TWI771595B - Electromagnetic wave shielding film, manufacturing method of shielding printed wiring board, and shielding printed wiring board - Google Patents

Abstract

An object of the present invention is to provide an electromagnetic wave shielding film for producing a printed wiring board with very low connection resistance and very good transmission characteristics. An electromagnetic wave shielding film comprising: a protective layer, a shielding layer laminated on the protective layer, and an insulating adhesive layer laminated on the shielding layer; and the shielding layer on the side of the insulating adhesive layer is formed with A conductive bump, wherein the insulating adhesive layer has a first insulating adhesive layer on the shield layer side and a second insulating adhesive layer on the opposite side of the first insulating adhesive layer, and the second insulating adhesive layer The surface roughness (Ra) of the agent layer is 0.5~2.0μm.

Description

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

The present invention relates to an electromagnetic wave shielding film, a manufacturing method of a shielding printed wiring board, and a shielding 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, which are rapidly becoming smaller and more functional. Furthermore, it is also used in the connection of movable parts such as printer heads and control parts by its excellent flexibility. Electromagnetic wave shielding measures are required in these electronic devices, and even for flexible printed wiring boards used in devices, flexible printed wiring boards that have been implemented with electromagnetic wave shielding measures such as sticking electromagnetic wave shielding films (hereinafter also referred to as "" Shielded Printed Wiring Board”).

Generally speaking, an electromagnetic wave shielding film is composed of an outermost insulating layer (protective layer), a shielding layer for shielding electromagnetic waves, and an adhesive layer for sticking to a printed wiring board. When manufacturing the shielding printed wiring board, the electromagnetic wave shielding film is pasted to the flexible printed wiring board in such a way that the adhesive layer of the electromagnetic wave 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 casing, but there are also cases where the ground circuit of the printed wiring board is electrically connected to the external ground through the electromagnetic wave shielding film pasted on the flexible printed wiring board. connection situation.

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 further connected to the external ground, Thereby, the ground circuit of the flexible printed wiring board is electrically connected to the external ground.

prior art literature Patent Literature Patent Document 1: Japanese Patent Laid-Open No. 2004-095566

Summary of 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 is derived from the conductive filler. That is, the electrical contact between the conductive adhesive layer and the ground circuit is obtained by the contact between the conductive filler and the ground circuit. The contact surface of the conductive adhesive and the ground circuit also has a portion without conductive filler. With such a portion, there is a problem that the connection resistance between the conductive adhesive layer and the ground circuit becomes high. Moreover, since the adhesive resin contains the conductive filler, the relative permittivity and dielectric loss tangent of the entire conductive adhesive layer become high. When the relative permittivity and the dielectric loss tangent of the conductive adhesive layer are increased, there is a problem that the transmission characteristics are deteriorated.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electromagnetic wave shielding film for producing a shielding printed wiring board with very low connection resistance and very good transmission characteristics.

means of solving 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 insulating adhesive layer laminated on the shielding layer; and the shielding layer on the side of the insulating adhesive layer A conductive bump is formed, the insulating adhesive layer has a first insulating adhesive layer on the shield layer side and a second insulating adhesive layer on the opposite side of the first insulating adhesive layer, and the second insulating adhesive layer is provided. The surface roughness (Ra) of the adhesive layer is 0.5~2.0μm.

The electromagnetic wave shielding film of the present invention is adhered to a printed wiring board, and 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 the cover film is formed with a ground circuit. exposed opening.

At this time, the conductive bump penetrates the insulating adhesive layer and is in contact with the ground circuit. The connection resistance between the ground circuit and the conductive bump can be reduced by designing such that the conductive bump and the ground circuit are in reliable contact.

Furthermore, in the electromagnetic wave shielding film of this invention, the surface roughness (Ra) of the 2nd insulating adhesive layer is 0.5-2.0 micrometers. That is, the second insulating adhesive layer is flat. If the surface roughness (Ra) of the second insulating adhesive layer is in the above-mentioned range, the conductive bump can easily penetrate the insulating adhesive layer, so that the connection resistance between the ground circuit and the conductive bump can be reduced. It is technically difficult to make the surface roughness (Ra) of the second insulating adhesive layer less than 0.5 μm. When the surface roughness (Ra) of the second insulating adhesive layer exceeds 2.0 μm, it becomes difficult for the conductive bumps to penetrate the insulating adhesive layer, and a portion where the connection resistance between the ground circuit and the conductive bump increases is likely to occur. .

Moreover, the electromagnetic wave shielding film of this invention is adhere|attached to a printed wiring board via an insulating adhesive layer. Since the insulating adhesive layer does not contain conductive substances such as conductive fillers, the relative permittivity and the dielectric loss tangent are very small. Therefore, the transmission characteristics of the shielded printed wiring board produced using the electromagnetic wave shielding film of the present invention are good.

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 substantially the same. When the heights of the plurality of conductive bumps are substantially the same, the plurality of conductive bumps can easily penetrate the insulating adhesive layer uniformly and make contact with the ground circuit. Therefore, the connection resistance between the ground circuit and the conductive bump can be reduced.

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

In the electromagnetic wave shielding film of the present invention, the distance from the second insulating adhesive layer to the conductive bump is preferably 20 μm or less. If the distance from the second insulating adhesive layer to the conductive bump is 20 μm or less, the conductive bump is likely to penetrate through the insulating adhesive layer, so that the conductive bump is likely to be in contact with the ground circuit.

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

The manufacturing method of the shielding printed wiring board of the present invention is characterized by comprising the following steps: the electromagnetic wave shielding film preparation step is to prepare the electromagnetic wave shielding film of the present invention; the printed wiring board preparation step is to prepare the printed wiring board, the printed wiring board A base film, a printed circuit including a ground circuit formed on the base film, and a cover film covering the printed circuit are provided, and an opening for exposing the ground circuit is formed in the cover film; the electromagnetic wave shielding film is arranged in the steps of: The second insulating adhesive layer of the electromagnetic wave shielding film is in contact with the cover film of the printed wiring board, and the electromagnetic wave shielding film is arranged on the printed wiring board; and the pressing step is to pressurize the electromagnetic wave shielding film. The conductive bump penetrates through the insulating adhesive layer of the electromagnetic wave shielding film and is in contact with the ground circuit of the printed wiring board.

The manufacturing method of the shielding printed wiring board of this invention is the manufacturing method of the shielding printed wiring board which used the electromagnetic wave shielding film of this invention mentioned above. Therefore, the connection resistance between the ground circuit and the conductive bump of the obtained shielded printed wiring board is low, and the transmission characteristic is very good.

A shielded printed wiring board of the present invention is characterized in that it is composed of a printed wiring board and the 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 The cover film of the printed circuit has an opening for exposing the ground circuit; the conductive bump of the electromagnetic wave shielding film penetrates the insulating adhesive layer and is connected to the ground circuit of the printed wiring board.

In the shielding printed wiring board of the present invention, the conductive bumps of the electromagnetic wave shielding film of the present invention are connected to the ground circuit of the printed wiring board through the insulating adhesive layer. Therefore, the connection resistance between the ground circuit and the conductive bump is very low.

In the shielding printed wiring board of the present invention, the electromagnetic wave shielding film and the printed wiring board are bonded together by the insulating adhesive layer of the electromagnetic wave shielding film. Since the insulating adhesive layer does not contain conductive substances such as conductive fillers, the relative permittivity and the dielectric loss tangent are very small. Therefore, the transmission characteristics of the shielded printed wiring board of the present invention are good.

Invention effect In the electromagnetic wave shielding film of the present invention, the surface roughness (Ra) of the second insulating adhesive layer is 0.5 to 2.0 μm. When the surface roughness (Ra) of the second insulating adhesive layer is within the above-mentioned range, the conductive bump can easily penetrate through the insulating adhesive layer. Therefore, the connection resistance between the ground circuit and the conductive bump can be reduced.

The electromagnetic wave shielding film of the present invention is bonded to a printed wiring board through an insulating adhesive layer. Since the insulating adhesive layer does not contain conductive substances such as conductive fillers, the relative permittivity and the dielectric loss tangent are very small. Therefore, the shielding printed wiring board made by using the electromagnetic wave shielding film of the present invention has good transmission characteristics.

Form for carrying out the invention Hereinafter, the electromagnetic wave shielding film of this invention is demonstrated concretely. However, the present invention is not limited to the following embodiments, and can be appropriately changed and applied within the scope of not changing the gist of the present invention.

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 insulating adhesive layer laminated on the shielding layer; and the shielding layer on the side of the insulating adhesive layer A conductive bump is formed, the insulating adhesive layer has a first insulating adhesive layer on the shield layer side and a second insulating adhesive layer on the opposite side of the first insulating adhesive layer, and the second insulating adhesive layer is provided. The surface roughness (Ra) of the adhesive layer is 0.5~2.0μm.

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. 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 wave shielding film 10 is composed of a protective layer 11 , a shielding layer 12 laminated on the protective layer 11 , and an insulating adhesive layer 13 laminated on the shielding layer 12 . In addition, a plurality of conductive bumps 14 are formed on the shield layer 12 on the side of the insulating adhesive layer 13 . Then, the insulating adhesive layer 13 has a first insulating adhesive layer 13a on the side of the shielding layer 12, a second insulating adhesive layer 13b on the opposite side of the first insulating adhesive layer 13a, and a second insulating adhesive layer The surface roughness (Ra) is 0.5~2.0μm.

Furthermore, as shown in FIG. 2 , the electromagnetic wave shielding film 10 is adhered to the printed wiring board 20 to manufacture the shielding printed wiring board 30 . The printed wiring board 20 includes a base film 21 , and includes a plurality of The printed circuit 22 of the ground circuit 22a and the cover film 23 covering the printed circuit 22, and the cover film 23 has an opening 23a that exposes 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 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 examples thereof include epoxy resin compositions, urethane resin compositions, urethane urea resin compositions, and styrene resin compositions. At least one resin composition in the group consisting of a resin composition, a phenol-based resin composition, a melamine-based resin composition, an acrylic resin composition, and an alkyd-based resin composition.

Although it does not specifically limit about the said active energy ray curable composition, For example, the polymerizable compound etc. which have at least 2 (meth)acryloyloxy groups in a molecule|numerator are mentioned.

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, defoaming agents, leveling agents, fillers, flame retardants, viscosity Conditioners, 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 to 15 μm, preferably 3 to 10 μm. If the thickness of the protective layer is less than 1 μm, since it is too thin, it is difficult to sufficiently protect the shielding layer and the insulating adhesive layer. If the thickness of the protective layer exceeds 15 μm, since it is too thick, the protective layer is difficult to bend, and the protective layer itself is easily damaged. Therefore, it is difficult to apply to a member requiring bending resistance.

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

When the shield layer 12 is made of a metal, gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, etc. can be mentioned as the metal. Among these, copper is preferable. From the viewpoint of conductivity and economy, copper is a more suitable material for the first shielding layer.

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

When the shielding layer 12 is formed of a conductive resin, the shielding layer 12 may be formed 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 microparticles, the metal microparticles are not particularly limited, and may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder coated with silver on copper powder, metal-coated polymer microparticles, or Microparticles such as glass beads, etc. Among these, from the viewpoint of economy, copper powder or silver-coated copper powder which can be obtained at a low price is preferable.

The average particle diameter _D50 of the electroconductive particles is not particularly limited, but is preferably 0.5 to 15.0 μm. When the average particle diameter of electroconductive particle is 0.5 micrometer or more, the electroconductivity of electroconductive resin is favorable. When the average particle diameter of the conductive particles is 15.0 μm or less, the conductive resin can be thinned.

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

Although the compounding quantity of an electroconductive particle is not specifically limited, 15-80 mass % is suitable, 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 alkyd resin compositions and alkyd resin compositions, etc.

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

The shape of the conductive bump 14 is not particularly limited, and may be a columnar shape such as a cylinder, a triangular prism, and a quadrangular prism, or may be a pyramidal shape such as a cone, a triangular pyramid, and a quadrangular pyramid.

The heights of the plurality of conductive bumps 14 (the heights indicated by the 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 through the insulating adhesive layer 13 uniformly and contact 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, preferably 5-30 μm. The volume of the conductive bump 14 is preferably 10,000-1,000,000 μm ³ , preferably 30,000-500,000 μm ³ .

The conductive bumps 14 are preferably composed of a resin composition and a conductive filler. That is, the conductive bumps 14 may be formed of a conductive paste. By using the conductive paste, the conductive bumps 14 can be easily formed in any position and in any shape. In addition, the conductive bumps 14 may also 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 in any position and in any shape.

When the conductive bumps 14 are composed of a resin composition and a conductive filler, the resin composition is not particularly limited, and can be used: styrene-based resin composition, vinyl acetate-based resin composition, polyester-based resin composition, Thermoplastic resin compositions such as polyethylene-based resin compositions, polypropylene-based resin compositions, amide-imide-based resin compositions, amide-based resin compositions, and acrylic-based resin compositions; or phenol-based resin compositions, epoxy-based resin compositions Thermosetting resin compositions such as resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions, and the like. The material of the resin composition may be used alone or in combination of two or more.

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

When the conductive filler is metal microparticles, the metal microparticles are not particularly limited, and may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder coated with silver on copper powder, metal-coated polymer microparticles, or Microparticles such as glass beads, etc. Among these, from the viewpoint of economy, copper powder or silver-coated copper powder which can be obtained at a low price is preferable.

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

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

When the conductive bump 14 is composed of the resin composition and the 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 copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, and an alloy containing any one or more of these. The plating method or the vapor deposition method can use the previous method.

(Insulating Adhesive Layer) As described above, the electromagnetic wave shielding film 10 is bonded to the printed wiring board 20 via the insulating adhesive layer 13 . Since the insulating adhesive layer 13 does not contain conductive substances such as conductive fillers, the relative permittivity and the dielectric loss tangent are very small. Therefore, the shielding printed wiring board 30 formed by using the electromagnetic wave shielding film 10 has good transmission characteristics.

In the electromagnetic wave shielding film 10, the surface roughness (Ra) of the 2nd insulating adhesive layer 13b is 0.5-2.0 micrometers. In addition, the surface roughness (Ra) of the second insulating adhesive layer 13b is preferably 0.1 to 2.0 μm, preferably 0.5 to 1.5 μm. That is, the second insulating adhesive layer 13b is flat. When the surface roughness (Ra) of the second insulating adhesive layer 13 b is in the above-mentioned range, the plurality of conductive bumps 14 penetrate the insulating adhesive layer 13 equally. Therefore, the plurality of conductive bumps 14 are in equal contact with the plurality of ground circuits 22a. Therefore, the connection resistance between the ground circuit and the conductive bump can be reduced. It is technically difficult to make the surface roughness (Ra) of the second insulating adhesive layer less than 0.5 μm. When the surface roughness (Ra) of the second insulating adhesive layer exceeds 2.0 μm, it becomes difficult for the plurality of conductive bumps to penetrate the insulating adhesive layer uniformly, and the connection between the ground circuit and the conductive bumps is likely to occur. The part where the resistance increases.

The surface roughness (Ra) of the second insulating adhesive layer 13b can be determined by, for example, a method of forming a second insulating adhesive layer by lamination, a method of forming a second insulating adhesive layer by coating, or the like. control.

In this specification, the surface roughness (Ra) of the second insulating adhesive layer is measured using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times) at any 5 of the second insulating adhesive layer. After treatment, the data analysis software (LMeye7) was used, and the measurement was performed according to JIS B 0601:2013. In addition, the cutoff wavelength λc was set to 0.8 mm.

In the electromagnetic wave shielding film 10, the thickness of the insulating adhesive layer 13 is preferably 5-30 μm, preferably 8-20 μm. If the thickness of the insulating adhesive layer is less than 5 μm, since the amount of resin constituting the insulating adhesive layer is small, it is difficult to obtain sufficient adhesive performance. And, it becomes easy to be damaged. When the thickness of the insulating adhesive layer exceeds 30 μm, the entirety becomes thick and flexibility is likely to be lost. In addition, it is difficult for the conductive bump to penetrate through the insulating adhesive layer.

In the electromagnetic wave shielding film 10, the distance from the second insulating adhesive layer 13b to the conductive bumps 14 (the distance indicated by the symbol "D" in FIG. 1) is preferably 20 μm or less, preferably 0˜20 μm. In addition, the distance from the second insulating adhesive layer 13b to the conductive bump 14 is 0, which means that the conductive bump 14 is exposed from the second insulating adhesive layer 13b. If the distance from the second insulating adhesive layer 13b to the conductive bumps 14 is 20 μm or less, the conductive bumps 14 easily penetrate through the insulating adhesive layer 13 , so that the conductive bumps 14 are likely to be in contact with the ground circuit 22a.

In the electromagnetic wave shielding film 10, the relative dielectric constant of the resin constituting the insulating adhesive layer 13 at a frequency of 1 GHz and 23° C. is preferably 1-5, preferably 2-4. In addition, the dielectric loss tangent of the resin constituting the insulating adhesive layer 13 at a frequency of 1 GHz and 23° C. is preferably 0.0001 to 0.03, preferably 0.001 to 0.02. Within the above range, the transmission characteristics of the shielded printed wiring board 30 manufactured using the electromagnetic wave shielding film 10 can be improved.

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

As a thermosetting resin, a phenol type resin, an epoxy type resin, a urethane type resin, a melamine type resin, a polyamide type resin, an alkyd type resin, etc. are mentioned, for example. Moreover, as a thermoplastic resin, a styrene-type resin, a vinyl acetate-type resin, a polyester-type resin, a polyethylene-type resin, a polypropylene-type resin, an imide-type resin, and an acrylic resin are mentioned, for example. Moreover, as for the epoxy resin, an amide-modified epoxy resin is preferable. These resins are suitable as resins constituting the insulating adhesive layer. The material of the insulating adhesive layer may be used alone or in combination of two or more.

(Printed Wiring Board) Next, the printed wiring board 20 to which the electromagnetic wave shielding film 10 is to be attached will be described.

(basement membrane and coverlay) The materials of the base film 21 and the cover film 23 are not particularly limited, but are preferably made of engineering plastics. As the above engineering plastics, for example: polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, polyetherimide Amine, polyphenylene sulfide and other resins. In addition, among these engineering plastics, a polyphenylene sulfide film is preferable when flame retardancy is required, and a 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 portion 23a is not particularly limited, but is preferably 0.1 mm ² or more, preferably 0.3 mm ² or more. In addition, the shape of the opening 23a is not particularly limited, and may be a circle, an ellipse, a quadrangle, a triangle, or the like.

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

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

As shown in FIG. 2 , the shielded printed wiring board 30 is composed of the printed wiring board 20 and the electromagnetic wave shielding film 10 . The printed wiring board 20 includes a base film 21 and a printed circuit including a plurality of ground circuits 22 a formed on the base film 21 . 22 and a cover film 23 that covers the printed circuit 22, and an opening for exposing the ground circuit 22a is formed in the cover film 23; the electromagnetic wave shielding film 10 is composed of the protective layer 11, the shielding layer 12 laminated on the protective layer 11, and the shielding layer laminated on The insulating adhesive layer 13 of the layer 12 is constituted, and a plurality of conductive bumps 14 are formed on the shielding layer 12 on the side of the insulating adhesive layer 13; the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate through the insulating bonding The agent layer 13 is connected to a plurality of ground circuits 22 a of the printed wiring board 20 .

In the shielded printed wiring board 30 , the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate through the insulating adhesive layer 13 and are connected to the plurality of ground circuits 22 a of the printed wiring board 20 . In the electromagnetic wave shielding film 10, the surface roughness (Ra) of the 2nd insulating adhesive layer 13b is 0.5-2.0 micrometers. That is, the second insulating adhesive layer 13b is flat. Therefore, the conductive bump 14 easily penetrates through the insulating adhesive layer 13 to uniformly contact the ground circuit 22a. Therefore, the connection resistance between the ground circuit 22a and the conductive bump 14 is very low.

The shielding printed wiring board 30 is bonded to the electromagnetic wave shielding film 10 and the printed wiring board 20 via the insulating adhesive layer 13 of the electromagnetic wave shielding film 10 . Since the insulating adhesive layer 13 does not contain conductive substances such as conductive fillers, the relative permittivity and the dielectric loss tangent are very small. Therefore, the transmission characteristics of the shielded printed wiring board 30 are good.

Hereinafter, an example of the manufacturing method of the shielded printed wiring board of this invention is demonstrated using drawing. FIGS. 3( a ) to ( d ) are step 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 steps) In this step, as shown in FIG. 3( a ), the above-mentioned electromagnetic wave shielding film 10 is prepared. Since the preferable structure etc. of the electromagnetic wave shielding film 10 have already been demonstrated, description is abbreviate|omitted here.

(Printed wiring board preparation steps) In this step, as shown in FIG.3(b), the printed wiring board 20 is prepared. Since the preferable structure etc. of the printed wiring board 20 have already been demonstrated, description is abbreviate|omitted here.

(Electromagnetic wave shielding film arrangement steps) In this step, as shown in FIG. 3( c ), the electromagnetic wave shielding film is arranged on the printed wiring board 20 so that the second insulating adhesive layer 13 b of the electromagnetic wave shielding film 10 is in contact with the cover film 23 of the printed wiring board 20 10. At this time, the conductive bump 14 is positioned on the ground circuit 22a.

(pressurization step) In this step, as shown in FIG. 3( d ), pressing is performed so that the plurality of conductive bumps 14 of the electromagnetic wave shielding film 10 penetrate through the insulating adhesive layer 13 of the electromagnetic wave shielding film 10 to connect with the plurality of printed wiring boards 20 . A ground circuit 22a contacts.

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

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

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

[Example] Embodiments of the present invention are disclosed below in more detail, but the present invention is not limited to these embodiments.

(Example 1) First, the polyethylene terephthalate film which peeling process was performed on one side was prepared as a 1st peeling film.

Next, epoxy resin was applied to the peeling treatment surface of the first peeling film, and it was 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 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 to form conductive bumps. The shape of the conductive bump was conical, the height was 23 μm, and the volume was 100000 μm ³ . Furthermore, the shape, height, and volume of the conductive bumps were measured using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times) at any five locations on the surface of the shielding layer where the bumps were formed, and data analysis software ( LMeye7) for analysis. The parameter for binarization is height, and the automatic threshold algorithm is Kittler's method.

Next, 100.0 parts of epoxy resins and 49.6 parts of organophosphorus flame retardants were mixed to prepare a composition for insulating adhesive layers.

Next, the polyethylene terephthalate film which performed the peeling process on one side was prepared as a 2nd peeling film. Then, the composition for an insulating adhesive layer was applied to the peeling-treated surface of the second release film, and heated at 100° C. for 2 minutes using an electric oven to produce an insulating adhesive layer with a thickness of 9 μm.

Next, the protective layer formed on the first peeling film and the insulating adhesive layer formed on the second peeling film were bonded together, and the second peeling film was peeled off, thereby producing the electromagnetic wave shielding film of Example 1.

The surface roughness (Ra) of the second insulating adhesive layer of the electromagnetic wave shielding film of Example 1 was 0.72 μm.

(Example 2) An electromagnetic wave shielding film of Example 2 was produced in the same manner as in Example 1, except that the thickness of the insulating adhesive layer was 16 μm and the surface roughness (Ra) of the second insulating adhesive layer was 0.76 μm.

(Comparative Example 1) First, the polyethylene terephthalate film which peeling process was performed on one side was prepared as a 1st peeling film.

Next, epoxy resin was applied to the peeling treatment surface of the first peeling film, and it was 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 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 to form conductive bumps. The shape of the conductive bump was conical, the height was 23 μm, and the volume was 100000 μm ³ . Furthermore, the shape, height, and volume of the conductive bumps were measured using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times) at any five locations on the surface of the shielding layer where the bumps were formed, and data analysis software ( LMeye7) for analysis. The parameter for binarization is height, and the automatic threshold algorithm is Kittler's method.

Next, 100.0 parts of amide-modified epoxy resins and 49.6 parts of organophosphorus flame retardants were mixed to prepare a composition for insulating adhesive layers. Furthermore, the relative dielectric constant of the amide-modified epoxy resin at a frequency of 1 GHz and 23° C. was 2.69, and the dielectric loss tangent was 0.0103.

Next, the composition for an insulating adhesive layer was coated on the copper layer by a bar coater, and heated at 100° C. for 2 minutes using an electric oven to form an insulating adhesive layer with a thickness of 13 μm, thereby producing Comparative Example 1 The electromagnetic wave shielding film.

The surface roughness (Ra) of the second insulating adhesive layer of the electromagnetic wave shielding film of Comparative Example 1 was 2.59 μm.

(Connection resistance measurement test) FIG. 4 is a schematic diagram schematically showing a method for measuring the resistance value of the electromagnetic wave shielding film in the connection resistance measurement test. The electromagnetic wave shielding film 110 in FIG. 4 schematically shows the electromagnetic wave shielding films of the respective examples and comparative examples. 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 insulating adhesive layer 113 laminated on the shielding layer 112, and the shielding layer 112 on the insulating adhesive layer 113 side is formed with a plurality of conductive bumps 114 . In addition, in the connection resistance measurement test, a model substrate 120 is prepared which includes a base film 121, a plurality of measurement printed circuits 125 formed on the base film 121, and a cover film 123 covering the measurement printed circuits 125, and The cover film 123 is formed with an opening 123 a that exposes the measurement printed circuit 125 . In addition, the opening part 123a has a circular shape with a diameter of 1 mm.

In the connection resistance measurement test, as shown in FIG. 4 , the electromagnetic wave shielding film 110 was placed on the model substrate 120 so that the conductive bumps of the electromagnetic wave shielding film 110 were in contact with the printed circuit 125 for measurement, and the temperature was 170° C., 3 MPa, The electromagnetic wave shielding film 110 was adhered to the model substrate 120 after being pressurized and heated under the conditions of 3 minutes, and then cured at 150° C. for 1 hour.

The resistance value between the measurement printed circuit 125 of the model board|substrate 120 to which the electromagnetic wave shielding film 110 adhered after standing at 60 degreeC for 3 days was measured with the resistance meter 150.

The reflow resistance evaluation of the model board|substrate 120 to which the electromagnetic wave shielding film 110 adhered after standing at 60 degreeC for 3 days was performed. Regarding the reflow conditions, lead-free solder was assumed, and a temperature profile was set in which the shielding film in the shielding printed wiring board was exposed to 265° C. for 10 seconds. The resistance value between the printed circuits 125 for measurement after the reflow process was carried out five times in total under the above-mentioned conditions was measured with the resistance meter 150 . Furthermore, the step of the heating cycle imitates the reflow step of attaching the electromagnetic wave shielding film to the printed wiring board and then mounting the electronic parts.

Table 1 shows the resistance values of the electromagnetic wave shielding films of Example 1, Example 2 and Comparative Example 1 measured by the above method.

[Table 1]

As shown in Table 1, it can be seen that the electromagnetic wave shielding films of Example 1 and Example 2 whose surface roughness (Ra) of the second insulating adhesive layer is in the range of 0.5 to 2.0 μm have lower connection resistance.

10: Electromagnetic wave shielding film 11: Protective layer 12: Shielding layer 13: Insulating adhesive layer 13a: The first insulating adhesive layer 13b: Second insulating adhesive layer 14: Conductive bumps 20: Printed wiring board 21: basement membrane 22: Printed Circuits 22a: Ground circuit 23: Cover film 23a: Opening 30: Shielded printed wiring board 110: Electromagnetic wave shielding film 111: Protective layer 112: Shielding layer 113: insulating adhesive layer 114: Conductive bumps 120: Model substrate 121: basement membrane 123: cover film 123a: Opening 125: Printed circuits for measurement 150: Resistance meter D: Distance from the second insulating adhesive layer to the conductive bump 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. 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. FIGS. 3( a ) to ( d ) are step 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 schematic diagram schematically showing a method for 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: Insulating adhesive layer

13a: The first insulating adhesive layer

13b: Second insulating adhesive layer

14: Conductive bumps

D: Distance from the second insulating adhesive layer to the 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 insulating adhesive layer laminated on the shielding layer; and the shielding layer on the side of the insulating adhesive layer A conductive bump is formed, the insulating adhesive layer has a first insulating adhesive layer on the shield layer side and a second insulating adhesive layer on the opposite side of the first insulating adhesive layer, and the second insulating adhesive layer is formed The surface roughness (Ra) of the adhesive layer is 0.5~2.0μm. The electromagnetic wave shielding film of claim 1, wherein a plurality of the conductive bumps are formed. The electromagnetic wave shielding film of 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 a conductive filler. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the distance from the second insulating adhesive layer to the conductive bump is 20 μm or less. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the resin constituting the insulating adhesive layer has a relative dielectric constant of 1 to 5 at a frequency of 1 GHz and 23° C., and a dielectric loss tangent of 0.0001 to 0.03 . A method of manufacturing a shielded printed wiring board, which is characterized in that It includes the following steps: the electromagnetic wave shielding film preparation step, which is to prepare the electromagnetic wave shielding film according to any one of claims 1 to 6; the printed wiring board preparation step, which is to prepare a printed wiring board, the printed wiring board has a base film, includes forming A printed circuit of the ground circuit 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 electromagnetic wave shielding film disposing step is based on the first electromagnetic wave shielding film. 2. The method in which the insulating adhesive layer is in contact with the cover film of the printed wiring board, and the electromagnetic wave shielding film is arranged on the printed wiring board; The insulating adhesive layer of the electromagnetic wave shielding film is in contact with the ground circuit of the printed wiring board. A shielded printed wiring board, characterized in that it is composed of a printed wiring board and the electromagnetic wave shielding film according to any one of claims 1 to 6, the printed wiring board has a base film, and includes a ground circuit formed on the base film. A printed circuit and a cover film covering the printed circuit, and the cover film is formed with an opening for exposing the ground circuit; the conductive bumps of the electromagnetic wave shielding film penetrate the insulating adhesive layer and are connected to the printed wiring board. the ground circuit connection.

Images