Radial Flow Chip Stack Cooling for Two-Phase Stability
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Solution Overview
Problem
Efficient cooling of 3D chip stacks is challenging due to instability in two-phase flow through microchannels, leading to high vapor velocity and pressure drops that disrupt the cooling process, particularly in high-power chip stacks with multiple chips.
Innovation Solution
A chip package structure with integrated radial liquid-vapor flow cooling, featuring a central inlet manifold and peripheral outlet manifold, guided by radial flow channels and inlet nozzles to stabilize the flow and reduce pressure drops, using guiding walls and varying nozzle sizes to direct coolant effectively across the chip stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If two-phase cooling is used in microchannels, then cooling efficiency is improved, but flow stability deteriorates due to high vapor velocity and pressure drops
Solution Approach 1:
The patent transitions from conventional linear microchannel flow to radial flow geometry, where coolant enters centrally and flows outward in multiple dimensions across the chip stack. This radial configuration reduces flow path length and vapor velocity while maintaining effective heat removal, resolving the contradiction between cooling efficiency and flow stability
Solution Approach 2:
The chip stack is divided into multiple flow cavities separated by guiding walls, with each cavity receiving coolant through dedicated inlet nozzles. This segmentation stabilizes two-phase flow by confining vapor-liquid interaction to discrete regions, preventing flow instability while maintaining high cooling efficiency across the entire stack
2Device complexity
If conventional microchannel structures are used, then device complexity is reduced, but cooling performance deteriorates due to unstable two-phase flow
Solution Approach 1:
The radial flow manifold structure serves multiple functions simultaneously: it distributes coolant to multiple flow cavities, provides structural support through guiding walls, and stabilizes two-phase flow through its geometry. This multi-functionality achieves superior cooling performance without proportionally increasing device complexity
Solution Approach 2:
The patent introduces radial flow geometry that extends cooling in the lateral dimension from the central inlet, rather than relying solely on linear microchannels. This dimensional change provides inherent flow stability and improved cooling performance with relatively simple structural implementation
3Productivity
If high vapor velocity occurs in two-phase flow, then evaporation rate increases, but pressure drops increase and dry-out occurs
Solution Approach 1:
The radial flow configuration distributes vapor generation across multiple circumferential directions from the central inlet, reducing vapor velocity in any single direction. This dimensional distribution maintains high overall evaporation rate while reducing localized pressure drops and preventing dry-out conditions
Solution Approach 2:
By dividing the chip stack into multiple flow cavities with guiding walls, the patent segments vapor-liquid flow paths. This segmentation allows each cavity to maintain adequate liquid supply and evaporation rate while reducing vapor velocity and pressure drops through shorter, confined flow paths
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 radial flow configuration enhances cooling efficiency by maintaining a stable evaporating film, reducing pressure drops, and preventing dry-out, allowing for effective heat dissipation in high-power chip stacks with multiple chips.
Implementation Method 1
the heated liquid evaporates to create an annular flow wherein a thin liquid film (evaporation layer) is present on the surfaces being cooled
Implementation Method 2
the latent heat of the liquid coolant is typically much larger than the specific heat of the fluid times the typical temperature increase of the liquid coolant
Implementation Method 3
two-phase cooling with radial liquid-vapor flow
Implementation Method 4
a thin liquid film (evaporation layer) is present on the surfaces being cooled
Data Source
AI summary
A package structure to implement two-phase cooling includes a chip stack disposed on a substrate, and a package lid that encloses the chip stack. The chip stack includes a plurality of conjoined chips, a central inlet manifold formed through a central region of the chip stack, and a peripheral outlet manifold. The central input manifold includes inlet nozzles to feed liquid coolant into flow cavities formed between adjacent conjoined chips. The peripheral outlet manifold outputs heated liquid and vapor from the flow cavities. The package lid includes a central coolant supply inlet aligned to the central inlet manifold, and a peripheral liquid-vapor outlet to output heated liquid and vapor that exits from the peripheral outlet manifold. Guiding walls may be included in the flow cavities to guide a flow of liquid and vapor, and the guiding walls can be arranged to form radial flow channels that are feed by different inlet nozzles of the central inlet manifold.