China New Product Low Cost Pcb Prototype - 4 Layer ENIG SF302+FR4 Rigid-Flex PCB – Huihe

Points For Attention In The Design Of Rigid Flexible Combination Zone

1.The line should transition smoothly, and the direction of the line should be perpendicular to the bending direction.

2.The conductor shall be evenly distributed throughout the bending zone.

3.The width of the conductor shall be maximized throughout the bending zone.

4.PTH design should not be used in rigid flexible transition zone.

5.Bending radius of bending zone of rigid flexible PCB

Material Of Flexible PCB

Everyone is familiar with Rigid materials, and FR4 types of materials are often used. However, many requirements need to be taken into account for the rigid flexible PCB materials. Need to be suitable for adhesion, good heat resistance, in order to ensure that the rigid flexural bonding part of the same degree of expansion after heating without deformation. General manufacturers use resin series of rigid PCB materials.

For flexible materials, choose a substrate and cover film with smaller size expansion and contraction. Generally use the hard PI manufacturing materials, but also direct use of non-adhesive substrate for production. The flex materials are as follows:

Base Material: FCCL(Flexible Copper Clad Laminate)

PI. Polymide: Kapton (12.5 um / 20 um / 25 um / 50 um / 75um). Good flexibility, high temperature resistance (long-term use temperature is 260°C, short term 400°C), high moisture absorption, good electrical and mechanical characteristics, good tear resistance. Good weather resistance, chemical resistance and flame retardancy. Polyester imide (PI) is the most widely used.PET. Polyester (25 um / 50 um / 75um). Cheap, good flexibility and tear resistance. Good mechanical and electrical properties such as tensile strength, good water resistance and hygroscopicity. But after being heated, the shrinkage rate is large and the high temperature resistance is poor. Not suitable for high temperature soldering, melting point 250°C, less used

Covering Membrane

The main role of the covering film is to protect the circuit, prevent the circuit from moisture, pollution and welding.The Conductive Layer can be Rolled Annealed Copper, Electrodeposited Copper and Silver Ink. The crystal structure of electrolytic copper is rough, which is not conducive to fine line yield. Calendered copper crystal structure is smooth, but the adhesion with the base film is poor. Can be distinguished from the appearance of spot and rolling copper foil. Electrolytic copper foil is copper red, calendering copper foil is gray white.Additional Materials &Stiffeners: That is pressed in part of the flex PCB for welding components or adding stiffeners for installation. Reinforcement film available FR4, resin plate, pressure sensitive adhesive, steel sheet aluminum sheet reinforcement, etc.

Non-flow/Low Flow glue semi-cured sheet (Low Flow PP). Rigid and Flex connections are used for Rigid flex PCB, usually very thin PP.