Printed Circuit Design & Fab Online Magazine

Board Talk

Jeffrey Beauchamp Successful BGA routing depends less on pushing density limits and more on making fabrication-aware decisions early in the layout process.

For a long time, I have wanted to provide engineers with straightforward, specific guidance when starting a ball grid array (BGA) layout to complement the overall guidelines from many PCB fabricators. BGA routing often appears straightforward during layout, but many of the real challenges emerge later during fabrication, assembly, testing or field use. A design may pass CAD checks but still cause avoidable manufacturing problems if routing decisions are made without considering how the board would be built. For engineers new to BGAs, the objective should not be to maximize density or use advanced techniques prematurely. The goal is to apply disciplined design choices that are manufacturable, reliable and scalable.

Read more: A Beginner’s Guide to BGA Routing That Won’t Come Back to Bite You

Jeffrey Beauchamp Catch heat at the board before it turns into a full-time job.

Heat sneaks up fast in today’s electronics. Higher power density, smaller form factors and long-life reliability expectations all collide, requiring better thermal design. The teams that come out on top with this challenge are the ones who solve heat at the PCB level rather than trying to fix it later with a bigger heat sink or more airflow.

Read more: Metal-Core PCBs and Thermal Management

Jeffrey Beauchamp Not every design is practical for every volume.

Not long ago, a customer sent us an 8-layer rigid PCB design for quotation. On the surface, nothing unusual – until we noticed the minimum finished hole size (FHS) was 4 mils. That number might not sound alarming, but in PCB manufacturing, 4 mils is a red flag. Here’s why.

The issue arises when fabricators drill a plated through-hole (PTH) and deposit copper during plating. The remaining diameter after this process becomes the finished hole size. A 4-mil FHS with a tolerance of ±4 mils technically ranges from 0 to 8 mils. That kind of spread becomes nearly impossible to maintain in volume production.

Read more: Minimum Finished Hole Size and How it Impacts Manufacturability

The question not asked may be cause for concern.

It is essential for PCB fabricators to ask their customers engineering questions before production. Clarifying design requirements and expectations ensures they are fully understood, preventing costly errors, avoiding liberties being taken in the fabrication process, resulting in a product that meets both performance and reliability standards.

I write this not only to set clear expectations for customers but to strongly caution that when questions are not asked, there may be cause for concern. Questions must be asked so we can align objectives. The PCB is custom manufactured, and in many cases, the fabricator is either replicating something another manufacturer has built or creating something entirely new. In both scenarios, setting clear expectations is critical. If someone else has built it, we must know what we’re matching. Conversely, if the part number is a first-time build, the customers must understand that we’re doing something that has not been achieved.

Read more: Assumption vs. Accuracy: Why We Ask Engineering Questions