TWI734574B - Electromagnetic wave shielding sheet and electromagnetic wave shielding wiring circuit board - Google Patents

Abstract

The present invention provides an electromagnetic wave shielding sheet having reflow resistance and excellent cold-heat cycle reliability, excellent high-frequency shielding properties and good bending resistance, and a wiring circuit board using the electromagnetic wave shielding sheet. It is solved by an electromagnetic wave shielding sheet, the electromagnetic wave shielding sheet is characterized in that it includes a conductive adhesive layer, a metal layer and a protective layer, and the interface of the metal layer and the conductive adhesive layer is connected to the metal layer Among them, the 60° specular gloss determined in accordance with ISO 7668 is 10 to 800, and the metal layer has a plurality of openings, and the opening ratio is 0.10% to 20%.

Description

Electromagnetic wave shielding sheet and electromagnetic wave shielding wiring circuit board

The present invention relates to an electromagnetic wave shielding sheet and an electromagnetic wave shielding wiring circuit board. For example, it relates to an electromagnetic wave shielding sheet suitable for use in joining with a part of a part that emits electromagnetic waves and uses an electromagnetic wave shielding sheet The electromagnetic wave shielding wiring circuit board.

Various electronic devices represented by mobile terminals, personal computers (PC), servers, etc. have built-in wiring circuit boards such as printed wiring boards. In order to prevent malfunctions caused by external magnetic fields or electric waves, and to reduce unnecessary radiation from electrical signals, electromagnetic wave shielding structures are provided on these printed circuit boards.

With the high-speed transmission of transmission signals, electromagnetic wave shielding sheets are also required to have electromagnetic wave shielding properties against high-frequency noise (hereinafter, high-frequency shielding properties) and reduce transmission loss in the high-frequency region (hereinafter, sometimes referred to as transmission characteristics) ). Patent Document 1 discloses a structure in which a metal layer having a thickness of 0.5 μm to 12 μm and an anisotropic conductive adhesive layer are provided in a laminated state. It is also described that according to this configuration, electric field waves, magnetic field waves, and electromagnetic waves traveling from one side to the other side of the electromagnetic wave shielding sheet can be well shielded, and transmission loss can be reduced. [Prior Art Literature]

[Patent Literature] [Patent Document 1] International Publication No. 2013/077108 [Patent Document 2] Japanese Patent Laid-Open No. 2013-168643

[The problem to be solved by the invention] In recent years, in electronic devices typified by mobile phones, with the increase in high-speed transmission of transmission signals, electromagnetic wave shielding sheets on the wiring circuit boards incorporated in these have also been required to have high-frequency shielding properties and transmission characteristics. Therefore, it has been considered that it is preferable to use a metal layer having a thickness of 0.5 μm to 12 μm as described in Patent Document 1 in the conductive layer of the electromagnetic wave shielding sheet. However, the electromagnetic wave shielding printed circuit board formed by attaching an electromagnetic wave shielding sheet with a metal layer to the printed circuit board has the following problems (hereinafter, sometimes referred to as reflow resistance): when performing heat treatment such as reflow soldering , Due to the volatile components generated from the inside of the wiring circuit board, floating between the layers occurs, and poor appearance and poor connection due to foaming and the like. In response to this problem, for example, in Patent Document 2, a metal foil having a plurality of pinholes in the metal thin film layer is used to allow volatile components to pass through the pinholes of the metal thin film layer, thereby suppressing floating or foaming between layers. Moreover, the thicker the metal layer of the electromagnetic wave shielding sheet is, the higher the shielding performance is, on the other hand, the higher the repulsive force. As a result, when the shielding printed circuit formed by attaching the electromagnetic wave shielding sheet to the printed circuit is assembled into the frame, the occurrence of cracks in the bent portion, poor appearance, poor insulation, and occurrence of noise leakage become problems. On the other hand, as electronic devices such as smart phones and tablet terminals have become popular worldwide in recent years, reliability under a wide range of temperature conditions is required. When the printed circuit boards provided with electromagnetic wave shielding sheets of Patent Document 1 and Patent Document 2 are exposed to extreme temperature changes, problems such as peeling from the printed circuit board or interruption of the connection with the ground circuit occur (hereinafter, the reliability of cooling and heating cycles).

The present invention is made in view of the background, and its object is to provide an electromagnetic wave shielding sheet having reflow resistance and excellent cold-heat cycle reliability, excellent high-frequency shielding properties and good bending resistance, and using the The wiring circuit board of the electromagnetic wave shielding sheet. [Technical means to solve the problem]

The inventors conducted active studies and found that the problems of the present invention can be solved in the following embodiments, thereby completing the present invention. That is, the electromagnetic wave shielding sheet of the present invention is characterized in that it has a laminate having a conductive adhesive layer, a metal layer, and a protective layer in this order. The 60° specular gloss determined by the International Organization for Standardization (ISO) 7668 is 10 to 800, the metal layer has a plurality of openings, and the opening ratio is 0.10% to 20%. [Effects of the invention]

According to the present invention, the following excellent effects are achieved, namely: it is possible to provide an excellent reflow resistance, excellent high-frequency shielding performance even when used in a high-frequency transmission circuit, and good bending resistance Electromagnetic wave shielding sheet and electromagnetic wave shielding wiring circuit board with high connection reliability even after exposure to cold and heat cycles.

Hereinafter, an example of an embodiment to which the present invention is applied will be described. In addition, the size or ratio of each member in the following figures is for convenience of description, and is not limited to this. In addition, in this specification, the description of "arbitrary number A to arbitrary number B" means that the number A is included as a lower limit and the number B is included as an upper limit in the above-mentioned range. Moreover, the "sheet" in this manual includes not only the "sheet" defined in the Japanese Industrial Standards (JIS), but also the "film". In addition, the numerical value specified in this specification is a value calculated|required by the method disclosed in an embodiment or an Example.

＜Electromagnetic wave shielding sheet＞ The electromagnetic wave shielding sheet of the present invention has a laminate having at least a conductive adhesive layer, a metal layer, and a protective layer in this order. FIG. 1 is a cross-sectional view illustrating an electromagnetic wave shield sheet 10 according to the embodiment. As shown in FIG. 1, the electromagnetic wave shielding sheet 10 has a laminate including a conductive adhesive layer a1, a metal layer a2, and a protective layer a3 in this order. The metal layer a2 is arranged between the conductive adhesive layer a1 and the protective layer a3. . The electromagnetic wave shielding sheet of the present invention is provided with a plurality of openings a4 and an opening ratio of 0.10% to 20%. The surface of the metal layer that is in contact with the conductive adhesive layer is 60% calculated in accordance with ISO 7668. °The metal layer has a mirror gloss of 10 to 800, so it can exhibit excellent transmission characteristics especially in wiring circuit boards that transmit high-frequency signals (for example, from 100 MHz to 50 GHz). Regarding the electromagnetic wave shielding sheet 10, for example, a printed circuit board as an adherend is bonded to a surface on the conductive adhesive layer a1 side to form an electromagnetic wave shielding layer, and an electromagnetic wave shielding printed circuit board is produced. That is, in the surface of the metal layer a2, the surface facing the signal wiring in the printed circuit board is the surface in close contact with the conductive adhesive layer a1.

[Loss tangent of laminated hardened material] Furthermore, the electromagnetic wave shielding sheet of the present invention preferably: a laminate having at least an electrically conductive adhesive layer, a metal layer, and a protective layer in this order is heat-pressed at 170°C for 30 minutes. The loss at 125°C The tangent is 0.10 or more. In this way, the reliability of the cooling and heating cycle can be further improved.

The laminated hardened product can be formed by hardening the electromagnetic wave shielding sheet by hot pressing at 170°C for 30 minutes. That is, it refers to a laminate including a conductive adhesive layer, a metal layer, a protective layer, and other functional layers, in which the layer having a hardening component is hardened.

The laminated hardened product is the one in which the peelable sheet is removed from the electromagnetic wave shielding sheet before or after the heat pressing, and the electromagnetic wave shielding sheet is laminated by heat pressing only one electromagnetic wave shielding sheet, or by laminating multiple electromagnetic wave shielding sheets using a laminator, etc. Any method of hot pressing can be obtained. That is, the laminated cured product is the same laminated constituent part of the electromagnetic wave shielding sheet as the electromagnetic wave shielding layer used for the electromagnetic wave shielding printed circuit board.

Specifically, for example, two electromagnetic wave shielding sheets are prepared, the peelable sheets on the conductive adhesive layer side of each are peeled off, and the exposed conductive adhesive layers are bonded to each other, and the process is performed at 170°C for 30 minutes By hot pressing, a laminate having at least a conductive adhesive layer, a metal layer, and a protective layer is thermally cured to form a laminate cured product.

The loss tangent of the laminate cured product is a value obtained by the following formula (3), and is an index of the ability to relax the stress generated when the electromagnetic wave shielding sheet is deformed. Numerical formula (3) (Loss tangent of laminated hardened material)= (Loss elastic coefficient of laminated hardened material E'')/(Storage elastic coefficient of laminated hardened material E') As an example, the dynamic viscoelastic curve of the laminated hardened product (Example 5) is shown in FIG. 5. By reading the loss elastic coefficient E" and the storage elastic coefficient E'at a certain temperature, and applying these values to the equation (3), the loss tangent at the corresponding temperature can be calculated. From the viewpoint of the reliability of the cooling and heating cycle, the laminate cured product preferably has a loss tangent at 125°C of 0.1 or more after hot pressing at 170°C for 30 minutes. If the laminated hardened product has a loss tangent at 125°C of 0.1 or more after hot pressing at 170°C for 30 minutes, the stress due to expansion during high-temperature exposure can be sufficiently alleviated. It is more preferable that the laminate cured product has a loss tangent at 125°C of 0.13 or more after hot pressing at 170°C for 30 minutes, and more preferably 0.15 or more.

The loss tangent of the laminated hardened product can be determined by changing the loss elastic coefficient E of any one of the conductive adhesive layer, the metal layer, the protective layer, and the other layers included in the laminated hardened product, or the loss elasticity coefficient of two or more layers. And storage elasticity coefficient E'to control. This is because by changing the loss elastic coefficient E'' and storage elastic coefficient E'of one or two or more layers included in the laminated hardened product, the loss elastic coefficient E'' and storage elastic coefficient E of the laminated hardened product 'Will change, so that the loss tangent of the laminated hardened material changes.

As an example of a method of changing the loss elastic coefficient E" and the storage elastic coefficient E'of one layer or two or more layers included in the laminated hardening substance, the hardening dose control in the protective layer can be cited. That is, by increasing or decreasing the hardening dose in the protective layer, the storage elastic coefficient E'of the protective layer increases or decreases. As a result, the storage elastic coefficient E'of the laminated hardened product increases or decreases, and the loss tangent of the laminated hardened product decreases or increases. The method for controlling the loss tangent of the laminated hardened product is not particularly limited. It can be used to change the type or blending ratio of thermoplastic resin or thermosetting resin and hardener, change the ratio of the thickness of each layer, change the type of metal layer, etc. Well-known method.

"Metal Layer" The metal layer of the present invention has a function of imparting high-frequency shielding properties to the electromagnetic wave shielding sheet. In the interface between the conductive adhesive layer and the metal layer, on the side where the metal layer and the conductive adhesive layer are in contact, the 60° specular gloss calculated in accordance with ISO 7668 is 10 to 800. By controlling the 60° mirror gloss in the range of 10 to 800, it is possible to balance the bending resistance and the reliability of the cold and heat cycle. The details of the 60° specular glossiness and the details of the effects obtained by controlling the 60° specular glossiness will be described later. Furthermore, the metal layer of the present invention has a plurality of openings, and the opening ratio is 0.10% to 20%. Thereby, the reflow resistance is improved, and it is possible to suppress the occurrence of appearance defects and the decrease in connection reliability.

[60°mirror gloss] The 60° specular gloss is a parameter standardized in ISO 7668, which represents the degree of gloss on the surface of the measured object. Specular gloss can be measured by irradiating light (incident light) on the surface of the object to be measured at a certain angle of incidence, using a detector to detect the reflected light (specular reflection light) at a certain angle, and digitizing it . The incident light irradiated to the surface of the object to be measured is reflected, transmitted, or absorbed when it reaches the surface of the object to be measured. In addition, there are specular reflection and diffuse reflection in reflection, and light reflected at the same angle (reflection angle) as the incident angle is specular reflection light, which is the light detected in the specular gloss measurement. The 60° specular gloss is the value measured when the incident angle and reflection angle are 60°. When the surface of the measurement object is a metal layer, most of the incident light will be reflected. The ratio of the reflected light to specular reflection and diffuse reflection is determined by the roughness of the surface of the metal layer. Fig. 2 shows cross-sectional views of two measurement object surfaces with different roughnesses. As shown in (i) of FIG. 2, on the surface of the measurement target with low roughness, the proportion of specular reflection light is large, while diffuse reflection light decreases, and the value of specular gloss increases. On the other hand, as shown in (ii) of FIG. 2, the ratio of specular reflection light is small on the surface of the measurement target with a large degree of roughness. On the other hand, the diffuse reflection light increases, and the value of the specular gloss decreases. That is, the mirror gloss can be used as an index for estimating the roughness of the surface of the measurement object.

In addition, the value of the 60° specular gloss of the metal layer does not change due to the steps of forming the electromagnetic wave shielding layer such as heating and pressing. Therefore, the 60° specular gloss of the surface of the metal layer in contact with the conductive adhesive layer in the electromagnetic wave shielding layer is also 10 to 800.

When the electromagnetic wave shielding sheet and the laminated hardened product or electromagnetic wave shielding wiring circuit board formed by curing the electromagnetic wave shielding sheet are bent, the metal layer included is also bent together. At this time, when the unevenness of the surface of the metal layer is steep, cracks in the metal layer may be induced. That is, when the metal layer is bent, stress is concentrated on the concave and convex portions, and cracks are generated in the metal layer from the concave portion as a starting point. Cracks in the metal layer cause problems such as a decrease in shielding properties due to poor conductivity of the metal layer, or poor appearance due to the end of the crack piercing other layers. Therefore, from the viewpoint of bending resistance, the 60° specular gloss of the surface of the metal layer in contact with the conductive adhesive layer is preferably 10 or more, more preferably 20 or more, and even more preferably 40 or more.

On the other hand, from the viewpoint of the reliability of the cooling and heating cycle, the result of active research is that by setting the 60° specular gloss of the metal layer in the range of 10 to 800, the reliability of the cooling and heating cycle is improved. It is believed that this is because even when the shape of the conductive adhesive layer changes due to the expansion and contraction of the conductive adhesive layer during the cooling and heating cycle, the unevenness formed on the surface of the metal layer is appropriately rough, and the conductive adhesive layer is maintained The conductive filler is in contact with the metal layer, thereby suppressing the deterioration of the connection resistance. As a result of the research, it is more preferable to set the 60° specular gloss of the metal layer to the range of 20 to 750, and still more preferably to the range of 40 to 700.

[Method of controlling 60° mirror glossiness] The method of controlling the 60° specular gloss of the metal layer surface includes, for example, a method of attaching roughened particles to the surface of a copper foil to form a roughened surface, and polishing described in Japanese Patent Laid-Open No. 2017-13473 The method of buff polishing the metal surface, the method of polishing the metal surface using abrasive cloth, the method of forming a metal layer on the carrier with the desired unevenness by plating or other methods to transfer the unevenness of the carrier material, by compression The shotblast method in which air blows the abrasive onto the metal surface. The method of controlling the 60° specular gloss on the surface of the metal layer is not limited to the exemplified method, and a conventionally known method can be applied.

[The thickness of the metal layer] The thickness of the metal layer is preferably 0.3 μm or more. By setting the thickness of the metal layer to 0.3 μm or more, it is possible to suppress transmission of the wavelength of electromagnetic noise generated from the printed circuit board, thereby exhibiting sufficient high-frequency shielding properties and suppressing cracks in the metal layer during bending. The thickness of the metal layer is more preferably 0.5 μm or more. On the other hand, the thickness of the metal layer is preferably 5.0 μm or less. By setting the thickness of the metal layer to 5.0 μm or less, the loss tangent of the laminated hardened product can be increased, and the reliability of the cooling and heating cycle can be improved. The upper limit of the thickness of the metal layer is more preferably 3.5 μm or less.

[Composition of the metal layer] For the metal layer, for example, a metal foil, a metal vapor-deposited film, or a metal-plated film can be used. The metal used in the metal foil is preferably, for example, a conductive metal such as aluminum, copper, silver, gold, and the like, and one type of metal or an alloy of multiple types of metals may be used. In terms of high-frequency shielding properties and cost, copper, silver, and aluminum are more preferable, and copper is still more preferable. For copper, for example, rolled copper foil or electrolytic copper foil is preferably used. As the metal used in the metal vapor-deposition film and the metal-plated film, for example, an alloy of one or more metals of conductive metals such as aluminum, copper, silver, and gold is preferably used, and copper and silver are more preferable. One or both surfaces of metal foil, metal vapor-deposited film, and metal-plated film can be coated with metal or organic matter such as rust inhibitor.

[Opening] The metal layer has a plurality of openings with an opening ratio of 0.10% to 20%. By having the opening, the reflow resistance is improved. By having an opening, when the electromagnetic wave shielding printed circuit board is reflowed, the volatile components contained in the polyimide film or cover layer adhesive of the printed circuit board can escape to the outside, thereby suppressing the cover The appearance of poor appearance caused by the peeling of the interface between the layer adhesive and the electromagnetic wave shielding sheet.

The shape of the opening viewed from the surface of the metal layer can be formed into various shapes as necessary, such as a perfect circle, an ellipse, a quadrilateral, a polygon, a star, a trapezoid, a branch, and the like. From the viewpoint of manufacturing cost and ensuring the strength and 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 in the range of 0.10% to 20%, which can be calculated by the following formula (2). Numerical formula (2) (Aperture ratio [%])=(Area of opening per unit area)/(Area of opening per unit area+Area of non-opening per unit area)×100

By setting the aperture ratio to 0.10% or more, the volatile components during the reflow process can be sufficiently escaped, and the occurrence of appearance defects and the decrease in connection reliability caused by the interface peeling of the cover layer adhesive and the electromagnetic wave shielding sheet can be suppressed. Therefore preferred. On the other hand, by setting the aperture ratio to 20% or less, the amount of electromagnetic wave noise passing through the aperture can be reduced and the shielding properties can be improved, which is preferable. The range of the aperture ratio that balances reflow resistance and high-frequency shielding properties at a high level is more preferably 0.30% to 15%, and still more preferably 0.50% to 6.5%.

In particular, in the electromagnetic wave shielding sheet where the 60° specular gloss of the metal layer is in the range of 700 or more and the interface with the conductive adhesive layer is smooth, the adhesion between the metal layer and the conductive adhesive layer is weak. During the soldering process, the volatile components swell at the interface between the metal layer and the conductive adhesive layer, resulting in poor appearance such as delamination or floating, but by setting the aperture ratio to 0.10% or more, preferably 0.50% or more , Can make the volatile components escape sufficiently, which can further suppress the occurrence of delamination or floating between layers.

The aperture ratio can be measured, for example, by using a laser microscope and a scanning electron microscope (Scanning Electron Microscope, SEM) to vertically magnify an image obtained by 500 to 2000 times from the surface direction of the metal layer. , Binarize the opening and the non-opening, and use the number of pixels of the binarized color per unit area as the respective areas.

The average area of one opening is preferably 0.7 μm ² to 5000 μm ² . It is more preferably 10 μm ² to 4000 μm ² , and still more preferably 20 μm ² to 2000 μm ² . By setting the opening area to 0.7 μm ² or more, the adhesion between the protective layer and the conductive adhesive layer becomes better, and the reflow resistance becomes more excellent. By setting the area of the opening to 5000 μm ² or less, it is possible to make it excellent in high electromagnetic wave shielding properties, which is therefore preferable.

The number of openings is preferably 100 openings/cm ² to 200,000 ^{openings/cm 2} . More preferably, it is 1,000 pieces/cm ² to 150,000 pieces/cm ² , and still more preferably 1,000 pieces/cm ² to 20,000 pieces/cm ² . By setting the number of openings to 100/cm ² or more, it is easy to efficiently discharge volatile components to the outside, and therefore the reflow resistance can be further improved. By setting the number of openings to 200,000/cm ² or less, high electromagnetic wave shielding properties can be ensured, which is preferable.

[Method for manufacturing metal layer with opening] The method for manufacturing the metal layer with openings can be a conventionally known method, and it can be applied to a method of forming a patterned resist layer on a metal foil and etching the metal foil to form an opening (i), using screen printing to define The method of printing the conductive paste with the pattern (ii), the screen printing of the primer (Anchor Agent) with a predetermined pattern, and the method of metal plating only on the printed surface of the primer (iii), and Japan The manufacturing method (iv) described in Japanese Patent Laid-Open No. 2015-63730, etc. That is, pattern printing of water-soluble or solvent-soluble ink is performed on the support, a metal vapor-deposited film is formed on the surface, and the pattern is removed. By forming a mold release layer on the surface and performing electrolytic plating, a metal layer with an opening with a carrier material can be obtained. Among these, the opening forming method (i) of forming a patterned resist layer and etching the metal foil can precisely control the shape of the opening, and therefore is preferable. However, the manufacturing method of the metal layer is not limited to the etching method (i), and other methods may be used as long as the shape of the opening can be controlled.

"Conductive Adhesive Layer" The conductive adhesive layer can be formed using a conductive resin composition. The conductive resin composition includes a binder resin and a conductive filler. As the binder resin, any one of a thermoplastic resin, a thermosetting resin, and a curing agent can be used. The conductive adhesive layer may use either an isotropic conductive adhesive layer or an anisotropic conductive adhesive layer. The isotropic conductive adhesive layer has conductivity in the vertical and horizontal directions when the electromagnetic wave shielding sheet is placed horizontally. In addition, the anisotropic conductive adhesive layer has conductivity only in the vertical direction when the electromagnetic wave shielding sheet is placed horizontally. The conductive adhesive layer may be either isotropic conductivity or anisotropic conductivity. In the case of anisotropic conductivity, cost reduction is possible, which is preferable.

[Thermoplastic resin] Examples of thermoplastic resins include polyolefin resins, vinyl resins, styrene-acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, and polyurethanes. Ester resin, polyester resin, polycarbonate resin, polyimide resin, liquid crystal polymer, fluororesin, etc. Although not particularly limited, from the viewpoint of transmission loss, materials with low dielectric constant and low dielectric loss tangent are preferable, and from the viewpoint of characteristic impedance, materials with low dielectric constant are preferable, such as liquid crystal polymerization. Materials or fluorine-based resins, etc. The thermoplastic resin can be used alone or in combination of two or more kinds.

[Thermosetting resin] The thermosetting resin is a resin having a plurality of functional groups capable of reacting with a curing agent. Examples of functional groups include hydroxyl groups, phenolic hydroxyl groups, methoxymethyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazinyl groups, aziridinyl groups, thiol groups, Isocyanate group, blocked isocyanate group, blocked carboxyl group, silanol group, etc. Examples of thermosetting resins include acrylic resins, maleic acid resins, polybutadiene resins, polyester resins, polyurethane resins, polyurethane urea resins, epoxy resins, and oxetane resins. Alkyl resin, phenoxy resin, polyimide resin, polyimide resin, polyimide resin, phenolic resin, alkyd resin, amino resin, polylactic acid resin, oxazoline resin, benzoxan Known resins such as oxazine resin, silicone resin, and fluororesin. The thermosetting resin can be used singly or in combination of two or more kinds.

Among these, in terms of reflow resistance, polyurethane resins, polyurethane urea resins, polyester resins, epoxy resins, phenoxy resins, polyimide resins, and polyamide resins are preferred. Amine resin, polyamide imide resin.

[hardener] The curing agent has a plurality of functional groups that can react 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 organometallic compounds. The hardener can be used alone or in combination of two or more kinds.

Regarding the curing agent, it is preferable to include 1 to 50 parts by mass of various curing agents with respect to 100 parts by mass of the thermosetting resin, more preferably 3 to 40 parts by mass, and still more preferably 3 to 30 parts by mass.

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

[Conductive filler] The conductive filler has a function of imparting conductivity to the conductive adhesive layer. Among the conductive fillers, as the raw material, for example, conductive metals such as gold, platinum, silver, copper, and nickel, and their alloys, and conductive polymer particles are preferred. In terms of price and conductivity, silver is more preferred. . Furthermore, from the viewpoint of cost reduction, it is also preferable to use metal or resin as a core body instead of fine particles of a single raw material and have a coating layer covering the surface of the core body. Here, the core body is preferably appropriately selected from inexpensive nickel, silicon dioxide, copper and alloys thereof, and resins. The coating layer is preferably a conductive metal or a conductive polymer. Examples of conductive metals include gold, platinum, silver, nickel, manganese, and indium, and alloys thereof. Furthermore, the conductive polymer includes polyaniline, polyacetylene, and the like. Among these, in terms of price and conductivity, silver is preferred.

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

The average particle diameter of the conductive filler is the D ₅₀ average particle diameter, and from the viewpoint of sufficiently ensuring conductivity, it is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. By setting the D ₅₀ average particle size of the conductive filler to be 2 μm or more, even in the case of expansion of the conductive adhesive layer during the thermal cycle test, the conductive fillers are sufficiently in contact with each other, and the conduction path can be ensured. On the other hand, from the viewpoint of achieving both the thickness of the conductive adhesive layer, the thickness is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. By setting the _{average particle size of D 50} to 30 μm or less, it is possible to suppress the phenomenon that the conductive filler pierces the protective layer during bending. The _{average particle diameter of D 50} can be determined by a laser diffraction/scattering particle size distribution measuring device or the like.

The content of the conductive filler in the conductive adhesive layer is preferably 35% by mass to 90% by mass, more preferably 39% by mass to 70% by mass, and still more preferably 40% by mass to 65% by mass. By setting it as 35% by mass or more, the connection between the conductive adhesive layer and the ground wiring becomes good, and therefore the high-frequency shielding properties and the reliability of the cooling and heating cycle are improved. On the other hand, by setting it as 90% by mass or less, reflow resistance and bending resistance are improved.

For the purpose of improving the desired physical properties or imparting functions, the conductive resin composition can be additionally formulated with silane coupling agents, rust inhibitors, reducing agents, antioxidants, pigments, dyes, adhesive imparting resins, plasticizers, and ultraviolet absorbers. As optional ingredients, such as antifoaming agents, leveling regulators, fillers, flame retardants, etc. For example, carbon particles may be added for the purpose of adjusting the viscoelasticity of the conductive adhesive layer. Examples of carbon particles include carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

The conductive resin composition can be obtained by mixing and stirring the materials described so far. For stirring, for example, a known stirring device such as a dispermat and a homogenizer can be used.

A known method can be used for the preparation of the conductive adhesive layer. For example, a method of forming a conductive adhesive layer by coating a conductive resin composition on a peelable sheet and drying it, or extruding the conductive resin composition into an extruder using an extruder such as a T-die Flake to form.

For the coating method, for example, gravure coating method, kiss coating method, die coating method, lip coating method, chipped wheel coating method, doctor blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, etc. can be used. Well-known coating methods such as coating method and dip coating method. At the time of coating, it is preferable to perform a drying step. For the drying step, for example, a known drying device such as a hot air dryer and an infrared heater can be used.

The thickness of the conductive adhesive layer is preferably 2 μm to 30 μm, more preferably 3 μm to 15 μm, and still more preferably 4 μm to 9 μm. By setting the thickness in the range of 2 μm to 30 μm, the reliability of the cooling and heating cycle and the resistance to reflow soldering can be improved.

"The protective layer" The protective layer can be formed using a conventionally known resin composition. The resin composition may contain the thermoplastic resin or the thermosetting resin and the curing agent described in the conductive resin composition, and the optional components as required. In addition, the thermosetting resin and curing agent used in the protective layer and the conductive adhesive layer may be the same or different.

The resin composition can be obtained by the same method as the conductive resin composition.

In addition, the protective layer can also use a film formed by molding insulating resins such as polyester, polycarbonate, polyimide, polyimide, polyamide, polyphenylene sulfide, and polyether ether ketone.

The thickness of the protective layer is usually about 2 μm to 10 μm.

"Manufacturing Method of Electromagnetic Wave Shielding Sheet" A known method can be used for the manufacturing method of the electromagnetic wave shielding sheet. For example, the method (i) forming a conductive adhesive layer on a peelable sheet, and superimposing the conductive adhesive layer on an electrolytic copper foil with an opening with a carrier material (also referred to as a copper foil with a carrier material) After laminating the surface side of the electrolytic copper foil, the carrier material is peeled off. Then, the surface from which the carrier material is peeled and the protective layer separately formed on the peelable sheet are superimposed and laminated; method (ii) forming a protective layer on the peelable sheet, and superimposing the protective layer on the opening of the carrier material After the electrolytic copper foil is laminated on the electrolytic copper foil surface side, the carrier material is peeled off. Then, the surface from which the carrier material is peeled and the conductive adhesive layer separately formed on the peelable sheet are superimposed and laminated; method (iii) on the side of the electrolytic copper foil surface of the electrolytic copper foil with openings of the carrier material The resin composition is applied to form a protective layer, and the releasable sheet is bonded. After that, the carrier material is peeled off, and the conductive adhesive layer separately formed on the peelable sheet is superimposed and laminated; method (iv) forming a conductive adhesive layer on the peelable sheet, and overlaying the conductive adhesive layer on the tape carrier After laminating the electrolytic copper foil surface side of the copper foil of the material, the carrier material is peeled off. Then, the surface from which the carrier material is peeled and the protective layer separately formed on the peelable sheet are superimposed and laminated, and then an opening is formed on the electromagnetic wave shielding sheet with a needle-shaped jig; method (v) is formed on the peelable sheet The protective layer of is overlapped on the electrolytic copper foil surface side of the electrolytic copper foil with openings of the carrier material and laminated, and then the carrier material is peeled off. Then, a conductive adhesive layer is formed on the surface from which the carrier material is peeled; the method (vi) is to form a conductive adhesive layer on the peelable sheet, and the surface of the rolled copper foil with openings has a 60° mirror gloss After the surface of 10 to 800 is overlapped with the conductive adhesive layer and laminated, the other surface laminated with the conductive adhesive layer is overlapped with the protective layer separately formed on the peelable sheet and laminated; method (vii ) A protective layer is formed on the peelable sheet, and the other surface of the rolled copper foil with openings that has a 60° mirror gloss of 10 to 800 is overlapped with the conductive adhesive layer and laminated, and then the The other side laminated with the protective layer overlaps and laminates the conductive adhesive layer separately formed on the peelable sheet; method (viii) on the surface of the rolled copper foil with openings, 60° specular gloss is The other surface of the 10-800 surface is coated with a resin composition to form a protective layer, and a peelable sheet is bonded. After that, the other side is overlapped with the conductive adhesive layer separately formed on the peelable sheet and laminated; method (ix) on the surface of the rolled copper foil with openings, the 60° specular gloss is 10 to 800 The conductive resin composition is coated on the surface of the slab to form a conductive adhesive layer, and the peelable sheet is attached. After that, the other surface is overlapped with a protective layer separately formed on the peelable sheet and laminated; etc.

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

The electromagnetic wave shielding sheet of the present invention can be used for various applications that need to shield electromagnetic waves. For example, it goes without saying that flexible printed circuits can also be used for rigid printed circuits, Chip On Film (COF), Tape Automated Bonding (TAB), flexible connectors, liquid crystal displays, touch screens, etc. . In addition, it can also be used as a component for building materials such as the housing of a personal computer, the wall of building materials and window glass, and a member that blocks electromagnetic waves in vehicles, ships, and airplanes.

In the electromagnetic wave shielding sheet of the present invention, when a thermoplastic resin is used for the adhesive resin in the conductive adhesive layer, the thermoplastic resin contained is present in a solid state, and the thermoplastic resin is melted by hot pressing with the wiring circuit board And solidified again after cooling, and the desired bonding strength can be obtained.

In the electromagnetic wave shielding sheet of the present invention, when a thermosetting resin is used for the binder resin in the conductive adhesive layer, the thermosetting resin and curing agent contained in the sheet are present in an uncured state (stage B), and use It is hardened by hot pressing with the printed circuit board (C stage), and the desired bonding strength can be obtained. In addition, the uncured state includes a semi-cured state in which a part of the hardener is hardened.

In addition, in order to prevent the adhesion of foreign matter, the electromagnetic wave shielding sheet is usually stored in a state where the peelable sheet is attached to the conductive adhesive layer and the protective layer.

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

＜Electromagnetic wave shielding wiring circuit board＞ The electromagnetic wave shielding wiring circuit board includes an electromagnetic wave shielding layer formed of the electromagnetic wave shielding sheet of the present invention, a top coat, and a wiring circuit board including a circuit pattern having signal wiring and ground wiring, and an insulating base material. The wiring circuit board includes a circuit pattern having signal wiring and ground wiring on the surface of the insulating base material, and the signal wiring and the ground wiring are insulated and protected by forming on the wiring circuit board, so that at least a part of the ground wiring has a path The conductive adhesive layer of the electromagnetic wave shielding sheet is arranged on the surface coating, and then the electromagnetic wave shielding sheet is thermally pressed to make the conductive adhesive layer flow into the via and adhere to the ground wiring Then, an electromagnetic wave shielding wiring circuit board can be manufactured by this.

An example of the electromagnetic wave shielding printed circuit board of the present invention will be described with reference to FIG. 3. The electromagnetic wave shielding layer 12 includes a conductive adhesive layer a1, a metal layer a2, and a protective layer a3.

The top coat 8 is an insulating material that covers the signal wiring of the printed circuit board and protects it from the external environment. The top coat layer is preferably a polyimide film with a thermosetting adhesive, a thermosetting or ultraviolet curing type solder resist, or a photosensitive cover film. For fine processing, a photosensitive cover film is more preferable. In addition, the top coat layer is usually made of a known resin having heat resistance and flexibility, such as polyimide. The thickness of the top coat is usually about 10 μm to 100 μm.

The circuit pattern includes a ground wiring 5 that is grounded, and a signal wiring 6 that transmits electrical signals to electronic components. Both are usually formed by etching copper foil. The thickness of the circuit pattern is usually about 1 μm to 50 μm.

The insulating substrate 9 is a support for the circuit pattern, and is preferably a bendable plastic such as polyester, polycarbonate, polyimide, polyphenylene sulfide, liquid crystal polymer, and more preferably liquid crystal polymer and polyamide. amine. Among these, considering the use of a wiring circuit board for transmitting high-frequency signals, it is more preferable to use a liquid crystal polymer having a low relative permittivity and a low dielectric loss tangent. When the printed circuit board is a rigid circuit, the constituent material of the insulating base material is preferably glass epoxy. By including insulating base materials such as these, the printed circuit board obtains high heat resistance.

The hot pressing of the electromagnetic wave shielding sheet 10 and the printed circuit board is usually performed under the conditions of a temperature of about 150°C to 190°C, a pressure of about 1 MPa to 3 MPa, and a time of about 1 minute to 60 minutes. By hot pressing, the conductive adhesive layer 1 is in close contact with the top coat layer 8, and the conductive adhesive layer 1 flows to fill the via 11 formed in the top coat layer 8, thereby realizing conduction with the ground wiring 5 . By hot pressing, the thermosetting resin reacts and hardens to become the electromagnetic wave shielding layer 12. In addition, in order to promote hardening, post-curing may be performed at 150°C to 190°C for 30 to 90 minutes after hot pressing.

The opening area of the passage 11 is preferably 0.8 mm ² or less, and preferably 0.008 mm ² or more. By setting it as such a range, the area of the ground wiring can be narrowed, and the size of the printed circuit can be reduced. The shape of the passage is not particularly limited, and any of circles, squares, rectangles, triangles, and irregular shapes can be used according to the application. Through these steps, the electromagnetic wave shielding wiring circuit board 7 is obtained.

In terms of suppressing the leakage of electromagnetic waves more effectively, it is preferable to laminate electromagnetic wave shielding layers on both sides of the printed circuit board. In addition, the electromagnetic wave shielding layer in the electromagnetic wave shielding printed circuit board of the present invention can be used as a grounding circuit in addition to shielding electromagnetic waves. By this, by omitting a part of the grounding circuit, the area of the printed circuit board is reduced and the cost is reduced. It is possible and can be assembled into a small area inside the frame.

Furthermore, the signal wiring is not particularly limited, and it can be used in either a single ended (single ended) circuit including one signal wiring or a differential circuit including two signal wirings, but a differential circuit is preferable. On the other hand, when there are restrictions on the circuit pattern area of the printed circuit board and it is difficult to form a ground circuit in parallel, the ground circuit may not be provided in the lateral direction of the signal circuit, and the electromagnetic wave shielding layer may be used as the ground circuit to be formed in the thickness direction. It has a grounded printed circuit structure.

The electromagnetic wave shielding printed circuit board of the present invention is preferably mounted on electronic devices such as notebook PCs, mobile phones, smart phones, and tablet terminals in addition to liquid crystal displays, touch screens, and the like. [Example]

Hereinafter, the present invention will be explained in more detail through examples, but the present invention is not limited to the following examples. In addition, "parts" in the examples means "parts by mass", and "%" means "% by mass".

In addition, the acid value of the resin, the weight average molecular weight (Mw), the glass transition temperature (Tg), and the average particle diameter of the conductive filler are measured by the following methods.

"Determination of acid value of binder resin" The acid value is measured in accordance with JIS K0070. Accurately measure about 1 g of the sample in a stoppered Erlenmeyer flask, add 100 mL of tetrahydrofuran/ethanol (volume ratio: tetrahydrofuran/ethanol=2/1) mixture to dissolve. A phenolphthalein test solution was added as an indicator, and titration was performed with a 0.1 N alcoholic potassium hydroxide solution, and the time when the indicator remained light red for 30 seconds was set as the end point. Calculate the acid value (unit: mgKOH/g) according to the following formula. Acid value (mgKOH/g)=(5.611×a×F)/S in, S: The amount of sample taken (g) a: Consumption of 0.1N alcoholic potassium hydroxide solution (mL) F: The titer of 0.1N alcoholic potassium hydroxide solution

"Determination of the weight average molecular weight (Mw) of the binder resin" The weight average molecular weight (Mw) was measured using a gel permeation chromatography (Gel Permeation Chromatograph, GPC) "HPC-8020" manufactured by Tosoh Co., Ltd. GPC is a liquid chromatograph that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on their molecular size differences. In the measurement of the present invention, two "LF-604" (manufactured by Showa Denko Co., Ltd.: GPC column for rapid analysis: 6 mmID×150 mm size) are connected in series and used as a column, and the flow rate is 0.6 mL/ Min, the column temperature is 40°C, and the weight average molecular weight (Mw) is determined by polystyrene conversion.

"Glass Transition Temperature (Tg) of Adhesive Resin" The Tg is measured by differential scanning calorimetry ("DSC-1" manufactured by Mettler Toledo).

"Measurement of the average particle size of conductive filler" The average particle size of D ₅₀ is measured by using a laser diffraction and scattering method particle size distribution analyzer LS13320 (manufactured by Beckman Coulter), and the powder sample is dried by a cyclone Module (tornado dry powder sample module) is the value obtained by measuring the conductive filler, and it is the particle size whose cumulative value in the cumulative particle size distribution is 50%. In addition, the refractive index is set to 1.6.

Next, the raw materials used in the examples are shown below. "Raw material" Conductive filler 1: Composite fine particles (dendritic fine particles coated with 10 parts by mass of silver relative to 100 parts by mass of copper as a core) Average particle size D ₅₀ : 12.0 μm Fukuda Metal Foil Powder Industry Company-manufactured conductive filler 2: Composite fine particles (dendritic fine particles coated with 10 parts by mass of silver relative to 100 parts by mass of copper as a core) Average particle size D ₅₀ : 1.0 μm Fukuda Metal Foil & Powder Industry Co., Ltd. Manufacture of conductive filler 3: Composite fine particles (dendritic fine particles coated with 10 parts by mass of silver relative to 100 parts by mass of copper as a core) Average particle size D ₅₀ : 6.0 μm manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd. Conductive filler 4: Composite fine particles (dendritic fine particles coated with 10 parts by mass of silver relative to 100 parts by mass of copper as a core) Average particle size D ₅₀ : 17.0 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd. Conductive Filler 5: Composite fine particles (dendritic fine particles coated with 10 parts by mass of silver relative to 100 parts by mass of copper as the core) Average particle size D ₅₀ : 32.0 μm Adhesive manufactured by Fukuda Metal Foil Industry Co., Ltd. Resin: Polyurethane urea resin with acid value of 5 mgKOH/g, Mw of 54,000 and Tg of -7°C (manufactured by TOYO CHEM) Epoxy compound: "JER828" (bisphenol A epoxy Resin epoxy equivalent = 189 g/eq) Aziridine compound manufactured by Mitsubishi Chemical Corporation: "Chemitite PZ-33" manufactured by Japan Catalyst Co., Ltd. Pigment: carbon black "MA100" Carrier material manufactured by Mitsubishi Chemical Corporation: ""EmbletS25" manufactured by UNITIKA

Table 1 shows the copper foil with carrier material used. These copper foils with a carrier material are formed by forming a patterned resist layer on the copper foil formed on the carrier material, and etching the copper foil to form openings, and have the thickness shown in Table 1. And copper foil such as aperture ratio.

[Table 1] Table 1. Copper foil with carrier material A1 Copper foil with carrier material A2 Copper foil with carrier material A3 Copper foil with carrier material A4 Copper foil with carrier material A5 Copper foil with carrier material A6 Copper foil with carrier material A7 Copper foil with carrier material A8 Copper foil Thickness [μm] 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 The area of an opening [μm ² ] 314 314 314 314 314 314 314 314 Number of openings [pieces/cm ² ] 9550 0 960 1600 20700 47700 63600 68200 Opening rate [%] 3.0% 0% 0.3% 0.5% 6.5% 15.0% 20.0% 21.4% Copper foil with carrier material A9 Copper foil with carrier material A10 Copper foil with carrier material A11 Copper foil with carrier material A12 Copper foil with carrier material A13 Copper foil with carrier material A14 Copper foil Thickness [μm] 0.1 0.3 0.5 3.5 5.0 7.0 The area of an opening [μm ² ] 314 314 314 314 314 314 Number of openings [pieces/cm2] 9550 9550 9550 9550 9550 9550 Opening rate [%] 3.0% 3.0% 3.0% 3.0% 3.0% 3.0%

<Production of conductive adhesive layer 1> In terms of solid content, 100 parts of binder resin, 1 47 parts of conductive filler, 10 parts of epoxy compound, and 0.5 part of aziridine compound are put into the container, and the mixed solvent is added so that the concentration of non-volatile content becomes 40% (Toluene: isopropanol=2:1 (mass ratio)), and stirred with a disperser for 10 minutes to obtain a conductive resin composition.

Using a bar coater, the conductive resin composition was coated on the peelable sheet so that the dry thickness became 10 μm, and dried in an electric oven at 100° C. for 2 minutes, thereby obtaining a conductive adhesive layer 1.

<Manufacturing of Conductive Adhesive Layer 2-Conductive Adhesive Layer 12> The conductive adhesive layer 2 to the conductive adhesive layer 12 shown in Table 2 to Table 5 were produced in the same manner as the conductive adhesive layer 1 except that the type and the amount of the conductive filler were changed.

[Example 1] In terms of solid content, 100 parts of the binder resin, 30 parts of the epoxy compound, and 7.5 parts of the aziridine compound were added, and stirred with a disperser for 10 minutes to obtain a resin composition. Using a bar coater, the obtained resin composition was applied to a copper foil A1 with a carrier material so that the dry thickness became 5 μm, and dried in an electric oven at 100°C for 2 minutes to form a protective layer 1 and micro-adhesive The peelable sheet is attached to the protective layer 1.

Then, the carrier material of the copper foil A1 with the carrier material was peeled, the copper foil surface was polished, and the 60° mirror gloss of the copper foil surface was adjusted to the value shown in Table 2, and the copper foil 2 was produced. The conductive adhesive layer 4 is attached to the polished copper foil surface, thereby obtaining an electromagnetic wave shielding sheet including "peelable sheet/protective layer 1/copper foil 2/conductive adhesive layer 4/peelable sheet". The bonding of the copper foil 2 and the conductive adhesive layer 4 is performed by a thermal laminator ^{at a temperature of 90° C. and a pressure of 3 kgf/cm 2.}

[Example 2 to Example 33, Comparative Example 1 to Comparative Example 4] Except that the types of conductive adhesive layer, protective layer, and copper foil were changed as shown in Tables 1 to 5, the same procedure as in Example 1 was carried out to obtain Examples 2 to 33 and Comparative Example 1, respectively. ~ The electromagnetic wave shielding sheet of Comparative Example 4. When the target value of the 60° mirror gloss on the copper foil surface is different from the value of the carrier material, the 60° mirror gloss is adjusted by appropriately polishing the surface or roughening the surface.

With respect to the obtained electromagnetic wave shielding sheet, the thickness of each layer, the 60° specular gloss of the metal layer, and the loss tangent of the electromagnetic wave shielding sheet were measured by the following methods.

"Measurement of the thickness of each layer" The thickness of the conductive adhesive layer, the metal layer, and the protective layer after hot pressing of the electromagnetic wave shielding sheet is measured by the following method. The peelable sheet on the conductive adhesive layer side of the electromagnetic wave shielding sheet is peeled off, and the exposed conductive adhesive layer and the polyimide film ("Kapton" manufactured by Toray-Dupont Co., Ltd.) are peeled off. 200EN”) bonding and hot pressing at 2 MPa and 170°C for 30 minutes. After cutting it into a size of 5 mm in width and 5 mm in length, 0.05 g of epoxy resin (Petropoxy 154, manufactured by Maruto Co., Ltd.) was dropped onto the glass slide. Then, the electromagnetic wave shielding sheet is bonded to obtain a laminate of glass slide/electromagnetic wave shielding sheet/polyimide film. For the obtained laminate, a cross section polisher (manufactured by JEOL Co., Ltd., SM-09010) was cut from the polyimide film side by ion beam irradiation to obtain a hot press of the electromagnetic wave shielding sheet. After the measurement sample.

The cross section of the obtained measurement sample was observed using a laser microscope (manufactured by KEYENCE, VK-X100), and the thickness of each layer was measured based on the enlarged image obtained by the observation. The magnification is set from 500 times to 2000 times.

"Measurement of 60° Mirror Gloss" The 60° specular gloss of the metal layer of the electromagnetic wave shielding sheet was measured by the following method. The peelable sheet on the conductive adhesive layer side of the electromagnetic wave shielding sheet is peeled off, and the end of the adhesive tape ("CT1835" manufactured by Nichiban) is pasted on the exposed conductive adhesive layer. Join the adhesive tape, peel off from the end of the adhesive tape, and peel off the conductive adhesive layer/adhesive tape. The conductive adhesive layer is removed, and the surface of the exposed metal layer is measured using a glossmeter (manufactured by BYK, Micro-Tri-Gloss) and measuring the gloss of the mirror surface. The measured value at an angle of 60° is regarded as 60° specular gloss.

"Determination of Loss Tangent of Laminated Hardened Material" The loss tangent of the laminate cured product is measured by the following method. First, prepare two electromagnetic wave shielding sheets with a width of 50 mm and a length of 50 mm. The peelable sheets on the conductive adhesive layer side are peeled off, and the exposed conductive adhesive layers are bonded to each other at 170°C, 2.0 MPa , Crimping under the condition of 30 minutes to make it heat-cured to obtain a laminated hardened product. After that, the central part of the laminated hardened product was cut to a width of 5 mm and a length of 30 mm, as a sample. Set this sample in a dynamic viscoelasticity measuring device (DVA-200, a dynamic viscoelasticity measuring device, manufactured by IT Measurement and Control Co., Ltd.) under the conditions of heating rate: 10°C/min, measuring frequency: 1 Hz, and strain: 0.08% The dynamic viscoelasticity measurement is carried out under the following conditions, and the loss elastic coefficient E" and storage elastic coefficient E'at 125°C are read according to the obtained dynamic viscoelastic curve, and the loss tangent of the laminated hardened product is calculated.

The following evaluation was performed using the obtained electromagnetic wave shielding sheet. The results are shown in Table 2 to Table 5.

＜Reflow resistance＞ The resistance to reflow soldering was evaluated by the following tests and the presence or absence of changes in appearance. The appearance of the electromagnetic wave shielding sheet with high reflow resistance does not change, but the electromagnetic wave shielding sheet with low reflow resistance undergoes foaming or peeling. First, the peelable sheet of the conductive adhesive layer of the electromagnetic wave shielding sheet with a width of 25 mm and a length of 70 mm is peeled off, and the exposed conductive adhesive layer is separated from the gold-plated copper-clad laminate (gold-plated 0.3 μm/nickel-plated 1 μm/copper foil 18 μm/adhesive 20 μm/polyimide film 25 μm) The gold-plated surface is crimped at 170°C, 2.0 MPa, and 30 minutes to make it thermally hardened And a laminate is obtained. The obtained laminate was cut into a size of 10 mm in width and 65 mm in length to prepare samples. The obtained sample was placed in a gas environment of 40° C. and 90% RH for 72 hours. After that, the polyimide film of the sample was floated on the molten solder at 250°C for 1 minute, and then the sample was taken out to visually observe its appearance, and evaluate whether there are abnormalities such as foaming, floating, peeling, etc. according to the following criteria . ◎: There is no change in appearance at all. Very good. ○: A small amount of small foaming is observed. Good. Δ: A large amount of small foaming is observed. Can be practical. ×: Severe foaming or peeling is observed. Not practical.

＜Bending resistance＞ Peel off the conductive adhesive layer of the electromagnetic wave shielding sheet with a width of 20 mm and a length of 100 mm, and separate the exposed conductive adhesive layer from the Kapton 500H with a width of 20 mm and a length of 100 mm. Crimping was performed under the conditions of ℃, 2.0 MPa, and 30 minutes to heat-harden to obtain a sample. The obtained sample was bent 180 degrees so that the electromagnetic wave shielding layer of the sample was outside, and a 1000 g weight was placed on the bent portion for 10 seconds. After that, the bent portion was restored to its original flat state. Place a weight of 1000 g for 10 seconds and set this as the number of bends once. Use the microscope "VHX-900" manufactured by KEYENCE (stock) to observe whether there are cracks in the electromagnetic wave shielding sheet, and evaluate the number of times that it can be bent without cracks. Count the number of flexures before cracks occur in the flexure where a 1000 g load is applied. 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. Can be practical. ×: Less than 2 times. Not practical.

＜High frequency shielding ability＞ Regarding high-frequency shielding performance, according to American Society for Testing and Materials (ASTM) D4935, a coaxial tube-type shielding effect measurement system manufactured by Keycom is used to obtain a non-bonding effect. A sample obtained by curing the electromagnetic wave shielding sheet by thermocompression bonding of the body. Then, the sample was irradiated with electromagnetic waves under the conditions of 100 MHz to 15 GHz, and the amount of attenuation of the electromagnetic wave attenuation was measured, and marking was performed in accordance with the following standards. The sample obtained by curing the electromagnetic wave shielding sheet was obtained by hot pressing the electromagnetic wave shielding sheet to which the peelable sheet was attached under the conditions of 150° C., 2.0 MPa, and 30 minutes, and peeling the peelable sheet. In addition, the measured value of the attenuation is decibels (unit; dB). ◎: The attenuation when irradiating 15 GHz electromagnetic waves is less than -55 dB. Extremely good. ○: The amount of attenuation when irradiating 15 GHz electromagnetic waves is -55 dB or more and less than -50 dB. good. Δ: The amount of attenuation when irradiating electromagnetic waves of 15 GHz is more than -50 dB and less than -45 dB. Can be practical. ×: The amount of attenuation when irradiating 15 GHz electromagnetic waves is -45 dB or more. Not practical.

<Reliability of Cooling and Heating Cycles> The reliability of cooling and heating cycles is evaluated by measuring the connection resistance value through the small opening passage before and after the cooling and heating cycle. The specific method of evaluation is shown below. Prepare the electromagnetic wave shielding sheet with a width of 20 mm and a length of 50 mm. The peelable sheet of the electromagnetic wave shielding sheet of each Example and Comparative Example was peeled off, and the exposed conductive adhesive layer was crimped to a separately produced flexible printed circuit under the conditions of 170° C., 2 MPa, and 30 minutes. Specifically, as shown in FIG. 4, as a printed circuit, a copper foil circuit 22A and a copper foil circuit 22B with a thickness of 18 μm, which are not electrically connected to each other, are formed on a polyimide film 21 with a thickness of 25 μm. A circuit of a polyimide cover layer 23 with an adhesive having a thickness of 37.5 μm and a circular via 24 with a diameter of 1.1 mm (via area 1.0 mm ^{2) is laminated on the copper foil circuit 22A.} Then, after pressure bonding was performed under the conditions of 170° C., 2 MPa, and 30 minutes, the conductive adhesive layer 25b and the protective layer 25a of the electromagnetic wave shielding sheet were cured, thereby obtaining a sample. Next, the peelable sheet on the side of the protective layer 25a of the sample was removed, and the "Loresta GP" BSP probe manufactured by Mitsubishi Chemical Analytech was used to measure the plan view of (4) in FIG. 4 The initial connection resistance value between 22A-22B shown. In addition, (2) of FIG. 4 is a cross-sectional view of D-D′ of (1) of FIG. 4, and (3) of FIG. 4 is a cross-sectional view of CC′ of (1) of FIG. 4. Similarly, (5) of FIG. 4 is a cross-sectional view of D-D′ of (4) of FIG. 4, and (6) of FIG. 4 is a cross-sectional view of CC′ of (4) of FIG. 4. Put the sample into the thermal shock device ("TSE-11-A", manufactured by Espec), and expose at high temperature: 125°C for 15 minutes, low temperature exposure: -50°C for 15 minutes Perform 200 alternate exposures. After that, the connection resistance value of the sample was measured in the same manner as in the initial stage. The evaluation criteria for the reliability of the cooling and heating cycle are as follows. ◎: (Connection resistance value after alternate exposure)/(Initial connection resistance value) is less than 1.5. Extremely good. ○: (connection resistance value after alternate exposure)/(initial connection resistance value) is 1.5 or more and less than 3.0. good. Δ: (connection resistance value after alternate exposure)/(initial connection resistance value) is 3.0 or more and less than 5.0. Can be practical. ×: (connection resistance value after alternate exposure)/(initial connection resistance value) is 5.0 or more. Not practical.

[Table 2] Table 2. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Conductive adhesive layer type Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 10 10 10 10 10 10 10 10 10 10 10 Aziridine compounds 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Conductive filler Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler content [parts] 74 74 74 74 74 74 74 74 74 74 74 Conductive filler content [mass%] 40% 40% 40% 40% 40% 40% 40% 40% 40% 40% 40% Metal layer type Copper foil 2 Copper foil 3 Copper foil 4 Copper foil 5 Copper foil 6 Copper foil 7 Copper foil 8 Copper foil 11 Copper foil 12 Copper foil 13 Copper foil 14 Copper foil with carrier material Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A3 Copper foil with carrier material A4 Copper foil with carrier material A5 Copper foil with carrier material A6 60° mirror gloss 791 745 698 455 42 twenty one 13 455 455 455 455 Thickness [μm] 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Opening rate [%] 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 0.30% 0.50% 6.5% 15.0% The protective layer type Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 30 30 30 30 30 30 30 30 30 30 30 Aziridine compounds 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 pigment 8 8 8 8 8 8 8 8 8 8 8 Laminated hardened material loss tangent 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Evaluation Reflow resistance ○ ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ◎ ◎ Bending tolerance ◎ ◎ ◎ ◎ ◎ ○ Δ ◎ ◎ ◎ ○ High frequency shielding [15GHz] ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ○ Cooling and heating cycle reliability Δ ○ ◎ ◎ ◎ ○ Δ ◎ ◎ ◎ ◎

[table 3] table 3. Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Conductive adhesive layer type Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 10 10 10 10 10 10 10 10 10 10 10 Aziridine compounds 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Conductive filler Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler content [parts] 74 74 74 74 74 74 74 74 74 74 74 Conductive filler content [mass%] 40% 40% 40% 40% 40% 40% 40% 40% 40% 40% 40% Metal layer type Copper foil 15 Copper foil 17 Copper foil 18 Copper foil 19 Copper foil 20 Copper foil 21 Copper foil 22 Copper foil 23 Copper foil 24 Copper foil 4 Copper foil 4 Copper foil with carrier material Copper foil with carrier material A7 Copper foil with carrier material A4 Copper foil with carrier material A3 Copper foil with carrier material A9 Copper foil with carrier material A10 Copper foil with carrier material A11 Copper foil with carrier material A12 Copper foil with carrier material A13 Copper foil with carrier material A14 Copper foil with carrier material A1 Copper foil with carrier material A1 60° mirror gloss 455 745 745 455 455 455 455 455 455 455 455 Thickness [μm] 1.0 1 1 0.1 0.3 0.5 3.5 5.0 7.0 1.0 1.0 Opening rate [%] 20.0% 0.5% 0.3% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% The protective layer type Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 2 Protective layer 3 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 30 30 30 30 30 30 30 30 30 50 60 Aziridine compounds 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 pigment 8 8 8 8 8 8 8 8 8 8 8 Laminated hardened material loss tangent 0.15 0.15 0.15 0.17 0.16 0.16 0.13 0.12 0.08 0.12 0.09 Evaluation Reflow resistance ◎ ○ Δ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Bending tolerance Δ ◎ ◎ Δ ○ ◎ ◎ ○ Δ ◎ ◎ High frequency shielding [15GHz] Δ ◎ ◎ Δ ○ ◎ ◎ ◎ ◎ ◎ ◎ Cooling and heating cycle reliability ◎ ○ ○ ◎ ◎ ◎ ◎ ○ Δ ○ Δ

[Table 4] Table 4. Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Example 29 Example 30 Example 31 Example 32 Example 33 Conductive adhesive layer type Conductive adhesive layer 1 Conductive adhesive layer 2 Conductive adhesive layer 3 Conductive adhesive layer 5 Conductive adhesive layer 6 Conductive adhesive layer 7 Conductive adhesive layer 8 Conductive adhesive layer 9 Conductive adhesive layer 10 Conductive adhesive layer 11 Conductive adhesive layer 12 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 10 10 10 10 10 10 10 10 10 10 10 Aziridine compounds 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Conductive filler Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 2 Conductive filler 3 Conductive filler 4 Conductive filler 5 Conductive filler content [parts] 47 60 71 205 258 995 1271 74 74 74 74 Conductive filler content [mass%] 30% 35% 39% 65% 70% 90% 92% 40% 40% 40% 40% Metal layer type Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil 4 Copper foil with carrier material Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A1 60° mirror gloss 455 455 455 455 455 455 455 455 455 455 455 Thickness [μm] 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Opening rate [%] 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% 3.0% The protective layer type Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Adhesive resin 100 100 100 100 100 100 100 100 100 100 100 Epoxy compound 30 30 30 30 30 30 30 30 30 30 30 Aziridine compounds 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 pigment 8 8 8 8 8 8 8 8 8 8 8 Laminated hardened material loss tangent 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Evaluation Reflow resistance ◎ ◎ ◎ ◎ ○ ○ Δ ◎ ◎ ◎ ◎ Bending tolerance ◎ ◎ ◎ ◎ ○ ○ Δ ◎ ◎ 〇 Δ High frequency shielding [15GHz] Δ ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Cooling and heating cycle reliability Δ ○ ○ ◎ ◎ ◎ ◎ Δ ○ ◎ ◎

[table 5] table 5. Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Conductive adhesive layer type Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Conductive adhesive layer 4 Adhesive resin 100 100 100 100 Epoxy compound 10 10 10 10 Aziridine compounds 0.5 0.5 0.5 0.5 Conductive filler Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler 1 Conductive filler content [parts] 74 74 74 74 Conductive filler content [mass%] 40% 40% 40% 40% Metal layer type Copper foil 1 Copper foil 9 Copper foil 10 Copper foil 16 Copper foil with carrier material Copper foil with carrier material A1 Copper foil with carrier material A1 Copper foil with carrier material A2 Copper foil with carrier material A8 60° mirror gloss 830 5 455 455 Thickness [μm] 1.0 1.0 1.0 1.0 Opening rate [%] 3.0% 3.0% 0.0% 21.4% The protective layer type Protective layer 1 Protective layer 1 Protective layer 1 Protective layer 1 Adhesive resin 100 100 100 100 Epoxy compound 30 30 30 30 Aziridine compounds 7.5 7.5 7.5 7.5 pigment 8 8 8 8 Laminated hardened material loss tangent 0.15 0.15 0.15 0.15 Evaluation Reflow resistance Δ ◎ X ◎ Bending tolerance ◎ X ◎ X High frequency shielding [15GHz] ◎ ◎ ◎ X Cooling and heating cycle reliability X X ◎ ◎

a1: Conductive adhesive layer a2: metal layer a3: protective layer a4: opening 5: Ground wiring 6: Signal wiring 7: Electromagnetic wave shielding wiring circuit board 8: Top coat 9: Insulating base material 10: Electromagnetic wave shielding sheet 11: Access 12: Electromagnetic wave shielding layer 21: Polyimide film 22A, 22B: copper foil circuit 23: Polyimide coating with adhesive 24: circular path 25a: protective layer 25b: Conductive adhesive layer

FIG. 1 is a cross-sectional view illustrating the electromagnetic wave shielding sheet of this embodiment. FIG. 2 is a diagram illustrating a comparison of the ratio of specular reflection light/diffuse reflection light on surfaces with different roughnesses. 3 is a schematic cross-sectional view of a cut portion showing an example of the electromagnetic wave shielding printed circuit board of the present embodiment. Fig. 4 is a schematic plan view and a cross-sectional view of a cut portion of the reliability evaluation of the cooling and heating cycle. Figure 5 is a dynamic viscoelastic curve of a laminated hardened product (Example 5).

a1: Conductive adhesive layer

a2: metal layer

a3: protective layer

a4: opening

10: Electromagnetic wave shielding sheet

Claims (6)

An electromagnetic wave shielding sheet, which is characterized in that: A laminate having a conductive adhesive layer, a metal layer, and a protective layer in this order, On the surface of the metal layer in contact with the conductive adhesive layer, the 60° specular gloss calculated in accordance with International Organization for Standardization 7668 is 10 to 800, The metal layer has a plurality of openings, and the opening ratio is 0.10% to 20%. The electromagnetic wave shielding sheet according to claim 1, wherein the laminate cured product obtained by hot pressing the laminate at 170°C for 30 minutes has a loss tangent at 125°C of 0.10 or more. The electromagnetic wave shielding sheet according to claim 1 or 2, wherein the thickness of the metal layer is 0.3 μm to 5.0 μm. The electromagnetic wave shielding sheet according to claim 1 or claim 2, wherein the conductive adhesive layer contains a binder resin and a conductive filler, and the conductive filler in the conductive adhesive layer has D ₅₀ The average particle size is 2 μm to 30 μm. The electromagnetic wave shielding sheet according to claim 4, wherein: The content of the conductive filler in the conductive adhesive layer is 35% to 90% by mass. An electromagnetic wave shielding wiring circuit board, characterized by comprising: an electromagnetic wave shielding layer formed of the electromagnetic wave shielding sheet according to any one of claims 1 to 5, a top coat, and a circuit having signal wiring and an insulating base material .

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