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|Solder and Die Attach for High Temperature Electronic Packaging|
|Keywords: solder, attach, reliability|
|The RoHS ban of lead from electronics has pushed the industry to find lead-free alternatives. This is true even for high temperature applications, where high lead solders have typically been used. This paper will present two ongoing studies that address the need for both chip and component attach that can survive high temperature operation and wide temperature range cycling. The first study focuses on the durability of lead-free component attach under combined temperature cycling and vibration for applications above 125°C. Quad flat packs (QFP) and 2512 chip resistors were reflowed on ENIG finished polyimide printed circuit boards with commercially available SAC305 and with versions of SAC305 containing intentional fourth element doping. The doped alloys were chosen because of previously published results showing reduced intermetallic formation in solders containing these elements. Isothermal aging for up to 500 hours was performed to measure the interfacial intermetallic thickness, and characterize intermetallic compounds. An assessment was then performed featuring thermal cycling intermixed with vibration cycling to determine the most durable solder alloy. The second study focuses on the manufacture and temperature cycling durability of transient liquid phase sintered die attach joints made with different combinations of a high melting point metal and a low melting point semimetal. Results will be shown describing the effect of different compositions and reflow profiles on percent conversion and voiding. Shear test results will demonstrate joint strength at temperatures up to 500°C.|
|Patrick McCluskey, Associate Professor
University of Maryland
College Park, MD