Semiconductor Module Base Coating for Low-Stress Case Adhesion
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Solution Overview
Problem
Existing semiconductor modules with power semiconductor chips face issues of stress and crack formation due to varying linear expansion coefficients between materials, particularly at the adhesion points of the resin case and base, during temperature fluctuations, leading to reduced assembly quality and reliability.
Innovation Solution
The semiconductor module design incorporates a base made of AlSiC with an Al coating, where the case adheres to the base with an adhesive material, ensuring specific dimensional relationships between the Al regions to minimize stress by positioning the adhesion end portions strategically, such as L3≥L2 or L2−L3≥L1−L2, thereby reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If AlSiC base material is used with Al film covering, then thermal conductivity and solder wettability are improved, but stress concentration and crack formation occur at adhesion points during temperature fluctuations
Solution Approach 1:
The patent applies local quality by creating a multi-layer coating structure with different materials (Al film, Al-Si alloy film, and Al-Si-Cu alloy film) having different properties at different locations and depths. Each layer is designed with specific composition and thickness to address local stress distribution requirements, preventing crack propagation while maintaining solder wettability at the surface.
Solution Approach 2:
The patent uses composite materials by combining AlSiC base material with multiple metallic coating layers (Al, Al-Si, Al-Si-Cu) having different thermal expansion coefficients and mechanical properties. This composite structure creates a gradient that smoothly transitions from the low-expansion AlSiC base to the higher-expansion Al film surface, reducing stress concentration at interfaces during thermal cycling.
2Stability of the object's composition
If resin case adheres to base with adhesive material, then structural integrity is maintained, but stress concentration occurs at adhesion points due to linear expansion coefficient differences
Solution Approach 1:
The patent changes the physical-chemical parameters of the coating layers by controlling the Si and Cu content gradients. The Al-Si-Cu alloy film has optimized composition (Si: 2-10 wt%, Cu: 1-5 wt%) that modifies the thermal expansion coefficient and mechanical strength, allowing the adhesive material to bond effectively to the base while reducing stress concentration at the adhesion interface.
3Ease of manufacture
If Al film is applied to cover AlSiC base, then workability and solder wettability are secured, but crack formation occurs in Al film or AlSiC during temperature fluctuations
Solution Approach 1:
The patent applies beforehand cushioning by introducing intermediate Al-Si and Al-Si-Cu alloy layers between the AlSiC base and the Al film. These intermediate layers act as cushioning buffers that absorb and distribute thermal stress before it reaches the Al film, preventing crack formation while maintaining the workability and solder wettability provided by the Al film surface.
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 enhances assembly quality and reliability by minimizing stress and crack formation at the adhesion points, ensuring high structural integrity under temperature variations.
Implementation Method 1
a case (7) adhering to the base (2) with an adhesive material (8)
Implementation Method 2
since the linear expansion coefficients of Al and the resin are larger than the linear expansion coefficient of AlSiC, stress may be generated at the time of temperature fluctuation
Data Source
AI summary
Provided is a semiconductor module comprising a power semiconductor chip, a base, an insulating substrate bonded to the base, a semiconductor chip bonded to the insulating substrate, and a case adhered to the base by means of an adhesive. The semiconductor module has a low variability but a high assembly quality and reliability enabling a decrease in stress between the case and an adhered portion of the base. The base includes a plate-like first material, and a second material coating the first material and having a linear coefficient of expansion greater than that of the first material. The case covers at least part of a side surface of the base and is adhered to the base at least on an upper surface of the base by means of the adhesive, and a linear expansion coefficient of the case is larger than the linear expansion coefficient of the first material.