1. High Performance Printed
Circuit Boards
By Joseph Y. Lee
Samsung Electro-Mechanics

2. Chapter - 1
High Performance
Printed Circuit Boards
- Introduction

3. Definitions
 Laminates – combination of a resin system and a
reinforcement material.
 Glass transition temperature (Tg) – temperature
such that resin behaving more like a gel or high
viscosity liquid rather than a solid.
 Loss tangent or dissipation factors – power loss
through the laminate material
 Epoxy - a thermosetting resin; used chiefly in
strong adhesives and coatings and laminates

4. Cross section of FR-4 and CCL
epoxy
C
u
resin
CC FR-4 glass
L fibers
void
epoxy

5. Bismaleimide Tiazine (BT) Epoxy-Based
Laminates
 Low cost
 Used in FR-4.
 Less water absorption compared to polyimide
 However, low Tg. Less tolerate of high
temperatures.
 Tradeoffs- Difficulty in drilling causes
microcracks
 Tradeoffs - brittle when lower % of resin

6. Table 1.1 High Tg Laminate Systems
Resin Reinforcement Tg (°C)
Bisamaleimide triazine-epoxy Woven E-glass 170-220
Polymide Woven E-glass 200 min
Polymide Nonwoven aramid 220 min
Polymide Woven quartz 250 min
Cyanate ester Cross-plied aramid 230 min
Cyanate ester Woven S-2 glass 230 min

7. Polyimide
 Excellent toughness – superior adhesion to
copper
 Good processability
 Highest Tg – reduce overall manufacturing
costs
 Tradeoff- very expensive
 Another tradeoff – absorbs water

8. Table 1.2 Laminate Cost Comparison
Laminate Relative Cost
Epoxy/E-glass 1x
Polyimide/E-glass 2x
Epoxy/Nonwoven aramid 1.5x
Epoxy/woven aramid 6x
Cyanate ester/S-glass 6x
PTFE/glass 3x
Polyimide/quartz 9x

9. Table 1.3 Laminate Loss Properties
Laminate Loss Tangent at 1MHz
E-glass/epoxy 0.035
E-glass/polyimide 0.035
Aramid fiber (cross-
plied)/cyanate ester 0.025
E-glass/cyanate ester 0.015
S-2 glass/cyanate ester 0.015
Quartz/polymide 0.010
E-glass/PTFE 0.001

10. PTFE (Teflon)
 Low dielectric constant and low loss tangent
 Nonpolar and hydrophobic
 E-glass widely use
 Costs cheaper than polyimide
 Tradeoffs – CTE problems caused plated-through
holes failures
z-axis expansion and
contraction

11. Choice of Materials Considerations
 Cost
 Loss tangent must be low.
 CTE (Coefficient Temperature of Expansion)
 Tg (Glass Transition Temperature)
 Modulus of tensile strength
 Water absorption
 Dielectric constant – depends applications

12. Chapter – 2
Microvias, Built-Up
Multilayers, and High
Density Circuit Boards

13. Definitions
 Plated-through holes – connect together circuits on
both sides of the board by means of a drill
 Multilayering – separate two-layer circuits could be
laminated together and then connected to each other
with plated-through holes
 Buried via – made by drilling and plating a two-sided
board and then laminating into a multilayer
 Blind via – connects outer layer circuit to an interior
layer without disturbing the layers below the interior
layer
 Microvia – very small hole or via, generally by a non-
mechanical means to connect two layers of circuitry.

14. Plated-through hole and buried vias
Plated-through hole Buried via

15. Three Laser Systems
CO2
 Fastest system
 Form vias in organic and glass reinforced dielectrics
 Cannot penetrate Cu
UV-YAG
 Slower
 Can penetrate Cu
Excimer
 Highest via resolution
 Slowest
Overall – less stringent cleanliness requirements and no
photomask is required. Cost is lower than photoprocess.

16. Sequential vs. Parallel Processes
 Sequential – circuit layers built up one at a time
(laser process)
 Parallel – individual layers are separately made,
then laminated all at once (B2IT process)
Sequential yield = 0.95 * (0.92)4 = 68% yield
Parallel yield = 0.95 * (0.92)2 = 80% yield

17. Microvia
 Much smaller
 Possible to pack much more
functionality in smaller space
 More efficient circuit routing
 Less distortion to rise time
 Lower resistance by 17x
 Less signal delay at 100MHz and above

18. Three Processes for Microvia
Via non-uniform,
Both photovia and slow process
laservia have good
anistropic etching

19. Laser vs. Photo
laser

20. Considerations
 Again, cost.
 Laser vs. Photo – depending on number
of microvias
 Yield between photovia vs. B2IT
 Microvias is the way to go.
 Reduction of # of layers is required to
reduce costs for microvias.

21. Chapter – 3
Substrates for RF and
Microwave Systems

22. What Are RF and
Microwaves?
 They are analog signals or AC signals.
 Digital signals are 0’s and 1’s.
0 – 0 volt, 1 – 2 volts.
 Wavelengths between 0.1 to 30cm.
 Cell phones are hand held radios. They
receive and transmit radio signals.
 Radio waves are electro-magnetic waves.
 An radio antennae is an inductor.

23. Transmission Lines
Metal planes
z
z

24. Impedance Matching
Z0 RL
: Reflectivity
:Transmission

25. Similar to a Capacitor
=1
Z0 RL = ∞
=2
2t0 4t0 6t0 8t0

26. Bouncing Back and Forth
= -1
Z0 RL = 0
= 0
2t0 4t0 6t0 8t0

27. Termination
=0
Z0 Z0
=1
2t0

28. IC Chip – Parasitic
Transmission Lines
Passives on Printed Circuit Board used to
correct reflectivity of parasitic transmission
lines in IC chip.
Why can we put
Ex. IC Chip with 4.5 km of metal lines in Pentium. the passives in
Metal lines form parasitic transmission lines the IC Chip?

29. Via Structures
Blind pad Blind Buried Staggered Staircase Spiral
Metal lines and vias embedded inside the PCB board do form parasitic
transmission lines as well. Passives are used to correct this.

30. Commonly Used Transmission Lines
Microstrip Stripline Coplanar Waveguide
Conductor-Backed Slotline Coplanar Strips
Coplanar Waveguide

31. Microstrip
Advantage - Most widely used. Excellent integration
with chip and lumped elements. Multilayers are
possible. Ground plane isolate the microstrip.
Disadvantage - Line losses are somewhat higher with
poorer isolation between circuits. It is unshielded and
some radiation occurs for thicker substrates depending
on dielectric constant and frequency.

32. Stripline
Advantage - No fields extend outside ground plane. Works
well with multilayers and well-shielded.
Disadvantage – It is susceptible to unwanted modes.
Crosstalking may be a problem as well.

33. Coplanar Waveguide
Very good integration with chip and lumped elements.
Series and shunt connections are relatively easy.
Disadvantage – thick substrates are required to keep
structure away from the chasis. Integration with
multilayers is poor.

34. Conductor-backed Coplanar Waveguide
Advantage – It offers less radiation loss than a pure
microstrip line. Connections can be made at the I/O’s
with ground, signal, or ground probes.
Disadvantages - It does require metal vias or plated-
through holes to connect the coplanar grounds to the
backside ground. Structure is susceptible to
unwanted parasitic modes.

35. Slotlines and Coplanar Strips
Slotline Coplanar Strips
Easy integration with chip and lump element.
Combination with microstrip located on ground plane
guarantee constant 180° phase shifts independent of
frequency for certain circuits.
However, they do not integrate well with multilayers.

36. Definitions – LTCC and HTCC
 LTCC (Low Temperature Co-fired Ceramic) –
a multilayer ceramic technology, which
processes the ability to embed the passive
elements, such as resistors, capacitors and
inductors into a ceramic interconnect package
while the active elements are mounted on the
top layer.
 HTCC (High Temperature Co-fired Ceramic)
– differs from LTCC by high temperature of
1600°C while LTCC uses a temperature of
850 to 950°C.

37. LTCC vs. HTCC
 HTCC er=10 while LTCC er=4 to 8.
 tanδ HTCC < tanδ LTCC
 Resistivity of refractory metals like W and Mo
for HTCC > resistivity of Ag metals for LTCC
 HTCC is made up of alumina particles while
LTCC is made up of glass with some alumina.
 Firing oven heating, HTCC temperature >
LTCC temperature
 Time to heat HTCC > Time to heat LTCC

38. General Design Recommendations
 Minimize # of conductor layers
 Use the widest possible lines and
spaces.
 Avoid using tracks that are not 0 or 90°
angles.
 Amount of metal should be evenly
distributed.

39. Organic PWB’s
 FR-4 is the most easily manufactured
laminate material.
 Thick metal ground plane provide high
heat flow.
 Lower costs compared to ceramics.
 Dielectric constant and dissipation
factors, same as ceramics if not better.

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