SMTA International Conference Proceedings

Reliability Evaluation of Ultra Large BGA System-In-Package (SiP) Module Assemblies

Authors: Weidong Xie, Cherif Guirguis, Qiang (Johnson) Wang, and Mudasir Ahmad
Company: Cisco Systems, Inc.
Date Published: 9/28/2014   Conference: SMTA International

Abstract: According to Cisco's Visual Networking Index Forecast [1], the amount of internet traffic will quadruple by 2015, driven by the increase of mobile devices and video content in the network. To meet such explosive demand, the industry has been developing new packaging solutions that will enable engineers to pack more functions and deliver higher speed with same or smaller form factors. An innovative System-in-Package (SiP) module has been developed as cost-effective packaging technology. This ultra large 90x90 mm module accommodates fourteen DDR3 memories and one flip chip ASIC with an organic substrate. The challenges and corresponding solutions in packaging design, process, and assembly of such a large organic BGA module has been outlined by Ahmad, et al. [2].

In this study, a full scale reliability evaluation of the SiP module assembly has been conducted. The evaluation included 0/100°C Accelerated Temperature Cycling (ATC), mechanical shock under different impulse G levels, and mechanical four-point bend. The test vehicle of this study has been designed to include multiple chains for real time continuity monitoring of interconnects at different levels, i.e. from ASIC flip chip to module substrate, from DDR3 memory components to module substrate, and from SiP module to Print Circuit Board (PCB). Some of those daisy chains were dedicated to the interconnects in high stress regions such as die shadow areas and package corners to allow pinpointing of the failures at the exact locations during the reliability evaluation. Strain gauges were attached onto the PCB during shock and bend testing so that the board level strains at failure could be recorded. Furthermore, an acoustic emission system has also been adopted during 4-point bend testing to study the onset of pad cratering. Finite element analysis has also been performed to evaluate the stress and strain distributions of the solder joint interconnect structure during shock and bend testing. The insightful results of this study are valuable to design robust and reliable ultra large BGA module assemblies.

Key Words: 

solder joint reliability, lead free, assembly, system-in-package, MCM module

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