JP5179422B2 - Static electricity protection structure - Google Patents

Description

  The present invention relates to a protection structure against static electricity applied to a circuit board. In particular, in order to protect a semiconductor element mounted on a printed circuit board from static electricity, an electrostatic discharge path is formed between the static electricity application point and the ground. The present invention relates to an electrostatic protection structure including a metal plate for electrostatic discharge.

In a conventional electrostatic protection structure for a circuit board, it has been proposed to connect a static electricity application point to a ground with a low impedance (for example, Patent Document 1).
In such a static electricity protection structure, the static electricity applied to the apparatus is configured to be discharged to the ground ground through the shortest path.

Japanese Patent Laid-Open No. 10-241888

As shown in Patent Document 1, in order to quickly release static electricity noise applied to the substrate to the ground, it has been conventionally connected from the point where static electricity is applied to the ground with a metal body (electrostatic discharge metal). Has been done. However, Patent Document 1 does not describe an electrostatic protection structure having a plurality of substrates.
On the other hand, when there are a plurality of substrates in the unit case and there are a plurality of places where static electricity is applied, the substrates are connected by metal pillars or the like to release static electricity.

  In an electronic device having a plurality of substrates, if an attempt is made to take countermeasures against static electricity, the substrates are connected by metal columns as described above. In this case, it is necessary to secure an area for raising the metal columns on the substrate. Yes, it was a restriction on the board mounting area. In addition, there is a problem in that a malfunction occurs due to mutual interference from another substrate in a path through which static electricity escapes.

The electrostatic protection structure according to the present invention includes an electrostatic discharge metal plate for forming an electrostatic discharge path between a static electricity application point and a ground in order to protect semiconductor elements mounted on a plurality of printed circuit boards from static electricity. It is a protective structure, and the electrostatic discharge metal plate is provided at each of a plurality of static electricity application points and is connected to the ground at different points, and the electrostatic discharge metal plate provided on each printed circuit board However, it was set as the structure which mutually opposes.

  According to the present invention, when there are a plurality of substrates in the unit case, component mounting can be performed for each substrate without worrying about the positional relationship between them. Further, it is possible to make a sheet metal shape according to the component mounting of each board. As a result, noise countermeasures can be implemented according to the component mounting of each board, and a device unit with high noise resistance can be realized.

It is a schematic side view of the control controller to which the electrostatic protection structure of this invention is applied. It is a schematic plan view of the metal plate for electrostatic discharge in the electrostatic protection structure of this invention. It is a schematic plan view of the metal plate for electrostatic discharge which shows another example in the electrostatic protection structure of this invention. It is a schematic plan view of the metal plate for electrostatic discharge which shows another example in the electrostatic protection structure of this invention. It is a schematic side view of the control controller which shows the example which applied the electrostatic protection structure of this invention to three board | substrates.

Embodiment 1 FIG.
FIG. 1 is a schematic side view showing a control controller to which an electrostatic protection structure according to Embodiment 1 of the present invention is applied. In FIG. 1, the controller is covered with a resin unit case 1, and a printed circuit board 2a and a printed circuit board 2b exist inside. Semiconductor elements 3a and 3b are mounted on the printed boards 2a and 2b, respectively, and in order to protect the semiconductor elements 3a and 3b from static electricity, a static electricity application point indicated by an arrow A (for example, external access connectors 4a and 4b). ) And the ground 6 have an electrostatic discharge protection structure including electrostatic discharge metal plates 5a and 5b for forming an electrostatic discharge path.

The electrostatic discharge metal plates 5a and 5b are disposed on the printed circuit boards 2a and 2b, respectively. The electrostatic discharge current applied from the electrostatic application points A and B is for electrostatic discharge provided on the printed circuit boards 2a and 2b. It flows to the ground 6 through the metal plates 5a and 5b. For this reason, the structure is such that the static electricity applied from different static electricity application points A and B flows to the ground 6 through different paths.
Further, the respective electrostatic discharge metal plates 5a and 5b are opposed to each other, and are configured to shield the influence of the electrostatic discharge current flowing through the electrostatic discharge metal plates provided on the opposed printed boards.

An example of the shape of the electrostatic discharge metal plates 5a and 5b is shown in FIG. In the illustrated example, it is a rectangular conductive metal plate member, and is supported in parallel to the printed circuit boards 2a and 2b at a predetermined distance from the semiconductor elements 3a and 3b. The dimensions of the electrostatic discharge metal plates 5a and 5b are sufficiently large so as to have a low impedance against the electrostatic discharge current.
Here, “low impedance” refers to an impedance such that the potential of the electrostatic discharge metal plate can be substantially regarded as a ground ground potential, whereby the semiconductor element does not substantially malfunction.
In this way, by taking a square wide dimension as the metal plate for electrostatic discharge, the impedance becomes low with respect to the electrostatic discharge current, and the discharge current is dispersed, so the potential at the point of applying static electricity is substantially regarded as the ground installation potential. Thus, the electromagnetic field generated from the metal plate is reduced to a level at which the semiconductor element does not malfunction, and an electronic device that performs stable circuit operation can be realized.

  In addition, according to such a configuration, even if there are a plurality of static electricity application points, the electrostatic discharge metal plate is provided to face each printed circuit board, so that the opposite static electricity application point is provided. The influence of the applied static electricity can be reduced, the malfunction of the semiconductor element can be eliminated, and a control controller that can operate stably even when static electricity is applied can be realized.

Embodiment 2. FIG.
3 and 4 show an example in which one of the electrostatic discharge metal plates 5b is formed in a thin plate shape having a bent portion instead of a square shape.
In the example of FIG. 3, the path from the electrostatic application point to the ground is formed in a substantially L shape with a thin plate-like metal plate orthogonal to each other. In the example of FIG. The example comprised with the thin plate-shaped metal plate of the diagonal shape to connect is shown. With the shape as shown in FIG. 3, the electrostatic discharge path can be further away from the semiconductor element on the substrate. Further, if the shape is as shown in FIG. 4, the static electricity application point and the ground can be connected by a shorter path.
By using a thin plate-like metal plate for electrostatic discharge as shown in FIG. 3 and FIG. 4, the path of electrostatic discharge current can be limited compared to the case of a wide square shape as shown in FIG. It is possible to avoid the discharge current from flowing directly above the semiconductor element mounted on the substrate.
In addition, in the printed circuit board 2a having the other wide rectangular metal plate 5a, the electromagnetic field mutual interference of the discharge current flowing through the electrostatic discharge metal plate 5b having the bent portion provided in the opposed printed circuit board 2b is detected by itself. Due to the shielding effect of the metal plate 5a having a wide rectangular shape on the side, it can be reduced to a level at which the semiconductor element does not malfunction.

  Although the shielding effect is reduced, when semiconductor components that are susceptible to noise are mounted on both the substrates 2a and 2b, the electrostatic discharge metal plates 5a and 5b are arranged so that the discharge current does not flow immediately above the semiconductor components. Both of them can be formed into a thin plate shape having a bent portion as shown in FIG. 3 or FIG.

Embodiment 3 FIG.
FIG. 5 shows an example in which three printed circuit boards are provided in the unit case. In this example, the static electricity application points of the controller are three points A, B, and C, but the same configuration as in FIG. 1 can be adopted. Also in this case, the structure is such that the electrostatic discharge metal plates 5a, 5b, and 5c are prepared according to the static electricity application points A, B, and C, and are connected to the ground 6 from the respective metal plates 5a, 5b, and 5c. And And at least 2 metal plate for electrostatic discharge is comprised so that it may mutually oppose. In the example of FIG. 5, electrostatic discharge metal plates 5b and 5c are arranged to face each other.
The shape of the electrostatic discharge metal plates 5a, 5b, and 5c is set to an optimum shape according to the mounting state of the semiconductor elements 3a, 3b, and 3c mounted on the respective substrates, so that the static electricity is applied from the respective static electricity application points. Even when the voltage is applied, it is possible to realize a controller that performs stable circuit operation.

  Although FIG. 5 shows an example in which three printed circuit boards are used, even when there are four or more printed boards, a circuit operation that is stable against static electricity can be achieved by similarly connecting each of the plurality of boards to the ground. A controller can be realized.

  1 Unit case, 2a, 2b, 2c Printed circuit board, 3a, 3b, 3c Semiconductor element, 4a, 4b, 4c External access connector, 5a, 5b, 5c Electrostatic discharge metal plate, 6 Ground, A, B, C Static electricity Application point.

Claims (6)

In order to protect semiconductor elements mounted on a plurality of printed circuit boards from static electricity, the electrostatic protection structure includes an electrostatic discharge metal plate for forming an electrostatic discharge path between a static electricity application point and a ground. A metal plate is provided at each of a plurality of static electricity application points and connected to the ground at different points, and the electrostatic discharge metal plates provided on each printed circuit board face each other. Electrostatic protection structure characterized by Electrostatic protection structure of claim 1, wherein the respective printed circuit board to the ESD metal plate provided is made of a conductive metal plate member having a rectangular shape. The metal plate for electrostatic discharge provided on each printed circuit board has one electrostatic discharge metal plate having a wide rectangular shape, and the other metal plate has a thin plate shape having a bent portion. The electrostatic protection structure according to claim 1 . 4. The electrostatic protection structure according to claim 3 , wherein the other of the metal plates for electrostatic discharge is formed in a substantially L shape by a thin plate-like metal plate having a shape orthogonal to each other. 4. The electrostatic protection structure according to claim 3 , wherein the other one of the metal plates for electrostatic discharge is constituted by a thin plate-like metal plate having a shape orthogonal to each other and an oblique shape connecting between the shapes. In order to protect semiconductor elements mounted on a plurality of printed circuit boards from static electricity, the electrostatic protection structure includes an electrostatic discharge metal plate for forming an electrostatic discharge path between a static electricity application point and a ground. A metal plate is provided at each of a plurality of static electricity application points and connected to the ground at different points, and the metal plates for electrostatic discharge provided on each printed circuit board are opposed to each other In order to protect the semiconductor element mounted on the printed circuit board from static electricity, the electrostatic protection structure includes a metal plate for electrostatic discharge for forming an electrostatic discharge path between the static electricity application point and the ground. An electrostatic discharge metal plate is provided for each of the printed circuit boards, and at least two of the electrostatic discharge metal plates face each other. Static electricity protection structure you characterized by being configured to be disposed Te.

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