Yu-Chieh Lin
Advisor: Prof. CP Wong
will defend a master’s thesis entitled,
Investigation of the Chemical and Physical Impact of No-Clean Flux Residue on Board-Level Underfill Performance
On
Friday, April 25 at 11:00 a.m.
via MS Teams
https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZTdhODcxODAtOGJj…

Abstract
This paper investigated the chemical and physical impact of No-Clean Flux (NCF) residue among the Solder/underfill/Cu clad interface in electronic packaging. NCF use mild activator acid to mitigate the influence in package, but the NCF residue can still cause reliability issue in long term, like adhesion failure, corrosion. Two flux types—alcohol- and rosin-based—were heated with lead-free SAC305 (96.5Sn-3Ag-0.5Cu) solder through reflow process, and underwent curing profile with dispensed Bisphenol-A Epoxy. Residues were generated via reflow process (soaking: 120–140°C, peak: 240–260°C, under N₂) and characterized pre-/post-reflow using FTIR, revealing oxidative degradation (increased C=O, decreased C-O/O-H peaks). Laser microscopy confirmed solder wettability under reflow conditions. Collected residues were mixed with epoxy and analyzed via TGA/DSC, showing altered curing kinetics. Cross-sectional SEM/EDS of samples showed voids, ionic salt migration, and interfacial residue accumulation, which correlated with adhesion failure during dicing and DSC curing curve. These results highlight the critical role of flux chemistry in interfacial reliability and suggest optimizing underfill formulations or reflow parameters to mitigate residue propagation.
Committee
•    Prof. CP Wong – MSE (advisor)
•    Prof. Meilin Liu– MSE
•    Dr. Kyoung-Sik Jack Moon – MSE
•    Dr. Mohanalingam Kathaperumal – ECE