Gradient Electrode Layers for Varistor Bonding and Cost Reduction
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Solution Overview
Problem
Conventional varistor electrode fabrication using silk-screen printing results in environmental pollution, high production costs due to precious silver usage, low bonding strength, high-resistance ohmic contact, and poor corrosion resistance against lead-free solder, leading to reliability issues.
Innovation Solution
The electrode component features two or more base metal materials or alloys with concentration gradients, sequentially stacked and formed using a spray forming process, integrated with a ceramic substrate and insulating layer to enhance bonding strength and solderability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional silk-screen printing process with organic silver paste is used, then electrode layer can be formed, but toxic substances cause serious environmental pollution
Solution Approach 1:
The patent extracts and removes the harmful organic binder from the traditional silver paste formulation, replacing it with a water-based or alcohol-based binder system. This extraction of the toxic component eliminates environmental pollution while maintaining the electrode formation capability through alternative binding mechanisms.
Solution Approach 2:
The patent replaces expensive organic silver paste with a more economical inorganic-based electrode material system that uses water or alcohol as binder. This substitution with cheaper, environmentally benign materials achieves the same functional result without the harmful byproducts of organic paste decomposition.
2Reliability
If thick silver layer is adopted to increase surge-withstanding capability, then electrode performance improves, but production cost increases due to precious silver material
Solution Approach 1:
The patent employs composite electrode structures combining multiple metal layers with different functional properties. A thin silver layer provides necessary conductivity and surge protection, while underlying base metal layers (copper, nickel, or palladium) provide mechanical strength and cost reduction. This composite approach achieves surge-withstanding capability with minimal precious metal consumption.
Solution Approach 2:
The patent applies silver material selectively only where electrically critical, rather than uniformly throughout the entire electrode structure. The silver is concentrated in specific functional zones where surge protection is needed, while other areas use cheaper base metals, optimizing both performance and cost efficiency.
3Ease of manufacture
If conventional silk-screen printing process is used, then electrode layer can be formed, but bonding strength is low due to silver-ceramic incompatibility
Solution Approach 1:
The patent introduces intermediate metal layers (such as nickel or palladium) between the silver electrode and ceramic substrate. These intermediary layers serve as chemical and mechanical bridges, providing excellent adhesion to the ceramic while maintaining electrical conductivity, thereby resolving the incompatibility between silver and ceramic materials.
Solution Approach 2:
The patent creates a multi-layer composite electrode structure where each layer is specifically selected for its bonding properties to adjacent materials. The gradient from ceramic-adherent base metal layers to silver conductive layers ensures strong overall bonding while maintaining electrical function.
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
This approach reduces production costs, minimizes environmental pollution, and improves bonding strength and solderability, reducing the risk of electrode separation during high-voltage discharges while maintaining original electrical characteristics.
Implementation Method 1
a process of spray-forming the electrode layers (3)
Data Source
AI summary
An electrode component includes a ceramic substrate, two electrode layers formed on two opposite surfaces of the ceramic substrate, two pins respectively connected to the two electrode layers, and an insulating layer enclosing the ceramic substrate, the electrode layers and a portion of each pin. Each electrode layer is formed of two or more base metal materials or alloys thereof, and the concentrations of the base metal materials progressively vary across the electrode layer. Accordingly, the production cost is lowered, environmental pollution caused by evaporation and thermal dissolution of organic solvent can be prevented, risk of separable electrode interface at high-voltage discharge is mitigated, and the fabrication process of the electrode layer is shortened while maintaining bonding strength between the electrode layers and the ceramic substrate and solderability between the electrode layers and the pins.