Cracked High-Resistance Layer in Multilayer Varistors
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Solution Overview
Problem
Multilayer varistors face the challenge of insulation failure due to the migration of ionized metal between electrodes when applied with voltage in a high-humidity environment.
Innovation Solution
A multilayer varistor design featuring a sintered body with internal and external electrodes, and a high-resistance layer with a surface having a plurality of cracks, which increases the creepage distance between electrodes and acts as a migration barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-resistance layer is formed to cover the sintered body surface, then insulation performance is improved, but metal ion migration still occurs in high-humidity environments
Solution Approach 1:
The high-resistance layer is designed with a cracked surface structure that creates a porous configuration. These cracks increase the surface path length for metal ion migration, effectively blocking the harmful migration path while maintaining the insulating function of the layer.
Solution Approach 2:
The solution transitions from a flat, two-dimensional surface coating to a three-dimensional cracked surface structure. The cracks create additional surface area and extend the migration path in the horizontal dimension, preventing direct vertical migration between electrodes.
2Reliability
If the high-resistance layer is made thicker to improve insulation, then insulation performance is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of increasing the thickness parameter of the high-resistance layer, the invention changes the surface morphology parameter by introducing cracks. This parameter substitution achieves improved insulation performance without the drawbacks of increased thickness, such as longer processing times and higher manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The increased creepage distance and the presence of cracks in the high-resistance layer effectively suppress the migration of metal ions, preventing insulation failure and ensuring reliable operation in high-humidity conditions.
Implementation Method 1
the high-resistance layer has a surface having a plurality of cracks... effectively suppress the migration of metal ions
Data Source
AI summary
A multilayer varistor of the present disclosure includes a sintered body, a first internal electrode, a second internal electrode, a first external electrode, a second external electrode, and a high-resistance layer. The first internal electrode and the second internal electrode are disposed in the sintered body. The first external electrode is disposed on a surface of the sintered body and is electrically connected to the first internal electrode. The second external electrode is disposed on the surface of the sintered body and is electrically connected to the second internal electrode. The high-resistance layer covers at least part of the surface of the sintered body, and the high-resistance layer has a surface having a plurality of cracks.