Thermally Conductive Composite Sheet Bonding
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Solution Overview
Problem
The compatibility between aluminum and graphite is poor due to poor wettability and a chemical reaction that occurs at high temperatures, leading to a brittle carbide layer formation, which weakens the heat-conducting properties of graphite and composite materials, and existing manufacturing methods for thermally conductive composites are complex and costly.
Innovation Solution
A thermally conductive composite sheet is created by sandwiching a graphite sheet within an aluminum alloy frame between two aluminum alloy layers, with diffusion-bonding under controlled temperature and pressure to form a unity, using mechanical and chemical treatments to prepare active surfaces for bonding, and optionally incorporating transition layers for enhanced bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum and graphite are bonded together, then heat-conducting properties are improved, but a brittle carbide layer forms due to chemical reaction at high temperatures
Solution Approach 1:
A transition layer comprising a transition metal or its alloy is introduced between the aluminum alloy and graphite. This transition layer acts as an intermediary that prevents direct chemical reaction between aluminum and graphite, avoiding carbide formation while maintaining thermal conductivity. The transition layer is diffusion-bonded to both aluminum alloy and graphite, creating a stable intermediate structure.
Solution Approach 2:
The invention creates a multi-layer composite structure consisting of aluminum alloy layers, transition layers, and graphite sheets bonded together through diffusion bonding. This composite structure combines the high thermal conductivity of aluminum and graphite while using the transition layer to prevent harmful chemical reactions, achieving both thermal performance and structural reliability.
2Manufacturing precision
If traditional hot pressing is used to manufacture thermally conductive composites, then material density is improved, but production complexity and cycle time increase significantly
Solution Approach 1:
The aluminum alloy sheets, transition layers, and graphite sheets are prepared and pre-assembled into a laminated structure before diffusion bonding. This preliminary preparation allows for precise control of layer thicknesses and arrangements, ensuring high material density in the final product while simplifying the actual bonding process to a single diffusion bonding step rather than complex multi-stage hot pressing.
Solution Approach 2:
The invention replaces traditional mechanical hot pressing with diffusion bonding under controlled atmosphere. Instead of applying high mechanical pressure and temperature for extended periods to achieve density, the process uses controlled diffusion bonding at lower temperatures with precise atmospheric control, significantly reducing production cycle time while maintaining or improving material quality.
3Strength
If diffusion bonding is used to bond aluminum alloy and graphite, then bonding strength is improved, but production cost increases due to controlled atmosphere requirements
Solution Approach 1:
The diffusion bonding process is conducted in a controlled inert atmosphere (vacuum or protective gas) that prevents oxidation of the aluminum alloy and transition layer during bonding. This controlled atmosphere enables strong, clean diffusion bonds without requiring expensive additional protective coatings or post-processing, balancing bonding strength with manufacturing cost by using a relatively simple atmospheric control system.
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 method produces a composite with desirable heat-conducting properties and light weight, suitable for thermal control and electronic packaging, while avoiding issues like bulging and deformation, and enables mass production with low costs and high efficiency.
Implementation Method 1
the first aluminum alloy layer and the second aluminum alloy layer are respectively diffusion-bonded to the graphite sheet and the aluminum alloy frame
Implementation Method 2
using mechanical and chemical treatments to prepare active surfaces for bonding
Implementation Method 3
using mechanical and chemical treatments to prepare active surfaces for bonding
Data Source
Figure 1~2
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AI summary
The present invention discloses a thermally conductive composite sheet, including a first aluminum alloy layer, at least one graphite sheet, an aluminum alloy frame, and a second aluminum alloy layer, where the aluminum alloy frame is provided with at least one opening; the graphite sheet is positioned inside the opening of the aluminum alloy frame; the aluminum alloy frame and the graphite sheet are sandwiched between the first aluminum alloy layer and the second aluminum alloy layer; the first aluminum alloy layer is diffusion-bonded to the graphite sheet and the aluminum alloy frame; the second aluminum alloy layer is diffusion-bonded to the graphite sheet and the aluminum alloy frame; and the graphite sheet is cladded by the first aluminum alloy layer, the second aluminum alloy layer, and the aluminum alloy frame, to form a unity. The present invention further provides a method for making the thermally conductive composite sheet. According to the thermally conductive composite sheet and the method for making same that are provided in the present invention, an aluminum alloy and graphite that are highly thermally conductive can be bonded, and production costs are relatively low.