Chapter 8 – Guide to Reliable Static and Dynamic Flexing
By Werner Engelmaier
Flexible circuit materials have an inherent ability to flexurally deform. One significant benefit is that the materials used to fabricate flexible circuits permit the roll-to-roll manufacturing processes for large volume production. It is thus important for designers to understand and consider the flexibility limitations of flex circuits, not only for the final product geometry and functional life, but also for all prior manufacturing, assembly, adjustment and repair procedures to avoid yield problems and functional life failures.
Chapter 8 provides design necessities in terms of conductor layout, flex circuit stack-up and material selection, as well as factors including: assembly, adjustment and repair procedures; final circuit geometry; and number of flexures during functional life. The chapter provides the necessary formulas and factors needed to determine strain, allowable strain range, applied strain vs. available ductility, distribution of applied strain and distribution of available ductility.