Ultra-low Warpage and Anhydride-free Liquid Compression Molding Materials for Advanced Semiconductor Packaging

Abstract

Advanced semiconductor packaging landscape is rapidly evolving to accommodate requirements of front end node shrink and performance expectations from emerging applications in big data, artificial intelligence, mobile and autonomous driving. Multiple innovations in packaging process technology as well as processing materials enable the progress in advanced packaging. Several wafer level packaging (WLP) platforms have emerged recently using fan-in, fan-out, 2.5D and 3D packaging processes to satisfy the requirements of increased functionality, reduced form factor, lower power consumption, and high reliability. These often-conflicting requirements drive the design and development of many new electronic materials including liquid compression molding (LCM) for Fan-In and Fan-Out WLPs. Historically, anhydride-based LCM materials have been used to balance the material properties to achieve consistent dispensability, high quality molding, and high mechanical stability during grinding, RDL, and singulation processing. However, stricter environmental regulations driven by EU REACH stipulates complete replacement of anhydride resins with more environmentally friendly raw materials while still providing the same or better performance. Most recently, Henkel has developed new platforms of anhydride-free LCM materials with reduced cure shrinkage, ultra-low warpage, good chemical resistance, and high reliability. LCM material choice is integral to the package design and end use as this material needs to withstand several thermal, mechanical, chemical and vacuum processes during the construction of the package and stringent reliability conditions. By judicious construction of the polymer network, appropriate filler selection, and controlled cure kinetics design, the cure shrinkage and warpage were significantly reduced over other designs. Furthermore, the low warpage stability of the molded wafer is maintained through post-mold curing, PI simulation, and RDL simulation process steps ultimately leading to improved reliability performance. Compared to traditional anhydride-based LCM, our reliability data (after 96 hours of uHAST & 1000 cycles of AATC) clearly indicates performance advantages of no filler-fall-off, no delamination, and better chemical resistance. In terms of workability, the new system shows improved work-life, fast-cure at 110–130°C, and complete gap filling. Lower die shift, good mold release, and improved tape debonding has also been observed through formulation and process optimization. Taking advantage of the proprietary resin and formulation design, Henkel's new LCM materials are delivering positive results in new FO-WLP designs and WLCSP applications needing 5-side or 6-side protection.