Power Module Stress Relaxation Layer for SiC Bonding
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Solution Overview
Problem
The reliability of bonding in power modules with thick copper substrates is a concern, as existing methods, such as using Ag fired layers, lead to degradation under thermal cycles, increasing thermal resistance and reducing reliability.
Innovation Solution
A power module design incorporating a plate-shaped thick copper substrate with a conductive stress relaxation metal layer, specifically an aluminum relaxation layer, where the semiconductor device is bonded using a heating and pressurizing process, reducing thermal stress and enhancing bonding reliability without increasing thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thick copper substrate is used to reduce thermal resistance, then heat dissipation performance is improved, but bonding reliability deteriorates due to thermal stress between copper and SiC materials
Solution Approach 1:
An aluminum relaxation layer is introduced as an intermediary between the copper substrate and SiC semiconductor device. This intermediate layer has a coefficient of thermal expansion intermediate between copper and SiC, reducing thermal stress during temperature cycles and improving bonding reliability while maintaining the low thermal resistance of the thick copper substrate
Solution Approach 2:
The patent creates a composite structure consisting of copper substrate + aluminum relaxation layer + SiC semiconductor device. This multi-material composite approach allows each layer to contribute its optimal properties: copper for thermal conduction, aluminum for stress relaxation, and SiC for semiconductor functionality
2Ease of manufacture
If conventional bonding methods are used on thick copper substrates, then manufacturing process is simple, but bonding layer degrades under thermal cycles increasing thermal resistance
Solution Approach 1:
The aluminum relaxation layer is formed on the copper substrate before mounting the SiC semiconductor device. This preliminary action prepares the substrate with stress-relaxing properties in advance, preventing bonding layer degradation during subsequent thermal cycling without complicating the overall manufacturing process
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 proposed solution improves the bonding reliability of power modules by reducing thermal stress between copper and silicon carbide (SiC) materials, maintaining low thermal resistance and extending the lifespan of the bonding layer through the use of aluminum relaxation layers in the power module fabrication method.
Implementation Method 1
a conductive stress relaxation metal layer disposed on the thick copper substrate
Implementation Method 2
bonding the semiconductor device to the stress relaxation metal layer by a heating and pressurizing process that applies pressure while heating
Implementation Method 3
bonding the semiconductor device to the stress relaxation metal layer by a heating and pressurizing process that applies pressure while heating
Implementation Method 4
making such a substrate portion as a thick copper substrate has progressed in order to reduce a thermal resistance
Data Source
AI summary
A power module includes: a plate-shaped thick copper substrate, a conductive stress relaxation metal layer disposed on the thick copper substrate, a semiconductor device disposed on the stress relaxation metal layer, and a plated layer disposed on the stress relaxation metal layer, wherein the semiconductor device is bonded to the stress relaxation metal layer via the plated layer. The thick copper substrate includes a first thick copper layer and a second thick copper layer disposed on the first thick copper layer, and the stress relaxation metal layer is disposed on the second thick copper layer. A part of the semiconductor device is embedded to be fixed to the stress relaxation metal layer. A bonded surface between the semiconductor device and the stress relaxation metal layer are integrated to each other by means of diffusion bonding or solid phase diffusion bonding.