Board level reliability improvement in eWLB (embedded wafer level BGA) packages

When it comes to reducing form-factor and increasing functional integration of mobile devices, Wafer Level Packaging (WLP) is an attractive packaging solution with many advantages in comparison to standard Ball Grid Array (BGA) packages. With the advancement of various fan-out WLP (FOWLP), it is a more optimal and promising solution compared to fan-in WLP because it can offer greater flexibility in design of more Input/Output (I/O) counts, multi-chips, heterogeneous integration and three-dimensional (3D) system-in-package (SiP). embedded Wafer Level Ball Grid Array (eWLB) is a type of fan-out WLP enabling applications that require smaller form-factor, excellent heat dissipation, and a thin package profile as it has the potential to evolve in various configurations with proven manufacturing capacity and production yield. eWLB is one of key advanced packages because of advantages of higher I/O density, process flexibilities and integration capabilities. It facilitates integration of multiple dies vertically and horizontally in one package without using substrates. The structural design as well as selection of materials becomes more important in determining process yield and long term reliabilities. Therefore, it is necessary to comprehensively investigate the key design factors affecting the reliability. In this paper, the influences of materials and structural designs on the board level reliability will be demonstrated. The structural analysis has been performed by going through every design factor in a board level. The reliability study was carried out in depth by experimental approaches as well as through thermo-mechanical simulations. The different structural design prolongs the life by giving more resistance to the crack propagation and also makes the entire package body more flexible. This paper also discusses the recent advancements of robust board reliability performance of large size eWLB. Standard JEDEC board level tests were carried out to investigate board level reliability of large size test vehicles and both destructive/non-destructive analyses were performed to investigate potential structural defects. Daisy chain test vehicles were also tested for board level reliability performance in industry standard test conditions.