A study of new flip chip packaging process for diversified bump and land combination

Flip chip packaging using plastic substrates is gaining popularity in the IC packaging market. However, the process has not been standardized as a real mass production system. We have newly developed a flip chip packaging technology using a nonconductive underfill resin sheet. The process flow of the new flip chip packaging is as follows. First, the underfill sheet is laminated to the substrate. Next, the bumped die is aligned and attached to the substrate, which is covered with the underfill sheet under appropriate heat and pressure conditions. The bumps under the die penetrate by displacing resin and eventually reach the metal land of the substrate. Finally, curing of the underfill sheet and metal connections is done. We have studied the possibility of application of this packaging technology to diversified bump and land combinations with changing underfill components and process parameters. The electrical stability under several stress test conditions such as JEDEC Level-3 and TST has been evaluated in this study. After this evaluation, we found that the packages which were built with the appropriate resin components and process parameters show good performance for all of these reliability tests, almost regardless of bump and land materials.