PCB News - Introduction to flexible circuit boards

Introduction to flexible circuit boards

Early flexible printed circuit boards(hereinafter referred to as flexible boards) were mainly used in the fields of small or thin electronic mechanisms and connections between rigid boards. In the late 1970s, it was gradually applied to electronic information products such as computers, cameras, printers, car stereos, and hard disk drives. At present, the Japanese FPC application market is still dominated by consumer electronic products, while the US has gradually shifted from past military use to consumer use for people's livelihood.

The functions of the soft board can be divided into four types: Lead Line, Printed Circuit, Connector, and Integration of Function. The use covers computers and computer peripherals. Scope of systems, consumer electrical appliances and automobiles.

. COPPER Clad Laminater (CCL)

CU (Copper foil): ED and RA copper foil: Cu copper layer, copper skin is divided into RA, Rolled Annealed Copper and ED, Electrodeposited. The two have different characteristics due to different manufacturing principles. ED copper is low in cost but easy to manufacture. When making Bend or Driver, the copper surface is easy to break. RA copper has high manufacturing cost but good flexibility, so the FPC copper foil is mainly RA copper.

A (Adhesive): Acrylic and epoxy resin thermosetting adhesive:

Adhesive is two major systems: Acrylic and Mo Epoxy.

PI (Kapton) Polyimide (polyimide film):

PI is the abbreviation of Polyimide. In DuPont called Kapton, the unit of thickness is 1/1000 inch lmil. The characteristics are thin, high temperature resistance, strong chemical resistance, and good electrical insulation. Now the FPC insulation layer is welded

Ask where the brothers and feet Kapton.

. Features:

1. It is highly flexible and can be wired in three dimensions, and the shape can be changed according to space constraints.

2. High and low temperature resistance, flame resistance.

3. It can be folded without affecting the signal transmission function and can prevent electrostatic interference.

4. Stable chemical changes, high stability and reliability.

5. Facilitate the design of related products, reduce assembly man-hours and errors, and increase the service life of related products.

6. The volume of the application product is reduced, the weight is greatly reduced, the function is increased, and the cost is reduced.

Polyimide Resin

Polyimide resin is represented by polypyromellitic acid imide produced by the reaction of an oxygen-containing layer base and anhydrous pyromellitic acid, and is a general term for a heat-resistant resin with five negative imine rings.

Imidine resin is the most versatile of all high heat-resistant polymers. It can create various sensors such as polypyromellitic acid imide and other kinds of sensors, and it can also make it multifunctional, so its use is so wide.

Although the use of polypyromellitic acid imine is greatly restricted because it does not melt, it has been successfully developed and only needs to sacrifice its heat resistance slightly to create a polyamide that can be melted or melted with a solvent. After the amine, its use soon became widespread. In the case of polyimide resins for printed circuit boards, in addition to heat resistance, attention must be paid to issues such as formability, mechanical properties, dimensional stability, electrical properties, and cost. Therefore, there are many restrictions on its use. For these reasons, only a few addition polymerization type thermosetting polyimides are currently used for multi-layer printed circuit boards with more than ten layers. However, it is believed that the amount will continue to increase in the future, as shown in the table below. In addition, the bottom protective film of the flexible circuit board is still polypyromellitic acid imide currently used.

The conductors used in printed circuit boards are made of thin foil-like copper.

It is the so-called copper foil. According to its manufacturing method, it can be divided into electrolytic copper foil and rolled copper foil.