Non-Aqueous Electrochemical Migration at High Temperatures
Author: Karen Tellefsen Company: Alpha Assembly Solutions Date Published: 6/5/2018
ICSR (Soldering and Reliability)
Abstract: High power amplifier modules often operate at temperatures greater than 100C. These components have large heat sink grounds on their bottoms and closely mounted input and output connectors. Flux residues get trapped between the ground and the other connectors, which are DC biased to provide power for the component. Because of the contained environment, it is difficult for the solvents and activators to volatilize as they would for most surface mount assemblies. When these components operate, the trapped flux residues, elevated temperatures and DC bias voltages may allow electrochemical migration (ECM) that may cause the component to short to ground and fail. At the elevated temperatures, the flux residues become a molten nonaqueous electrolyte, allowing corrosion followed by metal cation migration and deposition. This failure mechanism has been studied in order to create a test methodology for determining which solder paste fluxes are least likely to cause this failure during high temperature service under bottom terminated components.