Application of Experimental Design to the Solder Paste Screen Printing Process

Experimental design has proved to be a useful statistical tool in reducing process variation. The technique has been applied to a wide range of processes, including electronics assembly and soldering processes. For effective SMT assembly the screen printing of solder paste requires tight process control, especially as pad geometries become ever smaller. However, printing of solder paste is a rather complex process which is affected by machine, material, environmental and human factors, which make it difficult to characterise effectively. This paper examines the practical application of experimental design to solder paste printing for SMT and also the results from a number of experiments carried out on a semi‐automatic ‘clamshell’ type screen printer. The experimentation concentrates on the important printer and squeegee parameters and their effect on paste deposition, with measured solder paste height and ‘measle’ diagrams used as process outputs. The usefulness of the experimental results in determining ...