Yoshiko Tatsuta

Wafer and/or chip bonding adhesives for 3D package

For 3D package application the demanded feature of chip bonding adhesive was discussed and the material was developed, which was wafer level process compatible NCF (Non conductive sheet). It should be high flowability for lamination on a bumped wafer surface without void, diced with wafer without deformation or sticking dust, transparent for alignment mark detection and low coefficient of thermal expansion (CTE) for the package thermal cycle durability. The nano particle dispersed and highly loaded NCF has been developed to satisfy the demanded characteristics. The CTE was 37°C/ppm and 1% weight loss temperature is higher than 350°C. The photosensitive NCF has been also developed. Bump top adhesive can be removed completely by photolithography before bonding process. It can wipe off the anxiety of adhesive residue between bump and pad. This material is also good for lamination and has high heat resistance of 1% weight loss temperature higher than 300°C.

Photosensitive polyimide adhesive sheet

Positive tone Photosensitive Polyimide B-stage sheet which was composed of transparent soluble polyimide, naphthoquinone diazide compound, thermal cross linker and solvent, was developed. We designed new polyimide structure and cross linker suitable for photosensitive polyimide sheet. The photosensitive sheet shows fine pattern formation capability as well as good thermal stability and mechanical properties. It is quite easy to obtain flat surface on topological surface to laminate the photosensitive sheet.