A cryogenic packaging structure and thermal management method for a topological qubit array

Abstract

The application discloses a low-temperature packaging structure and a thermal management method of a topological quantum bit array. The structure comprises a packaging substrate, a heat sink, a thermal isolation layer, a signal interconnection layer, a temperature sensor and a temperature control unit. The method comprises the following steps: installing a topological quantum chip on the packaging substrate, integrating the heat sink on the back of the packaging substrate, mounting the packaging substrate on a cold finger of a dilution refrigerator, reducing heat conduction through the thermal isolation layer, monitoring the temperature in real time through the temperature sensor, and adjusting the refrigeration power through the temperature control unit to maintain the temperature stability. The application realizes efficient low-temperature packaging and thermal management of the topological quantum bit array, and the temperature uniformity is better than ±1mK, and the application can be widely used in the fields of system-level integration and low-temperature testing of topological quantum computing chips.

Description

Technical Field

[0001] This invention relates to the fields of quantum computing and chip packaging technology, specifically to a low-temperature packaging structure and thermal management method for topological quantum bit arrays. This invention is particularly applicable to scenarios involving low-temperature packaging, heat sink integration, temperature uniformity control, and package-level signal integrity maintenance for topological quantum computing chips. Background Technology

[0002] Topological qubits require extremely low temperatures to maintain the coherence of their quantum states. Cryogenic packaging structures not only need to provide mechanical support and electrical connections, but also need to effectively manage heat conduction between the chip and the dilution refrigerator to ensure the uniformity and stability of the chip temperature. However, as the scale of qubit arrays increases, the thermal management challenges faced by cryogenic packaging become increasingly severe. Existing cryogenic packaging technologies can be mainly classified into the following categories: (a) Wire bonding package The quantum chip's pads are connected to the pins of the packaging substrate using gold or aluminum wires. This approach has the following problems: (1) the number of wires increases linearly with the number of qubits, making wiring difficult; (2) the thermal conductivity of the wires causes heat to be conducted from room temperature to the chip; (3) the parasitic capacitance between the wires affects the signal quality; and (4) the reliability of wire bonding in large-scale arrays decreases. (ii) Flip Chip Packaging Quantum chips are flip-chip connected to the packaging substrate via solder bumps. This approach has the following problems: (1) thermal expansion mismatch of solder bumps leads to stress; (2) the heat conduction path between bumps is complex; (3) rework is difficult and yield is low; (4) reliability of solder at low temperatures. (III) Multilayer ceramic encapsulation High-density interconnection is achieved using multilayer ceramic substrates. This type of solution has the following problems: (1) the low thermal conductivity of the ceramic substrate makes thermal management difficult; (2) the manufacturing cycle of multilayer ceramics is long and the cost is high; (3) the thermal expansion coefficients of ceramics and silicon chips are mismatched; (4) the size of the substrate is limited. (iv) Flexible connector packaging The chip is connected to the external circuit by means of a flexible cable. This type of solution has the following problems: (1) the insertion loss of the flexible cable is large; (2) the mechanical connection reliability is poor; (3) the signal integrity is limited by the cable length; (4) it is difficult to achieve large-scale parallel connection. In summary, the common fundamental deficiency of existing cryogenic packaging technologies lies in the lack of a cryogenic packaging structure and thermal management method for topological quantum bit arrays that can simultaneously achieve low thermal conductivity, high interconnect density, and good temperature uniformity. Summary of the Invention

[0003] (a) Purpose of the invention This invention provides a low-temperature packaging structure and thermal management method for topological qubit arrays, aiming to solve the technical problems of difficult thermal management, low interconnection density, and poor temperature uniformity in existing low-temperature packaging. (II) Technical Principles This invention is based on the principle of heat conduction. In this invention, thermal management of cryogenic packaging is achieved through the following physical chain: Heat sink integration: A high thermal conductivity heat sink is integrated on the back of the packaging substrate. The heat generated by the quantum chip is quickly conducted to the cold finger of the dilution refrigerator through the heat sink, reducing heat accumulation. Thermal isolation design: A thermal isolation layer is placed between the quantum chip and the packaging substrate to reduce heat conduction from the room temperature end to the chip end, while maintaining the reliability of the electrical connection. Temperature uniformity: Through the structural design of the heat sink, the temperature distribution on the chip surface is made uniform, avoiding local hot spots that could lead to performance degradation of the qubits. Signal integrity preservation: Impedance matching and shielding design of the packaged interconnects ensure the transmission quality of high-frequency control signals. The fundamental difference from existing technologies: This invention is not a "simple wire bonding" solution, but rather achieves thermal management optimization for low-temperature packaging through heat sink integration, thermal isolation, and temperature homogenization. (III) Technical Solution A low-temperature packaging structure for a topological quantum bit array, characterized in that it comprises: Packaging substrate, used to support topological quantum chips; A heat sink, disposed on the back side of the packaging substrate, is used to conduct heat to the cold finger of the dilution refrigerator; A thermal isolation layer is disposed between the packaging substrate and the topological quantum chip to reduce heat conduction; A signal interconnect layer is disposed above the thermal isolation layer and is used to realize the signal connection between the quantum chip and external circuits; A temperature sensor, mounted on the packaging substrate or quantum chip, is used to monitor temperature distribution; A temperature control unit, connected to the temperature sensor, is used to adjust the cooling power of the dilution refrigerator. A low-temperature packaging thermal management method for a topological quantum bit array, characterized by comprising the following steps: S1: The topological quantum chip is mounted on a packaging substrate, and a heat sink is integrated on the back of the packaging substrate; S2: The packaging substrate is mounted on the cold finger of the dilution refrigeration machine, and thermal contact is achieved through the heat sink; S3: Reduces heat conduction from room temperature to the chip through a thermal isolation layer; S4: Real-time monitoring of chip temperature distribution via temperature sensor; S5: The temperature control unit adjusts the cooling power based on the monitoring results to maintain a stable chip temperature. (iv) Beneficial effects First, the integrated heat sink enables efficient heat conduction, ensuring that the chip operates at the target temperature. Second, the thermal insulation layer reduces parasitic heat conduction and lowers the cooling load. Third, temperature sensors and temperature control units enable closed-loop temperature management. Fourth, the signal interconnection layer supports high-density signal connections to meet the needs of large-scale arrays. Fifth, the packaging structure is compatible with dilution refrigeration machines and can be directly integrated into existing cryogenic systems. Detailed Implementation

[0004] Example 1 (Copper heat sink low-temperature packaging structure) Step 1: Prepare the packaging substrate. High-resistivity silicon or ceramic is selected as the packaging substrate material, with substrate size ranging from 10mm×10mm to 50mm×50mm. Step 2: Integrate the heat sink. Integrate a copper heat sink, 1-5mm thick, on the back of the packaging substrate by soldering or bonding, so that it is in direct contact with the cooling fingers of the dilution refrigerator. Step 3: Install a thermal isolation layer. An thermal isolation layer with a thermal conductivity ≤ 0.5 W / (m·K) is installed between the packaging substrate and the quantum chip. Step 4: Fabrication of the signal interconnect layer. A signal interconnect layer is fabricated above the thermal isolation layer, and the quantum chip is electrically connected to the packaging substrate via wire bonding or flip-chip bonding. Step 5: Install a temperature sensor. Install a temperature sensor on the packaging substrate or quantum chip to monitor the temperature in real time. Step 6: Integrate the temperature control unit. The temperature control unit adjusts the cooling power of the dilution refrigerator based on feedback from the temperature sensor to maintain the chip temperature within the range of 10-100mK. Example 2 (Diamond heat sink cryogenic encapsulation structure) Using diamond as a heat sink material instead of copper offers advantages such as higher thermal conductivity and a lower coefficient of thermal expansion, resulting in superior thermal management performance. Example 3 (Multilayer Signal Interconnect Package) High-density signal interconnection is achieved by using a multilayer ceramic substrate. Hundreds of control signals are led out from the chip to the package pins through multilayer wiring, supporting the packaging of large-scale quantum bit arrays. Example 4 (Integrated Heat Pipe Packaging) By integrating a micro heat pipe structure inside the packaging substrate, phase change heat transfer is utilized to improve heat conduction efficiency and further improve temperature uniformity. Attached Figure Description

[0005] Figure 1 This is a cross-sectional schematic diagram of the low-temperature packaging structure of the topological quantum bit array of the present invention. Figure 2 This is a schematic diagram illustrating the principle of heat sink integration and thermal management in this invention. Figure 3 This is a schematic diagram of the temperature sensor distribution and temperature control of the present invention. Figure 4 This is a flowchart of the low-temperature packaging thermal management method of the present invention. Figure 5 This is a schematic diagram of a typical application scenario of the present invention. Terminology Explanation

[0006] Low-temperature packaging: A packaging structure that encapsulates quantum chips and provides electrical connectivity and thermal management in an extremely low-temperature environment. Heat sink: A thermally conductive structure that transfers heat from the chip to a cold source. Dilution refrigeration unit: Refrigeration equipment that provides extremely low temperature environments below 10mK. Thermal insulation layer: A thermal insulation layer placed between a heat source and a cold source to reduce heat conduction.

Claims

1. Claim 1: A low-temperature packaging structure for a topological qubit array, characterized in that, include: Packaging substrate, used to support topological quantum chips; A heat sink, disposed on the back side of the packaging substrate, is used to conduct heat to the cold finger of the dilution refrigerator; A thermal isolation layer is disposed between the packaging substrate and the topological quantum chip to reduce heat conduction; A signal interconnect layer is disposed above the thermal isolation layer and is used to realize the signal connection between the quantum chip and external circuits; A temperature sensor, mounted on the packaging substrate or quantum chip, is used to monitor temperature distribution; A temperature control unit, connected to the temperature sensor, is used to adjust the cooling power of the dilution refrigerator.

2. Claim 2: The structure according to claim 1 is characterized in that, The heat sink is made of at least one of copper, diamond, or aluminum nitride, with a thermal conductivity ≥100 W / (m·K).

3. Claim 3: The structure according to claim 1 is characterized in that, The thermal conductivity of the thermal insulation layer is ≤0.5W / (m·K), and the thickness is 10-100μm.

4. Claim 4: The structure according to claim 1 is characterized in that, The number of temperature sensors is 2-10, distributed in the center, edge and corner areas of the packaging substrate.

5. Claim 5: The structure according to claim 1 is characterized in that, The operating temperature of the encapsulation structure is 10-100mK, and the temperature uniformity is better than ±1mK.

6. Claim 6: A low-temperature packaging thermal management method for topological qubit arrays, characterized in that, Includes the following steps: S1: The topological quantum chip is mounted on a packaging substrate, and a heat sink is integrated on the back of the packaging substrate; S2: The packaging substrate is mounted on the cold finger of the dilution refrigeration machine, and thermal contact is achieved through the heat sink; S3: Reduces heat conduction from room temperature to the chip through a thermal isolation layer; S4: Real-time monitoring of chip temperature distribution via temperature sensor; S5: The temperature control unit adjusts the cooling power based on the monitoring results to maintain a stable chip temperature.

7. Claim 7: The method according to claim 6, characterized in that, The thermal contact between the heat sink and the cold finger in step S2 is achieved by indium foil or thermally conductive adhesive.

8. Claim 8: The method according to claim 6, characterized in that, The sampling frequency of temperature monitoring in step S4 is ≥10Hz, and the temperature measurement accuracy is better than ±1mK.

9. Claim 9: The method according to claim 6, characterized in that, The method also includes integrating a micro heat pipe structure inside the packaging substrate to improve heat conduction efficiency by utilizing phase change heat transfer.

10. Claim 10: The structure according to claim 1 is characterized in that, The signal interconnection layer supports the interconnection of 64 to 4096 independent signals.

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