In PCB projects, manufacturing problems rarely come from dramatic
design errors.
Much more often, they originate from perfectly
reasonable design decisions that were made in isolation—without
full visibility into how the board will actually be fabricated,
assembled, tested, and scaled.
At Comtec Labs, we see the
same patterns repeating across industries: industrial electronics,
medical devices, automation, and emerging hardware startups. The
designs are electrically sound. The simulations pass. The
prototypes work.
And yet, when production begins, costs rise, lead times stretch, and
yield drops.
In this article, we explore three PCB design decisions that
frequently make manufacturing harder than it needs to be: overly
tight tolerances, exotic or low-availability materials, and hole
structures that are not designed with fabrication and assembly
in mind. None of these choices are “wrong” in isolation—but all
of them can quietly turn into production risks.
Understanding
these pitfalls early is a core part of Design for Manufacturability
(DFM).
And when DFM is applied early, it saves weeks, not days.
1. Overly Tight Tolerances Without a Real Need
Modern PCB tools make it easy to specify extremely tight
tolerances.
Annular rings, trace widths, drill sizes, impedance
targets—everything can be pushed to the limit with a few
clicks. The problem is that manufacturing processes are
statistical, not absolute.
When tolerances are tighter
than the natural capability of the fabrication or assembly
process, manufacturers are forced to slow down, increase
inspection, or accept lower yields. All three increase
cost.
Common examples include:
• Annular rings
specified smaller than the fabricator’s preferred process window
•
Hole-to-copper clearances with no margin for drill wander
•
Impedance tolerances tighter than what the chosen material stackup
can reliably support
In prototypes, these designs may pass. In volume production, they often fail.
A better approach is margin-based design. If a tolerance does not directly affect electrical performance, reliability, or safety, loosening it slightly can dramatically improve yield without impacting function.
Designing with the process—not against it—is one of the most effective cost-reduction strategies available.
2. Exotic Materials With Poor Availability
Another common issue is material selection driven purely by
electrical or mechanical performance, without considering supply
chain reality.
High-frequency laminates, specialty prepregs, or uncommon copper
weights may be technically ideal. But if those materials are not
readily available—or only available from a single supplier—they
introduce risk.
Material-related risks include:
• Long lead times during
prototyping
• Inconsistent availability between prototype and
production
• Forced stackup redesigns when volumes increase
•
Cost volatility driven by low-volume sourcing
In the European market, availability can vary significantly between
suppliers.
A material that is easy to source in small quantities
may become problematic at scale.
Early collaboration with
your PCB manufacturer helps identify materials that meet performance
requirements while remaining available, stable, and
cost-effective across the product lifecycle.
At Comtec
Labs, material selection is always evaluated not only for
performance,
but also for sourcing stability from prototype to
mass production.
3. Hole Structures Not Designed for Manufacturing
Vias, plated through-holes, blind and buried vias—holes are
fundamental to PCB design.
But they are also one of the most
common sources of manufacturing difficulty.
Problems often arise when:
• Aspect ratios exceed reliable
plating limits
• Mixed hole types increase process
complexity
• Via structures are optimized for routing, not
fabrication
• Via-in-pad is used without clear electrical
justification
Each additional hole type adds process steps, inspection points, and
failure risk.
In high-volume production, complexity directly
reduces yield.
Via-in-pad, for example, can be a powerful
tool—but only when truly required.
It increases cost due to
filling, capping, and additional quality control. If it does not
provide measurable electrical benefit, it often creates more problems
than it solves.
Designing hole structures with fabrication
input ensures reliability, repeatability, and scalability.
Why Early DFM Changes Everything
The common thread across all three issues is timing. These
decisions are rarely revisited once layout is complete.
That
is why early DFM matters.
When manufacturing input is
included before routing begins:
• Stackups are chosen for
performance and availability
• Tolerances are aligned with
real process capability
• Hole structures are optimized for
yield, not just density
One early conversation with your
manufacturing partner can prevent weeks of redesign,
multiple
prototype spins, and unnecessary cost.
DFM is not about
limiting designers.
It is about giving them better
constraints—ones grounded in reality.
Ready to Reduce PCB Surprises?
If you’re navigating complex requirements, tight schedules, or production risk, Comtec Labs offers a full suite of services to streamline your workflow:
PCB design service
PCB prototyping service
PCB component sourcing
PCB component assembly
PCB testing service
PCB repair and modifications
Printed circuit board production
PCB mass production