3D RCP Package Stacking: Side Connect, An Emerging Technology for System Integration and Volumetric Efficiency

Abstract

Fan-out wafer level packaging (FO-WLP) has shifted from standard single die, single sided package to more advanced packages for System-in-Package (SiP) and 3D applications. Freescale's FO-WLP, Redistributed Chip Package (RCP), has enabled Freescale to create novel SiP solutions not possible in more traditional packaging technologies or Systems-on-Chip (SoC). Simple SiP's using two dimensional (2D), multi-die RCP solutions have resulted in significant package size reduction and improved system performance through shortened traces when compared to discretely packaged die or substrate based multi-chip module (MCM). More complex 3D SiP solutions allow for even greater volumetric efficiency of the packaging space. 3D RCP is a flexible approach to 3D packaging with complexity ranging from Package-on-Package (PoP) type solutions to systems including ten or more multi-sourced die with associated peripheral components. Perhaps the most significant SiP capability of the RCP technology is the opportunity for heterogeneous integration. The combination of various system elements including, but not limited to SMD's, CMOS, GaAs, MEMS, imaging sensors or IPD's gives system designers the capability to generate novel systems and solutions which can then enable new products for customers. To enable this ever increasing system integration and volumetric efficiency, novel technologies have been developed to utilize the full package space. Technologies such as through package via (TPV) and double sided redistribution are currently proving successful. For this discussion, an emerging technology for 3D RCP package stacking that can further enhance design flexibility and system performance is presented. This technology, package side connect, utilizes the vertical sides of packages and stacked packages to capture a normally unused piece of package real-estate. Mechanical and electrical characterization of successful side connects will be presented as well as reliability results of test vehicle packages using RCP packaging technology.