Preparation equipment for palladium-plated bonding wire rod blank

Abstract

The utility model provides equipment for preparing a palladium-plated bonding wire rod blank. The equipment comprises a closed smelting system, a vacuumizing system, a protective gas system, a clamping guide system and a palladium-plated composite component, the closed smelting system is used for providing a closed smelting space; the vacuumizing system is used for communicating with the closed smelting system and vacuumizing the smelting space; the protective gas system is used for injecting protective gas into the smelting space; the clamping and guiding system is used for clamping the palladium-plated composite assembly and guiding the lower end of the palladium-plated composite assembly into the smelting containing cavity, a suction pipeline is further arranged in the clamping and guiding system, and molten liquid in the smelting containing cavity can enter the palladium-plated composite assembly under the action of negative pressure so as to form a palladium-plated bonding wire rod blank. Due to the existence of a closed space, vacuum and protective gas, the palladium plating stability is ensured; the oxidation process is avoided through multiple times of vacuumizing operation, so that the palladium-plated bonding wire has excellent mechanical and electrical properties, and the influence on the environment is small due to separation from the environment.

Description

Technical Field

[0001] The utility model relates to the technical field of chip packaging, and specifically, to a preparation device for a palladium-plated bonding wire rod blank. Background Art

[0002] With the development of electronic packaging towards miniaturization, multi-function and low cost, the packaging industry has put forward higher requirements for packaging forms and packaging materials. Wire bonding is the earliest chip packaging technology, which realizes the interconnection between devices and their packages through metal wires.

[0003] Gold is a traditional type of bonding wire, but its electrical and thermal conductivity properties make its application in high-density and fine-pitch packaging more challenging. At the same time, the cost of gold wire is constantly increasing, resulting in the gradual marginalization of the application of gold.

[0004] Copper has higher electrical and thermal conductivity than gold, and its cost is also much lower than that of gold, making copper a new bonding wire material that is widely accepted. However, since copper wire is extremely easy to oxidize in the environment, the oxidation barrier layer technology is an important way to solve the problem of easy oxidation of bare copper wire.

[0005] Among many oxidation barrier layer (gold, silver, palladium, nickel) technologies, palladium-plated copper wire has become the most potential bonding wire to replace gold wire due to its good bondability and reliability.

[0006] Currently, the production of palladium-plated copper bonding wire generally uses electroplating and electroless plating technologies. It is to continuously cast copper into a wire rod blank, and then carry out on-line electroplating or electroless plating on the copper bonding wire after rough drawing, medium drawing and fine drawing. These two technologies cause relatively serious environmental pollution, and at the same time, the investment in equipment and workshops is relatively large, and the production efficiency is low. On the one hand, it increases the production cost, and on the other hand, it also brings great pressure to the ecological environment.

[0007] In order to develop a green and environmentally friendly production process for palladium-plated copper bonding wire, people have been seeking an ideal technical solution. Summary of the Utility Model

[0008] The purpose of the utility model is to overcome the deficiencies of the prior art, and thus provide a preparation device for a palladium-plated bonding wire rod blank that is green and environmentally friendly, has low production costs, and excellent quality.

[0009] In order to achieve the above purpose, the technical solution adopted by the utility model is: a preparation device for a palladium-plated bonding wire rod blank, including a closed melting system, a vacuum pumping system, a protective gas system, a clamping and guiding system, and a palladium plating composite component;

[0010] The closed melting system is used to provide a closed melting space, and the melting space is provided with a melting cavity and a heating component for heating the melting cavity;

[0011] The evacuation system is used to connect to a closed melting system and evacuate the melting space.

[0012] The protective gas system is used to inject protective gas into the melting space.

[0013] The clamping and guiding system is used to clamp the palladium-plated composite component and introduce the lower end of the palladium-plated composite component into the melting cavity. An extraction pipeline communicating with the palladium-copper composite component is also provided in the clamping and guiding system. The extraction pipeline is connected to the evacuation system or an additional negative pressure extraction component. The molten liquid in the melting cavity can enter the palladium-plated composite component under the action of negative pressure to form a palladium-plated bonding wire rod blank.

[0014] Based on the above, the palladium-plated composite component includes a high-purity graphite tube and a pure palladium tube.

[0015] The high-purity graphite tube is the outer tube. The pure palladium tube is closely attached to the inner wall of the high-purity graphite tube and fixed at the lower part of the high-purity graphite tube. A support step is provided in the high-purity graphite tube for the pure palladium tube.

[0016] Based on the above, a position detection sensor is provided at the upper part of the inner wall of the palladium-plated composite component. The position detection sensor is used to detect the rising liquid level of the copper melt. The position detection sensor is associated with the evacuation system or an additional negative pressure extraction component externally connected to the extraction pipeline in the clamping and guiding system, so as to stop the extraction action after the melt rises to the set liquid level.

[0017] Based on the above, the palladium-plated composite component further includes a support tube. The support tube is closely attached to the inner wall of the high-purity graphite tube and fixed at the top of the high-purity graphite tube. A gap is left between the lower end of the support tube and the top end of the pure palladium tube. The position detection sensor is installed at the lower end of the support tube.

[0018] Based on the above, the position detection sensor is a thermal sensor or a pressure-sensitive sensor.

[0019] Based on the above, the clamping and guiding system includes a connecting sleeve. The connecting sleeve is externally sealed and penetrates through the top end of the closed melting system to conduct the inside and outside of the melting space. The extraction pipeline is connected to the outer end of the connecting sleeve.

[0020] Based on the above, the clamping and guiding system further includes a lifting mechanism and a movable sealing ring. The lifting mechanism is used to drive the connecting sleeve to lift and lower. The connecting sleeve is hermetically and movably matched with the closed melting system through the movable sealing ring.

[0021] Based on the above, the closed smelting system includes a closed smelting furnace, the top of the smelting furnace is equipped with a furnace cover, and the connecting sleeve is cooperatively installed with the furnace cover through a movable sealing ring; a smelting space is formed inside the smelting furnace, the smelting cavity is a high-purity graphite crucible, and the heating assembly is installed in the base of the high-purity graphite crucible. The heating assembly adopts an intermediate frequency heating unit with a working frequency of 1 kHz to 5 kHz and has an electromagnetic stirring function.

[0022] Based on the above, the vacuum pumping system includes a diffusion pump and a mechanical pump group. The diffusion pump is directly connected to the smelting furnace, and the mechanical pump group is communicated with the connecting sleeve through a suction pipe, and the suction pipe is a vacuum corrugated pipe.

[0023] The present utility model has substantial features and progress compared with the prior art. Specifically, the present utility model has the following advantages:

[0024] 1. From the equipment level, compared with the high pollution problem of the solution existing in the physical combination of traditional electroplating and electroless plating of palladium, the present utility model uses vacuum extraction of the plating material melt to metallurgically combine with the palladium tube under the condition of gas protection, and the whole process occurs in a closed and evacuated smelting space, minimizing the environmental impact.

[0025] 2. By using the method of negative pressure suction of the copper melt to directly metallurgically combine with the palladium tube, the coating has higher stability and is not easy to fall off.

[0026] 3. The present utility model uses a primary vacuum pumping to obtain a basic vacuum degree, uses a secondary vacuum pumping and injection of protective gas to protect the plating material melt, and then uses a method of three-time suction of the plating material melt to achieve three-time vacuum degassing, so that the gas content of the plating material in the bonding wire blank is greatly reduced, improving the mechanical and electrical properties of the palladium-plated bonding wire.

[0027] 4. In the design of the palladium tube, a pressure-sensitive or thermosensitive sensor is used to sense whether the copper melt rises in place, thereby controlling the degree of vacuum pumping; the method of wrapping the palladium tube with an outer layer of high-purity graphite tube is used to maintain the executability of the metallurgical bonding process between the palladium tube and the plating material melt; a support tube is used to improve the structural strength of the palladium tube so as to be stably connected with the connecting sleeve; the easy-to-crack and non-reactive characteristics of the high-purity graphite tube are used to simplify the process of finally removing the high-purity graphite tube, obtaining a stable bonded palladium-plated bonding wire rod blank. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the preparation equipment for the palladium-plated bonding wire rod blank in the present utility model.

[0029] Figure 2 is a schematic structural diagram of the palladium tube clamping part in the preparation equipment for the palladium-plated bonding wire rod blank in the present utility model.

[0030] Figure 3 It is a cross-sectional view of the palladium-plated bonding wire rod blank in the present utility model.

[0031] Figure 4 It is an actual product drawing of the bonding surface of the palladium-plated bonding wire rod blank in the present utility model.

[0032] Figure 5 It is a performance comparison diagram between the palladium-plated copper bonding wire in the present utility model and a commercially available 20-μm palladium-plated copper bonding wire.

[0033] In the figure: 1. Melting furnace; 2. High-purity graphite crucible; 3. Palladium-copper composite device; 4. Furnace cover; 5. Movable sealing ring; 6. Suction pipeline; 7. Mechanical pump set; 8. Locking ring; 9. Diffusion pump; 10. Argon gas tank; 11. Connecting sleeve; 12. High-purity graphite tube; 13. Rubber ring; 14. Support steel pipe; 15. Pure palladium tube; 16. Crucible base; 17. Intermediate frequency heating unit; 18. Lifting mechanism; 19. Copper. Specific embodiments

[0034] Next, through specific embodiments, the technical solutions of the present utility model will be further described in detail.

[0035] In this embodiment, the preparation of the palladium-plated copper bonding wire rod blank is taken as an example for illustration. Except for copper, in other embodiments, it can be correspondingly replaced with other materials such as silver to form a palladium-plated silver bonding wire rod blank, etc.

[0036] As Figure 1 and Figure 2 shown, a preparation device for a palladium-plated bonding wire rod blank includes a closed melting system, a vacuum pumping system, a protective gas system, a clamping and guiding system, and a palladium-copper composite device 3.

[0037] In this embodiment, the closed melting system is used to provide a closed melting space, specifically including a closed melting furnace 1. The top of the melting furnace 1 is provided with a furnace cover 4, and the furnace cover 4 and the melting furnace 1 are sealed by a locking ring 8 and a sealing ring. A melting space is formed inside the melting furnace 1, and a melting cavity and a heating component for heating the melting cavity are arranged inside. In this embodiment, the melting cavity adopts a high-purity graphite crucible 2, and the heating component selects an intermediate frequency heating unit 17. Since the principle of the intermediate frequency heating unit 17 is electromagnetic heating, under the drive of electromagnetic force, electromagnetic force stirring of the copper melt can also be realized.

[0038] In other embodiments, the closed melting system can also select other types of closed melting spaces, such as other types of kilns, etc. The melting cavity can select other types of crucibles, the heating component can select electric heating, and the stirring component can select a common stirring structure or an independent electromagnetic stirring mechanism.

[0039] The vacuum pumping system is used to connect to the closed smelting system and evacuate the smelting space. In this embodiment, the vacuum pumping system mainly includes a diffusion pump 9 and a mechanical pump set 7. The diffusion pump 9 is directly connected to the smelting furnace 1, and the mechanical pump set 7 is connected to the smelting furnace 1 through a vacuum bellows, a clamping and guiding system, and a palladium-copper composite device 3.

[0040] In the mechanical pump set, a rotary vane pump is designed. The rotary vane pump is used to extract the copper melt and obtain a vacuum. The rotary vane pump can maintain the vacuum degree when it stops, thereby ensuring the stability of the copper melt in the pure palladium tube.

[0041] In other embodiments, the vacuum pumping system can also adopt other types of vacuum pump combinations.

[0042] The protective gas system is used to inject a protective gas into the smelting space. In this embodiment, argon is used as the protective gas, and an external argon gas tank 10 is connected. In other embodiments, other types of inert gases can also be selected as the protective gas.

[0043] The clamping and guiding system is used to clamp the pure palladium tube and introduce the lower end of the pure palladium tube into the smelting cavity. A suction pipeline 6 communicating with the inner tube of the pure palladium tube is also arranged in the clamping and guiding system. In this embodiment, a vacuum bellows is selected, and the suction pipeline 6 communicates with the mechanical pump set 7.

[0044] In this embodiment, the end of the clamping and guiding system is a connecting sleeve 11. In this embodiment, the connecting sleeve 11 is made of a steel sleeve. The outer part of the connecting sleeve 11 is hermetically inserted through the top of the closed smelting system to conduct the inside and outside of the smelting space, and the suction pipeline 6 is connected to the outer end of the connecting sleeve 11.

[0045] In this embodiment, the palladium-copper composite device 3 is kept vertical in the smelting furnace 1, its lower end faces the high-purity graphite crucible 2, and its upper end is connected to the connecting sleeve 11. The copper melt is attracted into the palladium-copper composite device 3 by the action of the suction force.

[0046] Specifically, in a preferred embodiment, a position detection sensor (not shown in the figure) is arranged on the upper part of the inner wall of the palladium-copper composite device 3. The position detection sensor is used to detect the rising liquid level of the copper melt. The position detection sensor is associated with the vacuum pumping system or an additional negative pressure suction component externally connected to the suction pipeline 6 in the clamping and guiding system, so as to stop the suction action after the copper 19 melt rises to the set liquid level. In this embodiment, a thermal or pressure-sensitive sensor can be selected as the position detection sensor. In other embodiments, a contact type or optical type position detection sensor can also be selected.

[0047] To protect the safety of the palladium tube and maintain its vertical state, the palladium-copper composite device 3 includes a high-purity graphite tube 12 and a pure palladium tube 15; the high-purity graphite tube 12 is the outer tube, and the pure palladium tube 15 is closely attached to the inner wall of the high-purity graphite tube 12 and fixed at the lower part of the high-purity graphite tube 12. A support step is provided in the high-purity graphite tube for the pure palladium tube, aiming to lock the position of the pure palladium tube 15, and at the same time, to avoid the direct contact between the pure copper melt and the pure palladium tube to damage the pure palladium tube 15, and to provide a channel for the copper melt to rise. During the rising process, the copper melt combines with the pure palladium tube as it cools.

[0048] In a preferred embodiment, to protect the clamping stability of the high-purity graphite tube 12, the palladium-copper composite device 3 further includes a support tube 14. The support tube 14 is closely attached to the inner wall of the high-purity graphite tube 12 and fixed at the top of the high-purity graphite tube 12. A section of interval is left between the lower end of the support tube 14 and the top end of the pure palladium tube 15. The in-place detection sensor is installed at the lower end of the support tube 14. In this embodiment, to ensure the stability of the support tube, its material is selected as steel to form a support steel tube.

[0049] The position where the support tube 14 is located cooperates with the connecting sleeve 11, serving as the end structure of the clamping and guiding system. The cooperation between the two can use a rubber ring 13 to fill the gap, which can ensure the sealing performance on the one hand and protect the high-purity graphite tube 12 from damage on the other hand.

[0050] In a preferred embodiment, in order to keep the palladium-copper composite device 3 away from the copper melt during the heating process of the copper melt and immerse the palladium-copper composite device 3 into the copper melt after the copper melt is heated, a lifting mechanism 18 and a movable sealing ring 5 are added to the clamping and guiding system. The lifting mechanism 18 is used to drive the connecting sleeve 11 to lift and lower. The connecting sleeve 11 is hermetically and movably matched with the closed melting system through the movable sealing ring 5. The movable sealing ring 5 can be a threaded ring, and the locking and sealing of the connecting sleeve are achieved by loosening and tightening.

[0051] The process of preparing the palladium-plated bonding wire rod blank using the above-mentioned preparation equipment for the palladium-plated bonding wire rod blank is as follows:

[0052] Step 1) Open the furnace lid and put high-quality electrolytic copper plates with a purity of more than 99.99% into the high-purity graphite crucible;

[0053] Step 2) Close the furnace lid, turn on the mechanical pump group and diffusion pump in sequence until the vacuum degree reaches 1*10 -2 Pa or more, then turn off the vacuum pumping system in sequence, open the argon valve of the protective gas system, and introduce high-purity argon until the vacuum degree in the furnace is 0.05 Mpa, and then close the argon valve;

[0054] Step 3) Turn on the intermediate frequency heating, preheat for 5 - 10 minutes with a power of 5 - 10 kw, then increase the power to 15 - 20 kw until the raw materials are completely melted;

[0055] Step 4) Increase the power to 30 - 35 kw, stir the copper melt using electromagnetic force, and keep it at a temperature of 1100 - 1150 °C;

[0056] Step 5) Turn on the mechanical pump set to pump the vacuum to 1 - 10 Pa, then introduce high-purity argon gas into it until the vacuum degree in the furnace reaches 0.01 Mpa, and then close the argon gas valve;

[0057] Step 6) Unscrew the sealing nut above the furnace cover, start the lifting mechanism, insert the graphite tube 10 - 20 mm away from the bottom of the high-purity graphite crucible, and then tighten the sealing nut above the furnace cover;

[0058] Step 7) Turn off the intermediate frequency induction heating, turn on the rotary vane pump in the mechanical pump set to pump the copper melt. When the copper melt touches the pressure-sensitive or thermosensitive sensor at the bottom of the support steel pipe, turn off the rotary vane pump, and the copper melt solidifies and composites with the pure palladium tube on the inner wall of the high-purity graphite tube;

[0059] Step 8) After the crucible is completely cooled, unscrew the sealing nut above the furnace cover, use the lifting mechanism to raise the high-purity graphite tube, remove the graphite tube, break it, and saw off the head and tail along the edge of the palladium tube to obtain the palladium-plated bonding wire rod blank, as Figure 3 shown.

[0060] Comparison of impurity content of palladium-copper composite rod blanks:

[0061] Use an oxygen-nitrogen-hydrogen analyzer to analyze the oxygen, nitrogen, and hydrogen in the traditional vacuum gas-protected continuous casting copper rod and the copper core of the palladium-copper composite rod blank of the present invention. The oxygen, nitrogen, and hydrogen content of the present invention is far lower than that of the traditional method, and the present invention improves the cleanliness of the palladium-copper composite rod blank.

[0062]

[0063] Interface bonding: As Figure 4 shown, the interface bonding of the palladium-copper composite rod is good.

[0064] One of the performance comparison examples of the bonding wire:

[0065] Compare the 20 μm palladium-plated copper bonding wire prepared by the scheme of the present invention ( Figure 5 a and b in) with the commercially available 20 μm palladium-plated copper bonding wire ( Figure 5 c and d in). The coating surface of the palladium-plated copper bonding wire prepared by the present invention is flat, smooth, uniform, and without obvious defects, while the commercially available palladium-plated copper bonding wire has slight unevenness, and even has coating peeling, copper exposure, or pore defects, which will seriously affect the performance of the palladium-plated copper bonding wire.

[0066] The Second Comparative Example of Bonding Wire Performance:

[0067] During the wire bonding process, the working conditions of the bonding wire are very complex. Especially for the bonding wire on a high-speed automatic wire bonder, it is required that the bonding wire has higher breaking force and elongation. For the bonding wire, its breaking force and elongation play a key role in the quality of wire bonding. A bonding wire with high breaking force and elongation is more conducive to bonding.

[0068] Using the YG001 B single-fiber electronic tensile tester, the breaking force and elongation of the 20μm palladium-plated copper bonding wire prepared by the solution of the present invention and the commercially available 20μm palladium-plated copper bonding wire are measured respectively. Taking the average value of 10 samples, the breaking force of the palladium-plated bonding wire prepared by the solution of the present invention is 6.8 cN, while the breaking force of the commercially available palladium-plated copper bonding wire is 5.4 cN; the elongation of the palladium-plated bonding wire prepared by the solution of the present invention is 10.6%, while the elongation of the commercially available palladium-plated copper bonding wire is 9.3%. The breaking force and elongation of the palladium-plated copper bonding wire prepared by the present invention are higher than those of the commercially available palladium-plated copper bonding wire.

[0069] The Third Comparative Example of Bonding Wire Performance:

[0070] According to the metal conduction theory, the reason why metal has resistance is that the electron wave is scattered, and the scattering of the electron wave often occurs where the integrity of the crystal lattice is damaged. According to this principle, Matthiessen's Rule expresses the resistivity (ρ) of metal as: ρ = ρ r + ρ t , ρ r is the resistivity related to impurities and lattice defects (point defects, line defects and surface defects), and ρ t is the resistivity related to temperature. Taking the average value of 10 samples, the resistivity of the palladium-plated bonding wire prepared by the solution of the present invention is 0.01716 Ω·mm 2 / m, while the resistivity of the commercially available palladium-plated copper bonding wire is 0.01717 Ω·mm 2 / m. The resistivity of the palladium-plated bonding wire prepared by the solution of the present invention is slightly lower than that of the commercially available palladium-plated copper bonding wire.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A preparation device for a palladium-plated bonding wire rod blank, characterized in that: It includes a closed melting system, a vacuum pumping system, a protective gas system, a clamping and guiding system, and a palladium-plated composite component; The closed melting system is used to provide a closed melting space, and the melting space is provided with a melting cavity and a heating component for heating the melting cavity; The vacuum pumping system is used to communicate with the closed melting system and evacuate the melting space; The protective gas system is used to inject protective gas into the melting space; The clamping and guiding system is used to clamp the palladium-plated composite component and introduce the lower end of the palladium-plated composite component into the melting cavity. A suction pipeline communicating with the palladium-copper composite component is also arranged in the clamping and guiding system. The suction pipeline communicates with the vacuum pumping system or an additional negative pressure suction component, and is used to suck the molten liquid in the melting cavity into the palladium-plated composite component under the action of negative pressure to form a palladium-plated bonding wire rod blank.

2. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 1, characterized in that: The palladium-plated composite component includes a high-purity graphite tube and a pure palladium tube; The high-purity graphite tube is the outer tube, the pure palladium tube is closely attached to the inner wall of the high-purity graphite tube and fixed at the lower part of the high-purity graphite tube, and a support step is arranged in the high-purity graphite tube for the pure palladium tube.

3. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 1 or 2, characterized in that: A position detection sensor is arranged at the upper part of the inner wall of the palladium-plated composite component. The position detection sensor is used to detect the rising liquid level of the copper molten liquid. The position detection sensor is associated with the vacuum pumping system or an additional negative pressure suction component externally connected to the suction pipeline in the clamping and guiding system, so as to stop the suction action after the molten liquid rises to the set liquid level.

4. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 3, characterized in that: The palladium-plated composite component further includes a support tube. The support tube is closely attached to the inner wall of the high-purity graphite tube and fixed at the top of the high-purity graphite tube. A section of interval is left between the lower end of the support tube and the top end of the pure palladium tube, and the position detection sensor is installed at the lower end of the support tube.

5. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 4, characterized in that: The position detection sensor is a thermal sensor or a pressure sensor.

6. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 1, characterized in that: The clamping and guiding system includes a connecting sleeve. The connecting sleeve is externally sealed and passes through the top end of the closed melting system to conduct inside and outside the melting space, and the suction pipeline is connected to the outer end of the connecting sleeve.

7. The preparation equipment for a palladium-plated bonding wire rod blank according to claim 6, characterized in that: The clamping and guiding system further includes a lifting mechanism and a movable sealing ring. The lifting mechanism is used to drive the connecting sleeve to lift and lower, and the connecting sleeve is hermetically and movably matched with the closed melting system through the movable sealing ring.

8. The preparation equipment for a palladium-plated bonding wire rod blank according to claim 6 or 7, characterized in that: The closed melting system includes a closed melting furnace. The top end of the melting furnace is configured with a furnace cover, and the connecting sleeve is installed in cooperation with the furnace cover through the movable sealing ring; the melting space is formed inside the melting furnace, the melting cavity is a high-purity graphite crucible, and the heating component is installed in the base of the high-purity graphite crucible. The heating component adopts an intermediate frequency heating unit with a working frequency of 1 kHz to 5 kHz and has an electromagnetic stirring function.

9. The preparation equipment for the palladium-plated bonding wire rod blank according to claim 8, characterized in that: The vacuum pumping system includes a diffusion pump and a mechanical pump group. The diffusion pump is directly connected to the melting furnace, and the mechanical pump group is communicated with the connecting sleeve through a suction pipe, and the suction pipe is a vacuum corrugated pipe.

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