Ceramic Substrate Assembly With Stepped Edges for Thermal Stress Relief
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Solution Overview
Problem
Ceramic substrate units in electric vehicle inverters face challenges with thermal stress concentration at edge areas, leading to internal cracks and separation, which degrade the performance and reliability of the power module.
Innovation Solution
A ceramic substrate unit is designed with stair-shaped protrusions on the outer circumferential surfaces of both the upper electrode and the heat sink, which helps disperse thermal stress at the edge areas, preventing separation and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heat sink is provided on the ceramic substrate to dissipate heat, then heat dissipation performance is improved, but thermal stress concentration at edge areas causes internal cracks and separation
Solution Approach 1:
The heat sink and upper electrode are segmented with stair-shaped protrusions at their edges, creating multiple stepped levels instead of a single continuous edge. This segmentation distributes the thermal stress across multiple interfaces rather than concentrating it at one location, preventing crack propagation and separation while maintaining effective heat dissipation through the bonded structure.
2Ease of manufacture
If the edge area of the ceramic substrate is made vulnerable to thermal impact, then manufacturing simplicity is maintained, but internal cracks and separation easily occur
Solution Approach 1:
The stair-shaped protrusions create a curved, stepped profile at the edges of the heat sink and upper electrode instead of sharp angular edges. This curved geometry distributes thermal stress more evenly across the edge area, reducing stress concentration points that would lead to cracks, while the stepped structure maintains manufacturing feasibility through standard machining or molding processes.
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 stair-shaped protrusions effectively relieve thermal stress at the edge areas, minimizing bonding stress while maintaining bonding strength, thus ensuring the reliability and performance of the power module.
Implementation Method 1
there is a problem that internal cracks and separation easily occur... a ceramic substrate unit... in which a stair-shaped protrusion may be formed on an outer circumferential surface of each of an upper electrode and a heat sink, thereby relieving thermal stress concentrated on an edge area
Data Source
AI summary
The present invention relates to a ceramic substrate unit and a method for manufacturing same, the ceramic substrate unit comprising: a ceramic substrate comprising a ceramic base material and metal layers provided at the upper and lower surfaces of the ceramic base material; an upper electrode bonded to the upper metal layer of the ceramic substrate, formed to be mounted with a semiconductor chip, and having a first stepped protrusion formed at the outer circumferential surface thereof; and a heat sink bonded to the lower metal layer of the ceramic substrate and having a second stepped protrusion formed at the outer circumferential surface thereof. Accordingly, the present invention can relieve thermal stress.