Root cause analysis of solder flux residue incidence in the manufacture of electronic power modules

Abstract

This work investigates the root causes of the incidence of solder flux residue underneath electronic components in the manufacture of power modules. The existing deionized water-based centrifugal cleaning process was analyzed and hypotheses for root causes of the problem were proposed. The experimentation included cleaning tests using agitation and soak cycles. Parameters such as chemical agent, time and temperature were also tested for these tests. A novel method of residue incidence determination using visual inspection was proposed. Results suggest that the centrifugal process with water is incapable of providing enough agitation to effectively clean the residue. It was also found that product design and architectural causes greatly contribute to cleaning process effectiveness. It was concluded that effective printed circuit board cleaning requires high agitation and efficient product design.