Research on temperature-assisted laser transmission welding of copper foil and polyethylene terephthalate

Copper foil is widely used in printed circuit board because of its good conductivity, especially in flexible printed circuit board. A traditional two-layer flexible copper clad laminate avoids introduction of an additional adhesive, its application range is improved, but its peel strength is low. Laser, as an efficient and clean energy, has great potential application value in this field. Based on the research of parameters of laser transmission welding copper foil and polyethylene terephthalate (PET), to prepare a two-layer flexible copper clad plate and improve the bonding strength of welding joints in laser welding, this study proposes to change the surface roughness of the copper foil and preheat the weldment in the welding process. The bonding properties of the welded joint were tested by a micro-tensile test bench. Through the study of laser parameters, a welding speed of 300 mm/min was used to explore the surface roughness of the copper foil, it was found that the overall welding effect was best when the surface roughness of the copper foil was 400 nm. The effect of the preheating temperature on the bonding properties of weldments was studied by preheating samples at different temperatures. A high-speed camera was used to record the instantaneous tensile state of the welding sample, the surface roughness of the debonding sample under different conditions was measured by atomic force microscope. The interface morphology of the sample was characterized by optical microscope, X-ray photoelectron spectrometer, and high-resolution field emission scanning electron microscope. The bonding mechanism was revealed, and the reason for the strength improvement of the welding joint was discussed. In view of the research results of the PET/copper foil high-strength bonding in this paper, it shows that the laser welding technology has an important application prospect in the production of a two-layer flexible copper clad laminate.