Low Warpage Liquid Compression Molded Underfill for Wafer Level Packaging

As semiconductor chip design transforms to meet the increased functionality, performance, and miniaturization needs of applications such as 5G, high-performance computing (HPC) and autonomous vehicles, advances in packaging materials and technologies have become crucial to enable tighter pitches, higher interconnect density, and increased complexity of the new architectures. Liquid compression molded underfill (L-MUF) has drawn attention as a new wafer level packaging material for its capability to gap fill and over mold simultaneously under low pressure. This material capability has improved efficiency and sustainability of the process and enabled higher reliability of the final package. L-MUF material development challenges include achieving void free gap filling in fine pitch applications and maintaining low warpage during the packaging process. This paper presents analysis of L-MUF encapsulant materials that feature lower warpage compared to typical encapsulants, a high glass transition temperature, void free gap filling, and high reliability. The novel L-MUF materials are formulated with proprietary resin systems and ultra-fine fillers as key enablers for their unique material properties and application performance. The results demonstrate that L-MUF materials have the combination of good flowability and low warpage and have the potential to meet the growing demands of various wafer level packing applications.