Short answer: Three design decisions make PCB manufacturing harder far more often than outright errors do: tolerances tighter than the fabrication or assembly process can hold, exotic or single-source materials chosen for performance alone, and hole structures optimised for routing rather than fabrication. Each one passes in prototypes and then shows up in volume production as lower yield, longer lead times and higher cost. The way to avoid them is margin-based design on proven material systems, with the manufacturer’s input before routing begins – one early conversation prevents weeks of redesign.
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.
Key facts
- Manufacturing is statistical, not absolute: tolerances tighter than the process window force slower production, more inspection or lower yield, and all three raise cost.
- Typical offenders are annular rings below the fabricator’s process window, hole-to-copper clearances with no margin for drill wander and impedance tolerances the stackup cannot hold.
- High-frequency laminates, specialty prepregs and uncommon copper weights bring supply risk: long lead times, prototype-to-production gaps and forced stackup redesigns.
- Every extra hole type adds process steps, inspection points and failure risk; via-in-pad is worth its filling and capping cost only with a measurable electrical benefit.
- None of these decisions is revisited once layout is complete, which is why manufacturing input belongs before routing starts.
Frequently asked questions
Why do tight PCB tolerances increase manufacturing cost?
Because fabrication and assembly processes are statistical. When a tolerance is tighter than the natural process capability, the manufacturer has to slow down, inspect more or accept lower yield, and all three raise the price per board.
Are high-frequency laminates and special materials a problem for PCB production?
Not technically, but commercially: they often have long lead times, inconsistent availability between prototype and series, single-source risk and volatile cost, which can force a stackup redesign when volumes grow.
When is via-in-pad justified?
Only when it delivers a measurable electrical benefit. It adds filling, capping and extra quality control, so without a clear justification it usually creates more problems than it solves.
How does Comtec Labs help avoid these three problems?
We review tolerances, material availability and hole structures with your designers before routing begins, and we evaluate every material for sourcing stability from prototype to mass production, not only for performance.
Ready to reduce PCB surprises?
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