Improvement in moisture resistance of thin SiP utilizing the plasma treatment of resin surface

In downsizing the SiP (System in Package) thickness, moisture resistance reliability has been a serious problem, because of the weak adhesion property of the interface between the interposer and mold resin [1]. Also, the SiP requires more heat resistance because of the high reflow temperature in the lead free solder process. In this work, we have improved the adhesion property with a new plasma treatment technology. It is Argon or Argon-Oxygen mixture Plasma treatment of PSR (Photo Solder Resist) surface composed of Cardo polymer which has excellent heat resistance compared to the conventional PSR. The plasma treatment improved the adhesion property of the interface between this PSR and mold resin. As a result, the moisture resistance reliability of the module was improved. SEM (Scanning electron microscope) images of the PSR surface treated with plasma showed the generation of projections caused the anchor effect. XPS (X-ray photoelectron spectroscopy) spectra indicated that the plasma treatment changed the chemical combined states of the PSR surface. From these results, both the anchor effect and the chemical bond effect increased the adhesion property at the PSR/mold resin interface. Therefore, with the adhesion improvement from the plasma treatment process and by adopting a highly heat resistant Cardo polymer PSR it is possible to miniaturize a fine moisture-resistant and heat-resistant SiP.