TWI776943B - Electromagnetic wave shielding film - Google Patents

Abstract

The present invention provides an electromagnetic wave shielding film with good transmission characteristics. An electromagnetic wave shielding film comprising an insulating protective layer, a shielding layer, and an adhesive layer, wherein the average length RSm of roughness curve elements on the surface of the adhesive layer side surface of the shielding layer is 40 μm or more and 100 μm or less.

Description

Electromagnetic wave shielding film

The present invention relates to an electromagnetic wave shielding film, a method for producing the same, and a shielding printed wiring board.

Background Art As a method of shielding a printed wiring board from electromagnetic waves, a method of bonding an electromagnetic wave shielding film having a shielding layer and a conductive adhesive layer to a printed wiring board is known. In this method, the printed wiring board is shielded by connecting the conductive adhesive layer of the electromagnetic wave shielding film and the ground circuit of the printed wiring board through the opening provided in the insulating film covering the ground circuit.

Patent Document 1 describes an electromagnetic wave shielding sheet comprising a laminate including an adhesive layer containing a conductive filler, a conductive layer, and an insulating layer. Patent Document 2 describes an electromagnetic wave shielding film including a roughened electromagnetic shielding layer on at least one surface. Patent Document 3 describes an electromagnetic wave shielding film including a conductive shielding layer and an adhesive layer, and wherein the maximum height of irregularities of the conductive shielding layer is larger than the thickness of the adhesive layer.

Prior Art Documents Patent Documents [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-157838 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-133474 [Patent Document 3] International Publication No. 2016/088381

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION Patent Document 1 describes that the electromagnetic wave shielding sheet described above can maintain good transmission characteristics. However, since the electromagnetic wave shielding sheet described in Patent Document 1 uses the conductive filler in the adhesive layer, it is not satisfactory in terms of the material cost of the conductive filler and the like. In addition, it is difficult to make the electromagnetic wave shielding sheet thinner than the particle size of the conductive filler in thinning the electromagnetic wave shielding sheet.

In Patent Document 2, by passing the roughened surface of the electromagnetic shielding layer through the film layer, even when the adhesive layer does not contain a conductive filler, at least a part of the roughened surface can be connected to the base layer of the circuit board and grounded. However, Patent Document 2 does not describe the relationship between the parameters related to the roughened surface roughness and the transmission loss.

In Patent Document 3, it is described that the convex portion of the conductive shield layer can be connected to the ground circuit through the adhesive layer, but the relationship between the parameters related to the roughened surface roughness and the transmission loss is also not mentioned.

The subject of this invention is to provide the electromagnetic wave shielding film which has favorable transmission characteristics. Another subject of this invention is to provide the electromagnetic wave shielding film which has favorable transmission characteristics in the electromagnetic wave shielding film whose adhesive layer does not contain a conductive filler.

MEANS TO SOLVE THE PROBLEM The present inventors have devoted themselves to researches on the above-mentioned problems. As a result, they have found that the electromagnetic wave shielding sheet in which the convex portion of the shielding layer is connected to the ground circuit through an adhesive layer that does not contain a conductive filler When the distance from the signal circuit is large and the proportion of the adhesive is large, good transmission characteristics can be obtained. Then, the present inventors found that when the average length RSm of the roughness curve elements on the surface of the adhesive layer side in the shield layer is set to 40 μm or more and 100 μm or less, the electromagnetic wave shielding film and the When the printed wiring board is attached, the convex part of the shielding layer can pass through the adhesive layer to be connected to the ground circuit, and even after the convex part of the shielding layer passes through the adhesive layer, there is no connection between the shielding layer and the printed wiring board. When the adhesive is sufficiently stored, the distance between the shield layer and the signal circuit is increased, and as a result, good transmission characteristics can be obtained, and the present invention has been completed.

The present invention includes the following suitable aspects. [1] An electromagnetic wave shielding film having an insulating protective layer, a shielding layer, and an adhesive layer, wherein the average length RSm of the roughness curve element according to JIS B 0601:2013 on the surface of the adhesive layer in the shielding layer is 40 μm more than 100 μm or less. [2] The electromagnetic wave shielding film according to [1], wherein the load area ratio Smr2 of the adhesive layer side surface in the shielding layer is 92% or more. [3] The electromagnetic wave shielding film according to [1] or [2], wherein the insulating protective layer contains particulate matter. [4] The electromagnetic wave shielding film according to [3], wherein the average particle diameter of the particulate matter is 15 μm or more. [5] A shielded printed wiring board to which the electromagnetic wave shielding film according to any one of [1] to [4] is attached. [6] A method for producing an electromagnetic wave shielding film, which is a method for producing the electromagnetic wave shielding film according to any one of [1] to [4], comprising the steps of: coating an insulating resin composition on a support substrate and hardening it to obtain an insulating protective layer; forming a shielding layer on the insulating protective layer; and forming an adhesive layer on the shielding layer.

Advantageous Effects of Invention According to the electromagnetic wave shielding film of one aspect of the present invention, even if the adhesive layer does not contain a conductive filler, when the electromagnetic wave shielding film and the printed wiring board are bonded together, the protrusions of the shielding film can be connected to the ground circuit of the printed wiring board. connection, and can play a good transmission characteristics.

MODE FOR CARRYING OUT THE INVENTION <Electromagnetic wave shielding film> An electromagnetic wave shielding film according to an aspect of the present invention has an insulating protective layer, a shielding layer, and an adhesive layer, and the surface of the shielding layer on the side of the adhesive layer conforms to JIS B The average length RSm (hereinafter also referred to as RSm) of the roughness curve elements of 0601:2013 is 40 μm or more and 100 μm or less.

The electromagnetic wave shielding film of one aspect of the present invention may be in the form of a roll that is rolled up while maintaining an elongated state, or may be in the form of a cut single sheet.

FIG. 1 shows an electromagnetic wave shielding film 100 according to an aspect of the present invention. As shown in FIG. 1 , the electromagnetic wave shielding film 100 has an insulating protective layer 110 , a shielding layer 120 and an adhesive layer 130 in this order. The RSm of the surface on the side of the adhesive layer 130 in the shield layer 120 is 40 μm or more and 100 μm or less.

(Insulating protective layer) The insulating protective layer is provided to protect the shield layer. The insulating protective layer may be, for example, a coating layer and/or film composed of an insulating resin composition.

The insulating resin should just have insulating properties, and examples thereof include thermoplastic resins, thermosetting resins, active energy ray-curable resins, and the like. The insulating resins may be used alone or in combination of two or more.

As a thermosetting resin, a phenol type resin, an epoxy type resin, a urethane type resin, a melamine type resin, an alkyd type resin, etc. are mentioned, for example.

As a thermoplastic resin, a styrene-type resin, a vinyl acetate-type resin, a polyester-type resin, a polyethylene-type resin, a polypropylene-type resin, an imide-type resin, an amide-type resin, an acrylic resin, etc. are mentioned, for example.

As an active-energy-ray-curable resin, the radical polymerizable compound etc. which are hardened by irradiation of an ultraviolet-ray, an electron beam, etc. are mentioned, for example. As an example of a radically polymerizable compound, the polymerizable compound etc. which have at least 2 (meth)acryloyloxy groups in a molecule|numerator are mentioned, for example. When the insulating resin composition contains an active energy ray-curable resin, the insulating resin composition preferably contains a polymerization initiator, for example, a radical polymerization initiator.

The insulating resin is preferably a thermosetting resin, preferably an epoxy resin. When an epoxy-based resin is used as the insulating resin, the shield layer tends to be easily prevented from being thermally damaged in the reflow step of mounting the electronic component on the printed wiring board.

The insulating resin composition may contain particulate matter. When the insulating resin composition contains particulate matter, it tends to be easy to manufacture an electromagnetic wave shielding film in which at least the shielding layer side surface of the insulating protective layer is uneven and the RSm of the adhesive layer side surface of the shielding layer is 40 μm or more and 100 μm or less. The kind of particulate matter, the average particle diameter (D50), the content in the insulating resin composition, the shape, and the like can be exemplified in the production of the electromagnetic wave shielding film described later.

The insulating resin composition may optionally contain at least one of the following additives: for example, a solvent, a crosslinking agent, a catalyst for polymerization, a curing accelerator, an adhesion imparting agent, an antioxidant, a pigment, a dye, a colorant, a plasticizer, UV absorbers, defoamers, levelers, fillers, flame retardants, viscosity modifiers and anti-caking agents.

When the insulating protective layer is a coating layer composed of an insulating resin composition, as a method for forming a coating layer composed of an insulating resin composition, the following methods are exemplified: coating on a support substrate The insulating resin composition is dried and cured to obtain a coating layer. As a method of coating the insulating resin composition, well-known coating methods, for example, a die coating method, a corner wheel coating method, a gravure coating method, a slit die coating method, etc. are mentioned.

As the supporting substrate, for example, substrates composed of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polyethylene Amide (PA), Polycarbonate (PC), Polystyrene (PS) or Polyphenylene Sulfide (PPS). The support substrate can also be subjected to peeling treatment on the surface.

The thickness of the insulating protective layer may be, for example, 1 μm or more, preferably 1.5 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, and particularly preferably 4 μm or more. On the other hand, the thickness of the insulating protective layer may be, for example, 30 μm or less, preferably 20 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and particularly preferably 5 μm or less. When the thickness of the insulating protective layer is 1 μm or more and 30 μm or less, good insulating properties are obtained, the shielding layer and the adhesive layer are sufficiently protected, flexibility is easily obtained, and the electromagnetic wave shielding film tends to be thinned easily. The thickness of the insulating protective layer can be measured, for example, according to the thickness measurement method in the examples described later.

When the insulating protective layer is a film composed of an insulating resin composition, the film composed of the insulating resin composition can be produced by a known molding method such as extrusion molding, blow molding, and calender molding.

The insulating protective layer may be a laminate of two or more layers, for example, a combination of coating layers and/or films composed of two or more insulating resin compositions. For example, when the insulating protective layer is a two-layer laminate, the laminate may be, for example, a laminate in which films composed of two types of insulating resin compositions are bonded together, and a laminate composed of two insulating resin compositions is formed on the film composed of the insulating resin compositions. Laminates of coating layers composed of other insulating resin compositions, laminates in which coating layers composed of other insulating resin compositions are formed on coating layers composed of insulating resin compositions, and the like.

When the insulating protective layer is a laminate of two or more layers and the insulating protective layer contains particulate matter, the insulating resin composition constituting the outermost layer on the shield layer side preferably contains particulate matter.

It is preferable that the surface of the insulating protective layer is roughened at least on the shield layer side. If at least the surface on the side of the shielding layer is roughened, by forming the shielding layer on this surface, there is a tendency to easily obtain a shielding layer having a surface shape substantially the same as the roughness of the surface of the insulating protective layer on the adhesive layer side .

As a method of making the surface of the insulating protective layer uneven, for example, a method of forming the insulating protective layer from the insulating resin composition containing the particulate matter described above, and sprinkling on the coating film of the insulating resin composition, etc. Methods for Particulate Matter. Moreover, the surface of the formed insulating protective layer may be processed by sandblasting, plasma irradiation, electron beam irradiation, chemical treatment, embossing, or the like. Further, the following methods can also be exemplified: a method in which particulate matter is sprinkled in advance on a support substrate used in the step of forming an insulating protective layer to be described later, and then an insulating resin composition is applied; A method of coating the surface of a support substrate with an insulating resin composition. Among them, a method of forming an insulating protective layer from an insulating resin composition containing a particulate matter is preferable because it is easy to adjust the surface roughness.

When the surface on the shield layer side of the insulating protective layer is uneven, the shape of the surface on the shield layer side of the insulating protective layer can be appropriately set according to the formation method and thickness of the shield layer. When forming a shield layer having substantially the same shape as the surface of the insulating protective layer, the average length RSm of the roughness curve elements on the surface of the insulating protective layer, for example, may be 130 μm or less, preferably 120 μm or less, and more preferably 110 μm or less. When the RSm of the shield layer side surface of the insulating protective layer is 130 μm or less, the RSm of the adhesive layer side surface of the shield layer tends to be 40 μm or more and 100 μm or less, which is preferable.

(Shield Layer) The shield layer is not particularly limited as long as it has conductivity, and may be a metal film, a conductive film composed of conductive particles, or the like.

The metal constituting the metal film may be, for example, one selected from the group consisting of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or any one or more of these. alloy, etc. Among them, copper and an alloy containing copper are preferred from the viewpoint of shielding properties and economical efficiency.

As a method of forming a metal film, for example, electrolytic plating, electroless plating (for example, displacement plating, electroless plating, etc.), sputtering, electron beam vapor deposition, vacuum vapor deposition, and CVD are exemplified. Addition methods such as metal-organic methods, and combinations thereof, etc. Moreover, the metal foil formed by a rolling process, or the metal foil (for example, special electrolytic copper foil etc.) formed by electrolysis, etc. may be sufficient as a metal film. Among them, the addition method is preferable from the viewpoint of easy control of the thickness of the metal film and easy acquisition of a metal film having a desired thickness.

When the shielding layer is a conductive film composed of conductive particles, the conductive particles may be particles such as carbon, silver, copper, nickel, and solder, for example. Moreover, the electroconductive particle may be the silver-coated copper particle which performed silver plating on copper powder, the particle which performed metal plating on insulating particles such as resin balls and glass beads, and the like. These electroconductive particles can be used individually or in mixture of 2 or more types.

The shape of the conductive particles may be spherical, needle-like, fibrous, platelet-like, or dendritic, and from the viewpoint of forming a layered shape, a sheet-like shape is preferred.

The average particle diameter of electroconductive particle is not specifically limited, According to the surface roughness, thickness, etc. of a shielding layer, it can select suitably. The average particle diameter of the conductive particles may be, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1.5 μm or more, still more preferably 2 μm or more, and particularly preferably 4 μm or more. On the other hand, the average particle diameter of the conductive particles may be, for example, 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less, still more preferably 7 μm or less, and particularly preferably 6 μm or less. When the average particle diameter of the conductive particles is 0.1 μm or more and 10 μm or less, the RSm of the adhesive layer side surface of the shielding layer tends to be easily set to 40 μm or more and 100 μm or less, and the thickness of the electromagnetic wave shielding film tends to be appropriate. .

As a method of forming the electroconductive film which consists of electroconductive particle, the method of forming the coating film of the paste containing electroconductive particle, the method of scattering electroconductive particle on an insulating protective layer, etc. are mentioned, for example. As a paste containing electroconductive particle, the mixture etc. of electroconductive particle, a thermosetting resin, and/or thermoplastic resin are mentioned, for example. As an example of a thermosetting resin and a thermoplastic resin, the thermosetting resin and thermoplastic resin contained in the insulating resin composition which comprise the said insulating protective layer can be exemplified. The paste containing electroconductive particle may contain additives, such as a solvent, as needed.

The thickness of the shield layer is not particularly limited as long as the average length RSm of the roughness curve elements is within a predetermined range, and may be, for example, 0.1 μm or more and 15 μm or less. When the thickness of the shielding layer is 0.1 μm or more, the shielding properties of the electromagnetic wave shielding film become favorable. Moreover, when it is 15 micrometers or less, the bending resistance of an electromagnetic wave shielding film becomes favorable. The thickness of the shielding layer can be measured, for example, according to the thickness measurement method in the examples described later.

The lower limit of the thickness of the shielding layer is preferably 0.5 μm or more, preferably 1 μm or more, more preferably 2 μm or more, and particularly preferably 4 μm or more. On the other hand, the upper limit of the thickness of the shielding layer is preferably 12 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and particularly preferably 6 μm or less.

[式中，m表示週期數、Xs表示1個週期的長度]。RSm係經由後述實施例中說明的「RSm測定方法」測定出的值。The RSm of the adhesive layer side surface of the shielding layer is 40 μm or more and 100 μm or less. RSm is the average length RSm of the roughness curve element according to JIS B 0601:2013. As shown in FIG. 2 , RSm is the average value of the length Xs corresponding to one roughness curve element consisting of a peak and a valley among the reference lengths L of the roughness curve. Therefore, generally, as RSm is smaller, the number of irregularities in the surface roughness in a certain length tends to increase more easily. The surface RSm can be calculated as follows: [Math 1]

[In the formula, m represents the number of cycles, and Xs represents the length of one cycle]. RSm is the value measured by the "RSm measurement method" demonstrated in the Example mentioned later.

When RSm is less than 40 μm, the convex parts on the surface of the shielding layer (that is, when the adhesive layer does not contain a conductive filler, when the surface of the shielding layer is viewed from the surface on which the adhesive layer is laminated, the convex part of the shielding layer) with respect to each other. The space is narrowed, and the area of the concave portion on the surface of the shielding layer (that is, the concave portion of the shielding layer when the surface of the shielding layer is viewed from the surface on which the adhesive layer is laminated when the adhesive layer does not contain a conductive filler) becomes larger. few. Thereby, when the electromagnetic wave shielding film is attached to the printed wiring board, the ratio of the adhesive between the shielding layer and the printed wiring board is reduced, and the distance (average value) between the signal transmission channel and the shielding layer is reduced. Here, the attenuation of the signal transmitted in the signal transmission channel depends on the dielectric loss of the material existing between the signal transmission channel and the shielding layer. If the dielectric loss of the material existing between the signal transmission channel and the shielding layer changes, large, the attenuation of the signal also increases. Therefore, it is estimated that when RSm is less than 40 μm, the dielectric loss between the signal transmission channel and the shielding layer increases, and the amount of signal attenuation also increases. In addition, when RSm is estimated to exceed 100 μm, the distance between the convex portions on the surface of the shielding layer increases, and the contact area with the ground circuit decreases, so that good shielding characteristics cannot be obtained. In addition, it is estimated that when RSm exceeds 100 μm, the surface shape of the shield layer tends to be gentle and there are many convex portions with low heights. Therefore, the ratio of the adhesive layer existing between the shield layer and the signal circuit is reduced, and the transmission characteristics are deteriorated. However, the above presumptions are not intended to limit the present invention.

RSm is preferably 95 μm or less, preferably 90 μm or less, more preferably 85 μm or less, and particularly preferably 80 μm or less. On the other hand, RSm is preferably 45 μm or more, preferably 50 μm or more, and more preferably 55 μm or more.

For example, RSm can be set to a desired value by selecting a material constituting the insulating protective layer or shielding layer, adjusting the manufacturing conditions of the insulating protective layer or shielding layer, etc. However, the electromagnetic wave shielding film of one aspect of the present invention does not It is limited to those obtained by the above-mentioned means. Regarding the method of making RSm a predetermined value, there are the following methods: for example, the insulating protective layer contains a filler to form unevenness on the surface of the insulating protective layer, and the method of forming a shielding layer on the uneven surface by an addition method; For example, a method of removing a part of the surface of the shielding layer formed on the surface of the insulating protective layer by etching, etc.; A method for a shielding layer having a predetermined surface shape.

The load area ratio Smr2 (hereinafter also referred to as Smr2) of the shielding layer is preferably 92% or more, preferably 94% or more, more preferably 95% or more, and particularly preferably 95.5% or more. The upper limit of Smr2 is usually less than 100%, but may be 99% or less from the viewpoint of productivity. When Smr2 is 92% or more, it is easy to suppress the transmission loss of the high-frequency signal transmitted to the printed wiring board, and it tends to be easy to optimize the connectivity with the ground circuit of the printed wiring board.

The load area ratio Smr2 is a parameter defined by ISO 25178-2:2012. As conceptually shown in FIG. 3 , Smr2 refers to the secant of the load curve drawn with the difference ΔSmr of the load area ratio Smr as 40% in the central part of the load curve with respect to the thickness curve, and will be the secant of the slowest slope. When the straight line is set as an equivalent straight line, and the equivalent straight line is set as the core part between the position where the load area ratio is 0% and 100% and the two height positions where the vertical axis intersects, the load curve is related to the protruding valley part and the core part. The load area rate at the point where the boundary lines intersect. Smr2 is a value obtained in accordance with the Smr2 measurement method described in the examples below. In addition, the load curve is a load curve with respect to the surface, and is expressed as a function of the degree of cutting with respect to the load area ratio.

Smr2 can be set to a desired value by, for example, selecting the material constituting the insulating protective layer or the shielding layer, and adjusting the manufacturing conditions of the insulating protective layer or the shielding layer, etc. However, the electromagnetic wave shielding film of the present invention is not limited to the use of the above means to gain.

The load area ratio Smr1 (hereinafter also referred to as Smr1) of the shielding layer is preferably 17% or more, preferably 18% or more, more preferably 20% or more, and particularly preferably 22% or more. On the other hand, Smr1 is usually 50% or less. When Smr1 is 17% or more, it is easy to suppress the transmission loss of the high-frequency signal transmitted to the printed wiring board, and it tends to be easy to optimize the connectivity with the ground circuit of the printed wiring board.

The load area ratio Smr1 is a parameter defined by ISO 25178-2:2012. As conceptually shown in FIG. 3 , Smr1 refers to the secant line of the load curve drawn with the difference ΔSmr of the load area ratio Smr as 40% in the central part of the load curve with respect to the thickness curve, and will be the secant of the slowest slope. When the straight line is set as an equivalent straight line, and the equivalent straight line is set as the core part between the positions where the load area ratio is 0% and 100% and the two height positions where the vertical axis intersects, the load curve is related to the protruding mountain part and the core part. The load area rate at the point where the boundary lines intersect. Smr1 is a value determined according to the Smr1 measurement method described in the examples below. In addition, the load curve is a load curve with respect to the surface, and is expressed as a function of the degree of cutting with respect to the load area ratio.

Smr1 can be set to a desired value by, for example, selecting the material constituting the insulating protective layer or the shielding layer, and adjusting the manufacturing conditions of the insulating protective layer or the shielding layer. However, the electromagnetic wave shielding film of the present invention is not limited to the use of the above means to gain.

(Adhesive Layer) The adhesive layer may be constituted by a known adhesive or adhesive. From the viewpoint of suppressing transmission loss of high-frequency signals transmitted through the printed wiring board, the adhesive preferably has a low dielectric constant. The relative dielectric constant of the adhesive layer may be, for example, 1 to 5, preferably 2 to 2.8, at a measurement frequency of 1 GHz and a measurement temperature of 23°C. In addition, the dielectric loss tangent of the adhesive layer may be, for example, 0 to 0.03, preferably 0.0001 to 0.02, at a measurement frequency of 1 GHz and a measurement temperature of 23°C.

The adhesive layer can be insulating or conductive. When the adhesive layer is conductive, it may be anisotropic conductivity or isotropic conductivity. However, it is preferable that the adhesive layer does not contain conductive fillers (that is, insulating properties) from the viewpoint of suppressing transmission loss, thinning, and manufacturing cost.

When the adhesive layer contains a conductive filler, the conductive filler includes, for example, a metal filler, a carbon filler, a mixture thereof, and the like. As a metal filler, metal powders, such as silver, copper, and nickel, etc. are mentioned, for example, These may be covered with gold or silver.

The adhesive layer may be composed of an adhesive resin composition. The resin contained in the adhesive resin composition is not particularly limited as long as it has adhesiveness, and for example, the resin exemplified above as the resin used for the insulating protective layer can be contained. The adhesive resin composition may contain, for example, a thermoplastic resin or a thermosetting resin.

As a thermoplastic resin, a styrene-type resin, a vinyl acetate-type resin, a polyester-type resin, a polyethylene-type resin, a polypropylene-type resin, an imide-type resin, an amide-type resin, an acrylic resin, etc. are mentioned, for example. When the adhesive resin composition contains a thermoplastic resin, the thermoplastic resin contained in the adhesive resin composition preferably has a lower glass transition point and/or melting point than the thermoplastic resin contained in the insulating protective layer.

As a thermosetting resin, a phenol type resin, an epoxy type resin, a urethane type resin, a melamine type resin, an alkyd type resin, etc. are mentioned, for example. These resins can also be modified.

The adhesive resin composition may also optionally contain the above-mentioned conductive fillers or at least one of the following additives: for example, hardening accelerators, adhesion imparting agents, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoaming agents, adjusting agents Leveling agent, filler, flame retardant and viscosity modifier, etc.

The adhesive is not particularly limited as long as it is a resin having adhesive properties, and examples thereof include those composed of acrylic resins, urethane resins, and silicone resins. As the adhesive, one formed on the release film can be generally used.

The thickness of the adhesive layer is not particularly limited, but may be, for example, 1 μm or more and 20 μm or less. The thickness of the adhesive layer is preferably 4 μm or more, more preferably 5 μm or more. On the other hand, the thickness of the adhesive layer is preferably 9 μm or less, more preferably 8 μm or less. The thickness of the adhesive layer can be measured, for example, according to the thickness measurement method in the examples described later.

When the thickness of the adhesive layer is 1 μm or more, the transmission characteristics of the electromagnetic wave shielding film tend to be good. When the thickness of the adhesive layer is 20 μm or less, when the electromagnetic wave shielding film and the printed wiring board are bonded together, the projections of the shielding layer tend to easily pass through the adhesive layer and be connected to the ground circuit of the printed wiring board.

The thickness of the electromagnetic wave shielding film is not particularly limited, but may be, for example, 3 μm or more and 50 μm or less. The thickness of the adhesive layer is preferably 5 μm or more, more preferably 30 μm or more. On the other hand, the thickness of the adhesive layer is preferably 10 μm or less, more preferably 20 μm or less. The thickness of the adhesive layer is a value measured according to the thickness measurement method in the examples described later.

<Manufacturing method of electromagnetic wave shielding film> The manufacturing method of the electromagnetic wave shielding film may be, for example, a manufacturing method including a step of coating an insulating resin composition on a support substrate and curing it to form an insulating protective layer (hereinafter. Also referred to as the insulating protective layer forming step); the step of forming a shielding layer on the insulating protective layer (hereinafter also referred to as the shielding layer forming step); and the step of forming an adhesive layer on the shielding layer (hereinafter also referred to as the following agent layer step). The electromagnetic wave shielding film thus formed can be an electromagnetic wave shielding film of one aspect of the present invention.

(Insulating Protective Layer Forming Step) As the supporting base material, thermoplastic resins such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI) can be mentioned. ), polyamide (PA), polycarbonate (PC), polystyrene (PS) or polyphenylene sulfide (PPS). Among them, polyethylene terephthalate (PET) is preferable because of its flexibility and high heat resistance.

The thickness of the support substrate may be, for example, 10 μm or more and 10 mm or less, preferably 20 μm or more and 8 mm or less. As the support base, for example, a roll-shaped support base can be continuously used while being rolled out, or a single piece that has been cut in advance may be used.

A release agent layer may also be provided between the support substrate and the insulating protective layer. As a release agent, a fluorine resin, a polyester resin, a silicone resin, a melamine resin etc. are mentioned, for example.

The insulating resin composition can be used as exemplified in the description of the insulating protective layer in the electromagnetic wave shielding film above. The insulating resin composition may optionally contain at least one solvent, such as toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, dimethylformamide, and the like. The insulating resin composition can be obtained by a well-known manufacturing method, for example, by mixing and preparing each component and a solvent together. In order to provide unevenness on the surface of the shield layer on the adhesive layer side, an insulating resin composition containing particulate matter is preferably used.

As a method of coating the insulating resin composition on one side of the support substrate, for example, a die coating method, a notch wheel coating method, a gravure coating method, and a slit die coating method can be used.

After coating the insulating resin composition, the solvent may be removed by heating and/or drying under reduced pressure as necessary.

When the insulating resin in the insulating resin composition is a thermosetting resin, the insulating resin composition can be cured by heating after drying. Heating can be performed using, for example, an infrared irradiation furnace, a hot air oven, or the like.

When the insulating resin is an active energy ray curable resin, the insulating resin composition can be cured by irradiating an active energy ray after drying. The active energy rays may be, for example, ultraviolet rays, electron beams, infrared rays, or the like. Among them, ultraviolet rays are preferable. Irradiation of ultraviolet rays can be performed using, for example, light sources such as high-pressure mercury lamps, metal halide lamps, low-pressure mercury lamps, and ultra-high pressure mercury lamps.

The support base material can be peeled off after drying and/or curing the insulating resin composition, or peeling off after the electromagnetic wave shielding film is pasted on the printed wiring board.

Regardless of the presence or absence of particulate matter in the insulating protective composition, at least the surface on the shield layer side of the insulating protective layer may be made uneven. When the surface on the shield layer side of the insulating protective layer is roughened, a shield layer having a predetermined RSm tends to be easily obtained.

As a method of making the surface of the insulating protective layer uneven, for example, the following methods are mentioned: a method of using an insulating protective composition containing a particulate substance; dry etching by sandblasting, plasma irradiation or electron beam irradiation, A method of treating the surface of the formed insulating protective layer by chemical treatment such as wet etching or embossing; a method of sprinkling particulate matter on the formed coating film of the insulating resin composition; A method of applying an insulating resin composition after sprinkling a particulate matter; a method of applying an insulating resin composition to the surface of a support substrate having a concavo-convex shape on the surface.

When providing unevenness|corrugation on the surface of the shield layer side of an insulating protective layer using the insulating protective composition containing a particulate-form substance, the particulate-form substance which has an insulating property can be used as a particulate-form substance. Examples of the insulating particulate matter include inorganic particles, for example, silica, alumina, and the like, and resin particles. The particulate matter can be used alone or in combination of two or more.

The average particle diameter (D50) of the particulate matter to be used can be appropriately determined according to the surface roughness on the shield layer side in the insulating protective layer. The average particle diameter of the particulate matter may be, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 13 μm or more, and particularly preferably 15 μm or more. On the other hand, the average particle diameter of the particulate matter may be, for example, 50 μm or less, preferably 40 μm or less, more preferably 35 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. When the average particle diameter of the particulate matter is 1 μm or more and 50 μm or less, there is a tendency that the surface of the insulating protective layer on the shielding layer side tends to be appropriately uneven and the RSm of the surface on the adhesive layer side of the shielding layer is 40 μm It is more than 100 micrometers or less, and it is easy to make the thickness of an electromagnetic wave shielding film suitable. The average particle diameter of the particulate matter is a value measured in accordance with the average particle diameter measuring method in the examples described later.

When the insulating resin composition contains the particulate matter, the content of the particulate matter in the insulating resin composition may be, for example, 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the resin component. When the insulating resin composition contains particulate matter, the content of the particulate matter in the insulating resin composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 100 parts by mass of the resin component. It is 20 mass parts or more. On the other hand, when the insulating resin composition contains particulate matter, the content of the particulate matter in the insulating resin composition is preferably 90 parts by mass or less, preferably 80 parts by mass or less, relative to 100 parts by mass of the resin component. More preferably, it is 60 parts by mass or less. When the insulating resin composition contains the particulate matter in an amount of 1 part by mass or more and 100 parts by mass or less, the surface of the insulating protective layer can be easily unevenly formed, and the RSm of the adhesive layer side surface of the shielding layer can be easily made. A tendency of 40 μm or more and 100 μm or less.

The shape of the particulate matter is not particularly limited, and may be spherical, needle-like, fibrous, platelet-like, and dendritic. From a viewpoint, spherical shape is preferable.

When the insulating resin composition contains particulate matter, the thickness of the insulating protective layer may be, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, the thickness of the insulating protective layer may be, for example, 30 μm or less, preferably 28 μm or less, more preferably 25 μm or less, and still more preferably 23 μm or less.

For example, in the treatment by sandblasting, the surface of the support substrate may be sprayed with an abrasive, such as beads, sand, dry ice, or the like, to be uneven. For example, in the treatment by embossing, the surface of the insulating protective layer can be given a concavo-convex shape by pressing a mold having a concavo-convex shape.

When the surface on the shield layer side of the insulating protective layer is made uneven, for example, the average length RSm of the roughness curve element on the shield layer side surface of the insulating protective layer may be 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less. . When the RSm of the shield layer side surface of the insulating protective layer is 100 μm or less, it is preferable because the RSm of the adhesive layer side surface of the shield layer tends to be 40 μm or more and 100 μm or less.

(Shield Layer Forming Step) The shield layer can be formed by forming a metal film on the surface of the insulating protective layer. The metal film can be formed by an additive method such as an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a CVD method, or a metal-organic method, or a method of bonding a metal foil. and so on. Among them, an electrolytic plating method or an electroless plating method is preferable. When a metal film is formed by an electrolytic plating method or an electroless plating method, dendritic fine irregularities are easily formed on the surface of the metal film, and the shield layer and the ground circuit of the printed wiring board tend to be easily connected. The metal film may consist of the metals mentioned above with respect to the shielding layer.

When the insulating protective layer contains fillers to form concavities and convexities on the surface of the insulating protective layer, and the shielding layer is formed on the concavo-convex surface by an additive method, the preferred additive methods are electrolytic plating and electroless plating. A well-known method can be employ|adopted for the electrolytic plating method. For example, the electrolyte should be copper sulfate, and the current should be applied for 60 seconds to 6 minutes at a temperature of 25°C to 40°C. As the electroless plating method, a known method can be used. The catalyst in the electrolytic plating method is preferably a metal nanoparticle, and the catalyst is preferably carried out at a temperature of 45° C. to 60° C. for 60 seconds to 5 minutes. When the insulating protective layer contains filler to form unevenness on the surface of the insulating protective layer, and the shielding layer is formed on the uneven surface by an additive method, the thickness of the shielding layer is not particularly limited, and it is preferably 0.1 to 15 μm, more preferably It is 0.1-1 micrometer, More preferably, it is 0.1-0.5 micrometer. When the thickness of the shielding layer is within the above-mentioned range, it tends to be easy to obtain a shielding layer having substantially the same shape as the uneven shape on the surface of the insulating protective layer.

By making the surface of the metal film uneven after forming the metal film, the RSm of the adhesive layer side surface of the shielding layer can also be set to be 40 μm or more and 100 μm or less. As a method of making the surface of the metal film uneven, for example, a method of processing by sandblasting, dry etching by plasma irradiation or electron beam irradiation, wet etching by chemical treatment, or embossing, etc. . Moreover, when performing the method of bonding a metal foil, the method of bonding the copper foil which provided the uneven|corrugated shape on the surface by embossing, etc., is mentioned, for example.

The shielding layer may be formed of electroconductive particles. About the method of forming a shielding layer from electroconductive particle, the method of forming by apply|coating the electroconductive paste containing electroconductive particle to the surface of the insulating protective layer, the method of forming by coating the electroconductive particle on the surface of the insulating protective layer, method etc. As a method of apply|coating the electroconductive paste containing electroconductive particle, a die coating method, a corner wheel coating method, a gravure coating method, a slit die coating method, etc. are mentioned, for example. After apply|coating the electroconductive paste containing electroconductive particle, drying process, hardening process, etc. are performed as needed.

(Adhesive Layer Forming Step) The adhesive layer may be constituted by an adhesive or an adhesive.

When the adhesive layer is composed of an adhesive, it can be formed by applying the adhesive to the barrier layer. As a method of apply|coating an adhesive agent to a shield layer, a die-tip coating method, a corner wheel coating method, a gravure coating method, a slit die coating method, etc. are mentioned, for example. As an adhesive agent, the above-mentioned thermoplastic resin composition, thermosetting resin composition, etc. are mentioned. After applying the adhesive, drying treatment, hardening treatment, and the like may be performed as necessary. In order to protect the surface of the adhesive layer before bonding with the printed wiring board, a release film may be bonded to the surface of the adhesive layer.

Moreover, when an adhesive agent layer is comprised with an adhesive agent, an adhesive agent layer can also be formed by sticking the adhesive agent side surface of the release film which apply|coats an adhesive agent with the surface of a shielding layer. The peeling film can be peeled off when it is bonded to a printed wiring board.

When the adhesive layer is composed of an adhesive, the adhesive layer can usually be formed by sticking the adhesive formed on the release film to the surface on the side of the shielding layer. The peeling film can be peeled off when it is bonded to a printed wiring board.

In the electromagnetic wave shielding film thus obtained, even if the adhesive layer does not contain a conductive filler, when the electromagnetic wave shielding film and the printed wiring board are pasted together, the convex portion of the shielding film can be connected to the ground circuit of the printed wiring board, and good performance can be exhibited. transfer characteristics. Moreover, since the conductive filler is not contained, the shielding film can be made thinner.

<Shielded printed wiring board> A shielded printed wiring board can be produced by bonding an electromagnetic wave shielding film to a printed wiring board.

FIG. 4 shows a shielded printed wiring board 300 according to an aspect of the present invention. As shown in FIG. 4 , the shielded printed wiring board 300 includes the electromagnetic wave shielding film 100 and the printed wiring board 200 . The printed wiring board 200 includes a base layer 210 , a ground circuit 220A and a signal circuit 220B formed on the base layer 210 , and an insulating layer 230 covering the base layer 210 so as to expose at least a part of the ground circuit 220A. A part of the convex portion of the shielding layer 120 passes through the adhesive layer 130 and is in contact with the ground circuit 220A. Therefore, even if the adhesive layer 130 does not contain a conductive filler, the shielding layer 120 and the ground circuit 220A can be electrically connected, and excellent shielding properties can be exhibited. In addition, since the RSm of the adhesive-side surface of the shielding layer 120 is 100 μm or less, the adhesive is stored in the concave portion of the shielding layer 120 , and the adhesive layer 130 can be sufficiently secured between the shielding layer 120 and the printed wiring board 200 . Therefore, good transmission characteristics can be exhibited. A high frequency signal is transmitted to the signal circuit 220B. The so-called high frequency refers to, for example, the region from 100MHz (extremely long and short wave) to 3000GHz (submillimeter wave), as long as it is the region of 100MHz to 100GHz used for signal transmission in printed wiring boards, the electromagnetic wave shielding film of the present invention is suitable for use .

(Printed Wiring Board) The printed wiring board may have a base layer, an insulating layer, and a printed circuit. The base layer and the insulating layer may be, for example, a resin film or the like. The resin film may be composed of resins such as polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, polyetherimide, or polyphenylene sulfide.

(Printed Circuit) The printed circuit may be, for example, a copper wiring pattern or the like formed on the base layer. The printed circuit may have a signal circuit and a ground circuit.

The electromagnetic wave shielding film can be bonded to the printed wiring board by placing the adhesive layer on the printed wiring board side. For example, the shielded printed wiring board can be bonded by placing an electromagnetic wave shielding film on the printed wiring board, and heating and pressing with a press. During pressurization, at least a part of the convex portion of the shielding layer passes through the adhesive layer and is connected to the ground circuit so as to be conductive. Moreover, even when pressurization is performed, since the adhesive agent fully exists in the recessed part of a shield layer, favorable transmission characteristics can be obtained.

Since the shielded printed wiring board of one aspect of the present invention can exhibit good transmission characteristics, it is suitable for use in smart phones, tablet terminals, personal computers, etc. that need to transmit a large amount of data at high speed.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

EXAMPLES Each characteristic value in the electromagnetic wave shielding film obtained in the Example and the comparative example was measured by the following method.

<Measurement of RSm> RSm was measured for the shielding layers obtained in the respective Examples and Comparative Examples. Specifically, after measuring five arbitrary points on the surface of the shielding layer using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times), the surface properties were measured according to JIS B 0601:2013 using data analysis software (LMeye7) to obtain the Arithmetic mean. In addition, the cutoff wavelength λc was set to 0.8 mm.

<Measurement of Smr2> Smr2 was measured for the shielding layers obtained in the respective Examples and Comparative Examples. Specifically, after measuring five arbitrary points on the surface of the shielding layer using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times), the surface properties were measured according to ISO 25178-6:2010 using data analysis software (LMeye7) to obtain its arithmetic mean. In addition, the cutoff wavelength of the S filter was set to 0.0025 mm, and the cutoff wavelength of the L filter was set to 0.8 mm.

<Measurement of Smr1> Smr1 was measured for the shielding layers obtained in the respective Examples and Comparative Examples. Specifically, after measuring five arbitrary points on the surface of the shielding layer using a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20 times), the surface properties were measured according to ISO 25178-6:2010 using data analysis software (LMeye7) to obtain its arithmetic mean. In addition, the cutoff wavelength of the S filter was set to 0.0025 mm, and the cutoff wavelength of the L filter was set to 0.8 mm.

<Measuring the average particle size> SALD-2200 manufactured by Shimadzu Corporation Co., Ltd. was measured at an absorbance of 30%, and the average particle size was determined.

<Measurement of thickness> The thickness of the adhesive layer is an image obtained by observing the cross section of the electromagnetic wave shielding film at 1000 times with an electron microscope (JSM-6510LA, manufactured by JEOL Ltd.), and the thickness of the adhesive layer is calculated by averaging 5 points. .

<Evaluation of Connectivity> After temporarily sticking an electromagnetic wave shielding film (120°C, 0.5MPa, 5 seconds) on the surface of a printed wiring board, heat and pressure (170°C, 3MPa, 30 minutes) were performed to form a shielded printed wiring board. A printed wiring board having two copper foil patterns extending in parallel with an interval therebetween and an insulating layer made of polyimide having a thickness of 25 μm and covering the copper foil patterns were used. The insulating layer is provided with openings exposing the respective copper foil patterns. The diameter of the opening was 1 mm. By measuring the resistance value between two copper foil patterns with an electrical resistance meter, the connectivity between the copper foil pattern and the electromagnetic wave shielding film was evaluated. When the resistance was less than 0.4Ω, the connectivity was considered to be good.

<Frequency Characteristics> The frequency characteristics of the electromagnetic wave shielding film were evaluated using the network analyzer 31 shown in FIG. 5 . As the network analyzer 31, ZVL6 manufactured by Rohde & Schwarz was used. The network analyzer 31 has input terminals and output terminals, which are connected to the connection substrate 32, respectively. The measurement is performed after the shield printed wiring board 60 to be measured is connected between the pair of connection substrates 32 so as to be supported in a linear state floating in the air. As the shield printed wiring board 60, a length of 200 mm was used. In addition, the measurement was performed in a frequency range of 100 kHz to 6 GHz. In addition, the measurement is performed in a gas environment with a temperature of 25° C. and a relative humidity of 30 to 50%. The network analyzer 31 measures how much the input signal is attenuated relative to the output signal at a frequency of 10 GHz. The measured attenuation is shown in Table 2 as transmission loss. The closer the attenuation is to zero, the lower the transmission loss.

<Preparation of a shielded printed wiring board> An insulating film of 37.5 μm formed by adding a polyimide film with a thickness of 12.5 μm and an adhesive layer with a thickness of 25 μm was used for the printed wiring board. Moreover, what performed the copper plating of 6 micrometers with respect to the copper foil of 12 micrometers was used for the circuit pattern. No ground circuit is included in the circuit pattern. In addition, a 25 μm polyimide film was used for the base film.

The electromagnetic wave shielding films obtained in the respective Examples and Comparative Examples were bonded to a printed wiring board, heated to 170° C., and a shielded printed wiring board was obtained with a pressure of 3 MPa.

<Adhesive resin composition 1> The following raw material was added in the following ratio to the 1000 ml flask with a stirring apparatus, and it prepared by stirring and dissolving it at room temperature for 6 hours. [Epoxy resin] Cresol novolac epoxy resin (manufactured by DIC Corporation, EPICLON N-655-EXP): 100 parts by mass [Imidazole-based hardening accelerator] manufactured by Shikoku Chemical Corporation, CUREZOL C11-Z: 0.2 part by mass [ Solvent] methyl ethyl ketone: 400 parts by mass

<Example 1> The insulating resin composition prepared with the respective components and amounts shown in Table 1 was coated on a PET film (thickness 50 μm) on which a polyester-based release agent was formed on the surface, followed by drying. Thereby, the insulating protective layer of the uneven surface is formed. The average particle diameter of the inorganic particles was 16.7 μm. The thickness of the insulating protective layer was measured. The results are shown in Table 2. Table 2 shows the RSm of the obtained insulating protective layer.

On the uneven surface of the formed insulating protective layer, a copper plated layer with a thickness of 2 μm was formed by plating to form a shielding layer of the uneven surface. The copper plating layer was formed by the electrolytic plating method under the following conditions. In the electrolytic plating method, the electrolytic solution used was copper sulfate, and a current was applied at a temperature of 25° C. for 6 minutes. RSm, Smr2, and Smr1 of the surface of the obtained shielding layer on which the adhesive layer is provided were measured. The results are shown in Table 2.

The adhesive resin composition 1 prepared as described above was applied to the surface of the shielding layer on the obtained uneven surface, followed by drying to prepare an adhesive layer, thereby obtaining an electromagnetic wave shielding film. Table 2 shows the thickness of the adhesive layer.

<Example 2> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the inorganic particle compounding amount used in Example 1 was replaced by 42.9 parts by mass relative to the resin solid content.

<Example 3> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the thickness of the insulating protective layer was replaced with 23 μm.

<Example 4> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the thickness of the insulating protective layer was replaced by 30 μm, and the inorganic particles were replaced by inorganic particles having an average particle diameter of 27.3 μm.

<Comparative Example 1> The insulating resin composition prepared with the components and amounts shown in Table 1 was applied on a PET film (thickness 50 μm) on which a polyester-based release agent was formed on the surface, followed by drying. Thereby, an insulating protective layer with a thickness of 5 μm was formed. Then, the 2-micrometer-thick copper foil produced by rolling was bonded to the insulating protective layer. Then, a liquid conductive adhesive composition having a solid content concentration of 20% was prepared by adding 17.6 parts by mass of silver-coated copper powder having a center particle diameter D50 of 13 μm to 100 parts by mass of the adhesive resin composition 1 have to. The above-mentioned liquid conductive adhesive composition was applied on copper foil using a doctor blade (plate spatula), and dried under the conditions of 100° C.×3 minutes to form a conductive adhesive layer. Thereby, a shielding film having a structure of insulating protective layer/metal layer/adhesive layer is produced.

<Comparative Example 2> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the inorganic particle compounding amount used in Example 1 was replaced by 100 parts by mass relative to the resin solid content.

<Comparative Example 3> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the inorganic particles used in Example 1 were replaced with inorganic particles having an average particle diameter of 20.7 μm.

<Comparative Example 4> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the compounding amount of the inorganic particles used in Comparative Example 1 was 42.9 parts by mass with respect to the resin solid content.

<Comparative Example 5> An electromagnetic wave shielding film was obtained in the same manner as in Example 1, except that the compounding amount of the inorganic particles used in Comparative Example 1 was 100 parts by mass with respect to the resin solid content.

單位：質量份[Table 1]

Unit: parts by mass

[Epoxy resin] Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical, jER1256): 100 parts by mass epoxy resin hardener (manufactured by Mitsubishi Chemical, ST14): 0.1 part by mass [Inorganic particle A] Porous silica particles : Average particle size 16.7μm [Inorganic particle B] Porous silica particle: Average particle size 20.7μm [Inorganic particle C] Porous silica particle: Average particle size 27.3μm

*OL：過負荷(超過測定範圍)[Table 2]

*OL: Overload (out of measurement range)

As can be seen from Table 2, compared with Comparative Examples 1 to 5, Examples 1 to 4 have lower attenuation of the transmission signal and less transmission loss.

31‧‧‧Network Analyzer 32‧‧‧Substrate for connection 60‧‧‧Shielding printed wiring board 100‧‧‧Electromagnetic wave shielding film 110‧‧‧Insulating layer 120‧‧‧Shielding layer 130‧‧‧Adhesive layer 200 ‧‧‧Printed wiring board 210‧‧‧Base layer 220A‧‧‧Ground circuit 220B‧‧‧Signal circuit 230‧‧‧Insulation layer 300‧‧‧Shielded printed wiring board

FIG. 1 is a schematic cross-sectional view showing a typical electromagnetic wave shielding film of one aspect of the present invention. FIG. 2 is a schematic diagram showing the mean length RSm of the roughness curve elements. FIG. 3 is a diagram conceptually showing the load area ratios Smr1 and Smr2. 4 is a schematic cross-sectional view of a shielded printed wiring board according to an aspect of the present invention. Fig. 5 is a system configuration diagram for measuring frequency characteristics.

Claims (5)

A shielding printed wiring board, comprising an electromagnetic wave shielding film and a printed wiring board; the electromagnetic wave shielding film has an insulating protective layer, a shielding layer and an adhesive layer; the printed wiring board has a base layer, an electrical circuit formed on the base layer and A signal circuit and an insulating layer, and the insulating layer covers the base layer in such a way that at least a part of the ground circuit is exposed; the electromagnetic wave shielding film is attached to the printed wiring board through the adhesive layer, and the adhesive in the shielding layer The average length RSm of roughness curve elements according to JIS B 0601:2013 on the side surface of the adhesive layer is 40 μm or more and 100 μm or less; the thickness of the adhesive layer is 1 μm or more and 20 μm or less; the adhesive layer does not contain conductive fillers; At least the side surface of the shielding layer of the insulating protective layer is concave and convex; and a part of the convex part of the shielding layer passes through the adhesive and is connected to the grounding circuit. The shielded printed wiring board according to claim 1, wherein the load area ratio Smr2 of the side surface of the adhesive layer in the shield layer is 92% or more. The shielded printed wiring board according to claim 1 or 2, wherein the insulating protective layer contains particulate matter. The shielded printed wiring board according to claim 3, wherein the average particle diameter of the particulate matter is 15 μm or more. A method of manufacturing a shielded printed wiring board, which is a method of manufacturing a shielded printed wiring board as claimed in any one of claims 1 to 4, comprising the steps of: coating a support substrate with an insulating resin composition and curing it to obtaining an insulating protective layer; forming a shielding layer on the insulating protective layer; forming an adhesive layer on the shielding layer to obtain an electromagnetic wave shielding film; and laminating the obtained electromagnetic wave shielding film to a printed wiring board.

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