Dosing of abrasive thermal pastes in cyclic operation

The ultimate stress test for stator materials

Abrasive thermal pastes are found in a range of applications. In the production of LEDs and circuit boards in the electronics industry and in the area of control systems in automotive applications - to name but a few examples. Through the regulation of thermal resistance, these pastes, referred to as gap fillers, ensure the heat transfer between the two components. To guarantee this property, the gap fillers are offset with up to 90 % filler material. The following rule of thumb applies: The higher the filler content, the higher the density.

In dosing technology, thermal pastes put very high demands on the dosing systems because the fillers tend to form sediment and on the other hand are highly aggressive to the dispensing unit. Therefore two parameters are essential: Firstly, the level of pressure has to remain as consistent as possible during the dispensing process to prevent separation between filler and binder and, secondly, the right choice of materials in the design of the dosing components for abrasive media has to be made.

In this context, a highly aggressive thermal paste has been tested at ViscoTec’s technical centre. In 1,500 dispensing cycles and 80 hours of operation, more than a ton of gap filler was dispensed with ViscoTec’s eccentric screw pump. The supply of the medium was determined using the barrel emptying system ViscoMT-L from a 200 litre barrel. The 160 ml dosing shots were dispensed with the positive displacement pump 3VMP22. To further increase the load of the stator, the dosing pressure was kept constant at 20 bar. Two mechanical highly resistant elastomeric mixtures from the ViscoTec stator portfolio were tested.

The wear and tear of the stator was evaluated based on the dimensional deviation before and after the trial. This resulted in an average deviation of 0.45 %, which exceeded the expectations of the material manufacturer. By using the eccentric screw pump from ViscoTec, the end user benefits from an extended service life of the dosing components - which in turn contributes to improved energy efficiency and a reduction in maintenance and repair costs.