Rigid And Flexible Substrates For Printed Circuit Boards

1. Phenolic paper laminate. Phenolic paper laminates can be divided into different grades. Most grades can be used at temperatures as high as 70~105 ℃. Too high temperatures may lead to some performance degradation (depending on the grade and thickness of the substrate), and overheating may cause carbonization. In the affected areas, the insulation resistance may drop to a very low value. Such a heat source is a heat generating element. In the normal temperature range, the substrate may be seriously blackened (sunlight can also blacken the substrate, but will not cause changes in material properties). When placed in a high humidity environment, the insulation resistance of the substrate will be greatly reduced. However, when the humidity is reduced, the insulation resistance will increase.

2. Epoxy paper laminate. Compared with phenolic paper laminate, epoxy paper laminate has greater improvement in both electrical and non electrical properties, and has better machinability and mechanical properties. According to the thickness of the material, its use temperature can reach 90 ~ 110 ℃.

3. Polyester glass felt laminate. The mechanical properties of polyester glass felt laminates are lower than those of glass cloth based materials, but higher than those of paper based materials. They have good impact resistance and electrical properties, and can be used in a wide frequency range. They can maintain good insulation performance even in high humidity environments. Its operating temperature can reach 100~105 ℃.

4. Epoxy glass cloth laminate. The mechanical properties of epoxy glass cloth laminate are higher than those of paper-based materials, especially the bending strength, impact resistance, warpage and welding thermal shock resistance are better than those of paper-based materials. The electrical performance of this material is also very good, the use temperature can reach 130 ℃, and it is less affected by harsh environment (humidity).

Copper clad substrate for flexible printed circuit board

1. Polyester film. The most common property of polyester film is flexibility, which is characterized by the formation of contractible coils when heated. If proper adhesive is used, this material can be used in the range of 80-130 ℃. Special attention shall be paid to the fact that this material is easy to soften and deform at the welding temperature, and it can still maintain its good electrical performance in high humidity environment.

2. Polyimide film. Polyimide film has good flexibility, and can remove absorbed moisture through preheating treatment to ensure safe welding. The general adhesive polyimide film can work continuously at temperatures up to 150 ℃, the special capacitive polyimide film using fluorinated ethylene propylene as the intermediate adhesive film can be used at 250 ℃, and the special purpose polyimide film without adhesive can be used at higher temperatures. Polyimide film has excellent electrical properties, but it may absorb moisture and affect the performance.

3. Fluorinated ethylene propylene film. FEP film is usually combined with polyimide or glass cloth to make a laminate, which has good flexibility and stability under the welding temperature of no more than 250 ℃. It can also be used as a non supporting material. FEP film is a thermoplastic material with a melting temperature of about 290 ℃, which has good moisture resistance, acid resistance, alkali resistance and organic solvent resistance. Its main disadvantage is that the conductive pattern is easy to move at the lamination temperature during lamination.