Surface mounted PCB cleaning process improvement and Its impact on manufacturing system performance

Abstract

In the surface mount technology (SMT) assembly line, the printed circuit boards (PCB) are washed to remove the solder flux that was used while soldering to prevent oxidation. However the current cleaning method is highly ineffective in removing these solder flux residues. The solder flux residues cause many problems like electro-migration, improper mold underfill and increase the chances of failure. This project explores alternative methods for the cleaning process and also identifies the important factors involved in cleaning. A model of the SMT assembly line was created using ARENA software and the impact of the different alternatives on the manufacturing system's performance was analyzed using this model. The results indicate that the use of chemicals in the ultrasonic cleaning method gives the best cleanliness performance. The results of the manufacturing system analysis show that the PCB cleaning process is not the bottleneck process in the SMT line and hence none of the different alternatives significantly impacted the throughput rate, cycle time and inventory levels. Cost comparison results also indicate that using chemicals in the batch type ultrasonic machine was atleast 25% cheaper than using chemicals in either centrifugal machine or in in-line machine.