JP2516104Y2 - Printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a printed wiring board.

2. Description of the Related Art Conventionally, as a printed wiring board, there has been known a printed wiring board having a structure in which a grounded conductive layer of a printed circuit board is pressed to be electrically connected to a metal case housing an electronic device by screwing. This printed wiring board includes a printed circuit board having a predetermined wiring pattern made of copper foil, a ground conductive layer bonded to the printed circuit board to ground the wiring pattern of the printed circuit board, and a metal case for covering the electronic device. , And then
Tighten the screw inserted in the screw insertion hole of the printed circuit board to the screw mounting part of the case, thereby connecting the printed circuit board and the case and pressing the ground conductive layer of the printed circuit board to the metal case to make it conductive. There is.

Here, when the ground conductive layer of the printed circuit board is pressed against the case to make it conductive, it is necessary to tighten the screw with a torque of a certain value or more in order to ensure conduction. At that time, excessive tightening may cause an unexpected mechanical stress to be applied to the printed circuit board. In this case, as shown in FIG. 6, the ground conductive layer 900 located near the screw insertion hole 800 may have a fractured portion 901 that breaks in a direction traversing the ground conductive layer 900, and the ground conductive layer 900 may be disconnected. Then, it is disadvantageous to ensure the original circuit function of the printed circuit board.

Further, even when unexpected mechanical stress such as vibration acts on the printed circuit board, the ground conductive layer 900 may be similarly broken in a direction traversing the same.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and an object thereof is to provide a first conductive portion of a ground conductive layer even when an unexpected mechanical stress is applied. It is an object of the present invention to provide a printed wiring board that is advantageous in avoiding the occurrence of a breakage portion that breaks in the direction crossing the line, maintaining the ground conductive layer in a good condition, and ensuring the original circuit function of the printed circuit board.

[Means for Solving the Problem] A printed wiring board of the present invention is a printed circuit board having a predetermined wiring pattern and a screw insertion hole penetrating in the thickness direction,
By tightening the ground conductive layer that is held on the printed circuit board and grounds the wiring pattern of the printed circuit board, the metal case that covers the electronic device, and the screw inserted into the screw insertion hole of the printed circuit board to the screw mounting part of the case, The ground conductive layer is composed of a screw that connects the printed circuit board and the case, and the ground conductive layer is a first conductive portion that grounds the wiring pattern of the printed circuit board and a first conductive portion that is pressed against the wall surface of the case by tightening the screw and conducts to the case. The second conductive portion and the first conductive portion and the second conductive portion, which have conductivity and are conductive, have lower strength than the first conductive portion, and are unexpected when tightening the second conductive portion and the case with screws. And a breakable portion that breaks before the first conductive portion breaks when the mechanical stress is applied. Screws can be screws and bolts.

[Operation] If unexpected mechanical stress is applied to the printed circuit board due to excessive tightening torque of screws, vibration, etc.,
Since the easily breakable portion having low strength is broken before the first conductive portion of the ground conductive layer is broken, the first conductive portion and the second conductive portion are separated. Therefore, the mechanical stress acting on the first conductive portion of the ground conductive layer is reduced or eliminated. Therefore, disconnection of the first conductive portion of the ground conductive layer is avoided in advance.

[Embodiment] The printed circuit board of this embodiment is applied to a vehicle-mounted control device. This printed wiring board is composed of a printed board 1, a ground conductive layer 2, a case 3 and a screw 4.
A predetermined wiring pattern is formed of copper foil on the printed circuit board 1 as in the conventional case, and an electronic device is mounted on the printed circuit board 1. A screw insertion hole 10 penetrating in the thickness direction is formed in a corner of the printed circuit board 1.

The grounding conductive layer 2 is made of copper foil and is bonded and held on the printed board 1 to ground the wiring pattern of the printed board 1. The ground conductive layer 2 includes a back surface GND pattern 20 as a first conductive portion bonded to the back surface of the printed circuit board 1, a second conductive portion 21 similarly bonded to the back surface of the printed circuit board 1, and a printed circuit board 1 similarly.
The easily breakable portion 22 which connects the back side GND pattern 20 and the second conductive portion 21 to each other on the back side of the back surface, the front side GND pattern 23 bonded to the front surface of the corner of the printed circuit board 1, and the printed circuit board 1 in the thickness direction. And a sleeve portion 24 that defines a through hole 11 penetrating therethrough. Sleeve part 24
Connects the back side GND pattern 20 and the front side GND pattern 23. The back side GND pattern 20 is for grounding the wiring pattern of the printed circuit board 1, and is grounded to the vehicle body via the harness via the connector.

The easily breakable portion 22 is the back side GND pattern 20 and the second conductive portion 21.
It is constituted by forming an elongated slit 25 having a substantially L-shape in the boundary region between and, and the width dimension of the easily breakable portion 22 is set small so as to be easily broken. Therefore, when mechanical stress is applied to the printed circuit board 1 etc., the back side GND
The easily breakable portion 22 is broken even before the pattern 20 is broken. When the components are mounted on the printed circuit board 1, solder is attached to the through holes 11.

The case 3 covers the electronic device mounted on the printed circuit board 1. The case 3 is formed of a conductive metal in order to prevent electromagnetic noise from the electronic device housed in the case 3 from leaking out. In this embodiment, as shown in FIG. 3, the screw 4 inserted into the screw insertion hole 10 of the printed circuit board 1 is tightened to the screw mounting portion 30 of the case 3, whereby the printed circuit board 1 and the case 3 are connected. ing.

Here, in this embodiment, when electromagnetic noise from the electronic device housed in the case 3 is received by the case 3, the case 3,
The second conductive portion 21, the easily breakable portion 22, and the rear surface GND pattern 20 are electrically connected to be grounded to the vehicle body.

By the way, as described above, when the back side GND pattern 20 of the printed circuit board 1 is conducted to the case 3, the torque for tightening the screw 4 is set to a predetermined value or more in order to surely press the second conductive portion 21 against the case 3 to ensure conduction. I have something to do. In this case, as described above, unexpected mechanical stress acts on the printed circuit board 1 and the rear surface GND pattern 20 may be broken in a direction traversing the rear surface GND pattern 20 and the rear surface GND pattern 20 may be disconnected. In this regard, in this embodiment, when unexpected mechanical stress acts on the printed circuit board 1 when tightening the screw 4,
Before the back surface GND pattern 20 is broken, the easily breakable portion 22 having low strength is broken. Therefore, the second conductive portion 21 and the back surface GND pattern 20 are separated by the breakage of the easily breakable portion 22. As a result, further mechanical stress does not act on the rear surface GND pattern 20, and therefore, in the present embodiment, disconnection of the conductive portion of the rear surface GND pattern 20 can be avoided in advance. Therefore, even when unexpected mechanical stress is applied to the printed circuit board 1, one part 20a of the backside GND pattern 20 and the other part 20a
The electrical connection with 20b can be secured, and the circuit function of the printed circuit board 1 can be secured well.

The easily breakable portion 22 is broken and the second conductive portion 21 and the back surface GN
Even if the D pattern 20 is separated, there is no particular problem because the back side GND pattern 20 is grounded to the vehicle body via the connector and the harness.

[Advantages of the Invention] In the present invention, since the easily breakable portion having low strength is broken before the first conductive portion that grounds the wiring pattern of the printed circuit board is broken, the first conductive portion and the second conductive portion are broken. Can be separated, and disconnection of the conductive portion of the first conductive portion can be avoided in advance. Therefore, the conductivity of the first conductive portion that grounds the wiring pattern of the printed board can be ensured, and the circuit function of the printed board is ensured.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is a plan view of a front side corner of a printed circuit board, FIG. 2 is a rear view of a back side corner of the printed circuit board, and FIG. FIG. 4 is a schematic cross-sectional view of the main part, FIG. 4 is a perspective view of the main part, and FIG. 5 is a cross-sectional view taken along the line WW of FIG. FIG. 6 is a rear view of a corner portion of a printed circuit board for explaining the conventional technique. In the figure, 1 is a printed circuit board, 2 is a ground conductive layer, and 20 is a back surface GN.
D pattern (first conductive portion), 22 is a breakable portion, 3 is a case, and 4 is a screw.

Claims (1)

(57) [Scope of utility model registration request] 1. A printed circuit board having a predetermined wiring pattern and a screw insertion hole penetrating in the thickness direction, a ground conductive layer held by the printed circuit board and grounding the wiring pattern of the printed circuit board, and an electronic device. The grounded conductive layer is composed of a metal case and a screw connecting the printed board and the case by tightening a screw inserted into the screw insertion hole of the printed board to a screw mounting portion of the case. Is a first conductive portion that grounds the wiring pattern of the printed circuit board, a second conductive portion that is pressed against a wall surface of the case by tightening the screw and is electrically connected to the case, and the first conductive portion having conductivity. The conductive portion and the second conductive portion are electrically connected to each other, the strength is lower than that of the first conductive portion, and an unexpected mechanical stress is generated when the second conductive portion and the case are fastened by the screw. A printed wiring board comprising: an easily breakable portion that breaks before the first conductive portion breaks when the printed wiring board acts.