Coil bubble-free micro-impregnation hot curing process method

Abstract

The application discloses a coil bubble-free micro-impregnation heat curing 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, and 4-6 mm connecting wires are reserved in the middle of the large magnetic core and the small magnetic core, and the remaining wire bundles are perpendicular to the connecting wires and are on the same side; after A and B components of organic silicone glue are mixed according to weight ratio, vacuum degassing is carried out at room temperature, then the coil after finishing is immersed, the coil is taken out after the organic silicone glue completely covers the magnetic core and the enameled wire, and the excess glue is wiped off by using flocked non-woven fabric. The coil after impregnation is clamped on a heat curing tool, vacuum degassing is carried out at room temperature, the heat curing tool is taken out after degassing, the heat curing tool is turned upside down by 180 degrees and placed in a high-temperature oven, and the organic silicone glue is completely cured. The application can solve the problems of uniform coating and quantitative control of the organic silicone glue on the coil surface, completely eliminate the residual bubbles in the silicone glue, and improve the space environmental reliability and the wide-temperature-range environmental adaptability.

Description

Technical Field

[0001] This application relates to the technical field of transformer communication, and in particular to a method for a bubble-free micro-impregnation thermosetting process for coils. Background Technology

[0002] Coils are key components of transformers, used in Ethernet transformers, isolation transformers, and other fields. Industrial-grade transformer coils often use magnetic cores coated with pyrrolidone and polyurethane enameled wire to achieve corrosion resistance and voltage withstand capabilities. By adding a silicone rubber coating to the coil surface, they meet the requirements for wide temperature range and aerospace environment resistance.

[0003] Silicone rubber coating of coil surfaces is typically achieved using two processes: coating with silicone and impregnation. Coating with silicone inside the housing cannot ensure 100% silicone coverage of the coil, while coating and impregnation of the coil individually make it difficult to control the amount of silicone used. Insufficient silicone coverage fails to meet wide-temperature-range performance requirements, while excessive coverage causes difficulties in housing assembly and transformer housing cracking during reflow soldering. Furthermore, neither of these methods effectively eliminates residual air bubbles within the silicone. With the increasing demands for device miniaturization and space-grade durability, it is crucial to address these technological challenges. Summary of the Invention

[0004] This application provides a bubble-free micro-impregnation thermosetting process for coils. By selecting low-viscosity, high-elasticity silicone rubber and innovating the coil impregnation and curing method, the problem of ineffective bubble removal and the inability to achieve uniform and quantitative silicone coating in the injection process is solved. This improves the manufacturability and reliability of transformer products, provides a certain reference for transformer potting processes, and positively promotes the exploration of applications requiring environmental resistance and high reliability in transformers.

[0005] In a first aspect, a method for a bubble-free impregnation and thermosetting process for coils is provided, comprising:

[0006] Prepare silicone rubber and place it in a vacuum environment for degassing treatment;

[0007] After soaking the transformer coil in silicone, remove it.

[0008] Adsorption materials are used to adsorb excess silicone from the surface of the transformer coil.

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

[0010] Remove the transformer coil from the vacuum chamber and dry it.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the preparation of the silicone rubber and the placement of the silicone rubber in a vacuum environment for degassing includes:

[0012] Stir the silicone rubber thoroughly for 5 minutes using a glass rod in a figure-eight motion;

[0013] Place the well-mixed silicone rubber solution in a vacuum chamber and degas for 5-10 minutes at room temperature (25±3℃) and a vacuum level below -0.01MPa. Then remove the solution and observe it under light to see if there are any air bubbles inside the silicone rubber. If so, repeat the above steps once.

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

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the step of immersing the transformer coil in silicone and then removing it includes:

[0016] Vertically and slowly immerse the transformer coil into the silicone rubber in the glass container;

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

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the use of an adsorbent material to adsorb excess silicone rubber on the surface of the transformer coil includes:

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

[0020] In conjunction with the first aspect, in some implementations of the first aspect, the suspension of the transformer coil is achieved by a curing fixture, which includes an upper cover plate and a lower cover plate; the suspension of the transformer coil in a vacuum chamber for degassing treatment includes:

[0021] By fixing the transformer coil after degumming between the upper and lower cover plates, the curing fixture is suspended in the air.

[0022] Rotate the curing fixture 180 degrees so that the top cover of the curing fixture is at the bottom. Remove it after degassing for 5 to 10 minutes in a vacuum chamber at room temperature (25±3℃) and a vacuum degree of less than -0.01MPa.

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

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the upper edge of the transformer coil core is kept 5 to 15 mm away from the front end face of the curing fixture;

[0025] In conjunction with the first aspect, in certain implementations of the first aspect, the step of removing the transformer coil from the vacuum chamber for drying includes:

[0026] After the transformer coil is vacuum degassed, remove the curing fixture, immediately rotate it 180 degrees so that the lower cover of the curing fixture is at the bottom, and place it in a high-temperature oven for curing; after curing, remove the transformer coil from the curing fixture and package it separately.

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

[0028] Before impregnating the transformer coils with adhesive, the enameled wire is twisted into a spiral and then wound around the first and second magnetic cores at equal intervals as required. During winding, ensure that the length of the connecting wire between the two coils is 5±1mm to facilitate the subsequent installation of the transformer coils.

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

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

[0031] (2) The present invention achieves micro-control of the amount of silicone on the outer surface of the coil by impregnating the coil with glue and adsorbing excess silicone with flocked non-woven fabric. This achieves effective coating of the coil, meets the wide temperature range characteristics, and eliminates the risk of shell cracking in high temperature environment due to excessive silicone usage.

[0032] (3) By adopting a process of forward degassing after coil impregnation and then reverse thermal curing, the present invention makes full use of gravity characteristics, solves the problem of bulging after silicone curing in the center ring of the magnetic core, and improves the assembly processability of miniaturized devices. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the coil impregnation in an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of coil cleaning 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 Implementation

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

[0037] To meet the special operating requirements of transformers, it is necessary to provide strain space for transformer coils (especially the magnetic core) under high and low temperature environments. Since silicone rubber generally operates at temperatures between -45℃ and 200℃, it can cover most transformer operating environments and possesses high elasticity and thermal conductivity, making it a suitable coating material for transformer coils. Transformers typically consist of a casing, coils, silicone rubber, and epoxy resin. Because the coefficient of thermal expansion of silicone rubber is much greater than that of the casing and epoxy resin, excessive silicone rubber potting can cause assembly difficulties and easily lead to casing cracking; insufficient silicone rubber cannot provide enough strain space for the coils, easily resulting in substandard high and low temperature inductance. Therefore, controlling the amount of silicone rubber used becomes a challenge in process control. If air bubbles exist inside the cured silicone rubber, there is a risk of these bubbles rupturing and reducing the withstand voltage of the surrounding enameled wire in a vacuum environment. Therefore, eliminating air bubbles within the silicone rubber is essential for withstanding vacuum environments.

[0038] Based on the above analysis, the silicone coating on the coil needs to be as thin as possible, providing sufficient space for high and low temperature strain, while also facilitating the observation of residual bubbles. Considering these factors, this invention provides a bubble-free impregnation and thermosetting process for coils. By selecting silicone with low viscosity, low hardness (high elasticity), and high light transmittance, and combining impregnation, degassing, vacuum degassing, and thermosetting processes, the above technical challenges are solved.

[0039] like Figure 1As shown, the transformer coil prepared by the bubble-free impregnation thermosetting process provided by the present invention includes a first magnetic core 1, a second magnetic core 5, enameled wire 3, and a connecting wire 4. The enameled wire 3 surrounds the outer periphery of the first magnetic core 1 to form a first coil 2. The enameled wire 3 surrounds 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 by a certain distance. The enameled wire 3 is also led outwards from the first coil 2 and the second coil.

[0040] The following is combined Figures 1 to 3 This invention describes a bubble-free impregnation and thermosetting process for coils.

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

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

[0043] Step 2: Prepare silicone 6 and place it in a vacuum environment for degassing.

[0044] Prepare the A and B components of silicone 6 according to the instructions, and stir thoroughly for 5 minutes using a glass rod in a figure-eight motion. Then, place the well-mixed silicone 6 solution in a vacuum chamber at room temperature (25±3℃) and a vacuum level below -0.01MPa for 5-10 minutes to remove air bubbles. Observe the silicone 6 under light to check for any air bubbles. If present, repeat the above steps once. The dynamic viscosity of silicone 6 should be less than 8000 cP, and the Shore hardness should be less than 50. The light transmittance of silicone 6 should be greater than 70%.

[0045] Step 3: Soak the transformer coil in silicone 6 and then remove it.

[0046] Before impregnating the transformer coil with silicone, comb the enameled wire 3 so that it is perpendicular to the connecting wire 4 and positioned to one side of the transformer coil. Ensure that the enameled wire 3 exits smoothly from the winding endpoints of the first magnetic core 1 and the second magnetic core 5, without bending or knotting, and straighten the coil connecting wire 4. Clamp the end of the enameled wire 3 and slowly and vertically immerse the first coil 2 and the second coil into the silicone 6 in the glass container 9. (Reference) 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 both immersed in the liquid surface 7 of the silicone 6, they stay for 1 to 2 seconds, and then the first coil 2 and the second coil are taken out along the inner wall 8 of the glass container 9. The excess silicone on the first coil 2 and the second coil is scraped off on the inner wall 8 of the glass container.

[0047] Step 3: Use an adsorption material to adsorb excess silicone 6 on the surface of the transformer coil.

[0048] Adsorbent materials need to be soft, absorbent, and porous. Non-woven fabric is a fibrous material with a porosity between 30% and 90%. A flocked non-woven fabric 14 is formed through a surface flocking process. This flocked non-woven fabric 14 is soft, breathable, and has good absorbency. (Reference) Figure 2 Fold the flocked nonwoven fabric 14 horizontally to better absorb excess silicone 6 from the surfaces of the first coil 2 and the second coil.

[0049] Specifically, place the first coil 2 and the second coil, after being impregnated with silicone, horizontally on one side of the flocked nonwoven fabric 14. Clamp the tail end 15 of the enameled wire 3 and gently drag the first coil 2 and the second coil to the other side of the flocked nonwoven fabric 14 along a direction perpendicular to the connecting line 4. Then, rotate the first coil 2 and the second coil horizontally 180 degrees and drag them from one side of the flocked nonwoven fabric 14 to the other side again. Utilize the adsorption properties of the pores and fibers on the flocked nonwoven fabric 14 to clean the excess silicone 6 from the central hole 12 of the first magnetic core 1 and the central hole 13 of the second magnetic core 5. If silicone 6 still seeps out, repeat the above steps.

[0050] Step 4: Place the transformer coil in a vacuum chamber for degassing treatment.

[0051] The suspension of the first coil 2 and the second coil can be achieved using the curing fixture 16. For example... Figure 3 As shown, the curing fixture 16 includes an upper cover plate 18 and a lower cover plate 19. The first coil 2 and the second coil, after being cleaned of adhesive, are fixed between the upper cover plate 18 and the lower cover plate 19 of the curing fixture 16, so that the first coil 2 and the second coil are suspended. The upper edge 11 of the first magnetic core 1 can maintain a distance of 5-15 mm (e.g., 10 mm) from the front end face 17 of the curing fixture 16. After clamping, the curing fixture 16 is rotated 180 degrees so that the upper cover plate 18 of the curing fixture 16 is at the bottom. It is then removed after degassing for 5-10 minutes in a vacuum chamber at room temperature (25±3℃) and a vacuum degree below -0.01MPa.

[0052] Optionally, observe whether there are residual air bubbles in the silicone 6 on the surface of the first coil 2 and the second coil. If there are air bubbles, use a needle to prick the air bubbles and remove the residual air. Then, place the coil back into a vacuum chamber at room temperature (25±3℃) and a vacuum degree lower than -0.01MPa for 1 to 2 minutes to remove the air bubbles.

[0053] Step 5: Remove the transformer coil from the vacuum chamber and dry it.

[0054] After the vacuum degassing of the first coil 2 and the second coil is completed, remove the curing fixture 16. Immediately rotate it 180 degrees so that the lower cover plate 19 of the curing fixture 16 is at the bottom, and place it in a high-temperature oven for curing according to the required temperature and time. After curing, remove the first coil 2 and the second coil from the curing fixture 16 and package them separately.

[0055] In this embodiment, the dimensions of the first magnetic core 1 are (outer diameter × inner diameter × thickness = 3.43 × 1.78 × 2.06), and the dimensions of the second magnetic core are (outer diameter × inner diameter × thickness = 3.04 × 1.6 × 1.7). The outer diameter of the enameled wire is 0.11 mm. Through the above process, the amount of silicone impregnation for a set of coils can be precisely controlled between 0.013 ml and 0.015 ml (compared to 0.04 ml to 0.06 ml for traditional coating or potting processes), achieving the process control target of micro-impregnation of the coils. Less silicone coating improves the coil assembly processability, saves coil assembly time (saving 2 minutes per product), and increases the reflow soldering pass rate of transformer products (from 85% to over 99%).

[0056] If opaque silicone is used, the presence of air bubbles can only be checked by X-ray after the silicone has cured; any remaining air bubbles must be removed. In this invention, the silicone 6 has a transmittance of over 70%, allowing for rapid inspection of air bubble residue after both degassing and curing. This ensures that each process is bubble-free, improving inspection efficiency and yield, and is more environmentally friendly and economical than traditional coating and potting processes. Furthermore, by performing two vacuum degassing processes to remove air bubbles from the silicone 6 and quickly checking for air bubble residue after curing, the conventional X-ray inspection for air bubble residue is replaced.

[0057] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can 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 should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for heat-curing coil impregnation without bubbles, characterized in that, include: Prepare silicone rubber and place it in a vacuum environment for degassing treatment. The silicone rubber has a Shore hardness of less than 50 and a light transmittance of more than 70%. After soaking the transformer coil in silicone, remove it. Excess silicone rubber on the surface of the transformer coil is adsorbed using an adsorbent material. The dynamic viscosity of the silicone rubber is less than 8000 cP. The adsorbent material is flocked nonwoven fabric, which is formed by flocking on the surface of a nonwoven fabric with a porosity between 30% and 90%. The flocked nonwoven fabric is folded horizontally, and the silicone-impregnated transformer coil is placed horizontally on one side of the flocked nonwoven fabric. The transformer coil is dragged to the other side of the flocked nonwoven fabric, and then the transformer coil is flipped horizontally 180 degrees. The transformer coil is dragged from one side of the flocked nonwoven fabric to the other side again. The transformer coil is suspended in a vacuum chamber for degassing treatment; Remove the transformer coils from the vacuum chamber and dry them; The process of suspending the transformer coil in mid-air is achieved using a curing fixture, which includes an upper cover plate and a lower cover plate; the process of suspending the transformer coil in mid-air within a vacuum chamber for degassing includes: By fixing the transformer coil after degumming between the upper and lower cover plates, the curing fixture is suspended in the air. Rotate the curing fixture 180 degrees so that the top cover of the curing fixture is at the bottom. Remove it after degassing for 5 to 10 minutes in a vacuum chamber at room temperature of 25±3℃ and a vacuum degree of less than -0.01MPa. The step of removing the transformer coil from the vacuum chamber and drying it includes: After the transformer coil is vacuum degassed, remove the curing fixture, immediately rotate it 180 degrees so that the lower cover of the curing fixture is at the bottom, and place it in a high-temperature oven for curing; after curing, remove the transformer coil from the curing fixture and package it separately.

2. The method according to claim 1, characterized in that, The preparation of the silicone rubber and the degassing treatment of the silicone rubber in a vacuum environment include: Stir the silicone rubber thoroughly for 5 minutes using a glass rod in a figure-eight motion; Place the well-mixed silicone rubber solution in a vacuum chamber and degas for 5-10 minutes at room temperature (25±3℃) and vacuum level (less than -0.01MPa). Then remove the solution and observe it under light to see if there are any air bubbles inside the silicone rubber. If so, repeat the above steps once.

3. The method according to claim 1, characterized in that, The process of immersing the transformer coil in silicone and then removing it includes: Vertically and slowly immerse the transformer coil into the silicone rubber in the glass container; When the upper edge of the transformer coil core is immersed in the silicone liquid, hold for 1 to 2 seconds, then remove the transformer coil along the inner wall of the glass container and scrape off the excess silicone on the inner wall of the glass container.

4. The method according to claim 1, characterized in that, Before drying, observe whether there are any residual air bubbles in the silicone on the surface of the transformer coil. If there are air bubbles, use a needle to break them and remove the residual air. Then, place the transformer coil in a vacuum chamber at room temperature of 25±3℃ and a vacuum degree of less than -0.01MPa for 1 to 2 minutes to remove the air bubbles.

5. The method according to claim 1, characterized in that, The upper edge of the transformer coil core should be 5-15mm away from the front end of the curing fixture.

6. The method according to claim 1, characterized in that, The method is used to prepare a transformer coil comprising a first magnetic core, a second magnetic core, enameled wire, and a connecting wire; the enameled wire is wrapped around the outer periphery of the first magnetic core to form a first coil; the enameled wire is wrapped 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 by a certain distance; the enameled wire is also led outward from the first coil and the second coil. Before impregnating the transformer coils with adhesive, the enameled wire is twisted into a spiral and then wound around the first and second magnetic cores at equal intervals as required. During winding, ensure that the length of the connecting wire between the two coils is 5±1mm to facilitate the subsequent installation of the transformer coils.

Images