Adhesion Mechanism between Mold Resin and Sputtered Stainless Steel Ground Films for Electromagnetic Wave Shield Packages

Abstract

The number of radio systems used for global communications or advanced features is increasing in electronic devices such as smart phones. As mobile information and telecommunications terminals are miniaturized and advanced features are added by manufacturers, measures to prevent electromagnetic interference among electronic components on high-density mounting boards are becoming increasingly important. Therefore, it is crucial to develop methods for forming electromagnetic wave shield films in semiconductor devices. Stable sputtering processes are increasingly used for the deposition of shield films. Although metal is often used as a shield film, the mechanism of the adhesion of the sputtered film to the mold resin in semiconductor devices has not been discussed. In this work, sputtering was used to deposit a stainless steel film as a ground film for a copper wave shield film and the factors that affected the adhesion of the stainless steel film to the mold resin were investigated. For the copper film with no ground film, adhesion decreased as the resin filler content decreased. For the copper/stainless steel film, adhesion remained high as the filler content of the mold resin decreased. The argon and nitrogen plasma etching formed carbides and nitrides at the interface of the mold resin and a stainless steel film, whereas argon etching formed carbides. Based on the experimental results, we proposed that the adhesion between the stainless steel film and the mold resin mainly arose from the carbides and nitrides reacting with iron and chromium in the stainless steel film.