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Reliability
li bili
C. Glenn Shirley
©2011 ASQ & Presentation Shirley
Presented live on Aug 02~04th, 2011
http://reliabilitycalendar.org/The_Re
liability_Calendar/Short_Courses/Sh
liability Calendar/Short Courses/Sh
ort_Courses.html
2. ASQ Reliability Division
ASQ Reliability Division
Short Course Series
Short Course Series
The ASQ Reliability Division is pleased to
present a regular series of short courses
featuring leading international practitioners,
academics, and consultants.
academics and consultants
The goal is to provide a forum for the basic and
The goal is to provide a forum for the basic and
continuing education of reliability
professionals.
http://reliabilitycalendar.org/The_Re
liability_Calendar/Short_Courses/Sh
liability Calendar/Short Courses/Sh
ort_Courses.html
3. Plastic Package Reliability
C. Glenn Shirley
Integrated Circuits Design and Test Laboratory
Electrical and Computer Engineering
Portland State University
Portland, Oregon
http://web.cecs.pdx.edu/~cgshirl/
© C. Glenn Shirley
4. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 2
© C. Glenn Shirley
5. Plastic-Encapsulated Microcircuits
• The course covers plastic-encapsulated microcircuits.
• Molding compound (MC) in PEMs comes in direct
contact with the die and chip connections.
Single Layer Copper Heat Slug
Lead Frame Tape/Adhesive
Dielectric
Expoxy Based Molding Metal Heat Sink Plate
Compound Ag - Epoxy Adhesive Ag - Epoxy Adhesive
BT Resin
Multilayer PCB
Epoxy Based Molding
1.27mm Grid Array Compound Solder Balls
Solder Balls
8/2-4/2011 Plastic Package Reliability 3
© C. Glenn Shirley
6. Plastic-Encapsulated Microcircuits
• Die is mounted on a lead frame (A42 or Cu).
• Bonds are made by. Alloy 42
Fe 58% Ni 42% alloy
– Wirebond: Au or Al; mostly Au. with CTE matching Si.
– TAB: Tape-Automated Bonding.
– C4: Controlled Collapse Chip Connect.
• Assembly is encapsulated in molding compound.
– Molding compound is in direct contact with die, wire
bonds, etc.
• External leads are trimmed and solder plated.
8/2-4/2011 Plastic Package Reliability 4
© C. Glenn Shirley
7. Molding Compounds
• MC is thermoset (curing) epoxy, typically novolac.
– Cures at ~ 170-180C.
– Silica “filler” controls CTE and increases thermal
conductivity.
– MCs are (now) free of ionic contaminants.
• Glass Transition ~ 140C.
• Moisture properties of MC:
– Permeable to moisture.
– Absorbs moisture. “Hygroscopic.”
Note distinction between thermoset and thermoplastic.
8/2-4/2011 Plastic Package Reliability 5
© C. Glenn Shirley
8. Molding Compound Properties
• At the glass transition (> 140 C)..
MC strength decreases CTE increases
L. T. Manzione “Plastic Packaging of Microelectronic Devices,” Van Nostrand Reinhold 1990.
8/2-4/2011 Plastic Package Reliability 6
© C. Glenn Shirley
9. Molding Compound Properties, ct’d
• Molding compound strongly absorbs water.
– Saturation uptake is proportional to RH, and independent
of temperature.
– Rate of uptake depends strongly on temperature.
L. T. Manzione “Plastic Packaging of Microelectronic
Devices,” Van Nostrand Reinhold 1990.
8/2-4/2011 Plastic Package Reliability 7
© C. Glenn Shirley
10. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 8
© C. Glenn Shirley
11. Life of an Integrated Circuit
OEM/ODM
Assembly Shipping Storage End-user Environment
Assembly
Temp
DT
Shipping Shock Temperature Bend Reflow Handling Temp, RH Power Cycle
Cycle Bent Pins, Singulation
Desktop
Temp
DT
BAM!
Shipping Shock Temperature Bend Reflow Handling Temp, RH User Drop Power Cycle
Cycle & Vibe
Mobile PC Bent Pins, Singulation
DT
BAM!
Shipping Shock Temperature Bend Reflow Handling Temp, RH Keypad
Cycle User Drop press
Handheld & Vibe
8/2-4/2011 Plastic Package Reliability 9
Source: Eric Shirley
© C. Glenn Monroe, 2003 Slide by Scott C. Johnson.
12. Stress/Test Flow
From: JEP150 “Stress-Test-Driven Qualification of and
Failure Mechanisms Associated with Assembled Solid
State Surface-Mount Components” (JEDEC)
Simulate shipping, storing, and
Preconditioning OEM board mounting process.
Simulate in-service end use
Environmental Stress conditions.
Electrical Test, Failure Determine pass/fail. Diagnose
Analysis failures.
8/2-4/2011 Plastic Package Reliability 10
© C. Glenn Shirley
13. Industry Reliability Standards
• International
– ISO International Standard Organization
– IEC International Electrotechnical Commission
• Europe
– CEN, CENELEC Comite Européen de Normalisation
Électrotechnique
• Japan
– JIS Japanese Industrial Standard, EIAJ
• US
– MIL (US Department of Defense), EIA/JEDEC
For US commercial products JEDEC standards have mostly superseded MIL standards.
8/2-4/2011 Plastic Package Reliability 11
© C. Glenn Shirley
14. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Preconditioning
• Preconditioning simulates board assembly.
• Specified by
– JESD22-A113F Preconditioning of Nonhermetic Surface
Mount Devices Prior to Reliability Testing.
– IPC/JEDEC J-STD-020D.01 Moisture/Reflow Sensitivity
Classification for Nonhermetic Solid State Surface Mount
Devices
http://www.jedec.org/
Free downloads, registration required.
8/2-4/2011 Plastic Package Reliability 12
© C. Glenn Shirley
16. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Environmental Test
• Stress-based testing (traditional). To keep things simple, we’ll
follow this approach.
– Standards: JESD47, MIL-STD-883.
– Pro:
• Well-established standards. Lots of historical data. Good for
comparisons.
• Little information about mechanism or use is required.
– Con:
• Overstress: May foreclose a technology.
• Understress: Misses a mechanism.
– May not accurately reflect a use environment.
• Knowledge-based testing.
– Risk assessment of Use and Mechanism guides test.
8/2-4/2011 Plastic Package Reliability 14
© C. Glenn Shirley
17. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Knowledge-Based Test
• Knowledge-Based Testing Use Condition Mechanism
– Stress depends on knowledge of
use conditions and mechanisms. Risk Assessment
– Risk assessment, using methods Stresses
• JEDEC: JESD94, JEP143, JEP148
• Sematech: “Understanding and Developing Knowledge-based
Qualifications of Silicon Devices” #04024492A-TR
– Pro:
• Stresses fit the product and its use. May make a product feasible.
– Con:
• Easy to miss mechanisms in new technologies and overlook use
conditions in new applications.
• Tempting to misapply to “uprate” devices, relax requirements.
8/2-4/2011 Plastic Package Reliability 15
© C. Glenn Shirley
19. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Example Stress Flow
Early life failure rate. Assumptions
ELFR 168 hrs 168 h is equivalent to early life requirement
JESD22-A108 SS computed from goal. eg. 3x611 = 1833
Focus of this course.
Preconditioning.
PC JESD22-A113
(Lots x Units)
3 x 77 3 x 25 3 x 25 3 x 25
HTOL HTSL (Bake) TC THB or HAST
High temperature 1000 hrs 700 cycles 1000 hrs (85/85)
operating life. JESD22-A103 3 cycles/hr JESD22-A101
168 -1000 hrs 233 hrs 96 hrs (130/85)
JESD22-A108 JESD22-A104 JESD22-A110
Condition B or G
(C is too severe)
8/2-4/2011 Plastic Package Reliability 17
© C. Glenn Shirley
20. Sampling
• JESD47 sample requirements are minimal.
– Single “snapshot” is a crude validation of the reliability of
the product.
– Small SS does not generate failures to give clues to process
weaknesses.
• Risks.
– Qualification hinges on single failures.
• Moral hazard to “invalidate” a failure is high.
– Lot-to-lot variation, excursions.
• Incoming materials, fab lots, assembly lots, test lots.
8/2-4/2011 Plastic Package Reliability 18
© C. Glenn Shirley
21. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Sampling, ct’d
• Number of lots covers risks of machine-to machine,
day-to-day, etc. variation.
• Often minimum SS to validate a goal is chosen.
– Pro: Saves $, and there are no failures to explain.
– Con: Pass/fail of the qual is at the mercy of a single failure.
• Verrry tempting to invalidate a failure.
– Con: No mechanism learning. (Accept/Reject 0/1)
• eg. To validate 500 DPM at ELFR using minimum SS at
60% confidence, 1833 units are required.
ln(1 cl )
– 500 DPM is a typical goal (see ITRS) SS
D
Useful “mental furniture” ln(1 0.6)
1833
500 106
8/2-4/2011 Plastic Package Reliability 19
© C. Glenn Shirley
22. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Sampling, ct’d
• For environmental stress, 77 is a typical SS, why?
ln(1 cl ) ln(1 0.9) ln(.1) 100 230.26
SS ; 2
76.7
D 3 10 3 3
– So, 0/1 accept/reject validates, to 90% confidence, a
failure rate less than 3% at the accelerated condition.
• If the stress corresponds to the lifetime (eg. 7 years)
then the average wearout failure rate is
3 102
FR 109 489 Fits
7 365 24
– This falls into the range of ITRS goals.
8/2-4/2011 Plastic Package Reliability 20
© C. Glenn Shirley
24. Example Data
• Additional attributes
enhance value of
data.
– Device type
– Date code
– Package type
– Readouts
– Failure analysis
Maxim product reliability report RR-1H
8/2-4/2011 Plastic Package Reliability 22
© C. Glenn Shirley
25. Preconditioning
Environmental Stress
Electrical Test, Failure
Analysis
Test and Failure Analyis
48 HOUR TEST WINDOW
• Moisture-related tests Functional Test
Fail (unvalidated failure)
Pass Return to Stress
(85/85, HAST, Steam) Validate Using Functional Test Pass
Invalid Failure
(Censor sample or
return to stress)
Fail
have specific test/FA Diagnostic Functional Test
Including raster scan, electrical analysis Pass
for electrical location of defect
reqt’s.
– Test must be done while All Other Failures
Fail by Invalid Mechanism
(eg. package defect
in die-related certification)
unit contains moisture.
• Within 48 hr. VALID FAILURE
– Units must not be “wet”. Bake + Diagnostic Functional Test
• Wet = liquid water. Fail
Irreversible Damage
(eg. corrosion)
Pass
Reversible
(eg. leakage path thu moisture films)
• Diagnostic Bake. Non-Destructive F/A
(visual, X-Ray, CSAM)
• Risk decision before
Risk Decision
(based on likely mechanism)
destructive analysis. Chemical Decapsulation
(to observe mechanical defects
such as cracks)
Mechanical Decapsulation
(to observe chemical defects
such as residues)
8/2-4/2011 Plastic Package Reliability 23
© C. Glenn Shirley
26. HAST versus 85/85
• Moisture MUST be non-condensing. (RH < 100%).
• Both require about < 1% fail. Typical SS ~ 100.
• 130/85 HAST duration is 10x less than 85/85
duration. We’ll see how this was justified.
• 85/85 (JESD22-A101) 6 week bottleneck in
information turns.
• HAST (JESD22-A110)
10x less time
33.3 14.2 1 atm = 14.2 psi
1.34 atmospheres Pressure vessel required.
14.2
8/2-4/2011 Plastic Package Reliability 24
© C. Glenn Shirley
27. Example: Comparison of HAST Stds
Intermittent Bias
Test and Failure Analysis Window
From Sony Quality and Reliability Handbook http://www.sony.net/Products/SC-HP/tec/catalog/qr.html
8/2-4/2011 Plastic Package Reliability 25
© C. Glenn Shirley
28. HAST System
• Large vessel (24” dia) requires forced convection.
C. G. Shirley, “A New Generation HAST System”, Non-proprietary Report to Intel, Despatch Industries, and Micro-
Instrument Corp. describing learnings during development of NG HAST. December, 1994.
8/2-4/2011 Plastic Package Reliability 26
© C. Glenn Shirley
32. HAST Ramp Up Requirements
• Ramp Up: Avoid condensation on load.
8/2-4/2011 Plastic Package Reliability 30
© C. Glenn Shirley
33. HAST Ramp-Down Requirements
• Mechanical pressure relief must be slow (3 h).
• Vent when pressure reaches 1 atm.
• Hold RH at test value.
– Units must retain moisture acquired during test.
~ 3.5 atm
1 atm
8/2-4/2011 Plastic Package Reliability 31
© C. Glenn Shirley
34. Vapor Pressure and Relative Humidity
Log scale 10
4 Coexistence of liquid and vapor
Q = 0.42 eV
2
1
.4
Pressure
(Atm) .2 Liquid Water
.1
Water Vapor
.04
.02
.01
200 160 120 100 80 60 40 20 0
Linear in 1/T (K),
Temperature in deg C (Arrhenius Scale) with ticks placed at
T (C).
8/2-4/2011 Plastic Package Reliability 32
© C. Glenn Shirley
35. Vapor Pressure and Relative Humidity
Actual water vapor pressure at temperature T
H
Saturated water vapor pressure at temperature T
or PH2O H Psat (T )
Important.
What is Psat?
lM QP klM
Psat (T ) P0 exp P0 exp QP 0.42 eV
RT kT R
Where
l = 2262.6 joule/gm (latent heat of vaporization)
M = 18.015 gm/mole, R = 8.32 joules/(mole K), k = 8.617x10-5 eV/K
This is a fair approximation. The main benefit is physical insight.
8/2-4/2011 Plastic Package Reliability 33
© C. Glenn Shirley
36. Vapor Pressure and Relative Humidity
An accurate formula for Psat (in Pascals) is
3
Psat (T ) 1000 exp an x , x
n 1
n 0 273 T ( C)
a0 16.033225, a1 35151386 103 ,
.
a2 2.9085058 105 , a3 5.0972361 106
which is accurate to better than 0.15% in the range 5 C< T < 240 C.
1 atm = 101325 pascals
This is an accurate formula.
8/2-4/2011 Plastic Package Reliability 34
© C. Glenn Shirley
37. Vapor Pressure and Relative Humidity
• Relative humidity at “hot” die in steady state.
– Partial pressure of water vapor is the same everywhere:
PH2O (die) PH2O (ambient )
– So RH at die is given by:
H(die) Psat (Tambient DTja ) H(ambient ) Psat (Tambient )
– Where the ratio, h is defined as:
H(die) h H(ambient )
Psat (Tambient )
h
Psat (Tambient DTja )
8/2-4/2011 Plastic Package Reliability 35
© C. Glenn Shirley
38. Vapor Pressure and Relative Humidity
1.00 0
2
0.80 4
0.784
6
0.60 8
R 10
0.40 15
20
30
0.20
40
Curves labelled with Tja
0.00
0 20 40 60 80 100 120 140 160 180 200
T(ambient)
Example: At 20/85 and Tja = 4 C, the die is at 24/(0.784x85) = 24/67.
8/2-4/2011 Plastic Package Reliability 36
© C. Glenn Shirley
39. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 37
© C. Glenn Shirley
40. Focus Topic: Acceleration
• Acceleration between two stresses is the ratio of
times (or cycles) to achieve the same effect.
• The “same effect” could be the same fraction failing.
– eg. The ratio of median (not mean!) times to failure in
different stresses is the Acceleration Factor (AF).
• AF is proportional to 1/MTTF
MTTF1 Q
1 1
AF (2 |1) exp Thermal
MTTF2 kB
T1 T2
Q
1 1
exp C V2 V1
MTTF1
AF (2 |1) exp Thermal and Voltage
MTTF2 kB
T1 T2
Q 1 1
m
MTTF1 a bV2 RH 2
AF (2 |1) exp Moisture ("Peck")
MTTF2 a bV1 RH1 k B T1 T2
m
MCTF1 DT2
AF (2 |1) Thermal Cycle ("Coffin-Manson")
MCTF2 DT1
8/2-4/2011 Plastic Package Reliability 38
© C. Glenn Shirley
41. Thermal Mechanisms
Early life failure rate.
ELFR 168 hrs
JESD22-A108
Preconditioning.
PC JESD22-A113
HTOL HTSL (Bake) TC THB or HAST
High temperature 1000 hrs 700 cycles 1000 hrs (85/85)
operating life. JESD22-A103 3 cycles/hr JESD22-A101
168 -1000 hrs 233 hrs 96 hrs (130/85)
JESD22-A108 JESD22-A104 JESD22-A110
Condition B or G
(C is too severe)
8/2-4/2011 Plastic Package Reliability 39
© C. Glenn Shirley
42. Gold-Aluminum Bond Failure
• Gold and Aluminum interdiffuse.
– Intermetallic phases such as AuAl2 (“Purple Plague”) form.
– Imbalance in atomic flux causes Kirkendall voiding.
– Bromine flame retardant is a catalyst.
• Kirkendall voids lead to
– Bond weakening - detected by wire pull test.
– Resistance changes in bond - detected by Kelvin
measurement of bond resistance.
8/2-4/2011 Plastic Package Reliability 40
© C. Glenn Shirley
43. Thermal (Ordinary) Purple Plague
Cross-section of gold ball bond on aluminum pad
after 200 hours at 160C
8/2-4/2011 Plastic Package Reliability 41
© C. Glenn Shirley
44. Gold-Aluminum Bond Failure
Log scale 1E4 1 year (!)
(8760h)
1E3
100
Hours
10
1
Source: S. Ahmad, Intel
0.1
380 340 300 260 220 200 180 160
Linear in 1/T
Temperature (deg C, Arrhenius Scale) (K), with ticks
Arrhenius plot of time to 10% of wire pull failure. placed at T (C).
Activation energy (Q) = 1.17 eV.
8/2-4/2011 Plastic Package Reliability 42
© C. Glenn Shirley
45. Gold-Aluminum Bond Failure
• Kelvin resistance Log{ Resistance Change (milliohms)}
measurements. 1.4
• Resistance increase of 1.45
1.2 2.7
Au bonds to Al pads vs 0.8
bake time. 1.0
0.5
• Bake at 200 C.
0.8
• Various levels of Br
flame-retardant in 0.6
molding compound. Weight % Bromine
0.4
• Br catalyzes Au-Al
intermetallic growth. 0.2 Source: S. Ahmad, et al. “Effect of Bromine in
Molding Compounds on Gold-Aluminum Bonds,”
• Br flame retardants IEEE CHMT-9 p379 (1986)
are being phased out 0
20 40 60 80 100 120 140
today.
Bake Time, hours
8/2-4/2011 Plastic Package Reliability 43
© C. Glenn Shirley
46. Thermal Degradation of Lead Finish
• Only an issue for copper lead frames (not Alloy 42).
• Cu3Sn or Cu6Sn5 inter-metallic phases grow at the
interface between solder or tin plating.
• Activation energy (Q) for inter-metallic phase growth
is 0.74 eV.
• If inter-metallic phase grows to surface of solder or
tin plate, solder wetting will not occur.
• Main effect is to limit the number of dry-out bakes of
surface mount plastic components.
8/2-4/2011 Plastic Package Reliability 44
© C. Glenn Shirley
47. Thermal Degradation of Lead Finish
Solder Solder
Lead
Cu6Sn5 intermetallic
Copper Copper
Post-plating solder plate Post burn-in solder plate showing
copper-tin intermetallic
8/2-4/2011 Plastic Package Reliability 45
© C. Glenn Shirley
48. Thermal Degradation of Lead Finish
X-section of solder-plated lead X-section of solder-coated lead
8/2-4/2011 Plastic Package Reliability 46
© C. Glenn Shirley
49. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 47
© C. Glenn Shirley
50. Example Stress Flow
Early life failure rate.
ELFR 168 hrs
JESD22-A108
Preconditioning.
PC JESD22-A113
HTOL HTSL (Bake) TC THB or HAST
High temperature 1000 hrs 700 cycles 1000 hrs (85/85)
operating life. JESD22-A103 3 cycles/hr JESD22-A101
168 -1000 hrs 233 hrs 96 hrs (130/85)
JESD22-A108 JESD22-A104 JESD22-A110
Condition B or G
(C is too severe)
8/2-4/2011 Plastic Package Reliability 48
© C. Glenn Shirley
51. H2O Diffusion/Absorption in MC
MODEL Surface exposed to ambient.
Zero flux or "die" surface
2L
Surface exposed to ambient.
ACTUAL Plastic Molding Compound (MC)
L
A
8/2-4/2011 Plastic Package Reliability 49
© C. Glenn Shirley
52. H2O Diffusion/Absorption in MC
Diffusion Coefficient: Saturation Coefficient:
Q Q
D D0 exp d S S0 exp s
kT See slide 13. kT
D0 4.7 105 m 2 / sec Qd 0.50 eV S0 2.76 104 mole/m3 Pa Qs 0.40 eV
Source: Kitano, et al IRPS 1988
Henry’s Law:
Msat PS HPsat S
See slide 33.
H2O vapor pressure.
Key Observation: Saturated moisture content of molding compound
is nearly independent of temperature, and is proportional to RH.
(Qs Qp )
M sat HP0 S0 exp Qs Qp 0.02 eV
kT
Nearly zero!
8/2-4/2011 Plastic Package Reliability 50
© C. Glenn Shirley
53. H2O Diffusion/Absorption in MC
1.00
0.80
Total Weight Gain (M)
(C-Cinit)/(Ceq-Cinit)
or 0.60
(M-Minit)/(Meq-Minit)
0.40
Concentration at Die Surface (C)
0.20
0.8481
0.00
0.00 0.20 0.40 0.60 0.80 1.00
Fourier Number = Dt/L^2
8/2-4/2011 Plastic Package Reliability 51
© C. Glenn Shirley
54. Response to Step-Function Stress
Typical Use Saturation Times
Hours
1K
DIP, PLCC (50 mils) Package Moisture
400
Time Constant
200 (time to 90% saturation)
100 PQFP (37 mils)
t (sat )
20
L2 Qd
10 TSOP (12 mils) 0.8481 exp
D0 kTmc
4
2 L
1
220 180 140 100 60 40 20
130 T (deg C)
Typical 130/85 HAST Saturation
Times Normal Operating Range
8/2-4/2011 Plastic Package Reliability 52
© C. Glenn Shirley
55. Cyclical Stress
One-Dimensional Diffusion Equation Solutions
8 hours on, 16 hours off cycling for PDIP Cj
Moles/m3 Moles/m3
520
540 0 440 0
460 360
380 mils mils
280
0 0 20 40 50
20 40 50
Hours 60 Hours 60
T(ambient) = 100 C T(ambient) = 60 C
t(sat) = 28 hours t(sat) = 153 hours
Moisture concentration at the die is constant if Period << t(sat)
8/2-4/2011 Plastic Package Reliability 53
© C. Glenn Shirley
56. Peck’s Acceleration Model
• Fundamental environmental parameters are T, H and
V, at the site of the failure mechanism.
– If the die is the site, this is denoted by “j”.
• A frequently used acceleration model is due to Peck
AF (a b V ) H m exp( Q / kT j )
j
• Find a, b, m, Q from experiments with steady-state
stress and negligible power dissipation.
• Typically a is small or zero: Bias is required.
• Requires H > 0 for acceleration: Moisture is required.
8/2-4/2011 Plastic Package Reliability 54
© C. Glenn Shirley
57. Moisture: MM Tape Leakage
Leadframe
Power Plane Ground Plane
8/2-4/2011 Plastic Package Reliability 55
© C. Glenn Shirley
58. Moisture: MM Tape Leakage
MM Leakage vs 156/85 Biased HAST Time 156/85 HAST of MM Tape Candidates
1000 0.15
800 "A"
0.1
600
Leakage 1/MTTF
mA
400 (hrs)
0.05
200 "B"
50
0 10 20 30 40 0
Biased HAST Stress Time (HR) 1 2 3 4 5 6 7 8
Bias (Volts)
Experimental Tape Data:
Tape m Q eV Acceleration factor is proportional to bias.
“A” >12 0.74 AF
“B” 5 0.77
Source: C. Hong, Intel, 1991 Constant V H m exp(Q / kT )
8/2-4/2011 Plastic Package Reliability 56
© C. Glenn Shirley
59. Moisture: Internal Metal Migration
• TAB Inter-lead Leakage/Shorts
– Accelerated by voltage, temperature and humidity
– Seen as early as 20 hrs 156/85 HAST
– Highly dependent on materials & process
-
+
-
Copper dendrites after 40 hours of biased 156/85 HAST
8/2-4/2011 Plastic Package Reliability 57
© C. Glenn Shirley
60. Lead-Stabilizing Tape Leakage
• A vendor process excursion.
• Leakage observed after 336 hours of steam.
• Re-activated by 48 hours at 70C/100% RH
• No leakage seen between leads not crossed by tape
• Rapid decay for leads crossing end of tape
– Tape dries from exterior inwards
Tape provides mechanical stability
Die Lead Stabilizing Tape to long leads during wirebond.
8/2-4/2011 Plastic Package Reliability 58
© C. Glenn Shirley
61. Lead-Stabilizing Tape Leakage
1E-5 Pins Crossed by Tape
1E-6
1E-7
Leakage Pin 2-3
Current (A) 1E-8 Pin 3 -4
1E-9
1E-10
1E-12 Pins NOT crossed by tape
1E-13
10 100 1000
Recovery Time (Minutes) Source: S. Maston, Intel
8/2-4/2011 Plastic Package Reliability 59
© C. Glenn Shirley
62. Aluminum Bond Pad Corrosion
Fe++ AF
Lead Corrosion
Microgap
Ni++ Cl-
Constant V H m exp(Q / kT )
Source m Q (eV)
Peck (a) 2.66 0.79
Moisture
Moisture Hallberg&Peck (b) 3.0 0.9
(a) IRPS, 1986; (b) IRPS, 1991.
Pins
1 Shortest path has highest
failure rate.
Source: P.R. Engel, T. Corbett, and W. Baerg, “A
New Failure Mechanism of Bond Pad Corrosion in
Plastic-Encapsulated IC’s Under Temperature,
Humidity and Bias Stress” Proc. 33rd Electronic
Components Conference, 1983.
8/2-4/2011 Plastic Package Reliability 60
© C. Glenn Shirley
63. Passivation in Plastic Packages
• Passivation is the final layer on the die.
• Passivation has two main functions:
– Moisture Barrier
• Molding compound is not a moisture barrier.
• Silicon oxides are not good moisture barriers.
• PECVD silicon nitride or silicon oxynitride film is a good barrier.
• Film must be thick enough to avoid pinholes, coverage defects.
– Mechanical Protection
• Silicon nitride films are brittle.
• Polyimide compliant film protects silicon nitride.
• Polyimide can react with moisture (depending on formulation).
8/2-4/2011 Plastic Package Reliability 61
© C. Glenn Shirley
64. Polyimide/Au Bond Failure
• Bonds overlapping passivation don’t necessarily
violate design rules.
• But can activate polyimide-related “purple plague”
failure mechanisms in combination with moisture.
• Acceleration modeling showed no field jeopardy.
Polyimide
PECVD Oxynitride/Nitride Metal Bond Pad
Other films
Silicon
8/2-4/2011 Plastic Package Reliability 62
© C. Glenn Shirley
65. Wire Bond Pull Test
8/2-4/2011 Plastic Package Reliability 63
© C. Glenn Shirley
66. Moisture-Related Gold Bond Degrad’n
Effect of 80 hours of 156/85 HAST vs 156/0 Bake
and Centered vs Off-Centered Bonds on Wire Pull Test Data
99.99
99.9
99
90
70 HAST
50 OFF-CENTER
%30
10
HAST
CENTERED
1 BAKE
BAKE OFF-CENTER
0.1 CENTERED
0.01
0 2 4 6 8 10 12 14 16 18 20
Pull Force (gm)
Source: G. Shirley and M. Shell, IRPS, 1993
8/2-4/2011 Plastic Package Reliability 64
© C. Glenn Shirley
67. Moisture-Related Gold Bond Degrad’n
Wire Pull Strength of Polyimide vs No Polyimide and Centered
vs Off-Centered Bonds after 40 hours of 156/85 HAST
99.99
99.9
99
90
70
50
%30 POLYIMIDE
OFF-CENTER
10
1
NO-POLYIMIDE
0.1 POLYIMIDE CENTERED: SQUARE
CENTERED OFF-CENTER: TRIANGLE
0.01
0 2 4 6 8 10 12 14 16 18 20
Pull Force (gm)
Source: G. Shirley and M. Shell-DeGuzman, IRPS, 1993
8/2-4/2011 Plastic Package Reliability 65
© C. Glenn Shirley
68. Moisture-Related Purple Plague
Cross-section of gold ball bond on aluminum pad
after 80 hours at 156C/85%RH
8/2-4/2011 Plastic Package Reliability 66
© C. Glenn Shirley
69. Moisture-Related Gold Bond Degrad’n
121/100 17hr 156/85 + x 156/65 b 112.7 gm
135/85 156/85
100 a0 113 1010 (gm - hrs) -1
.
80 m 0.98; Q 115 eV
.
F50
1
(gm) F50
40
(at ) 2 1 / b 2
a a0 h m exp( Q / kT )
20 FP F50 exp( Z P )
20 40 100 200 400 1E3 2E3
Hours 0.17
Source: G. Shirley and M. Shell-DeGuzman, IRPS, 1993
8/2-4/2011 Plastic Package Reliability 67
© C. Glenn Shirley
70. Circuit Failure Due to Passiv’n Defects
10m
Site of failing bit. SRAM after HAST stress.
Courtesy M. Shew, Intel
8/2-4/2011 Plastic Package Reliability 68
© C. Glenn Shirley
71. Circuit Failure Due to Passiv’n Defects
2m
2m
Etch-decorated cross-section of passivation. Note growth seams.
8/2-4/2011 Plastic Package Reliability 69
© C. Glenn Shirley
72. Circuit Failure Due to Passiv’n Defects
SRAM VOLTAGE THRESHOLD MAP FOR CELL PULLUP TRANSISTOR
(Baseline threshold is 0.89 V. Passivation is 0.6 m nitride, no polyimide.)
Vthreshold Vthreshold
Row Row
Column Column
After 120 h 156/85. 4 2 bits recover after further 2 hr
failed bits with Vt > 2.5 V bake at 150 C
Source: C. Hong, Intel
8/2-4/2011 Plastic Package Reliability 70
© C. Glenn Shirley
73. Acceleration Model Fit of HAST Data
SRAM HAST and 85/85 Bit Failures (No Polyimide)
90
85/85, standby
70 140/85, standby
140/85, no bias
50 156/85, standby
% 156/85, active
30 156/85, no bias
Model: 85/85 standby
Model: 140/85 standby
10 Model: 140/85 no bias
Model: 156/85 standby
Model: 156/85 active
Model: 156/85 no bias
1
Notes:
0.5 • “Standby” = 5.5V bias, low power
30 100 1E3 1E4 • “Active” = 5.5V bias, high power
Hours
• 156/85: non-standard, limit of
AF Constant ( a bV ) H m exp( Q / kT ) pressure vessel.
• Source: C. G. Shirley, C. Hong. Intel
a 0.24 b 014 m 4.64 Q 0.79 eV
.
8/2-4/2011 Plastic Package Reliability 71
© C. Glenn Shirley
74. Peck Model Parameters
Hours of
Q/m < 130/85
Mechanism Q(eV) m Q/m 0.42eV? 1kh 85/85 Reference
MM Tape A 0.74 12 0.06 Yes 69 2
MM Tape B 0.77 5 0.15 Yes 62 2
Single Bit SRAM 0.79 4.6 0.17 Yes 57 3
Corrosion, THB (early Peck) 0.79 2.66 0.30 Yes 57 4
Corrosion, THB (later Peck) 0.90 3 0.30 Yes 39 5
Bond Shear 1.15 0.98 1.17 No 16 6
Yes/No: Increasing power dissipation at die, slows/accelerates the moisture mechanism.
1. Kitano, A. Nishimura, S. Kawai, K. Nishi, "Analysis of Package Cracking During Reflow Soldering Process," Proc.
26th Ann. Int'l Reliability Physics Symposium, pp90-95 (1988)
2. S. J. Huber, J. T. McCullen, C. G. Shirley. ECTC Package Rel. Course, May 1993. Package tape leakage
acceleration data courtesy C. Hong.
3. G. Shirley and C. Hong, "Optimal Acceleration of Cyclic THB Tests for Plastic-Packaged Devices," in Proc. 29th
Ann. Int'l Reliability Physics Symposium, pp12-21 (1991)
4. S. Peck, "Comprehensive Model for Humidity Testing Correlation," in Proc. 24th Ann. Int'l Reliability Physics
Symposium, pp44-50 (1986).
5. Hallberg and D. S. Peck, "Recent Humidity Accelerations, A Base for Testing Standards," Quality and Reliability
Engineering International, Vol. 7 pp169-180 (1991)
6. G. Shirley and M. Shell-DeGuzman, "Moisture-Induced Gold Ball Bond Degradation of Polyimide-Passivated
Devices in Plastic Packages," in 31st Ann. Int'l Reliability Physics Symposium, pp217-226 (1993).
8/2-4/2011 Plastic Package Reliability 72
© C. Glenn Shirley
75. HAST versus 85/85, ct’d
• For all mechanisms surveyed, 1000 hours of 85/85 is
equivalent to < 96 hr of 85/85.
• For packages < 10 mils covering die, moisture
saturation occurs within 10 h at 130/85.
• For Tj-Ta > 10C, most mechanisms (with Q/m < 0.42
eV) can be more accelerated with cyclical bias.
• 85/85
– JESD22-A101
• HAST
– JESD22-A110
8/2-4/2011 Plastic Package Reliability 73
© C. Glenn Shirley
76. Steady Power Dissipation
• Superimpose log(H) vs 1/T contour plots of
– Peck model for THB acceleration factor.
– Partial pressure of water vapor, Psat.
• Contours are straight lines:
– Peck model: Iso-acceleration contours with slope
proportional to Q/m.
– Psat: Isobars with slope proportional to Qp = 0.42 eV.
• Depends on: In steady state, the partial pressure of
H2O is the same in the ambient and at the die.
Reference: C. G. Shirley, “THB Reliability Models and Life Prediction for Intermittently-
Powered Non-Hermetic Components”, IRPS 1994
8/2-4/2011 Plastic Package Reliability 74
© C. Glenn Shirley
77. Steady Power Dissipation
Iso-acceleration contours for example mechanism
(m = 4.6, Q = 0.8 eV) superimposed on water vapor pressure isobars.
5 atm 4 3 2 1 atm 0.1 atm 0.01atm
100
100K 1K
X Typical Climate
RH (%)
at Die
Hj Increasing steady-state
(log scale) 100 dissipation (X to Y).
Follows isobar.
10
40 1 Relative slope
Y 0.01
Q/m < 0.42 eV: Deceleration
Q/m > 0.42 eV: Acceleration.
30
180 140 100 80 60 40 20 0
Tj at Die (deg C) (Arrhenius (1/TK) Scale, marked with TC)
8/2-4/2011 Plastic Package Reliability 75
© C. Glenn Shirley
78. Example: Comparison of HAST Stds
Non-steady-state requirements
From Sony Quality and Reliability Handbook http://www.sony.net/Products/SC-HP/tec/catalog/qr.html
8/2-4/2011 Plastic Package Reliability 76
© C. Glenn Shirley
79. Time-Varying Power Dissipation
• Most moisture-related mechanisms..
– Have slow or zero rates at zero bias (V=0). AF V H exp(Q / kT )
m
j j
– Have Q/m < 0.42 eV so, in steady-state, depressed die
humidity due to power dissipation slows the rate.
• There is an optimum duty cycle which maximizes the
effective acceleration.
8/2-4/2011 Plastic Package Reliability 77
© C. Glenn Shirley
80. JEDEC 85/85 and HAST Req’ts
• Tj-Ta 10C: 100% duty cycle. Assumptions:
• 85/85
• Tj-Ta > 10C, 50% duty cycle. • Peck Model m = 4.64, Q = 0.79 eV
• AF = 0 for V = 0.
• MC thickness 50 mils
• Kitano et. al MC properties.
Effective Effective
Acceleration Acceleration
Factor Factor
Tj – Ta = 20C
G. Shirley and C. Hong, "Optimal Acceleration of Cyclic THB Tests for Plastic-Packaged
Devices," in Proc. 29th Ann. Int'l Reliability Physics Symposium, pp12-21 (1991)
8/2-4/2011 Plastic Package Reliability 78
© C. Glenn Shirley
81. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 79
© C. Glenn Shirley
82. Thermomechanical Mechanisms
Early life failure rate.
ELFR 168 hrs
JESD22-A108
Preconditioning.
PC JESD22-A113
HTOL HTSL (Bake) TC THB or HAST
High temperature 1000 hrs 700 cycles 1000 hrs (85/85)
operating life. JESD22-A103 3 cycles/hr JESD22-A101
168 -1000 hrs 233 hrs 96 hrs (130/85)
JESD22-A108 JESD22-A104 JESD22-A110
Condition B or G
(C is too severe)
8/2-4/2011 Plastic Package Reliability 80
© C. Glenn Shirley
83. Key Material Properties
• Material properties which drive temperature cycling-
induced failure mechanisms.
Material Thermal Coeffic’t Young's Thermal
of Expansion Modulus Conductivity
(ppm/°C) “TCE” (GPa) (W/m °C)
Copper 17 119 398
Alloy 42 5 Match! 145 15 Low!
Silicon 3 131 157
Molding Compound 21 18 0.6
Alumina 6.5 25 25
PC Board 15-17 11 25
8/2-4/2011 Plastic Package Reliability 81
© C. Glenn Shirley
84. Cracking Due to Temperature Cycle
Bond and TFC damage
Void & cracks Crack
Shear
Stress With crack
Without crack
Zero
Normal
Die Edge
Stress
With crack
Zero
Without crack
8/2-4/2011 Plastic Package Reliability 82
© C. Glenn Shirley
85. Crack Propagation in Test Conditions
• Tensile Test of Notched Samples
– Measure crack growth rate for sinusoidal load:
Crack
Load a Load
Notch
– Sample geometry and load determine stress intensity
factor, K.
– Plot crack growth rate da/dN versus K on log-log plot to
determine Coffin-Manson exponent, m:
8/2-4/2011 Plastic Package Reliability 83
© C. Glenn Shirley
86. Crack Propagation in Test Conditions
1E-1
Encapsulant A
1E-2
Slope of lines on log-log plot
Crack Growth Rate
25C
da/dN 1E-3
Const DK
mm/cycle
da m
1E-4 150C
dN
-55C
m 20
1E-5
Source: A. Nishimura, et. al. “Life Estimation for IC
Packages Under Temperature Cycling Based on
Fracture Mechanics,” IEEE Trans. CHMT, Vol. 10,
1E-6 p637 (1987).
0.5 1 2 3
Stress Intensity Factor Amplitude
K (MPa m)
8/2-4/2011 Plastic Package Reliability 84
© C. Glenn Shirley
87. Crack Propagation in Package
• The rate of crack propagation is also given by
Const DK
da m
dN
• But in plastic packages under temperature cycling,
the stress concentration factor is Important
DK Const ( moldingcompound silicon ) Tmin Tneutral
• α is the TCE of MC.
DT in temperature cycling-driven models is the temperature difference
between the neutral (usually cure) temperature, and the minimum
temperature of the cycle. Tmax is less important.
8/2-4/2011 Plastic Package Reliability 85
© C. Glenn Shirley
88. Package Cracking and Delamination..
..damages Wires, Bonds, and Passivation Films.
Wire Shear
Normal (tensile)
Crack
Shear
Au
Substrate Damage
Silicon
Thin-Film Cracking
8/2-4/2011 Plastic Package Reliability 86
© C. Glenn Shirley
89. Bond Damage: Wires and Ball Bonds
• Cracks can intersect wires, TAB leads.
• Bonds can be sheared at the bond/pad interface
• Shear and tensile normal stress can break wires at
their necks.
• Substrate cracks induced during bonding can
propagate and cause “cratering” or “chip-out”.
8/2-4/2011 Plastic Package Reliability 87
© C. Glenn Shirley
90. Wire Damage
(Open)
Wires sheared by wire crack
8/2-4/2011 Plastic Package Reliability 88
© C. Glenn Shirley
91. Bond Damage
Sheared Bond Unfailed Bond
20 m
Die Corner
Ball bonds in plastic package after temperature cycle.
8/2-4/2011 Plastic Package Reliability 89
© C. Glenn Shirley
92. Bond Damage
Necking Damage
8/2-4/2011 Plastic Package Reliability 90
© C. Glenn Shirley
93. Bond Damage
Necking fracture
8/2-4/2011 Plastic Package Reliability 91
© C. Glenn Shirley
94. Bond Damage
Delamination induced down bond fail after temperature cycle
8/2-4/2011 Plastic Package Reliability 92
© C. Glenn Shirley
95. Bond Damage
Cratering damage on bond pads
8/2-4/2011 Plastic Package Reliability 93
© C. Glenn Shirley
96. Bond Damage
Die
Bond shear at die corners after temperature cycle
8/2-4/2011 Plastic Package Reliability 94
© C. Glenn Shirley
97. Bond Damage and Delamination
A8
Intermetallic fracture at bond due to
shear displacement.
44 PLCC devices that failed after solder
A7
Pulse-echo acoustic image of mold compound/ die reflow and 1000 cycles (-40A9 125C)
to
interface in four devices. Delamination is shown in
black. White boxes added to show locations of low
Source: T.M.Moore, R.G. McKenna
bond wire pull strength results.
and S.J. Kelsall, IRPS 1991, 160-166.
8/2-4/2011 Plastic Package Reliability 95
© C. Glenn Shirley
98. Bond Damage (TAB)
Cu Lead Cu Lead
Ti barrier Au bump Au bump
Etch
Crater
Al pad
Substrate Crack
Barrier crack and Au/Al intermetallic
Silicon
TAB cratering and diffusion barrier damage revealed by wet etch.
8/2-4/2011 Plastic Package Reliability 96
© C. Glenn Shirley
99. Bond Damage (TAB)
TAB bonds Au/Al intermetallic formed at cracks in Ti barrier
8/2-4/2011 Plastic Package Reliability 97
© C. Glenn Shirley
100. Bond Damage (TAB)
Crater under TAB bonds
8/2-4/2011 Plastic Package Reliability 98
© C. Glenn Shirley
101. Thin-Film Cracking (TFC)
Wire Shear
Normal (tensile)
Crack
Shear
Au
Substrate Damage
Silicon
Thin-Film Cracking
8/2-4/2011 Plastic Package Reliability 99
© C. Glenn Shirley
102. TFC - Plastic Conforms to Die Surface
Die Surface
Replica in Plastic
8/2-4/2011 Plastic Package Reliability 100
© C. Glenn Shirley
103. TFC – Effect on Thin Films
Die Corner
Aluminum Cracks
Polysilicon A B
Die center
Shear stress applied to passivation
Passivation Aluminum
A Crack Crack B
PSG
SiO2
Channel Polysilicon
8/2-4/2011 Plastic Package Reliability 101
© C. Glenn Shirley
104. Thin-Film Cracking (TFC)
1 micron
Source: K. Hayes, Intel
Passivation delamination crack propagates into substrate.
8/2-4/2011 Plastic Package Reliability 102
© C. Glenn Shirley
105. Test Chip
• Thin film cracking can be detected electrically by test
structures in the corner of the die.
– Sensitive to opens and to shorts.
• Buss width is varied to determine design rule.
Die edge (saw cut). TFC sensor
Edge ring
TFD
TFC (20 um bus)
Metal 5
TFC (40 um bus)
Metal 4
Via 4
BOND PADS Minimum
Minimum
ATC X
Minimum
TFC (10 um bus) TFC (100 um bus) 100 microns
X = 10, 20, 40, 100 microns
8/2-4/2011 Plastic Package Reliability 103
© C. Glenn Shirley
106. TFC – Effect of Buss Width
Factors Affecting TFC: Buss Width Effect
Polysilicon
meanders under
buss edge are
vulnerable to No Contacts
crack-induced
opens.
17 m contacts
Buss Widths
3 m contacts
21 m 7m 105 m
Source: Shirley & Blish, “Thin Film Cracking and Wire Ball Shear...,” IRPS 1987.
8/2-4/2011 Plastic Package Reliability 104
© C. Glenn Shirley
107. TFC – Effect of Buss Width, ct’d
Factors Affecting TFC: Buss Width Effect
70
50
30
% Fail 105 micron bus, no slots or contacts
10
5
2
1
Busses with slots and/or contacts
.1
10 100 1000
Cycles
Narrow buss, or contacts, stabilizes buss, reduces incidence of TFC.
Leads to buss width design rules, and buss slotting in die corners.
8/2-4/2011 Plastic Package Reliability 105
© C. Glenn Shirley
108. TFC – Effect of Temperature Cycle
• Drivers: T/C conditions, and number of cycles.
• Mimimum T/C temperature, not amplitude, is key
aspect of stress.
– Stress depends on difference between cure temperature
(neutral stress) and minimum stress temperature.
95
-65 C to 150C
Same amplitude!
-40 C to 85 C
80
0 C to 125 C
60 125 C Amplitude
Source: C. F. Dunn and J. W. McPherson, “Temperature-
40 Cycling Acceleration Factors for Aluminum Metallization
Cum % Failure in VLSI Applications,” IRPS, 1990.
Fail 20
10
5
2
1
10 100 1000
Cycles
8/2-4/2011 Plastic Package Reliability 106
© C. Glenn Shirley
109. TFC – Effect of Passivation Thickness
100
• Fraction of PDIP- Source: A. Cassens, Intel
packaged SRAM failing.
80
• Post 1K cycle of T/C C.
• No Polyimide die coat. 60
%
• Thicker passivation is
Failing 40
more robust.
20
0
0.5 0.6 0.7 0.8 0.9 1.0 1.1
Total Passivation Thickness in microns
8/2-4/2011 Plastic Package Reliability 107
© C. Glenn Shirley
110. TFC – Effect of Compliant Overcoat
• SRAM in PDIP
• Temperature Cycle Condition C
• Polyimide Overcoat
200 cycles 500 cycles 1000 cycles
No Polyimide 0/450 13/450 101/437
Polyimide 0/450 0/450 0/450
8/2-4/2011 Plastic Package Reliability 108
© C. Glenn Shirley
111. Theory of TFC
• Shear stress applied to die surface by MC
– Is maximum at die corners
– Zero at die center.
(At die Surface)
Die
8/2-4/2011 Plastic Package Reliability 109
© C. Glenn Shirley
112. Theory of TFC, ct’d
• Buss width effect: Okikawa et. al.
• Passivation thickness effect: Edwards et al.
• TFC occurs when and where
2
t
( Passivation Surface) K E
L
• K = dimensionless constant
• E = Young’s modulus of passivation
• t = Passivation thickness
• L = Buss width
Thicker passivation, and/or narrower busses implies less TFC.
Sources: Okikawa, et al. ISTFA, Oct. 1983. Edwards, et al. IEEE-CHMT-12, p 618, 1987
8/2-4/2011 Plastic Package Reliability 110
© C. Glenn Shirley
113. Outline
• Plastic Packages
• Stress and Test Flows
• Thermal Mechanisms
• Moisture Mechanisms
• Thermo-mechanical Mechanisms
• Moisture-mechanical Mechanisms
• Technology Update
8/2-4/2011 Plastic Package Reliability 111
© C. Glenn Shirley
114. Thin Film Delamination
• Saw cut exposes thin film edges to moisture..
Polyimide
PECVD Oxynitride/Nitride Metal Bond Pad
Other films
Silicon
• And shear stress tends to peel films.
Shear stress Thin film delamination.
Moisture
Thin films
Substrate (Si)
8/2-4/2011 Plastic Package Reliability 112
© C. Glenn Shirley
115. Test Chip
• “Edge rings” are lateral moisture barrier.
• Effectiveness of edge rings can be tested electrically
by a TFD sensor on a test chip.
Edge ring Die edge (saw cut).
TFC (20 um bus) TFD Cross section of TFD sensor
TFC (40 um bus)
thin film#7
BOND PADS
thin film#6
ATC thin film#5
thin film#4
thin film#3
thin film#2
TFC (100 um bus) thin film#1
TFC (10 um bus)
substrate
interconnect via
8/2-4/2011 Plastic Package Reliability 113
© C. Glenn Shirley
116. Thin-Film Delamination
Edge ring
TFD Sensor
Source: C. Hong
Intel
Delamination at die edge after 168 hours of steam.
8/2-4/2011 Plastic Package Reliability 114
© C. Glenn Shirley
117. Thin-Film Delamination
Edge Ring
Crack breaks
continuity of
TFD sensor
10 m Source: C. Hong
Intel
Delamination at die edge after 168 hours of steam.
8/2-4/2011 Plastic Package Reliability 115
© C. Glenn Shirley
118. Popcorn Mechanism
Early life failure rate.
ELFR 168 hrs
JESD22-A108
Preconditioning.
PC JESD22-A113
HTOL HTSL (Bake) TC THB or HAST
High temperature 1000 hrs 700 cycles 1000 hrs (85/85)
operating life. JESD22-A103 3 cycles/hr JESD22-A101
168 -1000 hrs 233 hrs 96 hrs (130/85)
JESD22-A108 JESD22-A104 JESD22-A110
Condition B or G
(C is too severe)
8/2-4/2011 Plastic Package Reliability 116
© C. Glenn Shirley
119. Popcorn Mechanism
Moisture Absorbtion
a During Storage
t
Moisture Vaporization
During Solder
Pressure Dome Delamination Void
Pressure in Void = P
Bond Damage
Plastic Stress Fracture
Package Crack Collapsed Voids
Plastic package cracking due to “popcorn” effect during solder reflow
8/2-4/2011 Plastic Package Reliability 117
© C. Glenn Shirley
120. Popcorn Damage
Plastic package cracking due to “popcorn” effect during solder reflow
8/2-4/2011 Plastic Package Reliability 118
© C. Glenn Shirley
121. Popcorn Damage
B-Scan
line A8
SEM of cross section
Pulse-echo acoustic image through
back of 68PLCC that developed popcorn
A7 cracks during solder reflow A9
Source: T.M.Moore, R.G. McKenna and S.J. Kelsall,
in “Characterization of Integrated Circuit Packaging
Materials”, Butterworth-Heinemann, 79-96, 1993. Acoustic B-scan
8/2-4/2011 Plastic Package Reliability 119
© C. Glenn Shirley