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Understanding FPC flexible circuit boards

xinstMay 20, 2020

FPC FPC flexible circuit board: Flexible Printed Circuit in English, its Chinese meaning is flexible printed circuit board, referred to as flexible board. It is made of conductive circuit patterns on the surface of a flexible substrate using optical imaging pattern transfer and etching processes. The surface and inner layers of double-sided and multi-layer circuit boards are electrically connected to each other through metallized holes The surface of the circuit pattern is protected and insulated with PI and glue layer.

Mainly divided into single panel, hollow panel, double panel, multi-layer panel, soft and hard combination board.

FPC flexible circuit board
FPC flexible circuit board

Features of FPC flexible circuit board

Short: short assembly hours

All lines are configured, eliminating the need to connect redundant cables;

Small: smaller than PCB (hard board)

Can effectively reduce the product volume and increase the convenience of carrying;

Light: Lighter than PCB (hard board)

Can reduce the weight of the final product;

Thin: thinner than PCB (hard board)

It can improve the softness and strengthen the assembly of three-dimensional space in the limited space.

Advantages of flexible circuit boards

Flexible printed circuit boards are printed circuits made of flexible insulating substrates, and have many advantages that rigid printed circuit boards do not have:

It can be freely bent, wound and folded, can be arranged arbitrarily according to the space layout requirements, and can be arbitrarily moved and stretched in three dimensions, so as to achieve the integration of component assembly and wire connection;

The use of FPC can greatly reduce the volume and weight of electronic products, which is suitable for the development of electronic products in the direction of high density, miniaturization and high reliability. Therefore, FPC has been widely used in aerospace, military, mobile communications, laptop computers, computer peripherals, PDAs, digital cameras and other fields or products;

FPC also has the advantages of good heat dissipation and solderability, easy assembly, and low overall cost. The design of the combination of soft and hard also makes up for the slight deficiency of the flexible substrate in the component carrying capacity.

Other auxiliary materials

(1) Pure glue: This adhesive film is a thermosetting acrylic adhesive film composed of protective paper / release film and a layer of adhesive. It is mainly used for layered boards, soft and hard bonding boards, and FR-4 / steel sheet reinforcement board, play a bonding role.

(2) Electromagnetic protective film: pasted on the board to play a shielding role.

(3) Pure copper foil: only composed of copper foil, mainly used for hollow board production.


With plastic substrate

There are three main components of the adhesive base material: copper foil, glue, and PI. There are two types of single-sided base material and double-sided base material. Double-sided substrate.

Non-glue substrate

The non-adhesive substrate is a substrate without an adhesive layer, which is less than the ordinary adhesive substrate, the middle adhesive layer is only composed of copper foil and PI, which is thinner than the adhesive substrate , Better dimensional stability, higher heat resistance, higher bending resistance, better chemical resistance and other advantages, has now been widely used.

Copper foil: At present, the thickness of commonly used copper foil has the following specifications, 1OZ, 1 / 2OZ, 1 / 3OZ, now thinner copper foil with a thickness of 1 / 4OZ, but currently this kind of material is already used in China (Line width and distance are 0.05MM and below) products. With the increasing requirements of customers, materials of this specification will be widely used in the future.

Cover film

It is mainly composed of three parts: release paper, glue, and PI, and only two parts, glue and PI, are left on the product. The release paper will be torn off during the production process and no longer used (its role protects the foreign matter on the glue ).

Types of FPC

There are 6 types of FPC types:

(1) Single panel: only one side has a line.

(2) Double panel: There are lines on both sides.

(3) Hollow board: also known as window board (finger window).

(4) Layered board: two lines (separate).

(5) Multi-layer board: two or more lines.

(6) Soft and hard board: a product combining soft board and hard board.

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