Hybrid 3D Package with RDL and Laminate Substrate for Ultra-Thin and High-Bandwidth Applications

Abstract

In this work, a hybrid 3D package combining a redistribution layer (RDL) and laminate substrate layer for ultra-thin and high-bandwidth mobile applications are discussed and demonstrated. The motivation behind this hybrid 3D package structure was leveraging the advantages of high density RDL layer and advanced laminate substrate layer in one package to optimize package features or performance in bandwidth, package height, assembly manufacturing and package level as well as board level reliability to each specific industry requirement. For demonstration purposes, a $12.5\times 12.5-\text{mm}$ hybrid 3D packages combining a high density RDL and advanced laminate-substrate layer were designed and manufactured. In this demonstration, the $12.5\times 12.5-\text{mm}$ hybrid 3D package showed $395\ \mu \mathrm{m}$ package height including ball grid array (BGA) solder ball height and package warpage of $+64\ \mu \mathrm{m}$ (in crying mode) at 25°C and $-81\ \mu \mathrm{m}$ (in smile mode) at 260°C. The demonstration package passed package level reliability tests including unbiased highly accelerated stress test (uHAST), temperature cycling (TC) test and high temperature storage (HTS) test. The package showed less creep strain energy density (CSED) of the BGA solder balls under board level reliability-temperature cycling conditions than that of the RDL-based 3D package in the finite element model (FEM) simulation to a fully top package and 3D package stacked structure.