Symposium Conference Proceedings

Challenges and Solutions for the Effective Removal of OA Flux Residues

Authors: Umut Tosun, M.S.Chem.Eng.
Company: ZESTRON America
Date Published: 11/18/2014   Conference: Symposium

Abstract: PowerPoint Presentation Only

OA or water soluble flux remains a viable option within the electronics manufacturing industry, primarily for non-high reliability applications, although it can be used for high reliability applications as well. Nonetheless, once the decision is made to use an OA flux, measures must be taken to fully remove all flux residues. Due to the high activity level of water soluble fluxes, residues remaining on the board surface can lead to board failures resulting from electrical leakage current, electrochemical migration and dendritic growth. OA flux is designed to be cleaned with water, however, with the increase in component density on the board surface, and the ever reducing component standoff height, a DI-water cleaning process is challenged to meet today’s cleaning requirements. Compounding this challenge is the use of lead-free OA flux. These require higher reflow temperatures resulting burnt in fluxes or tin oxide residues that are even harder to remove as they begin to produce water insoluble contamination. Considering these challenges, a study was undertaken whereby PCB test vehicles were populated with numerous low standoff components and soldered with a variety of both leaded and lead-free solder pastes. Following reflow, all test vehicles were cleaned using a DI-water process as well as a chemically assisted process using an aqueous-based engineered cleaning agent specifically designed to clean OA flux residue at very low concentrations. The performance of the cleaning agent was compared to that of pure DI-water. Cleanliness was assessed per the IPC Test Method for visual inspection for surface, under component cleanliness, and cosmetic effect. Ion Chromatography analysis was also performed. Employing this effective cleaning agent from these tests, a customer evaluation was undertaken comparing this cleaning agent to that of DI-water as well as other available cleaning agents. All test results are compared and reported with optimal cleaner operating parameters recommended.

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