Laminate With Low-Hydrogen Copper Film for Thermal Stress Management
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Solution Overview
Problem
In power modules, thick metal films are needed for efficient heat dissipation, but they risk peeling or cracking due to thermal expansion differences between the metal film and insulating substrate, especially under thermal load.
Innovation Solution
A laminate with a copper powder metal film having low hydrogen (0.002% by mass or less) and specific oxygen (0.03% to 0.15% by mass) and phosphorus (0.002% to 0.028% by mass) content, deposited using a cold spraying method with an intermediate metal or alloy layer, to prevent thermal expansion issues and ensure strong adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metal film is made thicker to reduce thermal resistance and improve heat transfer efficiency, then heat dissipation performance is improved, but the risk of peeling or cracking due to thermal expansion difference increases
Solution Approach 1:
An intermediate layer is introduced between the metal film and the insulating substrate. This intermediate layer serves as a buffer that accommodates the coefficient of thermal expansion difference between the metal film and substrate, preventing peeling and cracking while allowing the metal film to maintain sufficient thickness for effective heat dissipation.
Solution Approach 2:
The laminate structure combines multiple materials (insulating substrate, intermediate layer, and metal film) with different properties. The intermediate layer is specifically selected or designed to have mechanical and thermal properties that bridge the metal film and substrate, creating a composite structure that resolves the thermal expansion mismatch problem.
2Use of energy by moving object
If the metal film is made thicker to reduce thermal resistance, then heat transfer efficiency is improved, but the risk of cracking the insulating substrate increases
Solution Approach 1:
The intermediate layer acts as a protective intermediary that absorbs and distributes thermal stress, preventing it from concentrating on the insulating substrate and causing cracks, thereby enabling the use of thicker metal films for improved heat transfer.
Solution Approach 2:
The intermediate layer is placed in advance between the metal film and substrate to provide cushioning against thermal stress before it can cause damage. This preventive measure allows the system to withstand thermal loads without substrate cracking.
3Temperature
If conventional cold spraying method is used to form metal film, then processing temperature is kept low and oxidation is suppressed, but hydrogen content in the metal film becomes high causing voids and reducing adhesion
Solution Approach 1:
The copper powder undergoes controlled heat treatment in a vacuum or inert atmosphere, changing the thermal parameters to remove hydrogen without causing oxidation. This parameter change (heat treatment conditions) resolves the contradiction by eliminating hydrogen-induced defects while maintaining the low-temperature advantage of cold spraying.
Solution Approach 2:
Heat treatment is performed in a vacuum or inert gas atmosphere to prevent oxidation of the copper powder while allowing hydrogen removal. This creates an inert environment that enables the necessary thermal processing without the harmful side effect of oxidation.
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 laminate achieves high heat dissipation without substrate cracking or voids in the metal film, maintaining adhesion strength and thermal conductivity.
Implementation Method 1
a method of forming a film on a surface of a substrate by injecting a powder of a material from a divergent (laval) nozzle together with an inert gas at a melting point or lower or a softening point or lower, and causing the powder to collide with the substrate in a solid phase state
Implementation Method 2
plastic deformation occurs between the powder and the substrate to obtain an anchor effect
Implementation Method 3
an interface between the intermediate layer and the metal film is plastically deformed
Implementation Method 4
a power module can perform cooling by moving heat generated from the chip to the cooling unit via the metal film and radiating the heat to an outside
Data Source
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AI summary
To provide a laminate having a high heat dissipation effect, having no problem such as cracking of an insulating substrate even when a thermal load is applied, and having no void or the like in a metal film, and a method of manufacturing the laminate. A laminate according to the present invention includes an insulating substrate 10, an intermediate layer 50 formed on a surface of the substrate 10 and containing a metal or an alloy as a main component, and a circuit layer 20 that is a metal film formed of a copper powder having a hydrogen content of 0.002% by mass or less and laminated on the intermediate layer 50. In the laminate, an interface between the intermediate layer 50 and the circuit layer 20 is plastically deformed.