Epec's Blog | Electronics Manufacturing Solutions

This blog post is intended to reinforce the design support we offer at Epec for our flex and rigid-flex PCBs. Technical design and engineering is one of our core foundations which allow us to best help our customers meet their product requirements. Within the post, we'll cover design areas that require special consideration.

Flexible PCBs use one of two polyimide flex core constructions: adhesive-based or adhesiveless. The difference lies in how copper is bonded to the polyimide core, which directly affects thickness, flexibility, thermal behavior, reliability, and cost. Selecting the correct construction requires balancing electrical, mechanical, and environmental design requirements.

For rigid-flex printed circuit boards (PCBs), the space joining rigid material to flex material (Transition Zone) sometimes contains imperfections that, although acceptable, could impact effectiveness of the final part. Transition zone imperfections can include any of the following:

Selecting the appropriate copper weight for a flexible PCB requires balancing both electrical performance and mechanical flexibility. Because copper is the stiffest component within a flexible circuit, it has a significant influence on the circuit's ability to bend reliably while still meeting electrical requirements.

A flexible circuit coverlay is a polyimide-based protective layer laminated over exposed circuitry in a flex PCB. It performs the same role as solder mask on rigid circuit boards, while maintaining the flexibility and durability required for bendable designs. Proper material selection, thickness, and opening design are critical to ensuring both protection and functionality.

Flex circuits provide design options that rigid printed circuit boards cannot. Whether used in new designs or to improve existing assemblies, flexible printed circuits enable tighter packaging, improved system reliability, broader electrical capabilities, and long‑term cost reductions.