JPH02272788A - Manufacture of radio wave shielding printed circuit board - Google Patents

Abstract

PURPOSE:To improve reliability by forming an etching resist layer in a range of 80% or more of a circuit pattern, partly exposing an insulating layer, and then forming a solder resist layer. CONSTITUTION:An insulating layer 2 of resin composition is formed in a range except a through hole 3 on a substrate formed with a wiring circuit 1. Then, an electromagnetically shielding layer 4 such as a copper layer, a nickel layer, a nickel-copper layer, etc., is formed on a whole circuit board, with thickness being approx. 0.1-1.0mum. Then, an etching resist layer 5 is formed on the layer 4, the exposed layer 4 is removed by etching, and an exposed part 6 is provided. The layer 5 is desirably formed to generate as many parts 6 as possible to cover an area of 80% or more of the channel pattern, and the area of the part 6 is suitably 5% or more of the entire substrate. Then, a solder resist layer 7 is formed thereon. Thus, the layers 2, 7 are coupled at the part 6, and the layer 4 is secured and stabilized between the layers 2 and 7, preventing the layers 4, 7 from deviating and thereby obtaining high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a radio wave shielding printed wiring board.

Conventional technology and its problems Malfunctions of computers, electronic devices, etc. caused by electromagnetic waves have become a problem. In order to prevent the electromagnetic waves generated by the electromagnetic waves from interfering with other parts, shielding of the source of the electromagnetic waves is performed.

Conventional electromagnetic shielding methods include making the outer or inner surface of the case of an electronic device a conductor, and wrapping a component such as a printed wiring board with a laminated film of a conductive film and a plastic film. However, with these methods, it may be difficult to make the case conductive, or the reliability and stability of the shielding effect may be insufficient.

Means for Solving the Problems In view of the above-mentioned problems, the present inventor has conducted extensive research and has devised a method for laminating a resin layer and an electromagnetic shielding layer on a printed wiring board using a specific process. By using this method, it is possible to obtain a printed wiring board having a stable shield layer fixed between the resin layers, and the obtained printed wiring board itself has an extremely reliable radio wave blocking function. It was discovered that it could be used as a printed wiring board.

That is, the present invention forms an insulating layer on a printed wiring board,
Next, after forming an electromagnetic shielding layer, an etching resist layer is formed on the shielding layer in a range covering 80% or more of the area of the circuit pattern, and then the exposed portion of the electromagnetic shielding layer is etched away. The present invention relates to a method for manufacturing a radio wave shielding printed wiring board, characterized in that a solder resist layer is formed after partially exposing an insulating layer.

Hereinafter, the method for manufacturing a printed wiring board of the present invention will be explained in the first part.
This will be explained with reference to the process diagram shown in the figure.

FIG. 1(a) is a sectional view of a printed wiring board (double-sided board) on which a wiring circuit (1) made of copper foil is formed. In the present invention, any conventionally used printed wiring board can be used. For example, as a board material,
Using paper-based phenolic resin copper-clad laminates, paper-based epoxy resin copper-clad laminates, glass cloth-based epoxy resin copper-clad laminates, etc., it is possible to use screen printing methods, photoprinting methods, subtractive methods, additive methods, etc. A wiring circuit formed by a known method can be used.

In the method of the present invention, first, an insulating layer (2) made of a resin composition is formed on a printed wiring board (FIG. 1(b)). As the resin composition for forming the insulating layer (2), it is preferable to use a resin composition commonly known as a solder resist from the viewpoints of applicability, adhesion, heat resistance, etc. There are no particular limitations on the method of forming an insulating layer using a solder resist, and any conventionally known method can be applied, for example,
A pattern forming method using a screen printing method using a solvent-free photosensitive liquid resist called UV solder resist, a pattern forming method using a photographic method using a solvent-free liquid solder resist, a pattern forming method using a photographic method using a solvent-type liquid solder resist , an insulating layer formation method using dry film solder resist, etc. can be adopted. The area where the insulating layer (2) is formed is the circuit pattern area, the through-hole area, excluding the through-hole area (3) for mounting components, lead terminals, etc. on the circuit surface of the printed wiring board.
The range may be set so that the land portion etc. can be sufficiently covered. The thickness of the insulating layer (2) may be set to a thickness that can ensure sufficient insulation depending on the type of resin used, and is usually 20 to 1.
The thickness may be approximately 00 μm.

Next, an electromagnetic shielding layer (4
) (Figure 1 (c)). Electromagnetic shield layer (4)
For example, a conductor layer formed by a dry plating method such as vapor deposition or sputtering, or a wet plating method such as electroless plating or electroplating can be used as a conductor layer having a shielding effect. . especially,
The wet plating method is advantageous in that it is easy to process and has excellent mass productivity. Wet plating methods include methods of applying electroless copper plating, electroless nickel plating, etc. alone, methods of laminating different types of electroless plating films, and methods of performing electroplating after electroless plating. Can be adopted as appropriate. Examples of the electromagnetic shield layer (4) include a copper layer, a nickel layer, a copper-nickel layer, a nickel-copper layer, and the like. The method for forming the shield layer (4) may be according to a known method. For example, in the electroless plating method, after imparting catalytic properties to the object to be treated according to a conventional method, it is added to a plating solution according to ordinary conditions. A method of immersion is sufficient. The thickness of the electromagnetic shielding layer (4) may be appropriately set so as to be thick enough to obtain the required shielding effect, and is usually about 0.1 to 1.0 μm. The shielding effect may be better with a multi-layer shield layer than with a single-layer shield layer, for example, Cu
For a single layer of 1 μm, the frequency is 100 MHz and about 20 dB.
Cub, 5μm-Ni
100MHz 60dB with 0.5μm multilayer shield layer
A certain degree of shielding effect can be obtained.

After forming the electromagnetic shield layer (4), an etching resist layer (5) is formed on the shield layer.
), the exposed shield layer is removed by etching to provide a partially exposed portion (6) of the insulating layer (FIG. 1(e)). Next, by forming a solder resist layer (7) on this, the insulating layer (2) and the solder resist layer (7) are strongly coupled by the exposed portion (6) of the insulating layer, and the electromagnetic shielding layer (4) ) is wrapped and fixed between the insulating layer (2) and the solder resist layer (7) and stabilized, preventing the shield layer (4) and the resist layer (5) from shifting (see Figure 1 ( fart)).

The area of the exposed portion (6) is not particularly limited, but if the area of this portion is increased, the bond between the insulating layer (2) and the solder resist layer (7) becomes stronger, and the shield layer (4)
and the resist layer (5) can be stably fixed. On the other hand, in order to obtain an effective shielding effect, it is preferable that the electromagnetic shielding layer (4) be present on a portion having an area of 80% or more on the circuit pattern (1) of the printed wiring board. Therefore, it is preferable that the etching resist layer (5) be formed so as to cover 80% or more of the area on the circuit pattern portion of the printed wiring board, and to expose as much of the insulating layer (2) as possible. From this point of view, the formation range of the etching resist layer (5) may be determined as appropriate depending on the shape of the circuit pattern. Normally, it is appropriate that the area of the exposed portion (6) of the insulating layer (2) is approximately 5% or more of the entire substrate. Since the etching resist layer (5) ultimately remains on the printed wiring board, it is required to have heat resistance, moisture resistance, etc., as well as good applicability, adhesion, etc. Therefore, as the resin composition for forming the etching resist layer (5), it is preferable to use the resin composition generally known as a solder resist as described above.

The etching resist layer (5) only needs to have a sufficient thickness to protect the electromagnetic shielding layer (14) during etching, and usually has a thickness of about 5 μm or more.

Etching of the electromagnetic shielding layer may be carried out according to a conventional method depending on the type of metal of the shielding layer.

Generally, the thickness of the shield layer (4) is 0.1 to 1.0 μm.
The conductor film thickness of the wiring circuit part (usually 20 to 30μ
The shield layer (4) can be etched by using a so-called soft etching method without almost corroding conductors such as through holes. For example, hydrogen peroxide
Sulfuric acid-based etching solution (for example, Nokku, 0A91)
etc.) for about 10 to 20 seconds.

By etching the shield layer (4), the insulation layer (2)
is partially exposed, and the solder resist layer (7) formed thereon is bonded to the insulating layer (2) through the exposed portion (6), thereby preventing the shield layer (4) from shifting. The solder resist layer (7) may be formed using a known resin composition for solder resists in accordance with a conventional method except for through holes for mounting components, lead terminals, etc. The thickness of the solder resist layer (7) is not particularly limited, but in the portion where the shield layer (4) is formed, it is 5 to 20 μm.
Generally, the thickness is approximately 10 μm or more in the portion (6) where the shield layer is etched away.

Effects of the Invention The radio wave shielding printed wiring board obtained by the present invention has an electromagnetic shielding layer on the wiring board itself, and the shielding layer is stably fixed between the resin layers, so that it is resistant to the influence of external electromagnetic waves and self-sustaining. This is an extremely reliable printed wiring board that can suppress the generation of electromagnetic waves.

Example Hereinafter, the present invention will be explained in more detail by showing examples.

Example 1 A radio wave shielding printed wiring board was manufactured by the following steps using a printed wiring board manufactured by the screen printing method shown in FIG. 2(A). In the figure, the black part is the conductor part.

(A) Insulating layer formation: Solvent developable liquid photo solder resist (trademark 2PSR)
-1000, manufactured by Taiyo Ink Manufacturing ■) on the wiring board,
After preliminary drying at 80°C for 25 minutes, exposure and development were carried out, followed by main drying at 150°C for 50 minutes.
An insulating layer having the pattern shown in Figure (b) was formed. The white part was the insulating layer part, and the film thickness was 40 μm.

(B) Formation of electromagnetic shield layer: An electroless copper plating film having a thickness of 0.5 to 1 μm was formed on the entire surface of the printed wiring board on which the insulating layer was formed. As a plating solution, thick electroless copper plating solution (copper sulfate 8-12g/12.E
, D, T, A, 25-35g/Q, formalin (37%
)5-10m (2/Q, sodium hydroxide 5-8, some amount of sex agent), pH 12-13, liquid temperature 40-60
Plating was carried out at 15 to 30 minutes.

(C) Etching resist layer formation: Using the liquid photoresist used to form the insulating layer, (
An etching resist layer was formed in the same manner as in step A). The pattern of the resist layer was as shown in FIG. 2 (c) (the white part is the resist layer), and the thickness was 16 μm.

(D) Etching: While the substrate is moved at a constant speed on a roller, a hydrogen peroxide-sulfuric acid based soft etching solution is applied at 1 kgf/c using a device that can spray etching solution from the top and bottom surfaces.
Etching was carried out by spraying both sides of the substrate for 15 seconds at a pressure of m2.

(E) Solder resist formation: (A)
A solder resist layer was formed in the same manner as in the step. The pattern of the solder resist layer was as shown in FIG. 2 (2) (the white part is the resist layer), and the thickness was 25 μm.

The radio wave shielding effect of the printed wiring board obtained through the above process was tested in the following manner.

That is, after predetermined components were mounted on the wiring board, a high frequency of 5 MHz was input in a shielded room, and the generated radio waves were analyzed with a spectrum analyzer. Figure 3 shows the spectrum diagram of the radio waves generated for the wiring board used for comparison without the electromagnetic shielding layer, and Figure 4 shows the spectrum diagram of the radio waves generated for the wiring board with the shielding layer of 0.5 μm. FIG. 5 shows a spectrum diagram of radio waves generated for a wiring board provided with a 1 μm shield layer. By comparing FIGS. 3 to 5, it can be seen that a large radio wave shielding effect can be obtained in the wiring board provided with the shield layer by the method of the present invention.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the process of the present invention, FIG. 2 is a drawing showing the pattern of the printed wiring board manufactured in Example 1, and FIG. 3 is a diagram showing the generated radio waves for a wiring board without a shield layer. The spectrum diagram, Figure 4 is 0. 5 μm
FIG. 5 is a spectrum diagram of generated radio waves for a wiring board provided with a shield layer of 1 μm. FIG. 5 is a spectrum diagram of radio waves generated for a wiring board provided with a 1 μm shield layer. DESCRIPTION OF SYMBOLS 1... Wiring circuit, 2... Insulating layer, 3... Through hole, 4... Electromagnetic shielding layer, 5... Etching resist layer, 6... Insulating layer exposed part, 7... solder resist layer. (more details)

Claims (1)

[Claims] 1. After forming an insulating layer on a printed wiring board and then forming an electromagnetic shielding layer, an etching resist layer is formed on the shielding layer in a range covering 80% or more of the area of the circuit pattern, and then A method for manufacturing a radio wave shielding printed wiring board, comprising: etching away the exposed portion of the electromagnetic shield layer to partially expose the insulating layer, and then forming a solder resist layer.