Semiconductor Device Buffer Member Stress Relaxation
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Solution Overview
Problem
Semiconductor devices with power conversion capabilities face reliability issues due to internal stress generated by temperature changes, caused by differing linear expansion coefficients between the case and sealing member, leading to peeling and decreased power cycle endurance.
Innovation Solution
Incorporating a buffer member with a lower elastic modulus than the case and sealing member, and a low expansion member with a smaller linear expansion coefficient than both, to mitigate internal stress by relaxing expansion and contraction differences, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the case and sealing member have different linear expansion coefficients, then the sealing function is maintained, but internal stress increases with temperature changes
Solution Approach 1:
The buffer member serves as a stress-absorbing intermediary between the case and sealing member. It has mechanical properties (elastic modulus and linear expansion coefficient) that are intermediate between the two components, allowing it to absorb differential thermal expansion stress through elastic deformation. This mediator approach prevents stress concentration at the case-sealing member interface while maintaining the sealing function.
Solution Approach 2:
The buffer member provides beforehand cushioning by being pre-installed between the case and sealing member to absorb thermal expansion stress before it can cause damage. The elastic deformation capability of the buffer member acts as a cushion that mitigates the impact of thermal cycling on the bonding interface, preventing peeling and maintaining reliability over temperature cycles.
2Stress or pressure
If the buffer member has low elastic modulus, then stress is relaxed, but the structural strength may be reduced
Solution Approach 1:
The patent optimizes the elastic modulus parameter of the buffer member to achieve a balance between stress relaxation and structural strength. The elastic modulus is controlled within a specific range that allows sufficient elastic deformation for stress absorption while maintaining adequate structural strength to support the sealing function. This parameter optimization ensures the buffer member can both relax internal stress and maintain structural integrity.
Solution Approach 2:
The buffer member may be constructed from composite materials that combine different components to achieve the desired balance between elastic modulus and strength. By using composite materials, the buffer member can exhibit tailored mechanical properties that provide both stress relaxation capability and sufficient structural strength, overcoming the trade-off between these two properties.
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 configuration effectively suppresses internal stress and maintains reliability against temperature changes, preventing peeling and ensuring consistent performance.
Implementation Method 1
Different resins are used for the case and the sealing member included in the above semiconductor device, and the linear expansion coefficient is therefore different between the case and the sealing member. Therefore, an internal stress is generated in the semiconductor device as the temperature changes.
Data Source
AI summary
A semiconductor device includes: a semiconductor chip; a case having a frame portion that has an inner wall portion surrounding an housing area in which the semiconductor chip is disposed; a buffer member provided on at last part of the inner wall portion of the case on a side of the housing area; a low expansion member provided on said at least part of the inner wall portion with the buffer member interposed therebetween on the side of the housing area; and a sealing member that seals the housing area, wherein the buffer member has a smaller elastic modulus than the case and the sealing member, and wherein the low expansion member has a smaller linear expansion coefficient than the case and the sealing member.