JPH05327270A - Electromagnetic shielding of circuit board - Google Patents

Abstract

PURPOSE:To provide a method for electromagnetic shielding of a circuit board by which the diffusion of an electromagnetic noise from the circuit board can be prevented more effectively. CONSTITUTION:A circuit board A' is so structured that the entire board including electronic components P1-P4 is coated with thermosoftening electromagnetic shielding material S which is cut to the same shape as the circuit board A' and the shielding material S is heated and then cooled to be stuck tightly to the board. By such a structure, the diffusion of an electromagnetic noise from the circuit board A' can be prevented effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic shielding method for a circuit board, and more particularly to an electromagnetic shielding method for a circuit board including mounted products.

[0002]

2. Description of the Related Art There are two types of countermeasures against an electromagnetic noise generation source: to eliminate generation of electromagnetic noise or to suppress generated electromagnetic noise before it spreads widely.
The former is a matter of selecting the circuit method, and the latter is a matter of assembling the circuit. The conventional latter means are: By using a multi-layer substrate, the mutual impedance of the circuits is suppressed. 2. Electronic components are added to the signal line to suppress noise energy. 3. Shorten the wiring between circuit units. 4. Shield the wiring between circuit units. 5. Noise energy is suppressed by adding electronic components to the connections between circuit units. 6. Connect the metal inside the product case to the same potential as the frame ground to prevent it from floating. 7. Shield the product case. There are various methods. The diffusion of electromagnetic noise has been suppressed while making full use of these methods. The effective means for suppressing diffusion of electromagnetic noise is to perform it at the root of the source, and the method is more effective as the contents of the younger numbers in the items 1 to 7 above. As one of the upper means, a method is known in which a copper paste layer is printed on the outer surface of the circuit board to wrap the circuit board with a conductive layer to form an electromagnetic shield. The method will be briefly described below. FIG. 4 is a block diagram showing an example of a conventional process for assembling the circuit board A, and FIG. 5 is a sectional view showing a schematic structure of the board A. As shown in FIG. 4, in the conventional assembly of the circuit board A, a printed circuit board is first manufactured as a multi-layer circuit board by a circuit board maker (printed circuit board steps F4.1 to F4.4). Next, an assembly maker mounts electronic components on the printed circuit board and solders them to make a circuit board A (board assembly steps F4.5 to F4.6). The electromagnetic shielding of the circuit board A is performed on the board surface other than the component mounting portion, and the circuit board A has a sectional structure as shown in FIG. In this way, the diffusion of electromagnetic noise from the circuit board A could be suppressed.

[0003]

In the conventional electromagnetic shielding method for the circuit board A as described above, the effect of suppressing the diffusion of electromagnetic noise tends to be diminished as the area of mounted components increases. This tendency is particularly noticeable in the recent planar mounting as a high-density mounting method. That is, since the high-density mounting board technology that is currently demanded uses a large number of planar mounting components, the mounting feet of the front mounting components appear on the back surface. We have achieved high density by mounting many parts on both sides while devising so that the mounting feet do not restrict the mounting of parts on the back. In this case, when viewed from the standpoint of the electromagnetic shield, the surface on which no parts are mounted was reduced, and as a result, the effect of electromagnetic shielding was sometimes halved. In order to solve the problems in the related art, the present invention provides an electromagnetic shield method for a circuit board by improving the electromagnetic shield method for the circuit board and more effectively suppressing the diffusion of electromagnetic noise. The purpose is.

[0004]

In order to achieve the above object, the present invention provides a method for electromagnetically shielding a circuit board including a mounted product, wherein the mounted product is made of a heat-softening electromagnetic shield material matching the shape of the substrate. An electromagnetic shield method for a circuit board is characterized in that the entire board including the above is covered, and at least the shield material is heated and then cooled and brought into close contact with the board. Furthermore, it is an electromagnetic shielding method for a circuit board in which the shield material is formed by bonding an insulating layer and a conductive layer together. Furthermore, it is an electromagnetic shielding method for a circuit board in which the insulating layer is partially cut so that the conductive layer of the shield material is in contact with the ground of the board. Further, there is provided an electromagnetic shielding method for a circuit board, wherein the shield material is formed by appropriately providing an air vent around the mounted product covered with the shield material.

[0005]

According to the present invention, the above-mentioned entire substrate including the mounted product is covered with the electromagnetic shielding material having a softening property adapted to the shape of the circuit board, and at least the shielding material is heated and then cooled to cool the shielding material. It is brought into close contact with the substrate. Furthermore, the shield material is formed by bonding an insulating layer and a conductive layer together. Further, the insulating layer is partially cut out so that the conductive layer of the shield material is in contact with the ground of the substrate. Further, the shield material is formed by appropriately providing an air vent around the mounted product covered with the shield material. As a result, the diffusion of electromagnetic noise from the circuit board is more effectively suppressed.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not of the nature to limit the technical scope of the present invention. 1 is a block diagram showing an assembling process of a circuit board A'according to an embodiment of the present invention, FIG. 2 is a sectional view showing a schematic structure of the substrate A ', and FIG. 3 is an assembling process of the substrate A'. It is explanatory drawing which shows each state of. Further, the same symbols are used for the elements common to the block diagram showing an example of the assembling process of the conventional circuit board A shown in FIG. 4 and the sectional view showing the schematic structure of the board A of FIG. As shown in FIG. 1, in the process of assembling the circuit board A'of this embodiment, first, in the printed circuit board process (F1.1 and F1.2), an ordinary printed circuit board B without electromagnetic shield is made. Next, the board assembly process (F
After soldering the electronic component in 1.3 to F1.7), the insulating layer S1 and the conductive layer S2 are overlapped and heat-processed to perform electromagnetic shielding. FIG. 2 shows a cross-sectional structure of the circuit board A'produced by this series of steps. The details of the board assembling step in this series of steps will be described below with reference to FIGS.
This will be described with reference to (d). FIG. 3A shows a state in which the board is being assembled after components are mounted (F1.3) and soldered (F1.4). P1 to P4 in the figure represent electronic components (corresponding to mounted products), and the circles at the four corners of the board indicate holes for mounting the board. The line drawn between this hole and each part shows the wiring L which constitutes an electronic circuit. FIG. 3B shows a state in which the insulating sheet (insulating layer) S1 is generated (F
1.5). The shape of the insulating sheet S1 is the ground connection portion G.
(The four corners in the figure) are removed.
The air hole H1 is provided in the portion corresponding to the contour of the. FIG. 3C shows a state in which the conductive sheet (conductive layer) S2 is generated (F1.6). The shape of the conductive sheet S2 is a substrate shape in which the air holes H2 are provided at the same locations as the air holes H1 provided in the insulating sheet S1.

Next, the conductive sheet S2 is replaced with the insulating sheet S
An electromagnetic shield material S is formed by laminating it on top of 1. At this time, the air holes H1 and H2 of both sheets S1 and S2 are in a connected state. Further, each sheet S1 and S2 has a shape in which a hole is formed in the corresponding portion, if necessary, if the substrate has a connector or the like. Further, each of the sheets S1 and S2 is made of a heat softening material at a specific temperature Ta, and the temperature Ta thereof is lower than the soldering temperature Tb for mounting components. That is, generally, the material used for the overcoat layer, the copper paste layer, etc., which is a conventional substrate processing material, satisfies the thermal softening condition. Next, the two sheets S1 and S2 are attached to each other and installed so as to cover the entire substrate after the component mounting and soldering to form a substrate unit. This substrate unit is heated at a temperature Ta to soften both sheets S1 and S2, and then cooled to perform thermal processing (F1.
7). Since this thermal processing is performed at a temperature lower than the soldering temperature Tb, the soldering is not impaired, and both sheets S
The air holes H1 and H2 of 1 and S2 allow air between the sheet and the substrate to escape, so that the sheets S1 and S2 have electronic parts P1 to P1.
It adheres to the substrate so as to cover P4. And FIG. 4 (d)
As shown in, the electromagnetic shielding of the entire board is performed. As a result, diffusion of electromagnetic noise from the circuit board A'is suppressed more effectively than in the conventional example. This effect is particularly remarkable in high-density planar mounting. On the contrary, the electromagnetic shield protects the circuit board A ′ from electromagnetic noise from the outside and also has an effect of preventing malfunction of the circuit. Further, in the above embodiment, one set of the insulating sheet S1 and the conductive sheet S2 is used, but by using a plurality of sets, the shield effect can be further improved. In the above-mentioned embodiment, the insulating sheet S1 and the conductive sheet S2 are attached to each other, and the whole substrate after the component mounting and soldering is covered. However, in actual use, the sheets S1 and S2 may be sequentially covered without any problem. There is no.

[0008]

Since the circuit board electromagnetic shielding method according to the present invention is configured as described above, the diffusion of electromagnetic noise from the circuit board can be suppressed more effectively than in the conventional example. This effect is particularly remarkable in high-density planar mounting. In addition, the electromagnetic shield conversely protects the circuit board from electromagnetic noise from the outside, and has an effect of preventing malfunction of the circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an assembly process of a circuit board A ′ according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic structure of a substrate A ′.

FIG. 3 is an explanatory view showing each state in the assembly process of the board A ′.

FIG. 4 is a block diagram showing an example of a conventional assembly process of a circuit board A.

5 is a sectional view showing a schematic structure of a substrate A. FIG.

[Explanation of symbols]

 A ... Circuit board (board) B ... Printed circuit board P1-P4 ... Electronic component (mounting product) S ... Electromagnetic shield material (shield material) S1 ... Insulating sheet (insulating layer) S2 ... Conductive sheet (conductive layer) H1, H2 ... Deflated

Claims (4)

[Claims] 1. A method of electromagnetically shielding a circuit board including a mounted product, wherein the entire substrate including the mounted product is covered with a heat-softening electromagnetic shield material matching the shape of the substrate, and at least the shield material is heated. After that, the circuit board is cooled and brought into close contact with the board, and an electromagnetic shield method for a circuit board is provided. 2. The electromagnetic shielding method for a circuit board according to claim 1, wherein the shield material is formed by bonding an insulating layer and a conductive layer together. 3. The electromagnetic shielding method for a circuit board according to claim 1, wherein the insulating layer is partially cut so that the conductive layer of the shield material is in contact with the ground of the substrate. 4. The electromagnetic shielding method for a circuit board according to claim 1, wherein the shield material is formed by appropriately providing an air vent around the mounted product covered with the shield material.