Counter-flow expanding channels for two-phase chip stack cooling
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Solution Overview
Problem
Efficient cooling of 3D chip stacks is challenging due to limitations in existing cooling techniques, particularly for high-power stacks, as they often require complex integration and may not adequately address thermal management, leading to reduced stack height and power capacity.
Innovation Solution
A two-phase cooling structure with expanding channels is employed, featuring an interposer cold plate with counter-flow arranged expanding channels that have different flow directions and widths, allowing for effective heat dissipation from both sides of the chip stack without the need for a central hole, and a manifold for coolant distribution and collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water cooling systems are used on the backside of the chip stack, then cooling capability is improved, but integration complexity increases and isolation of TSVs from liquid coolant is required
Solution Approach 1:
The patent employs two-phase cooling using liquid dielectric fluid that evaporates and condenses within integrated channels. The coolant is pumped through channels, evaporates at hot spots to form vapor, which then rises and condenses on cooler surfaces, creating a self-sustaining thermal cycle that eliminates the need for complex water cooling systems and TSV isolation
Solution Approach 2:
The patent utilizes phase transitions of dielectric fluid between liquid and vapor states for heat transfer. The liquid coolant evaporates at elevated temperatures to absorb heat, forming vapor that rises and condenses on cooler surfaces, releasing latent heat. This phase change mechanism provides efficient cooling without requiring complex integration or TSV isolation
2Device complexity
If single phase cooling with dielectric fluid is used, then TSV isolation is not required, but cooling performance is inferior to water
Solution Approach 1:
The patent transitions from single-phase dielectric fluid cooling to two-phase cooling by utilizing evaporation and condensation of the dielectric fluid. The liquid coolant evaporates at hot spots to absorb latent heat, and the resulting vapor condenses on cooler surfaces, providing superior cooling performance while maintaining integration simplicity and avoiding TSV isolation requirements
Solution Approach 2:
The patent introduces a vertical dimension to heat transfer by allowing vapor to rise and condense on upper surfaces of the chip stack. This three-dimensional heat transfer path, where liquid enters from below, evaporates, vapor rises, and condenses on top surfaces, significantly enhances cooling capability compared to conventional single-phase planar cooling
3Temperature
If radial expanding channels are used, then pressure drop and dry-out risk are reduced, but a central hole is required in the chip stack
Solution Approach 1:
The patent divides the cooling system into multiple independent linear channels distributed across the chip stack surfaces. Instead of a single central radial channel requiring a hole through the stack, multiple linear channels are segmented and distributed, with coolant entering through manifold structures at the edges and flowing through separate paths to various hot spots
Solution Approach 2:
The patent transitions from radial channels requiring vertical penetration to linear channels flowing in horizontal planes. The coolant flows linearly through channels that can be routed along the surfaces and edges of the chip stack, eliminating the need for central holes while maintaining the pressure drop and dry-out benefits of expanding channel geometry
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
This solution enhances heat removal capabilities, reduces pressure drops and vapor-liquid acceleration, maintains an annular regime with a thick evaporating film, and eliminates the need for a central inlet hole, thereby improving thermal management and stability in chip stacks.
Implementation Method 1
two-phase cooling in which a liquid coolant having a relatively low boiling point is used (e.g., liquid which evaporates at an operating temperature of the chips being used)
Implementation Method 2
heated evaporated coolant flows through confined channels to outlet ports
Data Source
AI summary
A structure for cooling an integrated circuit. The structure may include; an interposer cold plate having at least two expanding channels, each expanding channel having a flow direction from a channel inlet to a channel outlet, the flow direction having different directions for at least two of the at least two expanding channels, the channel inlet having an inlet width and the channel outlet having an outlet width, wherein the inlet width is less than the outlet width.