Power Module Substrate Bonding via Solid Phase Diffusion
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Solution Overview
Problem
Conventional methods for bonding power module substrates with heat sinks using grease or solder result in high thermal resistance, leading to increased temperatures and reduced functionality of electronic components, especially when aluminum or aluminum alloys are used with copper or copper alloys.
Innovation Solution
The use of solid phase diffusion bonding between a metal layer and a heat sink, forming an intermetallic compound layer with dispersed oxides, reduces thermal resistance and enhances bonding reliability, while maintaining temperatures below the eutectic temperature to prevent liquid phase formation and excessive compound generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If grease or solder is used to bond the metal layer and heat sink, then the bonding process is simple, but the thermal resistance increases and heat dissipation performance deteriorates
Solution Approach 1:
The invention removes the intermediate bonding materials (grease or solder) from the bonding interface between the metal layer and heat sink. By directly bonding the aluminum metal layer to the copper heat sink through diffusion bonding, the thermal resistance introduced by intermediate materials is eliminated, thereby improving heat dissipation performance while maintaining manufacturing feasibility through a controlled thermal process
Solution Approach 2:
The invention introduces an intermetallic compound layer as a controlled intermediate phase between the aluminum metal layer and copper heat sink. This intermetallic layer, formed through diffusion bonding at elevated temperatures, serves as a mediator that enables strong metallurgical bonding while maintaining low thermal resistance, thus resolving the contradiction between bonding strength and heat dissipation
2Strength
If the bonding temperature exceeds the eutectic temperature, then bonding strength improves, but liquid phase formation causes excessive compound generation and distortion
Solution Approach 1:
The invention precisely controls the bonding temperature parameter to be above the diffusion activation temperature but below the eutectic temperature of the aluminum-copper system. This parameter optimization enables sufficient atomic diffusion for strong bonding while preventing liquid phase formation, thus achieving both high bonding strength and compositional stability without excessive intermetallic compound generation
Solution Approach 2:
The invention applies a protective oxide layer on the aluminum metal layer before bonding. This oxide layer acts as a cushion that prevents excessive intermetallic compound growth and distortion during the diffusion bonding process, while still allowing sufficient thermal contact and bonding. The oxide layer is formed beforehand and protects the interface during the thermal process
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 approach significantly reduces thermal resistance and improves heat dissipation, maintaining component stability and reliability under thermal cycling, with the intermetallic compound layer providing stable properties and preventing excessive distortion.
Implementation Method 1
the metal layer and the heat sink are bonded together by solid phase diffusion bonding
Implementation Method 2
a power module substrate in which a circuit layer is arranged on one surface of an insulation layer and a metal layer is arranged on the other surface of the insulation layer, and a heat sink bonded on the metal layer
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A heat-sink-attached-power module substrate (1) has a configuration such that either one of a metal layer (13) and a heat sink (31) is composed of aluminum or an aluminum alloy, and the other one of them is composed of copper or a copper alloy, the metal layer (13) and the heat sink (31) are bonded together by solid phase diffusion bonding, an intermetallic compound layer formed of copper and aluminum is formed in a bonding interface between the metal layer (13) and the heat sink (31), and an oxide is dispersed in an interface between the intermetallic compound layer and either one of the metal layer (13) composed of copper or a copper alloy and heat sink (31) composed of copper or a copper alloy in a layered form along the interface.