Fusible Electrode Connection for Thermal-Stress-Protected Ceramic Components

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Solution Overview

Problem

Components experiencing inhomogeneous or asymmetric heating due to different thermal expansion coefficients can suffer mechanical stresses, leading to damage, such as fractures in connecting materials or external electrodes, especially in ceramic components with metal electrodes.

Innovation Solution

A component design featuring a connecting material with a melting point lower than the critical temperature, ensuring the connection between the main body and external electrode melts before reaching the critical temperature, thereby dissipating mechanical stresses, and resolidifying to reestablish the connection after cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the component is heated to high temperatures, then the functional performance is improved, but mechanical stresses arise due to thermal expansion differences leading to damage

Engineering Contradiction:

Improveoperating temperatureVSAvoidconnection integrity

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The connecting material is selected to melt at a temperature below the critical temperature to prevent damage. This preliminary protective action occurs before the critical temperature is reached, eliminating mechanical stresses by transitioning the connecting material from solid to liquid state, thereby preventing fracture of external electrodes or ceramic substrates.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the physical state parameter of the connecting material from solid to liquid by selecting a melting point below the critical temperature. This parameter change eliminates mechanical stresses that would otherwise cause damage, allowing the component to operate safely at high temperatures without compromising connection integrity.

Inventive Principle:

Principle #35Parameter changes

2Strength

If a connecting material with high melting point is used, then the connection strength is improved, but the component becomes vulnerable to thermal stress damage at high temperatures

Engineering Contradiction:

Improveconnection strengthVSAvoidthermal stress

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The invention converts the potentially harmful high melting point property into a beneficial protective feature by selecting a connecting material whose melting point is deliberately set below the critical temperature. The melting action, which might seem to weaken the connection, actually protects the component by eliminating thermal stresses that would cause more severe damage at higher temperatures.

Inventive Principle:

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

Solution Approach 2:

The connecting material acts as a protective cushion by melting before the critical temperature is reached. This preliminary protective mechanism absorbs and eliminates thermal stresses before they can cause damage to the external electrodes or ceramic substrate, similar to a safety fuse that protects the main system.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Object-affected harmful factors

If the connecting material melts, then mechanical stresses are eliminated, but the electrical connection is temporarily interrupted

Engineering Contradiction:

Improvemechanical stressVSAvoidelectrical continuity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The connecting material acts as a sacrificial, short-living protective element that melts temporarily to eliminate mechanical stresses. Although this temporarily interrupts the electrical connection, the liquid connecting material prevents stress transmission, and the connection can be restored when the component cools down, making the temporary disruption an acceptable trade-off for preventing permanent damage.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

Prevents damage from mechanical stresses during heating by melting the connecting material before critical temperatures are reached, ensuring the component remains functional and intact, with a solder material like tin-bismuth being particularly effective in maintaining reliable electrical and mechanical connections.

Implementation Method 1

The connecting material has a melting point which is lower than the critical temperature. Due to the fact that the state of the matter of the connecting material can change from solid to liquid before a critical temperature is attained

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

The main body and the external electrode have different coefficients of thermal expansion which determine a critical temperature which when exceeded results in a connection between the main body and the external electrode experiencing mechanical stresses

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11875925B2Thermistor, varistor or capacitor component with a fusible connecting element between the main body of the component

Publication Date: 2024.01.16 TDK ELECTRONICS AG

AI summary

An electrical component comprises a main body and at least one external electrode that is fastened by a connecting material to the main body. The main body and the external electrode have different coefficients of thermal expansion that determine a critical temperature which, when exceeded, results in a connection between the main body and the external electrode experiencing mechanical stresses that lead to damage to the component. The connecting material has a melting point which is lower than a critical temperature.