Phase-Change Metallic Thermal Interface for Low-Pressure Cooling
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Solution Overview
Problem
Conventional thermal-interface materials face challenges in achieving low thermal-contact resistance across solid-solid interfaces, particularly at high power and limited upper-threshold temperatures, often requiring substantial compressive pressure and being less effective with non-uniform interfaces.
Innovation Solution
The use of metallic thermal-interface materials, such as eutectic and non-eutectic mixtures of Bismuth, Indium, and Tin, which undergo phase transition within a specific temperature range, providing low thermal-contact resistance (less than 0.05° C.-cm2/W) with pressures as low as 10-15 PSI, and are forgiving during manufacturing and assembly, even with non-uniform interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal-interface materials are used, then thermal-contact resistance is reduced, but substantial compressive pressure is required
Solution Approach 1:
The patent changes the physical state parameter of the thermal-interface material by using phase-change materials that transition from solid to liquid at operating temperatures. This parameter change allows the material to flow and fill interface gaps without requiring substantial compressive pressure, while still achieving low thermal-contact resistance through the liquid phase's ability to conform to surface irregularities.
Solution Approach 2:
The patent directly applies phase transitions by selecting materials with melting points within the operating temperature range (e.g., gallium indium tin alloy with 10-30°C melting point). The material transitions from solid during assembly to liquid during operation, enabling gap filling and low thermal resistance without high pressure. The phase transition temperature is specifically chosen to occur after assembly but before maximum operating temperature.
2Reliability
If conventional thermal-interface materials are used, then thermal-contact resistance is reduced, but manufacturing precision is compromised
Solution Approach 1:
The phase transition from solid to liquid during operation allows the thermal-interface material to naturally flow and self-level across the interface, compensating for manufacturing variations in surface flatness and component alignment. This eliminates the need for precision machining or careful assembly that would otherwise be required to achieve uniform thermal contact.
Solution Approach 2:
The patent introduces dynamic behavior by using a material that changes its physical state from rigid (solid) to fluid (liquid) at operating temperatures. This dynamic property allows the material to adapt to interface geometries that would be difficult or impossible to achieve with static, solid-only materials, thereby reducing sensitivity to manufacturing precision requirements.
3Power
If high power operation is implemented, then heat transfer rate is increased, but thermal resistance becomes more significant
Solution Approach 1:
The phase-change material absorbs latent heat during melting, providing an additional heat transfer mechanism beyond conduction. This phase transition heat absorption occurs at constant temperature, effectively increasing the heat transfer rate without proportionally increasing thermal resistance. The material transitions from solid to liquid, absorbing large amounts of energy in the 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
These materials significantly reduce thermal resistance across solid-solid interfaces, improving heat transfer efficiency while being more forgiving during manufacturing and assembly, and maintaining performance across a range of temperatures and interface geometries.
Implementation Method 1
metallic thermal-interface materials, some of which partially or wholly undergo phase transition within an expected range of operating temperatures
Implementation Method 2
eutectic and non-eutectic mixtures of Bismuth, Indium, and Tin, which undergo phase transition within a specific temperature range
Implementation Method 3
providing low thermal-contact resistance (less than 0.05° C.-cm2/W) with pressures as low as 10-15 PSI
Data Source
AI summary
A heat-transfer component defines a thermal-interface surface and has a metallic thermal-interface material bonded to the thermal-interface surface. The metallic thermal-interface material has a solid-to-liquid phase-change temperature between about 60° C. and about 90° C. With a thermal-interface material bonded to the thermal-interface surface, the thermal-contact resistance between the thermal-interface material and the heat-transfer component can be reduced or substantially eliminated compared to conventional thermal-interface materials, including conventional metallic thermal-interface materials. Also disclosed are electrical devices having a heat generating component cooled by such a heat-transfer component.