The external sealing layer of high voltage ceramic capacitors, specifically the epoxy layer, serves not only as an encapsulating material but also significantly impacts the overall quality and characteristics of the capacitor itself.

 

First and foremost, the bonding between the ceramic chips and the epoxy layer is a critical junction point. Weak bonding can lead to lower capacitance. Therefore, the density of these bonding sites directly affects the epoxy layer's integrity, with denser bonding resulting in a smaller number of partial discharges.

 

Secondly, during the operation of ceramic capacitors under high voltage or discharge conditions, heat-induced stress occurs. This repeated thermal stress causes expansion and contraction mismatch between the core components, leading to resin delamination. The gas dissipation capacity within the capacitor diminishes significantly, while the stress on the epoxy layer dramatically increases, making the capacitor susceptible to failure.

 

Furthermore, it is commonly acknowledged that after the sintering process at high temperatures, capacitors require a recovery period to alleviate thermal stress through natural processes. The longer the recovery time, the greater the capacitors' ability to withstand tension, ensuring higher quality. For instance, comparing newly produced capacitors with those that have undergone nearly two months of recovery, the latter exhibits a much higher tolerance to voltage, achieving levels of 80kV or more even when tested at 60kV initially.

 

Moreover, the choice of epoxy materials can impact the capacitors' performance at different temperatures. Some high-voltage ceramic capacitors may experience reduced effectiveness at low temperatures. For example, if subjected to freezing temperatures as low as -30 degrees Celsius, cracks may form due to poor epoxy properties at such low temperatures or incompatibility with the expansion and contraction of the ceramic chips. Consequently, the inconsistent stress caused by extreme cold fails to reduce the volume to the same extent, leading to structural strain.

 

By addressing these factors and ensuring the quality of the epoxy layer, manufacturers can improve the overall performance and reliability of high voltage capacitors.