Pump test analogy

Abstract: Mycronic is a company that manufactures a solder paste printer used to manufacturecircuit boards. Inside the printer solder paste is fed with the help of a screw pump.The solder paste, consisting of relatively soft metals has a tendency to stick to thescrew surface and form particles. These are then detached and passed on in thesystem and can clog the nozzle of the printer. This project investigated the possibilityof creating a model test where different parameters can be varied to evaluate itsinfluence on the amount of solder paste sticking to the surface of the screw. Testingthese parameters directly in the solder paste printer would be time consuming andexpensive.A pin-on-disk set up with some modified parts was used to emulate the solder pastemotion in the screw pump. The results were then analyzed in light optical microscope(LOM) and scanning electron microscope (SEM) equipped with energy dispersivex-ray spectroscopy (EDS).The parameters that were varied were pressure, temperature, rotation speed,substrate, content of the paste and the shape of the profile, which is supposed toemulate the ridge of the screw. It was shown that the profile shape, the substrate andthe pressure was of great importance in the deformation of the solder balls while therotation speed and the paste content had a small or no effect.The goal of the project is to recreate the agglomerates that have led to malfunctionsin the printing and evaluate which parameters that have the greatest significance.