Detail: Field test with abrasive copper solder paste ? 2016 ViscoTec Pumpen- u. Dosiertechnik GmbH

Solder pastes are used for soldering metals and alloys such as copper, bronze, zinc or silver. A superficial connection is produced in the form of a melt, which solidifies after cooling. In many cases, solder pastes are used in the electronics sector of the automotive industry.

Due to abrasive particles in the medium, solder pastes place high demands on the dosing components used. Especially in shifts, the industry is pushing for low-wear solutions and long service life. ViscoTec’s eccentric screw pump has established itself in this particular market sector for a number of reasons: a uniform volume flow in the dosing pump prevents sedimentation of the filling material, concentrations of filler are avoided due to low pressures being exerted and a pulsation-free feed and also the fact that the rotor-stator combination of stainless steel and an elastomer ensures minimum shearing in the handling of the fluid.

ViscoTec dispensers are often integrated into fully automated systems as large scale paste application systems. This is just the case at one of the leading tier-one automotive supplier in Germany. Here, a glycol-based, highly filled copper solder paste is in operation. Due to the high degree of filling, the density is approximately 4,0 g/cm3. The application system is operated by 4 parallel dosing station units running in a three shift fixed cycle of 24 hours a day, 7 days a week.

Within the scope of a changeover to the largest of the RD-series of dispensers, the 3RD12, the dosing pump was tested under constant load over nine months - with surprising results: the stator, consisting of a mechanically stable elastomer, showed a deviation of only 0,04 mm from the reference value. No wear marks could be measured on the stainless steel rotor.

A highly satisfactory result in view of the extreme conditions of this real life situation. This was made possible by the number of year’s experience which ViscoTec has accumulated in the technical design of abrasive applications. In this particular case, the dispenser is operated at only 30% of the maximum revolution speed in order to minimize the flow velocities of the medium and therefore also reduce the impact force of the particles within. In addition to this know-how, the close co-operation with the material manufacturers and the constant optimization of the elastomers used, are the foundation for the success in this challenging field.