Compliant Heat Exchanger for Non-Uniform Multi-Chip Assemblies
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Solution Overview
Problem
Multi-chip modules with non-uniform chip heights pose challenges in achieving adequate thermal contact and efficient heat dissipation, as existing air-cooled heat sinks are too stiff to adapt to non-planar surfaces, leading to increased thermal resistance and limited thermal envelopes.
Innovation Solution
A compliant air heat exchanger with flexible elements and vapor chambers provides mechanical compliance and enhanced thermal performance, allowing for uniform bondline thickness across non-uniform chip assemblies without additional thermal resistance, using a base plate, flexible elements, and inflexible elements to create cavities that can be filled with evaporative fluids for improved heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If air-cooled heat sinks are used for multi-chip modules with non-uniform chip heights, then the structure is simple and easy to manufacture, but the heat sink is too stiff to adapt to non-planar surfaces, resulting in increased thermal resistance
Solution Approach 1:
The patent employs a flexible membrane as the heat transfer interface between the chips and the heat sink. This membrane can deform and conform to the non-planar surfaces of multi-chip assemblies with varying heights, ensuring adequate thermal contact across all chips while maintaining a simple overall heat sink structure. The flexibility of the membrane resolves the contradiction by adapting to surface irregularities without requiring complex rigid heat sink geometries.
Solution Approach 2:
The patent changes the physical state of the heat transfer interface from rigid to flexible by using a membrane that can undergo deformation. This parameter change allows the heat sink to adapt its contact pressure and surface geometry to match the non-uniform chip heights, improving thermal contact reliability while keeping the manufacturing process simple.
2Reliability
If lids are used to flatten warped assemblies and adapt to multi-chip topologies, then thermal contact is improved, but additional thermal resistance is introduced and the structure becomes more complex
Solution Approach 1:
Instead of using a rigid lid to flatten and adapt to multi-chip topologies, the patent uses a flexible membrane that naturally conforms to the existing non-planar chip surfaces. This eliminates the need for additional flattening mechanisms or complex lid structures, reducing overall device complexity while maintaining reliable thermal contact across all chips.
Solution Approach 2:
Rather than attempting to flatten the chips to match a rigid heat sink surface, the patent inverts the approach by making the heat transfer interface itself flexible so that it adapts to the chip surfaces. This inversion eliminates the need for additional adaptive components and reduces structural complexity.
3Temperature
If forced liquid coolant flow is used through multi-chip modules, then cooling performance is improved, but the system becomes more complex and expensive requiring forced flow mechanisms
Solution Approach 1:
The patent replaces the mechanical forced liquid coolant flow system with a passive air-cooled vapor chamber system. The vapor chamber uses phase change mechanics (evaporation and condensation) to achieve superior cooling performance without requiring pumps, valves, or complex fluid distribution networks, thereby reducing device complexity while improving temperature control.
Solution Approach 2:
The patent utilizes phase transitions of the working fluid within the vapor chamber to achieve efficient heat transfer. The fluid evaporates at the heated base, absorbs latent heat, condenses on the cooler outer surfaces, and releases heat, creating a passive but highly effective cooling mechanism that outperforms forced liquid flow without the associated complexity.
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 compliant air heat exchanger effectively adapts to non-uniform chip surfaces, reducing thermal resistance and improving the thermal envelope by allowing for a thin, uniform bondline thickness, thus enhancing cooling efficiency without the need for lids or additional assembly steps.
Implementation Method 1
The compliant air heat exchanger comprises, in embodiments, at least one flexible element such as a membrane or a thinned area
Implementation Method 2
The internal geometry allows for at least one cavity that can act as vapor chambers, at logical positions, in the base plate
Implementation Method 3
cavities that can be filled with evaporative fluids for improved heat transfer
Implementation Method 4
compliant air heat exchanger
Implementation Method 5
functionality that provides good thermal performance
Data Source
AI summary
This invention relates to cooling devices for multi-chip semiconductor devices, system-on-a-package devices, and other packaged devices. Because of the non-uniform height across the surface in such large-chip and multi-chip assemblies, providing heat exchange can be troublesome. Many air cooled heat sinks are too stiff to adapt to such non-uniform or warped shapes of chips or to shape-changing chip surfaces during operation. In the present disclosure, application of a mechanical load perpendicular to the chip plane causes certain features to flex and adapt to the non-uniform height of the chip plane, providing improved heat exchange.