Power Module Package Adhesive Layout for Hermetic Thermal Stress Relief
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Solution Overview
Problem
Existing power semiconductor module packaging technologies face challenges in achieving prompt completion and maintaining hermeticity due to thermal expansion differences between the frame and heat sink plate, leading to potential gross leaks during temperature changes.
Innovation Solution
A package design featuring a heat sink plate, frame, and adhesive layer with a protruding portion and insert member, where the adhesive layer has varying thickness to accommodate thermal expansion, ensuring sufficient thickness for stress relief and preventing hermeticity deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the adhesive layer is made thin to reduce package size, then the package dimensions are reduced, but the adhesive layer cannot effectively relieve thermal stress caused by coefficient of thermal expansion differences between the frame and heat sink plate
Solution Approach 1:
The adhesive layer is designed with non-uniform thickness, featuring a thicker portion at the peripheral region and a thinner portion at the central region. This local quality variation allows the peripheral adhesive layer to effectively relieve thermal stress from coefficient of thermal expansion differences between the frame and heat sink plate, while maintaining overall compact package dimensions. The thicker peripheral region provides sufficient stress relief capability without requiring the entire adhesive layer to be thick.
Solution Approach 2:
The invention transitions from considering adhesive layer thickness as a single-dimensional parameter to a two-dimensional thickness distribution pattern. By varying the thickness across different regions (peripheral vs central), the solution addresses thermal stress relief requirements at the periphery while maintaining compact overall dimensions, effectively resolving the contradiction between package size and hermeticity.
2Reliability
If the adhesive layer is made thick to relieve thermal stress, then hermeticity is maintained under temperature changes, but the package size increases and completion time is extended
Solution Approach 1:
The adhesive layer thickness is optimized locally rather than uniformly throughout. The peripheral region has increased thickness to provide thermal stress relief and maintain hermeticity, while the central region maintains reduced thickness to minimize overall package size. This local differentiation resolves the contradiction by providing stress relief only where thermally induced stress concentrations occur at the frame-heat sink interface.
3Reliability
If the adhesive layer is made thick to relieve thermal stress, then hermeticity is maintained, but the manufacturing process time is extended
Solution Approach 1:
The non-uniform adhesive layer design with thicker peripheral regions and thinner central regions reduces the total volume of adhesive material required compared to a uniformly thick design. This reduction in adhesive volume decreases curing time and assembly time, thereby reducing manufacturing completion time while still providing sufficient thermal stress relief at the critical peripheral regions to maintain hermeticity.
4Reliability
If a uniform thick adhesive layer is used, then thermal stress is relieved, but the package structure becomes complex and manufacturing precision is reduced
Solution Approach 1:
The adhesive layer is designed with a simple yet effective thickness variation pattern: thicker at the periphery and thinner at the center. This creates a gradient structure that naturally accommodates thermal stress without requiring complex multi-layer or reinforced constructions. The simplicity of this thickness gradient design maintains manufacturing precision while providing effective thermal stress relief to preserve hermeticity.
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 solution allows for prompt completion of power semiconductor modules and maintains hermeticity by effectively relieving thermal stress, preventing gross leaks even under repeated temperature changes.
Implementation Method 1
the adhesive layer has a larger thickness between the frame and the heat sink plate than between the protruding portion and the heat sink plate. The sufficiently thick portion of the adhesive layer is elastically deformed to relieve stress caused by a difference in thermal expansion between the frame and the heat sink plate
Implementation Method 2
The sufficiently thick portion of the adhesive layer is elastically deformed to relieve stress caused by a difference in thermal expansion between the frame and the heat sink plate
Implementation Method 3
the heat sink plate supports the frame, has an unmounted region where the power semiconductor element is to be mounted within the frame in plan view, is made of metal
Data Source
AI summary
An external terminal electrode is attached to a frame, and the frame contains a first resin, and has a first adhered surface. A heat sink plate supports the frame, has an unmounted region where a power semiconductor element is to be mounted within the frame in plan view, is made of metal, and has a second adhered surface. An adhesive layer contains a second resin different from the first resin, and adheres the first adhered surface of the frame and the second adhered surface of the heat sink plate to each other. One of the first and second adhered surfaces includes a flat portion and a protruding portion. The protruding portion protrudes from the flat portion and opposes the other one of the first adhered surface and the second adhered surface with the adhesive layer therebetween.