Taguchi Experimental Design for Cleaning Pwas with Ball Grid Arrays

E3all grid arrays (E3GAs), and other area array packages, are becoming more as a way to increase component pin count while avoiding the manufacturing prominent difficulties inherent In processing quad flat packs (QFPs). The JF)L Electronic Packaging and Fabrication section is currently conducting process development in order to be able to effectively place BGAs on printed wiring boards (PWE3S). Among the important processing steps is that of cleaning, which generally follows component placement anti solder reflow. Cleaning off cietrimental residues left after the various processing steps, especially solder paste application and solder reflow, is necessary to avoid harmful contaminants remaining on the PWB surface. Cleaning printed wiring assemblies (F’WAS) with BGA components mounted on the surface is problematic. Although these components typically have a standoff of 0.015 inch -0.025 inch, cleaning under such components is complicated by the hundreds of solder ball leads that such components have. Currently, a low flash point semi-aqueous material, in conjunction with a batch cleaning unit, is being used to clean PWAS, l-he approach taken at JPL was to investigate the use of (1) semi-aqueous materials having a high flash point and (2) aqueous cleaning involving a saponified, In order to optimize the experiment---that is, to maximize the information gained and to minimize the cost of conducting the investigation, the experiment was set up using Taguchi Design of Experiment (TIIOE). The details of the approach and the final results are presented in the paper.