JPH0766587A - Printed wiring board having magnetic coating film and electromagnetic wave shield layer and method for manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent noise such as crosstalk by sealing the magnetic field and electromagnetic waves generated from the circuit of the printed wiring board with one shield layer. [Structure] A magnetic field / electromagnetic wave shield layer 5 is provided on the surface of the single-sided plate on which the signal circuit 2 is formed via an insulating layer 4 and is connected to the earth circuit 3, and a magnetic field / electromagnetic wave shield layer 6 is directly provided on the back surface. Provided, magnetic field / electromagnetic wave shield layers 5, 6
An overcoat layer is provided on the surface. This magnetic field / electromagnetic wave shield layer has an initial permeability μ of 10 ² or more and a coercive force Hc.
[0e] contains a high-permeability magnetic powder having a value of 1 or less and a highly conductive copper powder or silver powder in an appropriate mixing ratio, and has conductivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board or a hybrid IC substrate and a multi-chip module substrate and a method for manufacturing the same, and more particularly to a printed wiring board which prevents crosstalk between circuits.

[0002]

2. Description of the Related Art In a printed wiring board, when a current is applied to a circuit formed on the surface of a substrate, a magnetic field is generated in the conductor of the circuit and an electromagnetic wave is generated by the magnetic field. Further, this magnetic field has a function of converting adjacent circuits into antennas. Since both the magnetic field and the electromagnetic wave affect the devices, they are sources of noise. That is, not only malfunctions and crosstalk phenomena occur between the circuits inside the device, but the same effect is exerted on external devices.

In order to prevent the influence of this electromagnetic wave, conventionally, as shown in FIG. 4, a paste mainly made of copper powder is provided on the surface of the signal circuit 32 formed on the surface of the insulating substrate 31 via the insulating layer 34. A printed wiring board is generally manufactured in which the electromagnetic wave shield layer 35 is formed to be connected to the earth circuit 33, and the electromagnetic wave shield layer 35 is overcoated with an overcoat 36 to insulate the surface of the electromagnetic wave shield layer 35. ing.

The invention disclosed in Japanese Patent Application Laid-Open No. 4-352498, which was developed for the purpose of sealing electromagnetic waves, is known. This invention develops a paste for forming a coating film for sealing the influence of electromagnetic waves generated from its own circuit on other devices and the influence of electromagnetic waves from other devices. This paste is
It contains soft magnetic powder having high magnetic permeability such as ferrite powder or iron alloy powder. When the electromagnetic wave is sealed by using this paste, the signal circuit formed on the substrate surface is covered with this paste.

[0005]

However, in the above-mentioned conventional electromagnetic wave shield layer mainly composed of copper powder, it is possible to prevent the electromagnetic wave generated from the own circuit from affecting other devices, but other It is difficult to effectively prevent the influence of electromagnetic waves from the above equipment.

Further, in the case of the paste described in Japanese Patent Application Laid-Open No. 4-352498, the method of forming a magnetic coating film suppresses the effects of electromagnetic waves generated from its own circuit and electromagnetic waves from other devices. This is performed in a complicated process of forming the signal circuit so as to wrap it.

Therefore, the present invention has been made in view of the above-mentioned problems of the prior art. The magnetic field and the electromagnetic wave generated in the circuit of the printed wiring board affect the inside and the outside equipment and the outside equipment. It is an object of the present invention to provide a printed wiring board that prevents noise such as crosstalk from occurring by preventing the printed wiring board from being affected by the above, and a method for easily manufacturing the printed wiring board.

[0008]

In order to achieve the above-mentioned object, the present invention provides a part or each of a surface on which a signal circuit is formed and a surface on which a signal circuit is not formed on the front and back surfaces of a printed wiring board. A magnetic coating film that absorbs a magnetic field is provided on the entire surface, and an electromagnetic wave shield layer that seals electromagnetic waves is provided at a required portion of the upper layer of the magnetic coating film,
Further, an overcoat layer is provided on the electromagnetic wave shield layer.

The magnetic coating film is mainly composed of a magnetic material made of a high magnetic permeability material having an initial magnetic permeability μ of 10 ² or more and a coercive force Hc [0e] of 1 or less. By having been completely covered with an insulating material such as resin or ceramic, it has an insulating property and also has a heat dissipation property.

According to this method for manufacturing a printed wiring board, an insulating material such as ceramic is provided on a part or all of the front surface and the back surface of the printed wiring board, the surface on which the signal circuit is formed and the surface on which the signal circuit is not formed. After applying a paste mainly composed of magnetic particles completely coated with, and then solidifying to form a magnetic coating film, after applying a paste mainly composed of copper to a required portion of the upper layer of the magnetic coating film It is characterized by being solidified to form an electromagnetic wave shield layer, connecting the electromagnetic wave shield layer to a ground circuit, and further providing an overcoat layer on the electromagnetic wave shield layer.

[0011]

According to the present invention, a magnetic coating film having a high magnetic permeability is provided on a required portion of the front and back surfaces of a printed wiring board to absorb a magnetic field, and an electromagnetic wave shield layer is provided on the magnetic coating layer to provide a signal circuit. Since the electromagnetic waves generated in the above are sealed, noise such as crosstalk can be effectively prevented.

Since the magnetic coating film is made insulative by completely covering the particles of the magnetic material having conductivity with an insulating material such as resin or ceramic, the insulating layer is not provided on the surface of the signal circuit. It can be formed directly without.

Since this magnetic coating film has a completely insulating property and a heat dissipation property, it can be used as a solder resist having both the purpose of magnetic field absorption and heat dissipation effect. Further, by filling the through holes with the paste mainly composed of the magnetic material having the insulating property, the magnetic field generated in the Z direction (the direction perpendicular to the substrate surface) is absorbed, and the magnetic field generated from the entire substrate is efficiently Can be absorbed.

[0014]

Embodiment 1 FIG. 1 shows Embodiment 1 of the present invention, in which a signal circuit 2 and a ground circuit 3 are formed on one surface (front side) of an insulating substrate 1, and the surface of the signal circuit 2 excluding the surface of the ground circuit 3. , And after directly applying the magnetic coating films 4 and 5 to the required portions of the back surface of the substrate 1 on which the circuits are not formed,
An electromagnetic wave shield layer 6 is applied to a required surface of the magnetic coating film 4 including the surface of the earth circuit 3 on the front side, the electromagnetic wave shield layer 6 is connected to the earth circuit 3, and an overcoat 8 is applied to the upper layer thereof to form an electromagnetic wave shield layer. 6 is a single-sided printed wiring board A formed so as to perform insulation protection on the surface of No. 6.

That is, this single-sided printed wiring board A absorbs the magnetic field generated from the signal circuit 2 from both sides by applying the magnetic coating films 4 and 5 on both sides thereof, and forms the signal circuit 2 with the electromagnetic wave shield layer 6. It is formed only on the front side to prevent the influence of electromagnetic waves.

[0016]

[Embodiment 2] FIG. 2 shows a single-sided printed wiring board B showing Embodiment 2 of the present invention.
5 is formed, electromagnetic wave shield layers 6 and 7 are formed on both sides, and the earth circuit 3 is connected.
9 is applied.

That is, in the single-sided printed wiring board B, the magnetic coating films 4 and 5 and the electromagnetic wave shield layers 6 and 7 are formed on the front and back surfaces of the substrate 1 to prevent the influence of the magnetic field and the electromagnetic waves on the front and back surfaces. Is.

[0018]

Third Embodiment FIG. 3 is a double-sided printed wiring board C showing a second embodiment of the present invention, in which signal circuits 12 and 1 are provided on both sides of a substrate 11.
3 and the ground circuits 14 and 15 are formed, and the through-holes 16 are formed to electrically connect the required circuits on the front and back sides through the through-hole plating 17.

In this embodiment, after the magnetic coating films 18 and 19 are applied to the required portions excluding the earth circuits 14 and 15, electromagnetic wave shield layers 20 and 21 are provided on the magnetic coating films 18 and 19 and are connected to the earth circuits 14 and 15. By applying overcoats 22 and 23 on the upper layers, the effects of the magnetic field and electromagnetic waves are completely prevented on the front and back surfaces.

The magnetic coating film 4 in Examples 1 to 3 above
5 and 18 and 19 are formed by using a paste mainly composed of particles of a magnetic material. This magnetic material has a high initial permeability μ of 10 ² or more and a coercive force Hc [0e] of 1 or less. Since it is made of a magnetically permeable material and has electrical conductivity, even if it is applied directly to the surface of the signal circuit by completely covering these particles with an insulating material such as resin or ceramic to make them electrically insulating, there will be problems. I try not to.

There are many kinds of magnetic materials having different characteristics. And, these magnetic materials must be selected from the types that provide the best effect on the performance required for equipment to which the magnetic coating films 3, 4 are applied, for example, television, audio and OA equipment. I won't.

For example, by using MnZn ferrite in the low frequency region, NiZn ferrite in the high frequency region, MnMg ferrite in the microwave region, etc., the magnetic field can be effectively absorbed depending on the frequency region required for these devices. .

Particularly for printed wiring boards, it is desirable to use a high magnetic permeability material having an initial magnetic permeability μ of 10 ² or more and a coercive force Hc [0e] of 1 or less. In addition, the magnetic material is not ferromagnetic but has a high magnetic permeability. In addition,
In the case of a ferromagnetic material, it has a strong coercive force, which may adversely affect crosstalk.

That is, those having a property of absorbing a magnetic field and demagnetizing, for example, MnZn ferrite, high purity Fe, FeNi
Materials with high magnetic permeability such as Mo (permalloy) and sendust are suitable.

The initial permeability μ of the magnetic material is 10 ² or less,
In addition, when the coercive force Hc [0e] is 1 or more, the magnetic field absorption is poor, and when this is used, noise cannot be completely prevented.

In order to effectively utilize the above-mentioned action of high magnetic permeability, in the present invention, two types of magnetic coating films, that is, an ultraviolet-curing type magnetic coating paste and a thermosetting type magnetic coating paste shown below are used. Was developed.

In this example, a printed wiring board was manufactured using these pastes, and its performance was confirmed. The compounding components of the developed paste and the method of forming the magnetic coating film are shown below.

The compounding components of the UV-curable magnetic coating film paste are as follows. Epoxy acrylate resin 30.0 wt
% Special acrylate resin 10.0 wt
% Acrylic reaction diluent 17.4 wt
% Acrylic modifier 4.0 wt
% Permalloy (FeNiMo) 36.2 wt
% Antifoam leveling agent 1.2 wt
% Photosensitizer 1.2 wt
%

This paste is applied to a required portion of a printed wiring board, and then the high pressure mercury lamp 3 of 80 W / Cm ² is applied.
Approximately 3 at a speed of approximately 4 m / min in the furnace irradiated with a lamp.
A cured magnetic coating film is formed by running for 0 seconds.

The compounding components of the thermosetting type magnetic coating paste are as follows. Epoxy resin 36.0 wt
% MnZn ferrite 42.7 wt
% Antifoam leveling agent 0.3 wt
% Organic solvent 18.0 wt
% Curing agent 3.0 wt
%

This paste is applied to a required portion of a printed wiring board and then heated at 150 ° C. for 30 minutes in an oven.
A heated magnetic coating film is formed by heating for a minute.

These two types of paste for magnetic coating film are mainly composed of a magnetic material of a high magnetic permeability material having an initial magnetic permeability μ of 10 ² or more and a coercive force Hc [0e] of 1 or less,
Moreover, the magnetic material contained in this paste is in a state of being completely covered with an insulating material such as resin or ceramic.

Therefore, this magnetic coating paste is
Since it also has the performance as an insulating layer completely, even if the magnetic substance is exposed on the surface of the magnetic coating film and comes into contact with the pattern surface made of a conductor, there is no problem in insulation.

In addition, a through hole (not shown) is generated in the Z direction (a direction perpendicular to the substrate surface) by selectively filling a required through hole with a paste mainly containing a magnetic material. It can absorb the magnetic field. Thereby, the magnetic field generated from the entire substrate can be efficiently absorbed and the electromagnetic wave can be sealed. Further, since this magnetic coating film has a heat dissipation property, it is possible to exert a heat dissipation effect as well as to absorb a magnetic field by being directly applied to the conductor surface.

Using this paste, the signal circuit 2 or 1
After the magnetic coating films 3 and 4 are formed directly on the surfaces on which the surfaces 2 and 13 are formed and the back surface on which the circuit is not formed, on the required portions of the respective surfaces, the magnetic coating films 4 and 5 or 18 and 1 are further formed.
The electromagnetic wave shield layers 5 and 6 are formed directly on the upper layer of 9 and are connected to the earth circuit 3 or 14, 15.

This electromagnetic wave shield layer has been conventionally used generally, and its components are as follows. Electrolytic copper powder 80.0 wt% Modified phenolic resin 15.0 wt% Dispersant and additive 0.5 wt% Solvent 4.5 wt%

The printed wiring board in this embodiment is not limited to the single-sided printed wiring board. Further, the components of the paste for the magnetic coating film and the curing method shown in this example are
Various changes can be made without departing from the scope of the claims of the present invention.

[0038]

According to the printed wiring board having the magnetic coating film and the electromagnetic wave shield of the present invention and the manufacturing method thereof,
The magnetic coating absorbs the magnetic field by applying the magnetic coating and the electromagnetic shielding layer to the required parts on the front and back of the printed wiring board, and the electromagnetic shielding layer seals the electromagnetic waves generated from the circuit to the inside and outside equipment. It is possible to effectively prevent the generation of noise such as crosstalk by preventing the influence on the external device and the influence from the external device.

Further, since the particles of the magnetic material, which is the main component of the magnetic coating paste of the present invention, have an insulating property by being covered with an insulating material such as resin or ceramic,
The magnetic coating layer can be formed directly on the surface of the signal circuit, and even if the magnetic material is exposed on the surface of the magnetic coating, the magnetic material itself does not adversely affect the insulation between the patterns.

Furthermore, since the magnetic coating film has a perfect insulating property, the magnetic coating film can be directly formed on the circuit as an insulating layer or as a solder resist.
Therefore, construction is easy and the number of steps can be reduced.

On the other hand, the heat generated from the conductor can be dissipated by the heat dissipation of the magnetic coating film, and the magnetic field in the Z direction can be absorbed by filling the through hole with a magnetic material.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a single-sided printed wiring board having a magnetic coating film and an electromagnetic wave shield layer showing Example 1 of the present invention.

FIG. 2 is a cross-sectional view of a single-sided printed wiring board having a magnetic coating film and an electromagnetic wave shield layer showing Example 2 of the present invention.

FIG. 3 is a cross-sectional view of a double-sided printed wiring board having a magnetic coating film and an electromagnetic wave shield layer showing Example 3 of the present invention.

FIG. 4 is a sectional view of a printed wiring board having a conventional electromagnetic shield layer.

[Explanation of symbols]

 1,11 Insulating substrate 2,12,13 Signal circuit 3,14,15 Earth circuit 4,5,18,19 Magnetic coating film 6,7,20,21 Electromagnetic wave shield layer 8,9,22,23 Overcoat 16 Through Hole 17 Through hole plating

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Ichikawa 1106 Fujikubo, Miyoshi-cho, Iruma-gun, Saitama Prefecture Japan CMC Co., Ltd. (72) Yoshio Nishiyama 1106 Fujikubo, Miyoshi-cho, Iruma-gun, Saitama Japan Share Company (72) Inventor Yuichi Koinuma 1106 Fujikubo, Miyoshi-cho, Iruma-gun, Saitama Japan CMK Corporation

Claims (4)

[Claims] 1. A magnetic coating that absorbs a magnetic field is provided on a part or all of a surface on which a signal circuit is formed and a surface on which a signal circuit is not formed, on the front and back surfaces of a printed wiring board, and Providing an electromagnetic wave shield layer that shields electromagnetic waves in the required part of the upper layer of the coating film,
A printed wiring board having a magnetic coating film and an electromagnetic wave shield layer, further comprising an overcoat layer provided on the electromagnetic wave shield layer. 2. The magnetic coating film is mainly composed of a magnetic material made of a high magnetic permeability material having an initial magnetic permeability μ of 10 ² or more and a coercive force Hc [0e] of 1 or less. A printed wiring board having the magnetic coating film according to claim 1 and an electromagnetic wave shield layer. 3. The magnetic coating film and the electromagnetic wave shield layer according to claim 1, wherein the magnetic material has an insulating property and a heat dissipation property by being completely covered with an insulating material such as resin or ceramics. A printed wiring board having. 4. A magnetic body in which a surface on which a signal circuit is formed and a surface on which a signal circuit is not formed on the front and back surfaces of a printed wiring board are completely covered with an insulator such as ceramics. And then solidify to form a magnetic coating film after applying a paste containing copper as a main component, and apply an paste containing copper as a main component to a required portion of the upper layer of the magnetic coating film and then solidify to form an electromagnetic shield layer. A method for producing a printed wiring board having a magnetic coating film and an electromagnetic wave shield layer, which is produced by connecting the electromagnetic wave shield layer to a ground circuit and further providing an overcoat layer on the electromagnetic wave shield layer.