Determining Organic Solvent Bath Lifespan in Lead-Frame Cleaning

In high-power discrete packages, high-lead solder paste is used as the interconnect material between the die and the copper lead frame or copper clips. Flux, a component of high-lead solder paste, aids the soldering process by removing oxidized metal from the surface of the solder alloy and the lead frame. After reflow soldering, cleaning is essential to remove flux residues from high-power discrete packages. This typically involves using an organic solvent in a semi-aqueous cleaning process. The bath lifespan of the organic solvent is a key factor influencing process costs and product quality. Factors such as flux loading, copper content, and water content in the organic solvent were studied to understand their impact on the bath lifespan in the semi- aqueous centrifugal cleaning process. Various evaluation methods were developed using bath monitoring techniques to investigate these factors and assess their impact on bath lifetime. A packaging quality assessment was also performed to ensure that the determined bath life does not affect package quality. The findings were correlated with several customer case studies to validate the results and determine the organic solvent bath life in lead frame defluxing processes using a centrifugal cleaning system.