Shinya Akizuki

Soluble and high molecular weight polyaniline

Low temperature polymerization of aniline using ammonium peroxodisulphate results in a soluble, high molecular weight polyaniline which forms a very strong free-standing film.

Study of encapsulating system for diversified area bump packages

With increasing numbers of handy electronic equipment in the market, the IC packages have become smaller size and require higher I/O for additional functions. The ultimate goal of IC assembly is direct chip mounting on Printed Circuit Board with flip chip interconnection. However the market is so complicated to expand bare chip mounting. The standardization of outer I/O in an IC package is one of the big advantage of IC packaging. Under above circumstance, area bump plastic packages such as Over Molded Plastic Ball Grid Array (OM-PBGA), and Cavity Down PBGA (CD-PBGA), and Flip Chip PBGA (FC-PBGA) are focused as standardized small body high I/O packages for future high end applications. Among area bump packages, the major one is OM-PBGA. The high potential package for high performance IC devices is CD-PBGA. For CD-PBGA, liquid compound is mainly used as IC encapsulant. And furthermore, FC-PBGA which has flip chip inner connection is available now as an option of the diversified application. Individual design conception are required for each IC encapsulating system and application. This paper is discusses about plastic IC encapsulation for diversified area bump packages explained here from the stand point of the material and the system.

Solid type cavity fill and under fill materials for new IC packaging applications

IC packaging methods are diversified drastically today, because of the requirement for the package to perform the IC characteristics itself. The majority of encapsulating material in the IC packaging market is transfer molding. However, the transfer molding method is hard to apply to some new applications such as flip chip, cavity fill type PPGA (plastic pin grid arrays), BGA (ball grid arrays), and tape carrier packages. Liquid type resins are mainly used for these new applications in the current market. However, there are several serious disadvantages to using liquid type resins. The problems are poor processability and reliability. Under these circumstances, we focused on the improvement of the two disadvantages for liquid resin applications on flip chip and cavity fill type PPGA and BGA. Our newly developed materials are solid compounds at room temperature. These compounds are designed based on the study of reliability and processability. The base resin systems are selected by moisture performance and fluidity characteristics.

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

Flip chip packages using plastic substrates are becoming popular in the IC packaging market. However, it still 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 onto substrate. Next, the bumped die is aligned and attached onto substrate which is covered by the underfill sheet under proper heat and pressure. The bumps under the die penetrate the resin and to reach the metal land of the substrate. Finally curing the underfill sheet and metal connection are carried out. We have studied the possibility of applying this packaging technology to a diversified bump and land combination by changing the underfill component and process parameters. The electrical stability and package warpage under several stress test conditions, such as JEDEC Level-3 and TST, have been evaluated in this study. After this evaluation, we found that the packages which have been built with proper resin components and process parameters show good performance for all of these reliability tests almost regardless of bump and land materials.