Semiconductor Module Encapsulant Thermal Expansion Matching
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Solution Overview
Problem
Existing methods for producing semiconductor modules with power electronic assemblies often result in undesirable phenomena such as delamination or destruction of contacting elements like bonding wires due to thermal expansion mismatches between encapsulating compounds and ceramic circuit carriers.
Innovation Solution
A method involving a semiconductor module with a ceramic circuit carrier made from aluminum oxide, aluminum nitride, or silicon nitride, covered by an encapsulating compound with a thermal expansion coefficient of 2 to 10 ppm/K, formed using a magnesium phosphate cement mixture, which includes inorganic additives and particles for enhanced thermal conductivity and tensile strength, and applied as a 'glob-top' encapsulation to partially or fully cover bonding wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional organic encapsulating compounds are used, then ease of manufacture is improved, but thermal expansion mismatch causes delamination and bonding wire destruction
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the encapsulating compound by using magnesium phosphate cement with a thermal expansion coefficient of 2-10 ppm/K, which matches the ceramic circuit carrier. This parameter adjustment eliminates thermal expansion mismatch while maintaining manufacturability through standard casting processes.
Solution Approach 2:
The patent employs a composite material system consisting of magnesium phosphate cement combined with inorganic additives and particles. This composite provides both the matched thermal expansion coefficient and the necessary mechanical properties, achieving reliability without sacrificing ease of manufacture.
2Reliability
If inorganic encapsulating compounds are used, then thermal expansion matching is improved, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the manufacturing process by adjusting the thermal expansion parameter through material selection (magnesium phosphate cement) rather than complex multi-layer structures. The single-phase cement-based compound achieves thermal matching without increasing device complexity.
3Ease of operation
If organic encapsulating compounds are used, then ease of application is improved, but adhesion and heat dissipation are insufficient
Solution Approach 1:
The patent uses a composite material system where magnesium phosphate cement provides strong adhesion to both ceramic and metal surfaces, while inorganic particles enhance heat dissipation. The mixture maintains ease of application through its castable mass form similar to conventional encapsulants.
Solution Approach 2:
The patent changes the material composition from organic to inorganic cement-based compound, which fundamentally improves adhesion strength and heat dissipation capability while maintaining ease of operation through similar application methodologies.
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 effectively prevents delamination and enhances the longevity of semiconductor modules by matching thermal expansion coefficients, improving heat dissipation and adhesion, thereby reducing the risk of bonding wire destruction and ensuring reliable operation under high power conditions.
Implementation Method 1
the encapsulating compound (30) has a thermal expansion coefficient in the range from 2 to 10 ppm/K and wherein the ceramic of the ceramic circuit carrier (50) is selected from the group consisting of ceramics based on aluminum oxide, aluminum nitride or silicon nitride
Implementation Method 2
comprising the formation of the hardened inorganic cement by the steps: (1) mixing a powdered mixture of inorganic binder and inorganic additives with water to form a castable mass, (2) casting the castable mass thus formed, and (3) subsequently setting and drying the cast mass
Implementation Method 3
improving heat dissipation and adhesion, thereby reducing the risk of bonding wire destruction
Data Source
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Figure 5
AI summary
Semiconductor module (10) with a ceramic circuit carrier (50) carrying at least one semiconductor component (20), wherein the at least one semiconductor component (20) is covered by a coating material (30), characterized in that the coating material (30) comprises a cured inorganic cement and has a coefficient of thermal expansion in the range of 2 to 10 ppm/K and wherein the ceramic of the ceramic circuit carrier (50) is selected from the group consisting of ceramics based on aluminum oxide, aluminum nitride or silicon nitride.