SMT PRINTING PROCESS FOR FINE AND ULTRA FINE PITCH
Author: Richard S. Clouthier Company: AMTX, Inc. Date Published: 4/28/1997
Surface Mount International
Abstract: This article focuses on the five major areas which must be under control simultaneously since the printing process is a dynamic equilibrium. This process must place the 39 variables which are spread out between the boards, pastes, stencils/squeegees, printers, and the measurement equipment under stringent control. Some of data will be presented in: graphs, tables, histograms, figures and SEMS for ease of reading and assimilation. Even though solder paste printing is only one step of the total surface mount manufacturing process it’s one of the most critical steps. It is general knowledge in the industry that anywhere from 52-72°/0 of the SMT defects can be attributed to the printing step of the SMT manufacturing process. Therefore if the initial step of the process is susceptible to a high percentage of error then the degree of control of the remaining processes will not matter. The defects generated in the print process will only add cost and not quality in the down stream processes. As depicted by figure 1, if the input to and the printing process variables are under control then the output of the process will yield optimized quality, lower defects, higher yield and less rework which all add up to greater margins and quicker time to market. The balance of this paper will deal with the key variables which must be under control in the five critical areas of the print process.