Indium-Gallium Thermal Interface Material Melting Range
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Solution Overview
Problem
Conventional low melting point alloys (LMAs) for thermal interfaces in packaged semiconductors have a narrow melting temperature range and fixed eutectic temperatures, making them unsuitable for varying junction temperature requirements, and are prone to overheating or deformation, leading to poor thermal contact and potential fatigue fractures.
Innovation Solution
A metal thermal interface material (TIM) composed of 20-98 wt% indium, 0.03-4 wt% gallium, and at least one element of bismuth, tin, silver, or zinc, allowing for adjustable melting temperatures and a broad range, preventing overheating and accommodating thermal stress, with gallium content affecting the initial melting temperature and range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional low melting point alloys (LMAs) are used for thermal interfaces, then low interface thermal resistance is achieved, but the melting temperature range is narrow and cannot be adjusted for varying junction temperature requirements
Solution Approach 1:
The patent changes the chemical composition parameters of the LMA by adding gallium (0.03-4 wt%) to pure indium, which systematically adjusts the melting temperature and broadens the melting temperature range. This allows the thermal interface material to be tuned for different junction temperature requirements while maintaining low thermal resistance
Solution Approach 2:
The patent creates a composite LMA system by combining indium base metal with gallium additive elements. This composite approach enables both the low thermal resistance property of pure indium and the adjustable melting characteristics introduced by gallium, achieving multiple performance goals simultaneously
2Ease of manufacture
If conventional LMAs with fixed eutectic temperatures are used, then manufacturing simplicity is maintained, but adaptability to varying packaged semiconductor temperature requirements is reduced
Solution Approach 1:
The patent modifies the compositional parameters of conventional LMAs by introducing gallium as an additive element. This simple compositional change enables continuous adjustment of melting temperature and range, allowing the same base material system to be adapted for different semiconductor packaging temperature requirements without complicating the manufacturing process
3Strength
If pure indium or low-solute In-Ag alloy is used to accommodate thermal stress, then thermal stress accommodation is improved, but the temperature range for heat absorption is limited
Solution Approach 1:
The patent changes the compositional parameters by adding gallium to indium, which broadens the melting temperature range. This allows the material to maintain solid-state thermal stress accommodation at lower temperatures while extending the heat absorption capability to higher temperatures through the expanded melting range, achieving both objectives simultaneously
4Reliability
If conventional LMAs are used, then low interface thermal resistance is achieved, but overheating and deformation occur at high temperatures leading to poor thermal contact
Solution Approach 1:
The patent adjusts the melting temperature parameters of the LMA by adding gallium, which raises and broadens the temperature range before complete liquefaction. This allows the material to maintain its semi-solid state and effective thermal contact properties at higher operating temperatures, preventing overheating and deformation that would otherwise occur with conventional LMAs
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 TIM maintains a stable semi-solid state for efficient heat conduction, accommodating thermal stress and preventing overheating, thus enhancing the thermal interface performance and extending the temperature range beyond that of pure indium, while meeting RoHS regulations.
Implementation Method 1
The TIM maintains a stable semi-solid state for efficient heat conduction
Implementation Method 2
LMAs could outperform thermal greases with better interfacial heat-conduction performance because of the benefit of melting/solidification reaction caused by interface temperature fluctuation, which promote large absorption and dispersion of joule heat passing through the interface
Implementation Method 3
The first-stage thermal interface material between the IC die and the heat spreader lid connected thereof has to adequately accommodate the thermal stress or twist deformation caused by thermal expansion mismatch between the IC die and the heat dissipation device
Data Source
AI summary
A melting temperature adjustable metal thermal interface material (TIM) and a packaged semiconductor including thereof are provided. The metal TIM includes about 20-98 wt % of In, about 0.03-4 wt % of Ga, and at least one element of Bi, Sn, Ag and Zn. The metal TIM has an initial melting temperature between about 60-144° C.