Preparation process of metallized magnetic core and product

Abstract

The invention relates to the field of inductance magnetic cores, and discloses a metallized magnetic core and a preparation method thereof. The preparation process of the metallized magnetic core comprises the following steps: S1, printing a polyurethane conductive adhesive containing copper-based powder on an electrode part of the magnetic core, and curing to obtain a printed magnetic core; and S2, sequentially carrying out copper plating, nickel plating and tin plating treatment on the electrode part of the printed magnetic core to prepare the electroplated metallized magnetic core. According to the prepared metallized magnetic core, by printing the polyurethane conductive adhesive, the flexible impact resistance and the conductive interface are increased, the limit mechanical reliability of the metallized magnetic core applied to a high-damp-heat environment and an extreme mechanical environment is improved, and when the metallized magnetic core is subjected to frequent physical impact, vibration and mechanical stress, the service life of the metallized magnetic core is prolonged. And after the metallized magnetic core and the PCB bonding pad are subjected to reflow soldering surface mounting, the problems of falling, cracking and crushing cannot occur, and the mechanical failure probability of the metallized magnetic core electrode is reduced.

Description

Technical Field

[0001] This application relates to the field of inductor cores, and in particular to a manufacturing process and product for a metallized magnetic core. Background Technology

[0002] Metallized magnetic cores are core components of electronic devices that are formed by depositing a conductive metal layer on the surface of a traditional insulated magnetic core using physical / chemical methods, ultimately creating a composite structure of "insulated magnetic core substrate + conductive metal layer". This design simultaneously combines the magnetic permeability of the magnetic core with the conductivity of the metal layer, simplifying the structure of inductors, transformers, and other devices, improving integration and performance. They are widely used in high-frequency, high-current inductors (such as power inductors in switching power supplies, and VRM voltage regulation modules for CPUs and GPUs), EMI suppression inductors in communication equipment, and battery management systems in automotive electronics.

[0003] Metallized magnetic cores in existing technologies are generally prepared using the following two processes: The first is to print or coat silver paste on the electrode areas of the magnetic core, bake and sinter it to form a silver layer, and then electroplate it to form a plating layer, thus obtaining a metallized magnetic core. The second is to perform PVD sputtering deposition on the surface of the magnetic core to form a metal plating layer, thus obtaining a metallized magnetic core.

[0004] Although the metallized magnetic cores prepared by the above two processes have good coating stability, when these metallized magnetic cores are applied to high humidity and heat environments and extreme mechanical environments, they are easily subjected to frequent physical impacts, vibrations and mechanical stresses, which makes the metallized magnetic cores prone to delamination, cracks or even breakage, making the inductor prone to mechanical failure. Summary of the Invention

[0005] To address the problem that metallized magnetic cores manufactured using existing processes are prone to delamination, cracking, or even breakage when subjected to frequent physical impacts, vibrations, and mechanical stresses in high-humidity and high-temperature environments and extreme mechanical environments, leading to the failure of the metallized magnetic cores, this application provides a manufacturing process and product for metallized magnetic cores.

[0006] Firstly, this application provides a manufacturing process for a metallized magnetic core, employing the following technical solution: A process for fabricating a metallized magnetic core includes the following steps: S1. Print a polyurethane conductive adhesive containing copper-based powder onto the electrode area of ​​the magnetic core, cure it, and obtain a printed magnetic core. S2. Electroplating is performed sequentially on the electrode areas of the printed magnetic core to form a copper plating layer, a nickel plating layer, and a tin plating layer, thus obtaining an electroplated metallized magnetic core.

[0007] By adopting the above technical solution, in step S1, printing and curing a polyurethane conductive adhesive containing copper-based powder on the electrode area of ​​the magnetic core increases the flexibility and impact resistance of the magnetic core, while providing a good foundation for subsequent electroplating. In step S2, electroplating is performed sequentially on the printed electrode area of ​​the magnetic core. The copper layer and the polyurethane conductive adhesive containing copper-based powder can be stably bonded, improving the electroplating stability. The three plating layers work synergistically to further enhance the conductivity and corrosion resistance of the metallized magnetic core. This manufacturing process solves the problem that existing metallized magnetic cores are prone to delamination, cracking, and even breakage in high humidity and extreme mechanical environments. The resulting metallized magnetic core improves the ultimate mechanical reliability in high humidity and extreme mechanical environments. It does not delamination, cracking, or breakage when subjected to frequent physical impacts, vibrations, and mechanical stresses, reducing the probability of failure.

[0008] Preferably, the printing thickness of the polyurethane conductive adhesive is 10-30 μm.

[0009] By adopting the above technical solution and optimizing the thickness of the polyurethane conductive adhesive, a flexible, impact-resistant, and conductive interface of appropriate thickness can be formed at the magnetic core electrode, which plays a good role in adhesion, buffering, and impact resistance.

[0010] Preferably, the thickness of the copper plating layer in step S2 is 8-10 μm.

[0011] By adopting the above technical solution and optimizing the copper plating thickness, it is possible to provide good conductivity and ensure good adhesion between the copper plating layer and the polyurethane conductive adhesive of the magnetic core. This avoids the plating layer from peeling off easily due to excessively thick copper plating or from being too thin, which would affect the conductivity.

[0012] Preferably, the thickness of the nickel plating layer in step S2 is 2-5 μm.

[0013] By adopting the above technical solution and optimizing the thickness of the nickel plating layer, it is possible to ensure that the metallized magnetic core has good corrosion resistance and oxidation resistance, while avoiding increased costs and impact on the overall performance of the magnetic core due to excessively thick nickel plating.

[0014] Preferably, the thickness of the tin plating layer in step S2 is 5-15 μm.

[0015] By adopting the above technical solution and optimizing the thickness of the tin plating layer, the oxidation resistance and corrosion resistance of the metallized magnetic core can be improved. Furthermore, the outermost tin plating layer can be further integrated with the subsequent immersion tin treatment, facilitating integration with the subsequent PCBA-level reflow soldering process.

[0016] Preferably, the polyurethane conductive adhesive is a thermosetting polyurethane conductive adhesive, which is made from the following raw materials in parts by weight: 100-120 parts polyurethane resin, 30-50 parts copper-based powder, 0.1-0.5 parts dispersant, and 0.1-0.3 parts leveling agent.

[0017] By adopting the above technical solution, a thermosetting polyurethane conductive adhesive is used. This adhesive cures rapidly under heating conditions, improving production efficiency and forming a stable cross-linked structure after curing, thus enhancing the stability and reliability of the conductive adhesive. Polyurethane resin, as the matrix, provides the conductive adhesive with good flexibility, adhesion, and chemical resistance, ensuring a good bond between the conductive adhesive and the magnetic core electrode. Copper-based powder is a key conductive component, forming conductive pathways in the conductive adhesive and imparting conductivity. Dispersants ensure that the copper-based powder is uniformly dispersed in the polyurethane resin, preventing agglomeration and ensuring uniform and stable conductivity. Leveling agents reduce the surface tension of the conductive adhesive, giving it good leveling properties during printing, ensuring printing quality, and thus improving the extreme mechanical reliability of the metallized magnetic core in high-humidity and high-temperature environments and extreme mechanical environments, reducing the failure probability of the metallized magnetic core.

[0018] Preferably, the polyurethane resin is prepared from a matrix resin and a curing agent, wherein the matrix resin is prepared by reacting toluene diisocyanate, polyol, caprolactam and a catalyst.

[0019] By adopting the above technical solution, toluene diisocyanate, as an isocyanate component, reacts with polyols under the action of a catalyst to form the basic structure of polyurethane, giving the polyurethane resin good reactivity and crosslinking ability; caprolactam can be used as a blocking agent to block the isocyanate groups, improve the storage stability of polyurethane conductive adhesive, so that the polyurethane resin will not react prematurely. The resulting matrix resin is mixed with the curing agent to obtain a thermosetting polyurethane resin, which can undergo stable reaction, crosslinking and curing under heating conditions.

[0020] Preferably, the copper-based powder is composed of flake copper powder and spherical copper powder in a weight ratio of (1-2):1, wherein the particle size of the flake copper powder is 0.5-5 μm and the particle size of the spherical copper powder is 0.1-3 μm.

[0021] By adopting the above technical solutions and optimizing the shape and proportion of copper-based powder, the flake copper powder has a large specific surface area and good orientation, which can form a good conductive network in the polyurethane conductive adhesive, effectively improving the conductivity. The spherical copper powder has a smaller particle size and can fill the gaps between the flake copper powder, increasing the packing density of the copper-based powder, further enhancing the conductivity and the compactness of the polyurethane conductive adhesive, improving the adhesion stability of the copper plating layer and the magnetic core, and helping to improve the ultimate mechanical reliability of the metallized magnetic core in high humidity and heat and extreme mechanical environments, reducing the probability of failure.

[0022] Preferably, the curing temperature of the polyurethane conductive adhesive is 120-200℃.

[0023] By adopting the above technical solution, the optimal curing temperature enables the polyurethane conductive adhesive to cure uniformly and stably, improves the stability of the cured smoothness, reduces the occurrence of bubbles and unevenness, and helps to improve the adhesion stability of the subsequent electroplating layer.

[0024] Secondly, this application provides a metallized magnetic core, which adopts the following technical solution: A metallized magnetic core is prepared by the aforementioned metallized magnetic core manufacturing process.

[0025] By adopting the above technical solution, the metallized magnetic core is printed with polyurethane conductive adhesive in the manufacturing process, which increases the flexibility, impact resistance and conductive interface, and improves the extreme mechanical reliability of the metallized magnetic core in high humidity and heat environments and extreme mechanical environments. When subjected to frequent physical impacts, vibrations and mechanical stresses, the metallized magnetic core will not have problems such as delamination, cracks and breakage, thus reducing the failure probability of the metallized magnetic core.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. The manufacturing process of the metallized magnetic core of this application involves printing and curing a polyurethane conductive adhesive containing copper-based powder on the electrode area of ​​the magnetic core, followed by electroplating to form a copper plating layer, a nickel plating layer, and a tin plating layer. The inclusion of the polyurethane conductive adhesive containing copper-based powder increases the flexibility, impact resistance, and conductive interface of the metallized magnetic core, improves the extreme mechanical reliability of the metallized magnetic core in high humidity and heat environments and extreme mechanical environments, and reduces the failure probability of the metallized magnetic core.

[0027] 2. A thermosetting polyurethane conductive adhesive is selected, and a better weight ratio of flake copper powder and spherical copper powder is used as the copper-based powder. The particle size of the copper-based powder is optimized to further enhance the conductivity and density of the polyurethane conductive adhesive, improve the adhesion stability of the copper plating layer and the magnetic core, and help improve the ultimate mechanical reliability of the metallized magnetic core in high humidity and extreme mechanical environments, and reduce the probability of failure. Attached Figure Description Figure 1 This is a schematic diagram of the structure of the metallized magnetic core of this application; Figure 2 This is a schematic diagram of the structure of the metallized magnetic core of this application after printing polyurethane conductive adhesive and curing. Figure 3 This is a schematic diagram of the structure of the metallized magnetic core of this application.

[0028] Explanation of reference numerals in the attached diagram: 1. Magnetic core; 2. Polyurethane conductive adhesive; 3. Electrode; 4. Coil. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-3 The preparation examples and embodiments further illustrate this application in detail.

[0030] Preparation example of polyurethane conductive adhesive Preparation Example 1 Preparation Example 1 discloses a polyurethane conductive adhesive, which is prepared by the following steps: 10 kg of polyurethane resin, 3 kg of spherical copper powder with a particle size of 1.5 μm, 0.01 kg of dispersant and 0.01 kg of leveling agent were added to a vacuum mixer, stirred evenly, and degassed under vacuum to obtain polyurethane conductive adhesive.

[0031] The polyurethane resin was prepared by using 18 kg of matrix resin and 0.2 kg of MOCA as a curing agent. MOCA is 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0032] The matrix resin was prepared by reacting 2 kg of toluene diisocyanate, 1 kg of polyol, 2.5 kg of caprolactam and 0.002 kg of catalyst at 75 °C for 2 h. The polyol was trimethylolpropane and the catalyst was dibutyltin dilaurate.

[0033] Preparation Examples 2-3 The difference between Preparation Example 2-3 and Preparation Example 1 lies in the amount of raw materials used and the preparation conditions, as detailed in Table 1 below.

[0034] Table 1. Parameters for Preparation Examples 1-3 Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 3 is that the copper-based powder is composed of flake copper powder and spherical copper powder in a weight ratio of 1:1. The particle size of the flake copper powder is 5 μm and the particle size of the spherical copper powder is 0.1 μm. The rest is the same as Preparation Example 3.

[0035] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 3 is that the copper-based powder is composed of flake copper powder and spherical copper powder in a weight ratio of 2:1. The particle size of the flake copper powder is 0.5 μm and the particle size of the spherical copper powder is 3 μm. The rest is the same as Preparation Example 3. Example

[0036] Example 1 Example 1 discloses a fabrication process for a metallized magnetic core, comprising the following steps: S1. A polyurethane conductive adhesive containing copper-based powder, derived from Preparation Example 1, was printed onto the electrode portion of the magnetic core. The printing thickness was 10 μm, and the adhesive was cured at 120°C for 60 min to obtain the printed magnetic core. (Refer to...) Figure 1 and Figure 2 ; S2. Electroplating is performed sequentially on the electrode area of ​​the printed magnetic core to form a copper plating layer with a thickness of 8μm, a nickel plating layer with a thickness of 5μm, and a tin plating layer with a thickness of 15μm, thereby obtaining an electroplated metallized magnetic core. S3. Assemble the electroplated metallized magnetic core, electrodes, and coil, and perform tin plating to obtain the metallized magnetic core. (Refer to...) Figure 3 The magnetic core in this embodiment is an I-shaped ferrite core.

[0037] Example 2-3 The difference between Examples 2-3 and Example 1 lies in the different preparation process parameters, as detailed in Table 2 below.

[0038] Table 2 Parameter table for Examples 1-3 Example 4 The difference between Example 4 and Example 3 is that the polyurethane conductive adhesive is derived from Preparation Example 4, while the rest is the same as in Example 3.

[0039] Example 5 The difference between Example 5 and Example 3 is that the polyurethane conductive adhesive is derived from Example 5, while the rest is the same as Example 3.

[0040] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that the polyurethane conductive adhesive in step S1 is replaced with printed silver paste. The printing thickness of the printed silver paste is 10 μm. It is first baked at 150°C for 60 min and then sintered at 650°C for 12 min. The rest is the same as Example 3.

[0041] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that step S1 is omitted, and PVD treatment is directly performed on the electrode area of ​​the magnetic core to form a copper layer, a nickel layer and a tin layer in sequence. The rest is the same as in Example 3.

[0042] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that copper-based powder was replaced with silver powder in equal amounts, while the rest was the same as Example 3.

[0043] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that the polyurethane conductive adhesive was replaced with epoxy conductive adhesive, which is Teng Hui Technology's epoxy conductive adhesive, model 70P; otherwise, it is the same as Example 3.

[0044] Performance testing was conducted on the metallized magnetic cores prepared in Examples 1-5 and Comparative Examples 1-4 as follows: Specifications of the tested metallized magnetic core: 5*4mm, inductance value of 1μH, maximum DC resistance of 16mΩ.

[0045] 1. Drop test The metallized magnetic core was dropped freely from a height of 1.5m onto the surface of a wooden board, and the drop was repeated 20 times. The inductance value before and after the test was recorded at a temperature of 25℃. The inductance value change rate was less than 3% to be considered qualified. The test results were recorded. 2. Damp heat test The metallized magnetic core was placed at a temperature of 125℃ and a humidity of 85% for 1008 hours, and then restored to 25℃. The inductance value before and after the test was tested. The inductance value change rate was less than 3%, which was considered qualified. The test results were recorded. 3. Impact resistance test Referring to the test method in GB / T 2423.5-2019, the test conditions are: 25℃ temperature, half-sine waveform, peak acceleration 60m / s². 2 The pulse duration is 11ms. The pulse is applied 100 times along the X, Y, and Z directions respectively. The inductance value before and after the test is tested. The inductance value change rate is less than 3% to be considered qualified. The test results are detected and recorded. The following are the performance test data of the metallized magnetic cores prepared in Examples 1-5 and Comparative Examples 1-4, as detailed in Table 3 below.

[0046] Table 3 Performance data of the metallized magnetic cores prepared in Examples 1-5 and Comparative Examples 1-4 Combining Examples 1-3 and Examples 4-5 with Table 3, it can be concluded that further optimizing the shape and particle size of the copper-based powder in the polyurethane conductive adhesive of this application can improve the reliability of the obtained metallized magnet. Compared with Example 3, the metallized magnetic cores obtained in Examples 4-5 showed a decrease in the rate of change of inductance under drop test, damp heat test, and impact test. This may be because the selection of copper-based powder with better specifications improves the density of the polyurethane conductive adhesive, thereby improving the strength and impact resistance of the polyurethane conductive adhesive, and thus improving the stability of the metallized magnetic core under impact and damp heat conditions.

[0047] Based on Examples 1-3 and Comparative Examples 1-2, and referring to Table 3, it can be concluded that the manufacturing process of this application—first printing polyurethane conductive adhesive containing copper-based powder, then electroplating to form copper, nickel, and tin layers, and finally assembling and immersion tin treatment—significantly improves the mechanical reliability of the metallized magnetic core. In Comparative Example 1, silver paste was used to replace the polyurethane conductive adhesive containing copper-based powder, and in Comparative Example 2, direct electroplating was performed, resulting in a significant reduction in the rate of change of inductance of the metallized magnetic core.

[0048] Based on Examples 1-3 and Comparative Examples 3-4, and referring to Table 3, it can be concluded that using the copper-based powder-containing polyurethane conductive adhesive of this application can improve the mechanical reliability of the prepared metallized magnetic core. In Comparative Example 3, replacing the copper-based powder with silver powder increased the inductance change rate of the prepared metallized magnetic core, possibly because the bonding force between the silver-containing polyurethane conductive adhesive and the copper plating layer decreased, thus reducing the mechanical reliability of the metallized magnetic core. In Comparative Example 4, replacing the polyurethane conductive adhesive with epoxy conductive adhesive increased the inductance change rate of the prepared metallized magnetic core, indicating that polyurethane conductive adhesive is more suitable for the technical inductors of this application than epoxy conductive adhesive, and can improve the mechanical reliability of the metallized inductor.

[0049] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A process for fabricating a metallized magnetic core, characterized in that, Includes the following steps: S1. Print a polyurethane conductive adhesive containing copper-based powder onto the electrode area of ​​the magnetic core, cure it, and obtain a printed magnetic core. S2. Electroplating is performed sequentially on the electrode areas of the printed magnetic core to form a copper plating layer, a nickel plating layer, and a tin plating layer, thus obtaining an electroplated metallized magnetic core.

2. The fabrication process of a metallized magnetic core according to claim 1, characterized in that, The printing thickness of the polyurethane conductive adhesive is 10-30µm.

3. The fabrication process of a metallized magnetic core according to claim 1, characterized in that, The thickness of the copper plating layer in step S2 is 8-10µm.

4. The fabrication process of a metallized magnetic core according to claim 1, characterized in that, The thickness of the nickel plating layer in step S2 is 2-5µm.

5. The fabrication process of a metallized magnetic core according to claim 1, characterized in that, The thickness of the tin plating layer in step S2 is 5-15µm.

6. The manufacturing process of a metallized magnetic core according to any one of claims 1-5, characterized in that, The polyurethane conductive adhesive is a thermosetting polyurethane conductive adhesive, which is made from the following raw materials in parts by weight: 100-120 parts polyurethane resin, 30-50 parts copper-based powder, 0.1-0.5 parts dispersant, and 0.1-0.3 parts leveling agent.

7. The fabrication process of a metallized magnetic core according to claim 6, characterized in that, The polyurethane resin is prepared from a matrix resin and a curing agent. The matrix resin is prepared by reacting toluene diisocyanate, polyol, caprolactam and a catalyst.

8. The fabrication process of a metallized magnetic core according to claim 6, characterized in that, The copper-based powder is composed of flake copper powder and spherical copper powder in a weight ratio of (1-2):1, wherein the particle size of the flake copper powder is 0.5-5µm and the particle size of the spherical copper powder is 0.1-3µm.

9. The manufacturing process of a metallized magnetic core according to claim 6, characterized in that, The curing temperature of the polyurethane conductive adhesive is 120-200℃.

10. A metallized magnetic core, characterized in that, It is prepared by the manufacturing process of a metallized magnetic core according to any one of claims 1-9.

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