Laminated PTC Thermistor Grain Size Control

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Solution Overview

Problem

Conventional PTC thermistor elements face a challenge in achieving a balance between low room-temperature resistivity and high withstanding voltage, as high room-temperature resistivity ensures withstanding voltage performance but results in large power loss during normal use.

Innovation Solution

A laminated PTC thermistor element with a ceramic substrate having an average porcelain grain size of 0.3 to 1.2 μm and a relative density between 70% and −6.43d+97.83%, along with internal and external electrodes, is developed to balance room-temperature resistivity and withstanding voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the room-temperature resistivity is reduced to decrease power loss, then the withstanding voltage performance deteriorates

Engineering Contradiction:

Improvepower lossVSAvoidwithstanding voltage performance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the average porcelain grain size (0.3-1.2 μm) and relative density (70%-97.83%) of the barium titanate-based semiconductor porcelain to achieve optimal balance between room-temperature resistivity and withstanding voltage, resolving the trade-off through quantitative parameter optimization

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by formulating a multi-component barium titanate-based semiconductor porcelain system containing specific additives (such as rare earth elements, alkali metals, alkaline earth metals) that work synergistically to achieve both low resistivity and high withstanding voltage properties

Inventive Principle:

Principle #40Composite materials

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 solution enables a laminated PTC thermistor element that achieves a balance between low room-temperature resistivity and high withstanding voltage, effectively addressing the power loss and voltage performance trade-off, suitable for overcurrent protection in advanced electronic devices.

Implementation Method 1

laminated PTC thermistor element which has positive temperature characteristics

Methodology Applied

Scientific EffectPositive temperature coefficient (PTC) effect: Thermistor

Implementation Method 2

external electrodes formed on the surface of the ceramic substrate, for providing electrical conduction to the internal electrodes

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9530547B2Laminated PTC thermistor element

Publication Date: 2016.12.27 MURATA MFG CO LTD

AI summary

A laminated PTC thermistor element that includes a ceramic substrate including a plurality of ceramic layers, a plurality of internal electrodes within the ceramic substrate, and external electrodes on the surface of the ceramic substrate that provide electrical conduction to the internal electrodes. The ceramic substrate is 0.3 [μm] or more and 1.2 [μm] or less in average porcelain grain size. Furthermore, the relative density of the ceramic substrate has a lower limit of 70 [%], and an upper limit of −6.43d+97.83 [%] when the average porcelain grain size is denoted by d.