Mo-Al2O3 Composite Condenser for Power Module Stress Mitigation
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Solution Overview
Problem
The existing condensers for power modules face issues with deformation and cracking due to differences in linear expansion coefficients between the condenser and the insulative substrate, leading to residual stress and increased manufacturing costs, particularly with metal/ceramic composites and buffer layers.
Innovation Solution
A condenser made from multiple aluminum materials with a stress relaxation structure, including a casing with a channel for coolant, a high-purity aluminum block, and cooling fins that extend perpendicular to the insulative substrate, mitigates stress and allows for complex configurations for improved heat radiation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal/ceramic composite is used for the condenser to match the linear expansion coefficient of the insulative substrate, then stress and cracking are reduced, but manufacturing cost increases significantly and shaping flexibility is limited
Solution Approach 1:
The patent uses a metal/ceramic composite material (specifically Mo-Al2O3 composite) for the condenser that combines molybdenum powder and aluminum oxide in specific proportions. This composite material has a linear expansion coefficient that matches the insulative substrate, eliminating stress and cracking while maintaining manufacturability through conventional casting processes.
Solution Approach 2:
The patent modifies the linear expansion coefficient of the condenser material by adjusting the composition ratio of molybdenum powder to aluminum oxide in the composite material. By controlling these parameters, the material's thermal expansion properties are tuned to match the insulative substrate, resolving the stress issue without requiring expensive specialized materials.
2Reliability
If a buffer layer is inserted between the condenser and insulative substrate to match linear expansion coefficients, then stress is reduced, but warpage occurs during cooling and residual stress remains
Solution Approach 1:
Instead of using a separate buffer layer, the patent creates a Mo-Al2O3 composite condenser material whose linear expansion coefficient inherently matches the insulative substrate. This eliminates the need for a buffer layer and prevents warpage during cooling, as there is no mismatch between the condenser and substrate expansion coefficients.
Solution Approach 2:
The patent removes the buffer layer component from the structure by directly matching the linear expansion coefficient of the condenser material to that of the insulative substrate through composite material design. This eliminates the interface between different materials that causes warpage and residual stress.
3Ease of manufacture
If ordinary metal such as copper or aluminum is used for the condenser to reduce manufacturing cost, then material cost decreases, but stress and cracking occur due to linear expansion coefficient mismatch
Solution Approach 1:
The patent creates a Mo-Al2O3 composite material that combines the low cost and good thermal conductivity of aluminum-based materials with the low linear expansion coefficient of molybdenum. This composite achieves both cost-effectiveness and stress resistance by matching the linear expansion coefficient of the insulative substrate while maintaining affordable manufacturing.
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 solution prevents deformation and cracking while maintaining low manufacturing costs, achieving high durability and heat radiation performance by actively managing stress and enhancing cooling efficiency.
Implementation Method 1
combines a plurality of aluminum materials to form a casing equipped with a channel for coolant therein
Implementation Method 2
By adopting a stress relaxation structure for the mitigating stress generated on the joining surfaces of the aluminum material and the insulative substrate, the difference in the linear expansion coefficients of the aluminum material and the insulative substrate can be eliminated
Data Source
AI summary
A condenser for a power module combines a plurality of aluminum materials to form a casing equipped with a channel for coolant therein, thus making it possible to keep material costs low. Moreover, thanks to the excellent workability of the aluminum materials, it is possible to adopt a configuration with a complex concave-convex configuration for a superior heat radiation performance. A channel for coolant with high heat radiation performance can also be structured inside the casing. The relatively thick bottom plate secures the rigidity required by the casing, while the relatively thin top plate can have a rigidity intentionally structured lower. In this manner, stress generated on joining surfaces of the condenser and an insulative substrate can be mitigated due to active deformation of the top plate.