JP7244535B2 - EMI SHIELDING FILM, METHOD FOR MANUFACTURING SHIELD PRINTED WIRING BOARD, AND SHIELD PRINTED WIRING BOARD - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electromagnetic wave shielding film, a method for manufacturing a shield printed wiring board, and a shield printed wiring board.

Flexible printed wiring boards are widely used to incorporate circuits into complicated mechanisms in electronic devices such as mobile phones, video cameras, and notebook computers, which are rapidly becoming smaller and more functional. Furthermore, taking advantage of its excellent flexibility, it is also used to connect a movable part such as a printer head and a control part. These electronic devices require measures to shield against electromagnetic waves, and the flexible printed wiring boards used in the equipment must be equipped with electromagnetic shielding measures such as attaching an electromagnetic shielding film (hereafter referred to as "flexible printed wiring boards"). (Also described as a "shield printed wiring board") has come to be used.

Generally, an electromagnetic wave shielding film consists of an outermost insulating layer (protective layer), a shield layer for shielding electromagnetic waves, and an adhesive layer for attaching to a printed wiring board.
When manufacturing the shield printed wiring board, the electromagnetic shielding film is attached to the flexible printed wiring board so that the adhesive layer of the electromagnetic shielding film is in contact with the flexible printed wiring board.

In addition, the ground circuit of the flexible printed wiring board is electrically connected to the external ground such as the housing. and an external ground are also electrically connected.

For example, in Patent Document 1, the adhesive layer of the electromagnetic wave shielding film is made of a conductive adhesive, the conductive adhesive is brought into contact with the ground circuit of the flexible printed wiring board, and the adhesive layer is connected to the external ground. Thus, the ground circuit of the flexible printed wiring board and the external ground are electrically connected.

JP 2004-095566 A

The conductive adhesive layer of the electromagnetic wave shielding film described in Patent Document 1 is composed of an adhesive resin and a conductive filler, and the conductivity of the conductive adhesive layer is obtained by the conductive filler.
That is, electrical contact between the conductive adhesive layer and the ground circuit is obtained by contact between the conductive filler and the ground circuit. The contact surface between the conductive adhesive and the ground circuit has a portion where the conductive filler does not exist. Since there is such a portion, there is a problem that the connection resistance between the ground circuit and the shield layer increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electromagnetic wave shield film for manufacturing a shield printed wiring board with sufficiently low connection resistance between the ground circuit and the shield layer. .

The electromagnetic wave shielding film of the present invention comprises a protective layer, a shield layer laminated on the protective layer, and an adhesive layer laminated on the shield layer. A bump is formed, and the volume of the conductive bump is 30,000 to 400,000 μm ³ .

The electromagnetic wave shielding film of the present invention comprises a base film, a printed circuit including a ground circuit formed on the base film, and a coverlay covering the printed circuit, the coverlay having an opening exposing the ground circuit. It is attached to the printed wiring board that has been formed.

At this time, the conductive bump penetrates the adhesive layer and comes into contact with the ground circuit.
Here, in the electromagnetic wave shielding film of the present invention, the volume of the conductive bumps is 30,000 to 400,000 μm ³ .
When the volume of the conductive bump is within the above range, the conductive bump is firmly in contact with the ground circuit, and the connection resistance between the ground circuit and the shield layer is reduced.
If the volume of the conductive bump is less than 30000 μm ³ , the conductive bump is less likely to come into contact with the ground circuit, and the connection resistance between the ground circuit and the shield layer tends to increase.
When the volume of the conductive bump exceeds 400000 μm ³ , the conductive bump occupies a large proportion of the adhesive layer.
Therefore, the relative permittivity and dielectric loss tangent of the entire region where the adhesive layer is present tend to increase. Therefore, transmission characteristics deteriorate.

In the electromagnetic wave shielding film of the present invention, the shape of the conductive bumps is desirably pyramidal.
If the conductive bump has a conical shape, the conductive bump can easily penetrate the adhesive layer and easily come into contact with the ground circuit.
Therefore, the connection resistance between the ground circuit and the shield layer is sufficiently reduced.

In the electromagnetic wave shielding film of the present invention, it is desirable that a plurality of conductive bumps are formed.
Furthermore, it is desirable that the heights of the plurality of conductive bumps are substantially the same.
When the heights of the plurality of conductive bumps are substantially the same, the plurality of conductive bumps evenly pierce the adhesive layer and easily come into contact with the ground circuit.
Therefore, the connection resistance between the ground circuit and the shield layer can be reduced.

In the electromagnetic wave shielding film of the present invention, the conductive bumps may be made of a resin composition and a conductive filler.
That is, the conductive bumps may be made of conductive paste.
By using the conductive paste, the conductive bumps can be easily formed at any position and with any shape.

In the electromagnetic wave shielding film of the present invention, it is desirable that the resin constituting the adhesive layer has a dielectric constant of 1 to 5 and a dielectric loss tangent of 0.0001 to 0.03 at a frequency of 1 GHz and 23°C.
Within such a range, the transmission characteristics of the shield printed wiring board manufactured using the electromagnetic wave shielding film of the present invention can be improved.

In the electromagnetic wave shielding film of the present invention, the adhesive layer is desirably an insulating adhesive layer.
Also, the electromagnetic wave shielding film of the present invention is adhered to the printed wiring board by the adhesive layer.
When the adhesive layer is an insulating adhesive layer, the insulating adhesive layer does not contain a conductive substance such as a conductive filler, so that the dielectric constant and the dielectric loss tangent are sufficiently small.
Therefore, a shield printed wiring board manufactured using the electromagnetic wave shielding film of the present invention has good transmission characteristics.

A method for manufacturing a shield printed wiring board of the present invention includes an electromagnetic shielding film preparing step of preparing the electromagnetic shielding film of the present invention, a base film, a printed circuit including a ground circuit formed on the base film, a printed wiring board preparing step of preparing a printed wiring board comprising a coverlay covering the printed circuit, the coverlay having an opening for exposing the ground circuit; and an adhesive layer of the electromagnetic wave shielding film. However, an electromagnetic shielding film arranging step of arranging the electromagnetic shielding film on the printed wiring board so as to be in contact with the coverlay of the printed wiring board, and a conductive bump of the electromagnetic shielding film is an adhesive of the electromagnetic shielding film and a pressurizing step of penetrating the layer and applying pressure so as to come into contact with the ground circuit of the printed wiring board.

The method for producing a shield printed wiring board of the present invention is a method for producing a shield printed wiring board using the electromagnetic wave shielding film of the present invention.
Therefore, the obtained shield printed wiring board has a low connection resistance between the ground circuit and the shield layer.

A shield printed wiring board of the present invention comprises a base film, a printed circuit including a ground circuit formed on the base film, and a coverlay covering the printed circuit, wherein the coverlay includes the ground circuit. It comprises a printed wiring board having an exposed opening and the electromagnetic wave shielding film of the present invention, and the conductive bumps of the electromagnetic wave shielding film penetrate the adhesive layer and connect to the ground circuit of the printed wiring board. characterized by being connected.

In the shield printed wiring board of the present invention, the conductive bumps of the electromagnetic wave shielding film of the present invention pierce the adhesive layer and are connected to the ground circuit of the printed wiring board.
Therefore, the conductive bumps of the electromagnetic wave shielding film are firmly in contact with the ground circuit of the printed wiring board, and the connection resistance between the ground circuit and the shield layer is reduced.

The electromagnetic wave shielding film of the present invention comprises a base film, a printed circuit including a ground circuit formed on the base film, and a coverlay covering the printed circuit, the coverlay having an opening exposing the ground circuit. It is attached to the printed wiring board that has been formed.

At this time, the conductive bump penetrates the adhesive layer and comes into contact with the ground circuit.
Here, in the electromagnetic wave shielding film of the present invention, the volume of the conductive bumps is 30,000 to 400,000 μm ³ .
When the volume of the conductive bump is within the above range, the conductive bump is firmly in contact with the ground circuit, and the connection resistance between the ground circuit and the shield layer is reduced.

FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a shield printed wiring board using the electromagnetic wave shielding film of the present invention. FIG. 3A is a process diagram showing an example of the manufacturing method of the shield printed wiring board of the present invention in order of steps. FIG. 3B is a process drawing showing an example of the manufacturing method of the shield printed wiring board of the present invention in order of steps. FIG. 3C is a process drawing showing an example of the manufacturing method of the shield printed wiring board of the present invention in order of steps. FIG. 3D is a process diagram showing an example of the manufacturing method of the shield printed wiring board of the present invention in order of steps. 4 is a cross-sectional photograph of the electromagnetic wave shielding film according to Example 1. FIG. FIG. 5 is a schematic diagram schematically showing a method of measuring the transmission loss of the electromagnetic wave shielding film in the transmission loss measurement test. FIG. 6 is a schematic diagram schematically showing a method of measuring the resistance value of the electromagnetic wave shielding film in the connection resistance measurement test.

The electromagnetic wave shielding film of the present invention will be specifically described below. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

The electromagnetic wave shielding film of the present invention comprises a protective layer, a shield layer laminated on the protective layer, and an adhesive layer laminated on the shield layer. A bump is formed.

Each configuration of the electromagnetic wave shielding film of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention.
FIG. 2 is a cross-sectional view schematically showing an example of a shield printed wiring board using the electromagnetic wave shielding film of the present invention.

As shown in FIG. 1 , the electromagnetic wave shielding film 10 comprises a protective layer 11 , a shield layer 12 laminated on the protective layer 11 , and an adhesive layer 13 laminated on the shield layer 12 .
A plurality of conductive bumps 14 are formed on the adhesive layer 13 side of the shield layer 12 .

As shown in FIG. 2, the electromagnetic wave shielding film 10 includes a base film 21, a printed circuit 22 including a plurality of ground circuits 22a formed on the base film 21, and a coverlay 23 covering the printed circuit 22. , and the coverlay 23 is attached to the printed wiring board 20 in which the opening 23 a is formed to expose the ground circuit 22 a and is used to manufacture the shield printed wiring board 30 .

(protective layer)
Although the material of the protective layer 11 is not particularly limited, it is preferably composed of a thermoplastic resin composition, a thermosetting resin composition, an active energy ray-curable composition, or the like.

Examples of the thermoplastic resin composition include, but are not limited to, styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, and imide resin compositions. , acrylic resin compositions, and the like.

Examples of the thermosetting resin composition include, but are not limited to, epoxy-based resin compositions, urethane-based resin compositions, urethane-urea-based resin compositions, styrene-based resin compositions, phenol-based resin compositions, and melamine-based resin compositions. at least one resin composition selected from the group consisting of products, acrylic resin compositions and alkyd resin compositions.

Examples of the active energy ray-curable composition include, but are not limited to, polymerizable compounds having at least two (meth)acryloyloxy groups in the molecule.

The protective layer 11 may be composed of a single material, or may be composed of two or more materials.

The protective layer 11 may optionally contain a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity adjuster. agents, anti-blocking agents and the like may also be included.

The thickness of the protective layer 11 is not particularly limited and can be appropriately set as required, but is preferably 1 to 15 μm, more preferably 3 to 10 μm.
If the thickness of the protective layer is less than 1 μm, it is too thin to sufficiently protect the shield layer and the adhesive layer.
If the thickness of the protective layer exceeds 15 μm, the protective layer is too thick to be bent, and the protective layer itself is likely to be damaged. Therefore, it becomes difficult to apply to members requiring bending resistance.

(shield layer)
The material of the shield layer 12 is not particularly limited as long as it is a conductive material as long as it can shield electromagnetic waves. For example, it may be made of a metal or a conductive resin.

When the shield layer 12 is made of metal, the metal includes gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, and the like. Among these, copper is desirable. Copper is a preferred material for the shield layer from the standpoint of conductivity and economy.

The shield layer 12 may be made of an alloy of the above metals.
Also, the shield layer 12 may be a metal foil, or may be a metal film formed by a method such as sputtering, electroless plating, or electrolytic plating.

When the shield layer 12 is made of a conductive resin, the shield layer 12 may be made of conductive particles and resin.

The conductive particles are not particularly limited, but may be fine metal particles, carbon nanotubes, carbon fibers, metal fibers, or the like.

When the conductive particles are metal microparticles, the metal microparticles are not particularly limited, but include silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by plating copper powder with silver, and polymer microparticles. Fine particles obtained by coating glass beads or the like with a metal may also be used.
Among these, copper powder or silver-coated copper powder, which are available at low cost, are desirable from the viewpoint of economy.

The average particle diameter _D50 of the conductive particles is not particularly limited, but is preferably 0.5 to 15.0 μm. When the average particle size of the conductive particles is 0.5 μm or more, the conductive resin has good conductivity. When the average particle size of the conductive particles is 15.0 µm or less, the conductive resin can be thinned.

The shape of the conductive particles is not particularly limited, but can be appropriately selected from spherical, flat, scale-like, dendrite-like, rod-like, fibrous and the like.

The amount of the conductive particles to be blended is not particularly limited, but is preferably 15 to 80% by mass, more preferably 15 to 60% by mass.

Examples of resins include, but are not limited to, styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, and amide resin compositions. thermosetting materials such as thermoplastic resin compositions such as acrylic resin compositions, phenolic resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, alkyd resin compositions, etc. A resin composition etc. are mentioned.

(Conductive bump)
The conductive bump 14 penetrates the adhesive layer 13 and contacts the ground circuit 22a.
The connection resistance between the ground circuit 22a and the conductive bumps 14 can be reduced by designing the conductive bumps 14 to reliably contact the ground circuit 22a.

The shape of the conductive bumps 14 is not particularly limited, but may be a columnar shape such as a cylinder, a triangular column, or a square column, or a pyramidal shape such as a cone, a triangular pyramid, or a quadrangular pyramid.
Among these, a conical shape is desirable.
When the conductive bump 14 has a conical shape, the conductive bump 14 easily penetrates the adhesive layer 13 and easily comes into contact with the ground circuit 22a.
Therefore, the connection resistance between the ground circuit 22a and the conductive bump 14 is sufficiently reduced.

The volume of each conductive bump 14 is desirably 30,000 to 400,000 μm ³ , more desirably 50,000 to 400,000 μm ³ .
When the volume of each conductive bump 14 is within the above range, the conductive bump 14 is in firm contact with the ground circuit 22a, and the connection resistance between the ground circuit 22a and the conductive bump 14 is reduced.
If the volume of each conductive bump is less than 30000 μm ³ , the conductive bumps are less likely to come into contact with the ground circuit, and the connection resistance between the ground circuit and the shield layer tends to increase.
If the volume of each conductive bump exceeds 400000 μm ³ , the ratio of the conductive bumps in the adhesive layer increases.
Therefore, the relative permittivity and dielectric loss tangent of the entire region where the adhesive layer is present tend to increase. Therefore, transmission characteristics tend to deteriorate.

It is desirable that the heights of the plurality of conductive bumps 14 (the height indicated by symbol "H" in FIG. 1) are approximately the same.
When the heights of the plurality of conductive bumps 14 are substantially the same, the plurality of conductive bumps 14 evenly pierce the adhesive layer 13 and easily come into contact with the ground circuit 22a.
Therefore, the connection resistance between the ground circuit 22a and the conductive bump 14 can be reduced.

The height of the conductive bumps 14 is preferably 1-50 μm, more preferably 5-30 μm.

The shape, height, and volume of the conductive bumps were measured at any five points on the surface of the shield layer on which the bumps were formed using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20x). After that, it can be analyzed using data analysis software (LMeye7). The binarization parameter was height, and the Kittler method was used as the automatic threshold algorithm.

Although the arrangement position of the conductive bumps 14 is not particularly limited, they may be arranged only at the positions in contact with the ground circuit 22a, or may be arranged at regular intervals.

The conductive bumps 14 are desirably made of a resin composition and a conductive filler.
That is, the conductive bumps 14 may be made of conductive paste.
By using the conductive paste, the conductive bumps 14 can be easily formed in arbitrary positions and in arbitrary shapes.
Alternatively, the conductive bumps 14 may be formed by screen printing.
When the conductive bumps 14 are formed by screen printing using a conductive paste, the conductive bumps 14 can be easily and efficiently formed at any position and in any shape.

When the conductive bumps 14 are made of a resin composition and a conductive filler, the resin composition is not particularly limited, but may be a styrene-based resin composition, a vinyl acetate-based resin composition, a polyester-based resin composition, or a polyethylene-based resin. Compositions, polypropylene resin compositions, imide resin compositions, amide resin compositions, thermoplastic resin compositions such as acrylic resin compositions, phenol resin compositions, epoxy resin compositions, urethane resins A composition, a thermosetting resin composition such as a melamine resin composition, an alkyd resin composition, and the like can be used.
The material of the resin composition may be one of these alone or a combination of two or more.

When the conductive bumps 14 are made of a resin composition and a conductive filler, the conductive filler is not particularly limited, but may be metal microparticles, carbon nanotubes, carbon fibers, metal fibers, or the like.

When the conductive filler is a fine metal particle, the fine metal particle is not particularly limited, but may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by plating copper powder with silver, or polymer fine particles. Fine particles obtained by coating glass beads or the like with a metal may also be used.
Among these, copper powder or silver-coated copper powder, which are available at low cost, are desirable from the viewpoint of economy.

Although the average particle diameter _D50 of the conductive filler is not particularly limited, it is preferably 0.5 to 15.0 μm.

The shape of the conductive filler is not particularly limited, but can be appropriately selected from spherical, flat, scaly, dendritic, rod-like, fibrous and the like.

When the conductive bumps 14 are composed of the resin composition and the conductive filler, the weight ratio of the conductive filler is desirably 30 to 99%, more desirably 50 to 99%.

Also, the conductive bumps may be made of metal formed by a plating method, a vapor deposition method, or the like.
In this case, the conductive bumps are preferably made of copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or alloys containing any one or more of these.
A conventional method can be used for the plating method and vapor deposition method.

(adhesive layer)
As described above, the electromagnetic wave shielding film 10 is adhered to the printed wiring board 20 with the adhesive layer 13 .

In the electromagnetic wave shielding film 10, the surface of the adhesive layer 13 opposite to the shield layer 12 is desirably flat.
If this surface is flat, the plurality of conductive bumps 14 will penetrate the adhesive layer 13 evenly.
Therefore, the plurality of conductive bumps 14 are evenly in contact with the plurality of ground circuits 22a. Therefore, the connection resistance between the ground circuit and the shield layer can be reduced.

In the electromagnetic wave shielding film 10, the thickness of the adhesive layer 13 is desirably 5-30 μm, more desirably 8-20 μm.
If the thickness of the adhesive layer is less than 5 μm, the amount of resin constituting the adhesive layer is too small to obtain sufficient adhesive performance. Moreover, it becomes easy to damage.
If the thickness of the adhesive layer exceeds 30 μm, the entire thickness is increased and the flexibility is likely to be lost. Also, the conductive bumps are less likely to penetrate the adhesive layer.

In the electromagnetic wave shielding film 10, the dielectric constant of the resin forming the adhesive layer 13 is desirably 1 to 5, more desirably 2 to 4, at a frequency of 1 GHz and 23.degree.
Further, the dielectric loss tangent of the resin constituting the adhesive layer 13 at a frequency of 1 GHz and 23° C. is preferably 0.0001 to 0.03, more preferably 0.001 to 0.002.
Within such a range, the transmission characteristics of the shield printed wiring board 30 manufactured using the electromagnetic wave shielding film 10 can be improved.

In the electromagnetic wave shielding film 10, the adhesive layer 13 may be a conductive insulating layer or an insulating adhesive layer. From the viewpoint of lowering , the insulating adhesive layer is desirable.
As described above, the electromagnetic wave shielding film 10 is adhered to the printed wiring board 30 with the adhesive layer 13 .
When the adhesive layer 13 is an insulating adhesive layer, since the adhesive layer 13 does not contain a conductive substance such as a conductive filler, the dielectric constant and dielectric loss tangent are sufficiently small. In this case, the shield printed wiring board 30 manufactured using the electromagnetic wave shielding film 10 has good transmission characteristics.

In addition, when the adhesive layer 13 has conductivity, the adhesive layer 13 contains a conductive substance such as a conductive filler. If the adhesive layer 13 contains a large amount of such a conductive substance, the dielectric constant and dielectric loss tangent of the entire adhesive layer 13 tend to increase.
On the other hand, in order to improve the transmission characteristics of the manufactured shield printed wiring board 30, it is desirable that the dielectric constant and dielectric loss tangent of the entire adhesive layer 13 are low.
Therefore, even if the adhesive layer 13 contains a conductive substance, it is desirable that the content be small so that the dielectric constant and dielectric loss tangent of the entire adhesive layer 13 are low.

The adhesive layer 13 may be made of a thermosetting resin or may be made of a thermoplastic resin.

Examples of thermosetting resins include phenol-based resins, epoxy-based resins, urethane-based resins, melamine-based resins, polyamide-based resins, and alkyd-based resins.
Examples of thermoplastic resins include styrene-based resins, vinyl acetate-based resins, polyester-based resins, polyethylene-based resins, polypropylene-based resins, imide-based resins, and acrylic-based resins.
Further, the epoxy resin is more preferably an amide-modified epoxy resin.
These resins are suitable as resins constituting the adhesive layer.
The material for the adhesive layer may be one of these alone, or a combination of two or more.

(Printed wiring board)
The printed wiring board 20 to which the electromagnetic wave shielding film 10 is attached will be described below.

(Base film and coverlay)
Materials for the base film 21 and the coverlay 23 are not particularly limited, but are preferably made of engineering plastics. Examples of such engineering plastics include resins such as polyethylene terephthalate, polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, and polyphenylene sulfide.
Among these engineering plastics, polyphenylene sulfide film is desirable when flame retardancy is required, and polyimide film is desirable when heat resistance is required. The thickness of the base film 21 is preferably 10-40 μm, and the thickness of the coverlay 23 is preferably 10-30 μm.

Although the size of the opening 23a is not particularly limited, it is preferably 0.1 mm ² or more, more preferably 0.3 mm ² or more.
The shape of the opening 23a is not particularly limited, and may be circular, elliptical, quadrangular, triangular, or the like.

(printed circuit)
Materials for the printed circuit 22 and the ground circuit 22a are not particularly limited, and may be copper foil, cured conductive paste, or the like.

Shield printed wiring board 30 manufactured by attaching electromagnetic shielding film 10 to printed wiring board 20 is one aspect of the shield printed wiring board of the present invention.

The shield printed wiring board 30 shown in FIG. 2 includes a base film 21, a printed circuit 22 including a plurality of ground circuits 22a formed on the base film 21, and a coverlay 23 covering the printed circuit 22, A printed wiring board 20 formed with an opening exposing a ground circuit 22 in a coverlay 23, a protective layer 11, a shield layer 12 laminated on the protective layer 11, and an adhesive laminated on the shield layer 12. The shield layer 12 on the side of the adhesive layer 13 is made of an electromagnetic wave shielding film 10 in which a plurality of conductive bumps 14 are formed. It penetrates the layer 13 and connects to a plurality of ground circuits 22 a of the printed wiring board 20 .

In the shield printed wiring board 30 , the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate through the adhesive layer 13 and are connected to the plurality of ground circuits 22 a of the printed wiring board 20 .
The connection resistance between the ground circuit 22a and the conductive bumps 14 can be reduced by designing the conductive bumps 14 to reliably contact the ground circuit 22a.

Next, an example of the method for manufacturing the shield printed wiring board of the present invention will be described with reference to the drawings.
3A, 3B, 3C and 3D are process diagrams showing an example of the method for manufacturing the shield printed wiring board of the present invention in order of steps.

(Electromagnetic wave shielding film preparation process)
In this step, as shown in FIG. 3A, the electromagnetic wave shielding film 10 is prepared.
Since the desirable configuration of the electromagnetic wave shielding film 10 has already been described, the description thereof will be omitted here.

(Printed wiring board preparation process)
In this step, as shown in FIG. 3B, a printed wiring board 20 is prepared.
Since the desirable configuration of the printed wiring board 20 has already been described, the description is omitted here.

(Electromagnetic wave shielding film placement process)
In this step, the electromagnetic wave shielding film 10 is placed on the printed wiring board 20 so that the adhesive layer surface of the electromagnetic wave shielding film 10 is in contact with the coverlay 23 of the printed wiring board 20, as shown in FIG. 3C.
At this time, the conductive bump 14 is positioned on the ground circuit 22a.

(pressurization process)
In this step, as shown in FIG. 3D, the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate through the adhesive layer 13 of the electromagnetic wave shielding film 10 and come into contact with the plurality of ground circuits 22a of the printed wiring board 20. pressurize to

Conditions for pressurization include, for example, conditions of 1 to 5 Pa and 1 to 60 minutes.

In the manufacturing method of the shield printed wiring board of the present invention, the adhesive layer 13 of the electromagnetic wave shielding film 10 may be cured by heating after or at the same time as the pressing step.

The shield printed wiring board 30 can be manufactured through the above steps.

EXAMPLES The present invention will be described below in more detail with examples, but the present invention is not limited to these examples.

(Example 1)
First, as the first release film, a polyethylene terephthalate film having one side subjected to release treatment was prepared.

Next, an epoxy resin was applied to the release-treated surface of the first release film and heated at 100° C. for 2 minutes using an electric oven to prepare a protective layer having a thickness of 7 μm.
After that, a copper layer of 2 μm was formed on the protective layer by electroless plating. The copper layer becomes a shield layer.

Next, 10 parts by weight of a mixture of cresol novolac type epoxy resin and isocyanate and 90 parts by weight of a conductive filler (spherical silver-coated copper powder having an average particle diameter of 5 μm) were mixed to prepare a conductive paste.
The weight ratio of the mixture of cresol novolak type epoxy resin and isocyanate was cresol novolac type epoxy resin:isocyanate=100:0.2.
Conductive bumps were then formed by screen-printing a conductive paste onto the copper layer.
The conductive bumps were conical in shape, 23 μm high and 120000 μm ³ in volume.
The shape, height, and volume of the conductive bumps were measured at any five points on the surface of the shield layer on which the bumps were formed using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20x). After that, it can be analyzed using data analysis software (LMeye7). The binarization parameter was height, and the Kittler method was used as the automatic threshold algorithm.

Next, 100.0 parts of an epoxy resin and 49.6 parts of an organic phosphorus flame retardant were mixed to prepare a composition for an adhesive layer.

Next, as the second release film, a polyethylene terephthalate film having one side subjected to release treatment was prepared.
Then, the adhesive layer composition was applied to the release-treated surface of the second release film and heated at 100° C. for 2 minutes using an electric oven to prepare an adhesive layer having a thickness of 9 μm.

Next, the protective layer formed on the first release film and the adhesive layer formed on the second release film are bonded together, and the second release film is peeled off to manufacture the electromagnetic wave shielding film according to Example 1. bottom.

4 is a cross-sectional photograph of the electromagnetic wave shielding film according to Example 1. FIG.
As shown in FIG. 4, the electromagnetic wave shielding film 10 according to Example 1 includes a protective layer 11, a shield layer 12 laminated on the protective layer 11, and an adhesive layer 13 laminated on the shield layer 12. A conical conductive bump 14 is formed on the shield layer 12 on the adhesive layer 13 side.

(Example 2) and (Comparative Example 1)
Electromagnetic wave shielding films according to Example 2 and Comparative Example 1 were produced in the same manner as in Example 1, except that the height and volume of the conductive bumps were changed as shown in Table 1.

(Comparative example 2)
First, as the first release film, a polyethylene terephthalate film having one side subjected to release treatment was prepared.

Next, an epoxy resin was applied to the release-treated surface of the first release film and heated at 100° C. for 2 minutes using an electric oven to prepare a protective layer having a thickness of 7 μm.
After that, a copper layer of 2 μm was formed on the protective layer by electroless plating. The copper layer becomes a shield layer.

Next, 100.0 parts of an amide-modified epoxy resin, 49.6 parts of silver-coated copper powder (average particle size D ₅₀ : 13 µm), and 49.6 parts of an organic phosphorus flame retardant were mixed to form a conductive adhesive layer. A composition for

Next, as the second release film, a polyethylene terephthalate film having one side subjected to release treatment was prepared.
Then, the conductive adhesive layer composition was applied to the release-treated surface of the second release film and heated at 100° C. for 2 minutes using an electric oven to prepare a conductive adhesive layer having a thickness of 9 μm.

Next, the protective layer formed on the first release film and the adhesive layer formed on the second release film are bonded together, and the second release film is peeled off to manufacture the electromagnetic wave shielding film according to Comparative Example 2. bottom.

(Transmission loss measurement test)
FIG. 5 is a schematic diagram schematically showing a method of measuring the transmission loss of the electromagnetic wave shielding film in the transmission loss measurement test.
The transmission loss measurement of the electromagnetic wave shielding film was evaluated using the network analyzer 41 shown in FIG.
As the network analyzer 41, ZVL6 manufactured by Rohde & Schwarz was used. The network analyzer 41 has an input terminal and an output terminal, to which a connection board 42 is connected. Measurement is performed by connecting the shield printed wiring board 30 to be measured between the pair of connection boards 42 so as to be supported in a straight line floating in the air. A shield printed wiring board 30 having a length of 100 mm was used. Measurements were also performed in the frequency range from 100 kHz to 20 GHz. Further, the measurement was performed in an atmosphere of 25° C. and 30 to 50% relative humidity. The network analyzer 41 measured how much the input signal was attenuated with respect to the output signal at a frequency of 10 GHz. Table 1 shows the measured attenuation as transmission loss. The closer the attenuation is to zero, the less the transmission loss.

(Connection resistance measurement test)
FIG. 6 is a schematic diagram schematically showing a method of measuring the resistance value of the electromagnetic wave shielding film in the connection resistance measurement test.
An electromagnetic wave shielding film 110 in FIG. 6 schematically shows the electromagnetic wave shielding films according to the first and second examples.
The electromagnetic wave shielding film 110 includes a protective layer 111, a shield layer 112 laminated on the protective layer 111, and an adhesive layer 113 laminated on the shield layer 112. The shield layer 112 on the adhesive layer 113 side has a plurality of of conductive bumps 114 are formed.
In the connection resistance measurement test, a base film 121, a plurality of measurement printed circuits 125 formed on the base film 121, and a coverlay 123 covering the measurement printed circuit 125 are provided. A model board 120 having an opening 123a exposing the printed circuit 125 for measurement is prepared.
The opening 123a is circular with a diameter of 1 mm.

In the connection resistance measurement test, as shown in FIG. 6, the electromagnetic shielding film 110 was placed on the model substrate 120 so that the conductive bumps 114 of the electromagnetic shielding film 110 were in contact with the measurement printed circuit 125, and the temperature was 170° C., 3 Pa, The electromagnetic shielding film 110 was adhered to the model substrate 120 by applying pressure and heating for 3 minutes and then post-curing at 150° C. for 1 hour.
After that, the resistance value between the measurement printed circuits 125 was measured by the ohmmeter 150 .

The electromagnetic wave shielding film according to Comparative Example 1 has the same configuration as the electromagnetic wave shielding film 110 except that the conductive bump is not provided and the adhesive layer is a conductive adhesive layer.
The electromagnetic wave shielding film according to Comparative Example 1 was also attached to the model substrate 120 under the same conditions as the above method, and the resistance value between the measurement printed circuits 125 was measured with the ohmmeter 150 .

Table 1 shows the results of the connection resistance test of the electromagnetic wave shielding films according to each example and comparative example.

As shown in Table 1, the electromagnetic wave shielding films according to Examples 1 and 2 exhibited small transmission losses in the transmission loss measurement test and small resistance values in the connection resistance measurement test.

10, 110 electromagnetic wave shielding films 11, 111 protective layers 12, 112 shield layers 13, 113 adhesive layers 14, 114 conductive bumps 20 printed wiring boards 21, 121 base films 22 printed circuits 22a ground circuits 23, 123 coverlays 23a, 123a opening 30 shield printed wiring board 41 network analyzer 42 connection board 120 model board 125 measurement printed circuit 150 resistance meter

Claims (8)

a protective layer;
a shield layer laminated on the protective layer;
and an adhesive layer laminated on the shield layer,
A conductive bump is formed on the adhesive layer side of the shield layer,
the volume of the conductive bump is 30000-400000 μm ³ ;
The conductive bumps are embedded in the adhesive layer so as not to be exposed from the surface of the adhesive layer facing the surface in contact with the shield layer ,
The conductive bump has a conical shape convex in a direction from a surface of the adhesive layer in contact with the shield layer toward a surface of the adhesive layer facing the surface of the adhesive layer in contact with the shield layer. electromagnetic wave shielding film. 2. The electromagnetic wave shielding film according to claim 1 , wherein a plurality of said conductive bumps are formed. 3. The electromagnetic wave shielding film according to claim 2 , wherein the heights of the plurality of conductive bumps are substantially the same. The electromagnetic wave shielding film according to any one of claims 1 to 3 , wherein the conductive bumps are made of a resin composition and a conductive filler. The electromagnetic wave according to any one of claims 1 to 4 , wherein the resin constituting the adhesive layer has a dielectric constant of 1 to 5 and a dielectric loss tangent of 0.0001 to 0.03 at a frequency of 1 GHz and 23°C. shield film. The electromagnetic wave shielding film according to any one of claims 1 to 5 , wherein the adhesive layer is an insulating adhesive layer. An electromagnetic shielding film preparing step for preparing the electromagnetic shielding film according to any one of claims 1 to 6 ;
A base film, a printed circuit including a ground circuit formed on the base film, and a coverlay covering the printed circuit, the coverlay having an opening exposing the ground circuit. A printed wiring board preparation step of preparing a printed wiring board;
an electromagnetic shielding film placing step of placing the electromagnetic shielding film on the printed wiring board so that the adhesive layer of the electromagnetic shielding film is in contact with the coverlay of the printed wiring board;
a pressing step of applying pressure so that the conductive bumps of the electromagnetic wave shielding film penetrate through the adhesive layer of the electromagnetic wave shielding film and come into contact with the ground circuit of the printed wiring board. manufacturing method. A base film, a printed circuit including a ground circuit formed on the base film, and a coverlay covering the printed circuit, the coverlay having an opening exposing the ground circuit. a printed wiring board;
Consisting of the electromagnetic wave shielding film according to any one of claims 1 to 6 ,
A shield printed wiring board, wherein the conductive bumps of the electromagnetic shielding film penetrate the adhesive layer and are connected to a ground circuit of the printed wiring board.

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