2006_Mar_SMT

Traceability
System
Error-proof Your
The Industry’s Only Dedicated Surface Mount Technology ResourceThe Industry’s Only Dedicated Surface Mount Technology Resource
Jetting: Dispense
Technology of Choice
Lead-free: Matte
Finish Solder Joints
SMT 101:
Solder Materials
March 2006
www.smtmag.com
I N S I D E :
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Everyone has questions regarding pending deadlines
for compliance with the European Union’s new RoHS
lead-free directive. Fortunately, AMTECH has all the
answers, including a complete line of environmentally
friendly lead-free solder products. AMTECH offers:
• Solder paste
• Solder powder
• Core wire
AMTECH lead-free solder pastes are made from
world class AMT Unisphere™
powder for enhanced
solderability, which contains <200 ppm of lead,
guaranteed. AMTECH is also your exclusive source
for SynTECH-LF, a unique lead-free,
no-clean solder paste formula made
with proprietary synthetic poly-adduct
components. SynTECH-LF has been
proven to increase process line
yields with less beading, scrap
and rework.
For sensible answers to all your
lead-free questions, call the
experts at AMTECH.
It’s that easy.
AMTECHwww.amtechsolder.com
75 School Ground Rd., Branford, CT 06405 USA
(800) 435-0317 • (203) 481-0362 • Fax (203) 481-5033
We’ve
made
lead-
free
easy.
F I L L I N G T H E V O I D
For RoHS-compliant
solder products,
AMTECH has
all the answers.
• Solder spheres
• Solder preforms
• NVOC liquid flux
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Previous Page Contents Zoom In Zoom Out Front Cover Search IssueSMT
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Fast & Easy RoHS Compliance Screening
• Real-time nondestructive chemical analysis
• Quantiﬁes total Pb, Cd, Hg, Cr and Br in seconds
• Test solders, components, packaging and more
• Little to no sample prep required
• Handheld or benchtop operation via wireless PC interface
NITON Analyzers
Billerica, MA USA
800-875-1578
+1 978-670-7460
niton@thermo.com
Sales & Service Worldwide
www.thermo.com/niton
Analyze • Detect • Measure • Control™
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________________

EMS Trends
®
SMT
Surface Mount
Technology®
Magazine
content s
f e a t u r e s
COVER
STORY
www.smtmag.com March 2006/SMT 3
This month
on the web
departments
5 How to Contact SMT
10 News
11 Calendar
37 SMT Industry
Directory
37 Advertiser Index
38 SMT Marketplace
columns
6 Speaking of SMT
Gail Flower
7 Surface Mount
Manufacturing
Robert Rowland
8 Surface Mount
Global Process
Design
Evelyn A. Baldwin
9 Surface Mount
Components
Craig Hunter
40 SMT Perspectives
Joe Belmonte
Check out IPC’s Book-to-Bill
Ratio for December 2005.
Keep up with the latest
industry happenings and
newest products on
SMT online.
Be sure to subscribe to our
HTML format e-newsletter,
delivered every other
Wednesday.
Find out about the newest
and hottest industry events
in the Conferences and
Events section.
12 Traceability Data Integrity — Challenges and Solutions
The electronics manufacturing industry is seeing increased demands for material
traceability. Traceability requirements once limited to high-reliability applications
are becoming a necessity in other sectors. OEMs feel it is pointless to request
traceability without checks and balances in place to ensure accuracy. This is
motivating assemblers to error-proof traceability systems. By Mitch DeCaire
18 Jetting: Dispense Technology of Choice for Adhesives
Many manufacturers choose jetting technology to meet the demands of automated
adhesive application processes. As more manufacturers in a variety of industries
become aware of its advantages, jetting will become increasingly popular as the
dispense technology of choice for adhesives. By Al Lewis
20 Analyzing the Debate of Clean vs. No-clean
Most consumer-based products have adapted a true no-clean strategy, primarily
due to rapid technological changes within the market. This study illustrates that
products manufactured using a no-clean label are not a guarantee of long-term
reliability. By Umut Tosun, M.S.,Ch.E, and Harald Wack, Ph.D.
24 Identifying Stencils for Lead-free Solder Paste
July 1, 2006 marks the era of lead-free electronics in Europe. The influence of RoHS
and WEEE will result in better environmental quality, protection of human health,
and more rational use of natural resources. But the removal of lead from electronics
will bring massive changes for all companies in the supply chain. By Holly Wise
27 Matte-ﬁnish Solder Joints After Lead-free Wave Soldering
Most joints soldered using lead-free alloys exhibit a dull or frosty appearance, which
differs from the smooth, bright, shiny surfaces of tin/lead solders. This article looks
at several reasons for this phenomenon. By Gerjan Diepstraten
30 Due Diligence Veriﬁcation — Ensuring RoHS Compliance
RoHS compliance will require manufacturers to incorporate measures to ensure all
electronic components meet the EU’s directive. This article looks at the program
one EMS provider instituted to document this compliance.
By Scott Mazur and David Mercuro
Step-by-Step
32 Step 3: Solder Materials
Greater than 60% of end-of-line defects in SMT assembly can be traced to solder
paste and the printing process. Another 15% occur during reflow. Using designed
experiments and the measurement of critical solder paste-related process metrics, a
solder paste evaluation procedure was developed to maximize information about the
paste and its processability, while minimizing experimentation.
By Timothy Jensen and Ronald C. Lasky, Ph.D., PE
ON THE COVER
The article on page 12 emphasizes the need for material
traceability within many sectors of electronics manufacturing.
To see your company’s most
recent news on the Website,
e-mail Lee Mather, assistant
editor, at leem@pennwell.com,
or call her at (603) 891-9176. Cover image courtesy of Cogiscan.
M A R C H 2 0 0 6
V O L U M E 2 0
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alpha®
EF-6100
Introducing ALPHA®
EF-6100. The high-reliability, low-solids,
alcohol-based, no clean wave soldering flux that meets the
challenges of lead-free and tin-lead processing.
When you convert to lead free, you want the excellent board cosmetics
and minimal flux residues associated with low-solids fluxes. But you cannot
sacrifice high electrical reliability for solderability. With ALPHA®
EF-6100,
the next generation wave soldering flux you get it all:
• Superior residue cosmetics
• Best-in-class electrical reliability, passing IPC, Bellcore, and JIS surface
insulation resistance (SIR) and Bellcore and JIS Electromigration (EM)
• Excellent soldering performance in lead-free and tin-lead processes.
ALPHA®
EF-6100 will help you transition to lead-free seamlessly and cost-
effectively. Let’s face it, the world is changing. At Cookson Electronics, we
believe change shouldn’t come at the expense of performance.
GO TO www.newalphaproducts.com
for more information
Or, contact your Cookson Electronics representative.
Worldwide Headquarters • 600 Route 440 • Jersey City, NJ 07304 • USA • +1-800-367-5460 • www.alphametals.com
European Headquarters • Forsyth Road • Sheerwater • Woking GU215RZ • United Kingdom • +44-1483-758-400
Asia-Pacific Headquarters • 1/F, Block A • 21 Tung Yuen Street • Yau Tong Bay • Kowloon, Hong Kong • +852-3190-3100
Are you sacrificing
electrical reliability
for low flux residue and
good board cosmetics?
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www.smtmag.com
E D I T O R I A L
O F F I C E S
S A L E S O F F I C E S
W O R L D W I D E
SMT
®
(Surface Mount Technology) is published by PennWell Corporation © 2006 PennWell Corporation. Authorization to photocopy items for
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March 2006, Volume 20, Number 3 • SMT© (Surface Mount Technology©) (ISSN 1529 8930) is published 12 times a year, monthly,
by PennWell Corporation, 1421 South Sheridan Road, Tulsa, OK 74112, telephone (918) 835-3161; fax (918) 831-9497; web address
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America. GST NO. 126813153. Publication Mail Agreement No. 40052420.
Cookson Electronics
Lead-Free Wave
Soldering
Technologies
alpha
Our wave soldering products are
part of the world’s most complete
line of lead-free solutions. Their
proven compatibility helps you
transition to lead-free processes
seamlessly.
• ALPHA Vaculoy SACX0307 –
Wave Solder Alloy, high yield, fast
throughput, economy, reliability
• ALPHA Telecore Plus Cored Wire
– complete lead-free compatibility,
activated rosin, halide-free flux
core, non-corrosive residues
• ALPHA EF-Series Flux – lead-free
compatible, excellent hole-fill,
minimal bridging, best-in-class
solderball resistance
GO TO
www.newalphaproducts.com
for more information
Or, contact your Cookson
Electronics representative.
Americas + 1-800-367-5460
Europe + 44-1483-758-400
Asia + 852-3190-3100
www.cooksonelectronics.com
GROUP PUBLISHER: Jay Regan,
(603) 891-9126; E-mail: JRegan@pennwell.com
EDITORIAL
EDITOR-IN-CHIEF: Gail Flower,
(603) 891-9395; E-mail: gailf@pennwell.com
MANAGING EDITOR: Michelle M. Boisvert,
(603) 891-9310; E-mail: mboisvert@pennwell.com
ASSISTANT EDITOR: Lee Mather,
(603) 891-9176; E-mail: leem@pennwell.com
CONTRIBUTING EDITOR: Julia Goldstein, Ph.D.,
E-mail: julia.goldstein@sbcglobal.net
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SUBSCRIPTION SERVICES:
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EDITORIAL OFFICE
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ADVANCED TECHNOLOGY DIVISION
SENIOR VP ELECTRONICS AND
IT GROUP: Mark Finkelstein
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CORPORATE OFFICERS
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U.S. ADVERTISING & ONLINE
ADVERTISING SALES
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CLASSIFIED, DIRECTORY &
MARKETPLACE ADVERTISING SALES
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E-mail: tomc@pennwell.com
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G A I L F L O W E R
Speaking of
SMT
Editorial
Advisory
Board
Board Design
and Assembly
Vern Solberg
Tessera Technologies Inc.
San Jose, California
Business Management
Gary Tanel
TechBiz Consulting
Dallas, Texas
Cleaning
Michael Konrad
Aqueous Technologies
Corporation
Rancho Cucamonga,
California
Components
Craig Hunter
AVX Corp.
Myrtle Beach, South Carolina
Design and
Manufacturing
Ray P. Prasad
Ray P. Prasad
Consultancy Group
Portland, Oregon
Electronic Packaging
and Assembly
Dennis Derﬁny
Motorola Inc.
Schaumburg, Illinois
Fine-Pitch
Robert Rowland
RadiSys Corp.
Hillsboro, Oregon
Global Process Design
Evelyn Baldwin
3M EMMD
N. Andover, Massachusetts
Materials Science
Jennie S. Hwang
H-Technologies Inc.
Cleveland, Ohio
Process Optimization
Ron Lasky
Indium Corp. of America
Medway, Massachusetts
Surface Mount Assembly
Kim Hyland
Solectron Corporation
Milpitas, California
H
ave you noticed that many
of the associations and
trade shows seem to be
comprised of the same
people who have been
in the industry for quite a while?
Everyone seems to have known one
another for a period of time. Con-
ferences deliver the same message
to the same audience. You begin
to question if engineers are still
excited about careers in our field, if
universities are graduating as many
engineers as in the past, and if the
rewards are as promising as when
Jobs and Wozniak created Apple. I
remember when attendees at SMTA
meetings would pull me aside to talk
about their latest ideas for changing
the world. Are we still as motivated
as in the past? What message comes
from electronics in general to the
youth of the next generation?
I recently visited YESTech’s
president, Don Miller. He formed
this company after leaving a job
working for a major AOI/X-ray
firm, and decided to form his own
company in 2002. He and a partner
created the employee-owned com-
pany, and supply the industry with
the same tools using off-the-shelf
components integrated into lower-
cost, high-quality products for AOI
and X-ray. By not reinventing the
wheel, but instead using components
from existing suppliers, they were
able to build an affordable product
and a viable, healthy company.
Our next stop was Los Angeles-
based P. Kay Metal, where presi-
dent Larry Kay demonstrated
their chemistry for dross elimi-
nation: MS2 100 PB surfactant
for leaded solder pots and MS2
200 LF for lead-free wave solder
pots. The patent-pending chem-
istry came about when his firm,
offering solder paste (wire and
bar), flux, and dross-reclamation
services, developed the material
to help remove dross. When you
reduce the amount of dross pro-
duced in the wave soldering process,
profits go up and material is used
more efficiently.
We also visited Westlake Village,
Calif.-based Smart Sonic to talk to
company president Bill Schreiber.
This company has just formed
another firm, SMT Detergent
Corp., to distribute the 440-R SMT
Detergent. Though the company
developed the original ultrasonic
stencil-cleaning process in 1989, it
took a while to demonstrate that it
could clean all types of solder paste
at low-power densities. Proprietary
detergent and mechanical efficiency
of the ultrasonic cleansers helped the
company grow steadily.
Many inventions occur as a natu-
ral progression when people mature
in their field. Perhaps the best way to
encourage this entrepreneurial spirit
among youth is to support involve-
ment early. Invite a college student
to attend local association chapter
meetings. Support student scholar-
ships presented by SMTAI and other
organizations. Hire interns and sup-
port university-based research. The
vitality of electronics depends on it.
As my father often said, “Learning
is a lifelong endeavor that begins
early and never really ends.” SMT
“Perhaps the best way to encourage
this entrepreneurial spirit among
youth is to support involvement early.”
Gail Flower
Editor-in-Chief
Fostering the Entrepreneurial Spirit
6 SMT/March 2006 www.smtmag.com
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R O B E R T R O W L A N D
T
he transition to lead-free soldering
is a giant puzzle. Trying to assem-
ble it has been a massive under-
taking because there are so many
pieces. Like many of you, I have
been working on this puzzle for several
years. Fortunately, the pieces are start-
ing to fit together, and more is being com-
pleted. Our industry still has a lot to do, but
there is enough momentum at this point
that we should be able to comply with the
July 1, 2006, deadline. Following are six
frequently asked questions (FAQs) to help
solve part of the puzzle.
Does the lead in solder exemptions
include components?
What is covered under “Lead in solders
for servers, storage and storage array sys-
tems, network infrastructure equipment for
switching, signaling, and transmission, as
well as network management for telecommu-
nications?” The conservative interpretation
is that this includes lead in solder joints and
BGA solder balls only, and does not include
lead in lead frames (QFP, SOIC, etc.) and end-
terminations (capacitors, resistors, etc.).
EU Guidance Document interpretation: This
exemption was introduced to allow the use
of lead in solders for professional, high-reli-
ability applications such as servers and net-
work infrastruc-
ture equipment,
for which viable
lead-free alterna-
tives have not been
identified. It is the
department’s view
that this applies to
the whole of the computer and its compo-
nents, including processors, memory boards,
power converters, power supplies, enclosed
housings, modular power subsystems, and
adapter cards.
Can you stockpile product made before
July 1, 2006?
It depends on whether the product is ready
to be “put on the market.” This refers to
finished products, not individual parts or
subassemblies. When a product enters the
EU, it has not been “put on the market” if
it requires additional assembly. This takes
place when the product is made available for
the first time — when it is transferred from
manufacturing to distribution.
What lead-free solder alloy should I use?
SAC305 (Sn96.5Ag3.0Cu0.5) is emerg-
ing as the general-purpose lead-free alloy.
Lead-free solder-alloy evolution started
with iNEMI and their recommendation of
the SAC (SnAgCu) alloy Sn95.5Ag3.9Cu0.6
for reflow soldering and Sn99.3Cu0.7 for
wave soldering. The IPC Solder Prod-
ucts Value Council recommended the
Sn96.5Ag3.0Cu0.5 alloy based on “equiva-
lent performance and lowest material cost.”
SnCuNi alloys also have emerged as another
option for lead-free wave soldering.
Can I use my existing wave solder pot?
No, for two reasons. Lead contamination
is always a possibility, no matter how well a
solder pot is cleaned. Lead-free solder will
dissolve the natural protective coating on
stainless steel, which eventually will cause
corrosion of untreated stainless-steel wave
soldering hardware. Solutions to this include
cast-iron solder pots; ceramic-coated pots; or
nitride-coated, stainless-steel pots.
What surface ﬁnishes are acceptable?
The iNEMI Tin Whisker User Group pub-
lished “Recommendations on Lead-Free Fin-
ishes for Components Used in High-Reliabil-
ity Products.” It contains three surface finish
categories: Desirable finishes: NiPd, NiAu,
NiPdAu, matte Sn with Ni under plate, matte
Sn with Ag under plate, Sn reflowed, Sn hot-
dipped, SnAg hot-dipped, and SnAgCu
hot-dipped. Less desirable finishes: SnCu hot-
dipped; SnAg, 2−4% Ag; matte-Sn, 150°C
anneal; matte-SnCu, 150°C anneal; and SnBi,
2−4% Bi. Finishes to avoid: Matte Sn, SnCu,
bright Sn, Ag, and AgPd.
Tin whisker mitigation methods include:
• Non-Sn plating: noble metal alloys that
do not contain Sn;
• Under-layer plating: Ni or Ag layer
between Sn and base metal;
• Fusing-Sn plating: reflow process using a
hot-oil bath;
• Hot-dipped–Sn: Applied using a molten-
Sn bath;
• Annealed-matte–Sn: 150˚C for one hour;
• SnBi alloys: Bi content range 2−4% (do
not use with tin/lead solder);
• SnAg alloys: Ag content range 2−4%;
• Increase Sn thickness: minimum thickness
without under-layer plating of 10 µm; min-
imum thickness with under-layer plating
of 2 µm.
Other than surface ﬁnish, how are
lead-free PCBs affected?
Surface finish gets most of the attention, but
other issues are:
• Glass transition temperature (Tg
) is the
temperature at which polymer materials
transition from a rigid to soft state.
• Coefficient of Thermal Expansion
(CTE) is the amount of material expan-
sion that occurs above and below Tg
, usu-
ally expressed in ppm/˚C.
• Material decomposition temperature (Td
)
is the temperature at which the material
breaks down due to thermal exposure.
• Time to delamination (T260 and T288)
is the amount of time at a single tempera-
ture (260˚ or 288˚C) that the material can
withstand before delaminating. SMT
Robert Rowland is an SMT Editorial Advi-
sory Board member, instructor and co-au-
thor of Applied Surface Mount Assembly.
He currently is the process engineering
manager at RadiSys Corp. in Hillsboro, OR,
and technical conference director of SMTA
International. He also is an active member
of the SMTA and a recipient of the SMTA
Founder’s Award. Contact him at (503) 615-
1354; e-mail: rob.rowland@radisys.com.
The RoHS and Lead-free Puzzle
“The transition to
lead-free soldering
is a puzzle. Trying to
assemble it has been a
massive undertaking….”
Speaking of
Manufacturing
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E V E L Y N A . B A L D W I N
Speaking of
Global Process Design
T
his is the first in a series of articles
I will write related to global pro-
cess improvements. As our world
becomes increasingly more com-
plex and interconnected at the same
time, it becomes imperative to develop pro-
cesses that work across disciplines, geog-
raphies, and our customers’ companies. I
think we all would agree that the only rea-
son any of us are in business is because our
customers exist. Only by continuing to sat-
isfy them can we look forward to future
success and profitability.
I think we also would agree that as the
global business climate becomes more com-
plex and interconnected, it is increasingly
difficult to satisfy the customer, especially
when each has specific needs, challenges,
and competitive conditions. That is one of
the many reasons why I say, “Thank good-
ness for process improvement tools such as
six sigma and methods that help manage
our business in this global environment.” I
strongly believe that these tools can help
companies build value with customers. If
customers are why we are here, making
our operations work better is how we serve
those customers.
Internally, tools
such as these drive
improvementsacross
the broad spectrum
of business processes
and geographies.
This translates into
a significant competitive advantage, of
which we’ve seen proof time and again. If
you’ve been successful with business pro-
cess improvements internally, the next log-
ical step is to bring what you have learned
and apply it to your customers’ processes.
In the rush to launch process-improve-
ment efforts with customers however, it
is important to remain focused on some
important criteria.
Understand Customer Processes
and Problems
First, customer projects must be designed
to address customer pain-points and solve
problems generated by a customer pro-
cess. This should be done using customer-
defined metric. For example, a project dis-
guised as “for the customer” that is actually
intended to accelerate payment to your
own company isn’t a customer project. In
fact, the outcome of a project that is truly
“for the customer” may actually reduce
some of your business with them in a cer-
tain area. When customers see improve-
ments that you have helped achieve, their
loyalty will likely benefit your company in
other ways.
Identify Meaningful Projects
There are several areas to explore for
improvement efforts. While quality issues
come to mind first, others abound. Sup-
ply chain, product performance, manufac-
turing productivity, safety, and financial or
transactional issues are all fertile ground
for meaningful and productive customer-
improvement projects. It often helps to
have a common language for framing
issues. The process-improvement tools
that have become increasingly widespread
in recent years provide that common lan-
guage and framework.
Introduce Concepts Carefully
As you take these new methodologies to
your customers, most of them will not be
familiar or experienced with the tools. It is
important to ensure that they are properly
trained in the concepts. Only when your
customers have a strong comfort level with
the tools you are asking them to adopt can
they buy-in, become engaged, and embrace
the concepts and methodology fully.
Help Customers Own the Project
and Follow Through
Presented in the proper manner, the cus-
tomer likely will see benefits in undertak-
ing the project and will value its outcome.
Without someone owning the project on
the customer side though, it may be des-
tined for certain failure. Therefore, just as
with internal projects, it is crucial to have a
champion on the customer-side to promote
and carry the project through the organi-
zation. The higher that person is within
the customer’s organization, the better.
Finally, the customer must possess a set of
follow-up measures that will maintain the
process-improvement momentum for the
long-term. It must be their responsibility
to implement the improvements and consis-
tently do follow-ups to maintain the gains.
Conclusion
What do we know about the value of global
process improvement efforts for customers
thus far? Experience has shown two pri-
mary benefits: strengthened customer rela-
tionships and growth. It is logical that the
first would lead to the second. Satisfying
our customers is why we are here. SMT
Evelyn A. Baldwin is an SMT Advisory
Board member and sales manager for
3M Electronics. Evelyn has been an SMTA
member since 1988, and has 20 years of
experience in the electronics industry as
a material supplier. She also has served
one three-year term as vice president of
communications at the SMTA. She may
be contacted at (978) 886-9661; e-mail:
eabaldwin@mmm.com.
“I think we also would
agree that as the
global business climate
becomes more complex
and interconnected, it
is increasingly difﬁcult
to satisfy the customer.”
Four Ways to Help Customers
Improve Global Processes
iNEMI will host workshops on April 5, 2006,
in Munich, during SEMICON Europa, and
June 26–30, 2006, in Shanghai, China.
For information, contact Chuck Richardson
at chuck.richardson@inemi.org.
iNEMI International Workshops
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Speaking of
Components
C R A I G H U N T E R
The Impact of RoHS on Military
and Aerospace Applications
his year it happens. By July 1, 2006,
all electrical and electronic items
(as defined by RoHS) available in
Europe will be required to comply
withlow-ppmlevelsforsixrestricted
substances. The major impact is the limit of
1,000 ppm applied to lead content, as this
requires a wholesale change to electronic
PCB soldering processes and materials.
Major OEMs worldwide have managed
this change surprisingly well. There still
are challenges for manufacturers of mission-
critical products arising from two trends
of lead-free production. First, commer-
cial assemblies need to transition to lead-
free. Second, the reflow medium will typi-
cally be based on SnAgCu (SAC); therefore,
components must be compatible with this
material and must retain reverse-compat-
ibility with tin/lead systems that have not
yet converted. The ideal, low-cost termina-
tion material for passive components meet-
ing the above requirements is matte-tin.
While SAC systems provided acceptable
performanceformanyyearsthrougharange
of applications, they have not yet established
the years of history for stress and creep that
traditional tin/lead systems have. Another
issue is that tin-plated components, whether
reflowed in SAC or tin/lead, will have small
areas of exposed tin that can cause concern
about whiskers.
As studies con-
tinue, many avionic
end products will
be able to claim an
exemption until at
least 2010 for the
conversion process.
How and where the exemptions are applied
will form a key part of manufacturers’ sourc-
ingstrategies—andallofthisisbeingdriven
at the component level. Let’s consider two
aerospace manufacturers:
• Aerospace Manufacturer “A” has adopted a
green, lead-free policy to maximize usage
of commercial off-the-shelf (COTS) prod-
ucts with no diminishing material supply
(DMS) concerns.
• Aerospace Manufacturer “B” will retain
usage of MIL components with tin/lead
terminations.
Manufacturer “A” has an in-house PCB
assembly, external contract electronic
manufacturer (CEM) programs, and uses
COTS system-level solutions (power sup-
plies, VMEs, and displays). Manufacturer
“B” does as well. Manufacturer “A” has some
joint programs in which it acts as the con-
tract electronic manufacturer (CEM) for
Manufacturer “B”, and others where it is
an integrator of manufacturer “B’s” systems,
and vice versa.
Clearly, there is no one-size-fits-all solu-
tion, especially as joint programs run the
gamut from commercial avionic programs
to satellites. All solutions will need to be
program-specific. Depending on end-cus-
tomer requirements, a given program may
not be able to use matte-tin-plated com-
ponents. This will not be an issue for MIL
products, which retain tin/lead termination
specifications. However, for COTS parts,
alternatives such as tin/lead, gold, or pal-
ladium silver may be necessary. If the pro-
gram has elected to use COTS components,
it should be noted that recent technologies
have incorporated matte-tin termination
since its inception, and a special terminated
version may be needed from the supplier. If
the program is mission-critical enough to
require tin/lead-terminated parts, it may
be worthwhile to source an established reli-
ability version of the same part.
This is happening now, with suppliers
offering established reliable versions of
new technologies, and generating new MIL
specification sheets for extended range
and low-ESR tantalum chips, for exam-
ple. It will now be key for the design engi-
neer using COTS parts in mission-critical
applications to specify the termination fin-
ish for the component. There will need to
be some changes in terminology too. One
example is the case of tinning the leads of
a thru-hole component.
Traditionally, tinning would mean dip-
ping in tin/lead solder. Now, with the
commercial part likely to have 100% tin-
plated leads, the term itself will cause con-
fusion, requiring exact definition of the
solder composition into which a part is
dipped. To avoid confusion from such
semantics, for thru-hole parts it is best
to source the exact lead finish required
directly from the supplier. For surface
mount passives, it is much more impor-
tant — not just a case of semantics, but
one of reliability. Dipping a surface mount
passive in a tin/lead bath to cover a tin fin-
ish can lead to reliability issues and will
negate any suppliers’ part warranties.
For COTS subsystems (off-the-shelf
power supplies), the trend will be to have tin-
termination passives reflowed in either SAC
or tin/lead, depending on the manufacturer.
The combination of matte-tin termination
in tin/lead has been the staple of the industry
for a number of years. But mitigation studies
nowareperformedtoallayanyconcernswith
this option, and include supplier’s test results
onthepotentialforwhiskergenerationunder
certain environmental conditions, how close
the component is to an adjacent part or cas-
ing, what (if any) coating is used on the PCB,
and whether or not the device will be used
in a vacuum.
With regard to RoHS compliance, there
is one silver lining for users of COTS parts
in tin/lead reflow systems — passive tech-
nologies have raised the bar for thermal
resistance in that they can withstand mul-
tiple cycles of higher temperature reflows
required for SAC systems. Using these
parts in tin/lead systems will generate lower
stress, and can prove more forgiving in low-
volume/high-mix programs. SMT
Craig Hunter is an SMT Editorial Advisory
Board member and strategic marketing
manager of AVX Corp. in Myrtle Beach, SC.
Contact him at (843) 946-0601; Fax: (843)
626-5814; e-mail: hunterc@avxus.com.
“There are challenges for
manufacturers of
mission-critical products
arising from two trends
of lead-free production.”
T
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120
160
200
80
40
0
D
1.10
1.20
1.00
0.90
NOSAJ J F A
2004 2005
M A M JJ
Book-to-Bill ratio
(based on 3-month rolling average)
Booking index
Shipment index
O DNS
1.04
0.96
1.08
1.15
1.051.05
1.08
1.04
1.10
1.13
1.06
1.00
1.03
1.13
1.16 1.16
1.18
1.13
newsCompiled by SMT Staff
the inside line
Book-to-Bill Ends 2005 on Positive Note
BANNOCKBURN, Ill. — The IPC IMS/PCB book-to-bill ratio for December 2005
dipped slightly, but remained positive at 1.06. IPC reports the book-to-bill for
rigid PCBs was 1.09, while the North American flexible circuit book-to-bill ratio
dropped to 0.95. For these segments combined, sales billed (shipments) for Decem-
ber 2005 increased 13.8% year-over-year, and orders booked increased 20.4% from
December 2004.
December’s overall book-to-bill remained positive, and combined orders
booked for December 2005 increased 20.4% compared to this time last year.
PCB BOOK-TO-BILL RATIO
Get ready for nanotechnology to
move from the lab to the marketplace.
Though there is still too much hype
surrounding nanotechnology, a few
practical products from
sportswear, to sensors,
and even golf balls are
available now.
On January 17, 2006,
Buffalo, N.Y.-based
NanoDynamics Inc.
offered a sleeve of their
new golf balls engi-
neered with nanopar-
ticles to every golfer in
the annual SMTA Pan Pacific Golf
Outing at the Hapuna Golf Course
on the Big Island of Hawaii. On this
Arnold Palmer-designed course, 700'
above sea level, each shot had to be
precise just to keep the ball on the
fairway — rather than in surround-
ing lava rock. The wind whipped
every drive. Rain sprinkled down on
golfers at one point.
“Did the NDMX balls make a dif-
ference in my game?” asked the win-
ner, George Toskey of Midland, Mich-
igan-based Dow Corning Corporation.
“They did seem more controllable than
normal, holding the direction better.”
A nanometer, a billionth of a
meter, or approximately the size of
ten hydrogen atoms in a row, may
be a small amount of material, yet
new nano-based products can make
a big impact in future devices, such
as diagnostic machines, sensors, and
even golf balls. For instance, Nano-
dynamics has applied its expertise
in nanotech processing to reduce
the grain size of the metal alloys
used in the ball’s hollow metal core.
The benefit of reducing grain size
Nano Golf Balls Straighten Drives
from micron- to nano-scale is improved
impact strength. Reducing grain size
increases hardness and ductility is elim-
inated, which is key because ductil-
ity yields less-efficient
energy transfer, claims
the company. Aerodynam-
ically, the hollow metal
core is a sphere with its
mass carried further from
its center, creating a gyro-
scope effect. This lower
spin-rate results in the
ball flying straighter with
fewer tendencies for hooks and slices,
according to NanoDynamics engineers.
Why is small size so important? When
materials are reduced in scale, they often
behave differently. Nanoparticles are
forecasted to create efficient fuel cells,
fortified trims on fenders, tempera-
ture-adjusting sports clothing, and golf
balls that straighten drives, putts, and
approach shots. For more information on
the NDX golf balls from NanoDynam-
ics, Inc., visit www.nanodynamics.com or
www.ndmxgolf.com.
— Gail Flower
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news
Labeling System Veriﬁes
RoHS Compliance
NEWTOWN, Conn. — As part of its “Total
WEEE/RoHS Management Solutions
(TWRS)” service, TUV Rheinland of
North America has released a compliance
label for companies to certify products for
the RoHS Directive. The labeling aspect
is part of the company’s TWRS program,
a suite of WEEE and RoHS management
services that offer companies assistance
in the transition to RoHS compliance —
from training and education, to product
design and review, test reports, calculation
of recovery and recycling rates, and regis-
tration within each EU member state.
NPL Conference Sees
High Attendance
MIDDLESEX, UK — The National Physi-
cal Laboratory (NPL) conference, “Man-
ufacturing Reliable Lead-free Assemblies,”
which highlighted NPL’s lead-free solder-
ing research saw sold-out attendance num-
bers. Presentations were split into several
topics. “Lead-free Components” concen-
trated on three areas: tin whiskers, test-
ing for lead-containing terminations, and
solderability testing. Other presentations
included Lead-free Design, Printing with
Lead-free Pastes, Reflow Soldering of Lead-
free Solder Pastes, Lead-free Solder Joint
Inspection, and Alternatives to Lead-free Sol-
dering. A copy of papers presented at the
conference is available at http://www.npl.
co.uk/ei/clubs/051208sstc.html.
Valor Expands Latin
American Business Unit
FOOTHILL RANCH, Calif. — As part of a
global expansion strategy, Valor Comput-
erized Systems appointed Dante Domin-
guez as general manager for Latin America.
Dominguez will be responsible for build-
ing and maintaining relationships with
Valor’s customers across Latin America.
FlexLink AB Names CEO
GÖTEBORG, Sweden — FlexLink AB will
appoint Mattias Perjos to CEO follow-
ing Fred Jönsson’s departure in mid-April.
Jönsson will become CEO for the Craw-
ford Group, a division within Cardo AB.
ITW Acquires Tech Spray
GLENVIEW, Ill. and AMARILLO, Texas — Illi-
nois Tool Works (ITW) and Tech Spray
L.P. have signed an acquisition agree-
ment in which ITW acquired Tech Spray
L.P., a formulator and manufacturer of
quality aerosols and specialty products.
Tech Spray will remain an independent
company under the ITW Contamination
Control group. SMT
calendar
March
2006 Borderland Tradeshow
14-15
El Paso, Texas
Maquila/Manufacturing Solutions;
(915) 771-7061; e-mail: borderland@huntleigh.net;
Website: www.borderland.tradeshow.net
Military Technologies Conference
14-15
Boston, Mass.
PennWell Corp.; (603) 891-9267;
e-mail: lgowern@pennwell.com;
Website: www.miltechconference.com
SMTA Toronto/Advanced
Manufacturing Expo
29-30
Mississauga, ON, Canada
SMTA; (952) 920-7682;
e-mail: kristen@smta.org;
Website: www.smta.org
April
NEPCON China/EMT China 2006
4-7
Shanghai, China
Reed Exhibitions; (203) 840-5402, ext. 5313;
e-mail: zgrashow@reedexpo.com;
Website: www.nepconchina.com
Atlanta SMTA Expo
20
Duluth, Ga.
SMTA; (952) 920-7682; e-mail: leslee@smta.org;
Website: www.smta.org
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____________________
______________________________

THE ELECTRONICS MANUFACTURING INDUSTRY
IS SEEING INCREASED DEMANDS FOR MATERIAL
TRACEABILITY. TRACEABILITY REQUIREMENTS
ONCE LIMITED TO HIGH-RELIABILITY
APPLICATIONS ARE BECOMING A NECESSITY IN
OTHER SECTORS. OEMS FEEL IT IS POINTLESS TO
REQUEST TRACEABILITY WITHOUT CHECKS AND
BALANCES IN PLACE TO ENSURE ACCURACY. THIS
IS MOTIVATING ASSEMBLERS TO ERROR-PROOF
TRACEABILITY SYSTEMS. By Mitch DeCaire
Traceability
Data Integrity —
Challenges
and Solutions
By
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ERP
MRP
MES
T
he electronics manufacturing industry
is experiencing increased demands for
material traceability. Competitive pres-
sures for improving product quality while
reducing cost dictate a higher level of visi-
bility and control over the assembly process
and materials used. Traceability require-
ments once limited to high-reliability appli-
cations, such as automotive, aerospace, and
medical, are becoming a necessity in other
sectors, including data communications,
telecom, and high-end computing.
While demanding traceability from EMS
providers, OEMs are emphasizing data
integrity. They understand it is pointless
to request traceability if there are no checks
and balances to ensure complete data cap-
ture and accuracy. This is motivating assem-
blers to error-proof their traceability sys-
tems. Smart material-detection systems are
replacing manual scanning operations and
open-loop systems. Safeguards are being
incorporated to prevent production auto-
matically, unless the specified traceability
data has been recorded successfully. Some
factors driving these demands include:
Outsourcing. OEMs continue to increase
their reliance on the outsourcing model to
reduce costs and shift focus to core compe-
tencies. These OEMs are concerned with
maintaining and improving quality levels
because this has a direct influence on cus-
tomer satisfaction and future revenues. The
ability to identify the root cause of a field
failure, implement corrective actions, and
limit product recalls are considered criti-
cal to the success of the outsourcing model.
Contractual traceability requirements
assure an OEM that its suppliers will imple-
ment the control systems needed to gener-
ate and collect the necessary data.
Product recalls. OEMs are increasingly sen-
sitive to the expense of product recalls.
When a recall is required, cost and customer
impact can be minimized if data exists to
identify affected product serial numbers
precisely. Without such data, worst-case
assumptions must be made when determin-
ing which units to recall, resulting in the
wasteful and unnecessary removal of good
product from the field.
Liability. Manufacturing contracts with liabil-
ity stipulations emphasize the importance of
being able to prove that your products were
assembled according to proper customer
specifications and industry standards, using
the correct materials and chemicals.
Lead-free.Lead-freeconversionschedulesvary
from OEM to OEM, and by component sup-
plier.Somemanufacturerswillberequiredto
convert certain products to lead-free around
specific date codes. Others will be tasked
with managing two processes throughout a
transitional period, either lead-based or lead-
free, depending on where a particular prod-
uct serial number will be shipped and sold.
All of this presents the assembler with chal-
lenges. One constant is that lead-free legis-
lation drives the need to know which com-
ponents, boards, and solder (bar, paste, wire)
were incorporated into each work order or
product serial number.
Lean manufacturing. Lean initiatives focus
on the elimination of waste (muda), error-
proofing your operations (poka yoke), and
increasing material velocity throughout
the supply chain. While responding to
customer requirements for traceability, the
assembler will simultaneously uncover pro-
active opportunities to become lean:
• Online material detection systems can
validate that the correct materials and
tooling are at required line locations at
the right time. This eliminates the cre-
ation of scrap (pure muda) associated
with line setup errors.
• Material-tracking systems can provide vis-
ibility of the status and location of materi-
als on the shop floor (Figure 1). This elim-
inates wasted time searching for inventory,
while enabling precise material procure-
ment. You can buy materials confidently
based on actual requirements instead of
sourcing surplus inventory to compensate
for a lack of visibility of components on
the production floor.
Moisture-sensitive devices (MSDs). Sev-
eral current trends exacerbate the logisti-
cal nightmare of MSD control and related
risks of moisture-induced defects. Some of
these trends include increased sensitivity
levels due to higher reflow temperatures of
lead-free; continued reductions in package-
body thickness and lead pitch; increased use
of plastic over higher-cost, hermetic-body
materials; higher-mix production, resulting
in longer cumulative exposure time before
each tray or reel is consumed completely;
and transfer of manufacturing operations to
extremely humid geographic areas.
Amaterialtraceabilitysystemthataccounts
for MSD handling relative to the industry
standard, IPC/JEDEC J-STD-033B, helps
ensure MSDs will survive the reflow pro-
cess. The long-term risk of field failures due
to moisture-induced, internal-component
damage is reduced. The assembler also gains
data that can be used in liability situations
to prove that MSDs were managed prop-
erly during the assembly process. Such data
will indicate that the probable root cause of
a moisture-induced defect may be attributed
elsewhere in the supply stream.
Deﬁning Traceability Requirements
Although our industry agrees that material
traceability is becoming more important,
discrepancy remains as to what this term
implies. The definition depends on whom
you ask. Before selecting a traceability solu-
tion, it is critical to understand the depth,
scope, and granularity of your customer’s
data requirements.
The lowest level of material traceabil-
ity, frequently termed item traceability, sim-
ply keeps track of work in process (WIP) to
maintain time-stamped data on gross-prod-
uctmovementthroughoutsequentialprocess
steps. Item traceability is deployed in paral-
lel with route control to validate that each
process step occurred in the appropriate
sequence, at the correct workstation or sta-
tion type, while confirming that the product
passedalltestandinspectionpointsalongthe
way. Item traceability can be performed per
work order, but current trends are shifting
focus to individual product serial numbers.
Traceability applications necessitate an
additional link to the raw materials and tool-
ing used during assembly. This can include
a history of component lot codes present at
a workstation or machine when the product
was in it. With the emergence of lead-free,
there is an interest in recording raw materi-
als, such as solder paste, bar, and wire.
Figure 1. Real-time visibility of materials on shop floor.
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When tracking component lot codes, a
traceability system should account for the
product’s recipe (machine program or assem-
bly instructions) to screen-out online com-
ponents that aren’t used on a particular prod-
uct. This is especially helpful on assembly
lines or stations that incorporate a dedicated
setup. In such cases, the presence of a com-
ponent on the line does not necessarily indi-
cate its use on any particular product.
Within each level of material traceabil-
ity is plenty of room for different iterations.
When defining specific requirements, it is
important to ask the following questions:
• Do we need traceability of all compo-
nents, or just the more-expensive and
failure-prone components?
• Are we interested only in devices placed
using SMT machines?
• Should we log hand-placements and thru-
hole insertions?
• Should we trace lot-code data for other
raw materials such as solders, fluxes, and
cleaning agents?
• Should we know which operators were
involved at each stage of the assembly
process?
• Should our system maintain a log of other
process parameters, such as stencil serial
number, oven-zone temperatures, or the
tooling present at a manual workstation?
Full Data Capture and Accuracy
“Garbage in/garbage out” is a catchphrase
that can be applied to traceability systems.
A traceability solution is only as good as the
data that goes into it. For this reason, sources
of data loss and error should be eliminated
wherever possible. A common source of
data loss comes from the need to capture
each PCB serial number at strategic scan
points throughout the assembly process. In
such applications, the PCB serial number is
denoted typically by a barcode or 2-D data-
matrix symbol. The PCB S/N can be missed
due to quality issues associated with the cre-
ation and placement of the PCB identifier, or
if scanners along the line are not adjusted
properly during product changeover. The
risk of data loss is greater in higher-mix envi-
ronmentswithfrequentproductchangeovers,
and a variety of PCB form factors.
Product flow control can be implemented
to control the SMEMA handshake between
conveyors and machines at each PCB scan
point, and subsequently prevent a PCB from
transferring downstream, unless the prod-
uct serial number has been captured success-
fully (Figure 2). The mechanisms deployed
Figure 2. Product flow control assures data integrity and enforces route control.
TRACEABILITY DATA INTEGRITY — CHALLENGES AND SOLUTIONS
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________

RoHS is coming. Are you covered?
With Balazs, you are.
Beginning July 01, 2006, levels of
certain hazardous substances will be
restricted in consumer electronics.
Balazs analyzes parts, materials,
packaging and entire assemblies to
determine their compliance with
RoHS directives.
Balazs uses RoHS-approved proto-
cols with ultra-low detection limits for
all of the substances covered by the
restrictions, bringing strength to your
RoHS program. For more information,
call us at (510) 657-0600.
Balazs...trust that you are covered.
Certiﬁed ISO 17025 ISO 9001:2000
www.balazs.com
for product-flow control can also be used to
prevent further production when a system
detects a route-step error, a downstream line
setup discrepancy, or a product that failed a
prior test step and should not be allowed to
progress any further.
Another common error source stems
from scanning barcodes manually while
materials (components, stencils, solder paste,
etc.) are placed at specified locations along
the production line. Automated material-
detection technologies, commonly termed
smart technologies, can replace barcode
scanning and eliminate associated human
errors. One example, radio frequency iden-
tification (RFID), is an emerging material-
detection and tracking technology that is
garnering much attention.
Tape feeders for an SMT placement
machine represent a practical application
for RFID. The average PCB assembly fac-
tory has made a significant investment in a
large number of feeders for different types
of components and machines. RFID tags
can be attached to each feeder easily and eco-
nomically, regardless of feeder type or brand
name, to convert any standard feeder into a
smart feeder. RF antenna arrays can then be
installedwithinaplacementmachine’sfeeder
banks to detect and identify the feeder at
each slot automatically. The system subse-
quently prevents assembly defects by validat-
ing placement machine setup, and automati-
callycollectsaccuratetraceabilitydataduring
machine setup and replenishment (Figure 3).
In addition to improving data integrity, these
systems also improve line usage by eliminat-
ing the transactional overhead associated
with manual barcode-scanning operations
at the SMT line.
RF antenna arrays also can be retrofitted
within off-line changeover banks and feeder
storage racks, making it possible to track
feeders, including any reels of components
left on the feeders, throughout an entire fac-
tory (Figure 4). This leads to a more effi-
cient production operation. If you know the
real-time location of all feeders and reels on
your production floor, then no time is wasted
Figure 3. RFID tags
on feeders, and RF
antenna arrays on
feeder banks.
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RFID tag
Antenna arrays
Feeder
bank
searching for them. Because you no longer
have to compensate for a lack of visibility
of shop-floor inventory, it is not necessary
to purchase surplus components or release
more components than necessary from
stock. Using RFID technology to validate
setup and collect traceability data automat-
ically can be extended beyond the placement
machines to any other type of assembly sta-
tion. For example, RFID can be used to val-
idate that the correct stencil and solder paste
are present at a screen printer, or that the cor-
rect bin of components resides at a manual
assembly station. With these applications,
the goal is the same — eliminate ineffi-
ciencies and possible errors associated with
human transactions such as manual bar-
code-scanning operations.
It isn’t too late for electronics assemblers
who have invested in barcode-based MES
solutions for setup validation and traceabil-
ity. They can still benefit from RFID tech-
nology and automated product-flow control
without having to replace legacy systems.
This is because current and standards-
based software integration methodologies,
such as Web services, enable interoperabil-
ity between otherwise disparate systems.
RFID hardware and SMEMA-handshake
controllers can be integrated seamlessly
with an electronics assembler’s legacy soft-
ware system to exchange material-track-
ing event data. This type of integration
can be applied with internally developed
MES or shop-floor software systems, or
a commercial, third-party MES, as well
as software supplied by leading assembly-
equipment OEMs.
The most robust traceability systems
incorporate a combination of product-
flow control and automated material and
tooling detection at multiple assembly sta-
tions (Figure 5). This ensures all specifiedFigure 4. RFID smart feeders on equipment, off-line banks, and storage racks.
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Manage SMEMA interfaces to control product flow
and ensure 100% read rate of product serial number.
RF antenna arrays
within screen printer.
RFID tags on stencils,
paste cartridge, and tooling.
RF antenna arrays within
placement equipment.
RFID tags on feeders.
Machine/process
monitoring
Reflow ovenPick and placeChipshooterPrinter Manual work station
Figure 5. Robust traceability system.
materials are recorded and validated with
minimal human intervention before the
product is allowed to proceed to the next
assembly step or station.
Conclusion
To fulfill its intended purpose, a material
traceability system should ensure 100% data
capture and accuracy. This reinforces the
importance of automated data acquisition
to eliminate the risk of human error when
possible. A robust traceability system is one
that will also prevent production until all
required data has been captured, confirm-
ing that the correct materials are at the cor-
rect locations at each assembly step for the
product being assembled. When a customer
demands material traceability from the shop
floor, it is important to clearly understand
the specific requirements. When select-
ing a traceability system, it is critical to
choose a solution that is scalable and open in
architecture to ensure you can react to your
customers’ needs, no matter how simple or
complex — now and in the future. SMT
Mitch DeCaire, manager, Cogiscan, Inc.,
may be contacted at (450) 534-2644; e-mail:
mdecaire@cogiscan.com.
Cogiscan partners with
the following companies:
Equipment OEMs
AGS PTE LTD
www.ags.com.sg
Hover-Davis
www.hoverdavis.com
Juki Automation Systems
www.jas-smt.com
Integrator
SchmidtRFID
www.schmidtrfid.com
MES
Aegis Industrial Software Corp.
www.aiscorp.com
Conformal
Coating
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FIND OUT MORE ABOUT
CONFORMAL COATING
SYSTEMS FROM ASYMTEK:
Americas: 1-760-431-1919
Europe: +31-43-352-4466
Japan: +81-3-5762-2801
China: +86-21-5899-1879
Email: info@asymtek.com
www.asymtek.com
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Jetting: Dispense
Technology of Choice
for Adhesives
Many manufacturers
choose jetting technology
to meet the demands of
automated adhesive
application processes.
As more manufacturers
in a variety of industries
become aware of its
advantages, jetting will
become increasingly
popular as the dispense
technology of choice
for adhesives.
By Al Lewis
M
any manufacturers today choose
jetting technology to meet the
demands of their automated adhe-
sive application processes. Companies cur-
rently use jetting for corner-attach bond,
chip-stack packages (CSP), flip chip, no-flow,
andpre-appliedunderfillapplications,aswell
as conductive, surface mount, UV-cure adhe-
sives,andsilverepoxy.Becausejettechnology
represents a paradigm shift from needle dis-
pensing, it is becoming more popular as the
chosen dispense technology for adhesives.
Some reasons for this shift include:
• A jet dispenses material in smaller spaces
than a needle.
• Underfills have smaller fillets with jet-
ting for both BGA and flip-chip on-
board applications.
• Jetting is gentle on wire bonds and other
delicate assemblies.
• In contrast to jet printers, which are lim-
ited, automated jet dispensers can apply
specific fluids or viscosity ranges.
• The particular dispense characteristics of
adhesives and the range of adhesive appli-
cations makes jetting attractive for high-
volume production.
• Jetting is an enabling technology for
adhesive dispense on cutting-edge
designs.
• Jetting offers low cost of ownership
compared to other adhesive dispense
methods.
A Jetting Primer
Current dispense jetting technology uses a
mechanically, electrically, or pneumatically
actuated piston with a ball tip to impel fluid
through a narrow orifice at the end of the
jet nozzle (Figure 1). Air pressure raises the
piston, allowing fluid to flow around it into
the nozzle. When air pressure is removed, a
spring returns the piston so the ball again
sits in the nozzle orifice. As the ball re-seats,
it shoots a droplet of fluid out the end of the
nozzle. Adjusting the nozzle orifice, air and
fluid pressure control droplet size. Precise
heat control at the nozzle maintains fluid
temperature at an optimum viscosity for jet-
ting, and reduces variation in production.
Small dots propelled from the jetting
mechanism at rates up to 200 Hz in four soft-
ware-controlledmodes:distance-based,time-
based, fixed number of dots per line, and
continuous line with breaks, enable the con-
struction of many different sizes and shapes
of dots and lines. Because the momentum of
the fluid comes from the jetting action, prox-
imity to the substrate (dispense gap) is less
critical than needle dispensing.
A complete technical description of
jetting best illustrates its advantages over
other dispense technologies, but even this
brief introduction to the fundamentals of
jet dispensing reveals several advantages
over older adhesive dispensing methods.
Jetting is Versatile
Most adhesives that can be dispensed
using a needle can be applied with jetting
technology. An adhesive can be defined
as any material that bonds two previously
discrete items so the resulting bonded
assembly can operate within the range of
thermal and mechanical stresses that can
be expected within the product’s use.
Using this definition, many dispense
processes may be understood to be adhe-
sive applications. Some processes, such
as die attach and stacked die, are obvi-
ous. Others, such as underfill or lid seals,
may not be as obvious, but from the per-
spective of the dispense process, represent
adhesive applications.
The inherent simplicity of the jetting
mechanism enables it to adapt to a wider
variety of adhesive fluids, dispense patterns,
Figure 1. A pneumatic piston impels
fluid through a narrow orifice at the
end of the nozzle.
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and circuit board geographies than is pos-
sible with a needle dispenser. This simplic-
ity facilitates multiple adhesive application
processes using a single jetting dispenser.
Jetting is Faster for Adhesives
The most attractive feature of jetting with
regard to adhesives is increased speed.
The primary reason jetting is faster than
needle dispensing is the reduced amount
of mechanical travel required by the jet
mechanism.
The accumulated speed advantages of
jetting are summed up with the phrase
“jet on the fly.” Speed is the most obvi-
ous advantage of jetting adhesives, but the
elements of jetting that generate greater
speed also create other advantages.
Jetting is Non-contact Dispensing
To operate at high speeds, an automated nee-
dle dispenser often requires a standoff to pro-
vide dispense-gap feedback to the operating
system. This contributes several potential
negative outcomes:
1. Contacting the substrate with every dot
will abrade the tip of the standoff post.
This can cause process anomalies and
downtime for equipment maintenance.
2. The standoff post can track small
amounts of previously applied material
onto other parts of the substrate.
3. Because the standoff post sometimes
contacts previously applied material, it
must be cleaned. This adds complexity
to the mechanical and software compo-
nents of the dispense process.
4. Contact of the standoff post can damage
the board or substrate and knock com-
ponents off a PCB.
5. Under-board support typically is
required, adding cost and setup time.
Jetting eliminates these possibilities from
the process.
Applying Adhesives into Small Spaces
Several factors restrict the amount of
usable space available for a dispensing
needle. Rapidly decreasing component
size and shrinking real estate for place-
ment challenge the capability of needle
dispensers to apply adhesives quickly, ac-
curately, and effectively. These limits are
just as pronounced with screen-printing
technology. Some examples of applica-
tions where jetting technology’s ability
to apply adhesives into tight spaces are:
• SMT applications where it is neces-
sary to apply surface mount adhesives to
an assembly after solder paste has been
applied. Because of the jet nozzle’s ability
to fit into tight spaces, and because it can
build up a dot quickly by applying many
shots in the same location, surface mount
adhesive can be applied after solder paste
without disturbing the paste (Figure 2).
• 0402 component attach, where volumes of
10 nl and dots as small as ~13 mil are pos-
sible with jetting;
• Jetting through RF shields for BGA
underfill;
• Jetting in cavities for MEMS assembly;
• Jetting underfill on boards with tight
keep-out areas or to jet between closely
spaced die (currently as tight as 350 µm).
Jetting as an Enabling Technology
Some of the latest designs in electron-
ics packaging, medical devices, and tele-
communications equipment make jet-
ting an enabling technology — without
which the manufacturing of these prod-
ucts would be impossible or too expensive
to be marketable. Not only does jetting
enable the manufacture of these products,
it often can be accomplished using stan-
dard jetting equipment rather than cus-
tom-designed machines.
Typical applications in which jetting
can enable untenable designs include die
attach, assembling stacked die, produc-
ing cell phones that have an RF shield,
and installing UV gaskets for LCDs. The
speed improvement mentioned above can
be as great as 1.5–6× with jetting.
A more vital consideration in favor of jet-
ting adhesives for die attach, for example,
is the ability to create patterns not possible
with a needle dispenser. Another applica-
tion that demands the unique patterns avail-
able with jetting is dispensing 3-D lines of
silver epoxy onto MEMS sensors.
Jetting is Cost-effective
Several features of jetting technology lend
themselves to cost efficiencies not achiev-
able with other dispense methods. Jet dis-
pense can produce a smaller wetted path
than most pumps used for needle dispens-
ing. Therefore, less fluid is wasted. Fewer
machines are required with this technol-
ogy because one model can handle multi-
ple applications. Also, fewer moving parts
mean fewer breakdowns, lower mainte-
nance, less downtime, and fewer consum-
ables. Jetting’s ease of use requires less
operator training. Jetting is non-contact
dispensing, so it does not require under-
board support. Lastly, cleaning requires
minimal tools, and can be accomplished
in ten minutes or less.
Conclusion
Increasing demands of the global manufac-
turing market for speed, accuracy, ease of
use, and cost effectiveness in adhesive dis-
pensing makes jetting technology more
attractive than other dispense choices. In
response to the demand for enhanced vol-
umetric repeatability, one vendor* devel-
oped a feature that aims to improve pro-
cess capability (Cpk
). Dispense patterns are
programmed with a specified weight, the
system samples the dispense weight per shot
periodically, and then computes the num-
ber of shots for each pattern. This informa-
tion is used to optimize line-speed based on
maximum-specified shot intervals.
Jetting is used in the assembly and pack-
aging of cell phones, computer processors,
MEMS devices, hybrid circuits, and a vari-
ety of surface mount PCBs and flex circuits.
As designers become more familiar with the
capability of jetting, they will design parts
that can only be manufactured by use of
jetting technology. Those that don’t take
advantage of the technology lose an oppor-
tunity to improve their products. SMT
For a complete list of tables, please contact
the author.
*Calibrated Process Jetting (CPJ), Asymtek.
Al Lewis, director of application engineer-
ing, Asymtek, may be contacted at (760)
431-1919; e-mail: alewis@asymtek.com.
Figure 2. Jetting technology enables
surface mount adhesive to be applied
after solder paste without disturbing
the paste.
JETTING: DISPENSE TECHNOLOGY OF CHOICE
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After soldering After 4 weeks climatic changes
Inert resin
layer
Organic acid
Cracks
By Umut Tosun, M.S., Ch.E, and Harald Wack, Ph.D.
W
e all are experiencing new techno-
logical advances, on personal and
professional levels. Most consumer-
based products have adapted a true no-clean
strategy, primarily due to advancements.
No-clean products offer paste-specific
advantages that have found broad applica-
tion among high-end electronics industries
such as aerospace, avionics, and military and
defense. Within these markets, no-clean
pastes must be cleaned to eliminate any
impact of the low-residue nature, according
to J-STD-001, Class 3. The term “no-clean”
was chosen as a synonym for achieving iden-
tical product quality at lower overall process
cost by eliminating cleaning as an integrated
process step. Often, products manufactured
with a no-clean label are not a guarantee for
long-term reliable assemblies.
The missing link between in-field-failure
rates and climatic and leakage-current mea-
surements for electronic assemblies have yet
to be established. Actual weather conditions
are unfortunately not adequate to simulate
in-field conditions, and existing micro-cli-
mates at particular assembly locations are
influenced by site-specific factors. The doc-
umentation of micro-climatic conditions for
electronic assemblies has only recently been
possible due to newly developed sensor tech-
nologies. Consequently, there is a lack of
available information at this time. In the past,
such efforts have been seen in the automotive
sector, particularly in areas plagued by high
failure rates, such as electronic switches.
Studies on the long-term behavior of no-
clean encapsulations show that the integrity
of such films can be compromised (Figure 1).
This phenomenon depends on the quality of
encapsulation during the soldering step, as
well as the degree of actual in-field temper-
ature fluctuations (cycling). Some resin sys-
tems also become brittle through oxidation
reactions, and therefore guarantee protec-
tion for a limited period (Table 1).
HDI assemblies, particularly in motor
vehicles, are used more frequently. The
use of high-resistivity components accen-
tuates the sensitivity of these circuits to
environmental interferences. High-fre-
quency circuits between 30 MHz and 5
GHz are particularly affected. To maintain
signal integrity, these systems require not
only an adequate ohmic-insulation resis-
tance, but must also have stable, complex
impedance. Parasitic capacitances of con-
tamination can distort the ramp-up of the
signal, disrupting integrity and leading to
equipment malfunctions (Figure 2).
Proof of Cleanliness
Reductions in SIR and capacitive potential
that activator residues can build up can be
shown qualitatively under a scanning elec-
tron microscope (SEM). Imaging such
contamination is possible using a test that
responds selectively to carbon-acid-based
Most consumer-based products
have adapted a true no-clean
strategy, primarily due to rapid
technological changes within the
market. This study illustrates
that products manufactured
using a no-clean label are not a
guarantee of long-term reliability,
demonstrates the impact of this,
and highlights advantages of fully
integrated cleaning processes for
no-clean products.
Figure 1. Encapsulation of organic activators.
Analyzing the Debate of
Clean vs. No-clean
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Normal connection
High-frequency connection
Inductivity
Capacity
activators. Another direct measurement to determine resistiv-
ity values (i.e. of remaining no-clean residues) can be performed
through impedance spectroscopy. The surface resistance under-
neath chip resistors and capacitors can be determined to show the
improvements cleaning provides with respect to surface resistiv-
ity (Figure 3). For example, during studies, impedance was mea-
sured on identical components on five assemblies. These tests were
repeated after the cleaning process. Measurements matched, indi-
cating a high level of cleanliness across all assemblies.
This test, in conjunction with other reliability tests, allow assem-
blybehaviortobedeterminedunderappropriateclimaticconditions
to assess the overall benefits cleaning might have on products.
Post-soldering applications, such as the use of protective con-
formal coatings, should also be included in the clean vs. no-clean
manufacturing process discussion. During studies, delamination
and electrochemical migration were documented underneath
coatings up to 0.4" thick. Consideration must also be given to
increasing bleed from within assemblies and components. This
can limit the long-term adhesion of coatings and underfill materi-
als. Unfortunately, these critical precipitations are undefined, dif-
ficult to characterize or predict, and not monitored. Deteriorated
signal integrity will not be explainable or reproducible.
The no-clean process ideally should encapsulate all soils and
residues (or evaporate all critical compounds during soldering)
to render them ineffective against corrosion and leakage currents.
On the other hand, these hardened films can affect the ability
for IC testing (Figure 4). The defect rate of IC measurements
decreased significantly with a proper contact on residue-free sur-
faces. Furthermore, these films often lead to faulty measurements.
Contaminated test needles increased needle wear-and-tear, which
contribute adversely to overall process costs related to cleaning.
The presence of remaining no-clean flux residues also can
impact visibility, especially during the automated inspection
of soldered connections where various reflections and contrast
impairments are a concern. A lower defect rate (i.e. less rework)
is achieved with the use of clean processes.
Introducing a cleaning process for the removal of no-clean
flux residues adds to equipment and cleaning-agent costs. Such
expenses, can be justified when compared to various cost contrib-
utors of a no-clean process. For many electronic manufacturing
companies, the consumption of nitrogen (even for modern oven
systems) reflects one of the main consumable cost contributors
for no-clean processes. In light of lead-free, using nitrogen will
be less expendable with promoted oxidation due to higher sol-
dering temperatures.
Cost and reliability considerations aside, other benefits point
to an integrated and stable cleaning process. Soldering serves
Figure 2. Inﬂuence of high frequency on complex-resistance
boards. Flux activator residues can change the impedance of
connection surfaces and cause pad geometry enlargements.
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Frequency (Hz)
(Uncleaned)
Impedance(Ω)
Phase(°)
1 103 10030 1K300
100K
10K
1K
100
10
30K
0
-15
-30
-45
-60
-75
-90
3K
300
30
2wack 1-1
Measure
3wack 1-1
4wack 1-1
5wack 1-1
Frequency (Hz)
(Cleaned)
Impedance(Ω)
Phase(°)
1 103 10030 1K300
100K
10K
1K
100
10
30K
0
-15
-30
-45
-60
-75
-90
3K
300
30
wack Nr 2Be 1-2
Measure
wack Nr 3Be 1-2
wack Nr 4Be 1-2
wack Nr 5Be 1-2
Figure 3. Detection of contamination
by means of impedance spectroscopy.
ANALYZING THE DEBATE OF CLEAN VS. NO-CLEAN
to create soldered and reliable connections.
The addition of a cleaning-process step
introduces additional flexibility through
activated solder pastes and/or fluxes. This
results in an extended soldering process
window, i.e. shorter soldering profiles and
improved tolerances for process fluctua-
tions. Aside from appropriate soldering
conditions, cleanliness levels of assem-
blies must be considered as the second pri-
ority for no-clean processes. In compari-
son, methods with an integrated cleaning
process allow for more freedom. Here,
the functionality of each process step that
increases the output and reduce superflu-
ous rework steps is important.
For Class 3 products, the J-STD 001D
stipulates optical cleanliness (20–40×), as
well as a rosin content of <258 µg/in2
. Ionic
contamination values of <10.06 µg/in.2
, SIR
conformance, and other cleanliness stan-
dards are also required. With lead-free,
higher amounts of activators and rosins are
used, rendering the J-STD001D confor-
mance more difficult to achieve without a
fully integrated cleaning process. An over-
looked benefit of a clean process is the elim-
ination of any material specification with
regard to the actual (no-clean) remaining
TABLE 1
Summary of No-clean Risks
Full encapsulation ➞ Reﬂow process fully optimized.
Partial encapsulation ➞ Hygroscopic residues will absorb moisture.
Electrical cleanliness ➞ Leakage currents, corrosion, electrochemical migration,
and bit failures with RF assemblies (impedance-related).
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_____________________

contamination. By taking advantage of an integrated cleaning
process, companies profit from reduced costs and failure rates.
This process would result in overall improvement of adhesion of
conformal coatings and wire bondability.
Conclusion
With the onset of globalization movements, cost and logistical con-
siderations are becoming more prominent for domestic manufac-
turing companies to remain competitive. No-clean processes have
not only proven themselves effective, but will continue to play an
important role. With more experience and knowledge being gath-
ered, we are witnessing numerous high-quality assembly producers reverting to cleaning. The overall benefit of cleaning can realized
only by studying the positive effects on production costs, product
quality, and long-term climatic reliability. Cleaning also is becom-
ing a requirement due to the increased occurrence of high-fre-
quency technology and the introduction of lead-free solder pastes.
Due to the shortcomings of no-clean technologies, the debate of
clean vs. no-clean results in one conclusion — cleaning is neces-
sary for critical, highly valuable applications. SMT
For a complete list of references, please contact the authors.
Umut Tosun, M.S., Ch.E, application technology manager,
Zestron America, may be contacted at (888) 999-9116; e-mail:
u.tosun@zestronusa.com. Harald Wack, Ph.D. is the executive vice
president and CEO of Zestron.
Figure 4. Contaminated IC needles showing conventional
flux residues (left) and lead-free flux residues (right).
ACL Staticide
Elk Grove Village, Ill.
(847) 981-9212
www.aclstaticide.com
AGC Chemicals Americas, Inc.
Mission Viejo, Calif.
(949) 348-9608
www.agcchem.com
See Ad on page 16
Aqueous Technologies
Rancho Cucamonga, Calif.
(909) 944-7771
www.aqueoustech.com
Austin American Technology
Austin, Texas
(512) 335-6400
www.aat-corp.com
Cookson Electronics
Providence, R.I.
(203) 799-4904
www.cooksonelectronics.com
See Ad on pages 4–5
ITW Chemtronics
Kennesaw, Ga.
(770) 424-4888
www.chemtronics.com
See Ad on page 29
JNJ Industries, Inc.
Franklin, Mass.
(508) 553-0529
www.jnj-industries.com
Kester
Des Plaines, Ill.
(847) 297-1600
www.kester.com
Kyzen Corporation
Nashville, Tenn.
(615) 831-0888
www.kyzen.com
March Plasma Systems
Concord, Calif.
(925) 827-1240
www.marchplasma.com
MicroCare Corp.
New Britain, Conn.
(860) 827-0626
www.microcare.com
Nix of America
San Jose, Calif.
(408) 971-3115
www.nixofamerica.com
See Ad on page 23, 34
Petroferm Inc.
Fernandina Beach. Fla.
(904) 261-2400
www.pertroferm.com
Speedline Technologies
Franklin, Mass.
(508) 520-0083
www.speedlinetech.com
SmartSonic Stencil Cleaning
Systems
Canoga Park, Calif.
(818) 610-7900
www.smartsonic.com
SMT Detergent
Westlake Village, Calif.
(818) 707-3100
www.smtdetergent.com
TechSpray
Amarillo, Texas
(806) 372-8523
www.techspray.com
Zestron Corporation
Ashburn, Va.
(703) 589-1198
www.zestron.com
Cleaning Equipment and Materials
Here are just some additional resources related to this feature.
For more information, please contact each company directly.
ANALYZING THE DEBATE OF CLEAN VS. NO-CLEAN
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____________
_________

FPO
Solder spread inpact on process
High Sn-content alloys have higher
surface tension forces than
tin/lead alloys.
Lead-free alloys will not spread to
the edges of the pads as well as
tin/lead – potential for cosmetic
defect.
Requires more precise (accuracy
and repeatability) stencil aperture to
PCB pad alignment (process window
narrows).
•
•
•
63/37 alloy Lead-free
Post-reﬂowPre-reﬂow
Identifying Stencils for
Lead-free Solder Paste
July 1, 2006 marks the era of lead-free electronics in Europe. The influence of RoHS and
WEEE will result in better environmental quality, protection of human health, and more
rational use of natural resources. But the removal of lead from electronics will bring massive
changes for all companies in the supply chain.
B
eginning with the July 1, 2006 dead-
line, all suppliers must make changes
to ensure compliance with the lead-
free requirements of RoHS. On the surface
mount production line, both OEMs and
EMS providers are faced with several chal-
lenges with the emphasis on materials and
process traceability. The process includes
print accuracy and the alignment of the
stencil to the PCB. Material changes incor-
porate special tooling such as stencils. This
will require two stencils for the same pro-
duction run because the same stencil cannot
be used for both — the lead-bearing stencil
will contaminate the lead-free batch.
The lead-free printing process should
demonstrate a similar performance as the
lead-based paste printing process, i.e. sten-
cil life, print definition, and repeatabil-
ity — provided no density issues exist with
the paste. In general, no major changes to
the printing process should be required.
However, because tin/lead solder tends
to have better wetting than most lead-
free alloys, some stencil-design modifi-
cations may be needed to maximize paste
spread and counteract inferior wetting.
Depending on the materials and compo-
nents used, if wetting is not sufficient, sten-
cil design modifications may be needed.
For example, rather than producing sten-
cils with reductions of the aperture, we
may have to look at running the stencil 1:1
with the board. This is a trade-off because
going 1:1 with the board may result in more
defects during the assembly process. It
would be advisable to administer a test run
on a current stencil to confirm acceptable
spread and wetting.
Paste Characteristics
Due to paste-release characteristics and
lower wetting forces, the use of a material
other than standard stainless steel should be
evaluated for the lead-free stencil. Materi-
als with higher nickel content offer more
lubrication (less friction), improving paste
release. This material, which is currently
used to manufacture stencils for ultra-fine-
pitch or µBGA, offers better paste trans-
fer and volume.
Lack of spreading during the reflow
process requires a tighter process window,
Figure 1. 0603s and 0805s printed with lead-free solder paste before and after
reflow. There is a lack of spread during the reflow process. Photo courtesy of
Speedline Technologies.
By Holly Wise
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TEMS
®
A unit of ND Industries®
, Inc.
Low Pressure Injection Overmolding
Ruggedizing
Electronics
From
this
To
this
www.temsnd.com
• Low Pressure Injection Overmolding
• Potting • Sealing • EMI/RFI Shielding • Thermal Management
ND Industries, Inc. • 1000 North Crooks Road • Clawson, MI 48017 USA • Phone: 248-655-2506
• Los Angeles • Dallas • Chicago • Rockford • Detroit • Cleveland • Charlotte • New York • Orlando
• Kaohsiung, Taiwan • Kunshan City, China
®ND, ND Industries, ND Industries logo, and TEMS are registered trademarks of ND Industries, Inc.
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Dust Proof
Oil Proof
Shock Proof
Sleek &
Beautiful!
Water Proof
Dust Proof
Oil Proof
Shock Proof
Sleek &
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IDENTIFYING STENCILS FOR LEAD-FREE SOLDER PASTE
making the aperture position on the stencil and the placement
of the solder on the pad more critical. Tighter control of reg-
istration from stencil to board is mandatory to maximize pad
coverage, especially when placing components such as 0402. If
the positional accuracy of the stencil is off, it will compound
alignment issues (Figure 1).
Inspection and Accuracy
When using lead-free, it is more important that the positional
accuracy of the stencil be verified prior to use. This makes
proper inspection procedures a significant feature when deter-
mining a stencil supplier that will be a facilitator in the lead-free
transition. An automated optical inspection (AOI) system* can
be used to ensure positional accuracy and size over the entire
stencil. If any of the scanned apertures are misaligned with the
Gerber data due to an out-of-focus laser beam or non-calibrated
laser equipment, the operator is alerted with a percentage error,
and the misaligned apertures are highlighted. In the lead-free
environment, stencil manufacturers will require sophisticated
inspection systems such as AOI.
Another method to ease the transition to lead-free is to
make lead-free stencils distinguishable from lead-bearing
stencils to avoid contamination. In this example, the polyes-
ter border between the stainless-steel foil and the standard,
white, mesh frame signifies lead-bearing stencils. Lead-free
stencils are manufactured using a bright orange polyester
border, and the “Pb-free” symbol is etched onto the sten-
cil (Figure 2).
Conclusion
If lead-free isn’t on your agenda now, it soon will be. With all
involved parties ready and equipped to handle the conversion,
problems should be minimal. SMT
*LPKF ScanCheck AOI system, LPKF Laser and Electronics.
Holly Wise, technical accounts manager, MicroScreen, may be
contacted at (574) 232-4418; e-mail: hollyw@microscreen.org.
Figure 2. Lead-free (l) and lead-bearing (r) stencils show
distinguishing marks to help avoid contamination.
“Another method to ease the transition
to lead-free is to make lead-free stencils
distinguishable from lead-bearing stencils
to avoid contamination.”
Pb
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3
LEAD-FREESeries
ost joints soldered with lead-
free solders exhibit a dull or
frosty appearance. This differs
from the smooth, bright, shiny surfaces
experienced with tin/lead solders. This
is typical of SAC alloys (tin/silver/cop-
per) commonly used in lead-free solder-
ing applications. There are a number of
reasons for this occurrence. One reason
is that these lead-free alloys contain three
different elements, and thus three eutec-
tics, during solder solidification. These
eutectics each have their own melting
point and solidification behavior.
Formation of Different Eutectic Nuclei
Solder consists of an alloy that is a mix
of two or more metals. The melting and
solidification behavior will depend on the
formation of areas in the solder where dif-
ferent eutectics might solidify. This can
be the case when solder contains copper
and silver. In this case, CuSn- and AgSn-
eutectic parts or eutectic traces can form
next to the SnAgCu eutectic during solid-
ification of the solder in the joint.
Thedifferenteutecticsthatcanbeformed
in SAC alloys are Sn5Cu6 at 227°C, SnAg3
at 221°C, and Sn+SnAg3+Sn5Cu6at 217°C.
However, this is only true if the total pro-
cess contains only lead-free elements. In the
case of a tin-rich alloy, tin crystals can pre-
cipitateout ofthe alloy during cooling ofthe
joint at 232°C. If component leads are used
with a tin/lead plating, the lead dissolved
from the plating can also introduce eutec-
tic traces. This will lower the melting point
for some parts of the solder in the joint to
183°C for tin/lead eutectics, or to 178°C for
SnPbAg eutectics.
Solder Contraction or
Shrinkage While Solidifying
As the molten solder solidifies, it will shrink
by about 4%. Most of this volume reduc-
tion will be found in areas where the solder
solidifies last. These commonly are areas
where traces of the lowest melting eutec-
tic solder are found. If these traces are at
the joint-surface area, this mechanism can
create a dull appearance. This 4% volume
reduction often can be held responsible for
the formation of micro-cracks in the solder
joint. If the solder fillet moves during this
process due to pads lifting during soldering,
for example, and moves back during cool-
ing, these micro-cracks can develop larger
cracks due to volume reduction combined
with movement. These cracks will be found
only at the fillet surface of the solder joints.
The solder in between the copper barrel and
the lead generally will make a sound con-
nection that will strengthen the joint.
Movement of Soldered
Components or Solder While Pasty
The movement of soldered parts or solder
while not fully solidified or pasty can (at
worst) create cracks in solder joints, and (at
best)givethesolderjointamatteappearance
at the surface. The natural movement of the
solder pad during the formation of a solder
joint can cause this phenomenon. When
multiple joints are spaced together (as with
a connector), this solder-pad movement can
be considerable, and may cause fillet tearing,
fillet lifting, or pad tearing.
The differences in coefficients of thermal
expansion (CTE) between the copper bar-
rel that forms the plated thru-hole and the
epoxy-based material located between these
joints causes this pad movement. As a result,
the solder pad will be lifted in a wedge shape
from the edges of the copper barrel during
contact with the solder wave, and during the
filling of joints with liquid solder.
As soon as the soldered joint exits the
wave, it begins to solidify. Initially, dur-
ing this process more heat is transferred
to the epoxy/glass board material until
the solidification of thermal energy is
dissipated fully. Afterward, the board
cools and returns to its original dimen-
sions. During this time, the wedge-like
shape of the solder pad returns to a flat
configuration again. When this occurs,
the solder is not solidified completely
and exhibits a pasty characteristic. It
is this movement that can disturb the
joint surface during joint solidification
and can create cracks as a result of com-
bined shrinkage and fillet tearing. These
cracks are commonly positioned parallel
to the PCB surface. Occasionally, they
form a completely circular crack.
M
Matte-ﬁnish Solder
Joints after Lead-free
Wave Soldering
MOST JOINTS SOLDERED USING LEAD-FREE ALLOYS EXHIBIT A DULL OR
FROSTY APPEARANCE, WHICH DIFFERS FROM THE SMOOTH, BRIGHT,
SHINY SURFACES OF TIN/LEAD SOLDERS. THIS ARTICLE LOOKS AT SEVERAL
REASONS FOR THIS PHENOMENON.
By Gerjan Diepstraten
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Solder Joint Appearance
During solidification, the eutectic with the
lowest melting point often is surrounded by
already solidified particles — the eutectics
with higher melting points. This means that
during final solidification of the solder joint,
a soup of molten solder and already solidi-
fied particles with a different grain structure
is formed. During solidification, the solder
volume will shrink by about 4%. Most of this
volume reduction and contraction is found
on alloy parts in the joint that solidifies last.
This mix of liquid and solid solidifying at
different stages, each with a different surface
structure and combined with volume reduc-
tion, gives the joint a dull appearance.
Often, all of these mechanisms will act
concurrently, but not on every group of
joints at the same rate. This explains dif-
ferences in surface appearance after solder-
ing. Because the source of the dull solder
joint appearance lies in the combination
of the process and the alloy used, the out-
come should be judged as normal. This is
why the dull or matte appearance of such
solder joints should be regarded as an
effect, not a defect.
Effects of Forced Cooling
Forced cooling helps reduce the temperature
of the PCB at a faster rate, but has no real
effect on any of these mechanisms. It can
prevent further heat build-up in components
from the dissipated solidification heat com-
ing from the solder joint directly after sol-
dering — if cooling takes place at the com-
ponent side during this stage. Temperature
Explanation of Shrink
Structure Formation
If the solder alloy contains ele-
ments that can form more than
one eutectic alloy, different shrin-
kage patterns can be formed,
giving the solder joints a rough
appearance. Because factors such
as solder volume in the joint, the
heat-sinking effect of parts invol-
ved, alloy composition, and lead
plating can affect the cooling of
a soldered joint after leaving the
wave, solder solidification will
not be the same for all joints. This
means that joints can have a diffe-
rent appearance at the end of the
soldering process. Here’s why:
Assume that a given SAC sol-
der volume has the exact ternary-
eutecticcompositionSn3.5Ag0.9Cu.
This alloy will have a melting point
of 217°C. Under ideal conditions,
it has that melting point and no
other melting points from the
binary eutectics that could also
be present in this solder volume.
Therefore, this volume of solder
will solidify as one homogeneous
alloy that is in full equilibrium due
to its exact ternary-eutectic com-
position and equal temperature.
Normally, such an alloy will soli-
dify with a smooth surface under
these conditions because the sol-
der shrinkage will be divided over
the volume equally.
Next, assume that extra tin is
added to this perfect ternary sol-
der mixture deliberately. The extra
tin cannot be part of the ternary
eutectic because the alloy now con-
tains too much tin. This excess tin,
which has a melting point of 232°C,
MATTE-FINISH SOLDER JOINTS AFTER LEAD-FREE WAVE SOLDERING
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2006_Mar_SMT

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