Semiconductor Device Recessed Metal Layer Thermal Stress
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Solution Overview
Problem
Semiconductor devices used for power conversion experience damage and failure due to thermal history-related stress concentration at the interface between semiconductor elements and bonding materials, leading to increased resistance and reduced heat-dissipating ability over time.
Innovation Solution
A semiconductor device with a recessed metal layer on an insulated circuit board that accommodates the bonding material at the corners of the semiconductor element, reducing stress concentration by forming a fillet that avoids contact with the insulating board, thereby minimizing thermal expansion differences and associated stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bonding material covers the entire back surface of the semiconductor element including corners, then the bonding strength is improved, but thermal history-related stress concentration occurs at the interface edges leading to reduced reliability
Solution Approach 1:
The patent applies local quality by creating a recess at the corner portion of the metal layer, making the corner region structurally different from the rest of the surface. This localized modification allows the bonding material to be accommodated in a way that reduces stress concentration at the interface edges while maintaining adequate bonding coverage, thus improving interface durability without significantly compromising overall bonding strength.
2Area of stationary object
If the bonding material extends to the edges of the metal layer, then the bonding area is maximized, but stress concentration at the interface edges increases under thermal expansion differences
Solution Approach 1:
The recess structure acts as a beforehand cushioning measure by providing a stress-relief zone at the corner portions before thermal expansion stresses develop. The recess allows the bonding material to be positioned in a configuration that inherently reduces edge stress concentration, cushioning against the harmful effects of thermal cycling before damage can occur at the interface.
3Reliability
If a recess is added to the metal layer to reduce stress concentration, then reliability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The recess is implemented as a simple segmented feature at the corner portions of the metal layer, rather than a complex overall structural change. This localized segmentation approach modifies only the critical corner regions where stress concentration occurs, keeping the rest of the device structure simple and maintaining ease of manufacturing while improving reliability.
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 configuration extends the lifetime of semiconductor devices by reducing thermal history-related stress concentration, preventing damage and maintaining performance over long periods of operation.
Implementation Method 1
due to the thermal history of being exposed to high temperatures and low temperatures, the semiconductor device may begin to exhibit damage near the edges of the interface between the semiconductor element and the bonding material
Data Source
AI summary
A semiconductor device includes an insulated circuit board in which a metal layer is formed on one surface of an insulating board and a semiconductor element having a polygonal shape when viewed in a plan view that is bonded to the metal layer via a bonding material. The metal layer of the insulated circuit board has a recess that exposes the insulating board at a position corresponding to at least one corner of the semiconductor element.