Electric connector used in high-voltage environment box and brazing method

Abstract

The invention discloses an electric connector used in a high-voltage environment box and a brazing method. Comprising a vertical cylindrical stainless steel outer shell, a T-shaped stainless steel inner shell which extends into the stainless steel outer shell and is detachably connected with the upper part of the stainless steel outer shell, a silicon nitride ceramic circular plate, M vertically extending copper core wires and a copper core wire sleeve arranged at the upper parts of the copper core wires, wherein M is greater than or equal to 3; the upper ends and the lower ends of the stainless steel inner shell and the stainless steel outer shell are open, a stainless steel annular supporting frame is arranged in the middle of the inner side face of the stainless steel outer shell, and the silicon nitride ceramic circular plate is located on the stainless steel annular supporting frame. The electric connector has the advantages of being good in sealing performance and long in service life.

Description

Technical Field

[0001] The invention relates to the technical field of signal transmission connection, and in particular to an electric connector used in a high-voltage environment box and a brazing method. Background Art

[0002] As modern industry continues to increase its requirements for the performance of materials and components, the application of high-pressure gas environment fatigue test tensile machines has become increasingly critical. The above equipment is mainly used to simulate the fatigue performance of materials or components under high-pressure gas environments and tensile stress, and to evaluate their reliability and service life under complex working conditions.

[0003] The electrical connectors in the prior art are prone to deformation and cracking under high pressure, which can lead to problems such as sealing failure, signal instability, gas leakage, etc., hindering the performance research of materials and components, causing frequent equipment failures and test interruptions, resulting in high maintenance costs and waste of test materials. Summary of the invention

[0004] The purpose of the invention is to overcome the shortcomings of deterioration of the sealing performance of the electrical connector and easy failure of the welding parts under high-pressure environment, resulting in frequent interruption of signal transmission, and to provide an electrical connector and a brazing method for use in a high-pressure environment box.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An electrical connector for a high-voltage environment box, comprising a stainless steel outer shell in the shape of a vertical cylinder, a T-shaped stainless steel inner shell extending into the stainless steel outer shell and detachably connected to the upper part of the stainless steel outer shell, a silicon nitride ceramic circular plate, M vertically extending copper core wires and a copper core wire sleeve arranged on the upper part of the copper core wire, M ≥ 3; the upper and lower ends of the stainless steel inner shell and the stainless steel outer shell are both open, a stainless steel annular support frame is provided in the middle of the inner side surface of the stainless steel outer shell, and the silicon nitride ceramic circular plate is located on the stainless steel annular support frame; M through holes are provided on the silicon nitride ceramic circular plate, an annular groove for accommodating solder is provided on the upper part of the through hole, the copper core wire passes downward through the corresponding through hole and is brazed to the corresponding through hole; a notch for accommodating solder is provided on the upper part of the outer side surface of the silicon nitride ceramic circular plate, a gap is provided between the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate, and the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate are brazed to be connected.

[0007] The copper core wire casing is used to provide electrical insulation protection for the copper core wire to prevent leakage and short circuit caused by the crossing of the copper core wire current. The depth of the annular groove is generally set to 1.5mm, which can increase the welding area between the copper core wire and the silicon nitride ceramic disc, and at the same time increase the accumulation of solder. The plasticity of the solder can be used to reduce the stress here, so that the silicon nitride ceramic disc and the copper core wire are sealed and connected.

[0008] The silicon nitride ceramic circular plate used in the present invention plays a good insulating role, so that the electric connector will not have a cross-current phenomenon when transmitting signals.

[0009] The setting of the gap can reduce the risk of cracking caused by thermal expansion of the stainless steel outer shell and the stainless steel annular support frame and extrusion of the silicon nitride ceramic circular plate, and effectively reduce the welding internal stress caused by brazing the silicon nitride ceramic circular plate and the stainless steel annular support frame; and can be used to store excess solder, and the plasticity of the solder can relieve part of the stress, effectively improving the sealing performance of the connector in extreme environments, ensuring the stability of the welding part, preventing the gas in the high-pressure environment box from leaking out through the electrical connector, significantly reducing the interruption of signal transmission, and increasing the service life of the connector.

[0010] Preferably, a mica ring gasket is provided in the middle of the copper core wire, and an annular groove for accommodating the mica ring gasket is provided at the edge of the upper surface of the silicon nitride ceramic circular plate.

[0011] Preferably, an annular plate of stainless steel material is provided at the lower end of the stainless steel inner shell, a step hole is provided in the middle of the annular plate, and a silicon nitride ceramic sealing plate is provided on the step hole; M sealing holes are provided in the middle of the silicon nitride ceramic sealing plate, and an annular pit for accommodating solder is provided on the sealing hole, and the lower part of the copper core wire passes through the corresponding sealing hole and is brazed to the sealing hole; a gap is provided between the outer side surface of the silicon nitride ceramic sealing plate and the upper part of the inner side surface of the step hole, and the outer side surface of the silicon nitride ceramic sealing plate is brazed to the inner side surface of the step hole.

[0012] The provision of the annular plate and the silicon nitride ceramic sealing plate can further improve the sealing performance of the electrical connector and prevent the gas in the high-pressure environment box from leaking out through the electrical connector.

[0013] Preferably, the solder is composed of Ag, Cu, In metal powders and nano-titanium oxide powder, and the mass ratio of Ag, Cu, In metal powders and nano-titanium oxide powder in the solder is (10-14):(4-6):(1-3):1.

[0014] Use a high-precision electronic balance to weigh each component according to the composition ratio of the above solder. Put the weighed Ag, Cu, and In metal powders into a crucible in a vacuum induction melting furnace (the vacuum degree reaches 10-3Pa or above), evacuate the crucible, and then fill it with high-purity argon gas;

[0015] Use a vacuum induction melting furnace to heat the crucible at a heating rate of 5℃ / min-10℃ / min until the temperature is 100℃-150℃ higher than the melting point of the alloy, so that all components are completely melted. After the temperature stabilizes, weigh the nano-TiO2 powder according to 1% of the total mass of each component, and slowly add the nano-TiO2 powder to the molten metal; turn on the electromagnetic stirrer, adjust the stirring speed to 300rpm-400rpm, and continue stirring for 5min-10min to evenly disperse the nano-TiO2 powder in the molten metal; after stirring, use a vacuum induction melting furnace for insulation treatment, the insulation time is 10min-15min, to achieve refining;

[0016] After refining, the molten metal is allowed to cool naturally to room temperature under argon, and the cooled alloy ingot is placed in a ball mill with a mass ratio of grinding balls to alloy ingots of (5-8):1, and ball milling is performed for 10h-20h to obtain alloy powder with a particle size of 50um-100um; flux is added to the alloy powder according to a mass ratio of alloy powder to flux (the flux contains rosin, activator, film-forming agent and other ingredients) of (8-9):1; the two are placed in a mixer and stirred at a speed of 100rpm-200rpm for 15min-30min to fully mix the alloy powder and the flux to finally make solder.

[0017] Nano-titanium oxide is evenly dispersed in the AgCuIn solder, making the diffusion of Ag, Cu, and In elements more uniform and reducing segregation. Ag enhances the bonding strength with the copper core wire, and Cu improves the wettability of the ceramic block (silicon nitride ceramic disc or silicon nitride ceramic sealing plate), avoiding the deformation and cracking of the ceramic block caused by the high residual stress generated during the brazing process, and effectively improving the sealing performance of the electrical connector in extreme environments; In improves the wettability with (the inner side of the stainless steel annular support frame or annular plate), and forms a dense reaction layer with Fe, Cr, etc., ensuring the stability of the welding part, significantly reducing the interruption of signal transmission of the electrical connector, and improving the service life of the electrical connector.

[0018] Preferably, an internal thread is provided on the upper inner side of the stainless steel outer shell, and an external thread is provided on the outer side of the stainless steel inner shell, the internal thread and the external thread are meshed; and an installation thread is provided on the lower outer side of the stainless steel outer shell.

[0019] The stainless steel outer shell and the stainless steel inner shell of the present invention are threadedly connected, which is convenient for flexible control of the filling depth of the mica ring gasket in the annular groove during assembly, and can effectively solve the problem of uneven force on the silicon nitride ceramic circular plate under high pressure environment. The mica ring gasket can be incompletely filled into the annular groove and can be flexibly controlled to leave some floating space. The mica ring gasket can disperse the stress on the silicon nitride ceramic circular plate and further avoid deformation and cracking of the silicon nitride ceramic circular plate.

[0020] A method for soldering an electrical connector in a high-voltage environment box comprises the following steps:

[0021] Step 1-1, assembly before welding:

[0022] Inserting the copper core wire into the corresponding through hole, applying solder in the annular groove, and applying solder on the outer surface of the silicon nitride ceramic circular plate;

[0023] The silicon nitride ceramic circular plate is placed on a stainless steel annular support frame, and the copper core wire is passed through the lower end of the stainless steel lower shell to obtain an assembly;

[0024] Step 1-2, vacuuming:

[0025] Place the hollow base at the bottom of the assembly, place the assembly vertically in the vacuum brazing furnace, and use the three-stage pump of the vacuum brazing furnace to evacuate the vacuum brazing furnace to a vacuum degree of 10 -2 Below Pa;

[0026] Steps 1-3, heating before welding:

[0027] The temperature in the vacuum brazing furnace is raised from room temperature to T1, the value range of T1 is 240℃-250℃, the heating rate is 5℃ / min-6℃ / min, and the temperature is kept for 25min-30min;

[0028] When the room temperature rises to T1, the low-temperature solvent inside the solder can be effectively removed. The low-rate heating can ensure that the solvent inside the solder evaporates completely as much as possible, while ensuring the thermal stability of the electrical connector and making the components of the electrical connector heated evenly.

[0029] The temperature in the vacuum brazing furnace is raised from T1 to T2, the value range of T2 is 550℃-600℃, the heating rate is 4.5℃ / min-5℃ / min, and the heat preservation time is 10min-15min;

[0030] Heating from T1 to T2 can effectively remove the high-temperature solvent inside the solder. Heating at a low rate can gradually evaporate the high-temperature solvent, ensuring that the solvent evaporates completely without affecting subsequent welding; at the same time, ensuring that the components of the electrical connector are heated evenly, preparing for the next step of heating.

[0031] The temperature in the vacuum brazing furnace is raised from T2 to T3, the value range of T3 is 700℃-750℃, the heating rate is 4.5℃ / min-5℃ / min, and the heat preservation time is 10min-15min;

[0032] The temperature is raised from T2 to T3, ensuring that the components of the electrical connector are heated evenly when approaching the melting point of the solder, to avoid directly raising the temperature of the components of the electrical connector to the welding point, which may not achieve the welding effect and bring irreversible internal stress to the components of the electrical connector, which will eventually cause the silicon nitride ceramic disc to crack.

[0033] Steps 1-4, brazing:

[0034] Step 1-4-1, raising the temperature in the vacuum brazing furnace from T3 to T4, where the value range of T4 is 800°C-860°C, the heating rate is 1°C / min-3°C / min, and the temperature is kept for 10min-15min;

[0035] Heating at a rate lower than 3°C / min can ensure that the components of the electrical connector can be heated evenly. If the temperature rises too quickly, the temperature of the silicon nitride ceramic disc cannot keep up, which will cause uneven distribution of the solder.

[0036] Step 1-4-2, the solder is melted, and the solder seals and connects the copper core wire to the silicon nitride ceramic circular plate, and the solder seals and connects the outer side of the silicon nitride ceramic circular plate to the stainless steel annular support frame;

[0037] Steps 1-5, release internal stress:

[0038] The temperature in the vacuum brazing furnace is reduced from T4 to T5, the value range of T5 is 600℃-650℃, the cooling rate is greater than 4℃ / min, and the heat preservation time is 70min-80min;

[0039] During this stage, the temperature needs to be quickly lowered to reduce the continued reaction between the solder and the components of the electrical connector;

[0040] Step 1-6, lowering the temperature in the vacuum brazing furnace from T5 to room temperature, taking the assembly out of the vacuum brazing furnace, and completing the brazing.

[0041] Preferably, a mica annular gasket is provided in the middle of the copper core wire, and an annular groove for accommodating the mica annular gasket is provided at the edge of the upper surface of the silicon nitride ceramic circular plate; and the electrical connector assembly process also includes the following:

[0042] Put the mica ring gasket on each copper core wire, make the mica ring gasket fall into the annular groove, and put the copper core wire sleeve on the upper part of each copper core wire; install the stainless steel inner shell into the upper part of the stainless steel outer shell, make the mica ring gasket float along each copper core wire, make the copper core wire sleeve pass through the upper end of the stainless steel inner shell, and the electrical connector is assembled.

[0043] Preferably, an annular plate made of stainless steel is provided at the lower end of the stainless steel inner shell, a step hole is provided in the middle of the annular plate, and a silicon nitride ceramic sealing plate is provided on the step hole; M sealing holes are provided in the middle of the silicon nitride ceramic sealing plate, and an annular pit for accommodating the brazing material is provided on the sealing hole, and the lower part of the copper core wire passes through the corresponding sealing hole and is brazed to the sealing hole; a gap is provided between the outer side surface of the silicon nitride ceramic sealing plate and the upper part of the inner side surface of the step hole, and the outer side surface of the silicon nitride ceramic sealing plate is brazed to the inner side surface of the step hole;

[0044] Step 1-1 is replaced by the following steps:

[0045] Apply solder to the upper outer portion of the silicon nitride ceramic sealing plate, apply solder to the annular pit, and place the silicon nitride ceramic sealing plate in the upper portion of the step hole;

[0046] Applying solder in the annular groove; applying solder on the outer surface of the silicon nitride ceramic circular plate; placing the silicon nitride ceramic circular plate on a stainless steel annular support frame, inserting the copper core wire into the corresponding through hole and sealing hole in sequence, and passing the copper core wire through the lower end of the stainless steel lower shell to obtain an assembly;

[0047] Steps 1-4-2 are replaced by the following steps:

[0048] The solder melts, and the solder seals the copper core wire and the silicon nitride ceramic circular plate. The solder seals the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame. The solder seals the outer side of the silicon nitride ceramic sealing plate and the upper inner side of the step hole. The solder seals the copper core wire and the silicon nitride ceramic circular plate.

[0049] The solder seals the outer side of the silicon nitride ceramic sealing plate and the upper inner side of the step hole, and the solder seals the copper core wire and the silicon nitride ceramic circular plate, further ensuring the sealing of the electrical connector.

[0050] Therefore, the present invention has the following beneficial effects: no cross-talk occurs when transmitting signals, the sealing performance of the electrical connector in extreme environments is effectively improved, the stability of the welding parts is ensured, the interruption of signal transmission is significantly reduced, and the service life of the electrical connector is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a cross-sectional view of the present invention;

[0052] Figure 2 is a cross-sectional view of the stainless steel inner shell of the present invention;

[0053] Figure 3 is a cross-sectional view of the stainless steel outer shell of the present invention;

[0054] Figure 4 It is a structural schematic diagram of a silicon nitride ceramic circular plate of the present invention;

[0055] Figure 5 It is a structural schematic diagram of the silicon nitride ceramic sealing plate of the present invention;

[0056] Figure 6 It is a structural schematic diagram of the mica ring gasket of the present invention;

[0057] Figure 7 This is a SEM image of the welds of Examples 1 to 3 of the present invention and a comparative example;

[0058] Figure 8 This is a pressure test diagram of Example 1 of the present invention. DETAILED DESCRIPTION

[0059] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0060] Example 1

[0061] like Figure 1-Figure 6 The embodiment shown is an electrical connector for use in a high-voltage environment box, comprising a stainless steel outer shell 1 in the shape of a vertical cylinder, a stainless steel inner shell 2 in the shape of a T which extends into the stainless steel outer shell and is detachably connected to the upper part of the stainless steel outer shell, a silicon nitride ceramic circular plate 3, 5 vertically extending copper core wires 4 and a copper core wire sleeve 41 arranged on the upper part of the copper core wire; the upper and lower ends of the stainless steel inner shell and the stainless steel outer shell are both open, a stainless steel annular support frame 11 is arranged in the middle of the inner side surface of the stainless steel outer shell, and the silicon nitride ceramic circular plate is located on the stainless steel annular support frame; 5 through holes 30 are arranged on the silicon nitride ceramic circular plate, and an annular groove 31 for accommodating solder is arranged on the upper part of the through hole, and the copper core wire passes downward through the corresponding through hole and is brazed to the corresponding through hole; a notch 33 for accommodating solder is arranged on the upper part of the outer side surface of the silicon nitride ceramic circular plate, a gap 32 is arranged between the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate, and the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate are brazed to be connected.

[0062] A mica annular gasket 6 is arranged in the middle of the copper core wire, and an annular groove 34 for accommodating the mica annular gasket is arranged at the edge of the upper surface of the silicon nitride ceramic circular plate.

[0063] An annular plate 10 made of stainless steel is provided at the lower end of the stainless steel inner shell, a step hole 101 is provided in the middle of the annular plate, and a silicon nitride ceramic sealing plate 5 is provided on the step hole; five sealing holes 50 are provided in the middle of the silicon nitride ceramic sealing plate, and an annular pit 51 for accommodating solder is provided on the sealing hole, and the lower part of the copper core wire passes through the corresponding sealing holes and is brazed to the sealing holes; a gap is provided between the outer side surface of the silicon nitride ceramic sealing plate and the upper part of the inner side surface of the step hole, and the outer side surface of the silicon nitride ceramic sealing plate is brazed to the inner side surface of the step hole.

[0064] The solder consists of Ag, Cu, In metal powders and nano titanium oxide powder, and the mass ratio of the Ag, Cu, In metal powders and the nano titanium oxide powder in the solder is 10:6:3:1.

[0065] An internal thread 12 is provided on the upper inner side of the stainless steel outer shell, and an external thread 21 is provided on the outer side of the stainless steel inner shell, the internal thread and the external thread are meshed; a mounting thread 13 is provided on the lower outer side of the stainless steel outer shell.

[0066] A method for soldering an electrical connector in a high-voltage environment box comprises the following steps:

[0067] The silicon nitride ceramic disc and the silicon nitride ceramic sealing plate were boiled in distilled water for 10 minutes, and then ultrasonically cleaned and dried using anhydrous ethanol; the stainless steel outer shell and the stainless steel inner shell were ultrasonically cleaned and dried using anhydrous ethanol, and vacuum degassed at 1050°C;

[0068] Step 1-1, assembly before welding:

[0069] Apply solder to the upper outer portion of the silicon nitride ceramic sealing plate, apply solder to the annular pit, and place the silicon nitride ceramic sealing plate in the upper portion of the step hole;

[0070] Applying solder in the annular groove; applying solder on the outer surface of the silicon nitride ceramic circular plate; placing the silicon nitride ceramic circular plate on a stainless steel annular support frame, inserting the copper core wire into the corresponding through hole and sealing hole in sequence, and passing the copper core wire through the lower end of the stainless steel lower shell to obtain an assembly;

[0071] Step 1-2, vacuuming:

[0072] Place the hollow base at the bottom of the assembly, place the assembly vertically in the vacuum brazing furnace, and use the three-stage pump of the vacuum brazing furnace to evacuate the vacuum brazing furnace to a vacuum degree of 10 -2 Below Pa;

[0073] Steps 1-3, heating before welding:

[0074] The temperature in the vacuum brazing furnace is raised from room temperature to T1, the value range of T1 is 250°C, the heating rate is 6°C / min, and the temperature is kept for 30 minutes;

[0075] The temperature in the vacuum brazing furnace is raised from T1 to T2, the value range of T2 is 600°C, the heating rate is 5°C / min, and the temperature is kept for 15 minutes;

[0076] The temperature in the vacuum brazing furnace is raised from T2 to T3, the value range of T3 is 750°C, the heating rate is 5°C / min, and the temperature is kept for 15 minutes;

[0077] Steps 1-4, brazing:

[0078] Step 1-4-1, raise the temperature in the vacuum brazing furnace from T3 to T4, where the value range of T4 is 860°C, the heating rate is 3°C / min, and the temperature is kept for 15 minutes;

[0079] Step 1-4-2, the solder is melted, the solder seals the copper core wire and the silicon nitride ceramic circular plate, the solder seals the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame, the solder seals the outer side of the silicon nitride ceramic sealing plate and the upper inner side of the step hole, and the solder seals the copper core wire and the silicon nitride ceramic circular plate;

[0080] Steps 1-5, release internal stress:

[0081] The temperature in the vacuum brazing furnace is reduced from T4 to T5, the value range of T5 is 650℃, the cooling rate is 5℃ / min, and the temperature is kept for 80min;

[0082] Step 1-6, lowering the temperature in the vacuum brazing furnace from T5 to room temperature, taking the assembly out of the vacuum brazing furnace, and brazing is completed;

[0083] Put the mica ring gasket on each copper core wire, make the mica ring gasket fall into the annular groove, and put the copper core wire sleeve on the upper part of each copper core wire; install the stainless steel inner shell into the upper part of the stainless steel outer shell, make the mica ring gasket float along each copper core wire, make the copper core wire sleeve pass through the upper end of the stainless steel inner shell, and the electrical connector is assembled.

[0084] When in use, rotate the electrical connector counterclockwise 90°, connect the right end of the copper core wire to the sensor in the high-voltage environmental box, and connect the left end of the copper core wire to the signal receiving end, so that the stainless steel outer shell is connected to the high-voltage environmental box through the installation thread. The mica ring gasket can float left and right along each copper core wire, effectively dispersing the stress on the silicon nitride ceramic circular plate.

[0085] Example 2

[0086] The mass ratio of Ag, Cu, In metal powders and nano titanium oxide powder in the solder of Example 2 is 12:5:2:1.

[0087] The other structural and method contents of Example 2 are the same as those of Example 1.

[0088] Example 3

[0089] The mass ratio of Ag, Cu, In metal powders and nano titanium oxide powder in the solder of Example 3 is 14:4:1:1.

[0090] The other structural and method contents of Example 3 are the same as those of Example 1.

[0091] Comparative Example

[0092] The outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame are brazed and connected by AgCuTi active brazing filler metal at 880°C for 10 minutes, wherein the Ti content in the AgCuTi active brazing filler metal is 4%, and the AgCu alloy is Ag72Cu28.

[0093] Performance Test:

[0094] 1. The electrical connectors of Examples 1 to 3 and the comparative example were placed on a universal testing machine to test the shear strength of the weld between the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame. The electrical connector was placed on a nanoindenter to detect the weld between the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame. The residual stress of the weld was calculated according to the Suresh model. The results are shown in Table 1:

[0095]

[0096]

[0097] Table 1

[0098] It can be seen that the shear strength of the welds of Examples 1 to 3 is much better than that of the comparative example; when the mass ratio of Ag, Cu, In metal powders and nano-titanium oxide powder is 10:6:3:1, the shear strength of the welds is as high as 308.57 MPa, and the residual stress value is 0.21 GPa.

[0099] like Figure 7 As shown, the welds between the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame of the electrical connectors of Example 1, Example 2, Example 3 and the comparative example are scanned and inspected, wherein: Figure 7 Figures (a) to (d) correspond to Example 3, Example 2, Example 1 and the comparative example respectively; it can be seen that the nano-titanium oxide particles are uniformly dispersed in the solder matrix, while in the AgCuTi solder, the Ti element is segregated at the grain boundaries or certain local areas, resulting in inhomogeneity of composition and organization.

[0100] The analysis shows that: due to the dispersion strengthening and fine grain strengthening of nano-titanium oxide particles, the strength of the nano-titanium oxide reinforced AgCuIn solder of the present invention is higher than that of the AgCuTi solder; compared with the AgCuTi solder, the nano-titanium oxide reinforced AgCuIn solder is not prone to brittle fracture when subjected to impact or vibration, and can better adapt to complex working environments;

[0101] At the same time, the thermal expansion coefficient of nano-titanium oxide is relatively low. After being added to the AgCuIn solder, it can reduce the overall thermal expansion coefficient of the solder to a certain extent. The thermal expansion coefficient of the AgCuTi solder is relatively high. Under thermal cycle conditions, the weld is more likely to produce thermal stress, leading to weld failure.

[0102] 2. If Figure 8 As shown, the electrical connector of Example 1 was pressure tested after brazing. It can be seen that the pressure was released after reaching 15.8 MPa, and the silicon nitride ceramic circular plate and the stainless steel shell did not fall off, and the air tightness was intact.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrical connector for use in a high-voltage environment box, characterized in that: The invention comprises a stainless steel outer shell (1) in the shape of a vertical cylinder, a stainless steel inner shell (2) in the shape of a T which extends into the stainless steel outer shell and is detachably connected to the upper part of the stainless steel outer shell, a silicon nitride ceramic circular plate (3), M vertically extending copper core wires (4) and a copper core wire sleeve (41) arranged on the upper part of the copper core wires, where M is greater than or equal to 3; the upper and lower ends of the stainless steel inner shell and the stainless steel outer shell are both open, a stainless steel annular support frame (11) is arranged in the middle of the inner side surface of the stainless steel outer shell, and the silicon nitride ceramic circular plate is located on the stainless steel annular support frame; M through holes (30) are arranged on the silicon nitride ceramic circular plate, an annular groove (31) for accommodating solder is arranged on the upper part of the through hole, the copper core wire passes downward through the corresponding through hole and is brazed to the corresponding through hole; a notch (33) for accommodating solder is arranged on the upper part of the outer side surface of the silicon nitride ceramic circular plate, a gap (32) is arranged between the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate, and the inner side surface of the stainless steel annular support frame and the outer side surface of the silicon nitride ceramic circular plate are brazed to each other.

2. The electrical connector for use in a high-voltage environment box according to claim 1, characterized in that: A mica annular gasket (6) is provided in the middle of the copper core wire, and an annular groove (34) for accommodating the mica annular gasket is provided at the edge of the upper surface of the silicon nitride ceramic circular plate.

3. The electrical connector for use in a high-voltage environment box according to claim 1, characterized in that: An annular plate (10) made of stainless steel is provided at the lower end of the stainless steel inner shell, a step hole (101) is provided in the middle of the annular plate, and a silicon nitride ceramic sealing plate (5) is provided on the step hole; M sealing holes (50) are provided in the middle of the silicon nitride ceramic sealing plate, and an annular pit (51) for accommodating solder is provided on the sealing hole, and the lower part of the copper core wire passes through the corresponding sealing hole and is brazed to the sealing hole; a gap is provided between the outer side surface of the silicon nitride ceramic sealing plate and the upper part of the inner side surface of the step hole, and the outer side surface of the silicon nitride ceramic sealing plate is brazed to the inner side surface of the step hole.

4. The electrical connector for use in a high-voltage environment box according to claim 1, characterized in that: The solder is composed of Ag, Cu, In metal powders and nano titanium oxide powder, and the mass ratio of the Ag, Cu, In metal powders and the nano titanium oxide powder in the solder is (10-14):(4-6):(1-3):

1.

5. The electrical connector for use in a high-voltage environment box according to claim 1, characterized in that: The upper part of the inner side surface of the stainless steel outer shell is provided with an internal thread (12), and the outer side surface of the stainless steel inner shell is provided with an external thread (21), and the internal thread and the external thread are meshed; the lower part of the outer side surface of the stainless steel outer shell is provided with a mounting thread (13).

6. A brazing method for an electrical connector in a high-voltage environment box according to claim 1, characterized in that: The steps include: Step 1-1, assembly before welding: Inserting the copper core wire into the corresponding through hole, applying solder in the annular groove, and applying solder on the outer surface of the silicon nitride ceramic circular plate; The silicon nitride ceramic circular plate is placed on a stainless steel annular support frame, and the copper core wire is passed through the lower end of the stainless steel lower shell to obtain an assembly; Step 1-2, vacuuming: Place the hollow base at the bottom of the assembly, place the assembly vertically in the vacuum brazing furnace, and use the three-stage pump of the vacuum brazing furnace to evacuate the vacuum brazing furnace to a vacuum degree of 10 -2 Below Pa; Steps 1-3, heating before welding: The temperature in the vacuum brazing furnace is raised from room temperature to T1, the value range of T1 is 240℃-250℃, the heating rate is 5℃ / min-6℃ / min, and the temperature is kept for 25min-30min; The temperature in the vacuum brazing furnace is raised from T1 to T2, the value range of T2 is 550℃-600℃, the heating rate is 4.5℃ / min-5℃ / min, and the heat preservation time is 10min-15min; The temperature in the vacuum brazing furnace is raised from T2 to T3, the value range of T3 is 700℃-750℃, the heating rate is 4.5℃ / min-5℃ / min, and the heat preservation time is 10min-15min; Steps 1-4, brazing: Step 1-4-1, raising the temperature in the vacuum brazing furnace from T3 to T4, where the value range of T4 is 800°C-860°C, the heating rate is 1°C / min-3°C / min, and the temperature is kept for 10min-15min; Step 1-4-2, the solder is melted, and the solder seals and connects the copper core wire to the silicon nitride ceramic circular plate, and the solder seals and connects the outer side of the silicon nitride ceramic circular plate to the stainless steel annular support frame; Steps 1-5, release internal stress: The temperature in the vacuum brazing furnace is reduced from T4 to T5, the value range of T5 is 600℃-650℃, the cooling rate is greater than 4℃ / min, and the heat preservation time is 70min-80min; Step 1-6, lowering the temperature in the vacuum brazing furnace from T5 to room temperature, taking the assembly out of the vacuum brazing furnace, and completing the brazing.

7. The method for soldering an electrical connector in a high-voltage environment box according to claim 6, wherein: A mica annular gasket is provided in the middle of the copper core wire, and an annular groove for accommodating the mica annular gasket is provided at the edge of the upper surface of the silicon nitride ceramic circular plate; and the following electrical connector assembly process is also included: Put the mica ring gasket on each copper core wire, make the mica ring gasket fall into the annular groove, and put the copper core wire sleeve on the upper part of each copper core wire; install the stainless steel inner shell into the upper part of the stainless steel outer shell, make the mica ring gasket float along each copper core wire, make the copper core wire sleeve pass through the upper end of the stainless steel inner shell, and the electrical connector is assembled.

8. The brazing method of an electrical connector for a high-voltage environment box according to claim 6 or 7, characterized in that: An annular plate made of stainless steel is provided at the lower end of the stainless steel inner shell, a step hole is provided in the middle of the annular plate, and a silicon nitride ceramic sealing plate is provided on the step hole; M sealing holes are provided in the middle of the silicon nitride ceramic sealing plate, and an annular pit for accommodating the brazing material is provided on the sealing hole, and the lower part of the copper core wire passes through the corresponding sealing hole and is brazed to the sealing hole; a gap is provided between the outer side surface of the silicon nitride ceramic sealing plate and the upper part of the inner side surface of the step hole, and the outer side surface of the silicon nitride ceramic sealing plate is brazed to the inner side surface of the step hole; Step 1-1 is replaced by the following steps: Apply solder to the upper outer portion of the silicon nitride ceramic sealing plate, apply solder to the annular pit, and place the silicon nitride ceramic sealing plate in the upper portion of the step hole; Applying solder in the annular groove; applying solder on the outer surface of the silicon nitride ceramic circular plate; placing the silicon nitride ceramic circular plate on a stainless steel annular support frame, inserting the copper core wire into the corresponding through hole and sealing hole in sequence, and passing the copper core wire through the lower end of the stainless steel lower shell to obtain an assembly; Steps 1-4-2 are replaced by the following steps: The solder melts, and the solder seals the copper core wire and the silicon nitride ceramic circular plate. The solder seals the outer side of the silicon nitride ceramic circular plate and the stainless steel annular support frame. The solder seals the outer side of the silicon nitride ceramic sealing plate and the upper inner side of the step hole. The solder seals the copper core wire and the silicon nitride ceramic circular plate.

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