Experimental Study on 28nm Chip/Package Interactions in eWLB (Embedded Wafer Level BGA) Fan-Out Wafer Level Packages

Abstract

To meet the continued demand for form factor reduction and functional integration of electronic devices, WLP (Wafer Level Packaging) is an attractive packaging solution with many advantages in comparison with standard BGA (Ball Grid Array) packages. The advancement of fan-out WLP has made it a more promising solution as compared with fan-in WLP, because it can offer greater flexibility in enabling more IO's, multi-chips, heterogeneous integration and 3D SiP. In particular, eWLB (Embedded Wafer Level BGA) is a fan-out WLP solution which can enable applications that require higher I/O density, smaller form factor, excellent heat dissipation, and thin package profile, and it has the potential to evolve in various configurations with proven integration flexibility, process robustness, manufacturing capacity and production yield. It also facilitates integration of multiple dies vertically and horizontally in a single package without using substrates. For eWLB fan-out WLP, the structural design as well as selection of materials is very important in determining the process yield and long term reliability. Therefore it is necessary to investigate the key design factors affecting the reliability comprehensively. This work is focused on an experimental study on the chip-package interactions in eWLB fan-out WLP with multilayer RDL's. Standard JEDEC component and board level tests were carried out to investigate reliability, and both destructive and non-destructive analyses were performed to investigate potential structural defects. Warpage, die cracking and other failures were characterized through metrology measurements and electrical tests. Board assembly processes (including SMT, underfill, etc.) were also studied. The influence of materials and structural design on the package reliability will be demonstrated. Thermal characterization and thermo-mechanical simulation results will also be discussed.