What Is a Multilayer Flexible Printed Circuit (FPC)?

Jan 28, 2022

Circuits are the building blocks for nearly all electronic devices. A circuit, of course, is a controlled electrical path. It consists of a loop that begins, ends and repeats at a power source. A closed circuit means this loop is complete. An open circuit, on the other hand, means this loop is incomplete or broken.

There are rigid circuits and flexible printed circuits (FPCs). Rigid circuits are stiff, whereas FPCs are able to flex. While all FPCs are flexible, some of them feature more conductor layers than others. Multilayer FPCs fall under this category. What is a multilayer FPC exactly, and how does it differ from other types of FPCs?

Overview of Multilayer FPCs

A multilayer FPC is a type of FPC with at least three conductor layers. Conductor layers, of course, are layers of material that are electrically conductive. They often feature conductive traces. As electricity travels through the device, the conductive layers will determine its route.

Some FPCs only have a single conductor layer. Other FPCs have two or more conductor layers. The term “multilayer FPC” refers to any FPC with at least three conductor layers.

All FPCs have conductor layers. The conductor layers serve as the path for electricity. Multilayer FPCs, though, are designed with at least three conductor layers.

Other Types of FPCs

There are several other types of FPCs. One of the most common types of FPCs is single-sided. A single-sided FPC is essentially a single-layer FPC. It only features one conductor layer. The conductor layer is typically made of a conductive metal or a polymer that contains a conductive metal.

There are also double-sided FPCs. As you may have guessed, double-sided FPCs have two conductor layers. Some double-sided FPCs have plated through holes, whereas others do not. Regardless, all double-sided FPCs have two conductor layers.

When researching FPCs, you may come across rigid-flex. Rigid-flex FPCs are characterized by their hybrid design. They feature characteristics of both FPCs and traditional, rigid circuits. Rigid-flex FPCs feature substrates of both FPCs and rigid circuits that are laminated together. Most rigid-flex FPCs feature at least three conductor layers.

You can find FPCs in different classes. Class 1 FPCs undergo the least amount of inspection, whereas class 3 FPCs undergo the most amount of inspection. Additionally, you can find them in different types. Multilayer is a type of FPC that features at least three conductor layers. Other common types of FPCs include single-sided, double-sided and rigid-flex.

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