JP2021118343A - Electromagnetic wave shield sheet and electromagnetic wave shield wiring circuit board - Google Patents

Abstract

To provide an electromagnetic wave shield sheet having high washing resistance, circuit connection stability, excellent folding resistance, and good insulation properties, and a wiring circuit board using the electromagnetic wave shield sheet.SOLUTION: An electromagnetic wave shielding sheet 10 has a laminate including an adhesive layer 1, a metallic layer 2, and a protective layer 3 in this order. A surface of the metallic layer in contact with the adhesive layer has a 60° specular glossiness of 0-500 as determined in accordance with ISO 7668, and X expressed by formula (1) is less than 1.0. Formula (1) is X=Rz/T. Rz is the maximum height roughness of the metallic layer determined in accordance with JIS B0601. T is the thickness of the protective layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electromagnetic wave shield sheet and an electromagnetic wave shielding wiring circuit board, for example, an electromagnetic wave shield sheet suitable for being used by joining to a part of a component that emits an electromagnetic wave, and an electromagnetic wave using the electromagnetic wave shield sheet. Shielded wiring circuit board.

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.

With the increase in high-speed transmission of transmission signals, the electromagnetic wave shield sheet is also required to have electromagnetic wave shielding properties (hereinafter, high frequency shielding properties) corresponding to high frequency noise and reduction of transmission loss (hereinafter, sometimes referred to as transmission characteristics) in the high frequency region. ing. Patent Document 1 discloses a configuration in which a metal layer having a 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 electromagnetic wave shield sheet and reduces transmission loss.

International Publication No. 2013/077108 Japanese Unexamined Patent Publication No. 2019-121731

In recent years, in electronic devices typified by mobile phones, the electromagnetic wave shield sheet on the wiring circuit board built therein is also required to have high frequency shielding properties as the transmission signal is transmitted at high speed. Therefore, as described in Patent Document 1, it has been preferable to use a metal layer having a thickness of 0.5 to 12 μm as the conductive layer of the electromagnetic wave shield sheet.
However, simply using a metal layer having a thickness of 0.5 to 12 μm does not allow the electromagnetic wave shield sheet to exhibit sufficient high frequency shielding properties in the high frequency band, and the electromagnetic wave shielding sheet has better high frequency shielding properties. In order to make it possible, it has been required to further devise the metal layer.

Further, in the mounting process of an electronic device, the electromagnetic wave shielded wiring circuit board may be exposed to the cleaning process mainly for the purpose of removing dirt, dust and the like. Electromagnetic wave shielding property In order to remove all dirt, dust, etc. adhering to the wiring circuit board, a plurality of water-based, oil-based, acidic, and alkaline chemicals are used in the cleaning process. At that time, there is a problem that the resistance to decomposition / dissolution of the electromagnetic wave shield layer to cleaning chemicals is not sufficient and the electromagnetic wave shield layer is damaged.

With the worldwide spread of electronic devices such as smartphones and tablet terminals in recent years, reliability under all temperature and humidity conditions is required. When the wiring circuit board provided with the electromagnetic wave shield sheet of Patent Document 1 is exposed to a high temperature and high humidity environment, a water absorption phenomenon occurs due to the softening of the electromagnetic wave shield sheet, and the distance between the metal layer and the circuit increases due to swelling. There was a problem that the connection with the ground circuit was interrupted due to the distance (hereinafter referred to as circuit connection stability).
In Patent Document 2, the surface of the shield layer of the electromagnetic wave shield film (equivalent to the electromagnetic wave shield sheet) on the adhesive layer side is adjusted by adjusting the average length Rsm of the roughness curve element according to JIS B0601: 2013 within a certain range. , The ground wiring provided on the wiring circuit board and the shield layer are well grounded.

Further, 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. rice field.

The electromagnetic wave shield sheet is usually provided with an insulating protective layer on one side of the shield layer in order to prevent connection other than between the shield layer and the ground wiring. If the insulation of the protective layer is not sufficiently high, or if the steep unevenness of the shield layer penetrates the protective layer by heat pressing, when the protective layer of the electromagnetic wave shield layer comes into contact with a member other than the ground wiring, There was a problem that the connection was generated except between the shield layer and the ground wiring.

The present invention has been made in view of the above background, and an object of the present invention is an electromagnetic wave shield sheet having high cleaning resistance, circuit connection stability, excellent folding resistance, and good insulation. It is to provide a wiring circuit board using an electromagnetic wave shield sheet.

As a result of diligent studies by the present inventor, it has been found that the problems of the present invention can be solved in the following aspects, and the present invention has been completed.
That is, the electromagnetic wave shield sheet according to the present invention has a laminate having an adhesive layer, a metal layer, and a protective layer in this order, and the surface of the metal layer in contact with the adhesive layer is obtained in accordance with ISO 7668. The 60 ° mirror surface glossiness is 0 to 500, and X represented by the formula (1) is less than 1.0.
Equation (1)
X = Rz / T
(Rz is the maximum height roughness of the metal layer obtained in accordance with JIS B0601 and T is the thickness of the protective layer.)

According to the present invention, it is possible to provide an electromagnetic wave shield sheet having high cleaning resistance, circuit connection stability, excellent folding resistance, and good insulation properties, and a wiring circuit board using the electromagnetic wave shield sheet. Has an effect.

It is sectional drawing which illustrates the electromagnetic wave shield sheet which concerns on this embodiment. It is a figure which illustrated the ratio comparison of the specular reflection light / diffuse reflection light of the surface which the degree of roughness is different. It is a schematic cut section sectional view which shows an example of the electromagnetic wave shielded wiring circuit board which concerns on the explanation of the pushing effect of a non-conductive particle. It is a schematic cut section sectional view which shows an example of the electromagnetic wave shielded wiring circuit board which concerns on this embodiment. 2 is a cross-sectional view of two types in which the relationship between the thickness T of the protective layer and the maximum height roughness Rz of the metal layer is different. It is a schematic plan view of circuit connection stability evaluation, and the cut section sectional view.

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.

<Electromagnetic wave shield sheet>
The electromagnetic wave shield sheet of the present invention has a laminate having at least an adhesive layer, a metal layer, and a protective layer in this order. FIG. 1 is a cross-sectional view illustrating the electromagnetic wave shield sheet 10 according to the embodiment of the present invention. As shown in FIG. 1, the electromagnetic wave shield sheet 10 has a laminate having an adhesive layer 1, a metal layer 2, and a protective layer 3 in this order, and the metal layer 2 is a laminate of the adhesive layer 1 and the protective layer 3. It is placed in between.
That is, the electromagnetic wave shield sheet according to the present invention has a laminate having an adhesive layer, a metal layer, and a protective layer in this order, and the surface of the metal layer in contact with the adhesive layer is determined in accordance with ISO 7668. The maximum height roughness Rz obtained in accordance with JIS B0601 on the surface of the metal layer in contact with the adhesive layer, which has a 60 ° mirror surface gloss of 0 to 500, and the thickness T of the protective layer are used. Since X represented by the formula (1) is less than 1.0, high cleaning resistance, circuit connection stability, good insulation and the like can be exhibited.
For the electromagnetic wave shield sheet 10, for example, a wiring circuit board which is an adherend and a surface on the adhesive layer 1 side are bonded to form an electromagnetic wave shield layer to produce an electromagnetic wave shielded wiring circuit board. That is, of the surface of the metal layer 2, the surface facing the signal wiring and the ground wiring in the wiring circuit board is the surface in close contact with the adhesive layer 1.

《Metal layer》
The metal layer of the present invention has a function of imparting high-frequency shielding property to the electromagnetic wave shielding sheet. The surface of the metal layer on the side in contact with the adhesive layer has a 60 ° mirror glossiness of 0 to 500 determined in accordance with ISO 7668. Further, the metal layer of the present invention is characterized in that X represented by the formula (1) is less than 1.0.
Equation (1)
X = Rz / T
(Rz is the maximum height roughness of the metal layer obtained in accordance with JIS B0601 and T is the thickness of the protective layer.)
Details of the 60 ° mirror gloss, Rz, and the effects obtained by these controls will be described later.

[60 ° mirror gloss]
The 60 ° mirror gloss is a parameter standardized in ISO 7668 and represents the gloss of the surface to be measured. The mirror glossiness can be measured by irradiating the surface to be measured with light (incident light) at a constant incident angle, detecting the light reflected with a certain accuracy (specular reflected light) by a detector, and quantifying the light.
The incident light emitted to the surface to be measured is reflected, transmitted, or absorbed when it reaches the surface to be measured. Further, the reflection includes specular reflection and diffuse reflection, and the light reflected at the same angle (reflection angle) as the incident angle is the specular reflected light, which is the light detected by the mirror gloss measurement. The 60 ° mirror surface gloss is a value measured at an incident angle and a reflection angle of 60 °.
When the surface to be measured is a metal layer, most of the incident light is reflected. The ratio of the reflected light to be specular reflection or diffuse reflection is determined by the degree of roughness of the metal layer surface. FIG. 2 shows a cross-sectional view of two types of measurement target surfaces having different degrees of roughness. On the surface to be measured having a small degree of roughness, the ratio of the specularly reflected light is large, while the diffusely reflected light is small and the value of the specular glossiness is large. On the other hand, on the surface to be measured having a large degree of roughness, the ratio of the specular reflected light is small, while the diffuse reflected light is large and the value of the specular gloss is small. That is, the mirror glossiness can be used as an index for measuring the degree of roughness of the surface to be measured.

As a result of diligent studies, the inventor has found that the cleaning resistance of the electromagnetic wave shielding sheet and the circuit connection stability are improved by setting the 60 ° mirror surface gloss of the metal layer to 0 to 500. When the 60 ° mirror surface gloss of the metal layer is 0 to 500, it means that the surface of the metal layer is formed with irregularities having a sufficient roughness. The adhesive layer provided on the surface of the metal layer having the above-mentioned state penetrates into the unevenness of the surface of the metal layer having a high degree of roughness, and the adhesion between the metal layer and the adhesive layer becomes strong. Therefore, even when the electromagnetic wave shield sheet and the electromagnetic wave shield wiring circuit board are exposed to cleaning chemicals, the chemicals do not flow into the interface between the metal layer and the adhesive layer, and defects such as delamination can be suppressed. can. In addition, since there is no inflow of chemicals between the metal layer and the adhesive layer, discoloration and corrosion of the metal layer can be suppressed, especially when the cleaning chemicals have acidity or alkalinity. The invention exhibits excellent cleaning resistance.

Further, by setting the 60 ° mirror gloss of the metal layer to 0 to 500, when the adhesive layer is laminated on the metal layer, a structure in which the convex portion of the metal layer penetrates the adhesive layer can be formed. It will be possible. The electromagnetic wave shielding wiring circuit board produced by laminating the electromagnetic wave shielding sheet having the structure on the wiring circuit board has a convex portion of the metal layer even when the adhesive layer is swollen when exposed to a high temperature and high humidity environment. A stable circuit connection can be achieved by maintaining contact with the ground circuit.

From these facts, the 60 ° mirror glossiness of the metal layer is preferably 0 to 300, more preferably 0 to 100, further preferably 0 to 50, and 0 to 10. Is particularly preferable.

Regarding the mechanism that brought about the effect of the invention, the mechanism described above involves estimation, and the mechanism that exerts the effect is not limited in any way.

[Rz of metal layer]
The maximum height roughness Rz is a parameter defined by JIS B0601 and represents the distance from the highest point to the lowest point on the measurement surface.

The electromagnetic wave shield sheet of the present invention has a value X represented by the formula (1) formed by the maximum height roughness Rz (μm) of the surface in contact with the adhesive layer of the metal layer and the thickness T (μm) of the protective layer. , Less than 1.0, more preferably less than 0.97.
When X is less than 1.0, the insulating property of the electromagnetic wave shielding layer is improved. As shown in FIG. 5A, when X is 1.0 or more, the thickness T of the protective layer is smaller than the maximum height roughness Rz of the metal layer, so that the unevenness of the metal layer is the protective layer. The metal layer penetrates through and conducts with a part other than the ground wiring. On the other hand, as shown in FIG. 5B, when X is less than 1.0, the thickness T of the protective layer becomes larger than the maximum height roughness Rz of the metal layer, so that the unevenness of the metal layer Does not penetrate the protective layer, and the outermost surface of the electromagnetic wave shield layer has improved insulation.
Equation (1)
X = Rz / T
(Rz is the maximum height roughness of the metal layer obtained in accordance with JIS B0601 and T is the thickness of the protective layer.)

The reason why X is 1.0 or more is that, for example, the uneven height of the surface in contact with the protective layer of the metal layer is higher than the thickness of the protective layer, or when the protective layer is formed by coating or the like, a coating defect is caused. It is assumed that a metal layer is formed on the protective layer by plating or the like, and a metal layer is formed along the shape of the defect. The above-mentioned coating defects may occur, for example, when a resin composition containing particles having an average particle size larger than the thickness of the protective layer is applied. The above-mentioned factors for X to be 1.0 or more are examples.

[60 ° mirror gloss and Rz control method]
The method of controlling the 60 ° mirror surface gloss and Rz of the metal layer surface is, for example, to form a protective layer having irregularities from a resin composition containing particles, and then to form a metal layer on the protective layer by plating, sputtering, or the like. Method, method of forming a metal layer by plating or sputtering after spraying particles on a protective layer formed from a resin composition, blasting, plasma irradiation, electron beam treatment, chemical treatment, or embossing on the surface of the protective layer. A method of forming a metal layer on a protective layer by plating, sputtering, etc., a method of adhering roughened particles on the surface of a metal foil to form a roughened surface, A method of polishing a metal surface using a buff described in Japanese Patent Application Laid-Open No. 13473, a method of polishing a metal surface using a polishing cloth, and a method of forming a metal layer on a carrier material having desired irregularities by a method such as plating. Examples thereof include a method of transferring the unevenness of the carrier material, a shot blast method of spraying a polishing material onto a metal surface with compressed air, and a method of pressing a mold having a desired unevenness against a metal foil to transfer the uneven shape. The method for controlling the 60 ° mirror gloss and Rz on the surface of the metal layer is not limited to the illustrated method, and conventionally known methods can be applied.

[Thickness of metal layer]
The thickness of the metal layer is preferably 0.3 to 10 μm. When the thickness of the metal layer is 0.3 to 10 μm, both circuit connection stability and folding resistance can be achieved. When the thickness of the metal layer is 0.3 μm or more, the metal layer is less likely to break when pressed by non-conductive particles in the protective layer during hot pressing, and circuit connection stability is improved. The pushing action of the non-conductive particles will be described later. Further, when the thickness of the metal layer is 10 μm or less, it becomes difficult for the metal layer to crack at the time of bending, and the folding resistance is improved. The thickness of the metal layer is more preferably 0.5 to 5 μm.

[Components of metal layer]
As the metal layer, for example, a metal foil, a metal vapor deposition film, a metal plating film, or the like can be used.
The metal used for the metal foil is preferably a conductive metal such as aluminum, copper, silver, or gold, and any one type of metal or an alloy of a plurality of metals can be used. Copper, silver and aluminum are more preferable, and copper is even more preferable from the viewpoint of high frequency shielding property and cost. As copper, for example, it is preferable to use rolled copper foil or electrolytic copper foil.
As the metal used for the metal vapor deposition film and the metal plating film, for example, one kind of conductive metal such as aluminum, copper, silver and gold, or an alloy of a plurality of metals is preferably used, and copper and silver are more preferable. One surface or both surfaces of the metal foil, the metal vapor deposition film, and the metal plating film may be coated with a metal or an organic substance such as a rust preventive.

[Aperture]
The metal layer may have a plurality of openings. Having an opening improves solder reflow resistance. By having an opening, when the electromagnetic wave shielding wiring circuit board is soldered, the volatile components contained in the polyimide film and the coverlay adhesive of the wiring circuit board are released to the outside, and the coverlay adhesive and the electromagnetic wave shielding sheet are released. It is possible to suppress the occurrence of poor appearance due to interfacial peeling.

The shape of the opening seen from the surface of the metal layer can be formed as needed, such as a perfect circle, an ellipse, a quadrangle, a polygon, a star, a trapezoid, or a branch. From the viewpoint of manufacturing cost and ensuring the toughness of the metal layer, the shape of the opening is preferably a perfect circle and an ellipse.

[Aperture ratio of metal layer]
The aperture ratio of the metal layer is preferably in the range of 0.10 to 20%, and can be calculated by the following mathematical formula (2).
Equation (2)
(Aperture ratio [%]) = (Area of opening per unit area) / (Area of opening per unit area + Area of non-opening per unit area) x 100

When the aperture ratio is 0.10 or more, the volatile components during the solder reflow process can be sufficiently released, and the appearance deterioration due to the interfacial peeling of the coverlay adhesive and the electromagnetic wave shield sheet and the deterioration of the connection reliability can be prevented. It is preferable because it can be suppressed.
On the other hand, when the aperture ratio is 20% or less, the amount of electromagnetic noise passing through the opening portion can be reduced and the shielding property can be improved, which is preferable. The range of the aperture ratio that achieves both solder reflow resistance and high frequency shielding property at a high level is more preferably 0.30 to 15%, and even more preferably 0.50 to 6.5%.

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

[Manufacturing method of a metal layer having an opening]
As a method for producing a metal layer having an opening, a conventionally known method can be applied, and a method (i) of forming a pattern resist layer on a metal foil and etching the metal foil to form an opening, a predetermined method. A method of screen-printing an anchoring agent with a pattern and metal-plating only the anchoring agent-printed surface (ii), a manufacturing method described in Japanese Patent Application Laid-Open No. 2015-63730 (iii), 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 having an opening with a carrier can be obtained by forming a release layer on the surface and electroplating. Among these, an opening forming method (i) in which a pattern resist layer is formed and a metal foil is etched. However, it is preferable because the shape of the opening can be precisely controlled. However, the shape of the opening may be controlled by other methods, and the method for manufacturing the metal layer is not limited to the etching method (i).

《Adhesive layer》
The adhesive layer has a function of laminating an electromagnetic wave shield sheet on a wiring circuit board and adhering the electromagnetic wave shield sheet and the wiring circuit board when manufacturing an electromagnetic wave shielded wiring circuit board.

The adhesive layer can be formed using a resin composition. The resin composition contains a binder resin. As the binder resin, either a thermoplastic resin or a thermosetting resin and a curing agent can be used. As the adhesive layer, either a non-conductive adhesive layer or a conductive adhesive layer can be used, and the conductive adhesive layer exhibits conductivity by containing a conductive filler or the like.

Further, as the conductive adhesive layer, either an isotropic conductive adhesive layer or an anisotropic conductive adhesive layer can be used. The isotropic conductive adhesive layer has conductivity in the vertical direction and the horizontal direction when the electromagnetic wave shield sheet is placed horizontally. Further, the anisotropic conductive adhesive layer has conductivity only in the vertical direction when the electromagnetic wave shield sheet is placed horizontally.
The conductive adhesive layer may be either isotropically conductive or anisotropically conductive, and in the case of anisotropically conductive, the cost can be reduced, which is preferable.

[Thermoplastic resin]
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, polyimide resins, and liquid crystals. Examples include 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, and liquid crystal polymers, fluororesins and the like can be mentioned.
The thermoplastic resin can be used alone or in combination of two or more.

[Thermosetting resin]
A thermosetting resin is a resin having a plurality of functional groups capable of reacting with a curing agent. Functional groups include, for example, hydroxyl groups, phenolic hydroxyl groups, acid anhydride groups, methoxymethyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, and blocked groups. Examples thereof include an isocyanate group, a blocked carboxyl group and a silanol group. The thermosetting resin includes, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, polyurethane urea resin, epoxy resin, oxetane resin, phenoxy resin, polyimide resin, polyamide resin, polyamideimide resin, and phenolic resin. Known resins such as resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins can be mentioned.
The thermosetting resin can be used alone or in combination of two or more.

Among these, polyurethane resin, polyurethane urea resin, polyester resin, epoxy resin, phenoxy resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of cleaning resistance.

[Curing agent]
The curing agent has a plurality of functional groups capable of reacting with the functional groups of the thermosetting resin. Examples of the curing agent include known compounds such as epoxy compounds, acid anhydride group-containing compounds, isocyanate compounds, aziridine compounds, amine compounds, phenol compounds, and organic metal compounds.
The curing agent can be used alone or in combination of two or more.

The curing agent is preferably contained in an amount of 1 to 50 parts by weight based on 100 parts by weight of the thermosetting resin. When the amount of the curing agent is 1 part by weight or more, a strong crosslinked structure is formed in the adhesive layer, and the dissolution and swelling of the adhesive layer during exposure to a cleaning agent or high temperature and high humidity are suppressed. It can improve cleaning resistance and circuit connection stability. On the other hand, when the amount of the curing agent is 50 parts by weight or less, it is possible to suppress excessive curing of the adhesive layer and suppress the occurrence of cracks at the time of bending. The curing agent is more preferably contained in an amount of 3 to 40 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of the thermosetting resin.

The thermoplastic resin and the thermosetting resin can be used alone or in combination of both.

[Conductive filler]
The conductive filler has a function of imparting conductivity to the adhesive layer. As the material of the conductive filler, conductive metals such as gold, platinum, silver, copper and nickel and alloys thereof, and fine particles of the conductive polymer are preferable, and silver is more preferable from the viewpoint of cost and conductivity.
Further, composite fine particles having a coating layer covering the surface of the nuclei with a metal or resin as the nuclei instead of the fine particles of a single material are also preferable from the viewpoint of cost reduction. Here, it is preferable that the nucleolus is appropriately selected from inexpensive nickel, silica, copper and alloys thereof, and resins. The coating layer is preferably a conductive metal or a conductive polymer. Examples of the conductive metal include gold, platinum, silver, nickel, manganese, indium and the like, and alloys thereof. Examples of the conductive polymer include polyaniline and polyacetylene. Among these, silver is preferable from the viewpoint of price and conductivity.

The shape of the conductive filler is not limited as long as the desired conductivity can be obtained. Specifically, for example, spherical, flake-shaped, leaf-shaped, dendritic-shaped, plate-shaped, needle-shaped, rod-shaped, and grape-shaped are preferable. Further, two kinds of conductive fillers having different shapes may be mixed.
The conductive filler may be used alone or in combination of two or more.

The average particle diameter of the conductive filler, D is a ₅₀ average particle size, from the viewpoint of sufficiently ensuring conductivity is preferably at least 2 [mu] m, more preferably at least 5 [mu] m, and more preferably be 7μm or more. On the other hand, from the viewpoint of achieving compatibility with the thinness of the adhesive layer, 30 μm or less is preferable, 20 μm or less is more preferable, and 15 μm or less is further preferable. D ₅₀ average particle size can be determined by a laser diffraction scattering method particle size distribution measuring apparatus or the like.

The content of the conductive filler in the adhesive layer is preferably 35 to 90% by weight, more preferably 39 to 70% by weight, still more preferably 40 to 65% by weight. When the content is 35% by weight or more, the connection between the adhesive layer and the ground wiring is improved, so that the high frequency shielding property and the thermal cycle reliability are improved. On the other hand, when it is 90% by weight or less, the solder reflow resistance and the transmission characteristics are improved.

The resin composition 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, and an ultraviolet absorber for the purpose of improving desired physical properties and imparting functions. Agents, defoaming agents, leveling adjusters, fillers, flame retardants, etc. can be blended.

The resin composition can be obtained by mixing and stirring the materials described above. For stirring, a known stirring device such as a dispermat or a homogenizer can be used.

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

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.

The thickness of the adhesive layer is not particularly limited, but is preferably smaller than Rz on the surface of the metal layer. Since the thickness of the adhesive layer is smaller than Rz on the surface of the metal layer, when the electromagnetic wave shield sheet is adhered to the printed wiring board, the tip of the unevenness of the metal layer easily comes into contact with the ground wiring. Among them, when the thickness of the adhesive layer is 1 to 20 μm, it is particularly preferable because it can achieve both thin film property, adhesion to the base material, and connection (contact) to the ground wiring.

《Protective layer》
The protective layer is located on the surface of the electromagnetic wave shielding wiring circuit board composed of the electromagnetic wave shielding sheet and the wiring circuit board, and when cleaning the electromagnetic wave shielding wiring circuit board, the metal layer and the adhesive layer come into contact with the cleaning chemicals. It has a function to prevent the metal layer and a function to cut off the electrical connection between the metal layer and the outer conductor by covering the metal layer.

The protective layer can be formed using a resin composition. The resin composition contains a binder resin. As the binder resin, either a thermoplastic resin or a thermosetting resin and a curing agent can be used.

The weight average molecular weight of the binder resin is preferably 10,000 or more. When the weight average molecular weight of the binder resin is 10,000 or more, decomposition and dissolution of the coating film when exposed to cleaning chemicals can be suppressed, and cleaning resistance is improved. The weight average molecular weight of the thermosetting resin is more preferably 30,000 or more, and further preferably 50,000 or more. The weight average molecular weight of the binder resin is preferably 500,000 or less from the viewpoint of improving compatibility and dispersibility with other components contained in the protective layer.

[Thermoplastic resin]
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, polyimide resins, and liquid crystals. Examples include 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, and liquid crystal polymers, fluororesins and the like can be mentioned.
The thermoplastic resin can be used alone or in combination of two or more.

[Thermosetting resin]
A thermosetting resin is a resin having a plurality of functional groups capable of reacting with a curing agent. Functional groups include, for example, hydroxyl groups, phenolic hydroxyl groups, methoxymethyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, blocked isocyanate groups and blocked functional groups. Examples thereof include a carboxyl group and a silanol group. The thermosetting resin includes, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, polyurethane urea resin, epoxy resin, oxetane resin, phenoxy resin, polyimide resin, polyamide resin, polyamideimide resin, and phenolic resin. Known resins such as resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins can be mentioned.
The thermosetting resin can be used alone or in combination of two or more.

Among these, polyurethane resin, polyurethane urea resin, polyester resin, epoxy resin, phenoxy resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of solder reflow resistance.

[Curing agent]
The curing agent has a plurality of functional groups capable of reacting with the functional groups of the thermosetting resin. Examples of the curing agent include known compounds such as epoxy compounds, acid anhydride group-containing compounds, isocyanate compounds, aziridine compounds, amine compounds, phenol compounds, and organic metal compounds.
The curing agent can be used alone or in combination of two or more.

The curing agent is preferably contained in an amount of 1 to 50 parts by weight, more preferably 3 to 40 parts by weight, still more preferably 3 to 30 parts by weight, based on 100 parts by weight of the thermosetting resin.

The thermoplastic resin and the thermosetting resin can be used alone or in combination of both.

[Non-conductive particles]
The protective layer preferably contains non-conductive particles. The non-conductive particles have a function of improving the insulating property of the protective layer and assisting the grounding of the metal layer and the ground wiring by pushing the metal layer during hot pressing.

When the electromagnetic wave shield sheet is adhered to the printed wiring board, a hot press is mainly used. During the hot press, the electromagnetic wave shield sheet and the printed wiring board are pressed by the hot press plate from above and below as shown in FIG. , Under pressure. At that time, the non-conductive particles 4 contained in the protective layer 3 receive the pressure from the heat press and transmit the pressure to the metal layer 2. As a result, the metal layer 2 is pushed toward the adhesive layer 1 side, and finally comes into contact with the ground wiring 5. By this action, the metal layer 2 and the ground wiring 5 are electrically connected, and the electromagnetic wave shielding layer 12 can exhibit excellent high-frequency shielding properties.

Examples of the non-conductive particles include non-conductive ceramics, pigments, dyes and the like, and ceramics are preferable because they have high hardness and can be transmitted to the metal layer without relaxing the pressure received during hot pressing.

Among the non-conductive particles, it is preferable that the non-conductive particles have a volume resistivity of 1.0 × 10 ^{10 Ω · cm or more.} When the non-conductive particles have a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more, the insulating property of the protective layer can be further improved. The volume resistivity of the substance contained in the non-conductive particles ^{is more preferably 1.0 × 10 12} Ω · cm or more, and further preferably 1.0 × 10 ¹⁴ Ω · cm or more. Materials with a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more include aluminum dioxide (alumina), zirconium dioxide (zirconia), silicon dioxide (silica), boron carbide, aluminum nitride, boron nitride, magnesium oxide (magnesia). , Titanium oxide, etc. Among them, a more preferable substance is zirconium dioxide (ZrO ₂ ; volume resistivity 1.0 × 10 ¹² Ω · cm), and a more preferable substance is silica (SiO ₂ ; volume). The resistivity is 1.0 × 10 ¹⁴ Ω · cm). The volume resistivity of the substance contained in the non-conductive particles can be measured according to JIS C2141.

As the non-conductive particles, any shape can be used as long as the above-mentioned metal layer pressing mechanism can be realized, but the non-conductive particles are preferably massive, indefinite, substantially spherical, spherical, or true spherical. Is preferable. The non-conductive particles may be porous or may have pores inside as long as they can realize the above-mentioned pressing mechanism of the metal layer.

The protective layer preferably contains 3 to 80% by weight of non-conductive particles. When the amount of non-conductive particles contained in the protective layer is 3% by weight or more, the insulating property is improved, and when it is 80% by weight or less, the film forming property is improved. The non-conductive particles contained in the protective layer are more preferably 5 to 60% by weight, and particularly preferably 15 to 40% by weight.
From the viewpoint of the insulating property of the protective layer, ^{the content of the non-conductive particles having a volume resistivity of 1.0 × 10 10} Ω · cm or more is preferably 85 to 100% by weight based on 100% by weight of the non-conductive particles.

The average particle size of the non-conductive particles is not particularly limited as long as the 60 ° mirror gloss on the surface of the metal layer and X calculated by the formula (1) can be set as desired values, but the circuit connection is stable. The range of 1 to 50 μm is preferable because it is possible to achieve both property, folding resistance, and insulation. It is more preferably 4 to 20 μm, and even more preferably 6 to 14 μm.
The average particle size can be determined by a laser diffraction / scattering method particle size distribution measuring device or the like.

The ratio (average particle size / thickness) of the average particle size (μm) of the non-conductive particles to the protective layer thickness (μm) is preferably in the range of 1/4 to 1.5 / 1. When the ratio of the average particle size of the non-conductive particles to the thickness of the protective layer is in the range of 1/4 to 1.5 / 1, the circuit connection stability, the folding resistance, and the insulating property are improved. When the (average particle size / thickness) is 1.5 / 1 or less, non-conductive particles pop out from the protective layer to generate voids, and plating is formed through the voids to form a protective layer. It is possible to suppress the formation of a metal layer penetrating the metal layer, and the insulating property is improved. On the other hand, (average particle size /
When the thickness) is 1/4 or more, the action of the non-conductive particles pushing the metal layer during hot pressing becomes stronger, the connection with the ground wiring is improved, and the circuit connection stability is improved, which is preferable.

The resin composition also includes a silane coupling agent, a rust preventive, a reducing agent, an antioxidant, a tackifier resin, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling adjuster, a filler, and a flame retardant as optional components. Etc. can be mixed.
Further, pigments and the like other than non-conductive particles can also be added for the purpose of coloring the protective layer and enhancing the design, as long as the function as the protective layer is not impaired. Examples of such pigments include carbon black, carbon graphite, carbon nanotubes, graphene and the like. It is preferable to add carbon black, carbon graphite, carbon nanotubes, graphene and the like in the range of the addition amount that can obtain a good evaluation of "practical" or higher in the insulation evaluation described later.

The resin composition can be obtained by mixing and stirring the materials described above. For stirring, a known stirring device such as a dispermat or a homogenizer can be used.

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

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.

Further, as the protective layer, a film formed of an insulating resin such as polyester, polycarbonate, polyimide, polyamideimide, polyamide, polyphenylene sulfide, and polyetheretherketone can also be used.

The thickness of the protective layer is preferably 2 to 20 μm. When the thickness of the protective layer is 2 to 20 μm, it is possible to suppress dissolution of the protective layer and peeling from the metal layer after exposure to the cleaning chemicals.

The electromagnetic wave shield sheet may include other functional layers in addition to the adhesive layer, the metal layer, and the protective layer. The other functional layer is a layer having functions such as hard coat property, water vapor barrier property, oxygen barrier property, thermal conductivity, low dielectric constant, high dielectric constant, and heat resistance.

The electromagnetic wave shield sheet of the present invention can be used for various purposes in which electromagnetic waves need to be shielded. For example, it can be used not only for flexible printed wiring boards, but also for rigid printed wiring boards, COFs, TABs, flexible connectors, liquid crystal displays, touch panels, and the like. It can also be used as a member for blocking electromagnetic waves of a personal computer case, a building material such as a wall of a building material and a window glass, a vehicle, a ship, an aircraft, and the like.

In the electromagnetic wave shield sheet of the present invention, when a thermoplastic resin is used as the binder resin in the adhesive layer, the contained thermoplastic resin exists in a solid state, and the thermoplastic resin is melted and cooled by the wiring circuit board and the hot press. The desired adhesive strength can be obtained by later solidifying again.

In the electromagnetic wave shield sheet of the present invention, when a thermosetting resin is used as the binder resin in the adhesive layer, the contained thermosetting resin and curing agent are present in an uncured state (B stage), and the wiring circuit board and heat are generated. By curing by pressing (C stage), the desired adhesive strength can be obtained. The uncured state includes a semi-cured state in which a part of the curing agent is cured.

The electromagnetic wave shield sheet is generally stored with a peelable sheet attached to the adhesive layer and the protective layer in order to prevent foreign matter from adhering.

The peelable sheet is a sheet obtained by performing a known peeling treatment on a base material such as paper or plastic.

<Electromagnetic wave shielded wiring circuit board>
The electromagnetic wave shielded wiring circuit board includes an electromagnetic wave shield layer and a cover coat layer formed from the electromagnetic wave shield sheet of the present invention, and a wiring circuit board having a circuit pattern having signal wiring and ground wiring and an insulating base material. ..
The wiring circuit board has a circuit pattern having signal wiring and ground wiring on the surface of the insulating base material, and insulates and protects the signal wiring and ground wiring on the wiring circuit board, and at least one on the ground wiring. A cover coat layer having vias is formed in the portion, the adhesive layer surface of the electromagnetic wave shield sheet is arranged on the cover coat layer, and then the electromagnetic wave shield sheet is hot-pressed to allow the adhesive layer to flow into the via. It can be manufactured by adhering it to the ground wiring.

An example of the electromagnetic wave shielding wiring circuit board of the present invention will be described with reference to FIG.
The electromagnetic wave shield layer 12 has a structure including an adhesive layer 1, a metal layer 2, and a protective layer 3.

The cover coat layer 8 is an insulating material that covers the signal wiring of the wiring circuit board and protects it from the external environment. As the cover coat layer, a polyimide film with a thermosetting adhesive, a thermosetting or ultraviolet curable solder resist, or a photosensitive coverlay film is preferable, and a photosensitive coverlay film is more preferable for fine processing. Further, as the cover coat layer, a known resin having heat resistance and flexibility such as polyimide is generally used. The thickness of the cover coat layer is usually about 10 to 100 μm.

The circuit pattern includes a ground wiring 5 for grounding and a signal wiring 6 for sending an electric signal to an electronic component. Both are generally formed by etching a copper foil. The thickness of the circuit pattern is usually about 1 to 50 μm.

The insulating base material 9 is a support for a circuit pattern, and a flexible plastic such as polyester, polycarbonate, polyimide, polyphenylene sulfide, or liquid crystal polymer is preferable, and liquid crystal polymer and polyimide are more preferable. 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 wiring circuit board for transmitting a high frequency signal.
When the wiring circuit board is a rigid wiring board, glass epoxy is preferable as the constituent material of the insulating base material. By providing an insulating base material such as these, the wiring circuit board can obtain high heat resistance.

The heat pressing between the electromagnetic wave shield sheet 10 and the wiring circuit board is generally performed under the conditions of a temperature of about 150 to 190 ° C., a pressure of about 1 to 3 MPa, and a time of about 1 to 60 minutes. The adhesive layer 1 and the cover coat layer 8 are brought into close contact with each other by a hot press. The thermosetting resin reacts and cures by the hot press to form the electromagnetic wave shield layer 12.
In addition, in order to accelerate curing, post-cure may be performed at 150 to 190 ° C. for 30 to 90 minutes after hot pressing.

The opening area of the via 11 is preferably 0.8 mm ² or less, 0.008 mm ² or more. By setting the above range, the area of the ground wiring can be narrowed, and the size of the printed wiring board can be reduced.
The shape of the via is not particularly limited, and any of them can be used depending on the application such as a circle, a square, a rectangle, a triangle, and an amorphous shape.

It is preferable to laminate the electromagnetic wave shield layer on both sides of the wiring circuit board from the viewpoint of more effectively suppressing the leakage of electromagnetic waves. In addition, the electromagnetic wave shield layer in the electromagnetic wave shielding wiring circuit board of the present invention can be used as a ground circuit in addition to shielding electromagnetic waves, thereby omitting a part of the ground circuit and reducing the area of the wiring circuit board. This makes it possible to reduce costs and incorporate it into a narrow area inside the housing.

Further, the signal wiring is not particularly limited, and can be used for either a single-ended circuit consisting of one signal wiring or a differential circuit consisting of two signal wirings, but the differential circuit is more suitable. preferable. On the other hand, when the circuit pattern area of the wiring circuit board is limited and it is difficult to form the ground circuit in parallel, the ground circuit is not provided next to the signal circuit, and the electromagnetic wave shield layer is used as the ground circuit. A printed wiring board structure having a ground in the thickness direction can also be used.

The electromagnetic wave shielding wiring circuit board of the present invention is preferably provided (mounted) on electronic devices such as notebook PCs, mobile phones, smartphones, and tablet terminals in addition to liquid crystal displays and touch panels.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. Further, in the examples, "part" means "part by weight", and "%" means "% by weight".

The acid value of the resin, the weight average molecular weight (Mw), the glass transition temperature (Tg), and the average particle diameters of the conductive filler and the non-conductive particles were measured by the following methods.

<< Measurement of acid value of binder resin >>
The acid value was measured according to JIS K0070. Precisely weigh about 1 g of the sample in an Erlenmeyer flask with a stopper, and add 100 ml of a mixed solution of tetrahydrofuran / ethanol (volume ratio: tetrahydrofuran / ethanol = 2/1) to dissolve the sample. To this, a phenolphthalein test solution was added as an indicator, titrated with a 0.1 N alcoholic potassium hydroxide solution, and the end point was when the indicator held a pink color for 30 seconds. The acid value was calculated by the following formula (unit: mgKOH / g).
Acid value (mgKOH / g) = (5.611 × a × F) / S
However,
S: Sample collection amount (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: Titer of 0.1N alcoholic potassium hydroxide solution

<< Measurement of weight average molecular weight (Mw) of binder resin >>
The weight average molecular weight (Mw) was measured by using GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation. GPC is a liquid chromatography in which a substance dissolved in a solvent (THF; tetrahydrofuran) is separated and quantified according to the difference in molecular size. In the measurement in the present invention, two "LF-604" (manufactured by Showa Denko KK: GPC column for rapid analysis: 6 mm ID x 150 mm size) are connected in series to the column, the flow rate is 0.6 ml / min, and the column temperature is set. It was carried out under the condition of 40 ° C., and the weight average molecular weight (Mw) was determined in terms of polystyrene.

<< Glass transition temperature (Tg) of binder resin >>
The Tg was measured by differential scanning calorimetry (“DSC-1” manufactured by METTLER TOLEDO).

<< Measurement of average particle size of conductive filler and non-conductive particles >>
D ₅₀ average particle size, using a laser diffraction scattering method particle size distribution measuring apparatus LS13320 (manufactured by Beckman Coulter, Inc.) at Tornado Dry Powder sample module, numbers conductive filler and non-conductive particles obtained by measuring The cumulative value in the cumulative particle size distribution is 50%. The refractive index was set to 1.6.

Subsequently, the materials used in the examples are shown below.
"material"
-Binder resin 1: Polyurethane urea resin with an acid value of 5 mgKOH / g, a weight average molecular weight of 70,000, and a Tg of -5 ° C (manufactured by Toyochem Co., Ltd.)
-Epoxy compound: "JER828" (bisphenol A type epoxy resin epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Co., Ltd.-Aziridine compound: "Chemitite PZ-33" manufactured by Nippon Shokubai Co., Ltd.-Non-conductive particles 1: Sunsphere H-121
(:; Manufactured volume resistivity 1.0 × ^{10 14} Ω · cm content of 99% .AGC Si-Tech Co. 12.0μm, SiO _{2 D 50} average particle size)
-Non-conductive particles 2: Sunsphere NP-100
(:; Manufactured volume resistivity 1.0 × ^{10 14} Ω · cm content of 99% .AGC Si-Tech Co. 8.0μm, SiO _{2 D 50} average particle size)
-Non-conductive particles 3: Sunsphere H-51
(:; Manufactured volume resistivity 1.0 × ^{10 14} Ω · cm content of 99% .AGC Si-Tech Co. 5.0μm, SiO _{2 D 50} average particle size)
-Non-conductive particles 4: Sunsphere H-31
(:; Manufactured volume resistivity 1.0 × ¹⁰ content 99% ^{14 Ω} · cm .AGC Si-Tech Co. 3.0μm, SiO _{2 D 50} average particle size)
Non-conductive particles 5: Sunsphere H-201
(:; Manufactured volume resistivity 1.0 × ^{10 14} Ω · cm content of 99% .AGC Si-Tech Co. 15.0μm, SiO _{2 D 50} average particle size)
-Non-conductive particles 6: Zirconia beads NZ10SP
_{(D 50} average particle size:. 12.0μm, ZrO _2; volume resistivity 1.0 × ^{10 12} Ω · cm content 88% Niimi Sangyo Co., Ltd.)
-Non-conductive particles 7: GC # 1000
_{(D 50} average particle size:. 11.9μm, SiC; volume resistivity 1.0 × 10 of ⁶ Omega · cm content of 92% manufactured by Fujimi Incorporated)
-Conductive filler: Composite fine particles (dendrite-like fine particles in which 10 parts by weight of silver is coated on 100 parts by weight of copper in the core) D ₅₀ Average particle size: 11.0 μm Made by Fukuda Metal Foil Powder Industry Co., Ltd. ・ Carrier material Copper foil with A1: Electrolytic copper foil with a copper carrier having a thickness of 2.5 μm. The 30 μmφ opening is formed by etching so that the opening ratio is 6.5%.

<Manufacturing of adhesive layer 1>
In terms of solid content, 100 parts of binder resin, 20 parts of epoxy compound, and 0.5 part of aziridine compound are placed in a container, and a mixed solvent (toluene: isopropyl alcohol = 2: 1 (toluene: isopropyl alcohol = 2: 1) is charged so that the non-volatile content concentration becomes 40%. Weight ratio)) was added and stirred with a disper for 10 minutes to obtain a resin composition.

The resin composition was coated on a peelable sheet with a bar coater so that the drying thickness was 6.0 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an adhesive layer 1.

<Manufacturing of adhesive layers 2 to 6>
Adhesive layers 2 to 6 were obtained by carrying out the same method as that for the adhesive layer 1 except that the amount of the epoxy compound added was changed as shown in Table 1.

<Manufacturing of adhesive layer 7>
In terms of solid content, 100 parts of binder resin 1, 80 parts of conductive filler, 20 parts of epoxy compound, 0.5 part of aziridine compound are charged in a container, and a mixed solvent (toluene:) is prepared so that the non-volatile content concentration becomes 40%. Isopropyl alcohol = 2: 1 (weight ratio)) was added and stirred with a disper for 10 minutes to obtain a resin composition.

The resin composition was coated on a peelable sheet with a bar coater so that the drying thickness was 6 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an adhesive layer 7.

[Example 1]
In terms of solid content, 100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 were added, and the mixture was stirred with a disper for 10 minutes to obtain the resin composition 1. rice field. The obtained resin composition 1 is applied to a peelable sheet (thickness 50 μm) using a bar coater so that the dry thickness is 11 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain the protective layer 1. Formed.

Next, a copper plating layer (2.5 μm), which is a metal layer, was formed on the exposed surface of the protective layer 1 of the obtained “releaseable sheet / protective layer 1”. The copper plating layer was formed by an electrolytic plating method, and the electrolytic solution used was copper sulfate, and a current was applied at 25 ° C. for 7 minutes.

By adhering the adhesive layer 1 to the formed metal layer surface, an electromagnetic wave shield sheet composed of "peeling sheet / protective layer 1 / metal layer (plating layer) / adhesive layer 1 / peelable sheet" was obtained. The metal layer and the adhesive layer 1 were bonded together by a thermal laminator at a temperature of 90 ° C. and a pressure of 3 kgf / cm ^2.

[Examples 2 to 19 and 23 to 27, Comparative Examples 1 to 2]
As shown in Tables 1 and 2, Examples 2 to 19 and 23 to 27, Comparative Examples, were carried out in the same manner as in Example 1 except that the types of the adhesive layer, the metal layer, and the protective layer were changed. Electromagnetic wave shield sheets 1 and 2 were obtained, respectively. When the 60 ° mirror gloss on the surface of the metal layer after forming the copper plating layer was different from the target value, the 60 ° mirror gloss was adjusted by appropriately polishing or roughening the surface by buffing.

[Example 20]
In terms of solid content, 100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 were added, and the mixture was stirred with a disper for 10 minutes to obtain the resin composition 1. rice field. The obtained resin composition 1 is coated on a copper foil A1 with a carrier material using a bar coater so that the drying thickness is 11 μm, and dried in an electric oven at 100 ° C. for 2 minutes to form a protective layer 11. Then, a peelable sheet was attached to the protective layer 11.

Next, the carrier material of the copper foil A1 with the carrier material was peeled off, the copper foil surface was buffed, and the 60 ° mirror glossiness of the copper foil surface was adjusted to the values shown in Table 2 to obtain a metal layer. By adhering the adhesive layer 1 to the surface of the metal layer after polishing, an electromagnetic wave shield sheet composed of "peeling sheet / protective layer 1 / metal layer (copper foil) / adhesive layer 1 / peelable sheet" was obtained. .. The metal layer and the adhesive layer 1 were bonded together by a thermal laminator at a temperature of 90 ° C. and a pressure of 3 kgf / cm ^2.

[Example 21]
In terms of solid content, 100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 were added, and the mixture was stirred with a disper for 10 minutes to obtain the resin composition 1. rice field. The obtained resin composition 1 is applied to a peelable sheet (thickness 50 μm) using a bar coater so that the dry thickness is 11 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain the protective layer 1. Formed.

Next, a copper sputtering treatment was performed on the exposed surface of the protective layer 1 of the obtained "peeling sheet / protective layer 1" to form a metal layer.

By adhering the adhesive layer 1 to the formed metal layer surface, an electromagnetic wave shield sheet composed of "peeling sheet / protective layer 1 / metal layer (spatter layer) / adhesive layer 1 / peelable sheet" was obtained. The metal layer and the adhesive layer 1 were bonded together by a thermal laminator at a temperature of 90 ° C. and a pressure of 3 kgf / cm ^2.

[Example 22]
In terms of solid content, 100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 were added, and the mixture was stirred with a disper for 10 minutes to obtain the resin composition 1. rice field. The obtained resin composition 1 is applied to a peelable sheet (thickness 50 μm) using a bar coater so that the dry thickness is 11 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain the protective layer 1. Formed.

Next, a copper vapor deposition treatment was performed on the exposed surface of the protective layer 1 of the obtained "peeling sheet / protective layer 1" to form a metal layer.

By adhering the adhesive layer 1 to the formed metal layer surface, an electromagnetic wave shield sheet composed of "peeling sheet / protective layer 1 / metal layer (deposited layer) / adhesive layer 1 / peelable sheet" was obtained. The metal layer and the adhesive layer 1 were bonded together by a thermal laminator at a temperature of 90 ° C. and a pressure of 3 kgf / cm ^2.

With respect to the obtained electromagnetic wave shield sheet, the thickness of each layer and the 60 ° mirror glossiness of the metal layer were measured by the following methods.

<< Measurement of each layer thickness >>
The thicknesses of the adhesive layer, the metal layer, and the protective layer of the electromagnetic wave shield sheet were measured by the following methods.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, the exposed adhesive layer and the polyimide film (“Kapton 200EN” manufactured by Toray DuPont Co., Ltd.) were laminated, and heat-pressed at 2 MPa and 170 ° C. for 30 minutes. .. 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 into a slide glass, and an electromagnetic wave shield sheet is adhered to the slide glass / electromagnetic wave shield. A laminate having a sheet / polyimide film composition 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 an electromagnetic wave shield sheet after hot pressing.

The cross section of the obtained measurement sample is shown with a laser microscope (manufactured by KEYENCE, VK-X10).
Using 0), the thickness of each layer was measured from the observed enlarged image. The magnification was 500 to 2000 times. The thickness T of the protective layer is defined as the perpendicular distance passing through one point of the protective layer closest to the adhesive layer, starting from the outermost surface of the protective layer of the electromagnetic wave shield sheet in the enlarged image.

《Measurement of 60 ° mirror gloss》
The 60 ° mirror glossiness of the metal layer of the electromagnetic wave shield sheet was measured by the following method.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, and the exposed adhesive layer was washed away with acetone to expose the metal layer. The adhesive layer was removed, and the surface of the exposed metal layer was measured for mirror gloss using a gloss meter (micro-try gloss manufactured by BYK), and the measured value at a measurement angle of 60 ° was measured for 60 ° mirror gloss. And said.

<< Measurement of Rz >>
The maximum height roughness Rz of the metal layer of the electromagnetic wave shield sheet was measured by the following method.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, and the exposed adhesive layer was washed away with acetone to expose the metal layer. The adhesive layer was removed, and the surface of the exposed metal layer was subjected to measurement data acquisition using a laser microscope (VK-X100 manufactured by KEYENCE CORPORATION) (objective lens magnification 50 times). The acquired measurement data was taken into analysis software (analysis application "VK-H1XA", manufactured by KEYENCE CORPORATION), and line roughness measurement was performed (cutoff conditions were λ _S ; 2.5 μm, λ _C ; 0.8 mm. The measurement range is 0.25 mm). In one measurement field of view, measurement is performed in five regions, and similar measurement is performed in five fields of view by changing the measurement field of view. The average value of the measurement data in a total of 25 regions was defined as the maximum height roughness Rz of the metal layer. For the metal layer having an opening on the surface, the opening was excluded from the measurement range when performing the line roughness measurement.

The obtained electromagnetic wave shield sheet was evaluated for cleaning resistance, circuit connection stability, folding resistance, and insulation by the following methods.

<Washing resistance>
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet with a width of 40 mm and a length of 40 mm is peeled off, and the exposed adhesive layer and the polyimide film with a width of 50 mm and a length of 50 mm (“Kapton 500H” manufactured by Toray DuPont) are placed at 170 ° C. , 2.0 MPa, 30 minutes, and heat-cured to obtain a sample. A cross-cut guide was used on the protective layer side of the electromagnetic wave shield sheet of the obtained sample according to JIS K5400, and 100 grids with an interval of 1 mm were prepared. After that, it is immersed in the solvent type cleaning liquid "Zestron FA +" (manufactured by Zestron) for 20 minutes, set to 100% output using the ultrasonic cleaner "UT-205HS" (manufactured by SHARP), and ultrasonically treated for 2 minutes. After that, the sample was taken out, washed with distilled water, and then dried. Change the cleaning solution to "10 wt% hydrochloric acid aqueous solution", "10 wt% sodium hydroxide aqueous solution", "Pine Alpha ST-100S (manufactured by Arakawa Chemical Co., Ltd.)" Sound-cleaning treatment was performed. Adhesive tape was strongly crimped to the grid of each test piece, and the edges of the tape were peeled off at a stretch at an angle of 45 °.

⊚: The number of peeled grids is less than 5 for each test piece. Very good.
〇: For each test piece, the number of peeled grids is 5 or more and less than 15. Good.
Δ: In any of the test pieces, the number of peeled grids is 15 or more and less than 35. Practical use is possible.
X: In any of the test pieces, the number of peeled grids is 35 or more. Not practical.

<Circuit connection stability>
The circuit connection stability was evaluated by measuring the connection resistance value through the small aperture via. The specific method of evaluation is shown below.
An electromagnetic wave shield sheet was prepared to have a width of 20 mm and a length of 50 mm and used as a sample 25. Explaining by showing the plan views of FIGS. 6 (1) and 6 (4), the peelable sheet was peeled off from the sample 25, and the exposed adhesive layer 25b was placed on a separately prepared flexible printed wiring board (polyimide film 21 having a thickness of 25 μm). A copper foil circuit 22A having a thickness of 18 μm and a copper foil circuit 22B that are not electrically connected to each other are formed, and a thickness of 37.5 μm and a diameter of 1.1 mm (via area is 1) are formed on the copper foil circuit 22A. A wiring board on which a polyimide coverlay 23 with an adhesive having a circular via 24 of 0.0 mm ² ) is laminated) is crimped under the conditions of 170 ° C., 2 MPa, and 30 minutes, and the adhesive layer 25b and the protective layer 25a of the electromagnetic wave shield sheet are pressed. Was cured to obtain a sample. Next, the peelable sheet on the protective layer 25a side of the sample was removed, and the initial connection resistance value between 22A and 22B shown in the plan view of FIG. Measured using. 6 (2) is a cross-sectional view taken along the line DD'of FIG. 6 (1), and FIG. 6 (3) is a cross-sectional view taken along the line CC'of FIG. 6 (1). Similarly, FIG. 6 (5) is a cross-sectional view taken along the line DD'of FIG. 6 (4), and FIG. 6 (6) is a cross-sectional view taken along the line CC'of FIG. 6 (4).
The sample was placed in a high temperature and high humidity device (“PHP-2J”, manufactured by ESPEC CORPORATION), and the sample was exposed for 500 hours under exposure conditions of temperature: 85 ° C. and relative humidity: 85%. After that, the connection resistance value of the sample was measured in the same manner as in the initial stage.
The evaluation criteria for circuit connection stability are as follows.

⊚: (connection resistance value after exposure) / (initial connection resistance value) is less than 1.5 Very good.
◯: (connection resistance value after exposure) / (initial connection resistance value) is 1.5 or more and less than 3.0 Good.
Δ: (connection resistance value after exposure) / (initial connection resistance value) is 3.0 or more and less than 5.0 Practical use is possible. ×: (connection resistance value after exposure) / (initial connection resistance value) is 5.0 or more, not practical.

<Fold resistance>
The peelable sheet of the adhesive layer of the electromagnetic wave shield sheet with a width of 20 mm and a length of 100 mm is peeled off, and the exposed adhesive layer and the polyimide film with a width of 20 mm and a length of 100 mm (“Kapton 500H” manufactured by Toray DuPont) are placed at 150 ° C. A sample was obtained by crimping under the conditions of 2.0 MPa for 30 minutes and thermosetting. The electromagnetic wave shield sheet of the obtained sample 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 again 10. It was placed for 2 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 microscope "VHX-900" manufactured by KEYENCE CORPORATION, and the number of times the electromagnetic wave shield sheet 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 and less than 7 times. Practical use is possible.
X: Less than 2 times. Not practical.

<Insulation>
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet with a width of 50 mm and a length of 100 mm is peeled off, and the exposed adhesive layer and the polyimide film with a width of 70 mm and a length of 120 mm (“Kapton 300H” manufactured by Toray DuPont) are placed at 170 ° C. , 2.0 MPa, 30 minutes, and heat-cured to obtain a test piece. The surface resistance value of the insulating layer of the test piece was measured using a ring probe URS of "High Resta UP MCP-HT800" manufactured by Mitsubishi Chemical Analytech. The evaluation criteria are as follows.

◎: 1.0 × 10 ⁹ Ω / □ or more Very good.
◯: 1.0 × 10 ⁷ Ω / □ or more, ^{less than 1.0 × 10 9} Ω / □ Good.
Δ: 1.0 × 10 ⁵ Ω / □ or more, ^{less than 1.0 × 10 7} Ω / □ Practical use is possible.
×: 1.0 × 10 ^{Less than 5} Ω / □ Not practical.

1 Adhesive layer 2 Metal layer 3 Protective layer 4 Non-conductive particles 5 Ground wiring 6 Signal wiring 7 Electromagnetic shield wiring circuit board 8 Cover coat layer 9 Insulation base material 10 Electromagnetic shield sheet 11 Via 12 Electromagnetic shield layer 13 Thermal press plate 14 Removable sheet 21 Polyimide film 22 Copper foil circuit 23 Polyimide coverlay with adhesive 24 Circular via 25 Electromagnetic wave shield layer

Claims (5)

It has a laminate having an adhesive layer, a metal layer, and a protective layer in this order.
The surface of the metal layer in contact with the adhesive layer has a 60 ° mirror glossiness of 0 to 500 determined in accordance with ISO 7668, and X represented by the formula (1) is less than 1.0. Electromagnetic wave shield sheet featuring.
Equation (1)
X = Rz / T
(Rz is the maximum height roughness of the metal layer obtained in accordance with JIS B0601 and T is the thickness of the protective layer.) The electromagnetic wave shield sheet according to claim 1, wherein the thickness of the metal layer is 0.3 to 10 μm. The electromagnetic wave shield sheet according to claim 1 or 2, wherein the protective layer contains non-conductive particles having a volume resistivity of 1.0 × 10 ^{10 Ω · cm or more.} The electromagnetic wave shield sheet according to any one of claims 1 to 3, wherein the protective layer contains a binder resin having a weight average molecular weight of 10,000 or more. An electromagnetic wave shielding property comprising an electromagnetic wave shielding layer formed from the electromagnetic wave shielding sheet according to any one of claims 1 to 4, a cover coat layer, and a signal wiring and a wiring board having an insulating base material. Circuit board.

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