Anti-electromagnetic interference filter with sealing structure and manufacturing method thereof

Abstract

The invention discloses an anti-electromagnetic interference filter with a sealing structure and a manufacturing method thereof.The anti-electromagnetic interference filter comprises a metal bottom plate, a metal shell and a metal cover plate, the metal bottom plate and the metal cover plate are installed at the upper end and the lower end of the metal shell in a sealed mode respectively, an annular boss is arranged in the metal bottom plate, and a lower circuit board is installed on the annular boss; four annular magnetic cores are installed on the lower circuit board, an upper circuit board is installed at the upper ends of the four annular magnetic cores, four electrodes penetrate through the four annular magnetic cores to form a feed-through inductor, the four electrodes are fixedly and electrically connected with the upper circuit board, two input electrodes penetrate through the lower circuit board in a suspended mode, and the other two input electrodes are fixedly and electrically connected with the lower circuit board. Three of the four electrodes are fixedly connected to the metal bottom plate through glass insulators, and the other electrode is fixedly connected with the metal bottom plate to form a grounding end. According to the structure, a very good suppression effect is achieved at 10 MHz to 1 GHz, the space volume of the filter is reduced, and short circuit of the capacitor caused by improper cleaning of the capacitor is also avoided.

Description

Technical Field

[0001] The invention relates to an anti-electromagnetic interference filter with a sealed structure and a manufacturing method thereof, belonging to the technical field of anti-electromagnetic interference filters. Background Art

[0002] Electromagnetic compatibility (EMC) describes the ability of a device or system to work properly in its electromagnetic environment without causing unacceptable electromagnetic disturbance to anything in the environment. Specifically, it ensures that electronic equipment will not interfere with other equipment or be affected by external interference during operation. It includes two key aspects: electromagnetic interference (EMI) and interference immunity (EMS). EMI refers to the interference of electromagnetic energy generated by the device to the surrounding environment during normal operation, while EMS refers to the device's ability to resist interference from external electromagnetic fields.

[0003] At present, most DC-DC converter power systems require the ability to resist electromagnetic interference. It is necessary to add an EMI filter between the power supply and the converter to suppress electromagnetic interference, or add an EMI filter between the DC-DC converter and the working electronic equipment to suppress electromagnetic interference, to ensure that the converter and the electronic equipment use a clean DC voltage. In order to ensure that the equipment can pass the electromagnetic compatibility test, especially to pass the electromagnetic compatibility standards of RE102 and CE102 at the same time, it is necessary to use an EMI filter to effectively suppress interference from 10kHz to 1GHz. At present, most EMI filters are mainly aimed at electromagnetic interference from 10kHz to 10MHz, but the electromagnetic interference suppression from 10MHz to 1GHz is very small, and its suppression frequency band is narrow and cannot cover the demand. In some fields with harsh environments, such as aerospace, aviation and ships, EMI filters are required to have good sealing characteristics. Unsealed EMI filters will be penetrated by moisture when used in these fields, resulting in short circuits in the inductor, capacitor components and circuit boards in the EMI filter, thus failing to ensure the normal operation of the equipment.

[0004] The existing technology uses through-hole capacitor grounding to solve the high-frequency suppression problem, but the through-hole capacitor is difficult to weld, and the flux residue cannot be removed when placed in a sealed cavity. It will cause short circuit failure during long-term operation. If it is exposed to the air for a long time, the moisture in the air will penetrate into the through-hole capacitor, resulting in reduced insulation performance.

[0005] In addition, to ensure that the through-hole capacitor can effectively remove solder residues, the through-hole capacitor cannot be close to the printed circuit board and needs to be exposed to the air, so that the through-hole capacitor is in an unsealed state, and even all inductors and capacitors are exposed to the air. The inductors and capacitors in the Chinese patent (patent number ZL2004800117378) are placed in a plastic shell, causing the components to be completely exposed to the air. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a sealed structure anti-electromagnetic interference filter and a manufacturing method thereof, which can avoid short circuits in the inductor, capacitor elements and circuit boards in the EMI filter and ensure the normal operation of the equipment installed with the EMI filter.

[0007] The technical solution adopted by the present invention is: a sealed structure anti-electromagnetic interference filter, including a metal base plate, a metal shell and a metal cover plate, the metal base plate and the metal cover plate are respectively sealed and installed on the upper and lower ends of the metal shell, an annular boss is arranged in the metal base plate, a lower circuit board is installed on the annular boss, four annular magnetic cores are installed on the lower circuit board, an upper circuit board is installed on the upper ends of the four annular magnetic cores, four electrodes are passed through the four annular magnetic cores to form a through-core inductor, and the four electrodes are fixedly connected and electrically connected to the upper circuit board, two input electrodes of the four electrodes are suspended and passed through the lower circuit board, and the other two output electrodes are fixedly connected and electrically connected to the lower circuit board, after the lower ends of the four electrodes are extended, three electrodes are fixedly connected to the metal base plate through glass insulators, the fourth electrode is fixedly connected to the metal base plate and electrically connected to it as a grounding terminal, and the four electrodes all extend out of the metal base plate.

[0008] Furthermore, the metal shell is filled with potting glue.

[0009] Furthermore, the wall thickness of the glass insulator is not less than 1 mm. Furthermore, a chip capacitor 1 and a chip capacitor 2 are respectively disposed at the bottom of the lower circuit board and the bottom of the upper circuit board.

[0010] Furthermore, the upper circuit board is a multi-layer printed circuit board structure, and a second chip capacitor is connected across the input positive terminal and the input negative terminal of the connection pattern on the bottom surface of the upper circuit board, and the installation direction of the second chip capacitor is downward.

[0011] Furthermore, the above-mentioned lower circuit board is a single-sided board, and a chip capacitor 1 is connected across the output positive terminal and the output negative terminal of the connection pattern on the bottom surface of the lower circuit board. The installation direction of the chip capacitor 1 is downward and the distance from the bottom surface of the groove of the annular boss is not less than 0.5mm.

[0012] A method for manufacturing a sealed structure anti-electromagnetic interference filter, the method comprising the following steps: 1) Apply solder to the pad where the chip capacitor is placed on the lower circuit board, solder the chip capacitor by reflow soldering, and then clean it; 2) Apply solder to the pad where the second chip capacitor is placed on the upper circuit board, solder the second chip capacitor by reflow soldering, and clean it; 3) Insert the lower circuit board into the metal base plate with four electrodes through the through hole on the circuit board, attach the lower circuit board to the upper end surface of the annular boss of the metal base plate, and make the chip capacitor face downwards, weld the lower circuit board to two input electrodes of the four electrodes, and let the other two output electrodes pass through the lower circuit board in the air; 4) Insert the four annular magnetic cores from the upper ends of the four electrodes and place them against the lower circuit board; 5) Pass the upper circuit board through the through hole on the circuit board to the upper end of the four electrodes, so that the chip capacitor faces downward, and weld the four electrodes to the upper circuit board and clean them; 6) Install the metal shell on the metal bottom plate, and sew the connection between the metal shell and the metal bottom plate by laser to make the metal shell and the metal bottom plate become one, forming a cavity structure; 7) Fill the cavity with potting glue, completely fill the entire cavity and just cover the upper circuit board. Remove the air in the colloid through vacuum degassing. All components of the anti-electromagnetic interference filter are completely sealed in the potting glue.

[0013] 8) Cover the metal cover plate and the metal shell together and perform laser sealing welding to ensure that the cavity is a completely sealed structure. Beneficial effects of the present invention: Compared with the prior art, the present invention adopts metal sealing technology to completely seal the inductor and the capacitor in a sealed cavity, so that the filter has a metal sealing structure. The metal cavity formed by the metal shell and the metal bottom plate serves as the grounding terminal, ensuring that the circuit board capacitor shortens the distance from the capacitor to the grounding terminal through internal connection, and achieves a good suppression effect at 10MHz to 1GHz. Through the internal circuit board connection, the combination of the inductor and the capacitor is arranged in a vertical space, which not only reduces the spatial volume of the filter, but also can well avoid the capacitor from being short-circuited due to improper cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a front view structural diagram of the anti-electromagnetic interference filter; Figure 2 yes Figure 1 Schematic diagram of the AA section structure; Figure 3 yes Figure 1 Schematic diagram of the structure of the middle BB section; Figure 4 It is a schematic diagram of the structure of the anti-electromagnetic interference filter viewed from above; Figure 5 It is a left-view structural diagram of the anti-electromagnetic interference filter; Figure 6 yes Figure 5 Schematic diagram of the CC cross-section structure; Figure 7 yes Figure 5 Schematic diagram of the structure of the middle DD section; Figure 8 It is a three-dimensional structural diagram of an anti-electromagnetic interference filter; Fig. 9 It is a three-dimensional structural diagram of the anti-electromagnetic interference filter from another perspective; Fig.10 This is a schematic diagram of the connection between the upper and lower circuit boards of the anti-electromagnetic interference filter and the four electrodes; Fig.11 It is a schematic diagram of the three-dimensional structure of the upper circuit board; Fig.12 It is a schematic diagram of the three-dimensional structure of the lower circuit board; Fig.13 It is the circuit schematic diagram of the sealed structure anti-electromagnetic interference filter. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0016] Example 1: Figure 1-13 As shown, a sealed structure anti-electromagnetic interference filter, the anti-electromagnetic interference filter is an EMI filter of an LC structure circuit, and the specific circuit is as follows Fig.13 The specific structure includes a metal bottom plate 1, a metal shell 2 and a metal cover plate 3. The metal bottom plate 1 and the metal cover plate 3 are respectively sealed and installed on the upper and lower ends of the metal shell 2. An annular boss 4 is arranged in the metal bottom plate 1. A lower circuit board 5 is installed on the annular boss 4. Four annular magnetic cores 6 are installed on the lower circuit board 5. An upper circuit board 7 is installed on the upper ends of the four annular magnetic cores 6. Four electrodes 8 pass through the four annular magnetic cores 6 to form a through-core inductor, and the four electrodes 8 are fixedly connected and electrically connected to the upper circuit board 7. Two input electrodes of the four electrodes 8 are suspended and pass through the lower circuit board 5, and the other two output electrodes are fixedly connected and electrically connected to the lower circuit board 5. After the lower ends of the four electrodes 8 are extended, three electrodes 8 are fixedly connected to the metal bottom plate 1 through glass insulators 9. The fourth electrode 8 is fixedly connected to the metal bottom plate 1 and electrically connected to it as a grounding terminal. The four electrodes 8 all extend out of the metal bottom plate 1.

[0017] The metal shell 2 is filled with potting glue, and the potting glue is filled into the metal shell 2. The components and circuit boards in the metal shell 2 are covered by the potting glue, which can further effectively isolate the external moisture from penetrating into the inside. At the same time, the firmness of the potting glue after filling ensures that the filter is integrated inside and outside, thereby improving the shock resistance of the filter.

[0018] In order to allow the glass insulator to better play an insulating role, the wall thickness of the glass insulator 9 is not less than 1 mm, which can ensure effective physical isolation. In order to achieve a compact structure, a chip capacitor 1 10 and a chip capacitor 2 11 are respectively disposed at the bottom of the lower circuit board 5 and the bottom of the upper circuit board 7 .

[0019] The upper circuit board 7 is a multi-layer printed circuit board structure. A second chip capacitor 11 is connected across the input positive terminal and the input negative terminal of the bottom surface connection pattern of the upper circuit board 7. The installation direction of the second chip capacitor 11 faces downward.

[0020] The lower circuit board 5 is a single-sided board, and a chip capacitor 10 is connected across the output positive terminal and the output negative terminal of the bottom surface connection pattern of the lower circuit board 5. The installation direction of the chip capacitor 10 is downward and the distance from the bottom surface of the groove of the annular boss 4 is not less than 0.5mm to ensure that the chip capacitor 10 forms the shortest distance to the ground terminal.

[0021] The structure of the present invention comprises: a metal bottom plate 1, a metal shell 2, a metal cover plate 3, an upper circuit board 7, a lower circuit board 5, four annular magnetic cores 6 and two chip capacitors (chip capacitor one 10 and chip capacitor two 11).

[0022] Four electrodes (pins) are integrated on the metal bottom plate, and the four electrodes penetrate the metal bottom plate. The four electrodes are the input positive terminal, the input negative terminal, the output positive terminal, and the output negative terminal. The output negative terminal is also the ground terminal, which is connected to the metal bottom plate as a whole. The input positive terminal, the input negative terminal, and the output positive terminal are physically and electrically isolated from the metal bottom plate by glass insulators to ensure that the electrical distance between the three electrodes (pins) and the metal bottom plate is not less than 1mm.

[0023] A square convex structure is arranged on the top surface of the metal bottom plate, and a groove is opened in the middle to form an annular boss. The metal shell is a square structure, which is hollow and has stepped groove openings at the upper and lower ends. The metal bottom plate is an inverted square convex structure design, which is welded to the bottom of the metal shell to form a cavity structure design with a closed bottom.

[0024] Four electrodes (pins) penetrate the upper circuit board and the lower circuit board, and are conductively welded at corresponding positions (four pads on the upper circuit board and pads at two output electrodes on the lower circuit board) as needed by conventional welding techniques.

[0025] The upper circuit board and the lower circuit board are designed with conductive connection patterns according to the requirements of the electrical schematic diagram, and the input positive terminal and the output positive terminal are electrically connected through the pattern, and the input negative terminal and the output negative terminal are electrically connected. The upper circuit board and the lower circuit board are designed with through holes for the lead-out terminals to penetrate, and the pads around the through holes are designed with a disc structure, and the pad diameter is twice the diameter of the through hole to meet the welding requirements.

[0026] The upper circuit board is a multi-layer printed circuit board structure design, which can be designed as a 4-layer board or a 6-layer board according to the overcurrent requirements. The chip capacitor ears are connected across the two ends of the connection pattern on the bottom surface of the upper circuit board (between the positive input end and the negative input end), and the installation direction of the chip capacitor 2 is downward.

[0027] The lower circuit board is a single-sided board design. The bottom surface of the lower circuit board is designed with a connection pattern that connects to the output positive terminal and connects to the output negative terminal by mounting the chip capacitor 1 to ensure that the chip capacitor 1 forms the shortest distance to the ground terminal, and the installation direction of the chip capacitor 1 is downward, so that the chip capacitor 1 is in the groove opened in the metal bottom plate (the groove of the annular boss), and the distance from one side of the chip capacitor to the groove surface is ensured to be no less than 0.5mm.

[0028] The four electrodes (pins) are sleeved with an annular magnetic core, which is located between the upper circuit board and the lower circuit board. Each annular magnetic core is cylindrical with a through hole in the middle, and each electrode passes through the through hole of each corresponding through-core inductor.

[0029] Embodiment 2: A method for manufacturing a sealed structure anti-electromagnetic interference filter, the method comprising the following steps: 1) Apply solder to the pad where the chip capacitor is placed on the lower circuit board, solder the chip capacitor by reflow soldering, and then clean it; 2) Apply solder to the pad where the second chip capacitor is placed on the upper circuit board, solder the second chip capacitor by reflow soldering, and clean it; 3) Insert the lower circuit board into the metal base plate with four electrodes through the through hole on the circuit board, attach the lower circuit board to the upper end surface of the annular boss of the metal base plate, and make the chip capacitor face downwards, weld the lower circuit board to two input electrodes of the four electrodes, and let the other two output electrodes pass through the lower circuit board in the air; 4) Insert the four annular magnetic cores from the upper ends of the four electrodes and place them against the lower circuit board; 5) Pass the upper circuit board through the through hole on the circuit board to the upper end of the four electrodes, so that the chip capacitor faces downward, and weld the four electrodes to the upper circuit board and clean them; 6) Install the metal shell on the metal bottom plate, and sew the connection between the metal shell and the metal bottom plate by laser to make the metal shell and the metal bottom plate become one, forming a cavity structure; 7) Fill the cavity with potting glue, completely fill the entire cavity and just cover the upper circuit board. Remove the air in the colloid through vacuum degassing. All components of the anti-electromagnetic interference filter are completely sealed in the potting glue.

[0030] 8) Cover the metal cover plate and the metal shell together and perform laser sealing welding to ensure that the cavity is a completely sealed structure. The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A sealed structure anti-electromagnetic interference filter, characterized in that: The invention comprises a metal bottom plate (1), a metal shell (2) and a metal cover plate (3), wherein the metal bottom plate (1) and the metal cover plate (3) are respectively sealed and mounted on the upper and lower ends of the metal shell (2), an annular boss (4) is arranged inside the metal bottom plate (1), a lower circuit board (5) is mounted on the annular boss (4), four annular magnetic cores (6) are mounted on the lower circuit board (5), an upper circuit board (7) is mounted on the upper ends of the four annular magnetic cores (6), the four annular magnetic cores (6) pass through four electrodes (8) to form a through-core inductor, and four The four electrodes (8) are fixedly connected and electrically connected to the upper circuit board (7); two input electrodes among the four electrodes (8) are suspended and pass through the lower circuit board (5); the other two output electrodes are fixedly connected and electrically connected to the lower circuit board (5); after the lower ends of the four electrodes (8) are extended, three electrodes (8) are fixedly connected to the metal bottom plate (1) through glass insulators (9); the fourth electrode (8) is fixedly connected to the metal bottom plate (1) and remains electrically connected thereto as a grounding terminal; and the four electrodes (8) all extend out of the metal bottom plate (1).

2. The sealed structure anti-electromagnetic interference filter according to claim 1, characterized in that: The metal shell (2) is filled with potting glue.

3. The sealed structure anti-electromagnetic interference filter according to claim 1, characterized in that: The wall thickness of the glass insulator (9) is not less than 1 mm.

4. The sealed structure anti-electromagnetic interference filter according to claim 1, characterized in that: A chip capacitor 1 (10) and a chip capacitor 2 (11) are respectively arranged at the bottom of the lower circuit board (5) and the bottom of the upper circuit board (7).

5. The sealed structure anti-electromagnetic interference filter according to claim 4, characterized in that: The upper circuit board (7) is a multi-layer printed circuit board structure. A second chip capacitor (11) is connected across the input positive terminal and the input negative terminal of the bottom surface connection pattern of the upper circuit board (7). The installation direction of the second chip capacitor (11) faces downward.

6. The sealed structure anti-electromagnetic interference filter according to claim 4, characterized in that: The lower circuit board (5) is a single-sided board. A chip capacitor (10) is connected across the output positive terminal and the output negative terminal of the bottom surface connection pattern of the lower circuit board (5). The chip capacitor (10) is installed downward and the distance from the bottom surface of the groove of the annular boss (4) is not less than 0.5 mm.

7. The method for manufacturing a sealed structure anti-electromagnetic interference filter according to claim 1, characterized in that: The method comprises the following steps: 1) Apply solder to the pad where the chip capacitor is placed on the lower circuit board, solder the chip capacitor by reflow soldering, and then clean it; 2) Apply solder to the pads where the chip capacitor 2 is placed on the upper circuit board, solder the chip capacitor 2 by reflow soldering, and clean it; 3) Insert the lower circuit board into the metal base plate with four electrodes through the through hole on the circuit board, attach the lower circuit board to the upper end surface of the annular boss of the metal base plate, and make the chip capacitor face downward, weld the lower circuit board to two input electrodes of the four electrodes, and let the other two output electrodes pass through the lower circuit board in the air; 4) Insert four annular magnetic cores from the upper ends of the four electrodes and place them against the lower circuit board; 5) Pass the upper circuit board through the through hole on the circuit board to the upper end of the four electrodes, so that the chip capacitor faces downward, and weld the four electrodes to the upper circuit board and clean them; 6) Install the metal shell on the metal bottom plate, and sew the connection between the metal shell and the metal bottom plate by laser so that the metal shell and the metal bottom plate become one, thereby forming a cavity structure; 7) Fill the cavity with potting glue, completely fill the entire cavity and just submerge the upper circuit board, remove the air in the colloid through vacuum degassing, and the components of the anti-electromagnetic interference filter are completely sealed in the potting glue. 8) Cover the metal cover plate and the metal shell and seal them by laser welding to ensure that the cavity is a completely sealed structure.

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