TWI782213B - Electromagnetic wave shielding film, manufacturing method of shielding printed wiring board, and shielding printed wiring board - Google Patents

Abstract

The object of the present invention is to provide an electromagnetic wave shielding film for manufacturing a shielded printed wiring board in which the connection resistance between the ground circuit and the shielding layer is very small. An electromagnetic wave shielding film, characterized in that: it is composed of a protective layer, a shielding layer laminated on the protective layer, and an adhesive layer laminated on the shielding layer; a conductive bump is formed on the adhesive layer side of the shielding layer , the volume of the above-mentioned conductive bump is 30,000~400,000 μm ³ .

Description

Electromagnetic wave shielding film, manufacturing method of shielded printed wiring board, and shielded printed wiring board

The present invention relates to an electromagnetic wave shielding film, a manufacturing method of a shielded printed wiring board, and a shielded printed wiring board.

Background technique Flexible printed wiring boards are often used to build circuits in complex mechanisms in electronic devices such as mobile phones, cameras, and notebook computers that are rapidly progressing in miniaturization and high functionality. Furthermore, by taking advantage of its excellent flexibility, it is also used in the connection of movable parts such as print heads and control parts of printers. Electromagnetic wave shielding countermeasures are required in these electronic devices, and even the flexible printed wiring board used in the device is a flexible printed wiring board (hereinafter also described as "shielded printed wiring board").

Generally speaking, the electromagnetic wave shielding film is composed of the outermost insulating layer (protective layer), the shielding layer for shielding electromagnetic waves, and the adhesive layer for sticking to the printed wiring board. When manufacturing the shielded printed wiring board, the electromagnetic wave shielding film is pasted on the flexible printed wiring board in such a way that the adhesive layer of the electromagnetic wave shielding film contacts the flexible printed wiring board.

In addition, the grounding circuit of the flexible printed wiring board is electrically connected to the external grounding of the casing, etc., but it is also possible to connect the grounding circuit of the printed wiring board to the external grounding through the electromagnetic wave shielding film pasted on the flexible printed wiring board electrical connection.

For example, in Patent Document 1, the adhesive layer of the electromagnetic 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, In this way, the ground circuit of the flexible printed wiring board is electrically connected to the external ground.

Prior art literature patent documents Patent Document 1: Japanese Patent Laid-Open No. 2004-095566

Summary of the invention The problem to be solved by the invention 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 comes from the conductive filler. That is, the electrical contact between the conductive adhesive layer and the ground circuit is obtained through the contact between the conductive filler and the ground circuit. There is also a portion where no conductive filler exists on the contact surface between the conductive adhesive and the ground circuit. Due to such a portion, there is a problem that the connection resistance between the ground circuit and the shielding layer becomes high.

The present invention was made in view of the above problems, and an object of the present invention is to provide an electromagnetic wave shielding film for manufacturing a shielded printed wiring board with a very small connection resistance between a ground circuit and a shielding layer.

Means for Solving the Problems The electromagnetic wave shielding film of the present invention is characterized in that it is composed of a protective layer, a shielding layer laminated on the protective layer, and an adhesive layer laminated on the shielding layer; the adhesive layer on the shielding layer Conductive bumps are formed on the layer side, and the volume of the conductive bumps is 30,000 to 400,000 μm ³ .

The electromagnetic wave shielding film of the present invention is bonded to a printed wiring board. The printed wiring board has a base film, a printed circuit including a ground circuit formed on the base film, and a cover film covering the printed circuit. The opening where the circuit is exposed.

At this time, the conductive bump penetrates the adhesive layer and contacts 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 . If the volume of the conductive bump is within the above range, the conductive bump will firmly contact the ground circuit, and the connection resistance between the ground circuit and the shielding layer will be reduced. If the volume of the conductive bump is less than 30000 μm ³ , it is difficult for the conductive bump to contact the grounding circuit, and the connection resistance between the grounding circuit and the shielding layer tends to increase. When the volume of the conductive bump exceeds 400,000 μm ³ , the ratio of the conductive bump to the adhesive layer increases. Since the relative permittivity and dielectric loss tangent of the entire region having the adhesive layer tend to become high, transmission characteristics deteriorate.

In the electromagnetic wave shielding film of the present invention, the shape of the above-mentioned conductive bump is preferably a cone shape. If the shape of the conductive bump is tapered, the conductive bump can easily penetrate through the adhesive layer and be in contact with the ground circuit. Therefore, the connection resistance between the ground circuit and the shield layer can be sufficiently reduced.

In the electromagnetic wave shielding film of the present invention, a plurality of the above-mentioned conductive bumps are preferably formed. Furthermore, the heights of the plurality of conductive bumps are preferably approximately the same. If the heights of the plurality of conductive bumps are substantially the same, the plurality of conductive bumps can easily penetrate the adhesive layer evenly and be in contact with the ground circuit. Therefore, the connection resistance between the ground circuit and the shielding layer can be reduced.

In the electromagnetic wave shielding film of the present invention, the above-mentioned conductive bumps may also be composed of a resin composition and a conductive filler. That is, the electroconductive bump may also consist of electroconductive paste. By using the conductive paste, conductive bumps can be easily formed in arbitrary positions and in arbitrary shapes.

In the electromagnetic wave shielding film of the present invention, the relative permittivity of the resin constituting the above-mentioned adhesive layer at a frequency of 1 GHz and 23°C is preferably 1-5, and the dielectric loss tangent is preferably 0.0001-0.03. If it is the said range, the transmission characteristic of the shielded printed wiring board manufactured using the electromagnetic wave shielding film of this invention can be improved.

In the electromagnetic shielding film of the present invention, the above-mentioned adhesive layer is preferably an insulating adhesive layer. Moreover, the electromagnetic wave shielding film of this invention is adhere|attached to a printed wiring board via an adhesive agent layer. When the above-mentioned adhesive layer is an insulating adhesive layer, since the insulating adhesive layer does not contain conductive substances such as conductive fillers, the relative permittivity and dielectric loss tangent are sufficiently small. Therefore, the shielded printed wiring board manufactured using the electromagnetic wave shielding film of this invention becomes favorable in transmission characteristics.

The manufacturing method of the shielded printed wiring board of the present invention is characterized in that it comprises: an electromagnetic wave shielding film preparation step, which is to prepare the above electromagnetic wave shielding film of the present invention; a printed wiring board preparation step, which is to prepare a printed wiring board, and the printed wiring board has a substrate film, a printed circuit including a ground circuit formed on the above-mentioned base film, and a cover film covering the above-mentioned printed circuit, and an opening for exposing the above-mentioned ground circuit is formed on the above-mentioned cover film; the step of arranging the electromagnetic wave shielding film is as follows The adhesive layer of the electromagnetic wave shielding film is in contact with the cover film of the above-mentioned printed wiring board, and the above-mentioned electromagnetic wave shielding film is arranged on the above-mentioned printed wiring board; It penetrates through the adhesive layer of the electromagnetic wave shielding film and is in contact with the ground circuit of the above-mentioned printed wiring board.

The manufacturing method of the shielded printed wiring board of this invention is the manufacturing method of the shielded printed wiring board which uses the electromagnetic wave shielding film of this invention mentioned above. Therefore, the obtained shielded printed wiring board has a lower connection resistance between the ground circuit and the shielding layer.

The shielded printed wiring board of the present invention is characterized in that it is composed of a printed wiring board and the above-mentioned electromagnetic wave shielding film of the present invention, the printed wiring board includes a base film, a printed circuit including a ground circuit formed on the base film, and A cover film covering the printed circuit, and an opening for exposing the ground circuit is formed in the cover film. The conductive bump of the electromagnetic shielding film penetrates the adhesive layer and is connected to the ground circuit of the printed wiring board.

In the shielded printed wiring board of the present invention, the conductive bump of the electromagnetic wave shielding film of the present invention penetrates through the adhesive layer and is connected to the ground circuit of the printed wiring board. Therefore, the conductive bump of the electromagnetic wave shielding film will firmly contact the grounding circuit of the printed wiring board, and the connection resistance between the grounding circuit and the shielding layer will be reduced.

Invention effect The electromagnetic wave shielding film of the present invention is bonded to a printed wiring board. The printed wiring board has a base film, a printed circuit including a ground circuit formed on the base film, and a cover film covering the printed circuit. The opening where the circuit is exposed.

At this time, the conductive bump penetrates the adhesive layer and contacts 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 . If the volume of the conductive bump is within the above range, the conductive bump will firmly contact the ground circuit, and the connection resistance between the ground circuit and the shielding layer will be reduced.

form for carrying out the invention Hereinafter, the electromagnetic wave shielding film of this invention is demonstrated concretely. However, this invention is not limited to the following embodiment, In the range which does not change the gist of this invention, it can change suitably and apply.

The electromagnetic wave shielding film of the present invention is characterized in that it is composed of a protective layer, a shielding layer laminated on the protective layer, and an adhesive layer laminated on the shielding layer; the shielding layer on the side of the adhesive layer is formed with a conductive bump.

Hereinafter, each structure of the electromagnetic wave shielding film of this invention is demonstrated using drawing. 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 shielded printed wiring board using the electromagnetic wave shielding film of the present invention.

As shown in FIG. 1 , the electromagnetic shielding film 10 is composed of a protective layer 11 , a shielding layer 12 laminated on the protective layer 11 , and an adhesive layer 13 laminated on the shielding layer 12 . In addition, a plurality of conductive bumps 14 are formed on the adhesive layer 13 side of the shielding layer 12 .

Moreover, as shown in FIG. 2 , the electromagnetic wave shielding film 10 is pasted on a printed wiring board 20 to manufacture a shielded printed wiring board 30 . The printed circuit 22 of the ground circuit 22a and the cover film 23 covering the printed circuit 22 are formed in the cover film 23 with an opening 23a exposing the ground circuit 22a.

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

The above-mentioned thermoplastic resin composition is not particularly limited, and examples thereof include styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, and polypropylene-based resin compositions. , imide resin composition, acrylic resin composition, etc.

The above-mentioned thermosetting resin composition is not particularly limited, and may be selected from epoxy resin compositions, urethane resin compositions, urethane urea resin compositions, styrene At least one resin composition selected from the group consisting of resin-based compositions, phenol-based resin compositions, melamine-based resin compositions, acrylic-based resin compositions, and alkyd-based resin compositions.

The active energy ray-curable composition is not particularly limited, and examples thereof include 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.

In the protective layer 11, hardening accelerators, adhesion imparting agents, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoamers, leveling agents, fillers, flame retardants, viscosity Regulators, anti-caking agents, etc.

The thickness of the protective layer 11 is not particularly limited, and can be appropriately set as needed, but is preferably 1-15 μm, preferably 3-10 μm. If the thickness of the protective layer is less than 1 μm, it is too thin to sufficiently protect the shielding layer and the adhesive layer. If the thickness of the protective layer exceeds 15 μm, the protective layer is difficult to bend because it is too thick, and the protective layer itself is easily damaged. Therefore, it is difficult to apply to members requiring bending resistance.

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

When the shielding layer 12 is made of metal, examples of the metal include gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, and the like. Among these, copper is preferable. From the viewpoint of conductivity and economy, copper is a more suitable material for the shielding layer.

Furthermore, the shielding layer 12 may also be composed of an alloy of the above metals. In addition, the shielding layer 12 can be a metal foil, or a metal film formed by sputtering, electroless plating, electroplating, and the like.

When the shielding layer 12 is made of conductive resin, the shielding layer 12 may also be made of conductive particles and resin.

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

When the conductive particles are metal fine particles, there are no special restrictions on the metal fine particles, and they can be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder with silver plating on copper powder, or metal-coated polymer. Microparticles or microparticles such as metal-coated glass beads, etc. Among them, copper powder or silver-coated copper powder, which can be obtained at a low price, is preferable from the viewpoint of economy.

The average particle diameter D ₅₀ of the conductive particles is not particularly limited, and is preferably 0.5-15.0 μm. If the average particle diameter of the conductive particles is 0.5 μm or more, the conductivity of the conductive resin is good. When the average particle diameter of electroconductive particle is 15.0 micrometers or less, electroconductive resin can be thinned.

The shape of the conductive particles is not particularly limited, and can be appropriately selected from spherical, flat, scaly, dendritic, rod, and fibrous shapes.

The compounding quantity of conductive particle is not specifically limited, It is preferably 15-80 mass %, More preferably, it is 15-60 mass %.

The resin is not particularly limited, and examples thereof include styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, polypropylene-based resin compositions, and imide-based resin compositions. Thermoplastic resin compositions such as resin compositions, amide-based resin compositions, and acrylic resin compositions; or phenol-based resin compositions, epoxy-based resin compositions, urethane-based resin compositions, and melamine-based resin compositions Thermosetting resin compositions such as materials, alkyd resin compositions, etc.

(conductive bump) The conductive bump 14 penetrates the adhesive layer 13 and is in contact with the ground circuit 22 a. The connection resistance between the ground circuit 22 a and the conductive bump 14 can be reduced by making the conductive bump 14 in contact with the ground circuit 22 a reliably.

The shape of the conductive bump 14 is not particularly limited, and it can be a cylindrical shape such as a cylinder, a triangular prism, a square prism, or a cone shape such as a cone, a triangular pyramid, or a square pyramid. Among these, a cone shape is preferable. If the shape of the conductive bump 14 is a cone shape, the conductive bump 14 will easily penetrate the adhesive layer 13 and be easily in contact with the ground circuit 22a. Therefore, the connection resistance between the ground circuit 22 a and the conductive bump 14 is sufficiently reduced.

The volume of each conductive bump 14 is preferably 30000-400000 μm ³ , preferably 50000-400000 μm ³ . If the volume of each conductive bump 14 is within the above range, the conductive bump 14 can firmly contact the ground circuit 22a, and the connection resistance between the ground circuit 22a and the conductive bump 14 will be reduced. If the volume of each conductive bump is less than 30000 μm ³ , it is difficult for the conductive bump to contact the ground circuit, and the connection resistance between the ground circuit and the shielding layer tends to increase. When the volume per one conductive bump exceeds 400,000 μm ³ , the ratio of the conductive bump to the adhesive layer increases. Therefore, the relative permittivity and dielectric loss tangent of the entire region having the adhesive layer are likely to become high, and the transmission characteristics are likely to deteriorate.

The heights of the plurality of conductive bumps 14 (height represented by symbol "H" in FIG. 1 ) are preferably approximately the same. If the heights of the plurality of conductive bumps 14 are substantially the same, the plurality of conductive bumps 14 can easily penetrate the adhesive layer 13 evenly and be in contact with the ground circuit 22a. Therefore, the connection resistance between the ground circuit 22 a and the conductive bump 14 can be reduced.

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

Furthermore, the shape, height, and volume of the conductive bump can be measured using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times), after measuring any 5 places on the surface of the shielding layer where the bump is formed, using data analysis software ( LMeye7) for analysis. The parameter of binarization is height, and the automatic threshold algorithm adopts the Kittler method.

The location where the conductive bumps 14 are arranged is not particularly limited, and may be arranged only at a location in contact with the ground circuit 22a, or may be arranged at equal intervals.

The conductive bump 14 is preferably composed of a resin composition and conductive filler. That is, the conductive bump 14 may also be made of conductive paste. By using the conductive paste, the conductive bump 14 can be easily formed at any position and in any shape. Moreover, the conductive bump 14 can also be formed by screen printing. When the conductive bump 14 is formed by screen printing using the conductive paste, the conductive bump 14 can be easily and efficiently formed in any shape at any position.

When the conductive bump 14 is composed of a resin composition and a conductive filler, the resin composition is not particularly limited, and styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, Thermoplastic resin compositions such as polyethylene-based resin compositions, polypropylene-based resin compositions, imide-based resin compositions, amide-based resin compositions, and acrylic resin compositions; or phenol-based resin compositions, epoxy-based resin compositions, etc. Thermosetting resin compositions such as resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions, etc. The material of the resin composition may be a single type among them, or may be a combination of two or more types.

When the conductive bump 14 is composed of a resin composition and a conductive filler, the conductive filler is not particularly limited, and may be metal microparticles, carbon nanotubes, carbon fibers, metal fibers, and the like.

When the conductive filler is metal fine particles, there are no special restrictions on the metal fine particles, and they can be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder with silver plating on copper powder, metal-coated polymer Microparticles or microparticles such as metal-coated glass beads, etc. Among them, copper powder or silver-coated copper powder, which can be obtained at a low price, is preferable from the viewpoint of economy.

The average particle size D ₅₀ of the conductive filler is not particularly limited, and is preferably 0.5-15.0 μm.

The shape of the conductive filler is not particularly limited, and may be appropriately selected from spherical, flat, scaly, dendritic, rod, and fibrous shapes.

When the conductive bump 14 is composed of a resin composition and a conductive filler, the weight ratio of the conductive filler is preferably 30-99%, preferably 50-99%.

In addition, the conductive bump may be formed of a metal formed by a plating method, a vapor deposition method, or the like. In this case, the conductive bump is preferably composed of an alloy including one or more of copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like. As the plating method or vapor deposition method, the previous method can be used.

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

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

In the electromagnetic wave shielding film 10, the thickness of the adhesive layer 13 is preferably 5-30 μm, preferably 8-20 μm. If the thickness of the adhesive layer is less than 5 μm, it is difficult to obtain sufficient adhesive performance because the amount of resin constituting the adhesive layer is small. Moreover, it becomes easy to break. If the thickness of the adhesive layer exceeds 30 μm, the overall thickness will become thicker, and the flexibility will be easily lost. Also, it becomes difficult for the conductive bump to penetrate through the adhesive layer.

In the electromagnetic wave shielding film 10 , the relative dielectric constant of the resin constituting the adhesive layer 13 at a frequency of 1 GHz and 23° C. is preferably 1-5, preferably 2-4. Moreover, the dielectric loss tangent of the resin constituting the adhesive layer 13 at a frequency of 1 GHz and 23° C. is preferably 0.0001-0.03, more preferably 0.001-0.002. If it is the said range, the transmission characteristic of the shielded printed wiring board 30 manufactured using the electromagnetic wave shielding film 10 can be improved.

Furthermore, in the electromagnetic wave shielding film 10, the adhesive layer 13 can be a conductive insulating adhesive layer or an insulating adhesive layer. From the viewpoint of reducing the relative permittivity and dielectric loss tangent, the adhesive layer 13 is preferably It is an insulating adhesive layer. As described above, the electromagnetic wave shielding film 10 is bonded to the printed wiring board 30 through the adhesive layer 13 . When the above-mentioned adhesive layer 13 is an insulating adhesive layer, since the adhesive layer 13 does not contain conductive substances such as conductive fillers, the relative permittivity and dielectric loss tangent are sufficiently reduced. In this case, using the shielded printed wiring board 30 made of the electromagnetic wave shielding film 10, transmission characteristics become good.

Furthermore, when the adhesive layer 13 has conductivity, the adhesive layer 13 will contain conductive substances such as conductive fillers. If the adhesive layer 13 contains many such conductive substances, the relative permittivity and dielectric loss tangent of the entire adhesive layer 13 tend to become high. On the other hand, in order to make the transmission characteristics of the manufactured shielded printed wiring board 30 good, the relative permittivity and dielectric loss tangent of the adhesive layer 13 as a whole should be as low as possible. Therefore, even when the adhesive layer 13 contains a conductive substance, in order to lower the relative permittivity and dielectric loss tangent of the entire adhesive layer 13 , the less the content, the better.

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

As a thermosetting resin, a phenol resin, an epoxy resin, a urethane resin, a melamine resin, a polyamide resin, an alkyd resin, etc. are mentioned, for example. Furthermore, 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 resins. Also, as for the epoxy resin, an amide-modified epoxy resin is preferable. These resins are suitable as the resin constituting the adhesive layer. The material of the adhesive layer may be a single type among them, or a combination of two or more types.

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

(basement membrane and cover membrane) The materials of the base film 21 and the cover film 23 are not particularly limited, but are preferably made of engineering plastics. Examples of the above-mentioned engineering plastics include polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide imide, polyetherimide Amine, polyphenylene sulfide and other resins. Also, among these engineering plastics, polyphenylene sulfide film is preferable when flame retardancy is required, and polyimide film is preferable when heat resistance is required. Furthermore, the thickness of the base film 21 is preferably 10-40 μm, and the thickness of the cover film 23 is preferably 10-30 μm.

The size of the opening 23a is not particularly limited, but is preferably at least 0.1 mm ² , preferably at least 0.3 mm ² . Moreover, the shape of the opening part 23a is not specifically limited, A circle, an ellipse, a quadrangle, a triangle, etc. may be sufficient.

(printed circuit) The materials of the printed circuit 22 and the ground circuit 22a are not particularly limited, and may be copper foil, hardened conductive paste, or the like.

The shielded printed wiring board 30 made by sticking the electromagnetic wave shielding film 10 on the printed wiring board 20 is one aspect of the shielded printed wiring board of the present invention.

As shown in FIG. 2, the shielded printed wiring board 30 is composed of a printed wiring board 20 and an electromagnetic wave shielding film 10. The printed wiring board 20 has a base film 21, and a printed circuit including a plurality of ground circuits 22a formed on the base film 21. 22 and a cover film 23 that covers the printed circuit 22, and an opening that exposes the ground circuit 22a is formed on the cover film 23; The adhesive layer 13 of the shielding layer 12 is composed of a plurality of conductive bumps 14 formed on the shielding layer 12 on the side of the adhesive layer 13; the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate the adhesive layer 13 and are connected with The plurality of ground circuits 22a of the printed wiring board 20 are connected.

In the shielded printed wiring board 30 , the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate 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 22 a and the conductive bump 14 can be reduced by making the conductive bump 14 in contact with the ground circuit 22 a reliably.

Next, an example of the manufacturing method of the shielded printed wiring board of this invention is demonstrated using drawing. 3( a ) to ( d ) are process diagrams showing an example of the manufacturing method of the shielded printed wiring board of the present invention in order of steps.

(Electromagnetic wave shielding film preparation procedure) In this step, as shown in FIG. 3( a ), the above-mentioned electromagnetic wave shielding film 10 is prepared. The preferred configuration and the like of the electromagnetic wave shielding film 10 have already been described, so the description is omitted here.

(Printed wiring board preparation procedure) In this step, as shown in FIG.3(b), the printed wiring board 20 is prepared. Since the preferred configuration and the like of the printed wiring board 20 have already been described, description thereof will be omitted here.

(Electromagnetic wave shielding film configuration steps) In this step, as shown in FIG. 3( c ), the electromagnetic wave shielding film 10 is arranged on the printed wiring board 20 in such a manner that the adhesive layer of the electromagnetic wave shielding film 10 contacts the cover film 23 of the printed wiring board 20 . At this time, the conductive bump 14 is located on the ground circuit 22a.

(pressurization step) In this step, as shown in FIG. 3( d), pressure is applied so that the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate the adhesive layer 13 of the electromagnetic wave shielding film 10 and connect with the plurality of conductive bumps 14 of the printed wiring board 20. The ground circuit 22a contacts.

Regarding the pressurized conditions, the conditions of 1~5Pa and 1~60min can be exemplified.

In the manufacturing method of the shielded printed wiring board of the present invention, the adhesive layer 13 of the electromagnetic wave shielding film 10 can be hardened by heating after the pressurization step or simultaneously with the pressurization step.

Through the above steps, the shielded printed wiring board 30 can be manufactured.

[Example] The following examples illustrate the embodiments of the present invention more specifically, but the present invention is not limited to these embodiments.

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

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

Next, 10 parts by weight of a mixture of cresol novolac epoxy resin and isocyanate, and 90 parts by weight of a conductive filler (spherical silver-coated copper powder with an average particle diameter of 5 μm) were mixed to prepare a conductive paste. Furthermore, the weight ratio of the mixture of cresol novolac epoxy resin and isocyanate is cresol novolac epoxy resin:isocyanate=100:0.2. Then, conductive paste is screen-printed on the copper layer, thereby forming conductive bumps. The shape of the conductive bump is conical, the height is 23 μm, and the volume is 120000 μm ³ . Furthermore, the shape, height, and volume of the conductive bumps were measured at any five places on the surface of the shielding layer where the bumps were formed using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times), and then using data analysis software ( LMeye7) for analysis. The parameter of binarization is height, and the automatic threshold algorithm adopts the Kittler method.

Next, 100.0 parts of epoxy resins and 49.6 parts of organophosphorus-based flame retardants were mixed to prepare an adhesive layer composition.

A polyethylene terephthalate film subjected to release treatment on one side was prepared as a second release film. Then, the adhesive layer composition was coated on the release-treated surface of the second release film, and heated at 100° C. for 2 minutes using an electric oven to form an adhesive layer with 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 were bonded together, and the second release film was peeled off to manufacture the electromagnetic shielding film of Example 1.

Fig. 4 is a cross-sectional photograph of the electromagnetic wave shielding film of embodiment 1. As shown in Figure 4, the electromagnetic wave shielding film 10 of Embodiment 1 is made of protective layer 11, shielding layer 12 laminated on protective layer 11 and adhesive agent layer 13 laminated on shielding layer 12, and the shielding agent layer 13 on the side of adhesive agent layer Layer 12 is formed with conical conductive bumps 14 .

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

[Table 1]

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

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

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

A polyethylene terephthalate film subjected to release treatment on one side was prepared as a second release film. Then, the composition for the conductive adhesive layer was coated on 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 with a thickness of 9 μm.

Next, the protective layer formed on the 1st release film and the adhesive layer formed on the 2nd release film were bonded together, and the 2nd release film was peeled off, and the electromagnetic wave shielding film of the comparative example 2 was manufactured.

(Transmission loss measurement test) Fig. 5 is a schematic diagram schematically showing a method of measuring transmission loss of an electromagnetic wave shielding film in a transmission loss measurement test. The transmission loss measurement of the electromagnetic shielding film was evaluated using the network analyzer 41 shown in FIG. 5 . As the network analyzer 41, ZVL6 manufactured by Rohde & Schwarz was used. The network analyzer 41 has an input terminal and an output terminal, and these are respectively connected to the connection substrate 42 . The measurement was performed after the shielded printed wiring board 30 to be measured was connected between the pair of connection boards 42 and supported by the pair of connection boards 42 so as to be suspended in the air. As the shielded printed wiring board 30, one with a length of 100 mm was used. In addition, the measurement was performed within a frequency range of 100 kHz to 20 GHz. In addition, the measurement was carried out in an air environment with a temperature of 25°C and a relative humidity of 30 to 50%. The network analyzer 41 measures how much the input signal is attenuated relative to the output signal at a frequency of 10 GHz. The measured attenuation is shown in Table 1 as transmission loss. The closer the attenuation is to zero, the less the transmission loss is.

(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. The electromagnetic wave shielding film 110 in FIG. 6 schematically shows the electromagnetic wave shielding films of Embodiment 1 and Embodiment 2. The electromagnetic wave shielding film 110 is composed of a protective layer 111, a shielding layer 112 laminated on the protective layer 111, and an adhesive layer 113 laminated on the shielding layer 112, and a plurality of conductive protrusions are formed on the shielding layer 112 on the adhesive layer 113 side. Block 114. Also, in the connection resistance measurement test, a model substrate 120 including a base film 121, a plurality of printed circuits 125 for measurement formed on the base film 121, and a cover film 123 covering the printed circuits 125 for measurement were prepared, and The opening part 123a which exposes the printed circuit 125 for a measurement is formed in the cover film 123. As shown in FIG. In addition, the opening 123a is circular with a diameter of 1 mm.

In the connection resistance measurement test, as shown in FIG. 6 , the electromagnetic wave shielding film 110 was placed on the model substrate 120 in such a way that the conductive bump 114 of the electromagnetic wave shielding film 110 was in contact with the printed circuit 125 for measurement. After applying pressure/heating under the condition of 3 minutes, it was cured after 1 hour at 150° C., whereby the electromagnetic wave shielding film 110 was adhered to the model substrate 120 . Then, the resistance value between the printed circuit 125 for measurement was measured with the resistance meter 150 .

Furthermore, the electromagnetic wave shielding film of Comparative Example 1 has the same configuration as the electromagnetic wave shielding film 110 except that there is no conductive bump and the adhesive layer is a conductive adhesive layer. The electromagnetic wave shielding film of Comparative Example 1 was also pasted on the model substrate 120 under the same conditions as the above method, and the resistance value between the printed circuits 125 for measurement was measured with a resistance meter 150 .

Table 1 shows the results of the connection resistance test of the electromagnetic wave shielding films of the respective examples and comparative examples.

As shown in Table 1, the electromagnetic wave shielding films of Example 1 and Example 2 had small transmission loss in the transmission loss measurement test and small resistance values in the connection resistance measurement test.

10: Electromagnetic wave shielding film 11: Protective layer 12: shielding layer 13: Adhesive layer 14: Conductive bump 20:Printed Wiring Board 21: Basement Membrane 22: Printed circuit 22a: Grounding circuit 23: Cover film 23a: opening 30: Shielded printed wiring board 41: Network Analyzer 42: Substrate for connection 110: Electromagnetic wave shielding film 111: protective layer 112: shielding layer 113: Adhesive layer 114: Conductive bump 120:Model substrate 121: Basement Membrane 123: Cover film 123a: opening 125: Printed circuit for measurement 150: resistance meter H: height of conductive bump

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 shielded printed wiring board using the electromagnetic wave shielding film of the present invention. 3( a ) to ( d ) are process diagrams showing an example of the manufacturing method of the shielded printed wiring board of the present invention in order of steps. Fig. 4 is a cross-sectional photograph of the electromagnetic wave shielding film of embodiment 1. Fig. 5 is a schematic diagram schematically showing a method of measuring transmission loss of an electromagnetic wave shielding film in a 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.

10: Electromagnetic wave shielding film

11: Protective layer

12: shielding layer

13: Adhesive layer

14: Conductive bump

H: height of conductive bump

Claims (8)

An electromagnetic wave shielding film, characterized in that it is composed of a protective layer, a shielding layer laminated on the protective layer, and an adhesive layer laminated on the shielding layer; a conductive film is formed on the adhesive layer side of the shielding layer. The shape of the aforementioned conductive bump is cone-shaped; the position of the aforementioned conductive bump is closer to the side of the aforementioned shielding layer than the surface of the aforementioned adhesive layer opposite to the aforementioned shielding layer; the aforementioned conductive The volume of the bump is 30000~400000μm ³ . The electromagnetic wave shielding film according to claim 1, wherein a plurality of the conductive bumps are formed. 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 composed of a resin composition and conductive fillers. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the resin constituting the adhesive layer has a relative permittivity of 1 to 5 and a dielectric loss tangent of 0.0001 to 0.03 at a frequency of 1 GHz and 23°C. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the adhesive layer is an insulating adhesive layer. A method of manufacturing a shielded printed wiring board, characterized by comprising the following steps: The electromagnetic wave shielding film preparation step is to prepare the electromagnetic wave shielding film according to any one of claims 1 to 6; the printed wiring board preparation step is to prepare a printed wiring board, and the printed wiring board has a base film, including forming on the aforementioned base film. The printed circuit of the grounding circuit, and the cover film covering the above-mentioned printed circuit, and an opening for exposing the above-mentioned ground circuit is formed on the above-mentioned cover film; the step of disposing the electromagnetic wave shielding film is to use the adhesive layer of the above-mentioned electromagnetic wave shielding film to contact the above-mentioned In the method of the cover film of the printed wiring board, the aforementioned electromagnetic wave shielding film is arranged on the aforementioned printed wiring board; It is in contact with the ground circuit of the aforementioned printed wiring board. A shielded printed wiring board, characterized in that it is composed of the following: a printed wiring board having a base film, a printed circuit including a ground circuit formed on the base film, and a cover film covering the printed circuit, and in the aforementioned The cover film is formed with an opening that exposes the ground circuit; and the electromagnetic wave shielding film according to any one of claims 1 to 6, wherein the conductive bump of the electromagnetic wave shielding film penetrates the adhesive layer and connects with the printed wiring board ground circuit connection.

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