Adhesion mechanism between mold resin and sputtered copper for electromagnetic wave shield packages

As mobile information and communication terminals become smaller and more sophisticated, electronic device manufacturers are increasingly demanding that electromagnetic interference measures be added to individual electronic components assembled on high-density printed circuit boards. Therefore, semiconductor device products require a process for forming electromagnetic wave shielding film. Sputtered film deposition methods with stable processes are increasingly used for the formation of shield films. Although Cu is often used as the shield film, there has been little discussion of the adhesion mechanism with the mold resin used in semiconductor device products. In this work, Cu film was sputter-deposited onto mold resin under a variety of conditions, and the factors that influence adhesion were investigated. The results show that it is necessary to carry out degassing in the sputtering equipment at temperatures higher than 180°C, above which the amount of degassing increases. No clear relationship was found between surface roughness and adhesion. The exposure ratio of the SiO2 filler was found to be related to adhesion. The mechanism of adhesion between the mold resin and sputter-deposited Cu film was considered from the experimental results, and the following models are proposed. Plasma etching exposes SiO2 filler at the surface of the mold resin and increases the surface free energy. The surface becomes activated, which is thought to create adhesion between the Cu and SiO2 filler.