Flex and Rigid-Flex PCBs: What We Learned from Dealing with It
Being in the PCB business, we encounter a variety of PCBs in the market. The continuous evolving technology in the electronic industry contributes to more and more different designs and applications for PCBs. Majority of the products we deal with are rigid PCBs, used in various applications. However, from time to time we come across customers in need of flexible PCB solutions. Coming from a background of majorly studying rigid PCBs, dealing with FPCs and rigid-flex boards has been challenging, yet has make me very interested on gaining more knowledge of this technology. With that, I want to share some of the things I have learned for this mature, yet continuously evolving PCB solution.
Know the End-Product Application
It is important that you know if the application you intend for the product suits having the board flex, rigid-flex or rigid PCBs. This is critical as some application can be solved using a rigid PCB or a flexible PCB rather than having a rigid-flex board. Having decided what direction to take will dictate the cost as well, as rigid PCBs and flex PCBs is often times cheaper than a rigid-flex PCB. Knowing what you need and how you intend to use the boards is the first step.
Getting the Fabricator Involved
Communication is key during the design of a FPC/rigid-flex board. Most of the times, designer ignore the importance of getting the involvement of the fabricator on the design stage of the product. They want to save time by not engaging discussions with the fabricator and rely on their knowledge of the flexible PCB concept. However, this process proves to be vital, as this puts the product one step from being a realized board. By involving the fabricator, you will know the limitations of their process, perform risk assessment and increase the productivity by streamlining the next set of steps to be taken. Not only that you will be able to lessen the turnaround time of EQs, this will also ensure that possible showstoppers are addressed as early as the design stage.
Since the most useful property of flex PCB is its dynamic flexibility, the designer should be able to scrutinize the design for areas where stress is mostly concentrated. Stress concentration features are the predominant cause of mechanical failures in flex PCBs (i.e: broken conductor on the flexible area, torn insulating material, etc.). The use of platforms with stress analysis capability is helpful to know the points in your design where the most stress will occur, giving you the ability to address it as early as the design stage.
These are just some of the things we think a PCB designer should consider when engaging to flex or rigid-flex PCBs. An in-depth knowledge of this technology is also a factor on designing a working prototype.
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