Composite Solder TIM with Aluminum Particles
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Solution Overview
Problem
The high cost and limited availability of indium, combined with the challenges of implementing alternative thermal interface materials with different properties, hinder the development and implementation of efficient thermal management solutions for modern integrated circuit devices, particularly in applications requiring thin bondlines.
Innovation Solution
A composite solder thermal interface material is formed through thixocasting, incorporating aluminum particles dispersed within indium, which provides improved thermal conductivity and cost-effectiveness while minimizing oxidation and thermal strain, utilizing a mixture of molten indium and aluminum with controlled agitation and oxygen exclusion to create a metallic slurry with spherical aluminum particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure indium is used as thermal interface material, then thermal conductivity and malleability are improved, but material cost increases dramatically
Solution Approach 1:
The patent creates a composite material consisting of indium matrix with dispersed aluminum particles. This composite maintains the beneficial properties of pure indium (malleability, thermal conductivity, low melting point) while reducing cost by replacing a portion of expensive indium with cheaper aluminum. The aluminum particles are distributed throughout the indium matrix, creating a material that leverages the high thermal conductivity of aluminum while preserving indium's unique properties.
Solution Approach 2:
The patent modifies the compositional parameters of the thermal interface material by controlling the volume percentage of aluminum particles (5-50% of total material volume). By adjusting this parameter, the patent optimizes the balance between cost reduction and thermal performance, allowing customization based on specific application requirements while maintaining the essential characteristics needed for thin bondline applications.
2Temperature
If alternative materials with higher melting point are used, then thermal stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes the phase transition properties of indium (melting point 156°C) to enable simple manufacturing processes. The indium-based composite can be applied in固态 form and then reflowed by heating above indium's melting point but below aluminum's melting point (660°C), creating a self-leveling, self-healing joint. This phase transition approach allows for simplified manufacturing compared to materials requiring higher processing temperatures.
3Ease of manufacture
If aluminum particles are added to indium, then cost is reduced and thermal conductivity is improved, but oxidation resistance may worsen
Solution Approach 1:
The patent employs inert or reducing atmosphere during the manufacturing and processing of the indium-aluminum composite to prevent oxidation of aluminum particles. By controlling the atmospheric environment (using nitrogen, argon, or hydrogen atmospheres), the patent protects the aluminum particles from oxidizing while maintaining the benefits of the composite material structure.
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 thixocast composite material offers enhanced thermal performance and reduced material costs, maintaining the benefits of indium while leveraging aluminum's higher conductivity, with minimal oxidation and reduced thermal strain, making it an effective replacement for pure indium in IC packages.
Implementation Method 1
A composite solder material is formed through thixocasting, including an indium host material and aluminum particles dispersed within the indium
Implementation Method 2
the mixture is agitated during cooling to break apart dendritic aluminum structures before they can substantially form
Implementation Method 3
a composite solder material is formed through thixocasting... offers enhanced thermal performance
Implementation Method 4
indium, which is quite malleable, has a relatively low melting temperature... Applications calling for a very thin TIM in a thin bondline
Data Source
AI summary
A method includes providing a mixture of molten indium and molten aluminum, and agitating the mixture while reducing its temperature until the aluminum changes from liquid phase to solid phase, forming particles distributed within the molten indium. Agitation of the mixture sufficiently to maintain the aluminum substantially suspended in the molten aluminum continues while further reducing the temperature of the mixture until the indium changes from a liquid phase to a solid phase. A metallic composition is formed, including indium and particles of aluminum suspended within the indium, the aluminum particles being substantially free from oxidation.The metallic (solder) composition can be used to form an assembly, including an integrated circuit (IC) device, at least a first thermal component disposed adjacent to the IC device, and a solder TIM interposed between and thermally coupled with each of the IC device and the first thermal component.