JPH0567065U - Grounding structure of electronic equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] The soldering process between the metal case and the printed circuit board is omitted to improve the assembly workability. [Structure] An axial hole is formed at the tip of a case fixing screw, and a coil spring is press-fitted into this hole. The screw with coil spring, in which the screw and the coil spring are integrally combined in the axial direction, is screwed into the lower case to fix the upper case to the lower case, and the tip of the coil spring press-contacts the printed circuit board inside the case to print. A ground conduction path is formed between the ground land of the substrate and the metal case.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure for electromagnetically shielding an electronic device circuit board, and more particularly, to a grounding structure between a printed board and a metal case accommodating the printed board.

[0002]

[Prior Art]

 When designing electronic devices, circuit boards that handle high-frequency signals are generally housed in metal cases to prevent electromagnetic interference with external circuits, and are then subjected to strict electromagnetic shielding. In this case, the earth land of the printed circuit board is grounded by electrically connecting the case and the earth land by means such as soldering to the case.

FIG. 4 is an external perspective view showing a grounding structure of a conventional electronic device. In the figure, 10 is an upper case, 12 is a lower case, and 13 is a printed circuit board on which an electronic circuit for handling high frequencies is mounted. Side plates 14 and 14 are bent and formed in a U shape in the lower case 12 for holding the printed circuit board 13, and the printed circuit board 13 is mounted so as to be sandwiched between the both side plates 14. For this reason, a cut-and-raised claw 15 is formed on one of the side plates 14, and soldering is performed between the ground land 13a of the printed circuit board 13 and the cut-and-raised claw 15, so that the printed circuit board 13 is mounted on the lower case 12. The ground lands 13a of the printed circuit board 13 are fixed and electrically connected to the lower case 12. A screw tap 16 is formed on the other side plate 14.

The upper case 10 is attached from above the lower case 12, and a screw 18 is screwed into the screw tap 16 by aligning the positions of the screw insertion hole 17 and the screw tap 16. Therefore, a ground conduction path is formed between the metal cases 10 and 12 and the printed circuit board 13.

[0005]

[Problems to be solved by the device]

 However, since there is a difference in heat capacity between the cut-and-raised claw 15 and the earth land 13a of the printed board 13, considerable skill is required, and the case and the printed board are small. However, the work is not so easy as this, and therefore, a solder defect is likely to occur. If such defective soldering is not detected in the product inspection before shipment, the solder may crack later due to deterioration over time, resulting in insufficient shielding effect and noise. There is also a problem that soldering becomes more difficult if there is an error in the size of the cut and raised claw or the position of the earth land.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to omit soldering, which does not have good workability, to reduce the number of work steps and eventually to reduce the product cost.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, in the grounding structure of an electronic device of the present invention, an electronic device for electrically connecting a metal case accommodating a printed board and an earth land of the printed board to electromagnetically shield the printed board. In the grounding structure, the screw is tapped on the lower case to attach the upper case to the lower case.A hole is bored in the axial direction from the tip of the mounting screw, and one end of the coil spring is pressed into the hole. Then, the screw and the coil spring are integrally formed, and the other end of the coil spring is pressed against the earth land of the print substrate when the screw is attached.

[0008]

[Action]

 When one end of the coil spring is pressed into the tip of the mounting screw, the screw and the coil spring are integrally formed in the length direction. When the upper case is attached to the lower case by screwing this screw into the screw tap of the lower case, the other end of the coil spring reaches the printed circuit board inside the case, and presses the earth land of the printed board according to the screw fastening. It will be. For this reason, the lower case to which the upper case is attached forms an earth conduction path between the lower case and the earth land of the printed board through the screw, and shields the printed board housed in the case from electromagnetic waves.

[0009]

【Example】

 Hereinafter, a device grounding structure of the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of a screw with a coil spring used in the present invention. The screw 20 with a coil spring is a commonly used metric coarse screw, and is, for example, a M21 type screw 21 and a coil spring 23 that are integrally connected.

The screw 21 is formed with a drill hole 22 having a predetermined hole diameter in the axial direction from the tip portion 21a toward the screw head portion 21b, for example, a diameter of 1 mm. In FIG. 1, the hole 22 of the shaft core is shown in a partially cutaway sectional view in order to clearly show the hole 22. The coil spring 23 connected to the screw 21 is a spring formed by winding an elastic wire having a diameter of 1 mm several times, and one end thereof has an insertion end 24 linearly extended in the coil axial direction. The insertion end 24 is press-fitted into the hole 22, and the screw 21 and the coil spring 23 are axially connected as shown in the drawing. Although a large amount of stress is required for press-fitting, it is desirable that the coil spring 23 once press-fitted cannot be easily pulled out.

FIG. 2 shows a device structure to which the screw 20 with the coil spring is applied. In the figure, 30 is an upper case, 33 is a printed circuit board, and 40 is a lower case. The printed board 33 is fixed to the lower case 40 by an appropriate method without using soldering. The earth land 34 is formed below and in the center of the printed circuit board 33, but is not soldered to the case 40.

On the other hand, an engaging portion 42 parallel to the print substrate is formed at an edge portion of the lower case 40 that is bent in the vertical direction from the bottom portion, and a screw tap 43 is formed in the engaging portion 42. The upper case 30 is attached from above the lower case 40 configured as described above, and the positions of the screw insertion hole 32 and the screw tap 43 are aligned. The screw 20 with the coil spring inserted from the screw insertion hole 32 is screwed into the screw tap 43 to fix the upper case 30 to the lower case 40 as shown in FIG.

When the screw is fastened, the tip 25 of the spring reaches the earth land 34 of the printed circuit board 33, and the screw 20 with the coil spring presses the printed circuit board 33 according to the fastening. When the screw 20 is completely tightened, the restoring force of the compressed coil spring 23 strongly presses the printed circuit board. In this state, the tip 25 of the spring bites into the earth land 34, so that the cases 30 and 40 and the printed circuit board 33 are electrically connected to each other to form an earth conduction path.

The circuit formed on the printed circuit board 33 is electromagnetically shielded by the cases 30 and 40, and stable operation is obtained. Since the coil spring 23 is held in the direction in which it is sandwiched between the screw 21 and the printed circuit board 33, the coil spring 23 does not fall off the screw 21.

[0015]

[Effect of the device]

 As described above, according to the grounding structure of an electronic device of the present invention, a hole is axially drilled from the tip of the mounting screw that is screwed to the screw tap of the lower case to attach the upper case to the lower case. , The one end of the coil spring is press-fitted into the hole to integrally form the screw and the coil spring, and the other end of the coil spring is pressed against the earth land of the printed circuit board when the screw is attached. Therefore, the upper case is fixed to the lower case by fastening the screw with the coil spring, and the ground conducting path is formed between these cases and the ground land of the print substrate. As a result, the printed circuit board is electromagnetically shielded by the case, and stable operation is possible. Further, since the present invention can omit the soldering process, which is difficult to work, the assembly and maintenance work can be facilitated, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an external perspective view of a screw with a coil spring used in the grounding structure of the present invention.

FIG. 2 is a view showing a printed circuit board and a case structure of the present invention.

FIG. 3 is a partial cross-sectional view showing how a grounding passage is formed by a screw with a coil spring.

FIG. 4 is a diagram showing a conventional ground structure.

[Explanation of symbols]

 20 screw with coil spring 21 screw 22 hole 23 coil spring 24 insertion end 30 upper case 33 printed circuit board 34 earth land 40 lower case 43 screw tap

Claims (1)

[Scope of utility model registration request] 1. In a ground structure of an electronic device for electrically connecting a metal case for housing a printed circuit board and an earth land of the printed circuit board to electromagnetically shield the printed circuit board, a screw tap of a lower case is screwed. When the upper case is attached to the lower case, a hole is axially formed from the tip of the mounting screw, and one end of the coil spring is press-fit into the hole to integrally form the screw and the coil spring. A ground structure for an electronic device, wherein the other end of the coil spring is pressed against a ground land of the printed circuit board when the screw is attached.