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High-Frequency Flexible Circuits

Flexible circuits, as a family of products, come in many variations. There are the more traditional flex circuits that are low layer-count, very flexible, used in dynamic motion applications and static scenarios. The static case is generally an application of a one-time bend, where the circuit is formed to a shape in the assembly and then it never has to flex again. In dynamic applications, the circuit must continually flex during the product’s lifecycle, such as a read-write flex circuit inside of a hard disk drive.

Rigid-flex circuits have the ability to join multilayer rigid PCB technology with flexible circuits. Think of this concept as having flex circuit layers built into a multilayer PCB. The rigid areas are typically a FR-4 type material and the flex layers are polyimide-based materials. Rigid-flex offers the best of both worlds but can be problematic for manufacturing and reliability issues. Over the years, manufacturers of rigid-flex have fine-tuned the technology to where the manufacturing and reliability issues are well understood. Now, rigid-flex can be made effectively and with very good reliability.

John Coonrod of Roger Corporation discusses the pros and cons of materials for your high-frequency flexible circuits.

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This article originally appeared in the June 2013 issue of The PCB Design Magazine.