Air voids and cavities in electrical components represent very significant problems. They reduce the life of the components, but above all they mean shortcomings in terms of their functionality, because they reduce the dielectric strength and thus the insulating value.
In most cases, the main cause of bubbles and cavities is the air contained in the casting materials. In the manufacture of components intended for higher voltages and field loads, almost all current insulating materials are degassed before being processed. Yet silicones are often still processed without pre-degassing. In most cases barrel pump systems are used to feed silicone directly from the delivery containersinto the mixing and casting process. Instead of degassing, attempts are made to crush the air bubbles in the material during molding. However, this is only partially successful, since the air remains in the material - products free of defects and bubbles are therefore a lucky hit, and the rejection rates are high.
The Silicone Vacuum Treatment SVT® developed by HÜBERS ensures that the components are absolutely free of voids and cavities. Due to the thorough degassing of the material components, bubbles are already prevented during material preparation.
Compared to methods without pre-degassing of the material, SVT® offers a very high quality of manufactured products as well as a significant advantage in production costs:
In processes without pre-degassing, very high pressures must be applied in the mold to crush the existing bubbles. Pressures of more than 200 bar are possible. On the one hand this requires large clamping forces and the use of steel molds, and on the other hand even more pronounced cast skins (,,flash") emerge due to the high pressure between the mold halves. With the SVT® method 2 to 6 bar in the mold is sufficient, thereby enabling the use of aluminum molds and avoiding the formation of cast skins almost completely.