Design Issues of LSI Packages

Semiconductor packages and printed circuit boards have become diversified, and their mounting technology has undergone remarkable changes and progress. Large‐scale integrated (LSI) packages and printed circuit boards are made of various different materials such as resins, and in the manufacturing process, heat load due to high‐temperature solder reflow of about 250 degree C or higher and various reliability tests after that are imposed. In order to solve the technical problems of such a thin and small LSI package, the author develops a simple and convenient viscoelastic analysis software Visco‐elastic Stress Analysis Program (VESAP). He demonstrates that VESAP analysis is a useful tool for optimal design of LSI packages. In addition, the author conceptually summarizes the necessity of analysis considering the viscoelastic properties of the resin material in the optimum design of LSI package.