JP2020167250A - Electromagnetic wave shield sheet, electromagnetic wave shield wiring circuit board, and electronic device - Google Patents

Abstract

To provide an electromagnetic wave shield sheet, an electromagnetic wave shielded wiring circuit board, and an electronic device having high electromagnetic wave shielding property and good folding resistance, and reducing transmission loss.SOLUTION: An electromagnetic wave shield sheet 10 according to the present invention includes an adhesive layer 1, an insulating layer 3, and a metal layer 2 arranged between the adhesive layer 1 and the insulating layer 3, and the film thickness of the metal layer 2 is 0.2 to 10 [μm], the development length ratio RLr of the interface on the adhesive layer 1 side in the metal layer 2 is 1 to 1.4, and the development length ratio RLr of the interface on the insulating layer 3 side in the metal layer 2 is 1 to 1.5. Further, the development length ratio RLr of the interface on the adhesive layer 1 side is smaller than the development length ratio RLr of the interface on the insulating layer 3 side.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electromagnetic wave shield sheet, an electromagnetic wave shield wiring circuit board, and an electronic device, and uses, for example, an electromagnetic wave shield sheet suitable for joining and using a part of a component that emits an electromagnetic wave, and an electromagnetic wave shield sheet. Regarding electromagnetic wave shielded wiring circuit boards and electronic devices.

Various electronic devices such as mobile terminals, PCs, and servers have built-in wiring circuit boards such as printed wiring boards. These wiring circuit boards are provided with an electromagnetic wave shield structure in order to prevent malfunction due to an external magnetic field or radio wave, and to reduce unnecessary radiation from an electric signal.

In Patent Document 1, it is an object of the present invention to provide a shield film and a shield printed wiring board which satisfactorily shield electric field waves, magnetic field waves and electromagnetic waves traveling from one side to the other side of the shield film and have good transmission characteristics. , The following configuration is disclosed. That is, a configuration is disclosed in which a metal layer having a layer thickness of 0.5 to 12 [μm] and an anisotropic conductive adhesive layer are provided in a laminated state. It is described that the configuration satisfactorily shields electric field waves, magnetic field waves, and electromagnetic waves traveling from one side to the other side of the shield film.

International Publication No. 2013/077108

With the increase in high-speed transmission of transmission signals, electromagnetic wave shield sheets are also required to have high shielding properties for high frequencies and reduction of transmission loss. Therefore, as described in Patent Document 1, it has been preferable to use a metal layer for the metal layer of the electromagnetic wave shield sheet.

However, the thicker the metal layer of the electromagnetic wave shield sheet, the higher the shielding property, while the higher the repulsive force. Therefore, the shield printed wiring board in which the electromagnetic wave shield sheet is attached to the printed wiring board has problems such as cracks in the bent portion, poor appearance, poor insulation, and noise leakage when incorporated into the housing. Was there.

Further, in recent years, technical studies for the fifth generation mobile phone following the fourth generation mobile phone have been promoted. There, further reduction of transmission loss is required in order to realize a transmission capacity 10 times or more that of the 4th generation. Therefore, it is difficult to sufficiently reduce the transmission loss simply by using the metal layer for the electromagnetic wave shield sheet. Further, in the shielded wiring circuit board, by increasing the thickness of the wiring circuit board, the distance between the signal circuit and the electromagnetic wave shield sheet can be increased, and the transmission loss can be reduced. However, there is a problem that cracks are more likely to occur in the bent portion than ever before.

Further improvement in performance can be expected if high electromagnetic wave shielding properties can be exhibited, folding resistance can be improved, and transmission loss can be improved. It is also possible to increase the design margin of the internal electronic circuit or the like. With the recent increase in signal speed and frequency, improvement of transmission loss has become important for maintaining and improving performance characteristics.

The present invention has been made in view of the above background, and an object of the present invention is to have good folding resistance while having high electromagnetic wave shielding property even when used in a high frequency transmission circuit. The present invention is to provide an electromagnetic wave shield sheet, an electromagnetic wave shielded wiring circuit board, and an electronic device capable of reducing transmission loss.

The electromagnetic wave shield sheet according to the present invention includes an adhesive layer, an insulating layer, and a metal layer arranged between the adhesive layer and the insulating layer, and the thickness of the metal layer is 0.2. It is 10 [μm], and the developed length ratio RLr of the interface on the adhesive layer side in the metal layer is 1 to 1.4, and the developed length ratio of the interface on the insulating layer side in the metal layer. The RLr is 1 to 1.5.

The electromagnetic wave shielding property wiring circuit board according to the present invention is characterized in that the electromagnetic wave shielding sheet described above is bonded to at least one surface of the wiring circuit board.

The electronic device according to the present invention is characterized in that the electromagnetic wave shielding wiring circuit board is connected.

According to the present invention, an electromagnetic wave shield sheet, an electromagnetic wave shielded wiring circuit board, and an electronic device which have good folding resistance and reduce transmission loss while having high electromagnetic wave shielding property even when used in a high frequency transmission circuit. It has the excellent effect of being able to provide equipment.

It is sectional drawing which illustrates the electromagnetic wave shield sheet which concerns on Embodiment 1. FIG. (A) is a diagram illustrating an SEM image of a cross section of the electromagnetic wave shield sheet according to the first embodiment, and (b) explains the peripheral length including the interface of the metal layer of the electromagnetic wave shield sheet according to the first embodiment. It is a figure, (c) is a figure explaining the peripheral length other than the interface in the metal layer of the electromagnetic wave shield sheet which concerns on Embodiment 1. (A) and (b) are diagrams exemplifying the interface of the metal layer according to the first embodiment, and (c) is a diagram exemplifying the case where the semicircular interfaces are arranged. It is a process sectional view which illustrates the manufacturing method of the electromagnetic wave shield sheet which concerns on Embodiment 1, and shows the 1st process. It is a process sectional view which illustrates the manufacturing method of the electromagnetic wave shield sheet which concerns on Embodiment 1, and shows the 2nd process. It is sectional drawing which illustrates the electromagnetic wave shielded wiring circuit board which concerns on Embodiment 2. It is a flowchart which illustrates the manufacturing method of the electromagnetic wave shielded wiring circuit board which concerns on Embodiment 2. It is sectional drawing which illustrates the electromagnetic wave shielded wiring circuit board which concerns on another example of Embodiment 2. It is a figure which illustrated each Example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated each Example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated each Example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated each comparative example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated each Example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated each Example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. It is a figure which illustrated the comparative example of the electromagnetic wave shielding property wiring circuit board using the electromagnetic wave shielding sheet which concerns on embodiment. (A) is a graph illustrating the correlation between the unfolded length ratio RLr on the adhesive layer 1 side according to the embodiment and the evaluation result, the horizontal axis represents the unfolded length ratio RLr, and the vertical axis represents. A four-level evaluation is shown. (B) is a graph exemplifying the correlation between the surface roughness Ra on the adhesive layer 1 side and the evaluation result, the horizontal axis shows the surface roughness Ra, and the vertical axis shows the four-step evaluation. (C) is a graph exemplifying the correlation between the surface roughness Rz on the adhesive layer 1 side and the evaluation result, the horizontal axis shows the surface roughness Rz, and the vertical axis shows the four-step evaluation.

Hereinafter, an example of an embodiment to which the present invention is applied will be described. The sizes and ratios of the members in the following figures are for convenience of explanation and are not limited thereto. Further, in the present specification, the description "arbitrary number A to arbitrary number B" includes the number A as the lower limit value and the number B as the upper limit value in the range. Further, the term "sheet" in the present specification includes not only "sheet" defined in JIS but also "film". In addition, the numerical value specified in the present specification is a value obtained by the method disclosed in the embodiment or the embodiment.

(Embodiment 1)
The electromagnetic wave shield sheet according to the first embodiment will be described. First, the outline of the electromagnetic wave shield sheet will be described. After that, each layer constituting the electromagnetic wave shield sheet will be described in detail, and then a method for manufacturing the electromagnetic wave shield sheet will be described.

<Overview of electromagnetic wave shield sheet>
FIG. 1 is a cross-sectional view illustrating the electromagnetic wave shield sheet 10 according to the first embodiment. As shown in FIG. 1, the electromagnetic wave shield sheet 10 includes an adhesive layer 1, a metal layer 2, and an insulating layer 3. The electromagnetic wave shield sheet 10 includes a laminate in which an adhesive layer 1, a metal layer 2, and an insulating layer 3 are laminated in this order. The metal layer 2 is arranged between the adhesive layer 1 and the insulating layer 3.

The electromagnetic wave shield sheet 10 is used, for example, by joining to a component (not shown) such as a wiring circuit board. When the electromagnetic wave shield sheet 10 is joined to the component, the adhesive layer 1 side of the electromagnetic wave shield sheet 10 is arranged on the component. Then, the electromagnetic wave shield sheet 10 is joined to the component by the bonding process between the electromagnetic wave shield sheet 10 and the component. As the joining treatment method, for example, heat treatment or thermocompression bonding treatment is preferable, but the joining treatment method is not particular as long as the electromagnetic wave shield sheet 10 and the parts can be joined.

The insulating layer 3 plays a role of protecting the electromagnetic wave shield sheet 10. The insulating layer 3 is arranged on the surface layer side of the metal layer 2. Specifically, when the electromagnetic wave shield sheet 10 is bonded to the component, the insulating layer 3 is arranged on the surface layer side of the metal layer 2. The metal layer 2 is a layer sandwiched between the insulating layer 3 and the adhesive layer 1. The metal layer 2 mainly plays a role of shielding electromagnetic waves.

When the component to which the electromagnetic wave shield sheet 10 is bonded is a wiring circuit board such as a printed wiring board, the electromagnetic wave shield sheet 10, particularly the metal layer 2, shields electromagnetic noise generated from signal wiring or the like inside the component. Further, the electromagnetic wave shielding sheet 10, particularly the metal layer 2, plays a role of shielding signals from the outside.

The film thickness of the metal layer 2 is 0.2 to 10 [μm]. The development length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 is 1 to 1.4. The development length ratio RLr of the interface on the insulating layer 3 side in the metal layer 2 is 1 to 1.5. As a result, the electromagnetic wave shield sheet 10 can achieve both good folding resistance and reduction of transmission loss. The unfolded length ratio RLr will be described later.

The electromagnetic wave shield sheet 10 may further include another layer. For example, the surface layer of the insulating layer 3 is insulated from other layers such as a film having scratch resistance, designability, printability, and flame retardancy, between the adhesive layer 1 and the metal layer 2, and from the metal layer 2. A film or the like for strengthening the magnetic field cut may be laminated between the layers 3.

The electromagnetic wave shield sheet 10 of the present embodiment is suitable for preventing radiated electromagnetic waves of parts that emit electromagnetic waves (electric field waves and magnetic field waves) and for preventing malfunctions due to an external magnetic field or radio waves. Examples of the parts include hard disks, cables, and printed wiring boards built in personal computers, mobile devices, digital cameras, and the like. It is also suitable for card readers and the like. Hereinafter, each layer constituting the electromagnetic wave shield sheet will be described.

<Metal layer: Expanded length ratio RLr>
The metal layer 2 plays a role of shielding electromagnetic waves and electric field waves. In the metal layer 2, the unfolded length ratio RLr on the adhesive layer 1 side is, for example, 1 to 1.4, and the unfolded length ratio RLr on the insulating layer 3 side is 1 to 1.5. The unfolded length ratio RLr can be obtained from the following mathematical formula (1).

[Number 1]
(Expanded length ratio RLr) = (Expanded length of metal layer interface) / (Linear distance of metal layer interface)
... (1)

Here, the developed length of the metal layer interface is obtained by subtracting the peripheral length other than the interface from the peripheral length including the interface of the metal layer 2 as shown in the following mathematical formula (2). Further, the linear distance of the metal layer interface can be obtained from the distance between both ends of the developed length.
[Number 2]
(Expanded length of metal layer interface) = (peripheral length including metal layer interface)-(peripheral length other than interface)
... (2)

FIG. 2A is a diagram illustrating an SEM image of a cross section of the electromagnetic wave shield sheet 10 according to the first embodiment. FIG. 2A also shows a diagram for explaining the developed length and the linear distance of the interface of the metal layer 2. As shown in FIG. 2A, the peripheral length including the interface of the metal layer 2 is obtained from an electron microscope image (about 10,000 times) obtained by observing the cross section of the electromagnetic wave shield sheet 10 from the vertical direction by SEM. Specifically, for example, it can be obtained by reading an electron microscope image and measuring the peripheral length of the interface of the metal layer 2. The magnification of the electron microscope image is not limited to 10,000 times. The peripheral length of the interface of the metal layer 2 is measured at a magnification at which the peripheral length does not change even if the magnification is slightly changed.

FIG. 2B is a diagram for explaining the peripheral length including the interface of the metal layer 2 of the electromagnetic wave shield sheet 10 according to the first embodiment, and FIG. 2C is a diagram for explaining the peripheral length including the interface of the metal layer 2 of the electromagnetic wave shield sheet 10 according to the first embodiment. It is a figure explaining the peripheral length other than the interface in 2. As shown in FIG. 2B, the peripheral length including the interface of the metal layer 4 can be measured due to the image analysis software. The peripheral length including the interface of the metal layer 4 is a peripheral length having a straight line and a curved line, and in the case of the metal layer 4, the peripheral length other than the interface and the developed length are included. The unfolded length is the length along the interface constituting the interface. As shown in FIG. 2C, the peripheral length other than the interface is composed of a straight line portion. Therefore, the unfolded length can be measured from the equation (2).

The developed length of the metal layer interface can be obtained, for example, by reading an electron microscope image using a predetermined analysis software and manually measuring the peripheral length including the interface of the metal layer 2. The predetermined analysis software is, for example, Mac-View Ver.4 (Mount Tech).

As shown in the mathematical formula (1), the degree of unevenness (degree of undulation) of the interface of the metal layer 2 can be grasped by the developed length ratio RLr. The truly smooth metal layer 2 has a straight cross-sectional shape and has a developed length ratio of RLr of 1. As the uneven shape of the surface of the metal layer 2 increases, the unfolded length ratio RLr also increases. The smaller the height difference of the unevenness and the smaller the number of the unevenness, the smaller the developed length ratio RLr. On the contrary, the larger the height difference of the unevenness and the larger the number of the unevenness, the larger the developed length ratio RLr. On the other hand, Ra and Rz, which are general indicators of surface shape, are hardly affected by the number of irregularities.

3A and 3B are diagrams illustrating the interface of the metal layer 2 according to the first embodiment, and FIG. 3C is a diagram illustrating the case where the semicircular interfaces are arranged side by side. When the shape of the interface shown in FIGS. 3A and 3B is defined by the surface roughness Ra1 and Ra2, both are substantially equal, and the surface roughness Ra1≈Ra2. However, when defined by the development length ratio RLr that indicates the ratio of the distance to the distance, RLr1 <RLr2, which is different from the cases of FIGS. 3A and 3B. By using the developed length ratio RLr, the state of the interface of the metal layer 2 can be clearly distinguished.

In the metal layer 2 of the electromagnetic wave shield sheet 10, due to the nature of the electric current, the electric current flows on the surface of the metal layer 2 at high frequencies. Then, the shape of the surface, that is, the interface, affects the current. Since components such as a wiring circuit board are arranged directly below the interface on the adhesive layer 1 side, the transmission characteristics are greatly affected. Therefore, it is preferable that the unfolded length ratio RLr on the adhesive layer 1 side is small.

For example, the unfolded length ratio RLr on the adhesive layer 1 side is preferably 1.12 or less, more preferably 1.04 or less. When the developed length ratio RLr is 1.5 or less, the smoothness of the metal layer 2 having a function as a conductor becomes high. As a result, in the wiring circuit board using the electromagnetic wave shield sheet 10, the transmission loss in the high frequency region can be reduced. For example, it is possible to further suppress transmission loss in a wiring circuit board that transmits a high frequency (100 [MHz] to 50 [GHz]) signal. When the adhesion and chemical resistance are taken into consideration, the developed length ratio RLr is preferably 1.0005 or more.

On the other hand, the interface on the insulating layer 3 side does not affect the transmission characteristics as much as the interface on the adhesive layer 1 side. Therefore, the unfolded length ratio RLr of the interface on the adhesive layer 1 side is preferably smaller than the unfolded length ratio RLr of the interface on the insulating layer 3 side. However, from the viewpoint of the adhesion between the adhesive layer 1, the metal layer 2 and the insulating layer 3 in the electromagnetic wave shielding sheet 10, it is preferable that the developed length ratio RLr of the interface on the insulating layer 3 side is large. However, if it becomes too large, stress will be applied when it is bent and it will be easy to break. Therefore, the development length ratio RLr of the interface on the insulating layer 3 side of the metal layer 2 is preferably 1 to 1.5.

As shown in FIG. 3C, when the semicircular interfaces are arranged, the circumference is π times the diameter, so that the unfolded length ratio RLr is larger than 1.5. If the unfolded length of the metal layer 2 on the adhesive layer 1 side is larger than 1.5 in this way, the transmission characteristics cannot be improved.

A method of observing the cross section of the electromagnetic wave shield sheet 10 used for measuring the unfolded length ratio RLr will be described. First, the electromagnetic wave shield sheet 10 is cut to expose the cross section. As a method for exposing the cross section, there are known methods such as a cutting method, a mechanical polishing method, a microtome method, and a FIB (focused ion beam) method. However, when different materials having different hardness are included, such as the electromagnetic wave shield sheet 10, structural deformation such as peeling of different interfaces and deformation of voids, so-called artifacts, occurs when the cross section is prepared. Therefore, a true cross-sectional structure may not be obtained. The CP (Cross Section Polisher) method is a method for preparing a cross section using a broad Ar (argon) ion beam, and prepares a smooth and strain-free sample cross section even for metals, semiconductors, ceramics, and their composite materials. Can be done. Therefore, in the present embodiment, the CP method is preferable as the method for cutting the metal layer 2.

<Metal layer: thickness>
The thickness of the metal layer 2 is preferably 0.2 to 5 [μm]. The thickness of the metal layer 2 is more preferably 0.2 to 4 [μm], and even more preferably 0.5 to 3 [μm]. When the thickness of the metal layer 2 is in the range of 0.2 to 5 [μm], it is possible to balance high electromagnetic wave shielding performance and folding resistance.

<Metal layer: Manufacturing method>
The method for producing the metal layer can be formed by vacuum deposition, sputtering, CVD method, MO (metal organic), plating, or the like, in addition to the method using metal foil. Among these, metal foil, vacuum vapor deposition or plating is preferable in consideration of mass productivity.

As a preferable example of the metal foil, aluminum, copper, silver, gold and the like can be exemplified. Copper, silver, and aluminum are more preferable, and copper is even more preferable, in terms of shielding properties and cost. As copper, for example, it is preferable to use rolled copper foil or electrolytic copper foil. The lower limit of the thickness of the metal foil is preferably 0.2 [μm] or more, and more preferably 0.5 [μm] or more. On the other hand, the upper limit of the thickness of the metal foil is preferably 10 [μm] or less, and more preferably 5 [μm] or less from the viewpoint of folding resistance.

Aluminum, copper, silver, and gold can be exemplified as suitable examples of the metal layer 2 obtained by vacuum deposition. Of these, copper and silver are more preferable. Further, as a preferable example of the metal layer obtained by sputtering, aluminum, copper, silver, chromium, gold, iron, palladium, nickel, platinum, silver, zinc, indium oxide and antimony-doped tin oxide can be exemplified. Of these, copper and silver are more preferable. The lower limit of the thickness of the metal layer obtained by vacuum deposition and sputtering is preferably 0.2 [μm] or more, and more preferably 0.5 [μm] or more. The upper limit is preferably 4 [μm] or less.

The surface of the obtained metal layer 2 is formed by laminating it on a carrier having a smooth surface to transfer the smooth surface, and forming a smooth surface mainly by removing the convex portion of the metal layer 2 by etching or mechanical polishing. A predetermined shape and a predetermined developed length ratio RLr can be obtained by a treatment step, a smooth surface forming treatment step mainly for filling fine recesses of the smooth metal layer 2 by plating, vapor deposition, or the like. .. Among these, mechanical polishing is preferable because the surface of the metal layer 2 can be precisely controlled in a predetermined shape and a predetermined development length ratio RLr. However, other methods are not limited to mechanical polishing as long as the shape of the surface of the metal layer 2 and the developed length ratio RLr can be controlled.

<Metal layer: opening>
The metal layer 2 of the present embodiment preferably has a plurality of openings 4 on the entire surface. The opening 4 penetrates from the interface on the adhesive layer 1 side to the interface on the insulating layer 3 side. The smaller the unfolded length ratio RLr of the metal layer 2, the more likely it is that the adhesive force when laminated is reduced. However, by having the opening 4, the resin contained in the adhesive layer 1 flows into the opening 4. As a result, the insulating layer 3 and the adhesive layer 1 are adhered to each other. Therefore, the adhesive force at the interface between the insulating layer 3 / the metal layer 2 and the metal layer 2 / the adhesive layer 1 is improved. Therefore, it is not necessary to perform a roughening treatment on the metal layer 2 in order to obtain good adhesion. Therefore, the surface of the metal layer 2 can be easily formed into a predetermined shape.

Further, by having the opening 4, when the solder reflow treatment is performed, the volatile components contained in the polyimide film of the printed wiring board and the coverlay adhesive are released to the outside, and the interface peeling of the coverlay adhesive and the electromagnetic wave shield sheet 10 is performed. It plays a role in suppressing poor appearance and deterioration of connection reliability due to.

The shape of the opening 4 viewed from the plane direction can be formed as needed, such as a circle, an ellipse, a square, a polygon, a star, or a trapezoid. From the viewpoint of manufacturing cost and film toughness, circles and ellipses are preferable. When measuring the unfolded length ratio RLr, the opening 4 is excluded.

Area per one opening 4 is preferably 0.7~5000 [μm ^2], and more preferably from 10 to 4000 [[mu] m ^2], more preferably 20~2000 [μm ^2]. By setting the area of the opening 4 to 0.7 [μm ² ] or more, the adhesion between the insulating layer 3 and the adhesive layer 1 becomes good, and the hygroscopicity becomes excellent. By setting the area of the opening 4 to 5000 [μm ² ] or less, the electromagnetic wave shielding property can be made excellent.

Number of the opening portion 4, preferably from 100 to 200,000 [pieces / cm ^2], and more preferably 1000-150000 [pieces / cm ^2]. By setting the number of openings 4 to 100 [pieces / cm ² ] or more, it is possible to efficiently release volatile components to the outside. Therefore, hygroscopicity can be improved. In addition, the repulsive force can be reduced. By reducing the number of openings 4 to 200,000 [pieces / cm ² ] or less, high electromagnetic wave shielding properties can be ensured.

<Metal layer: aperture ratio>
The aperture ratio of the metal layer 2 in the present embodiment is preferably 0.05 to 40 [%]. The aperture ratio can be adjusted from the area and number of openings 4. By setting the aperture ratio to 0.05 [%] or more, it is possible to efficiently release volatile components to the outside. Therefore, hygroscopicity can be improved. By setting the aperture ratio to 40 [%] or less, high electromagnetic wave shielding properties can be ensured. Moreover, the transmission loss can be reduced. The aperture ratio is calculated from the following formula (3).
[Number 3]
Aperture ratio [%] = (area of opening per unit area) / (area of opening per unit area + area of non-opening per unit area) x 100
... (3)

The lower limit of the aperture ratio is preferably 0.05 [%], more preferably 0.1 [%]. The upper limit of the aperture ratio is preferably 40 [%], more preferably 30 [%], and even more preferably 10 [%]. By setting the aperture ratio in the range of 0.1 to 30 [%], it is possible to maintain hygroscopicity, transmission loss after high humidity treatment, high electromagnetic wave shielding performance, and reduce repulsive force.

The aperture ratio is measured, for example, by binarizing the opening 4 and the non-opening using an image obtained by magnifying the metal layer 2 vertically from the plane direction with a laser microscope and a scanning electron microscope (SEM) at a magnification of 500 to 2000 times. It can be obtained by setting the number of pixels of the binarized color per unit area as each area.

<Metal layer: Method of forming openings>
The method of manufacturing the metal layer 2 having the opening 4 is, for example, a punching method of mechanically punching a metal foil, a method of piercing a needle-shaped protrusion on the entire surface to form an opening 4 in the metal foil, or a method of forming an opening 4 on the metal foil. A method of forming a pattern resist layer and etching a metal foil to form an opening 4, a method of printing a conductive paste on a predetermined pattern by screen printing, screen printing an anchor agent with a predetermined pattern, and only the anchor agent printing surface. The method of metal plating, the manufacturing method described in JP-A-2015-63730, and the like can be applied. That is, a water-soluble or solvent-soluble ink is pattern-printed on the support, and a metal vapor-deposited film is formed on the surface of the support to remove the pattern. A metal layer 2 having an opening 4 with a carrier can be obtained by forming a release layer on the surface and electroplating.

<Adhesive layer>
The adhesive layer 1 may contain, for example, a thermoplastic resin or a curable resin. The curable resin is preferably a thermosetting resin or a photocurable resin. Further, the adhesive layer 1 may contain a conductive adhesive.

The thermoplastic resins include polyolefin resins, vinyl resins, styrene / acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, polyester resins, polycarbonate resins, and polyimide resins. Examples include liquid crystal polymers and fluororesins. Although not particularly limited, a material having a low dielectric constant and a low dielectric loss tangent is preferable from the viewpoint of transmission loss, and a material having a low dielectric constant is preferable from the viewpoint of characteristic impedance, such as a liquid crystal polymer and a fluorine-containing resin.

The thermosetting resin contains functional groups that can be used for cross-linking reaction by heating, such as hydroxyl groups, phenolic hydroxyl groups, methoxymethyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups and thiols. Any resin having one or more groups, isocyanate groups, blocked isocyanate groups, blocked carboxyl groups, silanol groups, etc. in one molecule may be used, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane. Examples thereof include resins, epoxy resins, oxetane resins, phenoxy resins, polyimide resins, polyamide resins, phenolic resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins. Further, the thermosetting resin in the present embodiment contains, if necessary, a so-called "curing agent" such as a resin or a low molecular weight compound that reacts with the above functional groups to form a chemical crosslink in addition to the above resin. Is preferable.

The photocurable resin may be a resin having at least one unsaturated bond in one molecule that causes a cross-linking reaction by light. For example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, epoxy. Examples thereof include resins, oxetane resins, phenoxy resins, polyimide resins, polyamide resins, phenolic resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins.

The adhesive layer 1 has other optional components such as a silane coupling agent, a rust preventive, a reducing agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, a defoaming agent, and a leveling adjuster. Fillers, flame retardants, etc. can be blended.

<Adhesive layer: Conductive or insulating>
The adhesive layer 1 is located on one surface of the electromagnetic wave shield sheet 10 and is responsible for sticking to a wiring circuit board described later. The adhesive layer 1 is preferably an anisotropic conductive adhesive layer that exhibits conductivity only in the thickness direction, or is preferably an insulating adhesive. If an anisotropic conductive adhesive layer is used as the adhesive layer 1 and the anisotropic conductive adhesive layer and the metal layer 2 are in contact with each other, a special member can be formed between the ground circuit of the wiring circuit board and the metal layer 2. Can be electrically bonded without use. By using an anisotropic conductive adhesive layer as the adhesive layer 1, bonding can be achieved more efficiently and electrically.

The anisotropic conductive adhesive layer contains a resin and a conductive filler, and preferably contains 60 [mass%] or less of the conductive filler. On the other hand, from the viewpoint of suppressing an increase in the resistance value after aging, it is preferable to add more than 20 wt%, more preferably more than 39 wt%, and further preferably more than 45 wt%.

When the thickness of the adhesive layer 1 after pressing is used as a reference (100), the average particle size of the conductive filler is preferably about 100 to 1000. By containing 60 [mass%] or less of the conductive filler having such a size, it is possible to suppress an increase in the resistance value after aging.

The average particle size of the conductive filler is the average particle size of D95, and is preferably twice or more, more preferably three times or more, the thickness of the adhesive layer 1 after pressing from the viewpoint of suppressing an increase in resistance value after aging. It is more preferable to make it 4 times or more. On the other hand, from the viewpoint of poor appearance, 10 times or less is preferable, 8 times or less is more preferable, and 7 times or less is further preferable. The D95 average particle size can be determined by a laser diffraction / scattering method particle size distribution measuring device or the like.

Examples of the conductive filler used include metal powders such as gold, silver, copper and nickel, alloy powders, low melting point metal powders such as solder, silver-plated copper powders, metal-plated glass fibers and carbon fillers. Be done. Of these, silver powder having high conductivity, silver-plated copper powder, and low-melting-point metal powder such as solder are preferable.

The shape of the conductive filler includes a spherical shape, a flake shape, a dendritic shape, a fibrous shape, and the like, and a spherical shape and a dendritic shape in which anisotropic conductivity is easily obtained are particularly preferable. Further, two kinds of conductive fillers having different shapes may be mixed. The conductive filler can be used alone or in combination of two or more.

<Adhesive layer: Manufacturing method>
The adhesive layer 1 can be obtained by mixing and stirring the materials described above. For stirring, for example, a stirring device known for a dispermat, a homogenizer, or the like can be used.

A known method can be used for producing the adhesive layer 1. For example, a method of forming an adhesive layer by applying an adhesive resin composition on a peelable sheet and drying it, or using an extrusion molding machine such as a T-die to sheet the adhesive resin composition. It can also be formed by extruding into a shape.

The coating methods include, for example, gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, and dip coating method. A known coating method such as a method can be used. It is preferable to carry out a drying step at the time of coating. For the drying step, for example, a known drying device such as a hot air dryer or an infrared heater can be used.

<Adhesive layer: Thickness>
The thickness of the adhesive layer 1 can be appropriately designed according to the intended use, but is preferably in the range of 0.5 to 25 [μm], more preferably 2 to 10 [μm]. By setting the thickness of the adhesive layer 1 to 0.5 [μm] or more, the adhesive force to parts such as wiring circuit boards can be increased. Further, by setting it to 25 [μm], the flexibility of the electromagnetic wave shielding wiring circuit board is improved.

<Insulation layer>
The insulating layer 3 is an insulating sheet formed by molding an insulating resin composition, and plays a role of protecting the metal layer 2 and a role of ensuring the insulating property of the surface layer. As the insulating resin composition, it is preferable to use a thermoplastic resin or a thermosetting resin. The thermoplastic resin and the thermosetting resin are not particularly limited, but the thermoplastic resin or the curable resin described in the adhesive layer 1 can be used. The thermoplastic resin and the curable resin used for the insulating layer 3 and the adhesive layer 1 may be the same or different.

The insulating resin composition can be formed in the same manner as the adhesive resin composition.

Further, as the insulating layer 3, a film formed of an insulating resin such as polyester, polycarbonate, polyimide, or polyphenylene sulfide can also be used.

<Insulation layer: thickness>
The thickness of the insulating layer 3 may vary depending on the application, but is preferably 2 to 15 [μm]. With such a thickness, it is possible to easily balance various physical properties of the electromagnetic wave shield sheet 10.

<Manufacturing method of electromagnetic wave shield sheet>
The method for manufacturing the electromagnetic wave shield sheet 10 is not particularly limited, but as an example, a method of bonding the adhesive layer 1, the metal layer 2, and the insulating layer 3 manufactured by the above method can be exemplified.

4 and 5 are process cross-sectional views illustrating the method for manufacturing the electromagnetic wave shield sheet 10 according to the first embodiment, FIG. 4 shows a first step, and FIG. 5 shows a second step. As shown in FIG. 4, the insulating layer 3 is applied to the base material 5. As the insulating layer 3, a preformed insulating film may be used, or the insulating layer 3 may be formed by applying an insulating resin composition to a base material 5 such as a peelable sheet. Next, the metal layer 2 with the carrier 6 is prepared. The metal layer 2 is, for example, a copper foil. The unevenness of the surface of the metal layer 2 is processed to a predetermined parameter. For example, the metal layer 2 is processed so that the developed length ratio RLr on the surface is 1 to 1.5.

Next, the metal layer 2 side of the metal layer 2 with the carrier 6 is attached to the insulating layer 3 coated on the base material 5. Then, the carrier 6 is peeled off from the laminated body of the base material 5, the insulating layer 3, and the metal layer 2. The insulating layer 3 may be formed by directly coating the insulating resin composition on the metal layer 2.

Next, the unevenness of the surface of the metal layer 2 on which the carrier 6 has been peeled off is processed to a predetermined parameter. For example, the unfolded length ratio RLr on the other surface of the metal layer 2 is processed to be 1 to 1.4. A carrier 6 having a smooth surface may be used, and the metal layer 2 may be laminated on the carrier 6 to transfer the smooth surface having a predetermined development length ratio RLr to the metal layer 2.

Next, as shown in FIG. 5, the adhesive layer 1 is applied to the base material 7. Next, the metal layer 2 side of the laminate of the base material 5, the insulating layer 3 and the metal layer 2 is attached to the adhesive layer 1 coated on the base material 7. In this way, the electromagnetic wave shield sheet 10 in which the interface of the metal layer 2 has a predetermined development length ratio RLr can be manufactured. When the electromagnetic wave shield sheet 10 is used for a component such as a wiring circuit board, the base material 7 is peeled off from the laminate of the insulating layer 3, the metal layer 2, and the adhesive layer 1 to be a shield target for the wiring circuit board or the like. The adhesive layer 1 side is adhered to the component. After adhesion, the base material 5 is peeled off. In this way, the electromagnetic wave shield sheet 10 can be used for the wiring circuit board.

The electromagnetic wave shield sheet 10 manufactured as described above can be used by being attached to various wiring circuit boards such as a flexible printed wiring board. Further, the electromagnetic wave shield sheet 10 according to the present embodiment can be widely applied to various electronic devices, devices, appliances and the like in addition to the wiring circuit board.

Next, the effect of this embodiment will be described. The electromagnetic wave shield sheet 10 of the present embodiment includes a metal layer 2. By setting the film thickness of the metal layer 2 to 0.2 to 10 μm, it is possible to have good folding resistance while having high electromagnetic wave shielding properties.

Further, the developed length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 affects the current flowing through the interface. Then, by setting the developed length ratio RLr of the interface on the adhesive layer 1 side to 1 to 1.4, it is possible to improve the transmission characteristics of the wiring circuit board arranged immediately below the interface on the adhesive layer 1 side. it can.

Further, the developed length ratio RLr of the interface on the insulating layer 3 side of the metal layer 2 affects the adhesion and folding resistance between the metal layer 2 and the insulating layer 3. For example, when the developed length ratio RLr of the interface on the insulating layer 3 side is large, the adhesion is improved, and when it is small, the folding resistance is improved. By setting the developed length ratio RLr of the interface on the insulating layer 3 side to 1 to 1.5, it is possible to balance the adhesiveness and the folding resistance.

(Embodiment 2)
Next, the electromagnetic wave shielded wiring circuit board according to the second embodiment will be described. The electromagnetic wave shielded wiring circuit board of the present embodiment is one in which the electromagnetic wave shield sheet 10 is bonded on at least one surface of the wiring circuit board. The electromagnetic wave shielded wiring circuit board of this embodiment is suitably used for, for example, an electronic device that transmits a signal having a frequency in the range of 1 [MHz] to 20 [GHz], for example, an electronic device such as a digital camera or a mobile phone. it can.

FIG. 6 is a cross-sectional view illustrating the electromagnetic wave shielded wiring circuit board 110 according to the second embodiment. As shown in FIG. 6, the electromagnetic wave shielding property wiring circuit board 110 includes a wiring circuit board 100, an electromagnetic wave shielding sheet 10, a cover layer 301, and a cover layer 302. The electromagnetic wave shielding wiring circuit board 110 has flexibility because it includes a film-like member, a thin member, a flexible member, and the like. The electromagnetic wave shielding wiring circuit board 110 extends in one direction in a flat state.

Here, for convenience of explanation of the electromagnetic wave shielded wiring circuit board 110, an XYZ Cartesian coordinate system is introduced. With the electromagnetic wave shielding wiring circuit board 110 flattened, the direction in which the electromagnetic wave shielding wiring circuit board 110 extends is defined as the X-axis direction. The direction orthogonal to the upper surface of the electromagnetic wave shielding wiring circuit board 110 is defined as the Z-axis direction. Therefore, the thickness direction of the electromagnetic wave shielding wiring circuit board 110 is the Z-axis direction. Both end faces of the electromagnetic wave shielding wiring circuit board 110 face in the Y-axis direction.

The wiring circuit board 100 extends in one direction, that is, in the X-axis direction. The wiring circuit board 100 is, for example, a flexible wiring board. The wiring circuit board 100 includes a conductive layer 11, a conductive layer 12, an insulating layer 21, an insulating layer 22, an insulating layer 23, a signal circuit 30, and a ground circuit 40. The wiring circuit board 100 is laminated in the order of the conductive layer 11, the insulating layer 21, the insulating layer 22, the insulating layer 23, and the conductive layer 12 from the bottom. A signal circuit 30 and a ground circuit 40 are provided between the insulating layer 21 and the insulating layer 22. In the wiring circuit board 100, another conductive layer or an insulating layer may be inserted between the layers. Both end faces face each other in the other direction orthogonal to one direction in the plane parallel to the upper surface 102 of the wiring circuit board 100, that is, in the Y-axis direction.

The conductive layer 11 is formed, for example, over the lower surface 101 of the wiring circuit board 100. The insulating layer 21 is provided on the conductive layer 11. The signal circuit 30 is provided on the insulating layer 21. The signal circuit 30 has a portion extending in the X-axis direction on the insulating layer 21. A plurality of signal circuits 30 may be provided. The signal circuit 30 may include, for example, a signal circuit 31 and a signal circuit 32. For example, the signal circuit 31 is arranged on the −Y axis direction side of the signal circuit 32.

The ground circuit 40 is provided on the insulating layer 21. The ground circuit 40 has a portion extending in the X-axis direction on the insulating layer 21. The ground circuit 40 is provided at a distance from the signal circuit 30. The ground circuit 40 has a portion extending in the X-axis direction along the signal circuit 30. A plurality of ground circuits 40 may be provided. The ground circuit 40 may include, for example, a ground circuit 41 and a ground circuit 42. For example, the ground circuit 41 is arranged on the −Y axis direction side of the signal circuit 31. The ground circuit 42 is arranged on the + Y-axis direction side of the signal circuit 32. The ground circuit 41 and the ground circuit 42 are provided so as to sandwich the signal circuits 31 and 32 from both the + Y axis direction side and the −Y axis direction side. Therefore, the signal circuit 30 is arranged between the ground circuit 41 and the ground circuit 42.

The insulating layer 22 is provided on the insulating layer 21, the signal circuit 30, and the ground circuit 40. The insulating layer 22 is provided on the insulating layer 21 so as to cover the signal circuit 30 and the ground circuit 40 from above. The insulating layer 23 is provided on the insulating layer 22. The conductive layer 12 is provided on the insulating layer 23.

The wiring circuit board 100 may be formed by using, for example, a double-sided flexible copper-clad laminate (hereinafter referred to as double-sided FCCL) and a single-sided flexible copper-clad laminate (hereinafter referred to as single-sided FCCL). The double-sided FCCL has copper foils formed on both sides of a film-like insulating base material layer. The single-sided FCCL has a copper foil formed on one side of a film-like insulating base material layer.

The copper foil on one side of the double-sided FCCL is used as the conductive layer 11, and the insulating base material layer is used as the insulating layer 21. The copper foil on the other side is patterned and used as the signal circuit 30 and the ground circuit 40. Further, the copper foil on one side of the one-sided FCCL is used as the conductive layer 12, and the insulating base material layer is used as the insulating layer 23. When double-sided FCCL and single-sided FCCL are used, the wiring circuit board 100 is formed as follows. That is, the signal circuit 30 and the ground circuit 40 are formed by patterning the other surface of the double-sided FCCL. Next, the insulating base material layer side of the single-sided FCCL is adhered to the patterned surface of the double-sided FCCL. As a result, the wiring circuit board 100 is formed. The insulating adhesive used for bonding is the insulating layer 22.

The insulating base layer of the double-sided and single-sided FCCL is preferably polyester, polycarbonate, polyimide, polyphenylene sulfide, or liquid crystal polymer, and more preferably liquid crystal polymer or polyimide. Among these, a liquid crystal polymer having a low relative permittivity and a low dielectric loss tangent is more preferable in consideration of the use of a flexible printed wiring board for transmitting a high frequency signal. By providing an insulating base material such as these, the electromagnetic wave shielding wiring circuit board 110 can obtain high heat resistance.

The signal circuit 30 sends an electric signal to an electronic member connected via the electromagnetic wave shielding wiring circuit board 110. The ground circuit 40 is set to a ground potential for grounding. The material used for the conductive layer 11, the conductive layer 12, the signal circuit 30, and the ground circuit 40 is not limited to copper foil as long as it is conductive. Further, the wiring circuit board 100 is not limited to the one formed by using the double-sided FCCL and the single-sided FCCL. For example, the conductive layer 11, the insulating layer 21, the signal circuit 30, the ground circuit 40, the insulating layer 22, the insulating layer 23, and the conductive layer 12 may be laminated in this order.

The thickness of the conductive layer 11, the conductive layer 12, the signal circuit 30, and the ground circuit 40 is, for example, 18 [μm]. The thickness of the insulating layer 21 and the insulating layer 23 is, for example, 50 [μm]. The thickness of the insulating layer 22 is, for example, 35 [μm]. The thickness of each layer included in the wiring circuit board 100 is not limited to the above-mentioned thickness as long as the wiring circuit board 100 is flexible, and may be about 1 to 200 [μm].

The insulating cover layer 301 is provided below the wiring circuit board 100. The insulating cover layer 302 is provided above the wiring circuit board 100. The cover layers 301 and 302 are insulating materials that cover the wiring circuit board 100 and protect it from the external environment. Since the conductive layers 11 and 12 are exposed over the lower surface 101 and the upper surface 102 of the wiring circuit board 100, the cover layers 301 and 302 cover the conductive layers 11 and 12. The cover layers 301 and 302 include, for example, a coverlay 61 and an insulating adhesive layer 62. The coverlay 61 contains, for example, a resin such as polyimide as a material. The insulating adhesive layer 62 is, for example, an insulating adhesive. The cover layers 301 and 302 are not limited to the configuration including the coverlay 61 and the insulating adhesive layer 62, and may be a thermosetting type or ultraviolet curable type solder resist, a photosensitive coverlay film suitable for fine processing, or the like. , Thermosetting adhesive or the like may be used. The thickness of the cover layers 301 and 302 is, for example, 10 to 100 [μm], preferably 60 [μm]. The thickness of the coverlay 61 is, for example, 25 [μm], and the thickness of the insulating adhesive layer 62 is, for example, 35 [μm].

In the cover layers 301 and 302, the insulating adhesive layer 62 side is adhered to the wiring circuit board 100. Through holes 63 are formed in the cover layers 301 and 302. The through hole 63 penetrates the coverlay 61 and the insulating adhesive layer 62. An earth via 64 is formed inside the through hole 63. Therefore, the earth via 64 penetrates the cover layers 301 and 302.

The electromagnetic wave shield sheets 10a and 10b include an adhesive layer 1, a metal layer 2, and an insulating layer 3 as described above. The electromagnetic wave shield sheets 10a and 10b are collectively referred to as an electromagnetic wave shield sheet 10. Therefore, the electromagnetic wave shield sheet 10 includes an electromagnetic wave shield sheet 10a that covers the lower surface 101 of the wiring circuit board 100, and an electromagnetic wave shield sheet 10b that covers the upper surface 102. The electromagnetic wave shield sheet 10 shields the wiring circuit board 100.

The electromagnetic wave shield sheet 10a covers the lower surface 101 of the wiring circuit board 100 with the adhesive layer 1 side. Therefore, the surface on the adhesive layer 1 side faces the lower surface 101 on the wiring circuit board 100 side. The electromagnetic wave shield sheet 10a covers the wiring circuit board 100 and is in contact with the cover layer 301. Therefore, the cover layer 301 is provided between the lower surface 101 of the wiring circuit board 100 and the electromagnetic wave shield sheet 10a that covers the lower surface 101. The electromagnetic wave shield sheet 10a covers the lower surface 101 of the wiring circuit board 100 with the adhesive layer 1 side, and covers at least a part of both end faces of the wiring circuit board 100 in the Y-axis direction with the adhesive layer 1 side. For example, the electromagnetic wave shield sheet 10a covers both end faces of the conductive layer 11, the insulating layer 21, and the insulating layer 22 of the wiring circuit board 100. Therefore, the electromagnetic wave shield sheet 10a comes into contact with both end faces of the conductive layer 11. Further, the electromagnetic wave shield sheet 10a covers both end faces of the cover layer 301.

The electromagnetic wave shield sheet 10b covers the upper surface 102 of the wiring circuit board 100 with the adhesive layer 1 side. Therefore, the surface on the adhesive layer 1 side faces the upper surface 102 on the wiring circuit board 100 side. The electromagnetic wave shield sheet 10b covers the wiring circuit board 100 and is in contact with the cover layer 302. Therefore, the cover layer 302 is provided between the upper surface 102 of the wiring circuit board 100 and the electromagnetic wave shield sheet 10b that covers the upper surface 102. The electromagnetic wave shield sheet 10b covers the upper surface 102 of the wiring circuit board 100 with the adhesive layer 1 side, and covers at least a part of both end faces of the wiring circuit board 100 in the Y-axis direction with the adhesive layer 1 side. For example, the electromagnetic wave shield sheet 10b covers both end faces of the conductive layer 12, the insulating layer 23, and the insulating layer 22 of the wiring circuit board 100. Therefore, the electromagnetic wave shield sheet 10b comes into contact with both end faces of the conductive layer 12. Further, the electromagnetic wave shield sheet 10b covers both end faces of the cover layer 302.

Both end faces of the wiring circuit board 100, that is, the end faces 103 and 104 are covered with the adhesive layer 1 from the conductive layer 11 to the conductive layer 12. Both end faces of the wiring circuit board 100 are covered with the adhesive layer 1 of the electromagnetic wave shield sheet 10a and the electromagnetic wave shield sheet 10b over the entire surface.

The boundary where the electromagnetic wave shield sheets 10a and 10b cover both end faces of the wiring circuit board 100 in the Y-axis direction is not limited to both end faces of the insulating layer 22. For example, the electromagnetic wave shield sheet 10a covers both ends of the cover layer 301 and the conductive layer 11, and the electromagnetic wave shield sheet 10b covers both ends of the cover layer 302, the conductive layer 12, the insulating layer 23, the insulating layer 22, and the insulating layer 21. The boundary between both end faces of the electromagnetic wave shield sheets 10a and 10b may be anywhere on both end faces, such as covering the faces.

The adhesive layers 1 of the electromagnetic wave shield sheets 10a and 10b may cover both end faces so as to extend in the X-axis direction along the signal circuit 30. Further, the adhesive layer 1 may cover the entire surface of both end surfaces along the signal circuit 30. The adhesive layer 1 of the electromagnetic wave shield sheets 10a and 10b may have a portion extending from both end faces of the wiring circuit board 100 in the outer Y-axis direction. The adhesive layer 1 may have a portion extending in the −Y axis direction from the end surface 103 on the −Y axis direction side and a portion extending in the + Y axis direction from the end surface 104 on the + Y axis direction side.

The earth via 64 penetrating the cover layers 301 and 302 contains the same material as the adhesive layer 1. When the adhesive layer 1 contains a conductive material, a part of the adhesive layer 1 is filled inside the through hole 63, so that the earth via 64 is the conductive material contained in the adhesive layer 1. May contain the same material as. The adhesive layer 1 is connected to the conductive layer 11 and the conductive layer 12 via the earth via 64. The earth via 64 penetrating the cover layers 301 and 302 may be arranged directly above the ground circuit 40.

Next, a method of manufacturing the electromagnetic wave shielding wiring circuit board 110 according to the second embodiment will be described. FIG. 7 is a flowchart illustrating a method of manufacturing the electromagnetic wave shielded wiring circuit board 110 according to the second embodiment.

As shown in step S11 of FIG. 7, first, the wiring circuit board 100 is prepared. The wiring circuit board 100 includes a conductive layer 11, an insulating layer 21 provided on the conductive layer 11, a signal circuit 30 provided on the insulating layer 21 and having a portion extending in the X-axis direction, an insulating layer 21 and the insulating layer 21. The insulating layers 22 and 23 provided on the signal circuit 30 and the conductive layer 12 provided on the insulating layer 23 are included.

Next, as shown in step S12, the electromagnetic wave shield sheet 10 is prepared. The order of steps S11 and S12 may be reversed or may be simultaneous.

Next, as shown in step S13, the wiring circuit board 100 is covered with the electromagnetic wave shield sheet 10. Specifically, the lower surface 101 of the wiring circuit board 100 is covered with the adhesive layer 1 side of the electromagnetic wave shield sheet 10a via the insulating cover layer 301, and the upper surface 102 of the wiring circuit board 100 is covered with the insulating cover. It is covered with the adhesive layer 1 side of the electromagnetic wave shielding sheet 10b via the layer 302. At the same time, at least a part of both end faces of the wiring circuit board 100 in the Y-axis direction is covered with the adhesive layer 1 side of the electromagnetic wave shield sheets 10a and 10b. The cover layer 302 is provided with a through hole 63. Further, it is desirable that the cover layer 301 is also provided with the through hole 63.

Next, as shown in step S14, pressing is performed. For example, heat is applied and heat pressed. Specifically, the electromagnetic wave shield sheets 10a and 10b covering the wiring circuit board 100 and the wiring circuit board 100 are pressed in the vertical direction. For example, the heat press preferably has a temperature of about 150 to 190 [° C.], a pressure of about 1 to 3 [MPa], and a time of about 1 to 60 [min]. As a result, the wiring circuit board 100, the cover layers 301 and 302, and the electromagnetic wave shield sheets 10a and 10b are crimped. At this time, the through hole 63 is filled with a part of the adhesive layer 1. When the pressing time is less than 30 minutes, it is preferable to perform oven curing at about 150 to 190 ° C. for 30 minutes or more after hot pressing. In this way, the electromagnetic wave shielded wiring circuit board 110 can be manufactured.

<Another Embodiment>
Next, another example of the electromagnetic wave shielded wiring circuit board will be described. FIG. 8 is a cross-sectional view illustrating the electromagnetic wave shielded wiring circuit board 210 according to another example of the second embodiment. As shown in FIG. 8, the electromagnetic wave shielding property wiring circuit board 210 includes a wiring circuit board 200, an electromagnetic wave shielding sheet 10, a cover layer 301, and a cover layer 302. The electromagnetic wave shielded wiring circuit board 210 is different from the above-mentioned electromagnetic wave shielded wiring circuit board 110 in that the configuration of the wiring circuit board 200 and the electromagnetic wave shield sheet 10 cover one side. The electromagnetic wave shielded wiring circuit board 210 also has flexibility.

The wiring circuit board 200 includes a conductive layer 11, an insulating layer 21, and wiring 50. The conductive layer 11 is formed, for example, over the lower surface 101 of the wiring circuit board 100. The insulating layer 21 is provided on the conductive layer 11. The wiring 50 is provided on the insulating layer 21. The wiring 50 has a portion extending in the X-axis direction on the insulating layer 21. A plurality of wirings 50 may be provided. The plurality of wires 50 and 51 are arranged at intervals in the Y-axis direction.

The wiring circuit board 200 is formed by using, for example, double-sided FCCL. The double-sided FCCL has copper foils formed on both sides of a film-like insulating base material layer. The copper foil on one side of the double-sided FCCL is used as the conductive layer 11, and the insulating base material layer is used as the insulating layer 21. The copper foil on the other side is patterned and used as the wiring 50 which becomes the signal circuit 30 and the ground circuit 40.

The insulating cover layer 301 is provided below the wiring circuit board 200. The insulating cover layer 302 is provided above the wiring circuit board 200. The cover layers 301 and 302 are insulating materials that cover the wiring circuit board 200 and protect it from the external environment. The cover layer 301 covers the conductive layer 11 of the wiring circuit board 200 from below. The cover layer 302 covers the wiring 50 from above.

As described above, the electromagnetic wave shield sheet 10 includes the adhesive layer 1, the metal layer 2, and the insulating layer 3. The electromagnetic wave shield sheet 10 covers, for example, the upper surface 201 side of the wiring circuit board 200. The electromagnetic wave shield sheet 10 covers the wiring circuit board 200 and is in contact with the cover layer 302. Therefore, the cover layer 302 is provided between the upper surface 201 of the wiring circuit board 200 and the electromagnetic wave shield sheet 10 that covers the upper surface 201.

<Examples and Comparative Examples>
Next, Examples and Comparative Examples will be described.

(Film thickness of adhesive layer)
The film thickness of the adhesive layer 1 is the thickness of the adhesive layer 1 after the electromagnetic wave shield sheet 10 is heat-bonded to the parts, and was measured by the following method. First, the peelable sheet of the adhesive layer 1 of the electromagnetic wave shield sheet 10 is peeled off, and the exposed adhesive layer and the polyimide film (“Kapton 200EN” manufactured by Toray DuPont) are bonded together for 30 minutes at 2 MPa and 150 ° C. Heat crimped. After cutting this into a size of about 5 mm in width and 5 mm in length, 0.05 g of epoxy resin (Petropoxy 154, manufactured by Maruto) is dropped on a slide glass, and an electromagnetic wave shield sheet 10 is adhered to the slide glass / electromagnetic wave. A laminate having the structure of the shield sheet 10 / polyimide film was obtained. The obtained laminate was cut by ion beam irradiation from the polyimide film side using a cross section polisher (SM-09010 manufactured by JEOL Ltd.) to obtain a measurement sample of the electromagnetic wave shield sheet 10 after heat crimping.

The cross section of the obtained measurement sample was measured with a laser microscope (VK-X100 manufactured by KEYENCE CORPORATION), and the thickness of the adhesive layer was measured from the observed enlarged image. The magnification was 500 to 2000 times.

(Transmission characteristics)
The transmission characteristics were evaluated using a flexible printed wiring board having a coplanar structure in which electromagnetic wave shield sheets were laminated on both sides. The flexible printed wiring board with a copper structure has a coverlay "CISV1215 (manufactured by Nikkan Kogyo Co., Ltd.)" composed of a polyimide film (thickness 12.5 μm) and an insulating adhesive layer (thickness 15 μm), and a thickness of 25 μm. It is composed of a double-sided CCL in which a rolled copper foil having a thickness of 12 μm is laminated on both sides of the polyimide film of. Then, two signal wirings having a length of 10 cm and a ground wiring are formed on one copper foil surface of the double-sided CCL, and the copper foil on the other surface is a shield film at a place where it does not overlap with the signal wiring. A part to be electrically connected to the ground wiring was formed, and the other part was removed by etching.
In Examples 1 to 15 and Comparative Examples 1 to 5, the width of the ground wiring was 80 μm, the width of the ground wiring was 1 mm, and the distance between the ground wiring and the signal wiring was 1 mm.

Two electromagnetic wave shield sheets are prepared, and the adhesive layer exposed by peeling off the peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet is applied to the coverlay side of the flexible printed wiring board of the coplanar structure and the etching surface of the double-sided CCL. On the other hand, it was pressure-bonded at 150 ° C. for 30 minutes at 2.0 MPa and heat-cured to obtain a laminate.
The transmission characteristics were evaluated by measuring the transmission loss of a high frequency signal of 20 GHz.
The evaluation criteria are as follows.
Excellent (◎): Less than 14 dB Good (Good, △): 14 dB or more, less than 15 dB Unsuitable (Poor, ×): 15 dB or more

(Heat-resistant)
The heat resistance was evaluated from the influence on the heat of the electromagnetic wave shielding wiring circuit board 210. The heat resistance is evaluated by the presence or absence of a change in appearance after the laminate coated with the electromagnetic wave shield sheet is reflowed using a small reflow machine (manufactured by SOLSYS-62501RTP Antom) at a peak temperature of 260 ° C. did. The appearance of the electromagnetic wave shield sheet having high heat resistance does not change, but the electromagnetic wave shield sheet having low heat resistance causes foaming and peeling.

First, the electromagnetic wave shield sheet was prepared to have a width of 15 mm and a length of 120 mm. Separately, as an adherend to which the electromagnetic wave shield sheet is attached, a polyimide film (thickness 12.5 μm “Kapton 50EN” manufactured by Toray DuPont) and a double-sided two-layer CCL in which copper foil (thickness 12 μm) is laminated on both sides thereof. Originally, a coverlay "CISV1225 (Nikkan Kogyo Co., Ltd.)" composed of a polyimide film with a thickness of 12.5 μm and a thermosetting adhesive with a thickness of 25 μm is formed on one of the copper foils in a shape based on JIS C6471. ”Was formed on both sides to form a double-sided printed wiring board. Further, the adhesive layer exposed by peeling the peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet is placed at 150 ° C. for 30 minutes at 2.0 MPa with respect to the coverlay on the side where the wiring of the double-sided printed wiring board is formed. It was crimped with and heat-cured to obtain a laminate. The obtained laminate was left at 40 ° C. and 90% RH for 72 hours. After that, a reflow treatment was performed, the appearance was visually observed, and the presence or absence of abnormalities such as foaming, floating, and peeling was evaluated according to the following criteria.
Excellent (◎): Excellent.
Good (△): Good.
Inappropriate (Poor, ×): Inappropriate.

(Chemical resistance)
The peelable sheet of the adhesive layer of the electromagnetic wave shield sheet having a width of 40 mm and a length of 40 mm is peeled off, and the exposed adhesive layer and Kapton 500H having a width of 50 mm and a length of 50 mm are crimped under the conditions of 150 ° C., 2.0 MPa and 30 minutes. The laminate was obtained by thermosetting. On the insulating layer side of the electromagnetic wave shield sheet of the obtained laminate, a cross-cut guide was used according to JIS K5400, and 100 grids with an interval of 1 mm were prepared. After that, it is immersed in the solvent-based cleaning liquid "Zestron FA +" (manufactured by Zestron) for 20 minutes, and the output is set to 100% using the ultrasonic cleaner "UT-205HS" (manufactured by SHARP), and the ultrasonic treatment is performed for 2 minutes. After that, the sample was taken out, washed with distilled water, and then dried. The adhesive tape was strongly pressure-bonded to the grid portion, and the end of the tape was peeled off at a stretch at an angle of 45 °, and the state of the grid was judged according to the following criteria.
⊚: The eyes of any grid do not come off.
〇: Small peeling of the coating film at the intersection of cuts. Clearly not above 5%.
Δ: The coating film is partially or completely peeled off along the cut line. 15% or more and less than 35%. X: The coating film is partially or completely peeled off along the cut line. 35% or more.

(Fold resistance)
The peelable sheet of the adhesive layer of the electromagnetic wave shield sheet having a width of 20 mm and a length of 100 mm is peeled off, and the exposed adhesive layer and Kapton 500H having a width of 20 mm and a length of 100 mm are crimped under the conditions of 150 ° C., 2.0 MPa and 30 minutes. The laminate was obtained by thermosetting. The electromagnetic wave shield sheet of the obtained laminated body is bent 180 degrees so that it is on the outside, a weight of 1000 g is placed on the bent portion for 10 seconds, the bent portion is returned to the original flat state, and the weight of 1000 g is put back again. It was placed for 10 seconds, and the number of times of bending was set to 1. Whether or not cracks were generated in the electromagnetic wave shield sheet was observed with a KEYENCE microscope "VHX-900", and the number of times the electromagnetic wave was bent without cracks was evaluated.
The number of times of bending until a crack was generated in the bent portion to which a load of 1000 g was applied was counted. The evaluation criteria are as follows.
⊚: 10 times or more. Very good.
◯: 7 times or more and less than 10 times. Good Δ: 2 times or more, less than 7 times.
X: Less than 2 times. Not practical.

(Resistance value after aging)
The peelable sheet of the adhesive layer 1 of the electromagnetic wave shield sheet 10 having a width of 20 mm and a length of 50 mm was peeled off, and the exposed adhesive layer 1 was separately prepared as a polyimide film of a flexible printed wiring board (thickness 12.5 μm). 1 Laminate on top. The flexible printed wiring board is formed of an electrically unconnected wiring 50 and a wiring 51 made of copper foil having a thickness of 18 μm, and has a through hole having an area of 20 mm ² or less on the circuit 50. A polyimide cover film with a 5 μm adhesive is laminated. Both were pressure-bonded for 30 minutes at 150 ° C. and 2 MPa to prepare a measurement sample. The resistance value between the circuit 50 and the circuit 51 of this measurement sample was measured using a 4-probe probe of "Lorester GP" manufactured by Mitsubishi Chemical Corporation, and the initial value was evaluated according to the following criteria. The value in parentheses is the cross-sectional area of the through hole.

After the evaluation of the initial value is completed, the measurement sample is allowed to stand for 500 hours in an atmosphere of 85 ° C. and 85% relative humidity, and then the resistance value between the circuit 50 and the circuit 51 is set to that of Mitsubishi Chemical's "Lorester GP". 4 Measured using a probe probe, the resistance value after aging was used, and the evaluation was made according to the following criteria.
⊚: (resistance value after 500H) / (initial value) ≦ 2
◯: 2 <(resistance value after 500H) / (initial value) ≤ 5
Δ: 5 <(resistance value after 500H) / (initial value) ≦ 10
X: (resistance value after 500H) / (initial value)> 10

9 to 15 are diagrams illustrating each embodiment and each comparative example of the electromagnetic wave shielded wiring circuit boards 110 and 210 using the electromagnetic wave shield sheet 10 according to the embodiment. 13 to 15 also include those showing Examples 11 to 15 and Comparative Example 5 in FIGS. 9 to 12 from another viewpoint. As shown in FIGS. 9 to 15, the unfolded length ratio RLr of the metal layer 2 on the adhesive layer 1 side is 1 to 1.4, and the unfolded length ratio RLr of the metal layer 2 on the insulating layer 3 side. When is 1 to 1.5, the transmission characteristics are excellent. On the other hand, when the unfolded length ratio RLr on the adhesive layer 1 side is 1.6 or more, the transmission characteristics and the folding resistance are unsuitable. Further, when the unfolded length ratio RLr on the insulating layer 3 side of the metal layer 2 exceeds 1.5, the folding resistance is unsuitable. The copper foil used in the metal layers 2 of Comparative Examples 3 to 5 is an electrolytic copper foil (“MT18SD-H” (manufactured by Mitsui Mining & Smelting Co., Ltd.)).

As shown in Examples 1, 2, 4, 5, 7, 11 to 15, the unfolded length ratio RLr on the adhesive layer 1 side is 1.001 to 1.11 and the unfolded on the insulating layer 3 side. When the length ratio RLr is 1.03 to 1.28, the transmission characteristics, the chemical resistance, and the folding resistance are excellent.

Regarding the opening 4, the opening ratio is preferably 0.1 to 30 [%], and when the opening ratio is 0.2 to 16.0 [%], the transmission characteristics, chemical resistance, folding resistance, and heat resistance are excellent. There is.

FIG. 16A is a graph illustrating the correlation between the unfolded length ratio RLr on the adhesive layer 1 side and the evaluation result. The horizontal axis represents the unfolded length ratio RLr, and the vertical axis represents the transmission characteristic. The evaluation of is shown. (B) is a graph illustrating the correlation between the surface roughness Ra on the adhesive layer 1 side and the evaluation result, the horizontal axis represents the surface roughness Ra, and the vertical axis represents the evaluation of the transmission characteristics. .. (C) is a graph illustrating the correlation between the surface roughness Rz on the adhesive layer 1 side and the evaluation result, the horizontal axis represents the surface roughness Rz, and the vertical axis represents the evaluation of the transmission characteristics. .. In the surface roughness Ra and Rz of (b) and (c), those having surface roughness Ra and Rz smaller than 0.1 in Examples 4 to 7 and the like are shown by replacing with 0.05.

As shown in FIG. 16A, the unfolded length ratio RLr on the adhesive layer 1 side has a correlation with the evaluation result, and the smaller the value from 1, the lower the evaluation. On the other hand, as shown in FIGS. 16B and 16C, the unfolded length ratio RLr on the adhesive layer 1 side has no correlation with the evaluation result. Therefore, it is considered that the surface roughness Ra and Rz have nothing to do with the characteristics such as the transmission characteristics.

Next, the effect of this embodiment will be described in comparison with a comparative example. In the electromagnetic wave shielding wiring circuit board 110 of the present embodiment, the developed length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 is 1 to 1.4. Thereby, the transmission characteristic can be improved. On the other hand, in the comparative example, the developed length ratio RLr of the interface of the metal layer 2 on the adhesive layer 1 side is 1.6 or more. In that case, the transmission characteristics cannot be improved.

In the present embodiment, the developed length ratio RLr of the interface on the insulating layer 3 side is 1 to 1.5. Thereby, the transmission characteristic can be improved. Further, by setting the developed length ratio RLr of the interface on the insulating layer 3 side to 1 to 1.5, it is possible to balance the adhesion and the folding resistance.

In the present embodiment, the unfolded length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 is 1 to 1.4, and the unfolded length ratio RLr on the insulating layer 3 side is 1 to 1.5. Therefore, the folding resistance can be improved. On the other hand, in the comparative example, the folding resistance cannot be improved. For example, as the results of Comparative Examples 3 to 5 show, when the development length ratio RLr of the metal layer 2 on the insulating layer 3 side is larger than 2, the folding resistance cannot be improved.

In the present embodiment, the unfolded length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 is 1 to 1.4, and the unfolded length ratio RLr on the insulating layer 3 side is 1 to 1.5. Therefore, heat resistance and acid resistance can be improved. In particular, when the metal layer 2 is provided with the opening 4, the heat resistance and acid resistance are excellent. When there is no opening 4 as in the first embodiment, the heat resistance evaluation result remains “Good (Δ)” because the metal layer 2 has no opening, which is an adherend. It is conceivable that the water / gas generated from the FPC or the adhesive layer 1 is shielded by the metal layer 2 and expands due to this.

In the present embodiment, the increase in resistance value after aging can be suppressed. Factors that suppress the increase in resistance value after aging include factors due to the metal layer 2, factors due to the adhesive layer 1, and factors due to the structure of the wiring circuit board 100.

The factor due to the metal layer 2 is that the aperture ratio is reduced to 0.1% to 30%. If the aperture ratio is large, the resistance value after aging increases, but since it is within the above range, the increase in resistance value after aging can be suppressed. Further, the development length ratio RLr of the interface on the adhesive layer 1 side is set to 1 to 1.4.

The factor due to the adhesive layer 1 is that it controls the film thickness, the amount of the filler, the shape and the particle size of the adhesive layer 1. Reducing the film thickness of the adhesive layer 1, increasing the amount of filler, making the shape spherical, and increasing the particle size improve the continuity of the electromagnetic wave shield sheet 10 in the stacking direction. By controlling the above, it is possible to suppress an increase in the resistance value after a lapse of time.

The factor due to the structure of the wiring circuit board 100 is the earth via 64. Since the conductive layer 11 or 12 and the metal layer 2 can be electrically connected by the earth via 64, an increase in the resistance value after a lapse of time can be suppressed. In the present embodiment, the unfolded length ratio RLr of the interface on the adhesive layer 1 side of the metal layer 2 is 1 to 1.4, and the unfolded length ratio RLr on the insulating layer 3 side is 1 to 1.5. Therefore, even when the diameter of the earth via 64 is small, it is possible to suppress an increase in the resistance value after a lapse of time. On the other hand, in Comparative Example 5, even if the earth via 64 is formed, the increase in the resistance value after aging cannot be suppressed, and when the diameter of the earth via 64 is small, the resistance value after aging is inappropriate (×). Is.

Further, as in Example 13, if the aperture ratio is larger than in Examples 14 to 20, the transmission characteristics are not affected, but it is difficult to suppress the increase in resistance value after aging depending on the diameter of the earth via. There is a tendency.

Regarding the conductive filler in the adhesive layer 1, D95 is preferably twice or more, more preferably three times or more the film thickness of the adhesive layer 1. The amount of the conductive filler added is preferably 26 PHR or more, more preferably 64 PHR or more. The addition rate of the conductive filler is preferably greater than 25%, more preferably greater than 39%.

Although the first and second embodiments of the present invention and the respective embodiments have been described above, the present invention includes appropriate modifications that do not impair the purpose and advantages thereof, and is not limited by the above embodiments. Moreover, the configurations in Embodiments 1 and 2 and each Example may be combined as appropriate.

1 Adhesive layer 2 Metal layer 3 Insulation layer 4 Opening 5 Base material 6 Carrier 7 Base material 10, 10a, 10b Electromagnetic wave shield sheet 11, 12 Conductive layers 21, 22, 23 Insulation layers 30, 31, 32 Signal circuit 40, 41, 42 Ground circuit 50, 51 Wiring 61 Coverlay 62 Insulating adhesive layer 63 Through hole 64 Earth via 100, 200 Wiring circuit board 101, 201 Bottom surface 102 Top surface 103, 104 End face 110, 210 Electromagnetic wave shielded wiring circuit board 301, 302 Cover layer RLr unfolded length ratio

Claims (8)

With the adhesive layer,
Insulation layer and
A metal layer arranged between the adhesive layer and the insulating layer,
With
The film thickness of the metal layer is 0.2 to 10 [μm].
The development length ratio RLr of the interface on the adhesive layer side of the metal layer is 1 to 1.4.
The development length ratio RLr of the interface on the insulating layer side of the metal layer is 1 to 1.5.
An electromagnetic wave shield sheet characterized by this. The unfolded length ratio RLr of the interface on the adhesive layer side is smaller than the unfolded length ratio RLr of the interface on the insulating layer side.
The electromagnetic wave shield sheet according to claim 1. The metal layer has a plurality of openings penetrating from the interface on the adhesive layer side to the interface on the insulating layer side, and the aperture ratio is 0.1 to 30 [%].
The electromagnetic wave shield sheet according to claim 1 or 2. The electromagnetic wave shield sheet according to any one of claims 1 to 3 is bonded to at least one surface of the wiring circuit board.
An electromagnetic wave shielded wiring circuit board characterized by this. A wiring circuit board that extends in one direction,
The upper surface and the lower surface of the wiring circuit board are covered with the adhesive layer side, and at least a part of both end faces of the wiring circuit board in the plane parallel to the upper surface in the other direction orthogonal to the upper surface is covered. The electromagnetic wave shield sheet according to any one of claims 1 to 3 covered with the adhesive layer side.
An insulating first cover layer provided between the lower surface and the adhesive layer covering the lower surface.
An insulating second cover layer provided between the upper surface and the adhesive layer covering the upper surface,
With
The wiring circuit board
With the first conductive layer
The first insulating layer provided on the first conductive layer and
A signal circuit provided on the first insulating layer and having a portion extending in one direction,
The first insulating layer and the second insulating layer provided on the signal circuit,
The second conductive layer provided on the second insulating layer and
Including
The adhesive layer contains a conductive material and is connected to the second conductive layer via an earth via that penetrates the second cover layer.
An electromagnetic wave shielded wiring circuit board characterized by this. The adhesive layer was connected to the first conductive layer via an earth via penetrating the first cover layer.
The electromagnetic wave shielded wiring circuit board according to claim 5. The electromagnetic wave shielding wiring circuit board according to claim 5 or 6, wherein both end faces are covered with the adhesive layer from the first conductive layer to the second conductive layer. The electromagnetic wave shielding wiring circuit board according to any one of claims 4 to 7 is connected.
An electronic device characterized by that.