Thermal stability of PCB materials

　　The content of nitrogen and phosphorus in halogen-free plate is higher than that of common halogen-based material, so the monomer molecular weight and Tg value are increased. In the case of heat, the molecular movement capacity will be lower than that of conventional epoxy resins, so the coefficient of thermal expansion of halogen-free materials is relatively small. Compared with halogen-free plate, halogen-free plate has more advantages, and halogen-free plate replaces halogen-free plate is also the trend of The Times.

　　Five, the production of halogen-free PCB experience

　　1 ply

　　Laminating parameters may vary from company to company. Take the above mentioned Sheng benefit substrate and PP multi-layer board, in order to ensure the full flow of resin, so that the binding force is good, the requirements of low plate heating rate (1.0-1.5℃ / min) and multi-stage pressure coordination, and in the high temperature stage requires a longer time, 180℃ to maintain more than 50 minutes. The following is a recommended set of platen program Settings and the actual plate temperature. The bonding force between the copper foil and the substrate is 1.ON/mm, and there is no stratification and bubble phenomenon in the plate after six thermal shocks.

　　2. Drilling machinability

　　The drilling condition is an important parameter, which directly affects the quality of the hole wall in the process of PCB. Since the P and N series functional groups increase the molecular weight of halogen-free copper clad plate and enhance the rigidity of molecular bonds, the rigidity of the material is also enhanced. At the same time, the Tg point of halogen-free materials is generally higher than that of ordinary copper clad plate, so the drilling effect of ordinary FR-4 drilling parameters is generally not satisfactory. When drilling halogen free plate, it is necessary to make some adjustments under normal drilling conditions.