Master of Science (MS)
The activity of halogen-free carboxylic acid flux is considered one of the most important aspects in controlling flip chip joint quality recently. In this work, we examined the CuOx removal effectiveness of carboxylic acid solutions at Cu substrates using electrochemical methods at elevated temperatures from 100ºC to 180ºC. Reaction kinetics of CuOx removal were investigated by chronopotentiometry and gravimetric analysis. FTIR was used to study the surface chemistry, and spectrophotometry was used to understand reactant and product solubility. Kinetics of carboxylic acid solution such as adipic acid or maleic acid in polyethylene glycol (PEG) with and without complexing agents such as ethanolamine was investigated. Carboxylic acid-based solutions with ethanolamine show oxide removal rates similar to hydrochloric acid solutions at temperatures above 140ºC. Results indicate the combination of proton-donating complexing agents with carboxylic acids can increase oxide removal rates an order of magnitude over solutions without complexing agents. Sn (II) and Sn (IV) voltammetry shows Sn2+ and Sn4+ can form Sn-carboxylate complex and dissolve into the solution. XPS results indicate under high temperature (180 ºC) and relatively low pH (~2.50), carboxylic acid can clean the surface of Sn as well as halide acid. Equilibrium coefficients between the complexes are obtained and potential-pH diagrams for adipic acid and maleic acid in PEG are presented.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Qu, Guoying, "Activity of halide-free flux at copper and tin surfaces" (2013). LSU Master's Theses. 3016.