Cold-Sprayed Metal-Diamond Thermal Structure for Semiconductor Heat Dissipation
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Solution Overview
Problem
Current heat spreader materials face challenges with high thermal conductivity (TC) and low coefficient of thermal expansion (CTE) mismatches, leading to thermal stress and reliability issues in semiconductor electronics, where existing materials like copper and CVD diamond are inadequate for modern heat flux levels and suffer from CTE mismatch problems.
Innovation Solution
A thermal structure comprising a semiconductor substrate with a ductile base layer and a top layer formed by cold spraying a metal-diamond matrix, where the metal matrix is formed by deforming metal particles upon impact, embedding diamond particles within, which reduces CTE mismatch and eliminates the need for thermal interface materials (TIMs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high thermal conductivity materials like copper are used, then heat dissipation is improved, but CTE mismatch with semiconductor substrates increases causing thermal stress and reliability issues
Solution Approach 1:
The patent applies composite materials by combining metal particles (providing ductility and thermal conductivity) with diamond particles (providing low CTE and high thermal conductivity) in a matrix structure. This composite approach allows the heat spreader to simultaneously achieve high thermal conductivity, low CTE, and ductility, resolving the contradiction between thermal performance and CTE mismatch with semiconductor substrates.
Solution Approach 2:
The patent changes the physical and chemical parameters of the material by controlling the particle size distribution, metal-to-diamond ratio, and density of the composite structure. By optimizing these parameters, the heat spreader achieves a CTE matched to semiconductor substrates while maintaining high thermal conductivity and ductility, eliminating thermal stress issues.
2Object-affected harmful factors
If CTE-matched materials like ceramics or metal-matrix composites are used, then CTE mismatch is reduced, but thermal conductivity decreases to levels insufficient for modern heat flux
Solution Approach 1:
The patent uses a metal-diamond composite where diamond particles (low CTE, high TC) are distributed in a metal matrix (high TC, ductile). This composite structure achieves both CTE matching with semiconductors and high thermal conductivity sufficient for modern heat flux levels, overcoming the limitations of conventional ceramic or composite materials.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where diamond particles (providing low CTE) and metal particles (providing high TC and ductility) are distributed throughout the matrix. Different regions of the composite contribute different properties, achieving overall CTE matching while maintaining high thermal conductivity pathways through the metal and diamond phases.
3Object-affected harmful factors
If thick thermal interface material layers are used to accommodate CTE mismatch, then CTE compatibility is improved, but thermal resistance increases significantly
Solution Approach 1:
The patent eliminates the need for thick thermal interface material layers by directly bonding the ductile metal-diamond composite heat spreader to the semiconductor substrate. The composite's inherent ductility and CTE matching allow for direct contact, removing the thermal resistance introduced by TIM layers while maintaining CTE compatibility.
Solution Approach 2:
The patent changes the interface properties by creating a direct bond between the ductile composite heat spreader and the semiconductor substrate. The controlled ductility and CTE of the composite enable intimate thermal contact without requiring additional interface materials, thereby minimizing thermal resistance while accommodating thermal expansion differences.
4Reliability
If ductile materials are used to enable direct bonding without TIM, then thermal interface quality is improved, but CTE mismatch with semiconductor substrates worsens
Solution Approach 1:
The patent employs a metal-diamond composite where the metal phase provides ductility for direct bonding while the diamond phase contributes low CTE. This composite structure enables direct bonding to semiconductor substrates with high thermal interface quality while simultaneously matching the CTE of the substrate, eliminating the trade-off between ductility and CTE compatibility.
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 solution provides a highly thermally conductive and low CTE structure that effectively dissipates heat without the use of TIMs, enhancing the reliability and efficiency of heat transfer by forming a continuous interface and reducing thermal resistance, suitable for semiconductor applications.
Implementation Method 1
a top layer comprising a matrix of metal and diamond formed above the base layer by cold spraying a powder selected from: a powder mixture of metal and diamond particles, and a powder of metal-clad diamond particles, wherein the top layer is formed of a matrix of metal formed by the deformation of the metal components of the powder on impact with the underlying surface and a dispersed phase comprising the diamond particles embedded within the metal matrix
Implementation Method 2
CS is an additive manufacturing technology capable of producing coatings of metals, composites, ceramics and polymers onto a variety of substrate materials. This is accomplished by accelerating small particles (1-60 μm range) up to supersonic speed in a nozzle using a carrier gas. Upon impact against a substrate, the particles plastically deform and bond to it.
Implementation Method 3
The solution provides a highly thermally conductive and low CTE structure that effectively dissipates heat without the use of TIMs, enhancing the reliability and efficiency of heat transfer
Data Source
AI summary
A thermal structure for dissipating heat from a semiconductor substrate has a semiconductor substrate having an external surface which may be roughened. An optional base layer comprising aluminium is formed on top of the external surface by a cold spraying process, and a top layer comprising a matrix of copper and diamond is formed above the substrate, and above the base layer if present, by cold spraying a powder mixture of copper and diamond particles. The top layer is thereby created as a matrix of copper formed by the deformation of the copper particles on impact with the underlying surface and a dispersed phase comprising the diamond particles embedded within the copper matrix. The resulting structure has high thermal conductivity and a coefficient of thermal expansion that is well matched to the substrate, and eliminates the need for a thermal interface material or paste.