Piezoelectric Substrate for Power Electronic Device Thermal Stress

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Solution Overview

Problem

Thermal stresses caused by coefficient of thermal expansion mismatch between metal and semiconductor substrates in power electronic devices lead to cyclic strain and fatigue failure in bonding materials, particularly as operating temperatures increase.

Innovation Solution

Attaching a piezoelectric substrate to the metal substrate, which generates mechanical strain in response to electric current, thereby canceling out or reducing the thermal strain on the metal substrate, and incorporating a controller to manage voltage based on temperature measurements to prevent deformation and fatigue in the bonding layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the operating temperature of the power electronic device increases, then the power electronic device can operate at higher temperatures, but thermal stresses caused by CTE mismatch between the metal substrate and the semiconductor device increase, leading to cyclic strain and fatigue failure in bonding material

Engineering Contradiction:

Improveoperating temperatureVSAvoidbonding material reliability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent applies parameter changes by utilizing the piezoelectric effect to dynamically adjust the mechanical strain state of the metal substrate. By applying voltage to the piezoelectric substrate, the system changes the physical parameters (strain) of the metal substrate to counteract thermal stresses, thereby preventing bonding material failure while maintaining high operating temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by integrating a piezoelectric substrate with the metal substrate to create a combined structure. This composite system allows the piezoelectric material to generate mechanical strain in response to electrical input, which compensates for thermal expansion mismatch between the metal and semiconductor substrates during temperature cycling

Inventive Principle:

Principle #40Composite materials

2Reliability

If a piezoelectric substrate is attached to the metal substrate to reduce thermal stress, then bonding material reliability improves, but device complexity increases

Engineering Contradiction:

Improvebonding material reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The piezoelectric substrate serves multiple functions: it acts as a stress-compensating element during thermal cycling, provides a platform for temperature sensing, and enables active control of metal substrate strain. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while improving bonding material reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Stress or pressure

If voltage is applied across the piezoelectric substrate to generate mechanical strain, then thermal stress on the metal substrate is reduced, but energy consumption increases

Engineering Contradiction:

Improvethermal stressVSAvoidenergy consumption

Core Design Contradiction:

Stress or pressureVSUse of energy by moving object

Solution Approach 1:

The system applies periodic voltage pulses to the piezoelectric substrate that correspond to the thermal cycling pattern of the power electronic device. By synchronizing the piezoelectric compensation action with the thermal stress cycles, the system reduces average energy consumption while maintaining effective stress mitigation during critical temperature transitions

Inventive Principle:

Principle #19Periodic action

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 system effectively reduces the likelihood of cyclic strain and fatigue failure in the bonding layer by mitigating thermal stresses, and also enables monitoring for defects by detecting changes in voltage across the piezoelectric substrate.

Implementation Method 1

The piezoelectric substrate is configured to generate a mechanical strain in response to electric current passing through the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

When the operating temperature of the power electronic device increases, thermal stresses caused by coefficient of thermal expansion (CTE) mismatch between the metal substrate and the semiconductor device increase

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10461668B2Systems for protecting and monitoring power electronic devices

Publication Date: 2019.10.29 TOYOTA JIDOSHA KK

AI summary

A system for protecting a power electronic device is provided. The system includes a power electronic device and a controller. The power electronic device includes a piezoelectric substrate, a metal substrate coupled to the piezoelectric substrate, a semiconductor device, and a bonding layer positioned between the metal substrate and the semiconductor device such that the metal substrate is bonded to the semiconductor device. The controller includes a power supply, one or more processors, and one or more memory modules storing computer readable and executable instructions. The computer readable and executable instructions, when executed by the one or more processors, cause the controller to: receive a temperature of the power electronic device, and provide a voltage determined based on the temperature of the power electronic device across the piezoelectric substrate.