Lead bonding method and manufacturing method of superconducting quantum chip and superconducting quantum chip

Abstract

The invention discloses a lead bonding method and a manufacturing method of a superconducting quantum chip and the superconducting quantum chip. The lead bonding method comprises the following steps: forming a plurality of mutually contacted first welding spots at different positions of a first metal bonding pad on a printed circuit board (PCB) for packaging the superconducting quantum chip by using metal welding wires; sequentially forming a plurality of mutually contacted second welding spots at different positions of a second metal bonding pad of the superconducting quantum chip body by using a metal welding wire; wire arcs are pulled out from the second welding spots to the corresponding first welding spots, the tail ends of the wire arcs are welded to the first welding spots, the metal welding wires are cut off, and one-to-one bonding of the multiple first welding spots and the multiple second welding spots is achieved. Reliability, stability and welding quality of welding spots are improved by adopting a hot ball bonding technology, mechanical interlocking and current distribution optimization can be realized by adopting a structure that a plurality of welding spots are in contact with one another, and performance, stability and reliability of superconducting quantum chip packaging are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of superconducting quantum technology, and in particular to a wire bonding method, manufacturing method, and superconducting quantum chip. Background Technology

[0002] In the field of quantum computing, superconducting quantum chips are the core components of superconducting quantum computers.

[0003] A crucial step in the fabrication of superconducting quantum chips is the wire bonding and packaging process. This process involves bonding the printed circuit board (PCB) used for packaging the superconducting quantum chip to the pads on the superconducting quantum chip body using wire bonding, and then packaging the bonded chip.

[0004] Since superconducting quantum chips require effective electrical connections with external circuits, wire bonding packaging technology enables signal transmission between the internal superconducting circuitry and external measurement and control circuits. Furthermore, packaging the wire-bonded chip provides a relatively stable physical environment, protecting it from damage caused by external factors.

[0005] Currently, the mainstream wire bonding process for aluminum-based superconducting quantum chips employs silicon-aluminum wire wedge bonding technology. This is because aluminum is a commonly used superconducting material in superconducting quantum circuits (such as Transmon qubits) (consistent with the chip electrode material), avoiding thermal noise and non-superconducting interface problems caused by dissimilar metal contacts. However, traditional aluminum wire wedge bonding has the following inherent drawbacks:

[0006] 1. Lower welding reliability: Wedge welding relies on pressure and ultrasonic friction to form a bond. Its mechanical strength and electrical contact stability are weaker than the metal fusion bonding method of ball welding, and it is prone to failure under low temperature cycling.

[0007] 2. Limited wire bonding directionality: Wedge bonding requires wires to emerge in a specific direction, making it difficult to achieve high-density, multi-dimensional interconnects and limiting chip layout flexibility.

[0008] 3. High solder joint impedance: Insufficient deformation of the metal at the wedge weld interface results in high contact resistance, introducing additional microwave loss and affecting the coherence time of the quantum bits. Summary of the Invention

[0009] In view of the above problems, the present invention is proposed to provide a wire bonding method, manufacturing method and superconducting quantum chip for overcoming or at least partially solving the above problems.

[0010] In a first aspect, embodiments of the present invention provide a wire bonding method for a superconducting quantum chip, comprising:

[0011] Using metal solder wire, multiple first solder points are formed at different positions on the first metal solder pad on the printed circuit board (PCB) for packaging superconducting quantum chips; the multiple first solder points are in contact with each other.

[0012] Using metal welding wire, multiple second solder points are sequentially formed at different positions on the second metal solder pad of the superconducting quantum chip body, and the multiple second solder points are in contact with each other; an arc is drawn from each second solder point to the corresponding first solder point, the end of the arc is welded to the corresponding first solder point, and the metal welding wire is cut, so as to achieve bonding of multiple first solder points on the first metal solder pad to multiple second solder points on the second metal solder pad one by one.

[0013] In one embodiment, before forming a plurality of first weld points and a plurality of second weld points using metal welding wire, the method further includes:

[0014] The first and second metal pads are cleaned using a fixed-point argon plasma to remove surface contaminants and metal oxide layers.

[0015] In one embodiment, in the step of cleaning the first metal pad and the second metal pad using fixed-point argon plasma, the power of the plasma generator used is 50-300W, and the cleaning time is 10-30 seconds.

[0016] In one embodiment, multiple first solder joints are formed at different locations on a first metal pad using a metal solder wire, including:

[0017] The following operations are performed sequentially at different positions of the first metal pad to form a plurality of first solder joints on the first metal pad: above the first metal pad, the heat generated by activating a tip current melts the metal welding wire to form a first solder ball, the first solder ball is melted and welded to the corresponding position of the first metal pad to form a corresponding first solder joint, and the metal welding wire is cut off.

[0018] During the above operation, the first solder joints formed at multiple different locations on the first metal pad come into contact with each other.

[0019] In one embodiment, above the first metal pad, heat generated by activating a tip current melts a metal welding wire to form a first solder ball, and the first solder ball is melted and welded to the corresponding position of the first metal pad to form a corresponding first solder joint, including:

[0020] Insert the metal welding wire into the cleaver of the ball welding machine and move the cleaver above the first metal welding pad;

[0021] The following operations are performed sequentially at multiple different locations on the first metal pad:

[0022] By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire into a first welding ball.

[0023] The cutting tool is pressed down to make the first solder ball contact the corresponding position of the first metal pad;

[0024] Ultrasonic energy is applied and sustained for a period of time to complete the fusion welding of the first solder ball and the first metal pad, forming the first solder joint corresponding to the first solder ball.

[0025] In one embodiment, a plurality of second weld points are sequentially formed at different positions on a second metal pad using a metal welding wire, the plurality of second weld points being in contact with each other; an arc is drawn from each second weld point toward a first weld point corresponding to the second weld point, the end of the arc is welded to the corresponding first weld point, and the metal welding wire is cut, including:

[0026] The following operations are performed sequentially at different positions on the second metal pad: Above the second metal pad, the heat generated by activating a tip current melts the metal welding wire to form a second solder ball; the formed second solder ball is melted and welded to the corresponding position on the second metal pad to form a corresponding second solder point; the metal welding wire holding the second solder ball is moved towards the first solder point corresponding to the second solder point to pull out a corresponding arc until it moves to the corresponding first solder point, and the end of the arc is welded to the corresponding first solder point; the metal welding wire is cut off; during the above operations, the second solder points formed at multiple different positions on the second metal pad come into contact with each other.

[0027] In one embodiment, the heat generated by activating a tip current melts the metal welding wire to form a second solder ball; the formed second solder ball is then melt-welded to the second metal pad to form a corresponding second solder joint, including:

[0028] Move the cleaver above the second metal pad;

[0029] By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire and form a second welding ball.

[0030] The cutting tool is pressed down to make the second solder ball contact the corresponding position of the second metal pad;

[0031] Ultrasonic energy is applied and sustained for a period of time to complete the welding of the second solder ball to the second metal pad, forming the second solder joint.

[0032] In one embodiment, the process parameters for capacitor discharge include: the capacitance of the capacitor discharge power supply is 50–500 μF, the voltage is 1000–5000 V, and the capacitor discharge time is 0.5–5 ms.

[0033] In one embodiment, the capacitor discharge power supply has a capacitance of 200μF, a voltage of 3000V, and a capacitor discharge time of 2ms.

[0034] In one embodiment, the metal welding wire holding the second welding ball is moved towards the corresponding first welding point to draw out a corresponding arc until it reaches the corresponding first welding point, and the end of the arc is welded to the corresponding first welding point, including:

[0035] The metal welding wire is held by a chopping blade, and the chopping blade rises to stretch the metal welding wire into an arc, moving it toward the first welding point corresponding to the second welding point.

[0036] When the blade moves to the corresponding first weld point, it presses down to bring the arc line into contact with the first weld point.

[0037] Ultrasonic energy is applied and sustained for a period of time until the arc is successfully welded to the first metal pad.

[0038] In one embodiment, after welding the end of the arc to the corresponding first weld point and cutting the metal welding wire, the method further includes:

[0039] Adjusting the capacitor discharge parameters causes the spark bar below the cleaver to generate a tip current, melting the end of the metal welding wire after it has been cut into a spherical shape.

[0040] In one embodiment, before forming a plurality of first weld points and a plurality of second weld points using metal welding wire, the method further includes:

[0041] The first and second metal pads are cleaned using a fixed-point argon plasma to remove surface contaminants and metal oxide layers.

[0042] In one embodiment, the ratio of the diameter of the first welding ball to the diameter of the metal welding wire is 1.5 to 3:1;

[0043] The ratio of the diameter of the second welding ball to the diameter of the metal welding wire is 1.5 to 3:1.

[0044] In one embodiment, the height of the arc from the second metal pad is 100–300 µm; the spacing between adjacent arcs is 10–30 µm.

[0045] In one embodiment, the metal welding wire is aluminum wire.

[0046] Secondly, embodiments of the present invention provide a method for manufacturing a superconducting quantum chip, the method comprising a step of bonding a printed circuit board (PCB) for packaging the superconducting quantum chip to the superconducting quantum chip body via wire bonding;

[0047] The wire bonding process is implemented using the wire bonding method for superconducting quantum chips as described above.

[0048] Thirdly, embodiments of the present invention provide a superconducting quantum chip, comprising: a superconducting quantum chip body, a PCB for superconducting quantum chip packaging, and a packaging box; the superconducting quantum chip body is stacked on the PCB; the superconducting quantum chip body and the PCB are packaged inside the packaging box;

[0049] The PCB is provided with a first metal pad; the first metal pad has a plurality of first solder joints that are in contact with each other;

[0050] The superconducting quantum chip body is provided with a second metal pad; the second metal pad has multiple second solder joints that are in contact with each other;

[0051] The plurality of first solder joints that are in contact with each other are bonded to the plurality of second solder joints that are in contact with each other by a metal wire arc.

[0052] In one embodiment, the superconducting quantum chip is obtained by the superconducting quantum chip manufacturing method described above.

[0053] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0054] In the wire bonding method for superconducting quantum chips provided in this embodiment of the invention, hot-ball bonding technology is used. Multiple first solder joints are formed by pre-planting balls at multiple different locations on the PCB used for packaging the superconducting quantum chip. Then, second solder joints are formed by ball bonding at multiple different locations on the superconducting quantum chip body. Wires are then led to the corresponding first solder joints on the PCB used for packaging the superconducting quantum chip to complete the welding. This process is repeated until the welding between each first solder joint and its corresponding second solder joint is completed. Compared to traditional wedge bonding technology, hot-ball bonding technology allows both the first and second solder joints to withstand higher shear forces, resulting in better reliability, stability, and welding quality, significantly improving the performance, stability, and reliability of the superconducting quantum chip packaging. Furthermore, for the superconducting quantum chip body and PCB, the parallel electrical connection formed by multiple solder joints (multiple first solder joints or multiple second solder joints) in contact with each other can achieve mechanical interlocking and current distribution optimization. Among them, mechanical interlocking ensures the stability of the physical structure of the parallel connection between multiple solder joints, preventing one solder joint from detaching due to mechanical stress. Even if a single solder joint suffers minor mechanical damage or electrical defects, other solder joints can still maintain mechanical fixation and current transmission, avoiding overall package failure and significantly improving the long-term operational reliability of the superconducting quantum chip. Current distribution optimization reduces microwave loss, avoids local overheating, and ensures signal fidelity.

[0055] Furthermore, before forming the first and second solder joints, this invention can use targeted argon plasma technology to clean the first and second metal pads respectively, removing surface contaminants and metal oxide layers. This effectively solves the problem of surface contamination and oxide layer removal in small areas without damaging microstructures such as Josephson junctions on superconducting quantum chips, laying a high-quality surface foundation for subsequent bonding and welding processes. Experiments have shown that the surface energy of the first and second metal pads after cleaning can be increased to 60-70 mN / m, and the shear strength between the solder ball and the pad can be increased by more than 50%.

[0056] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0057] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0058] Figure 1 This is an overall flowchart of the wire bonding method for the superconducting quantum chip in an embodiment of the present invention;

[0059] Figure 2 This is a schematic diagram of the fusion welding after the first solder ball comes into contact with the first metal solder pad when the wedge is pressed down in an embodiment of the present invention;

[0060] Figure 3a This is a schematic diagram of the formation of a second welding ball at the end of the metal welding wire in an embodiment of the present invention;

[0061] Figure 3b This is a schematic diagram showing the second solder ball descending above the second metal pad of the superconducting quantum chip body in an embodiment of the present invention;

[0062] Figure 3c This is a schematic diagram illustrating the fusion welding of the second solder ball and the second metal pad in an embodiment of the present invention;

[0063] Figure 3d This is a schematic diagram of the cleaving blade rising in an embodiment of the present invention;

[0064] Figure 3e This is a schematic diagram of a metal welding wire being stretched into an arc, a cleaver being pressed down, and the arc being welded to a first welding point on a first metal welding pad in an embodiment of the present invention.

[0065] Figure 4A schematic diagram of the process flow for bonding three first solder joints on a PCB for packaging a superconducting quantum chip and three second solder joints on the superconducting quantum chip body via wire bonding, as provided in an embodiment of the present invention.

[0066] Figure 5 This is a schematic diagram of a single first solder joint, a single second solder joint, and a wire arc after wire bonding packaging in an embodiment of the present invention. Detailed Implementation

[0067] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0068] The inventors of this invention have discovered that in superconducting quantum chips, existing technologies often use silicon-aluminum wire wedge bonding. This technology has problems such as potential for incomplete soldering, reduced bond strength, or even breakage at deformation points, resulting in low reliability, limited wire directionality, and high solder joint impedance. These issues make the fabricated superconducting quantum chips prone to failure during later use, seriously affecting the performance, stability, and reliability of the superconducting quantum chips.

[0069] To address the aforementioned issues, this invention employs heated ball bonding technology in the wire bonding step of the superconducting quantum chip fabrication process to improve wire bonding quality and ensure packaging reliability.

[0070] Before describing the wire bonding method for the superconducting quantum chip provided in the embodiments of the present invention, a brief description of the common structure of superconducting quantum chips will be given first.

[0071] A packaged superconducting quantum chip typically includes: the superconducting quantum chip body, the PCB for packaging the superconducting quantum chip, and the packaging box;

[0072] In the structure of a common superconducting quantum chip, the superconducting quantum chip body is usually stacked on a PCB and attached to a predetermined position on the PCB (such as the center of the PCB) by means of adhesive, for example. The superconducting quantum chip body and the PCB are encapsulated inside the superconducting quantum chip by a package.

[0073] The packaging box may include an upper cover and a lower cover, with the lower cover connected to the PCB by means of soldering, bonding, or other methods.

[0074] In the package, the pads on the superconducting quantum chip body (hereinafter referred to as the second metal pads) are bonded to the pads on the PCB (hereinafter referred to as the first metal pads) by wire bonding.

[0075] The wire bonding process for superconducting quantum chips is one of the many processes involved in manufacturing superconducting quantum chips. It involves bonding the PCB used for packaging the superconducting quantum chip to the pads on the superconducting quantum chip body using wire bonding.

[0076] Specifically, embodiments of the present invention provide a wire bonding method for a superconducting quantum chip, the method referring to... Figure 1 As shown, the method includes the following steps:

[0077] S11. Using metal solder wire, multiple first solder points are formed at different positions on the first metal solder pad on the printed circuit board (PCB) for packaging superconducting quantum chips; the multiple first solder points are in contact with each other.

[0078] S12. Using metal welding wire, multiple second welding points are sequentially formed at different positions of the second metal welding pad of the superconducting quantum chip body, and the multiple second welding points are in contact with each other.

[0079] S13. Pull out an arc wire from each second solder point to the first solder point corresponding to the second solder point, weld the end of the arc wire to the corresponding first solder point, and cut the metal welding wire to achieve bonding of multiple first solder points on the first metal solder pad to multiple second solder points on the second metal solder pad one by one.

[0080] In one embodiment, before steps S11-S13 above, the following steps may be performed:

[0081] The first and second metal pads are cleaned using fixed-point argon plasma (Ar plasma) to remove surface contaminants and metal oxide layers.

[0082] Point-to-point Ar plasma technology is a process that uses precisely controlled argon plasma to clean, activate, or modify the surface of specific micro-regions (such as the second metal pad on a superconducting quantum chip or the first metal pad on a printed circuit board (PCB) for packaging a superconducting quantum chip). This process utilizes the physicochemical properties of argon plasma to solve problems such as surface contamination and oxide layer removal in micro-regions without damaging the Josephson junction structure of the superconducting quantum chip, thus laying a high-quality surface foundation for subsequent bonding and welding processes.

[0083] In one embodiment, when using targeted Ar plasma to locally clean the solder pads before soldering, the process parameters can be selected as follows: plasma power 50-300 W, processing time 10-30 s.

[0084] Experiments have shown that cleaning the first and second metal pads using targeted Ar plasma technology can avoid damage to the Josephson junction of the superconducting quantum chip caused by overall plasma bombardment. The surface energy of the first and second metal pads can be increased to 60~70 mN / m (the increase in surface energy means that the surfaces of the first and second metal pads are transformed into highly active and easily bonded surfaces), and the shear strength between the solder balls and the pads can be increased by more than 50%.

[0085] For example, a plasma generator can be used to clean the surfaces of the first and second metal pads.

[0086] In one embodiment, steps S11-S13 in the above process flow, in specific implementation, involve an execution system including:

[0087] 1. Controllable atmosphere chamber (nitrogen / argon environment, oxygen content <10ppm), the entire bonding process is completed in a protective atmosphere, such as nitrogen or argon, to avoid metal wire melting and bonding interface oxidation, and to ensure the stability of the superconducting critical temperature (Tc≈1.2K).

[0088] 2. Precision capacitor discharge power supply (parameter range: capacitance 50~500 μF, voltage 1000~5000 V, discharge time 0.5~5 ms);

[0089] 3. Metal wire feeding mechanism (metal wire diameter 15~50 μm, purity ≥99.99%).

[0090] 4. High-frequency plasma generator (Ar plasma, frequency 13.56 MHz, power 50-300 W);

[0091] 5. Three-dimensional high-precision motion platform (positioning accuracy ±1μm).

[0092] In one embodiment, step S11 above is performed on the ball placement operation of the first solder joint in the following manner:

[0093] The following operations are performed sequentially at different positions of the first metal pad to form a plurality of first solder joints on the first metal pad: above the first metal pad, the heat generated by activating a tip current melts the metal welding wire to form a first solder ball, the first solder ball is melted and welded to the corresponding position of the first metal pad to form a corresponding first solder joint, and the metal welding wire is cut off.

[0094] During the aforementioned multiple operations, the first solder joints formed at multiple different locations on the first metal pad come into contact with each other.

[0095] Multiple first solder joints formed at different locations are in contact with each other, enabling parallel electrical connection through lateral contact between the multiple first solder joints. This effectively reduces the risk of failure of a single solder joint, reduces microwave loss, extends the coherence time of the quantum bit, and improves the reliability of low-temperature cycling.

[0096] In one embodiment, the formation process of each first solder joint includes the following steps:

[0097] 1.1) Insert the metal welding wire into the cleaver of the ball welding machine and move the cleaver above the first metal welding pad;

[0098] The following operations are performed sequentially at multiple different locations on the first metal pad:

[0099] 1.2) By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire into a first welding ball;

[0100] Specifically, the melting into the first welding ball can be achieved by: bringing one end of the capacitor discharge device into contact with the metal welding wire, and connecting the other end to the ignition rod. By applying a voltage of a certain frequency and power through the capacitor discharge device, an instantaneous ignition phenomenon is generated, melting the end of the metal welding wire into a ball and keeping it connected to the unmelted metal welding wire.

[0101] 1.3) Press down with the cutting tool to make the first solder ball contact the corresponding position of the first metal pad;

[0102] 1.4) Apply ultrasonic energy and continue for a period of time to complete the fusion welding of the first solder ball and the first metal pad, forming the first solder joint corresponding to the first solder ball.

[0103] In the process of forming multiple first solder joints, a three-dimensional high-precision motion platform is used to move multiple different positions, so that the cutting tool can form multiple first solder joints that are in contact with each other at different positions of the first metal solder pad.

[0104] A schematic diagram of the fusion welding after the first solder ball contacts the first metal pad when the cleaver is pressed down can be found in the image. Figure 2 As shown, Figure 2 The left side is a schematic diagram, and the right side shows a microscopic photograph of the first solder ball formed after the lower end of the welding wire comes into contact with the first metal pad.

[0105] In one embodiment, the step of cutting the metal welding wire can be achieved by clamping it with a wire clamp to break the metal welding wire.

[0106] In one embodiment, steps S12-S13 are further implemented in the following manner:

[0107] The following operations are performed sequentially at different positions of the second metal pad: above the second metal pad, the heat generated by activating a tip current melts the metal welding wire to form a second solder ball; the formed second solder ball is melted and welded to the corresponding position of the second metal pad to form a corresponding second solder joint;

[0108] The metal welding wire holding the second welding ball is moved towards the first welding point corresponding to the second welding point, and the corresponding arc is pulled out until it moves to the corresponding first welding point. The end of the arc is then welded to the corresponding first welding point. The metal welding wire is then cut off.

[0109] During the aforementioned multiple operations, the second solder joints formed at multiple different locations on the second metal pad come into contact with each other.

[0110] The process of forming multiple second solder joints at different locations on the second metal pad described above is similar to the process of forming multiple first solder joints on the first metal pad. The number of second solder joints is the same as the number of first solder joints, and they correspond one-to-one.

[0111] After each second solder joint is formed, it needs to be bonded to the corresponding first solder joint via a wire. Then, the next second solder joint is formed, and the next second solder joint is bonded to the corresponding first solder joint via a wire. This process is repeated N times (N equals the number of first solder joints or second solder joints) until all second solder joints are soldered and the second solder joints are bonded to their corresponding first solder joints.

[0112] For each second solder joint, its generation process and the bonding process with the first solder joint via a lead wire can be implemented in the following specific way:

[0113] 2.1) Move the cleaver above the second metal pad of the superconducting quantum chip body;

[0114] 2.2) By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire and form a second welding ball;

[0115] The second solder ball can be generated in a similar manner to step 1.2 above, and will not be described again here.

[0116] 2.3) Press down the cutting tool to make the second solder ball contact the corresponding position of the second metal pad;

[0117] 2.4) Apply ultrasonic energy and continue for a period of time to complete the fusion welding of the second solder ball and the second metal pad, forming the second solder joint.

[0118] 2.5) The metal welding wire is held by the chopping blade, and the chopping blade rises to stretch the metal welding wire into an arc, moving it towards the first welding point corresponding to the second welding point;

[0119] 2.6) When the blade moves to the corresponding first weld point, it presses down to bring the arc line into contact with the first weld point;

[0120] 2.7) Apply ultrasonic energy and continue for a period of time until the arc is successfully welded to the first metal pad.

[0121] 2.8) Cut the metal welding wire.

[0122] The purpose of the above-mentioned wire bonding process is to connect the second metal pad on the superconducting quantum chip body to the corresponding first metal pad on the PCB for packaging the superconducting quantum chip by means of wires.

[0123] In practice, steps 1.1-1.4 and 2.1-2.7 above can be performed on ball bonding equipment, such as a wire bonding machine.

[0124] In one embodiment, the specific process of steps 2.1-2.7 above can be referred to Figures 3a-3e shown. Specifically, Figure 3a The image shows the ignition rod completing the melting ball operation of the metal welding wire, forming a second welding ball at the end of the metal welding wire; Figure 3b The image shows the second solder ball being lowered by a cleaver to above the second metal pad of the superconducting quantum chip body; Figure 3c The diagram shows the second solder ball being pressed down by the cleaver and coming into contact with the corresponding position of the second metal pad, thus completing the fusion welding to form the second solder point; Figure 3d The diagram shows the cutting tool holding the metal welding wire and rising after the second weld point is formed; Figure 3e The diagram shows the process of the cutting blade rising and moving towards the first welding point, causing the metal welding wire to be stretched into an arc. Finally, the cutting blade presses down, and the arc contacts the first welding point, completing the welding of the arc to the first metal pad.

[0125] In the above Figures 3a-3e In the process shown, the wire clamp is used to fix the metal welding wire and keep the position of the metal welding wire stable throughout the wire bonding process.

[0126] After step 2.7 above, the metal welding wire needs to be cut (step 2.8), and then the cutter is raised. Repeat steps 2.1-2.8 again to complete the wire bonding between the next second solder point and the corresponding first solder point, until the wire bonding process between all second solder points and the corresponding first solder points is completed.

[0127] In one embodiment, after step 2.8 during each wire bonding process, the following operation may also be performed: adjust the parameters of capacitor discharge to excite the tip current of the spark bar below the cleaver, melting the end left after the metal welding wire is cut into a spherical shape.

[0128] Specifically, adjusting the parameters of capacitor discharge, such as reducing capacitance, voltage, or shortening discharge time (requiring lower voltage and capacitance and shorter discharge time than required for the balling process), aims to use low energy to melt only a small portion of the aluminum wire tip (not the high temperature and pressure required for integral balling or bonding), melting the tip left after cutting the metal wire into a spherical shape. The advantages of this operation are twofold: firstly, because steps 2.2-2.8 are repeated, the spherical tip formed after each bonding can be easily used for the next welding (i.e., repeating the "balling → bonding → cutting → tip processing" process), ensuring consistency in subsequent balling processes (e.g., maintaining a consistent ball diameter and wire diameter ratio). Secondly, low-energy discharge forming a spherical tip avoids problems such as wire metal oxidation and material waste caused by overheating.

[0129] In the wire bonding method for superconducting quantum chips provided in this embodiment of the invention, hot-ball bonding technology is used. Multiple first solder joints are formed by pre-planting balls at multiple different locations on the PCB used for packaging the superconducting quantum chip. Then, second solder joints are formed by ball bonding at multiple different locations on the superconducting quantum chip body. Wires are then led to the corresponding first solder joints on the PCB used for packaging the superconducting quantum chip to complete the welding. This process is repeated until the welding between each first solder joint and its corresponding second solder joint is completed. Compared to traditional wedge bonding technology, hot-ball bonding technology allows both the first and second solder joints to withstand higher shear forces, resulting in better reliability, stability, and welding quality, significantly improving the performance, stability, and reliability of the superconducting quantum chip packaging. Furthermore, for the superconducting quantum chip body and PCB, the parallel electrical connection formed by multiple solder joints (multiple first solder joints or multiple second solder joints) in contact with each other can achieve mechanical interlocking and current distribution optimization. Among them, mechanical interlocking ensures the stability of the physical structure of the parallel connection between multiple solder joints, preventing one solder joint from detaching due to mechanical stress. Even if a single solder joint suffers minor mechanical damage or electrical defects, other solder joints can still maintain mechanical fixation and current transmission, avoiding overall package failure and significantly improving the long-term operational reliability of the superconducting quantum chip. Current distribution optimization reduces microwave loss, avoids local overheating, and ensures signal fidelity.

[0130] To ensure the efficiency and quality of hot-ball bonding, in one embodiment, prior to step S11 above, the present invention can also perform preheating of the superconducting quantum chip body and the metal welding wire to 120-200°C on a wire bonding machine.

[0131] In one embodiment, the metal wire used in the above-mentioned wire bonding process can be aluminum wire.

[0132] In one embodiment, the ratio of the diameter of the first welding ball to the diameter of the metal welding wire is 1.5 to 3:1;

[0133] The ratio of the diameter of the second welding ball to the diameter of the metal welding wire is 1.5 to 3:1.

[0134] In one embodiment, the height of the arc formed in step 2.5 above from the second metal pad is 100 to 300 µm; the distance between two adjacent arcs is 10 to 30 µm.

[0135] In one embodiment, in the ball-forming process of steps 1.2 and 2.2 above, the capacitor discharge parameters are: capacitance 50-500 μF, voltage 1000-5000 V, and discharge time 0.5-5 ms.

[0136] Preferably, through experiments, the following process parameters were adopted in the above steps 1.2 and 2.2: capacitor 200 μF, voltage 3000 V, discharge time 2 ms. Under these conditions, the sphericity of the aluminum ball is ≥95% and the surface oxide layer thickness is <2 nm.

[0137] This will be illustrated with a specific example of wire bonding technology.

[0138] Reference Figure 4 The process flow diagram shown in this specific example uses aluminum wire as the metal welding wire. Three corresponding solder points need to be formed on the PCB for packaging the superconducting quantum chip and on the superconducting quantum chip body, respectively, and wire bonding is used.

[0139] The specific implementation process is as follows:

[0140] Step 1: Pad pretreatment steps;

[0141] For example, using fixed-point Ar plasma technology, the second metal pad on the superconducting quantum chip body and the first metal pad on the PCB used for superconducting quantum chip packaging can be locally cleaned (processing time 10-30 s) to remove the surface aluminum oxide layer. (and organic pollutants, which activate metal surfaces.)

[0142] Specifically, the process parameters of the plasma generator are as follows: a 13.56 MHz RF source with a power of 30 W and an Ar flow rate of 100 sccm; a nozzle diameter of 1 mm, a distance from the pad of 2 mm, and a scanning speed of 5. Processing time: 0.5 s / point. After the process is completed, Sputtering removal rate 2 After treatment, the atomic ratio of oxygen (O) to carbon (C) on the surfaces of the first and second metal pads decreased from 0.9 to 0.15, the contact angle decreased from 65° to 12°, and there were no cold solder joints after the metal wires were formed into balls.

[0143] Step Two:

[0144] In a protective atmosphere of N2 and AR, the end of an aluminum wire is melted into a ball (1.5 to 3 times the wire diameter) by capacitor discharge, and then pressed onto the second metal pad of the superconducting quantum chip body to form a second solder joint (first solder). Subsequently, three aluminum balls in contact with each other are continuously soldered onto the same pad to form a "triangular stack" structure, achieving mechanical interlocking and optimized current distribution.

[0145] Step 3: Multi-line arc control;

[0146] Three independent arcs are drawn out using a three-dimensional high-precision motion platform, heading towards the first metal pad (second soldering position) of the printed circuit board (PCB) used for packaging superconducting quantum chips. The arc height is 100-300 μm and the arc spacing is 10-30 μm.

[0147] Step 4: Bonding between solder joints;

[0148] On the printed circuit board (PCB) for packaging superconducting quantum chips, three closely arranged aluminum spheres have been pre-formed using a ball-planting technique. In this step, the three arcs generated in step three are tangent to the sides of the corresponding aluminum spheres, and the two are bonded together by secondary capacitor discharge to form a "three-line, three-sphere" stacked interconnect structure.

[0149] Step 5: Tail wire treatment;

[0150] The aluminum wire is cut and a spherical end is formed through low-energy discharge to prepare for subsequent welding.

[0151] After each of the steps 2 to 5 above is completed, which involves "generating a second solder joint → bonding it with the corresponding first solder joint → cutting the metal welding wire → processing the end of the metal welding wire", the PCB and the superconducting quantum chip body are moved to the next position and the above process is repeated until all the second solder joints and their corresponding first solder joints are bonded together.

[0152] Reference Figure 5 As shown in the last step, the black square on the left represents the first metal pad on the printed circuit board (PCB) used for packaging the superconducting quantum chip, and the three gray balls on it represent the first solder joints at three different locations; the blue square on the right represents the second metal pad on the superconducting quantum chip body, and the three gray balls on it represent the second solder joints at three different locations; the three first solder joints and the three second solder joints are bonded together one by one by wires.

[0153] A schematic diagram of a single first solder joint, a single second solder joint, and a wire arc after the above wire bonding package can be found by referring to... Figure 5 As shown, in Figure 5 In the diagram, the yellow portion represents the superconducting quantum chip itself, the gray portion represents the PCB used for packaging the superconducting quantum chip, and the packaging box is not shown.

[0154] Based on the same inventive concept, embodiments of the present invention also provide a method for manufacturing a superconducting quantum chip, the superconducting quantum chip being packaged with a superconducting quantum chip body and a printed circuit board for superconducting quantum chip packaging; the manufacturing method of the superconducting quantum chip includes a step of bonding the printed circuit board to the superconducting quantum chip body by wire bonding; this step is implemented using the wire bonding method for superconducting quantum chips as described above.

[0155] This invention also provides a superconducting quantum chip, which includes: a superconducting quantum chip body, a PCB for superconducting quantum chip packaging, and a packaging box; the superconducting quantum chip body is stacked on the PCB; the superconducting quantum chip body and the PCB are packaged inside the packaging box; wherein:

[0156] The PCB for packaging a superconducting quantum chip has a first metal pad; the first metal pad has multiple first solder joints that are in contact with each other.

[0157] The superconducting quantum chip body is provided with a second metal pad; the second metal pad has multiple second solder joints that are in contact with each other;

[0158] The plurality of first solder joints that are in contact with each other are bonded to the plurality of second solder joints that are in contact with each other by a metal wire arc.

[0159] Reference Figure 4 In the example shown, multiple first solder joints that are in contact with each other form a one-to-one correspondence with the multiple second solder joints that are in contact with each other. Each pair of bonded first solder joints and second solder joints forms a complete circuit. Since the multiple first solder joints are in contact with each other and the multiple second solder joints are in contact with each other, the multiple first solder joints (multiple second solder joints) belong to the parallel branches of the same node. The multiple first solder joints form a parallel electrical connection with each other, and the multiple second solder joints also form a parallel electrical connection with each other.

[0160] From an electrical perspective, this structural design improves bonding reliability and avoids the impact of single-point failures on the performance and reliability of superconducting quantum chips. By adopting this parallel electrical connection, the total current can be evenly distributed to multiple branches, and the current density of each solder joint (the principle is similar for the first or second solder joint) is reduced to 1 / n of the original (where n is the number of the first or second solder joints). This design also makes the total contact resistance significantly lower than that of a single solder joint, which can greatly reduce local heat accumulation, reduce microwave signal loss during transmission, avoid quantum state decoherence due to resistance heating or signal attenuation, and ensure signal fidelity.

[0161] From the perspective of mechanical stress, the mechanical stress is also distributed to multiple first solder joints or multiple second solder joints, rather than concentrated on a single first solder joint or second solder joint. This reduces the risk of solder joints peeling off from the pads due to stress caused by temperature changes, achieves mechanical interlocking, improves the reliability of the structure, and enhances the reliability of low-temperature thermal cycling.

[0162] The structural relationship between the superconducting quantum chip body, the PCB for superconducting quantum chip packaging, and the packaging box can be referred to existing technologies and will not be repeated here.

[0163] In one embodiment, the superconducting quantum chip described above can be obtained by the manufacturing method of a superconducting quantum chip as described above.

[0164] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A wire bonding method for a superconducting quantum chip, characterized in that, include: Using metal welding wire, multiple first solder joints are formed at different positions on the first metal pad on the printed circuit board (PCB) for packaging superconducting quantum chips. The plurality of first solder points are in contact with each other; Using metal welding wire, multiple second solder points are sequentially formed at different positions on the second metal solder pad of the superconducting quantum chip body, and the multiple second solder points are in contact with each other. A wire arc is drawn from each second solder point to the corresponding first solder point, and the end of the wire arc is welded to the corresponding first solder point. The metal welding wire is then cut to achieve bonding of multiple first solder points on the first metal pad to multiple second solder points on the second metal pad.

2. The method as described in claim 1, characterized in that, Before forming multiple first weld points and multiple second weld points using metal welding wire, the method further includes: The first and second metal pads are cleaned using a fixed-point argon plasma to remove surface contaminants and metal oxide layers.

3. The method as described in claim 2, characterized in that, In the step of cleaning the first metal pad and the second metal pad using fixed-point argon plasma, the power of the plasma generator used is 50-300W, and the cleaning time is 10-30 seconds.

4. The method as described in claim 1, characterized in that, Multiple first solder joints are formed at different positions on a first metal pad using a metal solder wire, including: The following operations are performed sequentially at different positions of the first metal pad to form a plurality of first solder joints on the first metal pad: above the first metal pad, the heat generated by activating a tip current melts the metal welding wire to form a first solder ball, the first solder ball is melted and welded to the corresponding position of the first metal pad to form a corresponding first solder joint, and the metal welding wire is cut off. During the above operation, the first solder joints formed at multiple different locations on the first metal pad come into contact with each other.

5. The method as described in claim 4, characterized in that, Above the first metal pad, heat generated by activating a tip current melts the metal welding wire to form a first solder ball. The first solder ball is then melted and welded to the corresponding position of the first metal pad to form a corresponding first solder joint, including: Insert the metal welding wire into the cleaver of the ball welding machine and move the cleaver above the first metal welding pad; The following operations are performed sequentially at multiple different locations on the first metal pad: By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire into a first welding ball. The cutting tool is pressed down to make the first solder ball contact the corresponding position of the first metal pad; Ultrasonic energy is applied and sustained for a period of time to complete the fusion welding of the first solder ball and the first metal pad, forming the first solder joint corresponding to the first solder ball.

6. The method as described in claim 1, characterized in that, Multiple second weld points are sequentially formed at different positions on a second metal pad using a metal welding wire, with the multiple second weld points in contact with each other; an arc is drawn from each second weld point toward a corresponding first weld point, the end of the arc is welded to the corresponding first weld point, and the metal welding wire is cut, including: The following operations are performed sequentially at different positions on the second metal pad: Above the second metal pad, the heat generated by activating a tip current melts the metal welding wire to form a second solder ball; the formed second solder ball is melted and welded to the corresponding position on the second metal pad to form a corresponding second solder point; the metal welding wire holding the second solder ball is moved towards the first solder point corresponding to the second solder point to pull out a corresponding arc until it moves to the corresponding first solder point, and the end of the arc is welded to the corresponding first solder point; the metal welding wire is cut off; during the above operations, the second solder points formed at multiple different positions on the second metal pad come into contact with each other.

7. The method as described in claim 6, characterized in that, The heat generated by activating a tip current melts the metal welding wire to form a second solder ball; the formed second solder ball is then melted and welded to the second metal pad to form a corresponding second solder joint, including: Move the cleaver above the second metal pad; By discharging through a capacitor, the spark rod below the cleaver is energized with a tip current to melt the metal welding wire and form a second welding ball. The cutting tool is pressed down to make the second solder ball contact the corresponding position of the second metal pad; Ultrasonic energy is applied and sustained for a period of time to complete the fusion welding of the second solder ball and the second metal pad, forming the second solder joint.

8. The method as described in claim 5 or 7, characterized in that, The process parameters for capacitor discharge include: the capacitance of the capacitor discharge power supply is 50–500 μF, the voltage is 1000–5000 V, and the capacitor discharge time is 0.5–5 ms.

9. The method as described in claim 8, characterized in that, The capacitor discharge power supply has a capacitance of 200μF, a voltage of 3000V, and a capacitor discharge time of 2ms.

10. The method as described in claim 6, characterized in that, The metal welding wire holding the second welding ball is moved towards the corresponding first welding point, pulling out a corresponding arc until it reaches the corresponding first welding point. The end of the arc is then welded to the corresponding first welding point, including: The metal welding wire is held by a chopping blade, and the chopping blade rises to stretch the metal welding wire into an arc, moving it toward the first welding point corresponding to the second welding point. When the blade moves to the corresponding first weld point, it presses down to bring the arc line into contact with the first weld point. Ultrasonic energy is applied and sustained for a period of time until the arc is successfully welded to the first metal pad.

11. The method as described in claim 6, characterized in that, After welding the end of the arc to the corresponding first weld point and cutting the metal welding wire, the method further includes: Adjusting the capacitor discharge parameters causes the spark bar below the cleaver to generate a tip current, melting the end of the metal welding wire after it has been cut into a spherical shape.

12. The method according to any one of claims 4-11, characterized in that, The ratio of the diameter of the first welding ball to the diameter of the metal welding wire is 1.5 to 3:1; The ratio of the diameter of the second welding ball to the diameter of the metal welding wire is 1.5 to 3:

1.

13. The method according to any one of claims 1-11, characterized in that, The height of the arc from the second metal pad is 100–300 µm; the spacing between adjacent arcs is 10–30 µm.

14. The method according to any one of claims 1-11, characterized in that, The metal welding wire is aluminum wire.

15. A method for manufacturing a superconducting quantum chip, the method comprising a step of bonding a printed circuit board for packaging the superconducting quantum chip to the superconducting quantum chip body via wire bonding; characterized in that, The wire bonding process is implemented using the wire bonding method for superconducting quantum chips as described in any one of claims 1-14.

16. A superconducting quantum chip, comprising: A superconducting quantum chip body, a PCB for packaging the superconducting quantum chip, and a packaging box; the superconducting quantum chip body is stacked on the PCB; the superconducting quantum chip body and the PCB are packaged inside the packaging box; characterized in that: The PCB is provided with a first metal pad; the first metal pad has a plurality of first solder joints that are in contact with each other; The superconducting quantum chip body is provided with a second metal pad; the second metal pad has multiple second solder joints that are in contact with each other; The plurality of first solder joints that are in contact with each other are bonded to the plurality of second solder joints that are in contact with each other by a metal wire arc.

17. The superconducting quantum chip as described in claim 16, characterized in that, The superconducting quantum chip is obtained by the manufacturing method of the superconducting quantum chip as described in claim 15.

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