Multilayer Varistor Structure to Prevent Coating Peeling and Cracking
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Solution Overview
Problem
Existing multilayer varistors experience reliability issues due to glass coatings peeling off or cracking under severe environmental conditions, compromising their performance.
Innovation Solution
A multilayer varistor design featuring a sintered body with a high-resistivity portion comprising a surface and inner zinc silicate layers, and controlled porosity to enhance mechanical and thermal stability, reducing the likelihood of peeling and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass coating is applied to increase reliability, then reliability is improved, but glass coating peels off or cracks under severe environment
Solution Approach 1:
The patent changes the material parameters by forming a zinc silicate-based high-resistivity portion through heat treatment of a silicon-impregnated sintered body. This creates a surface layer with different thermal expansion characteristics and mechanical properties compared to traditional glass coatings, preventing peeling and cracking while maintaining high reliability under severe environmental conditions.
Solution Approach 2:
The patent creates a composite structure by impregnating the sintered body with silicon solution and forming a zinc silicate-based high-resistivity portion through heat treatment. This composite material combines the properties of the base ceramic with zinc silicate, resulting in a coating that adheres strongly and resists thermal stress without peeling or cracking.
2Object-affected harmful factors
If glass coating is applied to protect surface, then moisture resistance is improved, but coating cracks under thermal stress
Solution Approach 1:
The patent modifies the surface layer parameters by creating a zinc silicate-based high-resistivity portion with controlled porosity (smaller than in the facing region). This surface layer has optimized thermal and mechanical properties that allow it to withstand thermal stress without cracking while maintaining effective moisture barrier properties.
Solution Approach 2:
The patent utilizes controlled porosity distribution, where the surface region has smaller porosity than the facing region. This porous structure allows the zinc silicate-based high-resistivity portion to absorb and accommodate thermal expansion stresses, preventing crack formation while maintaining moisture resistance through the dense surface layer.
3Reliability
If high-resistivity portion is formed in surface region, then peeling and cracking are prevented, but manufacturing process becomes complex
Solution Approach 1:
The patent applies preliminary action by impregnating the sintered body with silicon solution before the final sintering process. This pre-treatment step allows the silicon to be distributed throughout the material, and subsequent heat treatment automatically forms the zinc silicate-based high-resistivity portion in the surface region, integrating multiple functions into a streamlined manufacturing sequence rather than requiring separate coating and treatment steps.
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 design significantly improves the reliability and moisture resistance of the varistor by preventing peeling and cracking, even under extreme thermal and mechanical stress, maintaining consistent electrical characteristics.
Implementation Method 1
The second step includes impregnating, at a reduced pressure, the sintered body with a solution containing silicon
Implementation Method 2
The third step includes conducting, after the second step, heat treatment on the sintered body to form a high-resistivity portion, containing zinc silicate
Data Source
AI summary
A multilayer varistor includes a sintered body, a first external electrode, a second external electrode, a first internal electrode, a second internal electrode, and a high-resistivity portion. The first internal electrode is provided inside the sintered body and electrically connected to the first external electrode. The second internal electrode is provided inside the sintered body and electrically connected to the second external electrode. The high-resistivity portion includes: a surface high-resistivity portion provided to cover a surface of the sintered body; and an inner high-resistivity portion extended inward from the surface high-resistivity portion inside the sintered body.