FPC, also known as the soft circuit, is a highly reliable, flexible printed circuit made of poly-lipid films or polyimide as a base material. This kind of circuit can bend, fold, light weight, small size, good heat dissipation, easy installation, breaking through the traditional technology concept of interconnection. Flexible circuit, as a kind of new product with thin, light, flex and so on, FPC can meet the demand of three-dimensional group, which is widely applied in the electronic and communication industry. Mainly used in computer, car audio, cassette recorders, printers, scanners, CD/DVD machines and other electronic and communications products.
FPC: Generally referred to as flexible circuit boards.
Flexible PCB is a highly reliable and excellent flexible printed circuit board, which is made of polyimide or polyester film as base material. With high density of wiring, light weight, thin thickness, FPC good bending characteristics.
⒈ Short: Short assembly hours.
All lines are configured to complete. FPC Eliminates the connection work of redundant lines.
⒉ Small: The volume is smaller than PCB.
Can effectively reduce the volume of the product.
⒊ Light: Weight is lighter than PCB.
Can reduce the weight of the final product.
4 thin: thickness is thinner than PCB.
It can improve the softness. To strengthen the assembly of three degree space within the limited space.
The basic composition of FPC is the matrix membrane or heat-resistant resin which forms the substrate, followed by copper clad laminate and protective layer material.
The FPC substrate material from the initial polyimide membrane to the heat-resistant film can be welded. FPC The first generation polyimide membrane has the high hygroscopicity and the thermal expansion coefficient and so on, so people adopted the second generation polyimide material for high-density circuit.
So far, several kinds of FPC have been developed to replace the first generation polyimide membrane heat-resistant film. However, in the next 10 years, FPC it is considered that the position of the polyimide resin as the main material of FPC will not change. In addition, with the high performance of FPC, the material shape of polyimide resin will be changed, and the polyimide resin with new function must be developed.
Manufacturing process of FPC
The FPC manufacturing process has so far been processed using a reduction method (etching), usually with CCL as the starting material, using lithography to form an anticorrosive layer, and etching to remove not part of the copper surface to form a circuit conductor. Due to such problems as side erosion, FPC etching methods exist in micro-circuit processing restrictions.
It is considered that semi-additive is an effective method based on the difficulty of machining and difficult to maintain the high qualified rate micro circuit. The semi-additive process takes polyimide membrane as the starting material, first casting (coating) The liquid polyimide resin on the appropriate carrier to form polyimide membrane. Then, using sputtering method to form the dendrite layer on the Polyimide matrix film, FPC and then using lithography method to form the anti corrosion layer graphics of the inverse graphics of the circuit, known as the resistant coating. In the blank part electroplating forms the conductor circuit. Then remove the corrosion layer and the unnecessary planting layer to form the first layer of circuit.
A photosensitive polyimide resin is coated on the first layer of the circuit, which is formed by photolithography to form a hole, a protective layer, or a layer of insulation used in the second layer of the circuit, FPC and then sputtered to form a crystalline layer as a substrate conductive layer of the second layer circuit. Repeat the above process, can form multilayer circuit. This kind of semi additive can be used to process the Super micro circuit with the pitch of 5gm and the conduction hole as LOPM. The key of fabricating super micro circuit by using semi-additive is the performance of photosensitive polyimide resin used as insulating layer.