Precise Robotic Paste Dot Dispensing

Many electronic assembly processes require dispensing small dots of heavily filled materials such as solder paste and loaded epoxies. Methods were developed for rapidly optimizing processes that control the size and shape of such dots. The approach was to separate the process of making a known quantity of material appear at the dispense tip from the process of depositing that material on the workpiece. It was found that controlling dot mass depends primarily on understanding valve frequency response, and that the shape of the dot is primarily a function of the height from which it is released. This report describes how a paste dot is dispensed, presents data from a series of characterization experiments, and discusses how to apply what was learned to a broad range of materials, equipment and processes. This is a preprint of a paper that will be presented at the 39th Electronic Components Conference, IEEE/CHMT and EIA, Houston, Texas, May 22-24, 1989. Copyright  1989 IEEE