Power Module Substrate with Asymmetric Copper Layer for Warp Prevention
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Solution Overview
Problem
Existing power-module substrates face challenges in maintaining accuracy of position and preventing warp deformation due to temperature fluctuations, which affects the integration and radiation performance of semiconductor devices.
Innovation Solution
A power-module substrate unit with a ceramic substrate layer, a circuit layer formed by small circuit layers joined via solid diffusion bonding, and a radiation plate made of copper or copper alloy, where the thickness, bonding area, and yield stress ratios between the copper layer and radiation plate are optimized to create a symmetrical structure, reducing internal stresses and preventing warp deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple circuit layers are arrayed on an insulated substrate to downsize the module, then integration is improved, but warp occurs due to temperature fluctuation
Solution Approach 1:
The patent applies asymmetry by configuring the copper layer and radiation plate with different thicknesses, bonding areas, and yield stresses. The ratio (t1×A1×σ1)/(t2×A2×σ2) is controlled within 0.8-1.2, creating an asymmetric structure that compensates for thermal expansion differences and prevents warp while maintaining high integration of multiple circuit layers.
2Reliability
If lead frames are used to join insulated substrates, then radiation performance is maintained, but positioning accuracy deteriorates
Solution Approach 1:
The patent changes the physical parameters of the copper layer (thickness t1, bonding area A1, yield stress σ1) relative to the radiation plate (thickness t2, bonding area A2, yield stress σ2). By controlling the ratio (t1×A1×σ1)/(t2×A2×σ2) within 0.8-1.2, the structure achieves both good radiation performance and high positioning accuracy for multiple circuit layers.
3Ease of operation
If direct holding of insulated substrates is implemented, then positioning is simplified, but molding die restriction increases
Solution Approach 1:
The patent introduces a copper layer as an intermediary between the insulated substrate and the radiation plate. This intermediary layer facilitates direct holding of substrates while accommodating molding die constraints, as the copper layer can be precisely controlled in thickness and bonding area to achieve both ease of positioning and compatibility with 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
This configuration enhances the reliability and integration of semiconductor elements by maintaining accurate positioning and improving radiation performance while minimizing deformation from temperature fluctuations.
Implementation Method 1
a first copper layer joined on the first aluminum layer by solid diffusion bonding
Implementation Method 2
the radiation plate is made from copper or copper alloy and joined on the metal layer by solid diffusion bonding
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
In a power-module substrate unit 51, a circuit layer 12 is structured by a plurality of small circuit layers 12S; a ceramic substrate layer 11 is structured by at least one plate; the small circuit layers 12S are formed to have a layered structure having a first aluminum layer 15 bonded on one surface of the ceramic substrate layer 11 and a first copper layer 16 bonded on the first aluminum layer 15 by solid diffusion; a radiation plate 30 is made of copper or copper alloy; the metal layer 13 and the radiation plate 30 are bonded by solid diffusion, and a ratio (t1 × A1 × σ1) / (t2 × A2 × σ2) is not smaller than 0.80 and not larger than 1.20 where a thickness is t1 (mm), a bonding area is A1 (mm2), and an yield stress is σ1 (N/mm2) of the first copper layer 16; a thickness at a bonding position to the metal layer is t2 (mm), a bonding area is A2 (mm2), and an yield stress of the radiation plate 30 is σ2 (N/mm2).