Striped Internal Electrode Layout for Surge-Resistant Laminated Varistors

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Solution Overview

Problem

Conventional laminated varistors face degradation due to heat generation when handling large surge currents, leading to reduced surge resistance and potential failure in protecting semiconductor circuits from lightning and static electricity.

Innovation Solution

A laminated varistor design featuring alternating layers of ZnO varistor layers and Ag internal electrodes, with strategically arranged electrode strips and spaces to enhance heat dissipation and prevent delamination, while maintaining the number of varistor layers to maximize surge resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large surge current flows through the varistor, then the protective function is improved, but heat generation increases causing characteristics to deteriorate

Engineering Contradiction:

Improvesurge resistanceVSAvoidheat generation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The internal electrode is divided into multiple electrode strips arranged in parallel, which segments the current path and distributes the heat generation across multiple regions. This segmentation prevents localized overheating while maintaining the overall surge protection capability of the varistor.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Spaces are provided between adjacent electrode strips to create local regions with different thermal and electrical properties. These spaces facilitate heat dissipation pathways and prevent heat accumulation at critical locations, thereby improving the varistor's ability to handle surge currents without characteristic deterioration.

Inventive Principle:

Principle #3Local quality

2Reliability

If the number of varistor layers is increased to improve surge resistance, then the protective capability is enhanced, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvesurge resistanceVSAvoidnumber of layers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple electrode strips are combined into a single internal electrode structure that functions as one integrated component. This merging approach maintains the surge protection effectiveness of multiple layers while simplifying the manufacturing process by reducing the number of separate electrode components that need to be assembled.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The internal electrode with multiple electrode strips serves multiple functions simultaneously: it provides electrical connection, distributes current across the varistor layers, and facilitates heat dissipation. This multi-functionality reduces the need for additional components and simplifies the overall device structure.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If electrode strips are arranged closely to maximize active area, then surge resistance is improved, but heat dissipation becomes insufficient causing local temperature rise

Engineering Contradiction:

Improvesurge resistanceVSAvoidlocal temperature rise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Spaces are strategically provided between adjacent electrode strips to create local heat dissipation regions. These spaces have different thermal properties compared to the electrode material, allowing heat to be dissipated more effectively at critical locations while maintaining close spacing for maximum active area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The spaces between electrode strips, which reduce the active area, are converted into beneficial heat dissipation pathways. These spaces allow heat generated during surge events to be conducted away more effectively, transforming what would be a harmful concentration of heat into a beneficial cooling mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively disperses heat generated during surge events, preventing local temperature rises and improving surge-resistant characteristics without reducing the number of effective varistor layers, thus enhancing the varistor's ability to protect electronic circuits.

Implementation Method 1

The design effectively disperses heat generated during surge events, preventing local temperature rises

Methodology Applied

Scientific EffectHeat dissipation: Conduction (thermal)

Data Source

PatentUS11791072B2Laminated varistor

Publication Date: 2023.10.17 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A laminated varistor includes a varistor layer, a first internal electrode provided on an upper surface of the varistor layer, a second internal electrode provided on a lower surface of the varistor layer and facing the first internal electrode across the varistor layer in upward and downward directions, a first external electrode provided on a first side surface of the varistor layer and electrically connected to the first internal electrode, and a second external electrode provided on a second side surface of the varistor layer and electrically connected to the second internal electrode. The first internal electrode is extended from the first external electrode in a first extension direction. The first internal electrode includes first electrode strips arranged in a first arrangement direction perpendicular to the first extension direction and spaced apart from one another. This laminated varistor has improved surge-resistant characteristics.