Ensuring efficient and reliable operation
"Insulation" describes the complete encapsulation or filling of electronic components with suitable casting resins. In addition to protecting the components from external influences, this process also helps to improve their performance and mechanical, thermal and electrical properties as well as to extend their service life. To ensure bubble-free application, both the material preparation and feeding process as well as the potting process itself must take place in a vacuum.
In the case of insulation, electrical components under heavy loads, such as transformers, ignition coils, restrictors and capacitors, are completely filled with casting resin. This serves on the one hand to protect the coils from damaging environmental influences such as heat, moisture, vibration and dirt, thus increasing the longevity and reliability of the components, while on the other hand also improving the performance and properties of the parts. For instance, depending on the requirements, the casting resins used provide the components with higher mechanical stability, optimized heat dissipation, or improved high voltage resistance or temperature stability, thus ensuring a high level of operational reliability. Vacuum potting is usually selected to prevent the introduction of air bubbles, which can negatively impact the electrical properties of the components.
Custom casting resins
Coil components are commonly employed in the aerospace industry as well as in medical technology and in the military. They are also used in the field of energy technology – particularly for wind power stations and photovoltaics –, in the electronics and electrical industries and in the automotive industry. The growing use of hybrid and electrical vehicles is making coil products increasingly important even in the field of electromobility.
Depending on the application and requirements, materials with very different properties can be used to insulate these components. The key selection criteria include, for instance, fluidity, the type of curing, the thermal expansion coefficient, volume shrinkage, or the crack resistance after the material has cured.
Protecting components from electrical breakdown and corrosion
In the case of coil products and components with narrow potting spaces or undercuts, vacuum potting is often the only option for achieving reliable results and ensuring the long service life and lasting performance of the parts. Particularly in the case of highly functional or safety-related components, residual air bubbles in the potting compound or in the small voids of the coils can cause tremendous problems. Not only do they jeopardize the high voltage resistance, but they can also cause corrosion as a result of moisture entering the component. To ensure completely bubble-free potting, the entire preparation, feeding and dispensing process must take place in a vacuum.
Using thin film degassing, any trace of dissolved air in the potting medium can be removed as early as during the material preparation and feed process. A suitable agitator, which continuously circulates the medium used, also helps with degassing in the vacuum container. The continuous circulation causes the remaining air bubbles in the medium to rise to the top. At the interface between the material surface and vacuum, they then pop and are thus removed from the potting medium.
For the actual potting process, it is essential to remove even the smallest of air bubbles from the fine coils. For this purpose, the potting chamber is first placed in a vacuum and the component is filled with the prepared casting resin. In the next step, a brief intermediate release of air or a brief buildup of pressure ensures that the potting medium is pressed against surface tension even deeper into the small spaces of the coils. A final finishing layer then ensures the material is distributed evenly within the component.
TIP: Not every component can handle a sharp drop in pressure. While a coil product is for the most part unaffected by such conditions, the air encapsulated in a capacitor can cause the component to crack under external negative pressure. The vacuum should therefore be adjusted beforehand for the particular task.
