While many perceive high-tech PCBs as those with more layers, our aim is to outline the key areas that need to be understood when evaluating the capabilities of 2- and 4-layer PCB manufacturers. These versatile and cost-effective circuit boards can be as high-tech as their multi-layer counterparts, and our objective is to educate our audience as to what to look for to ensure that you get exactly what you are looking for.
Low Layer Count PCBs - Why They Are Not All Created Equal Because of changes in technology, 2- and 4-layer PCBs continue to be at the forefront of high-tech electronics manufacturing, design strategies, manufacturing requirements, and the future of PCB technology, showcasing how these compact boards can rise to any challenge.
In this webinar, we cover design strategies, manufacturing requirements, and the future of PCB technology, showcasing how these compact boards can rise to any challenge. We will also delve into the advantages and limitations of 2- and 4-layer PCBs, compare them to multi-layer boards, and discuss design tips to maximize their performance.
For more information on our printed circuit board solutions, visit https://www.epectec.com/pcb/.
What are the advantages and disadvantages of membrane structures.pptx
Low Layer Count PCBs – Why They Are Not All Created Equal
1. Manufacturing That Eliminates Risk & Improves Reliability
Low Layer Count PCBs
Why They Are Not All Created Equal
02.15.2024
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Why Talk About Low Layer Count Circuit Boards?
“…..anecdotal evidence tells us that most of the PCBs used
are double sided (two layer) and four layer in everyday
production….”
- Supporting American Printed Circuit Boards Act of 2022: An Appraisal
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Agenda
The basics of 2- and 4-layer PCBs – what you had to look for …
Technology changes that have made 2- and 4-layer PCBs more attractive –
then vs. now.
What design considerations change the game in terms of cost and reliability –
you will be surprised.
Material selection – what is the impact on performance?
Everyone can make these, so everyone’s quality is the same – right?
Cost vs. functionality – why 2- and 4-layer boards work for many applications.
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2/4 Layer PCB Basics
Multilayer plated through-hole PCBs
invented in the 1960s.
Double-sided plated through-hole PCBs
invented in the early 1940s.
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Old School DS & 4-Layer
Look at how little copper is left
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Old School – 2-Layer & 4-Layer Through Hole
Quality of Plated Through Hole
– Very simple as the holes were large
– Plating a through hole is all about
getting fluid through the drilled hole
Quality of the Etched Circuit
– Didn’t need to be very defined
– Plenty of space to meet IPC spec
– Impedance wasn’t a big issue
– Shorts and opens
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Old School 2- & 4-Layer PCBs
Driven by cost or functionality
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What Are The New Design Considerations?
Fine lines and spaces -
0.004” and lower
Very small holes – less than
10 mils
Solder mask dams as small
as 4 or 5 mils
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How Do All Of These Design Considerations Affect Cost?
They all:
– Require specialized equipment
• To be done right
– Have a high effect on yield
– Add time to process
Why?
– Less room for error
– 0.004” trace - +/-0.0004
– 0.015” trace - +/-0.0015
Over-etched PCB
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Some ways to help …
Different ways to treat vias
Always use the largest features
possible – holes, traces and spaces
Make sure you DFM your BGA
designs
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Material Selection on 2- and 4-Layer PCBs
Old School Thinking:
– Use high Tg material on all
through hole PCBs
Today:
– Unless you plan on doing
extensive re-work to the
PCB, do you really need it?
NOTE: Tg or Glass transition temperature, is the base material
parameter for the temperature (°C). It defines at what temperature the
base material becomes mechanically unstable. It is not the PCB
maximum operating temperature, but rather that which the PCBA can
endure for a short time before it deteriorates.
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Can You Really Re-Work These PCBs?
Sure – SMD don’t require as much heat
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Here Is Where It Matters …
It will take a ton of heat to get
the large through hole
components out.
If you have a large PCB where
you will want to regularly replace
a component.
Tg 130 vs Tg 180.
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Impedance Control and RF Circuits on 2/4 Layer
Can it be done?
– Sure can
Biggest challenges:
– Impedance features vs.
soldered features
– Important to keep the
soldered features the same
size and away from ground
planes
Using trace design to create
the desired impedance
This rule aims to solve a manufacturing problem known as tombstone.
During reflow, a too large connection to an SMD pad acts like a heatsink,
creating a situation where one side of the component has a slightly lower
temperature. Because of this, one side of the component can lift up from
the PCB. This is especially true for small (0402 and smaller) components.
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Everyone Can Make 2- & 4-Layers, Right?
Yes and no
Through hole – YES
Tight spaced, less than 10 mil
via and 5 mil dams – NO
Equipment matters
Registration and trace quality
Solder mask dam quality
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Everyone Can Make 2- & 4-Layers, Right?
Quality Registration
Old Way
– Panel tooling holes
New Way
– Registration to features
on each panel or PCB to
improve quality and yield
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Even The Small Things Matter – Inkjet Printing
Much faster and consistent process
More functionality
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Cost vs. Functionality
#1 rule of thumb – Always make it as big as you can.
– Improves long-term reliability
– Reduces cost
– More room for error – pure math
If it needs small features and tight tolerances – make sure that your
fabricator has made the necessary investment to be successful.
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What’s Next For 2- & 4-Layer PCBs?
Features will be getting smaller
Semiconductors will be getting
more functionality
– Making 2/4 layers cost-effective
Additional technology will be
developed and required
Fabricators will need to invest to
be successful
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Summary
Not all PCBs are created equal.
Feature size is more important than layer
count.
Not all fabricators have made the
investment in equipment needed to keep up
with the smallest features and tight
tolerances.
Use fabricators’ DFM services to check your
work while in development.
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You can quote and order circuit boards up to 16-layers online with
InstantPCBQuote™.
– Standard and Expedited Lead Times
– Various Material and Surface Finish Options
– Controlled Impedance, Controlled Dielectric, Via in Pad
Go to www.epectec.com/instantpcbquote/ to get started.
Did You Know?
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Q&A
Questions?
– Enter any questions you may have
in the control panel
– If we don’t have time to get to it, we
will reply via email
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Thank You
Check out our website at www.epectec.com.
For more information email sales@epectec.com.
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