Evolution and Applications of Fine-Feature Solder Paste Printing for Heterogeneous Integration

The semiconductor industry is quickly adopting heterogeneous integration as a solution to allow a large number of dies to be packed onto smaller components, improving cost-performance while expanding functionality. As such, the printing of solder paste formulated for System in Package (SiP) applications is becoming more difficult, with many depositions designed at one point as extremes during testing becoming the norm in industry. This paper will first briefly discuss the evolution of soldering material for heterogeneous integration, as some aspects of solder paste manufacturing, such as powder size, differ significantly from larger scale soldering applications. The objective of this study is to illustrate critical parameters for the printing of SiP paste. Multiple parameters that are important for SiP paste printing applications will be discussed, such as the metal load optimization, paste rheology, and metal powder size, type, and quality.