A 3D-MEMS probe and preparation method thereof

Abstract

The present invention provides a 3D-MEMS probe and a preparation method thereof, wherein the probe comprises a ceramic substrate, a cylinder, a cantilever beam structure and a needle tip; the needle tip is fixedly connected to the cylinder through the cantilever beam structure, and the cylinder is fixedly connected to the ceramic substrate. The preparation method comprises: (1) performing photolithography and wet etching on the substrate to obtain a needle tip structure blank; then sputtering a seed layer on the surface of the substrate; (2) growing a high-strength metal on the seed layer using electroplating technology, and then obtaining a needle tip structure by grinding; (3) performing photolithography, electroplating, and peeling on the needle tip structure to manufacture a cantilever beam structure; (4) welding a cylinder on the cantilever beam structure, and then fixing and connecting the ceramic substrate; (5) removing the seed layer by wet method, peeling the 3D structure probe from the substrate, and then collecting and cleaning it. The 3D-MEMS probe provided by the present invention has a simple structure and good reliability; and the preparation process is simple, and it is easy to process and mass produce.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical system (MEMS) processing technology, and in particular relates to a 3D-MEMS probe and a preparation method thereof. Background Art

[0002] In recent years, MEMS (micro-electromechanical system) processing technology has developed rapidly and has been widely used in the field of probe preparation. At present, related fields generally use MEMS processing technology to make related 2D probe products, but the preparation of 3D probes is relatively rare due to its complex preparation process and high cost.

[0003] CN 113562686A discloses a method for manufacturing a 3D-MEMS probe, which comprises the following steps: S1: cleaning a substrate; S2: photolithography and wet etching to obtain a needle tip pattern; S3: sputtering a seed layer on the substrate; S4: growing a high-strength metal on the seed layer using electroplating technology; S5: obtaining a needle tip structure using lapping; S6: photolithography, electroplating, and stripping on the needle tip structure to manufacture a cantilever beam structure; S7: connecting a cylinder to the cantilever beam structure using reflow soldering technology; S8: fixing and connecting a ceramic substrate using reflow soldering technology; S9: removing the seed layer using a wet method, stripping the 3D structure probe from the substrate, and then collecting and cleaning it.

[0004] In summary, providing a probe preparation method that has a simple preparation process, is easy to process and mass produce, and can accurately control the thickness of the probe is one of the problems that need to be solved urgently in this field. Summary of the invention

[0005] In view of the deficiencies of the prior art, an object of the present invention is to provide a 3D-MEMS probe and a method for preparing the same, so as to solve the problems of complex process and high cost in preparing the 3D-MEMS probe in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a 3D-MEMS probe, the 3D-MEMS probe comprising a ceramic substrate, a cylinder, a cantilever beam structure and a needle tip;

[0008] The needle tip is fixedly connected to the cylinder via a cantilever beam structure, and the cylinder is fixedly connected to the ceramic substrate.

[0009] As a preferred technical solution of the present invention, welding points are arranged between the cantilever beam and the cylinder, and between the cylinder and the ceramic substrate.

[0010] Preferably, a seed layer is provided on the top of the needle tip.

[0011] The 3D-MEMS probe provided by the present invention has a simple structure and good reliability. The needle tip is used to contact the pad of the sample to transmit the signal; the solder joint (i.e., reflow soldering technology) connects the needle tip, beam structure, cylinder and ceramic substrate to form a stable whole. When detecting, the surface morphology or vibration characteristics of the beam change, and these changes are detected and converted into electrical signals for output.

[0012] As a preferred technical solution of the present invention, the material of the needle tip includes palladium-cobalt alloy.

[0013] Preferably, the thickness of the needle tip is 10-20 μm, for example, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0014] The needle tip described in the present invention is a pad that contacts the sample and is used to transmit signals. If the thickness is too large, it will cause indentation, thereby causing chip damage, and if it is too small, the transmitted signal will become weak.

[0015] Preferably, the thickness of the seed layer is 10 to 200 nm, for example, 10 nm, 50 nm, 80 nm, 120 nm, 150 nm, 170 nm or 200 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] The present invention uses metal copper as the seed layer, which has the advantages of being easy, simple, cheap to prepare and having a mature and stable process.

[0017] As a preferred technical solution of the present invention, the material of the cantilever beam structure includes any one of palladium, cobalt or palladium-cobalt alloy or a combination of at least two of them. Typical but non-limiting combinations include: a combination of palladium and cobalt, a combination of palladium and palladium-cobalt alloy, a combination of cobalt and palladium-cobalt alloy, or a combination of palladium, cobalt and palladium-cobalt alloy.

[0018] Preferably, the material of the cylinder includes copper.

[0019] Preferably, the height of the cylinder is 8-12 mm, for example, 8 mm, 9 mm, 10 mm, 11 mm or 12 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the diameter of the cylinder is 50 μm-1 mm, for example, 50 μm, 100 μm, 500 μm, 800 μm or 1 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] The function of the cylinder of the present invention is to provide support for the 3D-MEMS probe in the vertical direction.

[0022] In a second aspect, the present invention provides a method for preparing the 3D-MEMS probe provided in the first aspect, the preparation method comprising the following steps:

[0023] (1) performing photolithography and wet etching on the substrate to obtain a needle tip structure blank; and then sputtering a seed layer on the surface of the substrate;

[0024] (2) Using electroplating technology to grow high-strength metal on the seed layer, and then using lapping to obtain the needle tip structure;

[0025] (3) performing photolithography, electroplating and stripping on the needle tip structure obtained in step (2) in sequence to manufacture a cantilever beam structure;

[0026] (4) welding a cylinder onto the cantilever beam structure and then fixing and connecting the ceramic substrate;

[0027] (5) The seed layer is removed by a wet method, and the 3D structure probe is peeled off from the substrate, and then collected and cleaned to obtain the 3D-MEMS probe.

[0028] The preparation method provided by the present invention effectively combines MEMS processing technology with photolithography, grinding, wet etching and other technologies to produce 3D-MEMS probes. The preparation process is simple and easy to process and mass produce.

[0029] As a preferred technical solution of the present invention, the substrate includes a silicon wafer or ceramics.

[0030] Preferably, step (1) also includes a cleaning process of the substrate before photolithography.

[0031] Preferably, the photolithography in step (1) includes sequentially performing coating, pre-baking, exposure, intermediate baking, development and post-baking.

[0032] Preferably, the deposition time is 20 to 40 minutes, for example, 20 minutes, 24 minutes, 28 minutes, 32 minutes, 36 minutes or 40 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the photoresist used in the photoresist coating includes 40XT glue.

[0034] Preferably, the rotation speed in the glue homogenization is 2500-3500 r / min, for example, it can be 2500 r / min, 2700 r / min, 2900 r / min, 3100 r / min, 3300 r / min or 3500 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the pre-baking temperature is 120-130° C., for example, it can be 120° C., 122° C., 124° C., 126° C., 128° C. or 130° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the pre-baking time is 8-12 min, for example, it can be 8 min, 9 min, 10 min, 11 min or 12 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0036] Preferably, the temperature of the intermediate baking is 100-110° C., for example, it can be 100° C., 102° C., 104° C., 106° C., 108° C. or 110° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the time is 1-2 min, for example, it can be 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min or 2 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0037] Preferably, the post-baking temperature is 60-100° C., for example, it can be 60° C., 70° C., 80° C., 90° C. or 100° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; the time is 20-40 min, for example, it can be 20 min, 25 min, 30 min, 35 min or 40 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0038] As a preferred technical solution of the present invention, the wet etching in step (1) includes: etching the substrate with alkaline solution and then performing oxidation and sharpening.

[0039] Preferably, the concentration of the alkali solution is 30-50wt%, for example, 30wt%, 34wt%, 38wt%, 42wt%, 46wt% or 50wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the corrosion time is 2.5 to 3.5 hours, for example, 2.5 hours, 2.7 hours, 2.9 hours, 3.1 hours, 3.3 hours or 3.5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the temperature of the oxidation sharpening is 950-1000°C, for example, 950°C, 960°C, 970°C, 980°C, 990°C or 1000°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the sputtering power in step (1) is 450-550 W, for example, 450 W, 470 W, 490 W, 510 W, 530 W or 550 W, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the sputtering speed in step (1) is 180 to 230 nm / min, for example, 180 nm / min, 190 nm / min, 200 nm / min, 210 nm / min, 220 nm / min or 230 nm / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] The present invention sets a seed layer on a substrate prepared with a needle tip structure through a sputtering process. Although a sputtering speed that is too fast can make the film grains refined and dense, too many nuclei are formed and the energy of the nuclei is too much, which will lead to excessive internal stress of the film and increase the number of defects. The substrate temperature rises, destroys the film layer structure, reduces the density and uniformity of the film layer, and too fast a deposition rate will make the internal stress of the metallized film layer too large, which will reduce the bonding force. If the sputtering speed is too slow, it will cause the atoms to migrate on the substrate for a long time, and they are easily captured by other substances before reaching the adsorption point, thereby forming larger grains, which will make the film surface rough and not dense. In addition, after the adsorbed atoms reach the substrate, the subsequent atoms will not arrive for a long time, and the exposed atoms are likely to adsorb residual gas molecules or other impurities.

[0045] The specific process of sputtering of the present invention includes: (1) starting the magnetron laser coating machine, placing the substrate after photolithography into the device, and feeding the film; (2) sputtering and deposition; (3) taking the film, ending the coating, and closing the device.

[0046] The specific process of electroplating described in the present invention includes: feeding the wafer to be electroplated → entering the plating (entering the fixture) → water washing → acid immersion (sulfuric acid) → electroplating metal (setting current and time) → water washing → taking the board out → deplating (exiting the fixture) → water washing → testing (using a step meter to test the thickness of the electroplated metal and using a laser confocal microscope to test the morphological characteristics).

[0047] Preferably, the high-strength metal in step (2) comprises palladium-cobalt alloy.

[0048] Preferably, step (2) further includes a process of stripping off excess metal after the growth.

[0049] The purpose of growing high-strength metal in step (2) is to fill the needle tip structure obtained in step (1) with high-strength metal (ie, to make the needle tip material high-strength metal). The purpose of the excess metal stripping process in the present invention is to remove excess high-strength metal from the substrate surface.

[0050] After the photolithography and electroplating in step (3) of the present invention, a layer of beam structure material is provided on the substrate surface. In order to ensure the integrity of the product structure, it is necessary to peel off the excess metal on the photoresist around the beam structure to obtain a beam structure that does not affect the normal use of the probe.

[0051] Preferably, the chemical reagent used in the stripping in step (3) includes alcohol and / or acetone.

[0052] As a preferred technical solution of the present invention, the welding method in step (4) includes reflow soldering.

[0053] The specific steps of the reflow soldering of the present invention include: pre-coating of solder paste → automatic mounting by machine → reflow soldering → inspection and electrical testing.

[0054] Preferably, the fixed connection method in step (4) includes reflow soldering.

[0055] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0056] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0057] (a) cleaning the substrate;

[0058] (b) using photolithography and wet etching to obtain a needle tip structure blank;

[0059] The photolithography includes: cleaning the silicon wafer, then using photoresist 40XT for coating at a speed of 2500-3500 r / min, and then performing pre-baking on a heating table at 120-130°C for 8-12 minutes to remove the solvent in the photoresist; then exposing on a SUSS MA8 double-sided contact photolithography machine, using a corresponding pattern mask; then performing intermediate baking on a heating table at 100-110°C for 1-2 minutes; using the exposed area of ​​the positive photoresist to react with the developer to be dissolved and form a pattern; and finally performing post-baking in an oven at 60-100°C for 20-40 minutes;

[0060] The wet etching comprises: using an alkali solution with a concentration of 30-50wt% to etch the silicon wafer for 2.5-3.5h, and then oxidizing and sharpening it at 950-1000°C;

[0061] (c) sputtering copper metal as a seed layer on the surface of the silicon wafer; the sputtering power is 450 to 550 W and the speed is 180 to 230 nm / min;

[0062] (d) growing a palladium-cobalt alloy on the seed layer;

[0063] (e) obtaining a needle tip structure by lapping;

[0064] (f) fabricating a cantilever beam structure by photolithography, electroplating, and lift-off on the needle tip structure;

[0065] (g) Connecting the cylinder to the cantilever beam structure using reflow soldering technology;

[0066] (h) using reflow soldering technology to fix and connect the ceramic substrate;

[0067] (i) The seed layer is removed by a wet method, and the 3D structure probe is peeled off from the substrate, and then collected and cleaned to obtain the 3D-MEMS probe.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) The present invention effectively combines MEMS processing technology, electroplating, grinding technology, reflow soldering, wet etching and other technologies. The technology is simple, and the combination of electroplating and grinding technology can accurately control the thickness of the probe;

[0070] (2) The reflow soldering technology used in the present invention does not require the printed circuit board to be immersed in molten solder, but instead uses local heating to complete the soldering task; therefore, the soldered components are less subject to thermal shock and will not be damaged by overheating;

[0071] (3) The reflow soldering technology used in the present invention only requires the application of solder on the soldering site and local heating to complete the soldering, thereby avoiding soldering defects such as bridging;

[0072] (4) In the reflow soldering technology adopted by the present invention, the solder is only used once and there is no situation of reuse, so the solder is very clean and free of impurities, thus ensuring the quality of the solder joints;

[0073] (5) The 3D-MEMS probe provided by the present invention has a simple structure and good reliability; and the preparation process is simple and easy to process and mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a schematic diagram of the structure of the 3D-MEMS probe provided in Example 1 of the present invention; wherein 1 is the needle tip, 2 is the cantilever beam structure, 3 is the cylinder, 4 is the welding point, and 5 is the ceramic substrate.

[0075] Figure 2 It is a flow chart of the method for preparing a 3D-MEMS probe provided by the present invention. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] Example 1

[0078] This embodiment provides a Figure 1 The 3D-MEMS probe shown includes a ceramic substrate 5, a solder joint 4, a cylinder 3, a cantilever beam 2, and a needle tip 1;

[0079] The needle tip 1 is fixedly connected to the cylinder 3 through the beam structure 2 and the welding point 4, and the cylinder 3 is fixedly connected to the ceramic substrate 5; a welding point 4 is provided between the cylinder 3 and the ceramic substrate 5. The material of the needle tip includes palladium-cobalt alloy; the thickness of the needle tip is 15 μm.

[0080] The material of the beam structure includes cobalt-palladium alloy; the material of the cylinder is copper; the height of the cylinder is 10 mm; and the diameter of the cylinder is 500 μm.

[0081] The preparation method of the 3D-MEMS probe is as follows Figure 2 The steps shown include:

[0082] (a) cleaning the substrate;

[0083] (b) using photolithography and wet etching to obtain a needle tip structure blank;

[0084] The photolithography includes: cleaning the silicon wafer, then using photoresist 40XT for coating at a speed of 3000r / min, and then performing pre-baking on a heating table at 125°C for 10 minutes to remove the solvent in the photoresist; then performing exposure on a SUSS MA8 double-sided contact photolithography machine, using a corresponding pattern mask; then performing intermediate baking on a heating table at 105°C for 1.5 minutes; using the exposed area of ​​the positive photoresist to react with the developer to be dissolved and form a pattern; and finally performing post-baking in an oven at 80°C for 30 minutes;

[0085] The wet etching method includes: etching the silicon wafer with an alkali solution having a concentration of 40wt% for 3h, and then oxidizing and sharpening the silicon wafer at 980°C;

[0086] (c) sputtering copper metal as a seed layer on the surface of the silicon wafer; the sputtering power is 500 W and the speed is 200 nm / min;

[0087] (d) growing a palladium-cobalt alloy on the seed layer;

[0088] (e) obtaining a needle tip structure by lapping;

[0089] (f) fabricating a cantilever beam structure by photolithography, electroplating, and lift-off on the needle tip structure;

[0090] (g) Connecting the cylinder to the cantilever beam structure using reflow soldering technology;

[0091] (h) using reflow soldering technology to fix and connect the ceramic substrate;

[0092] (i) The seed layer is removed by a wet method, and the 3D structure probe is peeled off from the substrate, and then collected and cleaned to obtain the 3D-MEMS probe.

[0093] Example 2

[0094] This embodiment provides a 3D-MEMS probe, which is different from the embodiment 1 only in that:

[0095] In this embodiment, the thickness of the needle tip is changed to 10 μm.

[0096] The preparation method of the 3D-MEMS probe is the same as that of Example 1.

[0097] Example 3

[0098] This embodiment provides a 3D-MEMS probe, which is different from the embodiment 1 only in that:

[0099] In this embodiment, the thickness of the needle tip is changed to 5 μm.

[0100] The preparation method of the 3D-MEMS probe is the same as that of Example 1.

[0101] Example 4

[0102] This embodiment provides a 3D-MEMS probe, which is different from the embodiment 1 only in that:

[0103] In this embodiment, the thickness of the needle tip is changed to 25 μm.

[0104] The preparation method of the 3D-MEMS probe is the same as that of Example 1.

[0105] Example 5

[0106] This embodiment provides a 3D-MEMS probe, and the 3D-MEMS probe is the same as that in Embodiment 1.

[0107] The only difference between the method for preparing the 3D-MEMS probe and Example 1 is that in this example, the reflow soldering described in step (g) and step (h) is changed to spot soldering.

[0108] Example 6

[0109] This embodiment provides a 3D-MEMS probe, and the 3D-MEMS probe is the same as that in Embodiment 1.

[0110] The only difference between the method for preparing the 3D-MEMS probe and Example 1 is that in this example, the sputtering power in step (c) is changed to 400W.

[0111] Example 7

[0112] This embodiment provides a 3D-MEMS probe, and the 3D-MEMS probe is the same as that in Embodiment 1.

[0113] The only difference between the method for preparing the 3D-MEMS probe and Example 1 is that in this example, the sputtering power in step (c) is changed to 600W.

[0114] The present invention also uses the 3D-MEMS probes provided in Examples 1-7 to detect wafers of visual recognition chips, flash memory chips, random dynamic storage chips, and the like.

[0115] In summary, the 3D-MEMS probe provided by the present invention has a simple structure and good reliability; and its preparation process is simple and easy to process and mass produce.

[0116] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0117] The applicant declares that the present invention illustrates the detailed process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a 3D-MEMS probe, characterized in that: The preparation method comprises the following steps: (1) Photolithography and wet etching are performed on the substrate to obtain a needle tip structure blank; then a seed layer is sputtered on the surface of the substrate; The substrate comprises a silicon wafer; The wet etching method includes: etching the substrate with an alkaline solution and then oxidizing and sharpening it; The temperature of the oxidation sharpening is 950-1000°C; (2) Using electroplating technology to grow high-strength metal on the seed layer, and then using grinding to obtain the needle tip structure; (3) performing photolithography, electroplating and stripping on the needle tip structure obtained in step (2) in sequence to manufacture a cantilever beam structure; (4) Welding a cylinder onto the cantilever beam structure and then fixing and connecting the ceramic substrate; (5) removing the seed layer by a wet method, peeling off the 3D structure probe from the substrate, collecting and cleaning it, and obtaining the 3D-MEMS probe; The 3D-MEMS probe includes a ceramic substrate, a cylinder, a cantilever beam structure and a needle tip; The needle tip is fixedly connected to the cylinder via a cantilever beam structure, and the cylinder is fixedly connected to the ceramic substrate.

2. The preparation method according to claim 1, characterized in that: A welding point is arranged between the cylinder and the ceramic substrate.

3. The preparation method according to claim 1, characterized in that: A seed layer is arranged on the top of the needle tip.

4. The preparation method according to claim 1, characterized in that: The needle tip is made of palladium-cobalt alloy.

5. The preparation method according to claim 1, characterized in that: The thickness of the needle tip is 10-20 μm.

6. The preparation method according to claim 1, characterized in that: The thickness of the seed layer is 10-200 nm.

7. The preparation method according to claim 1, characterized in that: The material of the cantilever beam structure includes any one of palladium, cobalt or palladium-cobalt alloy or a combination of at least two of them.

8. The preparation method according to claim 1, characterized in that: The material of the cylinder includes copper.

9. The preparation method according to claim 1, characterized in that: The height of the cylinder is 8-12 mm.

10. The preparation method according to claim 1, characterized in that: The diameter of the cylinder is 50 μm-1 mm.

11. The preparation method according to claim 1, characterized in that: Step (1) also includes a substrate cleaning process before photolithography.

12. The preparation method according to claim 1, characterized in that: The photolithography in step (1) includes sequentially performing coating, pre-baking, exposure, intermediate baking, development and post-baking.

13. The preparation method according to claim 12, characterized in that: The photoresist used in the photoresist coating includes 40XT glue.

14. The preparation method according to claim 12, characterized in that: The rotation speed during the coating is 2500-3500 r / min.

15. The preparation method according to claim 12, characterized in that: The pre-baking temperature is 120-130° C. and the time is 8-12 minutes.

16. The preparation method according to claim 12, characterized in that: The temperature of the intermediate baking is 100-110° C. and the time is 1-2 minutes.

17. The preparation method according to claim 12, characterized in that: The post-baking temperature is 60-100° C. and the time is 20-40 minutes.

18. The preparation method according to claim 1, characterized in that: The concentration of the alkali solution in step (1) is 30-50wt%.

19. The preparation method according to claim 1, characterized in that: The corrosion time is 2.5 to 3.5 hours.

20. The preparation method according to claim 1, characterized in that: The sputtering power in step (1) is 450-550W.

21. The preparation method according to claim 1, characterized in that: The sputtering speed in step (1) is 180-230 nm / min.

22. The preparation method according to claim 1, characterized in that: The high-strength metal in step (2) includes palladium-cobalt alloy.

23. The preparation method according to claim 1, characterized in that: Step (2) also includes a process of stripping off excess metal after the growth.

24. The preparation method according to claim 1, characterized in that: The chemical reagents used in the stripping in step (3) include alcohol and / or acetone.

25. The preparation method according to claim 1, characterized in that: The soldering method in step (4) includes reflow soldering.

26. The preparation method according to claim 1, characterized in that: The method of fixing the connection in step (4) includes reflow soldering.

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