Adhesion characteristics of aromatic thermosetting copolyester and glass fiber laminates with copper foils for improved circuit boards

Copper foils are the vital elements used in microelectronic devices. Adequate adhesion between copper foils to various substrates, such as Si, SiO₂ and polyimide, is crucial to functional electronic devices. Liquid-crystalline polymers (LCPs) can be used as substrates for these modules as well as the adhesive to copper foils. The adhesion between aromatic thermosetting copolyester (ATSP)/fiberglass fabric (GF) laminates and copper foils was characterized by peel strength tests. It was found that ATSP/GF laminates with copper foil using ATSP oligomers as adhesive showed a highest average peel strength of 711 N · m⁻¹. Scanning electron microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) showed an excellent bond between the composite and the copper foil interface. Failure occurred between the backside of the copper foil and the ATSP/GF laminates in the peeling test and the mechanism is discussed. Thermogravimetic analyzer (TGA) indicated a thermal stability up to 371°C for ATSP/GF composite substrate and a glass transition temperature of over 400°C as determined by peak in tan δ during Dynamic Mechanical Analysis (DMA).