Why consistency is needed in PCB manufacturing

Article By : Kella Knack

When it comes to developing the pieces of hardware, the process is not so simple. With PCB development, the process becomes even more challenging.

As an industry, those of us involved in designing and manufacturing electronic products can all agree that we now live and operate in a global supply chain environment. Since a lot of what is incorporated into current and next generation products is reflected in the software, this isn't much of a concern. Take your favourite products, download the latest software update and newly developed apps, and you're ready to go.

When it comes to developing the pieces of hardware, the process is not so simple. And, when it comes to printed circuit board (PCB) development efforts, the process becomes even more challenging. That's because PCBs are the launching points for hardware product development and the laminate and prepreg materials used in designing and manufacturing PCBs are the nuclei for those boards. (Prepreg is fibreglass cloth that has been saturated with resin that is not fully cured. As a PCB is placed under the heat and pressure of lamination this resin melts and flows into the voids in the adjacent copper layers filling them.)

The global aspects of the PCB development process are pretty much carved in stone—design and prototype the product in the U.S. and then move volume production offshore. The challenge lies in ensuring that the laminates and prepregs used for U.S. prototyping efforts will be the same as those used in offshore volume production. On the surface, the seamless transparent transition process for utilising the same PCB laminates from prototype to the full up product processes should be a "no brainer" and one that should not be subject to much scrutiny but that is not the case. This article will discuss what takes place in today's design/prototyping environments and the challenges that ensue in the realm of volume production.

What's different?

When electronic products were not nearly as complex as they are now, laminate and prepreg selection was not that big of a deal. Almost everything could be done using some iteration of FR-4 class material. Products were forgiving enough that using an FR-4 class material for the U.S. prototyping effort and then moving to a similar but not identical iteration of it for off-shore volume production was OK. Specifically, it was, and often still is, the practice of off-shore volume manufacturers to substitute the materials that are called out on the stackup drawings provided as guidelines for PCB fabrication. In fact, in some instances, product development companies have welcomed the opportunity to save money wherever or however they can and having offshore fabricators switch to a lower-cost, similar but not necessarily totally equivalent material is one path to realising these savings.

So, let's forward to today's product development environments. High-speed boards once occupied the niche of select, sophisticated pieces of hardware. But, by virtue of the components mounted onto it, today, every PCB is high-speed regardless of its final product implementation. And, as has been pointed out in a number of articles, technical presentations and conference panels, in many instances, we are bumping up against what is achievable in terms of performance parameters in even the fastest of the high speed laminates. There is not much more "there, there" in moving up the performance curve with laminate materials. The next step is photo optics but this is a huge step requiring massive changes in not just design processes but also in equipment tooling and manufacturing operations. Simply put, the transition to photo optics is not technically or economically feasible at this point in time. As a result, we are often called upon to wring the last ounce of performance capabilities out of existing laminate materials. As a consulting firm, Speeding Edge is frequently exhorted to try and exercise some Rocky/Bullwinkle "watch me pull a rabbit out of my hat" magic that really pushes the envelope in terms of what is practicable.

Next: Designing PCBs: Who owns the problems? »

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