Homogeneous Low Temperature Soldering Technology

M Affawn Ashraf, PhD; Rajen Sidhu, PhD; Alfred Yeo, PhD; Sireesha Gogineni; Kang Lin Chiew
Advanced Micro Devices Inc.
CA, USA

There is a shift in the microelectronic industry towards low temperature soldering (LTS) technology that incorporates a bismuth-based chemistry in Sn-based solder alloys. These chemistries are attractive due to their benign environmental impact and their capacity to keep warpages under control during the reflow process. However, enabling this technology requires investigating the quality and reliability of LTS ball grid array (BGA) mounted packages vs that of traditional Sn-Ag-Cu (SAC) BGA packages.

This paper presents key findings of enabling LTS technology on AMD’s Client BGA Packages using surface mount technology (SMT). It will highlight the thermal cycling performance of SAC and LTS assemblies are comparable, while in the mechanical shock testing the SAC assemblies performed significantly better than LTS assemblies. We recommend using adhesives (i.e. edge bond) to bridge the gap in mechanical shock performance of the two material technologies. In conclusion, LTS assemblies offer a viable alternative to traditional SAC under client-use conditions.

LTS assemblies on AMD’s client packages and their temperature cycling and mechanical shock testing reliability with SAC assemblies were compared. Results indicate that thermal cycle reliability performance of LTS packages is comparable with SAC packages, whereas the mechanical shock performance lower. Given this, edge bond processes are recommended to improve the mechanical shock performance of the LTS assemblies and bring it on par with SAC interconnects to enable future LTS assembly’s opportunities in the client segment.