Direct bonding of copper foil and liquid crystal polymer by laser etching and welding

Abstract

The reported laser welding of dissimilar materials (metal and plastic) mostly focuses on the optimization of parameters and process, the process is complex and the cost is high. Liquid crystal polymer (LCP) has attracted much attention due to its excellent electrical properties. With the rapid development of information technology, 5G high-frequency communication is gradually emerging. At the same time, there are many problems to be solved, such as the serious skin effect caused by the large copper foil surface roughness and large energy consumption. Therefore, it is urgent to solve this problem for the development of communication technology. Nowadays, the manufacturing process of a two-layer flexible copper clad laminate is not only complex, but also high production cost. In order to try a new manufacturing method and balance the copper foil surface roughness and the bonding strength between the copper foil and LCP, this study proposes a laser integrated manufacturing method for two-layer flexible copper clad laminates, including LCP laser etching, copper foil laser etching and laser welding. We fabricated regular microstructures on the copper foil surface by laser etching, used ultraviolet laser to irradiate the LCP surface, the copper foil and LCP were welded together by laser conduction welding. The surface roughness of the sample was measured by atomic force microscope, the surface morphology was observed by optical microscope, and the bonding strength and peel strength between the etched copper foil and LCP were tested by micro-tensile test. The welding sample bonding strength obtained by this way can reach the ultimate tensile strength of the copper foil, and the peel strength can reach 682.78 N/m, which is close to the reported peel strength obtained by other methods. High-resolution field emission scanning electron microscope and X-ray photoelectron spectrometer were used to reveal the bonding mechanism of the samples. The integrated method is easier to realize automation for the actual production process. Therefore, we have verified that the two-layer flexible copper clad laminate with high bonding strength and peel strength can be prepared by laser processing.