JPH0458596A - Electromagnetic shield - Google Patents

Abstract

PURPOSE:To make it possible to replace circuit components by covering the circuit components of a printed wiring board with a releasable insulating seal, applying conducting coating to the seal, and keeping a conductor faced with a grounding section in contact with the coated section. CONSTITUTION:A partitioning conductor 3 is installed to a grounding printed wiring circuit 6. Then, the whole body of a printed wiring board 1 and an electronic circuit board 2 is covered with an insulating seal made of releasable sealing resin 4. It is also acceptable to use a heat-shrinkable seal in order to further enhance the insulating properties. In this case, the partitioning conductor is arranged to be exposed where conductive coating is carried out with metal plating or conductive pain 5. Even the exposed partitioning conductor is coated with the conductive paint 5, which makes is possible to replace electronic circuit components 2.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention can be used to shield electromagnetic waves generated from an electronic circuit from being emitted to the outside, or to prevent unnecessary electromagnetic waves from entering the electronic circuit from outside. The present invention also relates to an electromagnetic shielding method for preventing electromagnetic interference between electronic circuits.

[Conventional technology] As various wireless devices and electronic devices have spread, there have been many cases where these electronic devices generate unnecessary radio waves that cause interference with other electronic devices, and this has become a social problem. There is. For this reason, (1) prevent unnecessary radio waves generated inside the electronic device from being emitted to the outside, (2) prevent unnecessary radio waves from outside from entering the device, (3) prevent the unnecessary radio waves generated inside the electronic device from entering the device, and (3) It is necessary to prevent the generated unnecessary radio waves from interfering with other parts of the device.

Conventionally, regarding (1) and (2) above, the entire electronic circuit of the device was covered with a metal case, the device's casing was made of conductive plastic, or the inner surface of the casing was coated with conductive paint or metal plating. This prevents the emission and intrusion of unnecessary radio waves. Regarding (3), electromagnetic interference between circuits has been prevented by using a printed wiring board provided with an electromagnetic shielding layer such as copper paste or by covering each circuit with a metal case.

[Problems to be Solved by the Invention] However, the above-mentioned conventional techniques for preventing the emission and intrusion of unnecessary radio waves in electronic devices or for preventing electromagnetic interference between circuits have the following problems. Ta.

(a) Conductive plastic casings are more expensive than normal plastic casings.

(a) When applying conductive paint to the housing, there are drawbacks to the electromagnetic shielding effect and durability.

(1) It is difficult to shield the entire device with both conductive plastic casings and conductive paint.

(1) Even if a printed wiring board provided with an electromagnetic shield layer is used, it is not possible to prevent electromagnetic interference between electronic circuits after electronic circuit components are mounted on the printed wiring board.

(e) If each circuit is covered with a metal case to prevent electromagnetic interference between electronic circuits, the entire circuit becomes large and heavy. etc.

Incidentally, in recent years, the personalization of electronic devices has become remarkable, as seen in office automation equipment such as word processors and personal computers, and mobile communication terminals such as mobile phones.
There is a demand for smaller and lighter equipment. On the other hand, as mentioned in (a) to (e) above, conventional electromagnetic shielding technology may be insufficient in terms of economy, durability, reliability, and miniaturization and weight reduction of electronic devices. Because of the large number of requests, we were unable to fully meet their demands.

The present invention has been made against this background, and it is possible to improve the electromagnetic shielding effect using the conventional method, and at the same time prevent electromagnetic interference between electronic circuits.
-Compared to the conventional case where each electronic circuit block is covered with a heavy metal case, the electromagnetic shielding part is much lighter and simpler, and it can be mounted on a printed wiring board even after applying electromagnetic shielding. The purpose is to provide an electromagnetic shielding method that allows easy replacement of circuit parts.

[Means for Solving Problems] The structure of the electromagnetic shielding method of the present invention for achieving the above object is as follows: First, the electromagnetic shielding method of the present invention has the following features: and covering the entire printed wiring board and the electronic circuit components mounted thereon with an insulating sealing resin or thin film seal that can be easily peeled off later. A part of the conductor is exposed from the sealing resin or thin film seal, and then metal plating or conductive paint is coated on the sealing resin or thin film seal so that the conductor can be contacted. It is characterized by

[Function] The present invention aims to insulate wiring and electronic circuit components of a printed wiring board from metal plating or conductive paint using a sealing resin or a thin film seal, and connects a ground portion of the printed wiring board to a metal metal layer using a conductor. By short-circuiting the conductor or conductive paint, an electromagnetic shielding effect is provided to the entire printed wiring board and the electronic circuit components mounted on it, and at the same time, an electronic circuit block separated from the conductor by metal plating or conductive paint. Prevent mutual electromagnetic interference. In addition, the shield member is made lightweight by using a film made of metal plating or conductive paint, and by using a sealing resin or thin film seal that can be easily peeled off from the insulating member, it is easy to replace electronic circuit components later. make it easier.

"Example" Hereinafter, an example of the present invention will be described in detail based on the drawings.

(1) First Embodiment FIGS. 1A, B, C, and D are diagrams showing a first embodiment of the present invention, and A shows a printed wiring board 1 and an electronic circuit component 2 mounted thereon from above. B is a cross-sectional view, C is a perspective view showing the arrangement of conductors 3 that partition electronic circuit blocks on printed wiring board 1, and D is sealing resin (or thin film seal) 4.
5 is a sectional view showing an electromagnetic shielding structure using metal plating or conductive paint 5. FIG.

In the electromagnetic rolling method in this first embodiment, first, as shown in FIG. The ground printed wiring circuit 6 (
(Illustrated in Figure 1 B and D) and pillar-shaped, hedge-shaped,
Each electronic circuit block 7 is separated by a partitioning conductor 3 such as a wall. This block 7 indicates a range in which mutual electromagnetic interference is avoided, and for example, in the example of a wireless device, the units include a transmitting section, a receiving section control section, etc. Next, as shown in the first diagram, the entire printed wiring board 1 and electronic circuit component 2 are coated with an insulating sealing resin (or thin film mold) 4 such as epoxy/resin. At this time, the heads of the partitioning conductors 3 that partition the electronic circuit into blocks are exposed from the sealing resin 4. Finally, the sealing resin 4 is plated with metal such as copper or nickel, or a conductive paint 5 is applied. At this time, the sealing resin 4
The head of the conductor 3 protruding from the surface is also plated or coated with conductive paint 5 so as to be integrated. In addition,
The conductor 3 that divides the circuit into blocks 7 is connected to the grounding printed wiring circuit 6 on the printed wiring board 1 from above the sealing resin (or thin film/ru) 4 after sealing the electronic circuit with resin or the like. You can also plug it in.

In the electromagnetic/hardening method of the first embodiment described above, the printed wiring board 1 and the electronic circuit components 2 are sealed with resin and then the metal plating or conductive paint 5 is placed on the printed wiring board 1.
When metal plating or conductive paint 5 is placed directly on the electronic circuit component 2, the printed wiring circuit 8 for signal lines on the printed wiring board 1 (shown in FIG. 1 B and D) and the wiring coming out from the electronic circuit component 2 This is to prevent 7 yotes from occurring. The metal plating or conductive paint 5 applied so that the surface of the sealing resin or thin film seal 4 etc. and the head of the conductor 3 protruding from the surface are integrated is the conductive paint 5 applied to the printed wiring board 1. The grounding printed wiring circuit 6 and the conductor 3 separated into each block of the electronic circuit component 2 are electrically short-circuited, and the electronic circuit component 2 is covered with a conductor for each block C1. In this state, the entire printed wiring board 1 and the electronic circuit components 2 mounted on it are electromagnetically routed, and at the same time, the electronic circuits are electromagnetically routed block by block. It is possible to prevent interference.

(2) Second embodiment Since sealing resin generally has strong adhesive properties, it is easy to peel it off from the printed wiring board or electronic circuit component again after coating the sealing resin on the printed wiring board or electronic circuit component. Therefore, it is almost impossible to replace parts after coating.

Therefore, when redoing electromagnetic molding or replacing parts even after resin sealing, the sealing resin should be one that can be easily peeled off from printed wiring boards and electronic circuit parts even after coating, and that is suitable for metal plating. It is preferable to use a resin that can be covered with conductive paint.

However, the resins that can be easily peeled off after such coating are silicone-based or fluoroplastic-based resins, and are generally difficult to coat due to metal plating or the like. This example shows a countermeasure for the case where a resin that can be easily peeled off from a printed wiring board or electronic circuit component even after coating cannot be obtained and can be used to carry metal plating or conductive paint.

FIG. 2 is a sectional view showing a second embodiment of the invention.

In the figure, 1 is a printed wiring board, 2 is an electronic circuit component,
3 is a partitioning conductor, and 6 is a grounding printed wiring circuit, which are similar to those in the first embodiment. In this example,
The sealing resin layer has a two-layer structure.

In the method of performing electromagnetic shielding using a sealing resin, a resin that can be easily peeled off later is used as the first layer of sealing resin 4a that is directly coated on the printed wiring board 1 and the electronic circuit components 2, and a resin that can be easily peeled off later is used. As the second layer of resin 4b to be coated, a resin that can be coated with metal plating or conductive paint 5 is used, and these are coated with the heads of the partitioning conductors 3 exposed, and finally metal plating is applied on top of them. Alternatively, a conductive paint 5 is applied.

In the method of using a thin film seal instead of the sealing resin, first, instead of the first layer sealing resin, a thin film 4a of polyethylene, vinyl chloride, etc. is used to seal the printed wiring board 1 and the electronic circuit component 2. cover. At this time, thin film sheet 1-
In order to adhere the thin film sheet 4a to the printed wiring board 1 and the electronic circuit component 2, the thin film sheet 4a is made into a bag shape, and the printed wiring board 1 is
After storing the electronic circuit components 2 and the electronic circuit components 2, vacuum sealing is performed. Next, the thin film sheet 4a is sealed with the same second layer resin 4b as above. Next, the conductor 7 that partitions the blocks of the electronic circuit is placed in a second
It is inserted into the printed wiring board l from above the sealing resin layer 4b. Finally, metal plating or conductive paint 5 is placed on the second layer sealing resin 4b.

As described above, the action of the second layer resin 4b makes it easy to apply metal plating and insulating paint, and even after electromagnetic shielding is applied due to the action of the first layer resin 4a, it is easy to remove the printed wiring board 1 and electronic circuit parts. It can be removed and replaced with parts.

(3) Third Embodiment Printed wiring boards usually contain components that require adjustment after mounting, such as frequency oscillation circuits and tone converters, connectors for external connections, memory circuit components, etc. as necessary. Parts that can be replaced later are installed. This third
In this example, even after electromagnetic/rooting is applied, there is a hole in the electromagnetic/hard part at the top of the circuit component, making it possible to access the circuit component from the outside and replace the component. show.

FIG. 3 is a sectional view showing the third embodiment of the present invention. In the figure, 1 is a printed wiring board, 2 is an electronic circuit component, 4 is a sealing resin (or thin film seal), and 5 is a metal plating or conductive paint, which is the same as in the first embodiment.

In this embodiment, a printed wiring board 1 and an electronic circuit component 2
When electromagnetic shielding is applied using the method of the first embodiment, the electronic circuit component 2a that needs to be accessible from the outside of the electromagnetic shield is covered in advance with a cylindrical cover 9 made of plastic or the like. . Thereafter, the printed wiring board 1 and the electronic circuit components 2, 2a, including the cylindrical cover 9, are sealed with resin, and further electromagnetic shielding is applied by applying metal plating or conductive paint. After this electromagnetic shielding is completed, the upper part of the cylindrical cover 10 is cut and removed together with the sealing resin (thin film seal) 4.

In this embodiment, when electromagnetic shielding is applied to printed wiring board 1 and electronic circuit component 2 by the method of the second embodiment,
After covering the electronic circuit component 2a that needs to be accessible from the outside of the electromagnetic shield with a cylindrical cover 9, the whole is covered with, for example, a first layer of thin film seal, and then a second layer of resin is applied on top of the cylindrical cover 9. Seal it with. Next, the conductor 3 that partitions the blocks of the electronic circuit is inserted into the printed wiring board 1 from above the second layer of sealing resin 4b, and metal plating or conductive paint 5 is placed on the sealing resin 4b to form an electromagnetic shield. administer. Thereafter, as described above, the upper part of the cylindrical cover 9 is cut and removed together with the first and second layer sealing structures.

By the above method, the circuit component 2 covered with the cover 9 in advance
In case a, a hole is formed in the upper electromagnetic shield part, so that the circuit component 2a can be contacted or replaced from the outside of the electromagnetic shield.

(4) Fourth Embodiment As mentioned in the second embodiment, the thin film 7- such as a thin film sheet
In the electromagnetic shielding method using the electromagnetic shielding method, resin sealing is required from above the thin film sheet in order to maintain adhesion with the printed wiring board and electronic circuit components, but in this example, a simpler electromagnetic Show silt method.

The thin film sheet that seals the printed wiring board and electronic circuit components is a heat-shrinkable sheet that contracts when heated and maintains its contracted shape even after cooling.

That is, the printed wiring board and electronic circuit components are covered with a heat-shrinkable thin film sheet. Next, this is heated by placing it in a constant temperature bath or the like. Once the sheet has shrunk and adhered to the printed wiring board and electronic circuit components, it is cooled. Next, the conductors that partition the blocks of the electronic circuit are inserted into the printed wiring board from above the heat-shrinkable sheet, and finally, metal plating or conductive paint is placed on the heat-shrinkable thin film sheet. If necessary to improve the adhesion between the printed wiring board and electronic circuit components and the heat-shrinkable thin film, the printed wiring board and electronic circuit components can be placed in a bag-like form using a heat-shrinkable thin film sheet, and sealed in vacuum. You can also heat it from

If there are any circuit components that need to be accessible from outside the electromagnetic shield, as in the third embodiment, cover those circuit components with a cylindrical cover before connecting the printed wiring board and the electronic circuit. The part is covered with a heat-shrinkable thin film sheet, and the upper part of the cylindrical cup is removed after heating, cooling, metal plating, or conductive paint application is completed.

(5) Fifth Embodiment In this embodiment, when covering a printed wiring board and electronic circuit components with a heat-shrinkable thin film sheet in the fourth embodiment, the printed wiring board and electronic circuit components are covered with a heat-shrinkable thin film sheet. Examples of measures to be taken when adhesion is unsatisfactory are shown.

FIG. 4 is a sectional view showing the fifth embodiment of the present invention. In the figure, ■ is a printed wiring board, 2 is an electronic circuit component, 3 is a partitioning conductor, 5 is metal plating or conductive paint, and 6 is a grounding printed wiring circuit, which is the same as described in the first embodiment. It is similar to In this embodiment, before covering the printed wiring board l and electronic circuit components 2 with the heat-shrinkable sheet 10 described in the fourth embodiment, the printed wiring is A void-filling resin 11 is placed on the board 1 using a lightweight foaming resin such as expanded polystyrene.
The surface to be covered with the heat-shrinkable sheet 10 is made flat. In this way, when heat-shrinkable sheet 10 is placed over printed wiring board 1 and electronic circuit component 2 and heated, heat-shrinkable sheet 10 can be brought into close contact with printed wiring board 1 and electronic circuit component 2. The subsequent treatment is performed in the same manner as in the fourth example.

Note that the present invention is not limited to the above-mentioned embodiments (it goes without saying that the present invention can be applied in various ways and can be implemented in various ways in accordance with the spirit thereof).

[Effects of the Invention] As is clear from the above explanation, the electromagnetic shielding method of the present invention is capable of sealing a printed wiring board and the entire electronic circuit components mounted thereon using an insulating sealing resin that can be easily removed later. Alternatively, each block of an electronic circuit can be covered with a thin film/rubber and coated with metal plating or conductive paint, or a conductor that short-circuits the ground part of the printed wiring board and the metal plating or conductive paint of the thin film shield. This is an electromagnetic shielding method that can give an electromagnetic shielding effect to the entire printed wiring board and the electronic circuit components mounted on it by separating the two, and at the same time prevent electromagnetic interference between electronic circuits, and is more effective than conventional methods. It has a high electromagnetic shielding effect and can prevent electromagnetic interference between electronic circuits, giving the housing of electronic equipment a 7-wave shielding effect, and protecting individual electronic circuit professionals.
The electromagnetic shielding part is much lighter than the case where the circuit is covered with a heavy metal case, the electromagnetic shielding method is simple, and even after applying the electromagnetic shielding, it is easy to replace the circuit components mounted on the printed wiring board. There is an advantage to having one.

[Brief explanation of the drawing]

Figures 1A, B, C, and D are views showing one embodiment of the present invention, Figure 2 is a sectional view showing a second embodiment of the invention, and Figure 3 is a third embodiment of the invention. FIG. 4 is a sectional view showing a fifth embodiment of the present invention. Dobrint wiring board, 2... Electronic circuit component, 3... Partitioning conductor, 4... Sealing resin (thin film roll, thin film sheet), 4a... First layer resin (thin film sheet), 4b・
2nd layer resin, 5...metal plating or conductive paint,
6...Printed wiring circuit for ground.

Claims (1)

[Claims] (1) First, a conductor connected to the ground part of the printed wiring board is used to demarcate the range in which mutual electromagnetic interference is avoided in the electronic circuit of the printed wiring board, and the entire printed wiring board and the electronic circuit components mounted thereon are separated. The electrical conductor is covered with an insulating sealing resin or thin film seal that can be easily peeled off later, so that a part of the conductor is exposed from the sealing resin or thin film seal, and then the sealing An electromagnetic shielding method comprising coating a stopper resin or a thin film seal with metal plating or conductive paint so that the conductor can be contacted.