Multi-Layer Varistor Ceramic Gradient for Lower Capacitance
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Solution Overview
Problem
Existing multilayer varistors face challenges in reducing capacitance without compromising breakdown voltage or increasing leakage current, primarily due to the limitations of ZnO ceramic dielectric constant and stray capacitance, which are not effectively addressed by current manufacturing methods.
Innovation Solution
A multilayer varistor design utilizing two or three ceramic materials with varying concentrations of monovalent elements, creating a concentration gradient to minimize dielectric constant and stray capacitance, while maintaining chemical similarity for easy processing and avoiding diffusion issues during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-layer structure with electrode patterns on both major surfaces is used to achieve bidirectional varistor characteristics, then the device complexity increases due to the need for multiple paste applications and firings, but the reliability and functionality are improved through symmetrical surge protection in both directions
Solution Approach 1:
The varistor is divided into multiple functional layers: first internal electrode layers, first external electrode layers, insulating layers, and second internal electrode layers. Each layer serves a specific function in achieving bidirectional protection while maintaining manufacturing feasibility through systematic segmentation of the structure.
Solution Approach 2:
The patent implements a nested structure where insulating layers are positioned between internal electrode layers, and external electrodes are formed on the major surfaces. This nested arrangement allows multiple functional elements to be integrated within a compact multi-layer configuration, reducing overall device complexity while maintaining bidirectional functionality.
2Manufacturing precision
If conventional multi-layer fabrication processes with multiple paste applications and firings are used, then manufacturing precision can be maintained, but the productivity decreases due to the time-consuming sequential process steps
Solution Approach 1:
The patent merges multiple paste application and firing operations into a single integrated firing process. By designing the electrode patterns and insulating layers to be formed simultaneously during one firing cycle, the method eliminates sequential steps while maintaining the precision required for proper electrode alignment and pattern formation.
Solution Approach 2:
The insulating layers are designed with pre-defined patterns that guide the subsequent electrode formation. By preparing the insulating layer structure first with built-in alignment features, the electrode patterns can be accurately formed in a single firing step without requiring multiple alignment and firing operations, thus improving productivity while maintaining precision.
3Reliability
If symmetrical electrode patterns are formed on both major surfaces to achieve bidirectional characteristics, then the electrical performance is improved through balanced surge protection, but the manufacturing difficulty increases due to the complexity of forming precise patterns on multiple surfaces
Solution Approach 1:
The firing process is designed to serve multiple functions simultaneously: it forms insulating layers, creates electrode patterns on both major surfaces, and establishes proper electrical connections all in one operation. This multi-functional approach simplifies manufacturing by eliminating the need for separate processes for each function, making the production of symmetrical bidirectional patterns more manageable.
Solution Approach 2:
The insulating layers act as intermediaries that facilitate the formation of symmetrical electrode patterns. By positioning insulating layers with specific patterns between the internal electrode layers, the process enables precise alignment and symmetrical pattern formation on both surfaces during a single firing operation, reducing manufacturing difficulty while maintaining electrical performance.
Data Source
Figure 1~3
AI summary
The invention relates to a multi-layer varistor (1) comprising a ceramic body (2) having a large number of inner electrodes (5), the ceramic body (2) comprising an active region (3) and a near-surface region (4), and the ceramic body (2) comprising at least one first ceramic material (6) and at least one second ceramic material (7), the ceramic materials (6, 7) differing in a concentration of monovalent elements X+, where X+ = Li+, Na+, K+ or Ag+. The invention further relates to a method for producing a multi-layer varistor (1).