Control method of FPC material ups and downs

FPC (Flexible Printed Circuit) refers to flexible circuit boards, also known as flexible printed circuit boards, flexible circuit boards or flexible boards. This circuit board has the advantages of high wiring density, light weight, and thin thickness. Widely used in mobile phones, notebook computers, PDAs, digital video cameras, LCM and many other products. In recent years, the PCB manufacturing process has developed rapidly, and the industry has set higher requirements for FPC. Precision PITCH is the main breakthrough direction of FPC in the future. Dimensional stability and refinement have also caused the rise in FPC costs. How to control the contradiction between the two has become a major breakthrough in the control of FPC material expansion and contraction during the production process. Below we will briefly explain how to control and the main points of control.

I. Design

1. Circuit: Because FPC will swell due to temperature and pressure during ACF crimping, it is necessary to consider the expansion rate of the crimping finger and perform pre-compensation treatment when designing the circuit initially;

2. Typesetting: The design products should be evenly and symmetrically distributed throughout the typesetting. The minimum interval between each two PCS products should be more than 2MM. The copper-free part and the via-dense part should be staggered as much as possible. These two parts are in the subsequent manufacturing process. There are two important aspects affected by the expansion and contraction of materials.

3. Material selection: The glue of the cover film should not be thinner than the thickness of the copper foil too much, so as to avoid the deformation of the product due to insufficient filling of the glue during lamination, and the thickness and whether the glue is evenly distributed is the culprit for the expansion and contraction of FPC materials.

4. Process design: The cover film should cover all copper foil parts as much as possible. It is not recommended to stick the cover film to avoid uneven force during pressing. The PI reinforced adhesive surface adhesive above 5MIL should not be too large. After the cover film is pressed and baked, PI-reinforced laminating is performed.

Second, material storage

I believe the importance of material storage. I need not say more. It must be stored strictly in accordance with the conditions provided by the material supplier.

Third, manufacturing

1. Drilling: It is best to add baking before drilling to reduce the increase and decrease of the substrate during subsequent processing due to the high moisture content in the substrate.

2. In electroplating: it should be made with short-sided plywood, which can reduce the deformation caused by the water stress caused by the swing. The swing can be reduced during plating to minimize the amplitude of the swing. The number of plywood also has a certain relationship. The number of asymmetrical plywood , Can be assisted by other side materials; when plating, the lower tank is charged to avoid the sudden high current impact on the board, so as not to adversely affect the plating of the board.

3. Squeezing: The traditional presses are larger and smaller than the fast presses. The traditional presses are cured at a constant temperature and the fast presses are cured by heat. Therefore, the change of the control glue of the traditional press must be stable. Quite important part.

4. Baking: For fast-pressed products, baking is a very important part. The baking conditions must be such that the glue is completely cured, otherwise there will be endless problems after subsequent production or use; the baking temperature curve is generally gradually raised to The temperature at which the glue is completely melted. Continue this temperature until the glue is completely solidified, and then gradually cool down.

5. During the production process, try to maintain the stability of temperature and humidity in all stations, and transfer between stations, especially those that need to be produced externally, and the conditions for product storage need special attention.

Fourth, packaging

Of course, the completion of the product does not mean that everything is fine. It is necessary to ensure that customers do not have any problems in subsequent use. In terms of packaging, it is best to bake first, dry the water absorbed by the substrate during the manufacturing process, and then use it. Vacuum packaged and instruct the customer on how to save.

Therefore, to ensure the quality of this kind of products, it is necessary to strictly follow the specific requirements from material preservation → control of each process → packaging → customers before use.