Testing and long-term monitoring within printed circuit board cleaning technology

摘要

Purpose - The purpose of this paper is to present the development and implementation of a system of test methods for determining the contamination level in cleaning baths and using this system for long-term monitoring in printed circuit board (PCB) production. Design/methodology/approach - A set of test methods was chosen that indicated the contamination of production cleaning baths in four chambers of an ultrasonic cleaning equipment filled with a commercial alkaline cleaner and isopropanol. By long-term monitoring, the amount of mechanical impurities, residue-on-evaporation, pH and conductivity were measured. Depending on the contamination of the cleaning baths, the final contamination of PCB surfaces was predicted and the baths were replaced with fresh baths. Findings - A novel system for testing and monitoring the contamination of cleaning baths was developed and implemented. The sustainable compliance with the specification was assured in PCB production, thus, the final PCB contamination achieved was under 1.5/1.2 /*g NaCI/cm2 as measured using the IPC-TM-650 test method. Quality requirements were fulfilled. This novel system was successfully integrated into the company's quality management system. Research limitations/implications - The set of test methods were used for an alkaline cleaner and isopropanol and for both a conventional solder and a lead-free one. Because the course of bath contamination, monitored by the four test methods, was found to be proportional, further development should be focused on the issue - i.e. to determine if the "proportionality" would be universal for all types of PCB manufacturing. Originality/value - The paper deals with a new approach for quality testing and assurance in PCB manufacturing. A set of test methods for monitoring contamination levels in production cleaning baths was implemented. This also supports process control and minimises the impact of cleaning processes on the environment (i.e. the production of waste from cleaning was reduced).