Printed circuit board for suppressing electromagnetic interference

Abstract

The invention relates to a printed circuit board for suppressing electromagnetic interference, belongs to the field of printed circuit boards, and aims to solve the problems that assembly is difficult and labor-consuming, large friction force needs to be overcome during installation in interference fit, an operator needs to apply enough pressure to press or clamp a shielding cover in place, and assembly working hours and labor intensity are increased. A printed circuit board for suppressing electromagnetic interference comprises a printed circuit board main body, an electronic element connected above the middle of the printed circuit board main body, a first shielding plate arranged on the outer side of the electronic element and fixedly connected with the printed circuit board main body, and a second shielding plate arranged above the first shielding plate, uniform pressure is applied to the whole second shielding plate through atmospheric pressure, so that the second conductive rubber is uniformly compressed to realize sealing, and in-place prompt is provided in combination with a thread structure, so that the installation difficulty of traditional interference fit is avoided, the labor intensity is reduced, and the sealing quality and the accuracy of an installation position are ensured.

Description

Technical Field

[0001] This invention relates to the field of printed circuit boards, and particularly to a printed circuit board for suppressing electromagnetic interference. Background Technology

[0002] Patent CN112911918B discloses a printed circuit board for suppressing electromagnetic interference. This printed circuit board improves the shielding effect of an electromagnetic shielding cover. It includes a circuit board body and a shielding device disposed on the circuit board body for shielding electronic components. The shielding device includes a rectangular frame that inserts into the circuit board body and a shielding cover that engages with and is electrically connected to the rectangular frame. The rectangular frame includes a pair of parallel long frame strips and a pair of parallel short frame strips. Several fixing rods perpendicular to the long frame strips are evenly spaced at the bottom of the two long frame strips. The circuit board body has pre-drilled holes for the fixing rods to pass through. This application improves the shielding effect on electronic components through the use of a shielding plate.

[0003] In modern electronic devices, the integration density and operating frequency of printed circuit boards (PCBs) continue to rise, making electromagnetic interference (EMI) a key factor restricting device performance and reliability. To effectively suppress EMI, the industry widely adopts shielding measures, which isolate interference sources from sensitive components by constructing metal shielding structures in specific areas of the PCB.

[0004] A mainstream shielding structure design involves placing a shielding plate at the bottom of the PCB, erecting shielding plates (usually called shielding frames) around the electronic components that need shielding on the PCB, and finally installing a shielding plate (usually called a shielding cover) on top of the electronic components. This "top-bottom-all-around" fully enclosed structure can form a complete Faraday cage, thereby effectively confining internal electromagnetic radiation and isolating external electromagnetic interference.

[0005] However, in order to facilitate subsequent maintenance, debugging or replacement of electronic components inside the shielded cavity, the upper shielding cover is usually not permanently fixed to the surrounding shielding frame (e.g., by soldering).

[0006] In existing technologies, one of the mainstream methods to achieve this detachable connection is to use an interference fit. That is, the size of the shielding cover is designed to be slightly larger than the internal size of the shielding frame, or protrusions, snaps, or other structures are set on the edge of the shielding cover so that it can be tightly locked onto the shielding frame by the pressure generated by elastic deformation during assembly.

[0007] While interference fits offer a degree of connection reliability, they also present several drawbacks in practical applications: First, assembly is difficult and labor-intensive. Installation requires overcoming significant friction, demanding operators apply sufficient pressure to press or snap the shielding cover into place, increasing assembly time and labor intensity. Second, accurate installation is difficult to determine. The lack of a clear positioning and feedback mechanism makes it hard for operators to accurately judge whether the shielding cover is fully and correctly installed, potentially leading to insecure installation and affecting shielding effectiveness. Finally, repeated disassembly and reassembly can cause fit failure. During the equipment's lifespan, maintenance and debugging may require multiple disassembly and reassembly of the shielding cover, each causing friction and wear on the interference fit's contact surfaces. With repeated disassembly and reassembly, wear intensifies, potentially increasing the fit clearance, eliminating the interference fit, and ultimately rendering the shielding cover unreliable, leading to decreased shielding performance or even complete failure.

[0008] To address the aforementioned problems, a printed circuit board for suppressing electromagnetic interference is proposed. Summary of the Invention

[0009] The purpose of this invention is to provide a printed circuit board that suppresses electromagnetic interference, solving the problems of difficult and laborious assembly, interference fit requiring overcoming large frictional forces during installation, and operators needing to apply sufficient pressure to press or snap the shielding cover into place, which increases assembly time and labor intensity.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a printed circuit board for suppressing electromagnetic interference, comprising a printed circuit board body, an electronic component connected to the upper middle part of the printed circuit board body, a first shielding plate fixedly connected to the printed circuit board body and disposed outside the electronic component, a second shielding plate disposed above the first shielding plate, a third shielding plate fixedly connected to the lower end of the printed circuit board body, a first conductive rubber disposed on the inner wall of the first shielding plate, a polytetrafluoroethylene coating on the outer surface of the first conductive rubber, a pull plate disposed on the inner side of the first conductive rubber, an air vent disposed inside the first shielding plate, a pulling mechanism disposed above the pull plate, and a rotating mechanism disposed below the pull plate;

[0011] The pulling mechanism includes a centering component and a sliding component, with the centering component located inside the centering component.

[0012] Preferably, the centering component includes a first rack fixedly connected to the upper center of the pull plate, a gear meshing with the outer side of the first rack, a rotating shaft fixedly connected inside the gear, the length of the rotating shaft being greater than the width of the first shielding plate, telescopic rods fixedly connected to the second shielding plate being rotatably connected to both ends of the rotating shaft, a second rack being provided on the other side of the gear, the central axis of the first rack being parallel to the central axis of the second rack, a counterweight being fixedly connected to the lower end of the second rack, a hanging plate being fixedly connected to the upper end of the first rack, a first groove being provided on the lower surface of the hanging plate, a second conductive rubber being fixedly connected to the upper end of the second shielding plate, a screw being threadedly connected to the lower outer end of the second shielding plate, and a threaded groove for threaded connection of the screw being provided on the lower outer side of the first shielding plate.

[0013] Preferably, the central axis of the first rack is parallel to the central axis of the second rack.

[0014] Preferably, the sliding assembly includes a fixed rod fixedly connected to the lower center of the second shielding plate, the fixed rod having a second groove inside, first holes on both sides of the second groove, a baffle on the inner side of the second groove, and a pull rod fixedly connected to the lower end of the baffle and fixedly connected to the second rack.

[0015] Preferably, the central axis of the second groove is collinear with the central axis of the second rack.

[0016] Preferably, the upper width of the second groove is greater than the lower width of the second groove, and the upper inner side of the second groove is in contact with the outer side of the baffle, and the baffle is in contact with the outer side of the first hole.

[0017] Preferably, both the baffle and the pull rod have a cuboid shape.

[0018] Preferably, the rotating mechanism includes a sleeve fixedly connected to the lower end of the pull plate. The lower end of the sleeve has a second hole. A guide groove is provided on the inner side wall of the sleeve. A support rod is provided inside the sleeve. A guide rod is fixedly connected to the support rod inside the guide groove. A rotating rod nested inside the second hole is fixedly connected to the lower end of the support rod. A fan blade is fixedly connected to the lower end of the rotating rod. The fan blade is made of stainless steel. A first support plate is rotatably connected to the lower end of the fan blade. A second support plate is fixedly connected to the second shielding plate below the first support plate.

[0019] Preferably, the guide groove has a spiral shape, and the guide groove and the guide rod are fitted with a clearance fit.

[0020] Preferably, the inner side of the sleeve fits against the outer side of the support rod, and the support rod has a cylindrical shape. The outer side of the rotating rod fits against the inner side of the second hole, and the rotating rod has a cylindrical shape. Furthermore, the central axis of the rotating rod is collinear with the central axis of the sleeve.

[0021] Preferably, the weight of the counterweight is greater than the sum of the weights of the first rack, the hanging plate, the pull plate, the first conductive rubber, and the sleeve.

[0022] 1. Compared with the prior art, the beneficial effects of the present invention are: by applying uniform pressure to the second shielding plate as a whole through atmospheric pressure, the second conductive rubber is uniformly compressed to achieve sealing, and the threaded structure provides positioning indication, thereby avoiding the installation difficulties of traditional interference fit, reducing labor intensity, and ensuring sealing quality and installation position accuracy.

[0023] 2. This invention utilizes the inertial motion of components such as counterweights to drive gas flow within a cavity in a vibrating environment, generating a force that counteracts the inertial displacement of electronic components. This effectively reduces printed circuit board cracks and poor component contact caused by vibration, thereby improving the reliability and service life of the equipment.

[0024] 3. This invention accelerates the transfer and dissipation of heat generated by electronic components to the shielding plate by causing gas to circulate within the shielding chamber under the drive of vibration and air pressure changes, thereby improving the heat dissipation efficiency of the system.

[0025] 4. This invention transforms the potentially instantaneous high-pressure airflow into a downward rotating flow field by using rotating fan blades, thereby dispersing the impact force and preventing the high-pressure airflow from concentrating on a single fragile electronic component, thus reducing the potential risk of damage.

[0026] 5. By using stainless steel fan blades, the present invention can make more full contact with electromagnetic waves and absorb their energy during rotation, thereby dynamically enhancing the electromagnetic interference suppression effect of the entire shielding system while dissipating heat. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the front cross-sectional structure of the pull plate of the present invention;

[0029] Figure 3 This is a schematic diagram of the front cross-sectional structure of the first rack of the present invention;

[0030] Figure 4 For the present invention Figure 3 Schematic diagram of the structure at point A in the middle;

[0031] Figure 5 For the present invention Figure 3 Schematic diagram of the structure at point B;

[0032] Figure 6 For the present invention Figure 3 Schematic diagram of the structure at point C;

[0033] Figure 7 This is a top view of the pull plate structure of the present invention;

[0034] Figure 8 This is a top view of the fan blade structure of the present invention.

[0035] In the diagram: 1. Printed circuit board body; 2. Electronic components; 3. First shielding plate; 4. Second shielding plate; 5. Third shielding plate; 6. First conductive rubber; 7. Polytetrafluoroethylene coating; 8. Pulling plate; 9. Pulling mechanism; 10. Rotating mechanism; 11. Vent hole; 91. Centering assembly; 92. Sliding assembly; 911. First rack; 912. Gear; 913. Rotating shaft; 914. Telescopic rod; 915. Second rack; 917. Counterweight; 918. Hanging plate; 919. First groove; 9110, second conductive rubber; 9111, screw; 9112, threaded groove; 921, fixing rod; 922, second groove; 923, first hole; 924, baffle; 925, pull rod; 101, sleeve; 102, second hole; 103, guide groove; 104, support rod; 105, guide rod; 106, rotating rod; 107, fan blade; 108, first support plate; 109, second support plate; 13, first air chamber; 12, second air chamber. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Please see Figures 1-8 The present invention provides a technical solution: a printed circuit board for suppressing electromagnetic interference, comprising a printed circuit board body 1, an electronic component 2 connected to the upper middle part of the printed circuit board body 1, a first shielding plate 3 fixedly connected to the printed circuit board body 1 on the outside of the electronic component 2, a second shielding plate 4 fixedly connected above the first shielding plate 3, a third shielding plate 5 fixedly connected to the lower end of the printed circuit board body 1, a first conductive rubber 6 provided on the inner wall of the first shielding plate 3, a polytetrafluoroethylene coating 7 coated on the outer surface of the first conductive rubber 6, a pull plate 8 provided on the inner side of the first conductive rubber 6, an air vent 11 provided inside the first shielding plate 3, a pulling mechanism 9 provided above the pull plate 8, and a rotating mechanism 10 provided below the pull plate 8;

[0038] The pulling mechanism 9 includes a centering component 91 and a sliding component 92, with the centering component 91 disposed inside the centering component 91.

[0039] The centering component 91 includes a first rack 911 fixedly connected to the upper middle of the pull plate 8. A gear 912 is meshed with the outer side of the first rack 911. A rotating shaft 913 is fixedly connected inside the gear 912. The length of the rotating shaft 913 is greater than the width of the first shielding plate 3. Telescopic rods 914, which are fixedly connected to the second shielding plate 4, are rotatably connected to both ends of the rotating shaft 913. A second rack 915 is provided on the other side of the gear 912. A counterweight 917 is fixedly connected to the lower end of the second rack 915. A hanging plate 918 is fixedly connected to the upper end of the first rack 911. A first groove 919 is provided on the lower surface of the hanging plate 918. A second conductive rubber 9110 is fixedly connected to the upper end of the second shielding plate 4. A screw 9111 is threadedly connected to the lower outer end of the second shielding plate 4. A threaded groove 9112 for threaded connection of the screw 9111 is provided on the lower outer side of the first shielding plate 3. The central axis of the first rack 911 is parallel to the central axis of the second rack 915.

[0040] The sliding assembly 92 includes a fixed rod 921 fixedly connected to the lower middle part of the second shielding plate 4. The fixed rod 921 has a second groove 922 inside. The second groove 922 has first holes 923 on both sides. A baffle 924 is provided on the inner side of the second groove 922. A pull rod 925 fixedly connected to the lower end of the baffle 924 is fixedly connected to the second rack 915. The central axis of the second groove 922 is collinear with the central axis of the second rack 915. The upper width of the second groove 922 is greater than the lower width of the second groove 922. The inner side of the upper end of the second groove 922 is in contact with the outer side of the baffle 924. The baffle 924 is in contact with the outer side of the first hole 923. The external structural shape of the baffle 924 and the pull rod 925 is cuboid, so that the baffle 924 and the pull rod 925 will not rotate when they move up and down.

[0041] The rotating mechanism 10 includes a sleeve 101 fixedly connected to the lower end of the pull plate 8. A second hole 102 is provided at the lower end of the sleeve 101. A guide groove 103 is provided on the inner wall of the sleeve 101. A support rod 104 is provided inside the sleeve 101. A guide rod 105 is fixedly connected to the support rod 104 inside the guide groove 103. A rotating rod 106 nested inside the second hole 102 is fixedly connected to the lower end of the support rod 104. A fan blade 107 is fixedly connected to the lower end of the rotating rod 106. The blade of the fan blade 107 is made of stainless steel. A first support plate 108 is rotatably connected to the lower end of the fan blade 107. A second support plate 109 fixedly connected to the second shielding plate 4 is provided below the first support plate 108. The guide groove 10... The external structure of 3 is spiral, and the guide groove 103 and guide rod 105 are fitted with clearance. The guide rod 105 will not rotate when it moves inside the guide groove 103. The inner side of the sleeve 101 is in contact with the outer side of the support rod 104, and the external structure of the support rod 104 is cylindrical. The outer side of the rotating rod 106 is in contact with the inner side of the second hole 102, and the external structure of the rotating rod 106 is cylindrical. The central axis of the rotating rod 106 is collinear with the central axis of the sleeve 101, so that the rotating rod 106 will not wobble when it rotates inside the second hole 102. The weight of the counterweight 917 is greater than the sum of the weights of the first rack 911, the hanging plate 918, the pull plate 8, the first conductive rubber 6, and the sleeve 101.

[0042] When the second shielding plate 4 needs to be installed during maintenance or testing, the first conductive rubber 6 and the pull plate 8 are placed inside the first shielding plate 3. At this time, the second shielding plate 4 does not seal the top of the first shielding plate 3, allowing the first conductive rubber 6 and the pull plate 8 to push the gas above the lower end of the vent 11 of the second shielding plate 4 out through the vent 11 to the top of the pull plate 8 and then discharge it. This positions the first conductive rubber 6 and the pull plate 8 below the lower end of the vent 11. The second shielding plate 4 is then moved downwards until it fits over the outside of the first shielding plate 3. When the second shielding plate 4 is fitted over the first shielding plate 3, after the rotating shaft 913 contacts the upper surface of the first shielding plate 3, the rotating shaft 913 stops moving downwards. However, the second rack 915 and the counterweight 917 continue to move downwards due to gravity, causing the gear 912 to rotate. This rotates the first rack 911, the first conductive rubber 6, and the pull plate 8 upwards. Since the second shielding plate 4 has blocked the upper end of the first shielding plate 3, When the first conductive rubber 6 and the pull plate 8 move upward, the space of the first air pressure chamber 13 below the first conductive rubber 6 and the pull plate 8 increases. The air inside the second air pressure chamber 12 above the first conductive rubber 6 and the pull plate 8 moves downward, causing the air pressure inside the second air pressure chamber 12 to decrease. The atmospheric pressure above the second shielding plate 4 pushes the second shielding plate 4 downward, compressing and sealing the second conductive rubber 9110. When the second conductive rubber 9110 can no longer be compressed, the screw 9111 moves to the position of the threaded groove 9112, and is manually tightened to fix the second shielding plate 4. This installation process does not require an interference fit, avoiding the situation where the operator needs to apply sufficient pressure to press or snap the shielding cover into place, which increases assembly time and labor intensity. The interference fit and the engagement of the threaded groove 9112 can indicate to the assembly personnel whether the installation is in place, and fixing the second shielding plate 4 does not require a large amount of friction as a fixing condition, making the installation more convenient.

[0043] Because the present invention uses atmospheric pressure to push the second shielding plate 4 to compress the second conductive rubber 9110 during installation, the entire upper part of the second shielding plate 4 is pressurized, making the second conductive rubber 9110 more uniformly pressed. This avoids the uneven force caused by manual pressing or the use of heavy objects, which could lead to the second shielding plate 4 warping during installation, resulting in greater friction when the second shielding plate 4 covers the outside of the first shielding plate 3, making installation inconvenient.

[0044] Because printed circuit boards (PCBs) are used as control components, they are often installed in environments with vibration, such as above vehicles. When vibration occurs, energy is transferred through the PCB body 1 to the second shielding plate 4, the fixing rod 921, and the baffle 924. This causes the baffle 924, the second rack 915, and the counterweight 917 to move upwards due to inertia. Since the weight of the counterweight 917 is greater than the sum of the weights of the first rack 911, the hanging plate 918, the pull plate 8, the first conductive rubber 6, the pull plate 8, and the sleeve 101, the upper end of the telescopic rod 914 abuts against the inner side of its fixed end. This causes the first rack 911 to move downwards, pushing the gas in the first pressure chamber 13 downwards and causing the gas to move towards the guide hole 11 and the inner side of the second pressure chamber 12. Because the area covered by the second shielding plate 4 contains a large number of electronic components 2, during vibration... During the operation, electronic component 2 will also move upward due to inertia. At this time, the gas in the first pressure chamber 13 moves downward, and the air pressure inside the first pressure chamber 13 increases. Although some gas will move from the air guide hole 11 to the inside of the second pressure chamber 12, the diameter of the air guide hole 11 cannot discharge a large amount of gas at the same time, and the vibration process is relatively fast. Most of the gas will push the electronic component 2, which moves upward due to inertia, and the printed circuit board body 1 downward, reducing the cracks caused by the inertial movement of electronic component 2 in the printed circuit board body 1 and the poor contact caused by electronic component 2 detaching from the printed circuit board body 1. This improves the service life of the printed circuit board body 1 and reduces the occurrence of poor contact of electronic component 2. At the same time, the flow of gas will cause the electronic component 2 to move to the first shielding plate 3 and the second shielding plate 4, which are filled with heat in the air, to accelerate heat exchange and improve heat dissipation efficiency.

[0045] During the upward movement of the sleeve 101, the fan blade 107, rotating rod 106, and first support rod 104 will not move upward due to gravity. This causes relative movement between the guide groove 103 and the guide rod 105, resulting in rotation between the fan blade 107, rotating rod 106, and first support rod 104. This rotation drives the gas to diffuse in all directions. The flow of gas causes the electronic components 2 to move towards the first shielding plate 3 and the second shielding plate 4, which carry heat, thus accelerating heat exchange and improving heat dissipation efficiency.

[0046] At the same time, the air pressure inside the first pressure chamber 13 increases, and the air pressure gas on the fan blade 107 diffuses to all sides. The increase in air pressure is instantaneous, and the sudden high pressure impact may directly affect the relatively fragile electronic components 2 and damage them. The downward airflow and the rotating airflow interact to form a rotating downward airflow, so that the airflow does not act on a single point, but can move to one side after acting, reducing damage.

[0047] Because the blades of fan 107 are made of stainless steel, stainless steel can absorb electromagnetic waves, allowing the fan 107 to come into more full contact with electromagnetic waves during rotation, thus improving the efficiency of the fan 107 in absorbing electromagnetic waves and further enhancing the effect of suppressing electromagnetic interference.

[0048] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A printed circuit board for suppressing electromagnetic interference, comprising a printed circuit board body (1), an electronic component (2) connected to the upper middle part of the printed circuit board body (1), a first shielding plate (3) disposed outside the electronic component (2) and fixedly connected to the printed circuit board body (1), a second shielding plate (4) disposed above the first shielding plate (3), and a third shielding plate (5) fixedly connected to the lower end of the printed circuit board body (1), characterized in that: The inner wall of the first shielding plate (3) is provided with a first conductive rubber (6), the outer surface of the first conductive rubber (6) is coated with a polytetrafluoroethylene coating (7), the inner side of the first conductive rubber (6) is provided with a pull plate (8), the interior of the first shielding plate (3) is provided with a vent hole (11), and a pulling mechanism (9) is provided above the pull plate (8). The pulling mechanism (9) is used to automatically lift the pull plate (8) by gravity transmission during the installation of the second shielding plate (4) to form a negative pressure in the shielding cavity, assisting the second shielding plate (4) to complete the sealing and pressing under atmospheric pressure; and when the equipment vibrates, the pull plate (8) is driven to reciprocate by the inertia of the counterweight to suppress the inertial vibration of the electronic components (2) and promote the internal airflow circulation to enhance heat dissipation. A rotating mechanism (10) is provided below the pull plate (8). The rotating mechanism (10) is used to convert the linear motion of the pull plate (8) into the rotational motion of the fan blade (107). By stirring the air in the shielding cavity, the airflow is evenly distributed and heat dissipation is enhanced. At the same time, the stainless steel fan blade (107) absorbs electromagnetic interference. The pulling mechanism (9) includes a centering component (91) and a sliding component (92), wherein the sliding component (92) is disposed inside the centering component (91).

2. The printed circuit board for suppressing electromagnetic interference according to claim 1, characterized in that: The centering assembly (91) includes a first rack (911) fixedly connected above the middle of the pull plate (8). A gear (912) is meshed with the outer side of the first rack (911). A rotating shaft (913) is fixedly connected inside the gear (912). The length of the rotating shaft (913) is greater than the width of the first shielding plate (3). Telescopic rods (914) fixedly connected to the second shielding plate (4) are rotatably connected to both ends of the rotating shaft (913). A second rack (915) is provided on the other side of the gear (912). The central axis of the first rack (911) is... Parallel to the central axis of the second rack (915), the lower end of the second rack (915) is fixedly connected to a counterweight (917), the upper end of the first rack (911) is fixedly connected to a hanging plate (918), the lower surface of the hanging plate (918) is provided with a first groove (919), the upper end of the second shielding plate (4) is fixedly connected to a second conductive rubber (9110), the lower outer end of the second shielding plate (4) is threadedly connected to a screw (9111), and the lower outer side of the first shielding plate (3) is provided with a threaded groove (9112) for threaded connection of the screw (9111).

3. A printed circuit board for suppressing electromagnetic interference according to claim 1, characterized in that: The sliding assembly (92) includes a fixed rod (921) fixedly connected to the lower middle of the second shielding plate (4). The fixed rod (921) has a second groove (922) inside. The second groove (922) has first holes (923) on both sides. The second groove (922) has a baffle (924) on the inner side. The lower end of the baffle (924) is fixedly connected to a pull rod (925) fixedly connected to the second rack (915).

4. A printed circuit board for suppressing electromagnetic interference according to claim 3, characterized in that: The central axis of the second groove (922) is collinear with the central axis of the second rack (915).

5. A printed circuit board for suppressing electromagnetic interference according to claim 3, characterized in that: The upper width of the second groove (922) is greater than the lower width of the second groove (922), and the upper inner side of the second groove (922) is in contact with the outer side of the baffle (924), and the baffle (924) is in contact with the outer side of the first hole (923).

6. A printed circuit board for suppressing electromagnetic interference according to claim 3, characterized in that: Both the baffle (924) and the pull rod (925) have a rectangular shape.

7. A printed circuit board for suppressing electromagnetic interference according to claim 1, characterized in that: The rotating mechanism (10) includes a sleeve (101) fixedly connected to the lower end of the pull plate (8). The lower end of the sleeve (101) is provided with a second hole (102). A guide groove (103) is provided on the inner side wall of the sleeve (101). A support rod (104) is provided on the inner side of the sleeve (101). A guide rod (105) fixedly connected to the support rod (104) is provided on the inner side of the guide groove (103). A rotating rod (106) nested inside the second hole (102) is fixedly connected to the lower end of the support rod (104). A fan blade (107) is fixedly connected to the lower end of the rotating rod (106). The blade of the fan blade (107) is made of stainless steel. A first support plate (108) is rotatably connected to the lower end of the fan blade (107). A second support plate (109) fixedly connected to the second shielding plate (4) is provided below the first support plate (108).

8. A printed circuit board for suppressing electromagnetic interference according to claim 7, characterized in that: The guide groove (103) has a spiral shape, and the guide groove (103) and the guide rod (105) are fitted with a clearance fit.

9. A printed circuit board for suppressing electromagnetic interference according to claim 7, characterized in that: The inner side of the sleeve (101) is in contact with the outer side of the support rod (104), and the support rod (104) has a cylindrical shape. The outer side of the rotating rod (106) is in contact with the inner side of the second hole (102), and the rotating rod (106) has a cylindrical shape. The central axis of the rotating rod (106) is collinear with the central axis of the sleeve (101).

10. A printed circuit board for suppressing electromagnetic interference according to claim 7, characterized in that: The weight of the counterweight (917) is greater than the sum of the weights of the first rack (911), the hanging plate (918), the pull plate (8), the first conductive rubber (6), and the sleeve (101).

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