As electronics keep getting smaller and more advanced, the need to connect flexible printed circuits (FPCs) to rigid PCBs continues to grow. In this article, Workingbear will walk you through the most common methods used in the industry today—and share some practical insights from real-world experience.
Flexible printed circuits (FPCs) are widely used because they can bend and fold. They’re perfect for compact products or for connecting signals between different PCBAs. But there’s a downside. As usage increases—especially in applications with repeated motion—FPCs can develop open circuits or intermittent connections over time.
Recently, my company started seeing an increase in field returns caused by open circuits in flexible printed circuits (FPCs) inside the terminal. After digging into several cases, the root cause turned out to be broken copper traces. So what’s going on?
As electronic devices keep getting thinner and more compact, FPCs (flexible printed circuits) are used more and more. In some designs, FPCs even replace traditional PCBs. But no matter how advanced FPC technology becomes, it still needs to connect to a rigid PCB in the end—and most of the time, that interface is a connector. That’s why designing FPCs for manufacturability (DFx) is so important.
Early on, Workingbear thought FPC design was mainly about getting the layout right and choosing the correct stiffener thickness under the gold fingers or edge board contacts—making sure it’s not too thick to fit into the connector or too thin to stay secure.
Recently, our team ran into a painful issue: cracked traces on an FPC. The problem quickly escalated, tying up engineering resources and causing significant losses for the supplier as well. As often happens after a failure, an old debate resurfaced—should FPCs use Rolled & Annealed (RA) copper or Electro-Deposited (ED) copper?
