Cryogenic IC Thermal Sink Layout for Multi-Temperature Cooling
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Solution Overview
Problem
Cryogenic MMICs face inefficiencies in thermal management due to the need to maintain all components at the most stringent operating temperature, leading to excessive cooling resource requirements, as heat laterally spreads across a single ground plane, necessitating cooling of devices that require different operational temperatures.
Innovation Solution
Implementing multiple thermal sink layers and dedicated ground planes for different temperature requirements, coupled via thermally conductive vias, allowing each thermal sink layer to be cooled at a specific temperature to maintain the respective ground planes and circuits at their desired operating temperatures, reducing the need for uniform cooling to the lowest temperature across the entire device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single ground plane is used to maintain uniform temperature across the MMIC, then temperature uniformity is improved, but cooling resource requirements increase significantly
Solution Approach 1:
The single ground plane is segmented into multiple ground planes, each associated with different thermal sink layers at different temperatures. This allows each segment to be cooled to its specific operational temperature requirement rather than cooling the entire MMIC to the lowest temperature, thereby reducing overall cooling resource requirements while maintaining temperature stability for each device type.
Solution Approach 2:
Different regions of the MMIC are assigned different thermal characteristics through dedicated thermal sink layers and ground planes. Each local region is cooled to the specific temperature required by its associated devices, rather than applying uniform cooling across the entire chip. This local quality approach optimizes cooling resources by matching temperature control to actual device needs.
2Reliability
If the entire MMIC is cooled to the lowest operational temperature (500 mK), then all devices can operate, but energy consumption increases by more than 8 times for devices that only require 4K cooling
Solution Approach 1:
The MMIC is divided into multiple temperature zones with separate ground planes and thermal sink layers. Devices requiring 500mK operation are isolated on one ground plane cooled to 500mK, while devices requiring only 4K operation are on another ground plane cooled to 4K. This segmentation prevents the 8x energy penalty by avoiding unnecessary over-cooling of devices that don't require the lowest temperature.
Solution Approach 2:
The temperature parameter is changed locally for different ground planes rather than maintaining a uniform temperature across the entire MMIC. Each ground plane is assigned a specific temperature parameter matching its devices' operational requirements, enabling energy-efficient operation by eliminating the need to cool all devices to the most stringent temperature requirement.
3Loss of energy
If thermally conductive vias are used to couple ground planes to thermal sink layers, then thermal management efficiency is improved, but device complexity increases
Solution Approach 1:
Thermally conductive vias act as intermediary elements coupling the ground planes to the thermal sink layers. These via structures provide efficient thermal pathways from each ground plane to its corresponding thermal sink layer, enabling effective heat removal while maintaining the multi-temperature-zone architecture. The via intermediaries resolve the contradiction by providing a practical implementation mechanism for the thermal management system.
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 approach reduces the overall cooling power requirements by allowing each thermal sink layer to be cooled at a temperature appropriate for its associated ground plane's operational needs, optimizing thermal management and reducing energy consumption.
Implementation Method 1
a first thermally conductive via that couples the first ground plane to the first thermal sink layer... a second thermally conductive via that couples the second ground plane to the second thermal sink layer
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An integrated circuit is provided that comprises a first thermal sink layer, a first ground plane associated with a first set of circuits that have a first operational temperature requirement, a first thermally conductive via that couples the first ground plane to the first thermal sink layer, a second thermal sink layer, a second ground plane associated with a second set of circuits that have a second operational temperature requirement that is higher than the first operational temperature requirement, and a second thermally conductive via that couples the second ground plane to the second thermal sink layer. The first thermal sink layer is cooled at a first temperature to maintain the first set of circuits at the first operational temperature requirement and the second thermal sink layer is cooled at a second temperature to maintain the second set of circuits at the second operational temperature requirement.