Electronic Component Module Design for Thermal Stress Reduction

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Solution Overview

Problem

In electronic-component-mounted modules, thermal stress due to differences in linear expansion coefficients between aluminum or copper components and electronic components can lead to cracking, especially under temperature changes, and silver-sintered bonding layers, while providing better high-temperature reliability, can be overly stressed and break the components.

Innovation Solution

The module incorporates silver-sintered bonding layers on both surfaces of electronic components with insulation circuit substrate boards and lead frames made of materials with lower linear expansion coefficients, such as copper alloys or ceramics, ensuring a difference in linear expansion coefficient of no more than 5 ppm/°C to reduce thermal stress and enhance bonding reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aluminum or copper components are used for the circuit layer and lead frame, then electrical conductivity is improved, but thermal stress is generated due to larger linear expansion coefficient compared to electronic components

Engineering Contradiction:

Improvebonding reliabilityVSAvoidthermal stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent changes the material parameter (linear expansion coefficient) of the lead frame from traditional copper/aluminum to a low linear expansion coefficient material. This parameter change resolves the contradiction by reducing thermal stress while maintaining electrical conductivity through alternative material selection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structure by bonding copper or copper alloy circuit layer and lead frame onto a substrate with low linear expansion coefficient. This composite approach allows the assembly to have both good electrical conductivity (from copper) and reduced thermal stress (from the low expansion substrate).

Inventive Principle:

Principle #40Composite materials

2Reliability

If silver-sintered bonding layer is used instead of soldering, then bonding reliability in high temperature environment is improved, but the bonding layer becomes thinner and harder, causing larger thermal stress on the electronic component

Engineering Contradiction:

Improvebonding reliability in high temperatureVSAvoidthermal stress on electronic component

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent changes the material composition parameter of the silver-sintered bonding layer by adding copper or copper alloy particles to the silver powder. This modification maintains the high-temperature bonding reliability of silver while reducing hardness and thermal stress through the softer copper phase.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the difference in linear expansion coefficient between insulation circuit substrate board and lead frame is large, then manufacturing flexibility is improved, but thermal stress in the electronic component increases

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidthermal stress in electronic component

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The patent establishes a specific parameter range for the difference in linear expansion coefficient (not more than 5 ppm/°C) between the insulation circuit substrate board and lead frame. This parameter control resolves the contradiction by limiting thermal stress while allowing manufacturing flexibility within the specified range.

Inventive Principle:

Principle #35Parameter changes

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 configuration improves bonding reliability and thermal conductivity, reducing the likelihood of component breakage by minimizing thermal stress and maintaining integrity under varying temperatures.

Implementation Method 1

Heat generated in the electronic component can be quickly released since thermal conductivity of the silver-sintered bonding layers is excellent

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

aluminum, aluminum alloy, copper, and copper alloy used for the circuit layer and the lead frame have larger linear expansion coefficient than that of the electronic component. Therefore, in a case in which the electronic component and the lead frame are mounted on the circuit layer by soldering, owing to change in usage environment and resistance heat of the electronic component and the like, thermal stress is generated in solder bonding layers

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11315868B2Electronic-component-mounted module design to reduce linear expansion coefficient mismatches

Publication Date: 2022.04.26 MITSUBISHI MATERIALS CORP

AI summary

An electronic-component-mounted module has an electronic component, a first silver-sintered bonding layer bonded on one surface of the electronic component, a circuit layer made of copper or copper alloy and bonded on the first silver-sintered bonding layer, and a ceramic substrate board bonded on the circuit layer, and further has an insulation circuit substrate board with smaller linear expansion coefficient than the electronic component, a second silver-sintered bonding layer bonded on the other surface of the electronic component, and a lead frame with smaller linear expansion coefficient than the electronic component bonded on the second silver-sintered bonding layer; and a difference in the linear expansion coefficient between the insulation circuit substrate board and the lead frame is not more than 5 ppm/° C.