A method for welding platinum-iridium alloy wire at the tail end of a cortical microelectrode

Abstract

The present invention discloses a method for welding a platinum-iridium alloy wire to the end of a cortical microelectrode. When the electromagnet power cord is not energized, the electromagnet magnetic surface has a magnetically attracted iron mold, and the cortical microelectrode is placed at a suitable distance from the front end of the iron mold. The platinum-iridium alloy wires are aligned one by one and inserted into a small hole formed by a groove of the iron mold and the surface of the adsorption electromagnet. The front end of the platinum-iridium alloy wire extending out of the groove of the iron mold automatically aligns and contacts the surface of the cortical microelectrode pad, and the extension length can be flexibly adjusted. The platinum-iridium alloy wire and the cortical microelectrode pad are welded one by one using resistance welding. After welding is completed, the electromagnet power cord is energized, the electromagnet loses its magnetism, and the iron mold is removed to remove the welded product, completing the welding of the platinum-iridium alloy wire to the cortical microelectrode pad. The present invention provides a highly reliable, low-cost, precisely controlled, and easily implemented method for studying welding between the end of a cortical microelectrode and a platinum-iridium alloy wire.

Description

Technical Field

[0001] The invention belongs to the technical field of precision machining, and in particular relates to a method for welding a platinum-iridium alloy wire at the tail end of a cortical microelectrode. Background Art

[0002] Welding multi-channel implantable microelectrodes based on platinum-iridium alloy is difficult, and efficient and accurate welding is a pressing issue. However, the extremely small size of the cortical microelectrode pads and the platinum-iridium alloy wires transmitted to the distal end place extremely high demands on the welding process of the platinum-iridium alloy wires and the cortical microelectrode pads. Furthermore, since the platinum-iridium alloy wires are prone to plastic deformation and difficult to maintain a straight, conformable shape, the welding position is difficult to determine. Therefore, ensuring efficient, precise, and controllable welding is crucial.

[0003] A search of prior art revealed that in 2022, Professor Iakov Rachinskiy of the Department of Biomedical Engineering at Duke University in Durham, North Carolina, USA, published an article titled "High-Density, Actively Multiplexed μECoG Array on Reinforced Silicone Substrate" in Frontiers in Nanotechnology, 2022, 4:5. This paper proposes fabricating all zero-insertion-force (ZIF) connectors at the ends of the electrode array on a single layer, thus protecting the metal connector pads from the overlying silicone layer. This connection method facilitates soldering, but the disadvantage of this interface method is that it uses a zero-insertion-force clip for clamping and lacks encapsulation, making it suitable for temporary, short-term use but not for long-term implantation. Furthermore, the use of reinforced, hardened silicone has yet to be verified for biocompatibility.

[0004] In 2018, Professor Klas Tybrandt of the Institute of Biomedical Engineering at ETH Zurich wrote an article titled “High-density stretchable electrode grids for chronic neural recording” in Advanced Materials, 2018, 30(15): 1706520. He proposed clamping the stretchable electrode grid on a customized connector and electroplating a thin layer of platinum on the exposed Au-TiO2NW to form an electrode. A thin layer of platinum electroplated on the exposed Au-TiO2NW can improve the electrode performance, but the clamping method is not reliable for fixing the metal and can only be used for preliminary verification in acute experiments.

[0005] In 2020, Professor Aline F. Renz of the Institute of Biomedical Engineering at the Swiss Federal Institute of Technology in Zurich published an article titled "Opto-E-Dura: a soft, stretchable ECoG array for multimodal, multiscale neuroscience" in Advanced Healthcare Materials, 2020, 9(17): 2000814. The article proposed minimizing the size and weight of the device by printing silver epoxy resin on the contacts and fixing them with epoxy glue. The implant was then mounted on a custom PCB, with the Omnetics connector soldered to the other side of the PCB. However, the biocompatibility of the silver paste material remains to be verified, and the mechanical strength is poor.

[0006] In 2020, Professor Giuseppe Schiavone of the Swiss Federal Institute of Technology in Lausanne wrote an article titled "Soft, implantable bioelectronic interfaces for translational research" in Advanced Materials, 2020, 32(17): 1906512. He proposed connecting scaled implants to bundled wires through miniaturized soft connectors. The leads are in contact with the electrical stimulation hardware through subcutaneous threads and interconnected with hard components through conductive epoxy resin and silicone adhesives. However, it is difficult to ensure that the particles in the ACF glue are pressurized and conductive by hot pressing the elastic silicone substrate.

[0007] CN 101240435 B discloses a method for electroplating self-welding three-dimensional microelectrode arrays, wherein microelectrodes are passed through metal micropores and fixed in slots; the micrometal pores are electroplated to gradually reduce the metal pores until they are bonded to the microelectrodes passing through the micrometal pores, thereby achieving self-welding of the microelectrodes and the micrometal pores. The electroplating solution used in this method easily corrodes the metal micropores and microelectrodes, and when the electroplated and welded microelectrodes and insulating plates are ultrasonically cleaned with acetone and alcohol, the acetone and alcohol have adverse effects on the microelectrodes.

[0008] CN 109534284 A discloses a method for hot-press welding microelectrodes to flexible cables. This method uses anisotropic conductive adhesive (ACF) as a pressure welding material to achieve anisotropic conduction of bumpless pads. Deep silicon etching technology is used to form grooves around the microelectrode pads, so that after hot-pressing, the microelectrode and flexible cable pads are conductive only in the normal direction of the pads. However, the ACF film itself is not conductive. Only when the ACF film is pressurized and heated does it soften (into a colloidal state), allowing the conductive particles to flow and evenly distribute. However, excessively high temperatures after heating can affect the properties of the microelectrode to be welded.

[0009] In summary, existing research lacks exploration of fixed welding between tiny wires, and the use of conductive epoxy resin and other materials to seal welds lacks physical verification. Manual welding is inefficient and time-consuming, alignment is difficult, and the weld uniformity is poor. Research on how to always keep the cortical microelectrode pad and platinum-iridium alloy wire fixed during the welding process is of great significance for efficient and precise welding. Summary of the Invention

[0010] To overcome the shortcomings of the prior art, the present invention provides a method for welding a platinum-iridium alloy wire to the end of a cortical microelectrode. When the electromagnet power cord is not energized, the magnetic surface of the electromagnet has a magnetically attracted iron mold, and the cortical microelectrode is placed at a suitable distance from the front end of the iron mold. The platinum-iridium alloy wires are aligned one by one and inserted into the small hole formed by the groove of the iron mold and the surface of the adsorption electromagnet. The front end of the platinum-iridium alloy wire extending out of the groove of the iron mold automatically aligns and contacts the surface of the cortical microelectrode pad, and the extension length can be flexibly adjusted. The platinum-iridium alloy wire and the cortical microelectrode pad are welded one by one using resistance welding. After welding is completed, the electromagnet power cord is energized, the electromagnet loses its magnetism, and the iron mold is removed to remove the welded product. The platinum-iridium alloy wire and the cortical microelectrode pad are welded. The present invention provides a highly reliable, low-cost, precisely controlled, and easy-to-implement operation method for studying the welding between the end of a cortical microelectrode and the platinum-iridium alloy wire.

[0011] The technical solution adopted by the present invention to solve the technical problem includes the following steps:

[0012] Step 1: Making a magnetic material mold, wherein the magnetic material mold is a hexahedron, one side of which is provided with a plurality of semicircular long grooves;

[0013] Step 2: The electromagnet is not energized, and the magnetic surface of the electromagnet is kept magnetic. The groove of the magnetic material mold faces the electromagnet and is adsorbed on the magnetic surface of the electromagnet. The magnetic surface of the electromagnet is part of the upper surface of the electromagnet.

[0014] Step 3: Place the cortical microelectrodes on one side of the magnetic material mold on the upper surface of the electromagnet, with each cortical microelectrode pad aligned with a groove in the magnetic material mold.

[0015] Step 4: Each platinum-iridium alloy wire is divided into a group and wound together. It is placed on the other side of the magnetic material mold on the upper surface of the electromagnet. One end of each platinum-iridium alloy wire is inserted into the groove of the magnetic material mold and extends out a part;

[0016] Step 5: Use resistance welding to weld the platinum-iridium alloy wires and the cortical microelectrode pads one by one;

[0017] Step 6: Power on the electromagnet power cord to make the magnetic surface of the electromagnet lose its magnetism, remove the magnetic material mold, and the welding is completed.

[0018] Preferably, the platinum-iridium alloy wire is a spiral wire structure and is dispersed at the end.

[0019] Preferably, a=4.

[0020] Preferably, the platinum-iridium alloy wires are wound into bundles and placed side by side in groups on the electromagnet.

[0021] Preferably, the radius of the groove of the magnetic material mold is 50 to 100 microns, and the depth of the groove is 0.3 to 1 centimeter.

[0022] Preferably, the magnetic material mold includes 16 grooves, which are divided into 4 groups. The normal angle between adjacent grooves in each group is 2 to 5 degrees, and the normal angle between the two nearest grooves in adjacent groups is 5 to 10 degrees.

[0023] Preferably, the diameter of the platinum-iridium alloy wire is 50 to 150 microns, and the length of the portion of the platinum-iridium alloy wire extending out of the groove of the magnetic material mold is 1 / 3 to 2 / 3 of the length of the cortical microelectrode pad.

[0024] Preferably, the material of the magnetic material mold is one of iron, cobalt, nickel, metal low-temperature negative thermal expansion material, and alloy low-temperature negative thermal expansion material.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The present method achieves "one-dimensional linear welding." After the platinum-iridium alloy wire penetrates the mold groove, the cortical microelectrode pad and the platinum-iridium alloy wire are both located in a one-dimensional straight line radially along the mold groove. This converts three-dimensional welding into one-dimensional linear welding, greatly improving the accuracy of the weld point position and the controllability of the welding process.

[0027] 2. When the electromagnet loses power, it is magnetic and can firmly adsorb the iron mold to ensure precise control of the platinum-iridium alloy wire on the cortical microelectrode pad during welding. After welding, the electromagnet is energized to eliminate the magnetism, and the iron mold can be easily removed, effectively ensuring the safety of the welding point.

[0028] 3. The present invention provides a highly reliable, low-cost, precisely controlled, and easily implemented operating method for studying the welding between the tail end of the cortical microelectrode and the platinum-iridium alloy wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a three-dimensional schematic diagram of the process of the present invention.

[0030] Figure 2 This is a process flow chart of the method of the present invention, (a) shows the iron mold being adsorbed onto the magnetic surface of the electromagnet, (b) shows the platinum-iridium alloy wires passing through the grooves of the iron mold one by one, (c) shows the platinum-iridium alloy wires being attached to the cortical microelectrode pads, (d) shows the platinum-iridium alloy wires being resistance welded one by one on the cortical microelectrode pads, and (e) shows the electromagnet being energized to release the iron mold.

[0031] Figure 3 This is a two-dimensional top view schematic diagram of the local welding area after welding is completed in the present invention.

[0032] Figure 4 This is a process flow chart of the magnet variant of the present invention. (a) shows the platinum-iridium alloy wire passing through the groove of the magnetic thermal expansion mold when the magnetic thermal expansion mold is not heated. (b) shows the platinum-iridium alloy wire being clamped by the groove of the magnetic thermal expansion mold after the magnetic thermal expansion mold is heated.

[0033] Figure 5 This is a schematic diagram of the water-soluble tape fixation of Example 3 of the present invention, (a) is a three-dimensional explosion diagram after the platinum-iridium alloy wire is fixed with the water-soluble tape, (b) is a three-dimensional diagram after the platinum-iridium alloy wire is fixed with the water-soluble tape, and (c) is a two-dimensional cross-sectional schematic diagram after the platinum-iridium alloy wire is fixed with the water-soluble tape.

[0034] In the figure: 1-cortical microelectrode tail end, 2-cortical microelectrode platinum-iridium alloy wire, 3-cortical microelectrode pad, 4-iron mold, 5-platinum-iridium alloy wire, 6-electromagnetic surface, 7-electromagnet power cord, 8-electromagnet, 9-electromagnet housing, 10-electromagnet resin glue, 11-iron mold groove, 12-resistance welding, 13-pad, 14-magnetic thermal expansion mold, 15-upper water-soluble tape, 16-lower water-soluble tape. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and examples.

[0036] In response to the defects and gaps in the existing technology, the present invention provides a platinum-iridium alloy wire welding process for the tail end of a cortical microelectrode, which can effectively improve the relative position accuracy of the platinum-iridium alloy wire during welding, while ensuring that the platinum-iridium alloy wire maintains a flat straight shape during welding. In the first step, when the electromagnet power cord is not energized, the magnetic surface of the electromagnet has a magnetic adsorption iron mold, and the cortical microelectrode is placed at a suitable distance from the front end of the iron mold; in the second step, the platinum-iridium alloy wires are aligned one by one and inserted into the small hole formed by the groove of the iron mold and the surface of the adsorption electromagnet. The front end of the platinum-iridium alloy wire extending out of the groove of the iron mold automatically aligns and contacts the surface of the cortical microelectrode pad, and the extension length can be flexibly adjusted; in the third step, the platinum-iridium alloy wire and the cortical microelectrode pad are welded one by one using resistance welding; in the fourth step, after welding is completed, the electromagnet power cord is energized, the electromagnet loses its magnetism, the iron mold is removed, and the welded product can be taken out, and the platinum-iridium alloy wire and the cortical microelectrode pad are welded. The present invention solves the following three problems: (1) manually aligning the platinum-iridium alloy wires one by one to the corresponding cortical microelectrode pads for resistance welding is time-consuming and laborious; (2) the relative position control uniformity of the cortical microelectrode pads is poor; and (3) the platinum-iridium alloy wire is prone to plastic deformation and is difficult to maintain a smooth straight shape. The present invention can effectively ensure efficient, accurate and stable welding between the tail end of the cortical microelectrode and the platinum-iridium alloy wire.

[0037] The technical solution adopted by the present invention to solve the technical problem includes the following steps:

[0038] Step 1: The electromagnet is not energized, the magnetic surface of the electromagnet is kept magnetic, the groove of the iron mold faces the electromagnet and is adsorbed on the magnetic surface of the electromagnet.

[0039] Step 2: Place the cortical microelectrode on the upper surface of the electromagnet, and align the cortical microelectrode pad with the groove of the iron mold.

[0040] Step 3: Wrap the platinum-iridium alloy wires together in groups of four and place them on the upper surface of the electromagnet. Insert one end of the platinum-iridium alloy wire into the groove of the iron mold and extend a part of it.

[0041] Step 4: Resistance welding is used to weld the platinum-iridium alloy wires and the cortical microelectrode pads one by one.

[0042] Step 5: Power on the electromagnet power cord to make the magnetic surface of the electromagnet lose its magnetism, remove the iron mold, and the welding is completed.

[0043] Preferably, the welding process is used to achieve connection between the cortical microelectrode and an external wire such as a platinum-iridium alloy wire.

[0044] Preferably, the platinum-iridium alloy wire is a spiral wire structure and is dispersed at the end.

[0045] Preferably, the platinum-iridium alloy wires are wound into bundles and placed side by side in groups on the electromagnet.

[0046] Preferably, the radius of the iron mold groove is 50 to 100 microns, and the depth of the iron mold groove is 0.3 to 1 centimeter.

[0047] Preferably, the 16 grooves of the iron mold are divided into 4 groups, the normal angle between adjacent grooves in each group is 2 to 5 degrees, and the normal angle between the two nearest grooves in adjacent groups is 5 to 10 degrees.

[0048] Preferably, the diameter of the platinum-iridium alloy wire is 50 to 150 microns, and the platinum-iridium alloy wire can be moved back and forth in the groove of the iron mold to flexibly adjust the protruding length.

[0049] Preferably, the length of the portion of the platinum-iridium alloy wire extending out of the groove of the iron mold is 1 / 3 to 2 / 3 of the length of the cortical microelectrode pad.

[0050] Preferably, the mold material adsorbed on the magnetic surface of the electromagnet can be ferromagnetic materials such as iron, cobalt, and nickel.

[0051] Preferably, the mold material may also be a magnetic thermal expansion material, such as a metal low-temperature negative thermal expansion material, an alloy low-temperature negative thermal expansion material, and the like. Specific embodiment 1:

[0053] Figure 1 This is a three-dimensional schematic diagram of the core process of welding the platinum-iridium alloy wire at the tail end of a cortical microelectrode. The platinum-iridium alloy wire 5 passing through the iron mold groove 11 and the cortical microelectrode pad 3 are welded together using resistance welding 12. The electromagnet power line 7 is energized and demagnetized and then removed.

[0054] Figure 2 A specific implementation method of the platinum-iridium alloy wire welding process for the tail end of the cortical microelectrode is provided. The preferred welding method can adopt the following steps:

[0055] S1: If Figure 2 As shown in (a), the iron mold 4 is adsorbed onto the electromagnet magnetic surface 6, and the lower surface of the iron mold 4 overlaps with the electromagnet magnetic surface 6.

[0056] S2: If Figure 2 As shown in (b), the platinum-iridium alloy wire 5 is inserted into the groove 11 of the iron mold, and the length of the part extending out of the groove 11 of the iron mold is 1 / 3 to 2 / 3 of the length of the cortical microelectrode pad 3.

[0057] S3: If Figure 2 As shown in (c), the cortical microelectrode tail end 1 is placed on the upper surface of the pad 13, and the platinum-iridium alloy wire 5 is attached to the cortical microelectrode pad 3.

[0058] S4: As Figure 2 As shown in (d), the platinum-iridium alloy wires 5 are welded one by one by resistance welding 12.

[0059] S5: If Figure 2 As shown in (e), after the electromagnet 8 is energized, the electromagnet magnetic surface 6 loses its magnetism, the iron mold 4 is separated, and the finished product after welding is taken out.

[0060] Figure 3 The two-dimensional top view of the finished product after welding is completed. The platinum-iridium alloy wire 5 is fixed by the iron mold 4 and arranged neatly to facilitate welding. Specific embodiment 2:

[0062] like Figure 4 As shown, compared with Example 1, Figure 4 (a) The material of the iron mold 4 is replaced by a magnetic thermal expansion material. The material structure of the thermal expansion material is mainly composed of relatively stable metal atoms, and the thermal expansion coefficient is lower than that of other materials, and it has a lower volume change rate. Thermal expansion is mainly divided into two types: positive thermal expansion (thermal expansion and cold contraction) and negative thermal expansion (thermal contraction and cold expansion). The magnetic thermal expansion materials on the market are mainly negative thermal expansion materials, mainly including metal low-temperature negative thermal expansion materials and alloy low-temperature negative thermal expansion materials, such as Mn3AX materials and CrTe with magnetic negative expansion properties. 1-x Se x Materials, R2Fe 17-x M x Cy Materials, R 1-x A x MnO3 materials, Gd5Sn4 materials, R2Fe 14 Material B, Gd3(FeTi) 29 Materials, TbPdIn (DyNiAl, GdNiAl) materials, Gd5 (Si, Ge) 4 materials and GdAl2 materials, etc.

[0063] When the iron mold 4 is made of CrTe 1-x Se x When the material is made, the unit cell volume of CrTe material increases with decreasing temperature, and with increasing Se content, 1-x Se x (0≤x≤0.15) The negative expansion effect parameter of the material is -28.8ppmK -1 (x=0,280-340K),-20.4ppmK -1 (x=0.05,240-320K), -15.6ppmK -1 (x=0.1,200-295K),-8.5ppmK -1 (x=0.15, 170-270K), the lower the temperature, the tighter the platinum-iridium alloy wire 5 is wrapped by the iron mold groove 11, and the better the fixing effect.

[0064] Figure 4 (a) The iron mold 4 is made of a magnetic material such as iron, cobalt, or nickel. When the platinum-iridium alloy wire 5 is inserted into the iron mold groove 11, there is a certain gap between the platinum-iridium alloy wire 5 and the iron mold groove 11. The platinum-iridium alloy wire 5 is not completely fixed and can be stretched forward and backward in the iron mold groove 11 to flexibly adjust the extended length. Figure 4 (b) The mold is a magnetic thermal expansion mold 14, which can expand when heated and self-hold each platinum-iridium alloy wire 5 to prevent the platinum-iridium alloy wire 5 from moving during welding. Specific embodiment 3:

[0066] like Figure 5 As shown, compared with Example 1, Figure 5 (a) shows the use of an upper layer of water-soluble tape 15 and a lower layer of water-soluble tape 16 to fix the platinum-iridium alloy wire 5, thereby welding the platinum-iridium alloy wire 5 to the cortical microelectrode pad 3. The specific steps are as follows:

[0067] Step 1: Stick the lower surface of the double-sided adhesive water-soluble tape 16 (such as TESA61914, TESA4972, etc.) to the surface of the iron mold groove 11.

[0068] Step 2: Paste the platinum-iridium alloy wires 5 one by one onto the upper surface of the lower water-soluble tape 16 and align them with the grooves of the iron mold grooves 11 .

[0069] Step 3: Place the sticky surface of the single-sided sticky upper water-soluble tape 15 (such as AQUASOL ASWT-2) on top of the platinum-iridium alloy wires 5 one by one, and contact and bond with the upper surface of the lower water-soluble tape 16.

[0070] Step 4: Use resistance welding 12 to weld the platinum-iridium alloy wire 5 to the cortical microelectrode pad 3.

[0071] Step 5: After welding is completed, rinse with 50-80 degrees Celsius hot water to accelerate the dissolution of the upper water-soluble tape 15 and the lower water-soluble tape 16. After the upper and lower water-soluble tapes are completely dissolved, take out the welded product.

[0072] Figure 5 (b) is a three-dimensional spatial display of the finished welding product when welding is completed.

[0073] Figure 5 (c) is a two-dimensional display diagram of the welding cross-section. The lower layer of water-soluble tape 16 is attached to the upper surface of the iron mold 4, and the platinum-iridium alloy wire 5 is attached to the upper surface of the lower layer of water-soluble tape 16. The lower surface of the upper layer of water-soluble tape 15 is fixed to the platinum-iridium alloy wire 5 one by one by sticking to the platinum-iridium alloy wire 5 and the upper surface of the lower layer of water-soluble tape 16.

[0074] This process uses a purely physical method to secure the platinum-iridium alloy wires 5, disregarding the magnetic properties of the iron mold 4 and electromagnet 8. The iron mold 4 can be replaced with molds made of other materials, significantly increasing the selectivity of mold materials. Removing conventional insoluble tape after welding is a challenging task, as manual removal can easily alter the relative spacing between the platinum-iridium alloy wires 5. However, water-soluble tape can be removed by flushing with hot water after welding, ensuring consistent spacing between the platinum-iridium alloy wires 5 and making it easier to remove the finished weld.

[0075] The platinum-iridium alloy wire welding process for the cortical microelectrode tail end of the present invention can be extended to be applied to welding of tiny fine wires of other different materials, such as copper wire, aluminum wire, silver wire, gold wire, etc., making multi-channel welding more convenient.

Claims

1. A method for welding platinum-iridium alloy wire at the end of a cortical microelectrode, characterized in that: The following steps are involved: Step 1: Prepare a magnetic material mold. The magnetic material mold is a hexahedron, one side of which is provided with multiple semicircular long grooves. The radius of the grooves in the magnetic material mold is 50-100 microns, and the depth of the grooves is 0.3-1 centimeter. The magnetic material mold includes 16 grooves, which are divided into 4 groups. The angle between the normal lines of adjacent grooves in each group is 2-5 degrees, and the angle between the normal lines of the two nearest grooves in adjacent groups is 5-10 degrees. The material of the magnetic material mold is one of iron, cobalt, nickel, metal low-temperature negative thermal expansion material, and alloy low-temperature negative thermal expansion material. Step 2: The electromagnet is not energized, and the magnetic surface of the electromagnet is kept magnetic. The groove of the magnetic material mold faces the electromagnet and is adsorbed on the magnetic surface of the electromagnet. The magnetic surface of the electromagnet is part of the upper surface of the electromagnet. Step 3: Place the cortical microelectrodes on the side of the magnetic material mold on the upper surface of the electromagnet, with each cortical microelectrode pad aligned with a groove in the magnetic material mold; Step 4: Platinum-iridium alloy wires are wound together in groups and placed on the other side of the magnetic material mold on the upper surface of the electromagnet, with one end of each platinum-iridium alloy wire inserted into the groove of the magnetic material mold and partially extending out. The platinum-iridium alloy wires are spiral wires and dispersed at the ends. The platinum-iridium alloy wires are wound into bundles and placed side by side in groups on the electromagnet. The diameter of the platinum-iridium alloy wires is 50 to 150 microns, and the length of the platinum-iridium alloy wires extending out of the groove of the magnetic material mold is 1 / 3 to 2 / 3 of the length of the cortical microelectrode pad. Step 5: Use resistance welding to weld the platinum-iridium alloy wires and the cortical microelectrode pads one by one; Step 6: Power on the electromagnet power cord to make the magnetic surface of the electromagnet lose its magnetism, remove the magnetic material mold, and the welding is completed.

2. The method for welding a platinum-iridium alloy wire at the tail end of a cortical microelectrode according to claim 1, characterized in that: Said a=4.

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