JP2000059030A - Printed circuit board with electromagnetic wave shielding material and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a printed circuit board with an electromagnetic wave shielding material, which can form a flexible electromagnetic wave shielding material at low cost. A substrate b provided with a circuit pattern 12a
The electromagnetic wave shielding material A made of the metal foil mesh 3a was provided on both sides of. The metal foil can be flexibly configured by utilizing the flexibility of the metal foil, and the production cost can be reduced because the metal foil is inexpensive and can be mass-produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flexible printed wiring board (FPB), a flexible copper-clad laminate (FC)
L), FPB (FPC) based on polyimide resin,
The present invention relates to a printed circuit board with an electromagnetic wave shielding material such as a printed wiring board (PWB) and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the increase in the frequency of electronic circuits such as computers, the problem of malfunctions and noise occurring in other electronic devices due to electromagnetic waves emitted from such electronic circuits has been regarded as a problem. For this reason, in recent years,
Countermeasures such as providing an electromagnetic wave shield in a casing for housing an electronic circuit have been taken. When an electromagnetic wave shielding material is provided on a printed circuit board such as an FPB, it must be flexible. Therefore, as a material for such an application, a material in which a metal fiber such as stainless steel is formed into a nonwoven fabric is considered.

[0003]

However, metal non-woven fabrics are complex and many in that metal fibers are cut into short lengths, uniformly dispersed in a binder, and then formed into a sheet, followed by sintering the fibers. There is a drawback in that it requires a process and is extremely expensive. Moreover, if the non-woven fabric is used, the fibers are separated and fall off to cause a short circuit, so that it is necessary to take countermeasures, and there are many problems. On the other hand, nonwoven fabrics with copper or nickel plated on the surface of polyester fiber are also provided,
Such a nonwoven fabric has a drawback that it is weak to bending and the surface plating is easily broken. Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printed circuit board with an electromagnetic wave shielding material capable of inexpensively forming a flexible electromagnetic wave shielding material and a method of manufacturing the same. .

[0004]

A printed circuit board with an electromagnetic wave shielding material according to the present invention is characterized in that an electromagnetic wave shielding material made of a metal foil mesh is provided on both sides of a substrate on which a circuit pattern is provided. In such a printed circuit board with an electromagnetic wave shielding material (hereinafter, simply referred to as a printed circuit), since the electromagnetic wave shielding material is provided on both sides of the circuit pattern, the shielding effect is satisfactory, and the electromagnetic wave shielding material is made of metal foil mesh. , It has sufficient flexibility, is thin, lightweight and inexpensive.

The present invention can be applied to, for example, a printed circuit board for connecting a main body of a notebook personal computer and a display. In such a case, the substrate and the electromagnetic wave shielding material are made of a flexible material. Is formed. Also,
In the use mode of the printed circuit board as described above, since the bending direction is constant, it is preferable that the strength of the electromagnetic wave shielding material has directivity. Specifically, the electromagnetic wave shielding material can be formed in a lattice shape including vertical and horizontal line portions, and the widths of the vertical and horizontal line portions can be different from each other. Then, by appropriately setting the direction of the electromagnetic wave shielding material according to the use state such as the state of action of the stress, it is possible to configure so as to withstand the stress with less material. Further, it is preferable to further laminate an insulating plate so as to sandwich the substrate since the insulating effect is further improved.

The pattern of the metal foil mesh in the present invention is arbitrary, and may be a simple lattice, honeycomb, or irregular pattern. In addition, as a material of the metal foil, a material manufactured by plastic working such as rolling, or an electrolytic copper foil can be used. It is preferable to use any metal foil that has been annealed for softening. Examples of a method of forming a metal foil mesh pattern include, for example, a method of punching holes by punching a metal foil made of a rolled material having a predetermined thickness. This is preferable because it is easy to arrange a large number of holes with high precision. Further, since a large number of holes are formed in the metal foil to form a mesh pattern, flexibility is greatly improved.

The material of the metal foil mesh in the present invention includes metals such as copper, iron, nickel, aluminum, gold, silver and platinum, and alloys of two or more of these metals (eg, copper-nickel alloy, stainless steel, etc.). Further, a metal-based material that can be formed into a foil, such as a metal compound, is used. In addition, a material whose surface has been subjected to plating treatment as necessary, such as for prevention of oxidation, can be used as appropriate. Particularly preferably, an alloy or a metal compound of copper, aluminum, iron, or nickel, which can be easily formed into a foil by rolling or the like, is preferable because it can be manufactured at low cost. The thickness is preferably as thin as possible, preferably 5 to 100 μm, more preferably 10 to 100 μm.
５０50 μm. The above-described printed circuit board with an electromagnetic wave shielding material of the present invention can be manufactured by laminating a metal foil mesh having the above-described mesh pattern on both sides of the substrate provided with the circuit pattern. Alternatively, by using the manufacturing method of the present invention described below, it can be manufactured in a small number of steps.

That is, in the method of manufacturing a printed circuit board according to the present invention, a metal foil is provided on both surfaces of a base, and (1) a metal foil on one surface is etched by a photoresist method to form a circuit pattern; 2) An electromagnetic wave shielding material having a mesh pattern is provided by etching the metal foil on the other surface by a photoresist method, and (3) an electromagnetic wave having a mesh pattern formed on the surface of the circuit pattern by the etching method. In a method of manufacturing a printed circuit board provided with a shielding material,
It is characterized in that the etching of (1) and the etching of (2) or (3) are performed simultaneously.

According to the above manufacturing method, since the mesh pattern of the electromagnetic wave shielding material and the circuit pattern or the mesh pattern of the other electromagnetic wave shield can be formed at one time, the number of steps can be reduced and the manufacturing cost can be reduced. it can. In general, it is simple and preferable to simultaneously perform the etching of (1) and the etching of (2).

[0010]

Next, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an electromagnetic wave shielding material used for a printed circuit board according to the first embodiment. This electromagnetic wave shielding material includes a metal foil mesh 3a in which a grid-like mesh pattern 40 is formed on the entirety of a flexible metal foil such as an electrolytic copper foil. As shown in FIG. 2, the mesh pattern 40 in this case includes a large number of square holes 41 regularly drilled in a metal foil and a line portion 42 which is a metal foil portion around the holes 41. Be composed. As the dimensions of the mesh pattern 40, for example, the width of the line portion 42 is 25 μm, one side of the hole 41 (pitch of the line portion 42) is 500 μm, and the aperture ratio is 91%. This electromagnetic wave shielding material can be elastically deformed or plastically deformed, and can be easily folded, rolled, or cut.
a.

Next, a method of manufacturing a printed circuit board using the electromagnetic wave shielding material, together with the method of manufacturing the electromagnetic wave shielding material, will be described with reference to FIGS.
First, as shown in FIG. 3, an adhesive layer 2a is provided on the surface of the base film 1. As the base film 1, PE
Various resin films such as T (polyethylene terephthalate) and polyimide are used, and the thickness is 25 to 100 μm.
m. As the pressure-sensitive adhesive for the pressure-sensitive adhesive layer 2a, an acrylic pressure-sensitive adhesive or the like is preferably used, and the thickness thereof is about 5 to 40 μm.

Next, an adhesive layer 2b is provided on the surface of the metal foil 3, and as shown in FIG. 4, the adhesive layer 2b and the pressure-sensitive adhesive layer 2a are bonded to each other. As the adhesive for the adhesive layer 2a, a thermosetting adhesive obtained by adding an elastomer to a resin such as epoxy or phenol is preferably used, and its layer thickness is about 5 to 40 μm. Note that only the adhesive layer 2b can be provided without providing the adhesive layer 2a.

Next, as shown in FIG. 5, a resist 4 is laminated on the surface of the metal foil 3. Next, as shown in FIG. 6, a film-shaped mask 5 on which a mesh pattern to be formed is printed as a light transmitting portion is laminated on the surface of the resist 4, and ultraviolet light is irradiated from above the mask 5. The thickness of the resist 4 is preferably about 10 to 25 μm.
The irradiation amount of the ultraviolet rays is preferably about 80 to 160 mj. The resist 4 in a portion corresponding to the light transmitting portion of the mask 5 is exposed by ultraviolet irradiation, and the exposed portion is printed on the metal foil.

Next, the mask 5 is removed, and the whole is immersed in a processing solution for resist removal such as sodium carbonate aqueous solution to remove the resist 4 in the unexposed portion, that is, the unprinted portion. Thus, the mesh pattern made of the resist 4 is developed on the surface of the metal foil 3 as shown in FIG. Next, the entire metal foil 3 corresponding to the undeveloped portion is etched as shown in FIG. 8 by immersing the whole in an etching solution (for example, a solution obtained by dissolving ferric chloride in hydrochloric acid). The metal foil mesh 3a is formed. Thereafter, the whole is immersed in a resist-removing treatment liquid such as a caustic soda diluent to remove the remaining resist 4 in the developing section as shown in FIG. Thus, the electromagnetic wave shielding material A is completed.

Next, the base film 1 is peeled off from the electromagnetic wave shielding material A and attached to both sides of the printed circuit board b or c to complete a printed circuit board (see FIG. 10). First, the printed board b has an adhesive layer 11 provided on the surface of the base film 10, a circuit pattern 12a is formed on the surface of the adhesive layer 11, and an insulating layer 13 and a cover film 14 are sequentially laminated on the surface. It is configured. As the base film 10, various resin films such as PET and polyimide are preferably used.
A thermosetting adhesive such as nitrile rubber phenol or polyamide phenol is used. For example, an electrolytic copper foil is brought into close contact with the adhesive layer 11 and heated and adhered to each other. Then, a circuit pattern 12a is formed by etching with the same photoresist as described above. In the insulating layer 13,
An adhesive such as an acrylic resin or a thermosetting adhesive obtained by adding an elastomer to a resin such as epoxy or phenol is preferably used. The cover film 14 is for ensuring insulation of the circuit pattern 12a, and is made of PET,
It is composed of various resin films such as polyimide.

Here, the printed circuit board c is made of an adhesive layer 11
Circuit pattern 1 directly on the base film 10 without using
This is different from the printed circuit board b in that 2a is formed. On the printed circuit board c, a copper foil layer is formed on the surface of the base film 10 by using means such as plating, sputtering, or vacuum deposition, and the copper foil layer is etched with the same photoresist as described above to form a circuit pattern 12a. To form

FIG. 11 shows the layer structure of printed circuit boards B and C completed from printed boards a and b. It is desirable to coat the surface of the metal foil mesh 3a, which is the outermost layer of the printed circuit boards B and C, with plating or resin, whereby the durability of the electromagnetic wave shielding material A can be increased. In FIG. 11, the adhesive layer 2b is
In order to indicate that heat curing has been performed, the display of the cross section is changed from a dot in the previous drawing to a diagonal line (similar display is performed in the following drawings).

In the printed circuit boards B and C, a single-layer circuit pattern 12a is provided.
As shown in (1), the circuit pattern 12a can be provided in two or more layers. FIG. 12A is a diagram in which an adhesive layer 11, a circuit pattern 12a, an insulating layer 13, and an electromagnetic wave shielding material A are sequentially laminated so as to sandwich the base film 10, and FIG. The circuit pattern 12a is provided directly on the base film 10 without being provided.

The printed circuit board shown in FIG. 13 has circuit patterns 12a directly provided on both sides of a base film 10, and four circuit patterns 12a are provided between the base films 10 with an insulating layer 15 interposed therebetween. is there. In this case, as the insulating layer 15, a core in which an adhesive is impregnated can be used. For example, glass epoxy, liquid crystal polymer impregnated with BT resin (Mitsubishi Gas Fold Max), or PPE impregnated with aramid (Matsushita Additive) can be used.

The above printed circuit boards are flexible and can be used for various applications. Further, since the electromagnetic wave shielding material A is laminated on both surfaces, the electromagnetic wave shielding property is extremely high. Further, since the cover film 14 is provided so as to sandwich the circuit pattern 12a, the insulating property is high, and the reliability as an electronic circuit is very high. In the printed circuit board shown in FIG. 13, the circuit pattern 12a is provided directly on the base film 10, but may be provided via the above-mentioned adhesive layer 11. Furthermore, it is also possible to provide the circuit pattern 12a in more layers.

Next, a method of manufacturing a printed circuit board according to the present invention will be described with reference to FIGS. First, FIG.
As shown in (A), the cover film 14, the adhesive layer 2
The electromagnetic wave shielding material having a layer structure consisting of b and the metal foil 3 is bonded to a printed circuit board material having a layer structure consisting of the adhesive layer 11 and the copper foil 12. Then, both sides are etched with a photoresist, and FIG.
(A) As shown in FIG.
From the copper foil 12 to form a circuit pattern 12a. In the state shown in FIG. 15A, since the adhesive layers 2b and 11 are thermally cured, the cross section is indicated by oblique lines.
Next, an insulating layer 13 is provided on the surface of the circuit pattern 12a, and an electromagnetic wave shielding material A 'having a layer configuration including a cover film 14, an adhesive layer 2b, and a metal foil mesh 3a is bonded to the surface of the insulating layer 13 by a lamination press. , FIG.
A printed circuit board shown in FIG.

The above is an example in which the metal foil mesh 3a and the circuit pattern 12a are provided on both surfaces of one cover film 14 with the adhesive layers 2b and 11 interposed therebetween, but both may be provided directly on the cover film 14. it can. Figures 14-16
14B shows such a manufacturing method. First, as shown in FIG. 14B, a metal foil 3 and a copper foil 12 are formed on both surfaces of a cover film 14 by a suitable means such as sputtering. Forming layer 3 and copper foil layer 12,
As shown in FIG. 3B, the metal foil mesh 3a and the circuit pattern 12a are formed by etching both surfaces thereof with a photoresist. Next, an insulating layer 13 is provided on the surface of the circuit pattern 12a, and the cover film 14, the adhesive layer 2b and the metal foil mesh 3a are formed on the surface of the insulating layer 13.
The electromagnetic wave shielding material A having a layer structure of is laminated by a lamination press to obtain a printed circuit board shown in FIG.

FIGS. 17 and 18 show examples in which only one layer of the cover film 14 is provided. First,
As shown in FIG. 17 (A), an electromagnetic wave shielding material having a layer configuration including the adhesive layer 2b and the metal foil 3 and a printed board material having a layer configuration including the cover film 14, the adhesive layer 11, and the copper foil 12 are used. to paste together. Then, both sides are etched with a photoresist, and FIG.
As shown in (B), the metal foil 3 to the metal foil mesh 3a
From the copper foil 12 to form a circuit pattern 12a. In the state shown in FIG. 3B, the adhesive layers 2b and 11 are shown by oblique lines because they have been thermally cured. Next, an insulating layer 13 is provided on the surface of the circuit pattern 12a.
A printed circuit board having only one layer of a cover film 14 as shown in FIG. 18 (A) as shown in FIG. Get.

Further, the printed circuit board shown in FIG. 18B has a circuit pattern 12 having a laminated structure shown in FIG.
The insulating layer 13 is provided on the surface of a, and the electromagnetic wave shielding material A having a layer configuration including the adhesive layer 2b and the metal foil mesh 3a is bonded to the surface of the insulating layer 13 by a lamination press.

FIG. 19 shows an example in which the widths of the line portions of the metal foil mesh of the electromagnetic wave shield are different from each other in the vertical and horizontal directions. In a use situation in which a tensile stress acts in the bending direction shown in the drawing, it is desirable to arrange the thick line portion in the bending direction as shown in FIG. Further, in a use situation in which the curvature of bending is large and considerable flexibility is required, it is desirable to arrange the thin line portion in the bending direction.

[0026]

Next, the effects of the present invention will be clarified by examples based on the present invention. [Example 1] An NBR-phenol-based adhesive layer was formed on one side of a copper foil having a thickness of 36 µm so that the thickness after drying became 20 µm, and after curing, an acrylic film was formed so that the thickness became 20 µm. PET with a release system after forming a pressure-sensitive adhesive layer
The films were laminated, and a grid-like mesh pattern was formed by a photoresist method to produce an electromagnetic wave shielding material as shown in FIG. The dimensions of the mesh pattern are such that the width of the line portion is 25 μm, one side of the hole (pitch of the line portion) is 400 μm, and the aperture ratio is 89%. The aperture ratio was calculated by the area ratio of the hole to the external area obtained by adding 面積 of the width (line width) of the metal foil around the hole to the area of the hole. A printed circuit board having the configuration (B) shown in FIG. 10 was prepared using the electromagnetic wave shielding material.

Example 2 An electromagnetic shielding material and a printed circuit board in Example 2 were produced in the same manner as in Example 1 except that the copper foil was changed to an aluminum foil, and the hole shape was changed to a hexagon. The dimensions of the mesh pattern are as follows: the diameter of the diagonal line of the hole is 400 μm, the width of the line portion is 30 μm,
6%.

Example 3 A copper foil was a stainless steel foil, a vertical line width was 25 μm, and a horizontal line width was 50 μm.
An electromagnetic wave shielding material and a printed circuit board in Example 3 were produced in the same manner as in Example 1 except that the diagonal diameter of the hole was 400 μm and the aperture ratio was 84%.

Example 4 An NBR-phenol-based adhesive was laminated on both sides of a polyimide film having a thickness of 50 μm, and a copper foil having a thickness of 18 μm was further adhered to cure the adhesive. After applying the resist to the copper foil on both sides, the circuit pattern was exposed on one side and the same mesh pattern as in Example 3 was exposed on the other side. Next, both sides of the developed sheet were simultaneously etched. Next, the electromagnetic wave shielding material obtained in Example 3 was bonded to the circuit pattern surface, and a printed circuit board was manufactured by the manufacturing method of the present invention.

Comparative Example 1 A commercially available wire mesh (mesh size: 200 mesh) was used as the electromagnetic shielding material in Comparative Example 1.

[Comparative Example 2] A commercially available light-transmitting conductive mesh obtained by electrolessly plating copper / nickel on a polyester core fiber (wire diameter: 43 μm, mesh size: 200 mesh, thickness: 66 μm)
m, trade name: Denzymesh MT3-100, manufactured by Nisshinbo Industries) was used as the electromagnetic wave shielding material in Comparative Example 2.

PET of the electromagnetic wave shielding material of each of the above embodiments
Samples of each example were obtained by removing the film and the adhesive layer to obtain a single metal foil mesh. For each of the samples of these examples and each comparative example, a spectrum analyzer TR4172 manufactured by ADVANTEST (Evaluation unit was T
R17301) was used to measure the electromagnetic wave shielding factor at 500 MHz. The results of the above test were as shown in Table 1 below.

[0033]

[Table 1]

As shown in Table 1, the electromagnetic wave shielding material produced in the example has a higher electromagnetic wave shielding property than the comparative example, and has a good electromagnetic wave shielding property when it is provided on both sides of a printed circuit board to form a printed wiring board. It is presumed to show sex.

[Bending test] The printed circuit boards of Examples 1 to 3 and the printed circuit board of Example 4 (length 20c)
mm × 10 cm in width). Next, a bending test was performed in which both ends of the printed circuit board were adjusted 10,000 times at a rate of twice a minute, and then the state of the metal foil mesh was observed. As a result, no damage or plastic deformation was observed on the metal foil mesh, and it was confirmed that the metal foil mesh had sufficient flexibility.

[0036]

As described above, according to the printed circuit board of the present invention, since the electromagnetic wave shielding material made of a metal foil mesh is provided on both sides of the circuit pattern, the shielding effect is satisfactory and the flexibility is high. The effect is that it is sufficient, thin and lightweight, and can be manufactured at a low price with few manufacturing steps.

[Brief description of the drawings]

FIG. 1 is a plan view conceptually showing an electromagnetic shielding material for an electric component according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion II in FIG.

FIG. 3 is a conceptual diagram of a first step in a preferred method for manufacturing an electromagnetic shielding material according to one embodiment of the present invention.

FIG. 4 is a conceptual diagram of a second step of the manufacturing method.

FIG. 5 is a conceptual diagram of a third step of the manufacturing method.

FIG. 6 is a conceptual diagram of a fourth step of the manufacturing method.

FIG. 7 is a conceptual diagram of a fifth step of the manufacturing method.

FIG. 8 is a conceptual diagram of a sixth step of the manufacturing method.

FIG. 9 is a conceptual diagram of a seventh step of the manufacturing method.

FIG. 10 is a conceptual diagram of an eighth step of the manufacturing method.

11A and 11B are conceptual diagrams showing a layer configuration of a printed circuit board manufactured by the same manufacturing method, wherein FIG. 11A is an example in which a circuit pattern is formed on a base film via an adhesive layer, and FIG. 2 shows an example in which a circuit pattern is directly formed.

FIG. 12 is a conceptual diagram showing another layer configuration of a printed circuit board manufactured by the same manufacturing method, in which (A) is an example in which a circuit pattern is formed on a base film via an adhesive layer,
(B) shows an example in which a circuit pattern is formed directly on a base film.

FIG. 13 is a conceptual diagram showing another layer configuration of the printed circuit board manufactured by the same manufacturing method, and shows an example in which a circuit pattern is directly formed on a base film.

FIG. 14 is a conceptual diagram of a first step in the manufacturing method of the present invention.

FIG. 15 is a conceptual diagram of a second step in the manufacturing method.

FIG. 16 is a conceptual diagram showing a layer structure of a printed circuit board manufactured by the same manufacturing method, where (A) is an example in which a circuit pattern and the like are formed on a cover film via an adhesive layer, and (B).
Shows an example in which a circuit pattern or the like is directly formed on a cover film.

FIG. 17 is a conceptual diagram of a first step in another manufacturing method of the present invention.

18A and 18B are conceptual diagrams illustrating a layer configuration of a printed circuit board manufactured by the manufacturing method of FIG. 17; FIG. 18A illustrates an example in which a circuit pattern and the like are formed on a cover film via an adhesive layer;
(B) shows an example in which a circuit pattern or the like is directly formed on a cover film.

FIG. 19 is a schematic diagram illustrating a relationship between a bending direction of a printed circuit board and a direction of a line portion.

[Explanation of symbols]

1, 10: base film, 2a: adhesive layer, 2b: adhesive layer, 3: metal foil, 3a: metal foil mesh, 12a:
Circuit pattern, A, A '... electromagnetic wave shielding material, B, C
... printed circuit boards.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5E321 AA17 BB21 BB25 BB41 BB44 GG05 GG09 5E346 AA06 AA11 AA12 AA15 AA16 AA32 AA35 BB01 BB02 BB04 BB06 CC10 CC31 CC41 DD02 DD12 DD32 DD44 DD48 EE02 GG18H13

Claims (4)

[Claims] 1. A printed circuit board with an electromagnetic wave shielding material, wherein an electromagnetic wave shielding material made of a metal foil mesh is provided on both sides of a substrate on which a circuit pattern is provided. 2. The substrate and the electromagnetic wave shielding material,
The electromagnetic wave shielding material is formed in a lattice shape including vertical and horizontal line portions, and is formed of a flexible material so that it can be used by bending in a predetermined direction. 2. The printed circuit board with an electromagnetic wave shielding material according to claim 1, wherein the widths of the line portions are different from each other. 3. The printed circuit board with an electromagnetic shielding material according to claim 1, wherein an insulating plate is further laminated so as to sandwich the substrate. 4. A metal foil is provided on both surfaces of a substrate, (1) a metal foil on one surface is etched by a photoresist method to form a circuit pattern, and (2) a metal foil on the other surface is photoresist. Providing an electromagnetic wave shielding material having a mesh pattern by performing etching by the method,
(3) In the method of manufacturing a printed circuit board with an electromagnetic wave shielding material provided with an electromagnetic wave shielding material having a mesh pattern formed by etching by a photoresist method on the surface of the circuit pattern, the etching of (1) and the above (2) ) Or (3), wherein the etching is performed simultaneously.