JPH02270390A - Printed wiring board provided with shielding layer - Google Patents

Abstract

PURPOSE:To enable the formation of an electromagnetic wave shielding layer even on a conduction through-hole by a method wherein sealing member high in heat and weather resistance is filled into the conduction through-hole, and the electromagnetic wave shielding layer is formed through the intermediary of an insulating layer. CONSTITUTION:A printed wiring circuit composed of required patterns is formed on both the sides of an insulating board 1 through the intermediary of a plating through-hole 8. A sealing member 3a is formed in such a manner that paste formed of photocuring synthetic resin material is filled into conduction through-holes 7 and set. An insulating layer 4 is formed through a screen printing or the like, an electromagnetic wave shielding layer 5 is deposited on the layer 4, and a solder resist layer 6 serving also as a protective layer of the electromagnetic wave shielding layer 5 is formed. It is preferable that the thickness of the insulating layer 4 is set to 20-50mum, and a relief part 40 shaped like a saucer is formed above a connection land 20 between the shielding layer 5 of the printed wiring circuit and an earth circuit 5a as shown in a figure b. Then, the earth circuit 5a of the connection land 20 is formed through the intermediary of the relief part 40 at a time with the formation of the shielding layer 5. Therefore, a high shielding effect can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to printed wiring boards.

[Conventional technology]

Conventionally, a method of providing an electromagnetic shielding layer on a printed wiring board via an insulating layer is described in Japanese Patent Application Laid-Open No. 62-213192 and is known. An electromagnetic shielding layer 5 is provided on the wiring circuit 2 via an insulating layer 4, and a solder resist layer 6 is also provided.
By providing the reprint wiring board 9, the reprint wiring board 9 is constructed.

In addition, the electromagnetic shielding layer 5 in the printed wiring board 9
Through-hole part 7 for conduction by plated through-hole 8
or, although not shown, is formed in a portion excluding component connection lands and the like.

[Problem to be solved by the invention]

In a conventional printed wiring board 9 provided with a shield layer 5, an insulating layer 4 is formed by screen printing on the printed wiring circuit 2 and the shield layer 5, especially on the printed wiring circuit 2. As shown in the figure, a relief part 40 having the same diameter (for example, φ3 m) as the connection land 20 is provided on the upper side of the connection land 20 with the shield layer 5 in the printed wiring circuit 2. When the shield layer 5 is formed, the ground circuit 5a is formed at the same time.

However, between the escape portion 40 formed on the upper side of the connection land 20 and the insulating layer 4, there is a step corresponding to the layer thickness of the insulating layer 4 formed on the upper side of the printed wiring circuit 2, which is normally formed by screen printing. When the thickness of the outer circumferential portion 5b of the ground circuit 5a of the shield layer 5 is thin compared to the thickness of the other shield layers 5, the shield ink may not flow smoothly into the relief portion 40, causing scratches, etc. This has the disadvantage that formation of an appropriate grounding circuit 5a is impaired.

In addition, the escape portion 40 has a ground circuit 5a having a film thickness greater than necessary.
(For example, if the thickness of the shield layer 5 is around 20 μm, a ground circuit 5a having a thickness of around 50 μm is usually formed in the relief portion 40.) As a result, the thicker the coating, the less flexible and brittle it becomes. (For example, thermal expansion at solder tip,
There is a drawback that cracks may occur in the ground circuit 5a during shrinkage).

Furthermore, printed wiring Fi provided with this kind of shield layer 5
In order to effectively obtain the shielding effect in 9, the insulating layer 4 interposed between the printed wiring circuit 2 and the shield layer 5 must be
It is necessary to apply an appropriate layer thickness.

In other words, if the thickness of the insulating layer 4 is thin, the electric properties, withstand voltage characteristics and insulation characteristics will deteriorate, and current will flow through the printed wiring circuit 2, causing a seat.
The operating characteristics of the printed wiring circuit 2 and the shield layer 5 will be impaired, leading to a deterioration of the quality of the printed wiring board itself.On the other hand, if the layer thickness is too thick, a step will occur between the printed wiring circuit 2 and the shield layer 5, and the ground circuit 5a provided between the two will be damaged. This method has drawbacks such as poor connections.

Therefore, the present invention was developed in view of the shortcomings in conventional printed wiring boards, and an object of the present invention is to provide a printed wiring board having a good electromagnetic shielding effect.

[Means to solve the problem]

The printed wiring board of the present invention is a printed wiring board in which a printed wiring circuit is provided on one or both sides of an insulating board, and a shield layer is provided on the upper side of the printed wiring circuit with an insulating layer interposed therebetween. The insulating layer is filled with a heat-resistant and weather-resistant sealing member, and the thickness of the insulating layer is 20 to 50 μm. This feature is characterized in that it is constructed by providing a relief portion in the form of a shape.

[For production]

The printed wiring board of the present invention is a printed wiring board in which a printed wiring circuit is provided on one or both sides of an insulating board, and a shield layer is provided on the upper side of the printed wiring circuit with an insulating layer interposed therebetween. By filling a weather-resistant sealing member and forming an electromagnetic shielding layer via an insulating layer, it is possible to form an electromagnetic shielding layer also on the conductive through-hole portion.

Further, the electromagnetic shielding layer is not divided by the conduction through-hole portion, and the effective area of the electromagnetic shielding layer can be increased.

Furthermore, by forming the insulating layer with a thickness of 20 to 50 μ-, it is possible to obtain an appropriate operation of the printed wiring circuit and an appropriate shielding effect of the shield layer, and also to provide a shield between the printed wiring circuit and the shielding layer. By forming a ground circuit through the cup-shaped escape part formed above the connecting land between layers, it is possible to prevent the ground circuit from fading or from becoming thicker than other shield layers and becoming brittle. It may be possible to form a shield layer.

〔Example〕

Embodiments of the printed wiring board of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a partially enlarged sectional view showing a first embodiment of the printed wiring board of the present invention. Reference numeral 1 denotes an insulating plate on which a reprinted wiring circuit 2 is formed from a desired pattern on both sides through plated through holes 8.

Further, 3a is a sealing member filled in the conductive through-hole portion 7, and the sealing member 3a is made of a thermosetting synthetic resin material such as epoxy resin or a photocuring synthetic resin material such as acrylic epoxy resin. It is what it is. The base made of these synthetic resin materials is filled into each conductive through-hole portion 7 of the reprinted wiring board 9 by means such as screen printing, and then cured.

Furthermore, after forming an insulating layer 4 by screen printing or the like, and forming an electromagnetic shielding layer 5 on top of this insulating layer 4,
A solder resist layer 6 which also serves as a protective layer for the electromagnetic shield layer 5 is formed.

The insulating layer 4 is desirably formed to have a layer thickness of 20 to 50 μm, and in particular, the upper side of the connecting land 20 between the shield layer 5 of the printed wiring circuit 2 and the earth circuit 5a has a layer thickness of 20 to 50 μm. As shown in the figure, a cup-shaped relief part 40 is formed.

Thereafter, a ground circuit 5a with the connection land 20 is formed simultaneously with the formation of the shield layer 5 via this cup-shaped escape part 40.

Therefore, as shown in FIG. 1C, by forming the ground circuit 5a through the cup-shaped relief part 40,
It is possible to make the layer thicknesses of a and the shield layer 5 uniform, and also to make the film thicknesses of the outer and inner peripheral parts of the connection land 20 uniform by eliminating the step difference due to the cup-shaped shape. This makes it possible to form a grounding circuit 5a.

Furthermore, in forming the cup-shaped relief portion 40, screen printing is mainly employed when forming the insulating layer 4. Instead of forming the insulating layer 4, screen printing is performed a plurality of times to form the insulating layer 4 with a desired thickness.

In particular, the relief portion 4 on the upper side of the connection land 20
0, when the insulating layer 40 is formed by screen printing a plurality of times, a relief part 40 having the same diameter as the connection land 20 is screen printed during the first screen printing, and thereafter, the connection land is sequentially formed. The stage where the diameter becomes larger than the diameter of 20.

A cup-shaped relief part 40 is formed by performing screen printing.
can be formed appropriately.

For example, when the thickness of the insulating layer 4 is 45 μ-, it is sufficient to form a layer with a thickness of 15 μ- three times in one printing, and the first
For example, if the diameter of the connecting land 20 is 3 mm, the diameter of the second relief part 40 is the same as that, and the second relief part 40 is the same diameter.
0 diameter is 3.1 m, and the third relief part 40 diameter is 3.2 m.
When forming the insulating layer 4 on the upper side of the connection land 20 by a method such as am, a cup-shaped relief part 40 can be formed.

Therefore, when the ground circuit 5a is formed with the connection land 20 through the cup-shaped relief portion 40, a smooth slope is formed from the outer circumference of the relief portion 40 toward the inner circumference. A shield paste for screen printing of the shield layer 5 is applied along this slope, and the film thicknesses of the ground circuit 5a and the shield M5 are also made uniform.

(Second Embodiment) FIG. 2 is a partially enlarged sectional view showing a second embodiment of the printed wiring board of the present invention.

Therefore, in this embodiment, the sealing member of the printed wiring board 9 in the first embodiment is made of a conductive synthetic material containing carbon, silver, copper, etc. That is, since electrical conduction can be established between both surfaces of the reprinted wiring board 9 by the conductive sealing member 3b, it is not necessarily necessary to plate the conductive through-hole portions 7.

It should be noted that other components in the configuration that are the same as those in the first embodiment are given the same numbers, and their explanations will be omitted.

In addition, in the above steps, each step of forming the insulating layer 4, the electromagnetic shield N5, and the solder resist layer 6 is performed by a conventionally known method, and the explanation of the specific method is omitted and is limited to this method. Needless to say, it can be formed by various other known methods.

(Effects of the Invention) According to the printed wiring board of the present invention, by filling the conduction through-hole portion with a heat-resistant and weather-resistant sealing member and forming an electromagnetic wave shielding layer through an insulating layer, Since an electromagnetic wave shielding layer can be formed also on the hole portion, it is possible to prevent the influence of electromagnetic waves, which are passive and active noise, even on the conductive through-hole portion.

In addition, the electromagnetic shielding layer is not divided by the conduction through-hole portion, and the effective area of the shielding layer can be increased, making it possible to provide a printed wiring board with extremely good electromagnetic shielding effect. It is.

Furthermore, by setting the absolute uM layer thickness formed between the printed wiring circuit and the shield layer in a printed wiring board equipped with a shield layer to 20 to 50μ steel, the proper operation of the printed wiring circuit and the connection between the printed wiring circuit and the shield layer are ensured. The difference in level can be minimized, and a ground circuit between the two can be formed without defects.

In addition, according to the printed wiring board of the present invention, it is possible to appropriately form a ground circuit when forming a shield layer, and to form a ground circuit with a film thickness equivalent to that of the shield layer, thereby providing printed wiring with high shielding effect and high durability. Boards can be provided.

[Brief explanation of drawings]

Figures 1a, b, and c are enlarged sectional views showing a first embodiment of the printed wiring board of the present invention, Figure 2 is an enlarged sectional view of a second embodiment of the printed wiring board of the present invention, and Figures 3a, b is an enlarged sectional view of a conventional printed wiring board. 1... Insulating plate 2... Printed wiring circuits 3a, 3b... Sealing member 4... Insulating layer 5... Electromagnetic wave shielding layer 5a... Earth circuit 6... Solder resist layer 7...・Through-hole portion for conduction 8 ・Plating through-hole 9 ・Printed wiring board 20 ・Connection land 40 ・Escape portion Patent applicant Nippon CMK Co., Ltd. Procedural amendment (
Method) % formula % 1. Indication of the case 1999 Patent layer No. 337194 2. Name of the invention Printed wiring board with a shield layer 3. Person making the amendment Relationship to the case Patent applicant address Miyoshi-cho, Iruma-gun, Saitama Prefecture Fujikubo 1106 Name: Japan CMK Co., Ltd. Representative: Noboru Nakayama 4, Agent: 105 Address: 2-2-15 Hamamatsucho, Minato-ku, Tokyo April 24, 1990 (Delivery) 7. Contents of amendment (1) The drawings of this application are amended as shown in the attached sheet. (2) Amend the document certifying the power of attorney as shown in the attached sheet. 8. List of attached documents m Amended drawings 1 copy (2) Power of attorney 1 mail order Top 1...Insulating plate 3a...Sealing member 4-Insulating layer 5...Electromagnetic wave shield layer 5a...Earth circuit 6 ... Solder resist layer 7 ... Through-hole section for conduction 8 ... Plating through-hole 9 ... Printed wiring board 20 ... Connection runt Fig. 1 (b) Fig. 1 (c) Fig. 2

Claims (3)

[Claims] (1) In a printed wiring board in which a printed wiring circuit is provided on one or both sides of an insulating board and a shield layer is provided on the upper side of the printed wiring circuit with an insulating layer interposed therebetween, a heat-resistant through-hole portion for conduction in the printed wiring circuit is provided. , filling a weather-resistant sealing member and forming the insulating layer with a thickness of 20 to 50 μm, and forming a cup-shaped relief part above the connection land of the printed wiring circuit when forming the insulating layer. What is claimed is: 1. A printed wiring board comprising a shield layer. (2) The printed wiring board having a shield layer according to claim 1, wherein the sealing member is made of a thermosetting synthetic resin or a photocuring synthetic resin material. (3) A printed wiring board with a shield layer according to claim 1, wherein the sealing member is made of a conductive synthetic resin material containing carbon, silver, copper, etc. and provides electrical continuity between both sides of the reprinted wiring board. .