Mark Finstad

Part two of how to design a flex circuit.

Ed.: The first part of this series was published in March 2014.

Flex PCB routing shares many of design rules as rigid PCB routing, with a few extra rules that apply specifically to areas of the circuit that will be flexing. The “extra” rules are:

Stress concentration points. I cannot overstress (no pun intended) the importance of reviewing the design for stress concentration features in flexing zones. The construction of the circuit and conductor features should remain constant and unchanged in and around an area that will be bent. The vast majority of flex circuit failures I have seen were caused by features that elevated mechanical stresses in a small focused area or point. Many things can cause this; here are some of the most common to keep out of a bending or flexing area.


Once again, your flex circuit manufacturer may not be able to tell you everything that will work, but I can guarantee that they will know what does not work (those experiences are hard to forget). Believe me, they want your design to work as much as you do.

Mark Finstad is a senior application engineer at Flexible Circuit Technologies (flexiblecircuit.com); This email address is being protected from spambots. You need JavaScript enabled to view it.. He and co-“Flexpert” Mark Verbrugge from PICA Manufacturing Solutions (This email address is being protected from spambots. You need JavaScript enabled to view it.) welcome your questions.

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