Flexible Printed Circuit (FPC) has some advantages, such as high-density wiring, light weight, and thin thickness. It is widely used in many products, such as mobile phones, laptops, PDAs, digital cameras, LCMs, etc..

 

In recent years, PCB manufacturing technology has developed rapidly. People put forward higher requirements for FPC. The stability and refinement of dimensions have led to an increase in the cost. We want to control expansion and contraction of FPC materials during the production process. Let's talk something about it.

 

1. Design

 

Circuit

 

Since FPC will expand due to temperature and pressure when ACF is crimped, the expansion rate must be considered when designing at first. You should do pre-compensation processing.

 

Layout

 

An evenly symmetrical layout is best. The minimum spacing between every two PCS components should be kept above 2mm. Copper-free parts and parts with dense vias should be staggered as much as possible. These two parts are important things that are affected by material expansion and contraction in subsequent manufacturing process.

 

Adhesive

 

The adhesive of the covering film cannot be much thinner than the copper foil, so as to avoid insufficient adhesive filling during lamination. Otherwise, it results in deformation. The thickness of adhesive and whether it is evenly distributed are reasons of expansion and contraction of FPC materials.

 

Process design

 

The covering film should cover all copper foil. It is not recommended to stick the covering film in strips to avoid uneven force during pressing. The covering film needs to be pressed and dried before PI reinforcement.

 

2. Material storage

 

It's important. Materials must be stored strictly in accordance with the conditions provided by the supplier. If they need to be refrigerated, then do that.

 

3. Manufacturing

 

Drilling

 

It is better to dry before drilling, to reduce expansion and contraction of materials during subsequent processing due to high moisture in them.

 

Electroplating

 

The short side should be fixed for operation, which can reduce deformation caused by water stress generated by the swing.

 

The swing amplitude should be reduced as much as possible during electroplating. Take care of the number of splints.

 

When electroplating, the tank should be charged to avoid sudden high current impact on the board.

 

Pressing

 

Traditional press machine is smaller than fast press machine. Traditional press machine is constant temperature curing, and fast press machine is heat curing. Therefore, traditional press machine must control the change of glue stably. Of course, the lamination layout is also very important.

 

Drying

 

For quick-pressed products, drying is important. The drying conditions must be such that the glue is completely cured. Otherwise, there will be endless troubles in subsequent production or use. The drying temperature gradually increases to the point at which the glue is completely melted, then maintain this temperature until the glue is completely cured, and then gradually cool down.

 

Temperature and humidity

 

During the production process, try to maintain the stability of temperature and humidity in all workstations. When transferring between workstations, pay attention to the storage conditions.

 

4. Packaging

 

To ensure that no problems occur during the use of FPC, it is best to dry it before packaging. That is to dry out the moisture absorbed by the base material during the manufacturing process. Vacuum packaging is necessary. You should know how to store it right.