Plane transformer magnetic core caulking method
By applying a sealing adhesive inside the magnetic core of a planar transformer, the problems of complex sealing and long curing time in existing technologies are solved, achieving efficient core protection and automated processing, and improving product reliability.
Patent Information
- Application Number
- CN202511420707.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2025-11-28
AI Technical Summary
Existing methods for sealing gaps in planar transformer cores are complex, difficult to automate, have long curing times, and are difficult to verify the sealing effect, resulting in low product reliability and yield.
A method of applying and filling sealant inside the planar transformer core is adopted, low-stress adhesive is used to fix the core and printed circuit board, and thermally conductive gel is used to fill the gaps to achieve synchronous curing.
It improves the protection of the magnetic core, reduces the curing time of the sealant, enhances product reliability and bonding efficiency, and is suitable for automated processing.
Smart Images
Figure CN121034840A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of magnetic core bonding of electronic products, and particularly relates to a method for blocking seams of a planar transformer magnetic core. BACKGROUND
[0002] At present, with the trend of smaller volume and higher power density, a large number of planar transformers are adopted, which are composed of built-in windings in printed boards and bonded with magnetic core devices. Such transformers have the characteristics of small volume and low power consumption. Since the products need to be finally filled for heat dissipation, in order to prevent the filling glue from entering the magnetic core, causing the magnetic core to crack during subsequent high-temperature storage, temperature cycling and other environmental tests, the planar transformer generally needs to be blocked.
[0003] The conventional method for blocking seams of a planar transformer magnetic core is to block the path of the filling glue penetrating into the magnetic core by using room temperature curing silicone rubber at the edge of the contact position between the planar transformer magnetic core and the printed board.
[0004] The existing external blocking method has the following disadvantages:
[0005] 1) The external blocking operation is complex, requires high skills of personnel, and is difficult to realize mass production by automatic equipment.
[0006] 2) The external blocking must use room temperature curing silicone rubber, and the complete curing time is as long as 24 hours, which causes the production cycle to be prolonged and is not conducive to realizing flow production.
[0007] 3) The blocking result of external blocking is difficult to check, and once the blocking is not in place, it is easy to cause product scrap, affecting the yield and product reliability. SUMMARY
[0008] The purpose of the present application is to solve the problems existing in the prior art, and to provide a method for filling and blocking seams in a planar transformer magnetic core, which can absorb the stress caused by thermal expansion and contraction of the filling glue during environmental testing and subsequent use of the product, thereby protecting the magnetic core, solving the problem of cracking of the magnetic core after temperature cycling test, and improving the product reliability.
[0009] The technical solution for achieving the purpose of the present application is a method for blocking seams of a planar transformer magnetic core, which comprises the following steps:
[0010] Step 1: Take the E rod of the planar transformer magnetic core, coat the first adhesive on the contact surface with the printed board, and then place the printed board of the corresponding model;
[0011] Step 2: After placing the printed board, coat the second adhesive on the contact surface between the E rod and the I rod of the planar transformer magnetic core;
[0012] Step 3: coating the heat-conducting gel layer by layer in the gap between the planar transformer core E rod and the printed board;
[0013] Step 4: placing the planar transformer core I rod, gently pressing and kneading to make the second adhesive gel evenly flat, fixing it with a clamp, and then placing it in an oven for baking and curing.
[0014] Further, in step 1, the coating area of the first adhesive gel is calculated according to the contact area between the planar transformer core E rod and the printed board, and the coating area is 20-30% of the contact area. After bonding, the gap between the planar transformer core E rod and the printed board is controlled to be 0-0.2 mm.
[0015] Further, in step 2, the coating area of the second adhesive gel is calculated according to the contact area between the planar transformer core E rod and the planar transformer core I rod, and the coating area is 90-100% of the contact area. After bonding, the gap between the planar transformer core E rod and the planar transformer core I rod is controlled to be 0-0.05 mm.
[0016] Further, in step 3, when coating the heat-conducting gel, the dispensing trajectory is one circle around the core column, and the distance from the side of the core is 0.5-1.0 mm.
[0017] Further, in step 3, the coating area of the heat-conducting gel is calculated according to the contact area between the planar transformer core E rod and the printed board, and the coating area is 50-100% of the contact area.
[0018] Further, in step 3, the dispensing height H of the heat-conducting gel is calculated according to the height difference h between the upper surface of the planar transformer core E rod and the printed board, and the calculation formula is:
[0019] H = h + (0.2-1.0) mm.
[0020] Further, in step 4, the tensile shear strength of the first adhesive gel after curing needs to be greater than 5 N / mm2.
[0021] Further, the first adhesive gel needs to have a low thermal expansion coefficient, and the difference between the thermal expansion coefficients of the core and the printed board is less than 10 ppm / ℃; the Tg point of the first adhesive gel needs to be greater than the maximum working or storage temperature of the product; the first adhesive gel is one or more of epoxy resin, polyurethane, acrylic, and silicone, and is a high-temperature resistant material.
[0022] Further, the thixotropic index TI of the heat-conducting gel is above 10; the thermal conductivity of the heat-conducting gel is above 2 W / mK; and the hardness value of the heat-conducting gel is below 60 Shore OO.
[0023] Further, the heat-conducting gel is one or more of a silicon-based single-component non-cured heat-conducting gel and a silicon-based two-component heat-cured heat-conducting gel, and is a high-temperature-resistant material.
[0024] Compared with the prior art, the present application has the following advantages:
[0025] (1) The present application realizes protection of the magnetic core by coating and filling the gap-filling glue inside the planar transformer magnetic core, and has high fault tolerance, a wider process window, solves the problem of cracking of the magnetic core after temperature cycling, and improves the reliability of the product.
[0026] (2) The method of filling and sealing the gap inside the magnetic core realizes synchronous curing of the gap-filling glue and the magnetic core adhesive, reduces the waiting time for curing of the gap-filling glue, and improves the efficiency of the magnetic core bonding.
[0027] (3) The low-stress adhesive is used to fix the magnetic core and the printed board, so as to avoid cracking of the magnetic core under stress.
[0028] (4) The adhesive structure of filling and coating inside the magnetic core is conducive to realizing automatic processing.
[0029] (5) The low-hardness heat-conducting gel filled gap can provide a wider process window and higher product reliability.
[0030] The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0031] Figure 1 It is a schematic diagram of assembly of the planar transformer magnetic core in one embodiment.
[0032] Figure 2 It is a schematic diagram of dispensing of the E rod of the planar transformer magnetic core in one embodiment.
[0033] Figure 3 It is a schematic diagram of dispensing of the heat-conducting gel in one embodiment, wherein Figure 3 (a) in the above figure is a front view, Figure 3 (b) in the above figure is a plan view. DETAILED DESCRIPTION
[0034] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.
[0035] It should be noted that if the embodiments of the present application involve directionality indication (such as up, down, left, right, front, back, etc.), the directionality indication is only used to explain the relative position relationship, motion condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directionality indication also changes accordingly.
[0036] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of a person skilled in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.
[0037] In one embodiment, a planar transformer magnetic core caulking method is provided, the method comprising the following steps:
[0038] Step 1, take the planar transformer magnetic core E rod 1, coat the first adhesive 3 on the contact surface with the printed board, and then place the corresponding model printed board 2;
[0039] Step 2, after placing the printed board 2, coat the second adhesive 4 on the contact surface between the planar transformer magnetic core E rod 1 and the I rod 6;
[0040] Step 3, coat the heat-conducting gel 5 layer by layer in the gap between the planar transformer magnetic core E rod 1 and the printed board 2;
[0041] Step 4, place the planar transformer magnetic core I rod 6, gently press and knead to make the second adhesive 4 evenly flat, then use the clamp to fix and put into the oven for baking and curing.
[0042] The planar transformer magnetic core assembly is as shown in Figure 1 .
[0043] Further, in one of the embodiments, in step 1, the coating area of the first adhesive 3 is calculated according to the contact area between the planar transformer magnetic core E rod 1 and the printed board 2, and the coating area is 20%~30% of the contact area, and the gap between the planar transformer magnetic core E rod 1 and the printed board 2 after bonding is controlled to be 0mm~0.2mm.
[0044] Furthermore, in one embodiment, in step 2, the coating area of the second adhesive 4 is calculated based on the contact area between the planar transformer core E rod 1 and the planar transformer core I rod 6, and the coating area is 90%~100% of the contact area. After bonding, the gap between the planar transformer core E rod 1 and the planar transformer core I rod 6 is controlled at 0mm~0.05mm.
[0045] Furthermore, in one embodiment, when applying the thermally conductive gel 5 in step 3, the dispensing trajectory is one circle around the central pillar of the magnetic core, and the distance from the side edge of the magnetic core is 0.5mm~1.0mm, such as... Figure 2 As shown.
[0046] Furthermore, in one embodiment, such as Figure 3 As shown, the coating area of the thermal conductive gel 5 in step 3 is calculated based on the contact area between the planar transformer core E rod 1 and the printed circuit board 2, and the coating area is 50%~100% of the contact area.
[0047] Furthermore, in one embodiment, the dispensing height H of the thermally conductive gel 5 in step 3 is calculated based on the height difference h between the upper surface of the planar transformer core E rod 1 and the printed circuit board, and the calculation formula is:
[0048] H = h + (0.2~1.0) mm.
[0049] Furthermore, in one embodiment, in step 4, the tensile shear strength of the first adhesive 3 after curing must be greater than 5 N / mm2.
[0050] Furthermore, in one embodiment, the first adhesive 3 needs to have a low coefficient of thermal expansion, and the difference between its coefficient of thermal expansion and that of the magnetic core and the printed circuit board is less than 10 ppm / ℃; the Tg point of the first adhesive 3 needs to be greater than the maximum operating or storage temperature of the product; the first adhesive 3 is one or more of epoxy resin, polyurethane, acrylic acid, and silicone, and is a high-temperature resistant material.
[0051] Furthermore, in one embodiment, the thixotropic index (TI) of the thermally conductive gel is above 10, and it does not sag or drip after dispensing, and can be dispensed in multiple layers; the thermal conductivity of the thermally conductive gel is above 2 W / mK; and the hardness value of the thermally conductive gel is below 60 Shore 00.
[0052] Furthermore, in one embodiment, the thermally conductive gel is one or more of a silicon-based single-component non-curing thermally conductive gel and a silicon-based two-component heat-curing thermally conductive gel, and is a high-temperature resistant material. After the magnetic core is assembled and encapsulated, the thermally conductive gel can withstand the high temperature, low temperature, vibration and other conditions during long-term operation of the product, and the adhesive state no longer changes.
[0053] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.
Claims
1. A method for sealing gaps in the magnetic core of a planar transformer, characterized in that, The method includes the following steps: Step 1: Take the planar transformer core E rod (1), apply the first adhesive (3) to its contact surface with the printed circuit board, and then place the corresponding model of printed circuit board (2). Step 2: After placing the printed circuit board (2), apply the second adhesive (4) to the contact surface between the E rod (1) and the I rod (6) of the planar transformer core. Step 3: Apply thermally conductive gel (5) layer by layer in the gap between the planar transformer core E rod (1) and the printed circuit board (2). Step 4: Place the planar transformer core I rod (6), press and rub lightly to spread the second adhesive (4) evenly, fix it with a clamp, and then bake it in an oven to cure.
2. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, In step 1, the coating area of the first adhesive (3) is calculated based on the contact area between the planar transformer core E rod (1) and the printed circuit board (2). The coating area is 20%~30% of the contact area. After bonding, the gap between the planar transformer core E rod (1) and the printed circuit board (2) is controlled at 0mm~0.2mm.
3. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, In step 2, the coating area of the second adhesive (4) is calculated based on the contact area between the planar transformer core E rod (1) and the planar transformer core I rod (6). The coating area is 90%~100% of the contact area. After bonding, the gap between the planar transformer core E rod (1) and the planar transformer core I rod (6) is controlled at 0mm~0.05mm.
4. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, When applying the thermal conductive gel (5) in step 3, the dispensing trajectory is to circle around the central column of the magnetic core, and the distance from the side of the magnetic core is 0.5mm~1.0mm.
5. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, In step 3, the coating area of the thermal conductive gel (5) is calculated based on the contact area between the planar transformer core E rod (1) and the printed circuit board (2), and the coating area is 50%~100% of the contact area.
6. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, In step 3, the dispensing height H of the thermal conductive gel (5) is calculated based on the height difference h between the upper surface of the planar transformer core E rod (1) and the printed circuit board. The calculation formula is as follows: H = h + (0.2~1.0) mm.
7. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, In step 4, the tensile shear strength of the first adhesive (3) after curing must be greater than 5 N / mm. 2 .
8. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, The first adhesive (3) must have a low coefficient of thermal expansion, and the difference between its coefficient of thermal expansion and that of the magnetic core and the printed circuit board must be less than 10 ppm / ℃; the Tg point of the first adhesive (3) must be greater than the maximum operating or storage temperature of the product; the first adhesive (3) is one or more of epoxy resin, polyurethane, acrylic, and silicone, and is a high-temperature resistant material.
9. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, The thixotropic index (TI) of the thermally conductive gel is above 10; the thermal conductivity of the thermally conductive gel is above 2 W / mK; and the hardness value of the thermally conductive gel is below 60 Shore 00.
10. The method for sealing gaps in a planar transformer core according to claim 1, characterized in that, The thermally conductive gel is one or more of a silicon-based single-component non-curing thermally conductive gel and a silicon-based two-component heat-curing thermally conductive gel, and is a high-temperature resistant material.