Power Module Tilted Substrate Stress Distribution
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Solution Overview
Problem
Conventional power modules experience stress-induced deformation and cracking of the resin case due to screw axial forces, leading to failures in breakdown voltage and electrical property fluctuations when attaching a heat dissipation substrate to a cooling fin.
Innovation Solution
A power module design featuring a heat dissipation substrate with a tilted part at its end, which is pressed against a cooling fin using a pressure structure, reducing deformation and stress concentration in the resin case by distributing the force across multiple contact points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the heat dissipation substrate is fixed to the cooling fin using a resin case with screw axial force, then the heat dissipation substrate is securely attached to the cooling fin, but the resin case deforms and causes cracks in the resin filling
Solution Approach 1:
A pressure member is introduced as an intermediary component between the resin case and the heat dissipation substrate. The pressure member has a pressing surface that contacts the heat dissipation substrate and transmits the screw axial force, preventing direct stress concentration on the resin case. This mediator distributes the force and eliminates the deformation and cracking problems of the resin case while maintaining secure attachment.
Solution Approach 2:
The resin case is designed with a pressing projection that extends toward the heat dissipation substrate before assembly. This preliminary structural preparation ensures that when the screw axial force is applied, the force is already directed through the predetermined pressing projection to the heat dissipation substrate, preventing deformation of the resin case during the attachment process.
2Strength
If the resin case is used to press the heat dissipation substrate against the cooling fin, then the heat dissipation substrate is fixed, but the resin case deformation causes failure in breakdown voltage
Solution Approach 1:
The pressure member serves as a mediator that separates the mechanical stress path from the resin case. By transmitting the pressing force through the pressure member's pressing surface directly to the heat dissipation substrate, the resin case is protected from deformation that would otherwise compromise the breakdown voltage of the resin filling.
3Force
If screw axial force is applied to fix the heat dissipation substrate, then the attachment is secure, but the resin case deforms under the stress
Solution Approach 1:
The pressure member is positioned between the resin case and the heat dissipation substrate to intercept and redistribute the screw axial force. The pressing surface of the pressure member contacts the heat dissipation substrate, allowing the full attachment force to be applied without deforming the resin case, thus preserving its shape while maintaining secure fixation.
Solution Approach 2:
The resin case is pre-formed with a pressing projection that creates a predetermined force transmission path. This preliminary structural arrangement ensures that when screw axial force is applied, the force follows the intended path through the projection to the heat dissipation substrate, preventing unintended deformation of the resin case.
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 design effectively suppresses the occurrence of cracks in the resin filling, maintaining electrical integrity and stability under torque, while also enhancing heat transfer and reducing manufacturing complexity.
Implementation Method 1
press the heat dissipation substrate against the cooling fin... distributing the stress and preventing deformation of the resin case
Implementation Method 2
enhancing heat transfer through the pressure member
Data Source
AI summary
In a power module, a power semiconductor element is mounted on a heat dissipation substrate having a tilted part formed at an end portion thereof, a resin case is arranged so as to surround the power semiconductor element and to contact the heat dissipation substrate, and a cooling fin is arranged so as to contact a surface of the heat dissipation substrate opposite a surface of the heat dissipation substrate on which the power semiconductor element is mounted. The power module includes pressure member contacting the tilted part of the heat dissipation substrate to press the heat dissipation substrate against the cooling fin.