Cryostat Sample Board Flex Cable for Thermal Isolation and RF Shielding
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Solution Overview
Problem
Existing cryostat systems face challenges in maintaining cryogenic conditions while efficiently transmitting electrical signals and power from room temperature to low-pressure vacuum chambers without compromising thermal or electrical conductivity, and require flexible and cost-effective wiring solutions that balance these factors.
Innovation Solution
The development of multilayer flexible printed circuit cables with electromagnetic shielding and adjustable mounting mechanisms for quantum integrated circuits, utilizing copper for electrical conductivity and minimizing thermal conductivity through optimized mesh patterns and thermal anchors to maintain effective shielding and isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used to transmit electronic signals, then electrical conductivity is improved, but thermal conductivity increases causing heat transfer from room temperature to cryogenic region
Solution Approach 1:
The copper conductor is segmented into multiple smaller strands rather than using a single solid conductor. This segmentation reduces the total cross-sectional area of copper while maintaining electrical conductivity through parallel paths, thereby reducing thermal conductivity proportionally more due to the reduced overall copper volume and increased inter-strand thermal resistance.
Solution Approach 2:
The patent uses a composite structure combining copper strands with polyimide insulation and mesh shielding layers. This composite construction allows the copper to provide electrical conductivity while the polyimide and mesh structures provide thermal isolation and electromagnetic shielding, creating a balanced multi-functional cable system.
2Object-affected harmful factors
If electromagnetic shielding is added to protect signal lines, then electromagnetic interference protection is improved, but thermal conductivity and complexity increase
Solution Approach 1:
The mesh pattern serves multiple functions simultaneously: it provides electromagnetic shielding for signal protection, acts as a thermal barrier to reduce heat transfer, and maintains flexibility of the cable assembly. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing complexity.
Solution Approach 2:
The electromagnetic shield is implemented as a mesh pattern rather than a solid continuous shield. This porous structure provides sufficient electromagnetic shielding through the mesh geometry while allowing flexibility in the cable and reducing the amount of conductive material needed, thus balancing shielding effectiveness with mechanical flexibility and thermal management.
3Loss of energy
If vacuum sealing is implemented to maintain cryogenic conditions, then thermal isolation is improved, but electrical signal transmission from room temperature becomes difficult
Solution Approach 1:
The flexible cable assembly acts as an intermediary that bridges the vacuum-sealed cryogenic region and the room-temperature environment. It provides electrical signal transmission through its conductive elements while the polyimide insulation and mesh shielding provide thermal isolation, allowing signals to pass through the vacuum barrier without compromising the thermal seal.
Solution Approach 2:
The cable uses flexible polyimide insulation and mesh structures that can accommodate the vacuum seal interface. These flexible components allow the cable to maintain electrical connectivity while adapting to the vacuum chamber geometry and seal requirements, enabling signal transmission without compromising vacuum integrity.
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 enables efficient transmission of electrical signals and power while maintaining cryogenic conditions, reducing energy loss and enhancing component reliability and functionality by balancing thermal and electrical performance, thus optimizing the cryostat system's operational efficiency.
Implementation Method 1
a first plurality of spring loaded mounting screws adapted to mechanically fasten the PCB to the contact plate suspending it therefrom to allow for differential thermal expansion and contraction
Implementation Method 2
allow for differential thermal expansion and contraction
Implementation Method 3
Copper is most often used to transmit electronic signals, but as stated supra, it is also used as a good thermal conductor
Implementation Method 4
it is also used as a good thermal conductor. Note that thermal conductivity and electrical conductivity are related by the Wiedemann-Franz law
Implementation Method 5
The two outer layers serve as electromagnetic shields while the two inner layers comprise the signal lines which typically require electromagnetic shielding
Implementation Method 6
The mesh preferably minimizes conductivity while still providing sufficient RF shielding. Thus, the cable enables effective shielding by optimizing the scale and size of the mesh, while minimizing the total cross sectional area of copper running up and down the flex cables, and therefore its thermal conductivity.
Data Source
AI summary
A novel and useful system wiring apparatus and related techniques that address the need to feed power and electronic signals to and from a sample board between the cold, low pressure region in a vacuum chamber and outside room temperature and atmospheric pressure. The wiring apparatus balances electrical resistance with the thermal conductivity of the power and signal conductors. Printed flexible cables are used having an annular sealing region which together with O-rings provide vacuum sealing while allowing electrical signals to pass between integrated circuit(s) inside the vacuum chamber and equipment outside the chamber. A thermal anchor is placed along the printed flexible cable to maintain a desired temperature along the cable. The printed flexible circuits are multilayer with two outer layers serving as an RF shield while two inner layers comprise the signal lines which typically require shielding, electrical isolation from each other and from external electromagnetic fields.