Coil bubble-free trace impregnation thermocuring process method

Abstract

The invention discloses a coil bubble-free trace impregnation thermocuring process method which comprises the following steps: four enameled wires are wound on a large magnetic core and a small magnetic core according to process requirements to form a coil, a 4-6mm connecting wire is reserved between the large magnetic core and the small magnetic core, and other wire harnesses are perpendicular to the connecting wire and are positioned on the same side. The organic silica gel A and the organic silica gel B are proportioned by weight and then subjected to vacuum defoaming at room temperature, then the finished coil is immersed until the magnetic core and the enameled wire are completely coated by the organic silica gel and then is taken out, and redundant gel liquid is wiped off by adopting flocked non-woven fabric. The coil obtained after gum dipping is completed is clamped on a thermocuring tool, and room-temperature vacuum defoaming is carried out; and after defoaming, taking out the curing tool, turning over the curing tool up and down by 180 degrees, and placing the curing tool in a high-temperature oven until the organic silica gel is completely cured. The problems of uniform coating and quantitative control of the organic silica gel on the surface of the coil can be solved, bubble residues in the silica gel are thoroughly eliminated, and the space environment reliability and the wide-temperature-range environment adaptability are improved.

Description

Technical Field

[0001] The present application relates to the technical field of transformer communication, and in particular to a coil bubble-free trace dipping thermal curing process method. Background Art

[0002] The coil is a key component of the transformer and is used in Ethernet transformers, isolation transformers and other fields. Industrial-grade transformer coils mostly use cores coated with parylene and polyurethane enameled wire to achieve corrosion resistance and pressure resistance. By adding silicone rubber to the surface of the coil, the requirements for wide temperature range and resistance to aerospace environment can be met.

[0003] The surface of the coil is coated with silicone rubber by two methods: spraying and dipping. The spraying method inside the shell cannot ensure that the silicone covers the coil 100%, and the amount of silicone cannot be controlled by spraying and dipping the coil alone. The small amount of silicone cannot meet the wide temperature range index characteristics, and the large amount of silicone coating makes it difficult to assemble the shell and crack the transformer shell during the reflow soldering process. And the above two methods cannot effectively eliminate the residual bubbles in the silicone. With the miniaturization of devices and the need to withstand space environments, the above process problems need to be solved urgently. Summary of the invention

[0004] The present application provides a coil bubble-free micro-impregnation thermal curing process method. By selecting low-viscosity, high-elasticity silicone rubber and innovating the coil impregnation curing method, the problem that the injection process cannot effectively discharge bubbles and cannot achieve uniform and quantitative control of silicone coating is solved. The processability and reliability of transformer products are improved, which has a certain reference significance for the transformer potting process and has a positive significance for the exploration of the application requirements of transformer environmental resistance and high reliability.

[0005] In a first aspect, a coil bubble-free dipping and thermal curing process method is provided, comprising:

[0006] Prepare organic silica gel, and place the organic silica gel in a vacuum environment for degassing;

[0007] Soak the transformer coil in silicone and take it out;

[0008] Adopt adsorption material to absorb excess organic silica gel on the surface of transformer coil;

[0009] The transformer coil is suspended in a vacuum box for degassing treatment;

[0010] The transformer coil is removed from the vacuum box for drying.

[0011] In combination with the first aspect, in certain implementations of the first aspect, preparing the organic silica gel and placing the organic silica gel in a vacuum environment for degassing treatment includes:

[0012] Use a glass rod in the shape of an "8" to fully stir the organic silica gel for 5 minutes;

[0013] Place the evenly mixed organic silica gel solution in a vacuum box, degas for 5 to 10 minutes at room temperature (25±3℃) and a vacuum degree below -0.01MPa, then take it out and observe through light whether there are bubbles in the organic silica gel. If so, repeat the above steps once.

[0014] In combination with the first aspect, in certain implementations of the first aspect, the dynamic viscosity of the organic silicone is less than 8000 cP, the Shore hardness is less than 50, and the light transmittance of the organic silicone is greater than 70%.

[0015] In combination with the first aspect, in certain implementations of the first aspect, the step of soaking the transformer coil in organic silica gel and then taking it out includes:

[0016] Slowly immerse the transformer coil vertically into the silicone in the glass container;

[0017] When the upper edge of the transformer coil core is immersed in the liquid surface of the silicone gel, stay for 1 to 2 seconds, then take out the transformer coil along the inner wall of the glass container, and scrape off the excess silicone on the transformer coil on the inner wall of the glass container.

[0018] In combination with the first aspect, in certain implementations of the first aspect, the using of an adsorption material to adsorb excess organic silica gel on the surface of the transformer coil includes:

[0019] Place the impregnated transformer coil horizontally on one side of the flocked non-woven fabric, gently drag the transformer coil to the other side of the flocked non-woven fabric, then flip the transformer coil horizontally 180 degrees, and drag the transformer coil from one side of the flocked non-woven fabric to the other side again. The flocked non-woven fabric is formed by a flocking process on the surface of a non-woven fabric with a porosity between 30% and 90%.

[0020] In combination with the first aspect, in certain implementations of the first aspect, the placing of the transformer coil in the air is achieved by a curing tool, and the curing tool includes an upper cover plate and a lower cover plate; the placing of the transformer coil in the air in a vacuum box for degassing treatment includes:

[0021] The transformer coil after clearing the glue is fixed between the upper cover plate and the lower cover plate, so that the curing tooling is suspended;

[0022] Turn the curing tooling 180 degrees so that the upper cover of the curing tooling is at the bottom, degas in a vacuum box at room temperature (25±3°C) and a vacuum degree lower than -0.01MPa for 5 to 10 minutes, and then take it out.

[0023] In combination with the first aspect, in certain implementations of the first aspect, before drying, observe whether there are residual bubbles in the silicone on the surface of the transformer coil. If there are bubbles, use a needle to prick the bubbles to expel the residual air, and then put it into a vacuum box at room temperature (25±3°C) and a vacuum degree lower than -0.01MPa for degassing for 1 to 2 minutes before taking it out.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the upper edge of the transformer coil core is kept 5 to 15 mm away from the front end surface of the curing tooling;

[0025] In combination with the first aspect, in certain implementations of the first aspect, taking the transformer coil out of the vacuum box for drying includes:

[0026] After the vacuum degassing of the transformer coil is completed, the curing tooling is taken out, immediately turned 180 degrees so that the lower cover of the curing tooling is located at the bottom, and placed in a high-temperature oven for curing; after curing, the transformer coil is removed from the curing tooling and packaged separately.

[0027] In combination with the first aspect, in certain implementations of the first aspect, the transformer coil prepared by the method includes a first magnetic core, a second magnetic core, an enameled wire, and a connecting wire; the enameled wire is wrapped around the outer circumference of the first magnetic core to form a first coil; the enameled wire is wrapped around the outer circumference of the second magnetic core to form a second coil; the connecting wire connecting the first coil and the second coil is formed by extending the enameled wire for a certain distance; and the enameled wire is also led outward from the first coil and the second coil;

[0028] Before dipping the transformer coil in glue, twist the enameled wire into a twisted wire, and then wrap it around the first magnetic core and the second magnetic core at equal intervals as required. When winding, ensure that the length of the connecting wire between the two coils is 5±1mm to facilitate the subsequent installation of the transformer coil.

[0029] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0030] (1) The present invention uses organic silicone with low viscosity, low hardness (high elasticity) and certain transparency. Low viscosity can improve the coating effect of organic silicone on the coil; low hardness (high elasticity) can solve the problem of satisfying the high and low temperature characteristics of the coil with a small amount of coating; the transparency of organic silicone can solve the problem of difficulty in inspecting internal bubbles after curing, replacing the process of X-ray inspection of residual bubbles, making the production process more environmentally friendly and economical.

[0031] (2) The present invention achieves micro-control of organic silicone on the outer surface of the coil by dipping the coil in glue and absorbing excess silicone with flocking non-woven fabric, thereby achieving effective coating of the coil, meeting the wide temperature range characteristics, and eliminating the risk of shell cracking in a high temperature environment due to excessive use of silicone.

[0032] (3) The present invention adopts a process method of forward degassing after coil dipping and then reverse thermal curing, which fully utilizes the gravity characteristics, solves the bulging phenomenon after the silicone in the center ring of the magnetic core is cured, and improves the assembly processability of miniaturized devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the coil dipping process according to an embodiment of the present invention.

[0034] Figure 2 Schematic diagram of coil glue removal according to an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of coil curing according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] To meet the use requirements of transformers in special environments, it is necessary to provide strain space for transformer coils (especially magnetic cores) in high and low temperature environments. Since the use temperature of silicone rubber is generally between -45℃ and 200℃, it can cover the use environment of most transformers, and it has high elasticity and thermal conductivity, so it is used as a covering material for transformer coils. Transformers usually include shells, coils, silicone and epoxy glue. Since the thermal expansion coefficient of silicone is much larger than that of shells and epoxy glue, excessive silicone potting makes product assembly difficult and easily causes shell cracking; insufficient silicone cannot provide sufficient strain space for the coil, which easily causes the high and low temperature inductance of the coil to be unqualified. Therefore, how to control the amount of silicone becomes a difficult point in process control. If there are bubbles inside the silicone after curing, there is a risk of bubbles bursting and reducing the pressure resistance of the surrounding enameled wire in a vacuum environment. Therefore, eliminating bubbles in silicone has become a must for space environment resistance.

[0038] According to the above analysis, the organic silicone coated on the outside of the coil needs to be as thin as possible and be able to provide sufficient high and low temperature strain space, while being easy to observe the bubble residue. Based on the above considerations, the present invention provides a bubble-free coil dipping and thermal curing process. Organic silicone with low viscosity, low hardness (high elasticity) and light transmittance is selected, and combined with dipping, cleaning, vacuum degassing and thermal curing processes to solve the above technical problems.

[0039] like Figure 1As shown, the transformer coil prepared by the coil bubble-free dipping and thermal curing process provided by the present invention comprises a first magnetic core 1, a second magnetic core 5, an enameled wire 3, and a connecting wire 4. The enameled wire 3 is wrapped around the outer periphery of the first magnetic core 1 to form a first coil 2. The enameled wire 3 is wrapped around the outer periphery of the second magnetic core 5 to form a second coil. The connecting wire 4 connecting the first coil 2 and the second coil is formed by extending the enameled wire 3 for a certain distance. The enameled wire 3 is also led outward from the first coil 2 and the second coil.

[0040] Combine the following Figures 1 to 3 The invention describes a coil bubble-free adhesive dipping and thermal curing process method.

[0041] Step 1: wrap the enameled wire 3 around the first magnetic core 1 and the second magnetic core 5.

[0042] The enameled wire 3 is first twisted into a twisted wire (the enameled wire 3 can be 4 enameled wires of the same specification), and then wrapped around the first magnetic core 1 and the second magnetic core 5 at equal intervals as required. When winding, ensure that the length of the two coil connecting wires 4 is 5±1mm to facilitate the subsequent installation of the transformer coil.

[0043] Step 2, preparing organic silica gel 6, and placing the organic silica gel 6 in a vacuum environment for degassing treatment.

[0044] Mix the A and B components of organic silica gel 6 according to the instructions, and stir them thoroughly for 5 minutes with a glass rod in the shape of "8". Then place the mixed organic silica gel 6 solution in a vacuum box, degas for 5 to 10 minutes at room temperature (25±3℃) and a vacuum degree lower than -0.01MPa, then take it out and observe whether there are bubbles in the organic silica gel 6 through light. If there are, repeat the above steps once. The dynamic viscosity of organic silica gel 6 must be less than 8000cP and the Shore hardness must be less than 50. The light transmittance of organic silica gel 6 must be greater than 70%.

[0045] Step 3, soak the transformer coil in organic silica gel 6 and then take it out.

[0046] Before dipping the transformer coil, comb the enameled wire 3 to be perpendicular to the connecting wire 4 and on one side of the transformer coil, ensure that the enameled wire 3 is smoothly drawn out from the winding end of the first magnetic core 1 and the second magnetic core 5, without bending or tangling, and straighten the coil connecting wire 4. Clamp the tail end of the enameled wire 3, and vertically and slowly dip the first coil 2 and the second coil into the organic silica gel 6 in the glass container 9. Figure 1 When the upper edge 11 of the first magnetic core 1 and the upper edge 10 of the second magnetic core 5 are immersed in the liquid surface 7 of the organic silica gel 6, stay for 1 to 2 seconds, then take out the first coil 2 and the second coil along the inner wall 8 of the glass container 9, and scrape off the excess organic silica gel on the first coil 2 and the second coil on the inner wall 8 of the glass container.

[0047] Step 3: using an adsorption material to adsorb excess organic silica gel 6 on the surface of the transformer coil.

[0048] The adsorbent material needs to be soft, absorbent, porous, etc. Non-woven fabric is a fiber material with a porosity between 30% and 90%. The flocked non-woven fabric 14 is formed by a surface flocking process. The flocked non-woven fabric 14 is soft, breathable, and has good adsorption properties. Figure 2 , fold the flocked non-woven fabric 14 horizontally so that it can better absorb the excess organic silica gel 6 on the surfaces of the first coil 2 and the second coil.

[0049] Specifically, place the first coil 2 and the second coil after the dip in glue horizontally on one side of the flocked non-woven fabric 14, clamp the tail end 15 of the enameled wire 3, gently drag the first coil 2 and the second coil to the other side of the flocked non-woven fabric 14 in a direction perpendicular to the connecting wire 4, and then flip the first coil 2 and the second coil horizontally 180 degrees, and drag the first coil 2 and the second coil from one side of the flocked non-woven fabric 14 to the other side again, making full use of the adsorption characteristics of the pores and fluff on the flocked non-woven fabric 14 to clean the excess organic silica gel 6 in the center hole 12 of the first magnetic core 1 and the center hole 13 of the second magnetic core 5. If there is still organic silica gel 6 seeping out, repeat the above steps.

[0050] Step 4: suspend the transformer coil in a vacuum box for degassing.

[0051] The first coil 2 and the second coil can be suspended by the curing tool 16. Figure 3 As shown, the curing tool 16 includes an upper cover plate 18 and a lower cover plate 19. The first coil 2 and the second coil after the glue is cleared are fixed between the upper cover plate 18 and the lower cover plate 19 of the curing tool 16, so that the first coil 2 and the second coil are suspended. The upper edge 11 of the first magnetic core 1 and the front end surface 17 of the curing tool 16 can maintain a distance of 5 to 15 mm (for example, 10 mm). After clamping, the curing tool 16 is turned over 180 degrees so that the upper cover plate 18 of the curing tool 16 is located at the bottom, and it is taken out after degassing for 5 to 10 minutes in a vacuum box at room temperature (25±3°C) and a vacuum degree lower than -0.01MPa.

[0052] Optionally, observe whether there are residual bubbles in the organic silica gel 6 on the surface of the first coil 2 and the second coil. If there are bubbles, use a needle to prick the bubbles to expel the residual air, and then put them into a vacuum box at room temperature (25±3°C) and a vacuum degree below -0.01MPa for degassing for 1 to 2 minutes before taking them out.

[0053] Step 5, take the transformer coil out of the vacuum box and dry it.

[0054] After vacuum degassing of the first coil 2 and the second coil is completed, the curing tool 16 is taken out. Immediately flip it 180 degrees so that the lower cover plate 19 of the curing tool 16 is located at the bottom, and place it in a high-temperature oven to cure it according to the temperature and time required by the process. After curing, the first coil 2 and the second coil are removed from the curing tool 16 and packaged separately.

[0055] In this embodiment, the size of the first magnetic core 1 is (outer diameter × inner diameter × thickness = 3.43 × 1.78 × 2.06), the size of the second magnetic core is (outer diameter × inner diameter × thickness = 3.04 × 1.6 × 1.7), and the outer diameter of the enameled wire is 0.11 mm. Through the above process method, the amount of glue impregnation of a group of coils can be accurately controlled between 0.013ml and 0.015ml (the amount of organic silica gel used in the traditional glue pouring or glue filling process is between 0.04ml and 0.06ml), achieving the process control goal of micro-dipping of coils; the amount of silica gel coating is less, which improves the processability of coil assembly, saves coil assembly time (saves 2 minutes for each product), and improves the reflow soldering pass rate of transformer products (from 85% to more than 99%).

[0056] If organic silica gel without light transmittance is used, the residual bubbles can only be checked by X-ray after the silicone gel is cured, and if there are any residual bubbles, they can only be removed. The organic silica gel 6 in the present invention has a light transmittance greater than 70%, and the residual bubbles can be quickly checked after degassing and curing, ensuring that there are no bubbles after each process, improving the inspection efficiency and pass rate, and being more environmentally friendly and economical than the traditional glue spraying and glue filling process. In addition, the bubbles in the organic silica gel 6 are discharged through two vacuum degassings, and the residual bubbles in the silicone gel after curing are quickly checked, replacing the conventional X-ray ray inspection process for residual bubbles.

[0057] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A coil bubble-free dipping and thermal curing process, characterized in that: include: Prepare organic silica gel, and place the organic silica gel in a vacuum environment for degassing; Soak the transformer coil in silicone and take it out; Adopt adsorption material to absorb excess organic silica gel on the surface of transformer coil; The transformer coil is suspended in a vacuum box for degassing treatment; The transformer coil is removed from the vacuum box for drying.

2. The method according to claim 1, characterized in that The step of preparing the organic silica gel and placing the organic silica gel in a vacuum environment for degassing treatment comprises: Use a glass rod in the shape of "8" to fully stir the organic silica gel for 5 minutes; Place the evenly mixed organic silica gel solution in a vacuum box, degas for 5 to 10 minutes at room temperature (25±3℃) and a vacuum degree below -0.01MPa, then take it out and observe through light whether there are bubbles in the organic silica gel. If so, repeat the above steps once.

3. The method according to claim 1 or 2, characterized in that: The dynamic viscosity of the organic silicone is less than 8000 cP, the Shore hardness is less than 50, and the light transmittance of the organic silicone is greater than 70%.

4. The method according to claim 1, characterized in that The step of soaking the transformer coil in organic silica gel and then taking it out comprises: Slowly immerse the transformer coil vertically into the silicone in the glass container; When the upper edge of the transformer coil core is immersed in the liquid surface of the silicone gel, stay for 1 to 2 seconds, then take out the transformer coil along the inner wall of the glass container, and scrape off the excess silicone on the transformer coil on the inner wall of the glass container.

5. The method according to claim 1, characterized in that: The method of using an adsorption material to adsorb excess organic silica gel on the surface of the transformer coil includes: Place the impregnated transformer coil horizontally on one side of the flocked non-woven fabric, gently drag the transformer coil to the other side of the flocked non-woven fabric, then flip the transformer coil horizontally 180 degrees, and drag the transformer coil from one side of the flocked non-woven fabric to the other side again. The flocked non-woven fabric is formed by a flocking process on the surface of a non-woven fabric with a porosity between 30% and 90%.

6. The method according to claim 1, characterized in that The step of placing the transformer coil in the air in a suspended state is achieved by a curing tool, which includes an upper cover plate and a lower cover plate; the step of placing the transformer coil in the air in a vacuum box for degassing treatment includes: The transformer coil after clearing the glue is fixed between the upper cover plate and the lower cover plate, so that the curing tooling is suspended; Turn the curing tooling 180 degrees so that the upper cover of the curing tooling is at the bottom, degas in a vacuum box at room temperature (25±3°C) and a vacuum degree lower than -0.01MPa for 5 to 10 minutes, and then take it out.

7. The method according to claim 6, characterized in that Before drying, observe whether there are residual bubbles in the silicone on the surface of the transformer coil. If there are bubbles, use a needle to prick the bubbles to expel the residual air, and then put it into a vacuum box at room temperature (25±3℃) and a vacuum degree below -0.01MPa to degas for 1 to 2 minutes before taking it out.

8. The method according to claim 6, characterized in that The upper edge of the transformer coil core is kept 5 to 15 mm away from the front end surface of the curing tooling.

9. The method according to any one of claims 6 to 8, characterized in that The step of taking the transformer coil out of the vacuum box and drying it comprises: After the vacuum degassing of the transformer coil is completed, the curing tooling is taken out, immediately turned 180 degrees so that the lower cover of the curing tooling is located at the bottom, and placed in a high-temperature oven for curing; after curing, the transformer coil is removed from the curing tooling and packaged separately.

10. The method according to claim 1, characterized in that The transformer coil prepared by the method comprises a first magnetic core, a second magnetic core, an enameled wire, and a connecting wire; the enameled wire is wound around the outer periphery of the first magnetic core to form a first coil; the enameled wire is wound around the outer periphery of the second magnetic core to form a second coil; the connecting wire connecting the first coil and the second coil is formed by extending the enameled wire for a certain distance; the enameled wire is also led outward from the first coil and the second coil; Before dipping the transformer coil in glue, twist the enameled wire into a twisted wire, and then wrap it around the first magnetic core and the second magnetic core at equal intervals as required. When winding, ensure that the length of the connecting wire between the two coils is 5±1mm to facilitate the subsequent installation of the transformer coil.

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