In this webinar, you'll learn: Why your stackup is critical to overall design success Key elements that comprise PCB board stack-ups (power planes, balance, flex / rigid-flex, etc) Material selection tips and guidelines Considerations for determining the optimal layer count Determining impedance targets and how your stack-up affects your ability to meet your impedance goals How to leverage your stackup to ensure design accuracy and good signal quality with your CAD system An overview of embedding components and the costs/benefits

1. How Does Your Stack-Up, Stack Up?
5/30/2019 How Does Your Stack-Up, Stack Up? 1
A Webinar By EMA Design Automation
Presenters:
Matthew Harms
Sue Frederick

2. Poll Question
First Question
2How Does Your Stack-Up, Stack Up?5/30/2019
• How many layers are your boards
usually?

3. Meet your Presenters
Application Engineers from EMA
3How Does Your Stack-Up, Stack Up?5/30/2019
Matthew Harms is an
Electrical Engineer and has
been an AE at EMA for 16
years
Sue Frederick is an
Electrical Engineer and has
worked with Cadence
software for over 20 years

4. Agenda
Topics for today
4
• Design Cycle Impact
• Importance of Collaboration
• Stack-up Composition
• Available Materials
• Picking Layer-count
• Impedance
• Embedding Components
How Does Your Stack-Up, Stack Up?5/30/2019

5. Impact on Design Cycle
5
Unpredictable
Schedules
Communication
Delays
Interrupted
Work Flows
Increased
Development Costs
Delayed Release To
Manufacturing
How Does Your Stack-Up, Stack Up?5/30/2019
Increase MFG
Costs

6. Importance of Collaboration
Work with the board manufacturer
6
• Cost implications of decisions
• Via types
• Core materials
• Stack-up count
• Manufacturability
• Meet impedances
• Limit Design for Manufacturability errors
• Constraints
• Minimum tolerances
• Lead time for uncommon materials
and/or processes
How Does Your Stack-Up, Stack Up?5/30/2019

7. What Is a Stack-Up…
Think Vertical
7
• The PCB stack-up design plays a central
part in the overall system performance
It is the substrate upon which all design
components are assembled
How Does Your Stack-Up, Stack Up?5/30/2019

8. Stack-up Composition
Single, Dual and Multilayers
8
• Single
(1-layer PCB)
• Dual
(two-sided PCB)
• Multi-Layer
How Does Your Stack-Up, Stack Up?5/30/2019

9. Stack-up Composition
Plane Pairs
9
• Multi-Layer stack-ups are made up of
plane pair cores and merged together
using a suitable dielectric material
• Fun Fact: Pre-preg is short for ‘Pre-
Impregnated’ with Resin
How Does Your Stack-Up, Stack Up?5/30/2019

10. Stack-up Composition
Material Build-up / Balancing
10
• A poorly designed PCB stack-up with
inappropriately selected materials can degrade
• electrical performance of signal transmission
• power delivery
• manufacturability
• The stack-up should be symmetrical from
the center out for balancing
How Does Your Stack-Up, Stack Up?5/30/2019

11. Stack-up Composition
Soldermask effects
11
• Soldermask is avoided when
sensitive circuitry is involved
• It is lossy at high frequencies
• high in moisture absorption
• contributes to dispersion effects
• the thickness can vary
• can have a wide range of
dielectric constants
How Does Your Stack-Up, Stack Up?5/30/2019

12. Stack-up Composition
Rigid/Flex Sections
12How Does Your Stack-Up, Stack Up?5/30/2019
Many reasons to use
Rigid and Flex together:
• Wiring that works
• Miniaturization &
weight reduction
• 3D packaging
• Fewer device
interconnects

13. Stack-up Composition
Rigid/Flex stack-up
13
• Core material traversing rigid and flex
• Unique materials and properties used
on flexible portion
• Traditional stack-up used in Rigid portion
How Does Your Stack-Up, Stack Up?5/30/2019

14. Stack-up Composition
Outline and Connector Import
14
• Work with MCAD team to bring in important
mechanical details
• Board outline
• Connector placements
• Height constraints
How Does Your Stack-Up, Stack Up?5/30/2019

15. Available Materials
FR4 Dielectric Material
15
• FR-4 (woven glass-epoxy) is the most
common dielectric material and delivers
good:
• performance for cost
• manufacturability and durability
• electrical properties
* Fun Fact: FR is short for Fire Retardant
How Does Your Stack-Up, Stack Up?5/30/2019

16. Available Materials
Advanced Dielectric Materials
16
• When advanced electrical properties and
performance are critical to your designs,
other materials are needed that offer:
• Lower dielectric loss
• Low electrical signal loss
• Increase heat resistance
How Does Your Stack-Up, Stack Up?5/30/2019

17. Available Materials
Polyimide Dielectric Materials
17
• Polyimide is commonly used in Rigid
Flex designs for its excellent
flexibility/bendability across temperatures
• is available under several trademarks
How Does Your Stack-Up, Stack Up?5/30/2019

18. Available Materials
Copper is King
18
• For electrical connections, copper is the most
common material used as the cost vs
performance tradeoff is favorable
• Nickel plating is used in some industries
(medical)
• Gold flashing/plating can be used as well
How Does Your Stack-Up, Stack Up?5/30/2019

19. Available Materials
Thickness of Copper
19
• The most common unit of measure for the
copper thickness on a PCB is ounces (oz)
• 1 oz of copper is pressed flat and spread
evenly over a one square foot area yields 1.37
mils (35 um) of thickness
* Fun Fact: household aluminum foil is ~ 0.63 mils or
the thickness of ½ oz copper
How Does Your Stack-Up, Stack Up?5/30/2019

20. • You will need a thicker conductor layer (2 oz,
3 oz…) if you need to carry more current and
maintain a certain temperature
• IPC-2221
• Section 6.2
Available Materials
Cost / Performance
20How Does Your Stack-Up, Stack Up?5/30/2019

21. • As the trace-width is reduced, the height of
the trace must shrink along with it
• Acids attack the sides of the traces in
contact with the substrate material more
aggressively causing a trapezoidal effect
• The width of the copper at the base may
become too narrow and fail:
Available Materials
Minimum Width
21How Does Your Stack-Up, Stack Up?5/30/2019

22. • Imbalanced etching of larger copper areas
can contribute to layer stress and warpage
• Layers which are etched leaving heavy and
light portions of imaging create a balancing
challenge
Available Materials
Etch Balancing
22How Does Your Stack-Up, Stack Up?5/30/2019

23. Available Materials
Surface Roughness
24
• The rougher the copper profile, the higher
the dielectric constant for the same dielectric
thickness
• Higher roughness profile adds additional
capacitance, increasing the dielectric
constant, due to reduced separation between
the two large parallel plates
How Does Your Stack-Up, Stack Up?5/30/2019

24. Picking Layer-count
Board Density / Escape Layers
25
• The escape routing from large BGAs usually
determines the number of routing layers
required in a complex PCB
• Most connections must be channeled directly
to an inner layer to be routed out of the BGA
How Does Your Stack-Up, Stack Up?5/30/2019

25. Picking Layer-count
Input from SI Group
26
• SI groups often request high-speed lines
routed on internal layers with enough power &
ground nearby to reduce EMI
• May request back-drilling on vias or
blind/buried vias to eliminate stubs and the
reflections that they generate
How Does Your Stack-Up, Stack Up?5/30/2019

26. Picking Layer-count
Input from Power Group
27
• Thickness of copper and number of planes is
adequate for expected current load
• Temperature rise is within design specifications
How Does Your Stack-Up, Stack Up?5/30/2019

27. Picking Layer-count
Can Split Planes Help?
28
• With the increase of power levels needed,
split planes can become necessary
• They come at a cost of greater signal
integrity complexity
How Does Your Stack-Up, Stack Up?5/30/2019

28. Picking Layer-count
How many power planes to use?
29
As many as you can afford…
• Half or fewer of your electrical layers will
be power or ground
• Half of those layers will go to power, the
others to ground
• Power and ground are often right next to
each other
• Why so many?
• Help reduce EMI
• Lower impedance
• Minimize loop currents
How Does Your Stack-Up, Stack Up?5/30/2019

29. Picking Layer-count
Compare Board Thickness to Via Size
• The aspect ratio is the thickness of the
board versus the width of the via
• Hole sizes that are small compared with the
board thickness can result in unsatisfactory
plating
• The larger the aspect ratio, the more difficult
it is to achieve reliable plating
How Does Your Stack-Up, Stack Up?5/30/2019

30. Impedance
Microstrip / Stripline
31
• Microstrip is a trace routed on an external
layer
• Stripline is a trace routed between two
power layers
• Stripline is often desired by the SI group for
having less EMI radiation
How Does Your Stack-Up, Stack Up?5/30/2019

31. Impedance
Trace Width / Thickness, Dielectric Thickness & Material
32
• The dielectric constant of the material
used to separate traces from their return
path play a major role in determining the
trace impedance
• Impedance can then be controlled through
the width of the trace, the space between
signal trace and signal return path, relative
dielectric coefficient of material, and the
thickness of the trace
How Does Your Stack-Up, Stack Up?5/30/2019

32. Impedance
Formulas
33
For Microstrip:
How Does Your Stack-Up, Stack Up?5/30/2019
For Symmetric Stripline:

33. Impedance
Differential Pairs
34
Even, Odd, Common
and Differential
Impedances
Spacing of signal
layers relative to power
planes is important
How Does Your Stack-Up, Stack Up?5/30/2019

34. Impedance
Glass Fiber Weave
35
Routing traces at an angle off the Fiber Weave
will maintain consistent impedance
How Does Your Stack-Up, Stack Up?5/30/2019

35. Impedance
Frequency Dependence
36
• Materials in your stack-up are frequency
dependent, meaning that your impedance
will vary with frequency as well
• Consider at higher frequencies
How Does Your Stack-Up, Stack Up?5/30/2019

36. Impedance
Field Solver vs. Equations
37
Field solvers use Maxwell’s equations and are
generally more accurate than using equations
directly
How Does Your Stack-Up, Stack Up?5/30/2019

37. Embedding Components
Passive/Active Components In-Board Due to Density
38
• With increased board density, additional
space to place components is necessary
• Option to embed components or to create
cavities to store them in
How Does Your Stack-Up, Stack Up?5/30/2019

38. Goals to Aim For
Five Take-Aways for Multi-Layer Boards
39
1. Signal layers always adjacent to planes
2. Signal layers coupled closely to their planes
3. Ground and power planes that are coupled
together as closely as possible
4. Routing of high-speed signals through buried
layers between planes to contain radiation
5. Multiple ground planes to lower impedance and
radiation
How Does Your Stack-Up, Stack Up?5/30/2019

39. Poll Question
Second Question
40How Does Your Stack-Up, Stack Up?5/30/2019
• What do you use to determine
impedances of traces on your board?

40. Demonstration
With Sue Frederick
41
• Stack-up creation templates
• Materials available
• Impedance measurements
How Does Your Stack-Up, Stack Up?5/30/2019

41. Poll Question
Third Question
42How Does Your Stack-Up, Stack Up?5/30/2019
• Do you reuse stackups between
designs?

42. 43
Minimize
Manufacturing Costs
Streamline
Schedules
Minimize
Communications
Delays
Improve Time
To Market
How Does Your Stack-Up, Stack Up?5/30/2019
With A Good Stack-Up You Can:

43. Hitchhiker’s Guide
to PCB Design
44
• Don’t Panic – it’s a free download
• Chapter 7 is on Stackup
• https://pages.ema-eda.com/Hitchhikers-
Guide-to-PCB-Design
How Does Your Stack-Up, Stack Up?5/30/2019

44. 45
Thank you for joining us today.
Questions?
Next Webinar:
Power Supply Design
EMA Design Automation
800-813-7494
matthewh@ema-eda.com
suef@ema-eda.com
www.ema-eda.com
How Does Your Stack-Up, Stack Up?5/30/2019