Authors:

Timothy P Malloy

Date Created:

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About Paper:

Solder joint failure in microelectronics can appear in many ways. Electromigration and solder joint fatigue are some of the most common reliability concerns for solder alloys. Electromigration in solder alloys - the movement of metal atoms due to high density currents - causes degradation of solder. Solder joint fatigue, on the other hand, is the mechanical degradation that occurs due to repeated stress and strain from thermal cycling. Solder joint geometry and material composition are known to affect the rate at which these degradations occur. To better understand these degradations, this research aims to develop a testing platform for electromigration in solder alloys and collect data to characterize their fatigue performance. For electromigration, a custom PCB was designed using KiCad 9.0 and printed by a vendor. A copper line 30 microns in height has 3 gaps: 300 microns, 200 microns, then 100 microns. In these gaps, custom solder paste was placed (various pastes were tested, including tin-silver-copper and tin-bismuth). As high- density current flowed through the circuit, the increases in resistance - an indication of electromigration - across the joints vs time were graphed. For fatigue testing, the HiDAC lab's custom-made closed-loop precision mechanical tester applied a displacement profile to the solder joint. This machine ran fatigue tests until the load range decreased by 75%, defining the N25 fatigue life. Fatigue tests were performed over different strain ranges, covering both high-cycle and low-cycle fatigue. Our platforms enables solder characterization and provides deeper insights into solder alloy reliability in microelectronics. Keywords: Solder; Electromigration; Fatigue; Microelectronics; SCALE

Source:

Purdue University / 2025

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Co-authors:

Timothy P Malloy