Towards a better understanding of underfill encapsulation for flip chip technology: proposed developments for the future

Most flip chip assemblies require underfill to bestow reliability that would otherwise be ravished by stress due to thermomechanical mismatch between die and substrate. While underfill can be viewed as “polymer magic” and the key to modern flip chip success, many see it as the process “bottleneck” that must be eliminated in the future. Both views are accurate. A substantial amount of R&D is being focused on making underfill more user‐friendly. Electronic materials suppliers, various consortia, government labs and university researchers are working diligently to shatter the bottleneck and fully enable flip chip ‐ the final destination for micropackaging. This paper will describe these efforts and provide a status report on state‐of‐the‐art underfill technologies. We will also examine new processing strategies.