Copper Oxide Removal Activity in Nonaqueous Carboxylic Acid Solutions

Abstract

Flip chip joint quality and reliability are strong functions of process parameters, materials and reactions before, during, and after solder reflow. In this work, we examine CuOx removal effectiveness of nonaqueous carboxylic acid solutions using electrochemical methods at temperatures from 100°C to 180°C. Chronopotentiometry and gravimetric analysis were used to study reaction kinetics, FTIR was used to study surface chemistry, and spectrophotometry was used to quantify reactant and product solubilities. Kinetics were investigated using carboxylic acid solutions such as adipic acid or maleic acid in polyethylene glycol. Carboxylic acid-based solutions with complexing agents show CuOx removal rates are similar to hydrochloric acid solutions at temperatures above 140°C. Results suggest the combination of proton-donating complexing agents with carboxylic acids can increase CuOx removal rates by an order of magnitude over solutions without complexing agents. A model including the formation of soluble Cu2+ complexes and the regeneration of carboxylic acids is presented.

Expanding the Range: AuCu Metal Aerogels from H2O and EtOH

“…To remove the copper oxide needles from the gel, an acid post-treatment step can be applied. In particular, carboxylic acids are known to gently dissolve CuO [53,54]. Furthermore, formic acid (HCOOH) has proven to be a selective etchant for CuO in the presence of metallic copper [55][56][57].…”