Power Module Substrate with Doped Copper Circuit Layer
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Solution Overview
Problem
Power module substrates face challenges in effectively radiating heat due to the lower thermal conductivity of aluminum compared to copper, and copper substrates are prone to cracking from thermal expansion differences, leading to substrate damage during cooling and heating cycles.
Innovation Solution
A power module substrate with a copper circuit layer doped with alkaline-earth, transition metal, or rare-earth elements, and boron, bonded to an insulating substrate, and an aluminum metal layer with additive elements like Si, Cu, Ag, Zn, Mg, Ge, Ca, Ga, and Li, to enhance thermal conductivity and reduce strain hardening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If an aluminum plate is used as the circuit layer, then the substrate weight is reduced and cost is lowered, but thermal conductivity decreases and heat radiation becomes insufficient
Solution Approach 1:
The circuit layer is constructed as a composite structure with a copper base plate providing thermal conduction pathways, overlaid with an aluminum alloy layer that reduces weight and cost. This composite configuration enables the substrate to achieve both low weight and high thermal conductivity by combining the advantageous properties of different materials in a functional architecture where copper handles heat transfer and aluminum provides structural lightness.
2Temperature
If a copper plate is used as the circuit layer, then thermal conductivity improves and heat radiation increases, but shear stress from thermal expansion differences causes strain hardening and cracking
Solution Approach 1:
The aluminum alloy layer's composition parameters are optimized to match its coefficient of thermal expansion with that of the copper base plate. By adjusting the alloying elements and their concentrations, the thermal expansion mismatch is minimized, reducing shear stress during thermal cycling and preventing strain hardening and cracking while maintaining the high thermal conductivity of copper.
Solution Approach 2:
The circuit layer uses a copper-aluminum composite structure where the copper base provides thermal conductivity and the aluminum alloy overlay provides thermal expansion compatibility with the insulating substrate. This layered composite design allows the system to simultaneously achieve high heat radiation capability and resistance to thermal cycling-induced cracking by distributing functional requirements across different material layers.
3Temperature
If a copper plate is used without thermal expansion matching, then heat radiation is effective, but thermal strain causes cracking in the insulating substrate
Solution Approach 1:
The thermal expansion parameters of the aluminum alloy layer are specifically adjusted to serve as a buffer between the copper base plate and the insulating substrate. The alloy composition is designed so that its thermal expansion coefficient falls between those of copper and the ceramic substrate, creating a gradient that reduces thermal strain concentration and prevents cracking while allowing effective heat radiation through the copper layer.
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 radiates heat and suppresses cracking in the insulating substrate during thermal cycles, ensuring reliable bonding and prolonged substrate integrity.
Implementation Method 1
thermal conductivity of the aluminum is lower than that of copper. Accordingly, in the case of using an aluminum plate as the circuit layer, heat transferred from a heat generating body such as an electrical component or the like which is mounted on the circuit layer cannot be spread and radiated
Implementation Method 2
a shear stress caused by a difference in coefficient of thermal expansion between the insulating substrate and the copper plate due to the above-described cooling and heating cycle
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A power module substrate (10) includes an insulating substrate (11), and a circuit layer (12) that is formed on one surface of the insulating substrate (11). The circuit layer (12) is formed by bonding a first copper plate (22) onto one surface of the insulating substrate (11). Prior to bonding, the first copper plate (22) has a composition containing at least either a total of 1 to 100 mol ppm of one or more kinds among an alkaline-earth element, a transition metal element, and a rare-earth element, or 100 to 1000 mol ppm of boron, the remainder being copper and unavoidable impurities.