JPH0559898U - Printed circuit board front panel with electromagnetic wave leakage prevention structure - Google Patents

Abstract

(57) [Abstract] [Purpose] A printed circuit board is inserted from above into a housing in which one bottom surface and four side surfaces continuous with this are surrounded by a metal plate and housed at regular intervals so that the top surface is covered with a front panel. In some electronic devices, the front panel has folding legs on both sides, and an elastic shield plate is interposed for electrical connection between the legs. If both sides have legs, the lead legs of the element may come into contact with the legs of the front panel, and the disadvantage that the element cannot be mounted at a portion hitting above the printed circuit board is solved. [Structure] The front panel has an L-shaped cross-section instead of a U-shape. Since one side is open, it does not interfere with the lead of the element. Further, the shield plate is fixed to the front panel by using a shield plate holding metal fitting having a different shape depending on the printed circuit board.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electromagnetic wave leakage prevention structure for a printed circuit board front panel that is inserted and housed in a housing of an electronic device. A printed circuit board is an electronic circuit element such as an IC, an LSI, a capacitor, a coil, or a resistor mounted on a pattern on a board such as an epoxy resin. A large number of printed circuit boards are arranged in parallel and stored in a housing. The housing is a metallic container having a bottom surface and four surfaces following the bottom surface. It has a connector part for circuit connection on the upper front panel part. There are many printed circuit boards, and high-frequency current or large pulse current may flow in the pattern of the circuit board. For this reason, unexpected noise may be applied to external electronic devices. Therefore, it is necessary to enclose the entire casing with metal to prevent electromagnetic wave leakage. All you have to do is enclose the whole thing in one piece of metal and ground it, but since the printed circuit boards are attached to each front panel and can be taken out or replaced one by one, if you cover the whole with a metal plate It becomes inconvenient to take in and out the board. Therefore, the front panels are electrically connected to each other and are grounded.

[0002]

[Prior Art]

 Due to the voluntary regulation of VCCI that began in 1986, each company's unique electromagnetic wave leakage prevention structure can be seen in the printed circuit board front panel. The front panel that holds the printed circuit board is a thin plate that is long in the longitudinal direction, but it must be electrically connected to each other. FIG. 6 is a diagram showing a conventional example. The front panel 10 is a metal plate having a U-shaped cross section. Since electrical contact cannot be made as it is, elastic metal shield plates 11 are attached to both outer sides of the legs of the front panel 10. FIG. 7 shows a perspective view of only the shield plate 11. It is a chevron-shaped piece of metal that has claw pieces to be folded. Holes for inserting the claw pieces of the shield plate 11 are formed in the legs on both sides of the front panel 10. Insert a claw piece into this hole and bend the tip to join the shield plate 11 to the front panel 10. When the front panel 10 is housed in the housing, the shield plates 11 on both sides of the front panel 10 come into contact with the shield plates 11 of the adjacent front panels 10 at the mountain portions. Appropriate pressure is exerted on the shield plates due to their elastic forces, and they are connected to each other with low contact resistance.

FIG. 8 shows another conventional example. An elastic shield plate 13 is fixed to one side of the front panel 12 having a U-shaped cross section. The shield plate 13 as shown in FIG. 9 is fixed to the lower edge of the front panel 12 at the folded-back portion at the lower end. It has three elastic pieces separated by two notches from above. The elastic piece in the center is almost upright, and the elastic pieces on the left and right are bent slightly backward. And both tips are bent forward. When the front panel 1 is housed in the housing, the center piece of the shield plate 13 presses the attached front panel 12 as shown in FIG. The left and right two pieces elastically press the adjacent front panel 13. Due to this elastic force, electrical conduction is established between adjacent front panels. Compared with the one shown in FIG. 6, there is an advantage that less shield plate is required. There is also a shield plate that does not electrically connect the front panels. In this case, it is necessary to further cover the front panel with a metal lid. If so, the whole becomes bulky, which is not desirable. After all, we would like to connect the front panels to each other and ground them to prevent the leakage of electromagnetic waves.

[0004]

[Problems to be solved by the device]

 In the conventional case, the front panel has legs on both sides, and electrical conduction has been achieved between the legs between adjacent front panels. Therefore, both legs were indispensable for the front panel. The conventional one with geometrical symmetry seems to have an excellent point in that the distribution of elastic force is equalized in terms of dynamics. However, the long hanging legs make it difficult to design the circuit inside the printed circuit board. The legs get in the way. The printed circuit board is sandwiched between both legs. In this sandwiched region, if a device with a long lead leg is attached, the lead leg will contact the leg of the front panel on the back side. Therefore, the present inventor considers that there is a hidden defect that the device can be mounted only in the area below the leg portion of the front panel. In recent years, the mounting density of electronic circuits has become higher and higher, and various devices are often mounted. Therefore, it is not desirable that the degree of freedom in circuit design is limited even though it is only on the upper side of the printed circuit board. An object of the present invention is to provide an electromagnetic wave leakage prevention structure for a front panel, which has a high degree of freedom in design and allows any element to be mounted up to the upper side of a printed circuit board.

[0005]

[Means for Solving the Problems]

 In the printed circuit board front panel of the electromagnetic wave leakage prevention structure of the present invention, the front panel does not have legs on both sides, and has legs on only one side. In other words, the front panel is bent only on one side to form the legs, but the other side is not bent and is open. The reason for opening is to prevent the lead foot of the device from hitting. The cross-sectional shape is L-shaped, not U-shaped. A number of shield plates are fixed to the open side by a shield plate retainer with an L-shaped cross section. The shield plate retainer is lower than the leg side of the front panel. Also, the shape of the shield plate holder is different for each printed circuit board, and the parts that are not necessary to hold the shield plate are cut out low. Originally, the shield plate holder is low and the part without the shield plate is notched, so it does not interfere with the lead leg of the element mounted on the printed circuit board.

[0006]

[Action]

 Although a front panel with an L-shaped cross section is used, a shield plate is attached to the open end by a shield plate retainer. Do not attach the shield plate to the side with legs (referred to as the closed end for comparison). When the front panel with the printed circuit board attached is inserted into the housing, the shield plates come into contact with the legs between adjacent front panels to make electrical connection to each other. Since the housing is originally grounded, all of these front panels are grounded through the housing. Then, it is the same as a perforated metal casing, which is equivalent to surrounding the entire circuit with a metal container. Even if electromagnetic waves are oscillated in the circuit of the printed board, it is possible to effectively prevent the electromagnetic waves from leaking out of the housing. Also, since one side of the front panel is open, long-legged elements can be attached to the upper side of the printed circuit board without impairing the degree of freedom in circuit design. Even a printed circuit board with a high mounting density near the front panel can be mounted on the housing after being mounted on the front panel of the present invention.

[0007]

【Example】

 FIG. 1 is a perspective view showing a state in which a plurality of printed circuit boards are mounted on a housing using a front panel according to an embodiment of the present invention. The front panel 1 is parallel to the upper surface. Below this, the printed circuit boards 4 are hung one by one in parallel at equal intervals. Below the printed board 4, there is a backplane board 9. This is fixed to the bottom of the housing 8 by some means. This means that the plurality of printed circuit boards 4 are housed between the front panel 1 and the backplane board 9. This arrangement is the same for the conventional arrangement.

FIG. 2 shows the structure of the back surface of the front panel 1. The front panel 1 is formed by bending a thin metal plate into an L-shaped cross section. Only one bent leg 14 is provided. The one without the legs 14 has an open shape. A shield plate pressing member 2 having an L-shaped cross section is fixed to the back surface by a fixing screw 5. The shield plate pressing member 2 is for fixing one or a plurality of shield plates 3 to the front panel 1. The shield plate holder is shown in FIG. The cross section is L-shaped, but the wider one is the fixing portion 15 for attaching to the front panel 1. The narrower folded portion 16 is a portion perpendicular to the front panel. A slit hole 6 is bored in the fixed portion 15 at the boundary. Further, the fixing portion 15 has a screw hole 7. The width of the fixed part is k. The width of the folded portion is h. The folded portion is not the same over the entire length, and is only h where the slit hole 6 exists, and is cut lower at other portions. The height of the notch 17 is n. k> h> n. n is determined by the upper limit of the mounting position of the lead leg of the device on the printed circuit board. That is, the element is mounted at various positions on the printed board, but the lead leg of this element is located below the height n of the notch 17. Therefore, the position of the cutout portion 17 is different for each print substrate. Moreover, the size and position of the slit holes are different. The optimum combination of the shield plate pressing member 2 and the shield plate 3 is used.

FIG. 4 shows the shape of the shield plate 3. It can be made by bending a metal plate with high elasticity. For example, a copper plate can be used. As mentioned above, the length m can be arbitrarily changed. A kerf 18 is cut halfway perpendicular to the longitudinal direction. The bent portion 19 is bent, and the back surface is a flat bent portion 20. The entire surface is a flat pressing portion 21 and an arcuate portion 22 following the pressing portion 21. The arcuate portion 22 contacts the leg portion of the adjacent front panel 1. The purpose of the folded portion 16 of the shield plate pressing member 2 is to fix the shield plate 3 having elasticity. The base of the shield plate 3 is fixed by sandwiching the folding portion 16 from the front and back by the bent portion 20 and the pressing portion 21 of the shield plate 3. The base of the shield plate 3 is fixed, but the end of the arcuate portion 22 which is the other end is free. That is, the shield plate 3 is cantilevered and has a shape that easily exhibits elasticity. FIG. 3 is a cross-sectional view showing a state in which the shield plate 3 is fixed to the front panel 1 by the shield plate pressing metal fitting 2 and a plurality of front panels 1 are further housed in a housing. As can be seen from this, the arcuate portion 22 of the shield plate 3 comes into contact with the bent leg portion 14 of the adjacent front panel 1. A printed circuit board 4 is attached below the front panel 1. With such a structure, unlike a conventional front panel having legs on both sides, the lead legs of the element mounted on the printed circuit board may come into contact with the side legs of the front panel. There is no. FIG. 10 is a cross-sectional view of a case where a printed circuit board in which an element is attached to a portion very close to the front panel 1 is included. The lead legs of the element parts are at the same height as the legs of the front panel, but one side is open, and since the shield plate pressing metal 2 is also a notch 17 at this position, it is a lead. There is no contact between the feet. This is an advantage that is difficult to expect in the conventional example. However, it may be a little troublesome for this to happen. That is, the shape of the shield plate pressing member 2 differs depending on the printed circuit board 4, and the length m of the shield plate 3 must also be different. FIG. 11 is a perspective view showing two examples of the shield plate holding metal fitting 2. In (a), there are three slit holes and four notches 17 are provided. The cutout portion 17 must be determined by the distribution of the lead legs of the element. Further, in (b), there are only two slit holes, and there are only three notches 16 as well. As described above, the shape of the shield plate pressing member 2 and the length of the shield plate 3 must be determined by the distribution of the elements on the printed circuit board to be attached thereto. In other words, many kinds of shield plate holding fittings 2 and shield plates 3 are required. However, in reality, even if there are a large number of types of printed circuit boards, the distribution of the lead legs of the element should be able to be summarized in a small total, so many types of shield plate holders 2 It does not always require various types of shield plates.

[0010]

[Effect of the device]

 A plurality of front panels are electrically coupled to each other by a shield plate, but they can be connected to the housing and grounded. Therefore, it is possible to prevent electromagnetic waves from leaking to the outside. When the front panel is inserted into the housing together with the printed circuit board, conduction between the front panels is automatically established and these are grounded, so there is no need to attach the ground wire. The one with legs on both sides like the conventional front panel structure may not be mounted due to the lead of the element, or it may be mounted unknowingly and may cause malfunction. Since there is no leg part of the PCB and it is open, there is no such a case, and since the element can be soldered to the edge of the PCB, the degree of freedom in the wiring design of the PCB does not deteriorate. The standard value of the VCCI self-regulation (type 1 information device) is 50 dB or less at 30 MHz to 230 MHz and 57 dB or less at 230 MHz to 1,000 MHz when the electric field strength of the leak electromagnetic wave is 3 m distance method. It was found that when the printed circuit board front panel of the present invention is used, a margin of 6 dB to 10 dB with respect to the reference value can be obtained. As described above, the printed circuit board front panel is effective when used in the field of electronic devices or the like where the front panel of the printed circuit board is exposed and attached to the housing and electromagnetic wave leakage prevention is required.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a front panel is stored in a housing.

FIG. 2 is a perspective view of the back surface of the front panel according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a combined front panel according to an embodiment of the present invention.

FIG. 4 is a front view and a side view of a shield plate used in the present invention.

FIG. 5 is a front view, a plan view, and a side view of a shield plate holding metal fitting used in the present invention.

FIG. 6 is a plan view showing contact between front panels according to a conventional example.

7 is a perspective view of a shield plate used for the front panel of FIG.

FIG. 8 is a plan view showing contact between front panels according to another conventional example.

9 is a perspective view of a shield plate used for the front panel of FIG.

FIG. 10 is a sectional view of the vicinity of the front panel for showing that the lead legs of the device do not contact the front panel between the front panels of the present invention.

FIG. 11 is a perspective view showing an example of a shield plate retainer having different shapes used in the present invention.

[Explanation of symbols]

 1 Front Panel 2 Shield Plate Holding Metal 3 Shield Plate 4 Printed Circuit Board 5 Fixing Screw 6 Slit Hole 7 Screw Hole 8 Housing 9 Backplane Board 10 Front Panel 11 Shield Plate 12 Front Panel 13 Sheet Rudder plate 14 Bending leg part 15 Fixing part 16 Folding part 17 Notch part 18 Notch groove 19 Bending part 20 Bending part 21 Holding part 22 Arc-shaped part

Claims (2)

[Scope of utility model registration request] 1. An electronic device in which a printed circuit board attached to a front panel from an upper surface is inserted and housed in a housing in which one bottom surface and four side surfaces continuous with the bottom surface are surrounded by metal plates at a constant interval. Is an L-shaped metal plate having one end bent inward, and an elastic shield plate is attached to the inside of the front panel through a shield plate retainer for the unfolded front panel. The shield plate comes into contact with the bent side surface of the adjacent front panel, and the shield plate electrically connects the adjacent front panels to each other to ground the housing, thereby grounding the whole body. The rudder plate pressing metal fitting is fixed to the front panel at one fixing surface with an L-shaped cross section, and has a slit hole at the boundary with the folding section, and the slit hole is formed on the front panel. A front panel of a printed circuit board having an electromagnetic wave leakage prevention structure, characterized in that a shield plate is inserted and fixed, and a folded portion of a portion where the shield plate does not exist is cut out to be low. 2. An electronic device in which a printed circuit board mounted on a front panel is inserted and housed from a top surface at a constant interval in a housing in which one bottom surface and four side surfaces continuous with the bottom surface are surrounded by a metal plate. Is an L-shaped metal plate having one end bent inward, and an elastic shield plate is attached to the inside of the front panel through a shield plate retainer for the unfolded front panel. The shield plate comes into contact with the bent side surface of the adjacent front panel, and the shield plate electrically connects the adjacent front panels to each other to ground the housing, thereby grounding the whole body. The rudder plate pressing metal fitting is fixed to the front panel at one fixing surface with an L-shaped cross section, and has a slit hole at the boundary with the folding section, and the slit hole is formed on the front panel. It is designed to be inserted and fixed, and the folding part of the part where the shielding plate does not exist is cut out low, and the shielding plate of different length and the folding part Using shield plate holders of different lengths, select the shield plate holder and shield plate suitable for the mounting condition of the elements on the printed circuit board, and mount the printed circuit board on the shield. Cold plate retainer and seal
A printed circuit board front panel with an electromagnetic wave leakage prevention structure characterized in that it is attached to the front panel together with the field plate, and is mounted on the housing.