Study On The Caculation And Application Of Solder Paste Process Capability Based On Experiment Design

As the pillar industry of China Electronics EMS, SMT has entered into the miro-profit age. At this background, SMT manufacture has been forced to control cost more aggressively by increasing first pass yield. On the other hand, the development of PCB component integration results in the smaller process windows, which also drives the manufacture to improve their line quality management objective to decrease failure ratio. Therefore, the question of "How to measure and control SMT process quality" has become more and more important one to solve.As the important Index to measure and analyze process quality, Process Capability Index (Cpk) has been widely applied in SMT line quality management. However, Solder Paste Print Cpk is frequently calculated by wrong USL/LSL because SMT line inspection equipment is isolated each other and technology limitation. In this situation, the wrong Cpk value would result in mistake on process quality level judgment and affect the final process improvement action.This article first descript the situation of current SMT line quality control chain, then design the experiment to validate the existence of above problems and point out where is current inspection technology’s limitation. In the following contents, article design a method, which is presented by 0.4 mm CSP tolerance setting experiment, to solve this problem to get correct Cpk value. Whereafter, the article present the Cpk application in two field, which is the method to fast get printer manufacture parameter by Taguchi design of experiment and the process chart to control and continuously improving printer process by using Cpk.