Improvement of an automatic wire feeding machine in a de-soldering process

Abstract

This paper presents the de-soldering process for rework of hard disk drive head stack assembly (HSA) units. An automatic wire feeder was used to place tin (Sn) onto the product. Improper feeding was determined to be one of the major causes of defective parts that had excessive amounts of Sn on the HSA. The defective parts due to the excessive amount of Sn were found to exceed 30% of production, which led to increased processing time and costs, since additional cleaning steps were needed. From the analysis, the major causes of excessive Sn were: 1) improper cutting of the wire, 2) inappropriate sizes and types of soldering materials, and, 3) inconsistent handling of the de-soldering process. This paper proposes approaches to address these three problems. First, the automatic wire feeding machine used in the de-soldering process was adjusted to properly cut wires into the flux core area. Second, the types of equipment and materials used in de-soldering were changed and optimized. Finally, a new standard method for operators, which could be easily controlled, was developed to allow consistent handling of the de-soldering process. After these process controls and machine adjustments were implemented, these excessive Sn related problems were significantly reduced. Sn contamination was found to be lowered by 41%. The cycle time was also found to be reduced by an average of 15 seconds.