JP2013168643A - Electromagnetic wave shield sheet and manufacturing method of wiring board with electromagnetic wave shield layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shield sheet which exhibits high electromagnetic wave shielding properties while ensuring excellent impedance matching in a wiring board with an electromagnetic wave shield layer, by thinning the electromagnetic wave shield layer and providing a conductive layer having a plurality of apertures in the electromagnetic wave shield sheet, and setting the shape and opening ratio of the apertures appropriately in a wiring board with an electromagnetic wave shield layer where an electromagnetic wave shield sheet is bonded to the wiring board and a conductive adhesive layer is omitted.SOLUTION: The electromagnetic wave shield sheet used while being bonded to a wiring board having signal wiring includes an insulating bonding layer containing a thermosetting resin composition having a glass transition temperature of 0-150°C and flowable under conditions of 150°C temperature and 1 kg/cmpressure, and a conductive layer provided on one surface of the bonding layer and having a plurality of apertures.

Description

  The present invention is an electromagnetic wave shielding sheet that is used by being attached (bonded) to a wiring board such as a printed wiring board. Even when the wiring board is thin, the electromagnetic noise generated from the electric circuit or signal wiring is shielded and desired. The present invention relates to an electromagnetic wave shielding sheet capable of obtaining the characteristic impedance and a method of manufacturing a wiring board with an electromagnetic wave shielding layer using the electromagnetic wave shielding sheet.

Electronic devices such as digital cameras and mobile phones are becoming smaller and thinner. Accordingly, printed wiring boards mounted on these electronic devices are also required to be reduced in size and thickness. The printed wiring board generally has an electromagnetic wave shielding layer for noise reduction (hereinafter, a printed wiring board having an electromagnetic wave shielding layer is referred to as “printed wiring board with an electromagnetic wave shielding layer”).
Furthermore, in recent years, “CISPR22”, an international standard for radiated electromagnetic noise (EMI), has been revised, and the upper limit frequency of electromagnetic noise to be suppressed has been expanded from 1 GHz to 6 GHz. Is required.
On the other hand, a wiring circuit (signal wiring) of a printed wiring board is required to transmit a high-speed and large-capacity signal, and a signal flowing through the wiring circuit needs to have higher frequency. Then, in order to suppress signal reflection and waveform distortion, it is necessary to match the input / output impedance of the circuit element connected to the printed wiring board and the characteristic impedance of the printed wiring board.
The characteristic impedance is represented by the following equation 1, the reactance L per unit length of the wiring circuit, and the capacitance per unit area between the conductive material such as the electromagnetic shielding layer and the ground circuit and the wiring circuit. It is approximated by the square root of C.
Characteristic impedance ≒ (L / C) ^0.5 ... Formula (1)

However, in recent printed wiring boards, the thickness of the wiring circuit is further reduced for the purpose of reducing the size and thickness of electronic devices. As a result, in the printed wiring board with an electromagnetic wave shielding layer, the interval between the wiring circuit and the electromagnetic wave shielding layer is narrowed, and the capacitance tends to increase.
Therefore, in order to obtain a desired characteristic impedance, it is necessary to form the wiring circuit so that the width of the wiring circuit becomes narrower, and to suppress an increase in capacitance of the printed wiring board with the electromagnetic wave shielding layer. However, it is technically difficult to significantly reduce the width of the wiring circuit, and there is a problem that a stable characteristic impedance cannot be obtained in a printed wiring board with an electromagnetic wave shielding layer.

  Therefore, it has been proposed to adjust the characteristic impedance of the printed wiring board with the electromagnetic shielding layer by forming an opening in the electromagnetic shielding layer and appropriately setting the area where the wiring circuit and the electromagnetic shielding layer overlap (patent) Reference 1).

JP 2006-24824 A

However, as shown in FIG. 1, the electromagnetic wave shield sheet 9 of Patent Document 1 has an insulative film 91, an opening metal layer 92, and a conductive adhesive layer 93 as essential components. The electromagnetic wave shielding sheet 9 is adhered (bonded) to the printed wiring board so that the conductive adhesive layer 93 is in contact with the printed wiring board. Furthermore, in order to improve the shielding performance, it is necessary to separately laminate a shielding film on the insulating film 91, and the thickness of the entire electromagnetic wave shielding sheet 9 cannot be reduced.
Therefore, for example, when the electromagnetic wave shield 9 is used for a flexible printed wiring board (hereinafter also referred to as “FPC board”), there is a problem that the flexibility of the FPC board is hindered. In addition, since the thickness of the entire printed wiring board with the electromagnetic wave shielding layer formed by joining the electromagnetic wave shield 9 to the printed wiring board cannot be reduced, there is a problem that downsizing and thinning of an electronic device on which the wiring board is mounted are restricted. There is also.

In the electromagnetic wave shielding sheet of the present invention, since the conductive adhesive layer 91 can be omitted, in the wiring board with the electromagnetic wave shielding layer formed by bonding the electromagnetic wave shielding sheet to the wiring board, the thickness of the electromagnetic wave shielding layer is reduced. be able to. Furthermore, the electromagnetic wave shielding sheet includes a conductive layer having a plurality of openings, and the wiring board with the electromagnetic wave shielding layer exhibits high electromagnetic wave shielding properties by appropriately setting the shape and opening ratio of the openings. At the same time, good impedance matching can be achieved.
Therefore, an object of this invention is to provide the electromagnetic wave shield sheet which can exhibit the above characteristic.

The present invention is an electromagnetic wave shielding sheet used by adhering to a wiring board having a signal wiring, which contains a thermosetting resin composition having a glass transition temperature of 0 to 150 ° C., a temperature of 150 ° C. and a pressure of 1 kg / cm. ^{The present} invention relates to an electromagnetic wave shielding sheet comprising: a bonding layer having an insulating property capable of flowing under the condition ² ; and a conductive layer provided on one surface of the bonding layer and having a plurality of openings.
In the electromagnetic wave shielding sheet of the present invention, the conductive layer has an inner peripheral surface that defines each opening, and the length of the inner peripheral surface in the circumferential direction has a maximum frequency that is input to the signal wiring. It is preferable to set it to 1/4 or less.
The electromagnetic wave shielding layer-attached wiring board is provided so as to cover the substrate, the signal wiring and the ground wiring provided on the substrate, and the signal wiring and the ground wiring on the substrate. A wiring board having a first insulating layer having a through hole in which a portion is exposed;
An electromagnetic wave shielding layer provided on the wiring board, a part of which is directly connected to the ground wiring through the through hole, and includes a conductive layer having a plurality of openings, and covers the conductive layer and the plurality And an electromagnetic wave shielding layer having a second insulating layer that is filled in the opening of the wiring board and bonded to the first insulating layer of the wiring board.

  According to the present invention having the above configuration, the bonding layer of the electromagnetic wave shielding sheet flows under constant heating and pressurizing conditions. Therefore, this electromagnetic wave shielding sheet is superimposed on the wiring board so that the conductive layer and the wiring board are in contact, and when these are heated and pressurized, the bonding layer flows and adheres to the wiring board through the opening of the conductive layer. can do. That is, according to the present invention, the electromagnetic wave shielding sheet can be bonded to the wiring board with high bonding strength without using a conductive adhesive layer.

Moreover, since the conductive adhesive layer is unnecessary, the thickness of the entire electromagnetic wave shielding sheet can be reduced. Therefore, the thickness of the whole wiring board with an electromagnetic wave shielding layer formed by adhering the electromagnetic wave shielding sheet to the wiring board can also be reduced. Therefore, when the wiring board is, for example, an FPC board, it contributes to miniaturization and thinning of an electronic device on which the board is mounted while ensuring the flexibility of the board.
Furthermore, the electromagnetic wave shielding sheet includes a conductive layer having a plurality of openings. By appropriately setting the shape and aperture ratio of these openings, the electromagnetic wave shielding sheet can exhibit both the electromagnetic shielding properties and the impedance controllability of the wiring board with the electromagnetic shielding layer in a balanced manner.

  As described above, according to the present invention, in the wiring board with an electromagnetic wave shielding layer formed by bonding the electromagnetic wave shielding sheet to the FPC board, the thickness of the electromagnetic wave shielding layer can be reduced, and the electromagnetic wave shielding property and the impedance controllability can be obtained. Both of these characteristics are improved.

FIG. 1 is a perspective view schematically showing a conventional electromagnetic wave shielding sheet. FIG. 2 (a) is a plan view showing a preferred embodiment of the wiring board with an electromagnetic wave shielding layer of the present invention, and FIG. 2 (b) shows a preferred embodiment of the wiring board with an electromagnetic wave shielding layer of the present invention. FIG. FIG. 3 is a partially enlarged view showing a cross section of the wiring board with an electromagnetic wave shielding layer shown in FIG. FIG. 4 is a cross-sectional view of a preferred embodiment of the electromagnetic wave shielding sheet of the present invention. FIG. 5 is a plan view illustrating a configuration example of the conductive layer of the electromagnetic wave shielding sheet illustrated in FIG. 4. FIG. 6 is a plan view showing another configuration example of the conductive layer of the electromagnetic wave shielding sheet shown in FIG. 7 is a plan view showing another configuration example of the conductive layer of the electromagnetic wave shielding sheet shown in FIG. FIG. 8 is an enlarged plan view showing one of the plurality of openings provided in the conductive layer shown in FIG.

Hereinafter, an electromagnetic wave shielding sheet of the present invention, a manufacturing method of a wiring board with an electromagnetic wave shielding layer, and a wiring board with an electromagnetic wave shielding layer will be described based on preferred embodiments shown in the accompanying drawings.
The electromagnetic wave shielding sheet of the present invention has a function of blocking electromagnetic noise, and is used by being bonded (bonded or adhered) to a wiring board having signal wiring. By adhering the electromagnetic wave shielding sheet to the wiring board, electromagnetic noise from signals transmitted through the signal wiring and electromagnetic noise from other wiring boards installed adjacent to it are captured, and unnecessary signals are wired. Generation of signal wiring on the board can be prevented.

First, prior to the description of the electromagnetic wave shielding sheet of the present invention, the wiring board with an electromagnetic wave shielding layer of the present invention formed by bonding the electromagnetic wave shielding sheet of the present invention to the wiring board will be described.
Fig.2 (a) is a top view which shows suitable embodiment of the wiring board with an electromagnetic wave shield layer of this invention, FIG.2 (b) is the side view. Moreover, FIG. 3 is a figure which expands and shows partially the cross section which cut | disconnected the wiring board with an electromagnetic wave shield layer shown to Fig.2 (a) by XX. In the following description, the upper side in FIGS. 2B and 3 is referred to as “upper” or “upper”, and the lower side is referred to as “lower” or “lower”.

As shown in FIGS. 2 and 3, the wiring board 100 with an electromagnetic wave shielding layer of the present invention includes a printed wiring board 50 and an electromagnetic wave shielding layer 10 provided on the printed wiring board 50.
The printed wiring board 50 includes a substrate 60, a signal wiring 71 and a ground wiring 72, and a first insulating layer 80 that covers the signal wiring 71 and the ground wiring 72. The ground wiring 72 is connected to the housing of the device on which the electromagnetic wave shielding layer-equipped wiring board 100 is provided, and is grounded to the ground (reference potential point). In the first insulating layer 80, a via 81 for exposing a part of the ground wiring 72 is formed. The via 81 may be closed by a thin bottom without penetrating the first insulating layer 80 in a state before the electromagnetic wave shielding sheet 1 is bonded to the printed wiring board 50, and may constitute a recess, Further, it may be constituted by a through-hole penetrating the first insulating layer 80.
Examples of the printed wiring board 50 include a rigid wiring board, an FPC board, and a rigid flexible wiring board. In the present embodiment, a case where an FPC board is used as the printed wiring board 50 will be described.

As the substrate 60, for example, various films such as a polyimide film, a polyether nitrile film, a polyether sulfone film, and a polyphenylene sulfide film can be used. Among the above various films, the substrate 60 is particularly preferably a polyimide film having a thickness of about 5 to 25 μm. This is because such a polyimide film has excellent flexibility and heat resistance.
On the substrate 60, a plurality of (four in this embodiment) signal wirings 71 and one ground wiring 72 are provided. Each signal wiring 71 and ground wiring 72 are in a straight line and are provided so as to be substantially parallel to each other. Each signal wiring 71 and ground wiring 72 are made of, for example, aluminum, copper, gold, or an alloy containing these. Each signal wiring 71 and ground wiring 72 may each constitute a circuit. Further, the number of the signal wiring 71 and the ground wiring 72 can be appropriately selected according to the design of the printed wiring board 50.
A first insulating layer 80 is provided on the substrate 60 so as to cover the signal wiring 71 and the ground wiring 72. The first insulating layer 80 prevents the signal wiring 71 and the ground wiring 72 from coming into contact with the metal layer 3 of the electromagnetic wave shielding layer 10 to be described later and short-circuiting at unnecessary portions.
The first insulating layer 80 is formed with a via 81 in which a part of the ground wiring 72 is exposed, and a part of the conductive layer 3 of the electromagnetic wave shielding layer 10 to be described later is connected to the ground wiring through the via 81. 72. The first insulating layer 80 is made of various resin materials such as phenol resin and epoxy resin, for example. A through hole may be formed instead of the via. In the via (through hole) 81, a part of the ground wiring 72 is exposed, and a part of the conductive layer 3 of the electromagnetic wave shielding layer 10 to be described later is connected to the ground wiring 72 through the via 81.

Further, as shown in FIGS. 2A and 2B, terminal portions 731 and 732 exposed from the first insulating layer 80 are provided at both ends of each signal wiring 71 and ground wiring 72, respectively. It is formed integrally with the signal wiring 71 and the ground wiring 72. Circuit elements are connected to these terminal portions 731 and 732.
Reinforcing plates 41 and 42 are provided on the lower surface of the printed wiring board 50 at portions corresponding to the terminal portions 731 and 732. The reinforcing plates 41 and 42 are made of, for example, a hard resin material such as polycarbonate or polyphenylene sulfide. By providing the reinforcing plates 41 and 42 on the lower surface of the printed wiring board 50, even when stress is applied to the terminal portions 731 and 732 when the terminal portions 731 and 732 are connected to the circuit elements, those Deformation can be reliably prevented.
On the first insulating layer 80 of such a printed wiring board 50, the electromagnetic wave shielding layer 10 is provided.
The electromagnetic wave shielding layer 10 includes a conductive layer 3 having a plurality of openings 31 and a second insulating layer 20 that covers the conductive layer 3.
A part of the conductive layer 3 is connected to the ground wiring 72 through the via 81 of the first insulating layer 80. That is, a part of the conductive layer 3 constitutes a connection portion that is directly connected to the ground wiring 72. With such a configuration, after the conductive layer 3 captures an electromagnetic wave that generates an unnecessary signal in the signal wiring 71 and converts it into a current (charge), the current is transmitted to the shield wiring board 100 via the ground wiring 72. It can be discharged to the outside.
The second insulating layer 20 covers the conductive layer 3, fills the plurality of openings 31 included in the conductive layer 3, and is bonded to the first insulating layer 80. Thereby, the electromagnetic wave shielding layer 10 is bonded to the printed wiring board 50.
In the electromagnetic wave shielding layer-equipped wiring board 100 having such a configuration, the conductive layer 3 is provided so as to be in contact with the printed wiring board 50, and is further formed by the second insulating layer 20 filled in the opening 31 of the conductive layer 3. The conductive layer 3 is fixed to the printed wiring board 50. Therefore, the thickness of the entire wiring board 100 with the electromagnetic wave shielding layer can be sufficiently reduced.
Further, by appropriately setting the shape and opening ratio of the opening 31 of the conductive layer 3, the characteristic impedance in the wiring board 100 with the electromagnetic wave shielding layer is changed to the input / output impedance of the circuit element connected to the wiring board 100 with the electromagnetic wave shielding layer. Can be easily adjusted to be equal to As a result, it is possible to prevent the signal input to the electromagnetic wave shielding layer-equipped wiring board 100 (terminal portions 731 and 732) from being reflected to the circuit element side that outputs this signal. Can be suppressed.
Moreover, the 2nd insulating layer 20 is formed when the thermosetting resin composition contained in the joining layer 2 of the electromagnetic wave shield sheet 1 hardens | cures so that it may mention later. On the other hand, the first insulating layer 80 is made of a resin material as described above. Since the resin materials have high adhesion, the second insulating layer 20 is firmly bonded to the first insulating layer 80. Therefore, it is possible to reliably prevent the electromagnetic wave shield layer 10 from peeling from the printed wiring board 50. In particular, since the second insulating layer 20 is composed of a cured product of a thermosetting resin composition, high bonding strength can be obtained between the second insulating layer 20 and the first insulating layer 80.

Further, as shown in FIG. 3, a part of the second insulating layer 20 is also filled in the via 81 of the first insulating layer 80. With such a configuration, the contact area (junction area) between the second insulating layer 20 and the first insulating layer 80 increases. Therefore, the bonding strength between the second insulating layer 20 and the first insulating layer 80 can be further improved.
In particular, the second insulating layer 20 is pinned to the first insulating layer 80 by the portion filled in the via 81 of the second insulating layer 20. As a result, the second insulating layer 20 can be prevented from being displaced in the surface direction with respect to the first insulating layer 80. The via 81 only needs to be formed in one place of the first insulating layer 80, but is preferably formed in two or more places. Thereby, the position shift prevention effect with respect to the 1st insulating layer 80 of the 2nd insulating layer 20 is exhibited more notably.

Hereinafter, the electromagnetic wave shielding sheet 1 that becomes the electromagnetic wave shielding layer 10 when bonded to the printed wiring board 50 will be described.
FIG. 4 is a cross-sectional view of a preferred embodiment of the electromagnetic wave shielding sheet of the present invention. In the following description, the upper side in FIG. 4 is referred to as “upper” or “upper”, and the lower side is referred to as “lower” or “lower”.
As shown in FIG. 4, the electromagnetic wave shielding sheet 1 includes a bonding layer 2 having an insulating property that can flow under constant heating and pressurization conditions, and a conductive layer provided on the lower surface of the bonding layer 2 and having a plurality of openings 31. Layer 3. In addition, in this specification, the electromagnetic wave shield sheet 1 may be called an electromagnetic wave shield film or an electromagnetic wave shield tape. FIG. 4 is a cross-sectional view showing a preferred embodiment of the electromagnetic wave shielding sheet 1, but this drawing is only an example of the electromagnetic wave shielding sheet 1 and may be another embodiment. Furthermore, the electromagnetic wave shielding sheet 1 may have a layer configuration in which other layers are added.

The bonding layer 2 contains a thermosetting resin composition having a glass transition temperature of 0 to 150 ° C. (preferably 0 to 100 ° C., more preferably 0 to 60 ° C.). As a result, the bonding layer 2 flows under conditions of constant heating and pressurization, specifically, a temperature of 150 ° C. and a pressure of 1 kg / cm ² (preferably a temperature of 150 ° C. and a pressure of 5 kg / cm ² ). Designed to. In such a state that the electromagnetic wave shielding sheet 1 is superposed on the printed wiring board 50 so that the conductive layer 3 and the first insulating layer 80 are in contact with each other, by heating and pressing under the above conditions, the bonding layer 2 is It flows so as to fill the opening 31 of the conductive layer 3 and comes into contact with the first insulating layer 80. Thereafter, the bonding layer 2 is hardened by further heating and the second insulating layer 20 is formed, thereby being bonded to the first insulating layer 80. That is, the electromagnetic wave shielding sheet 1 and the printed wiring board 50 can be bonded. Thereby, according to this invention, the electromagnetic wave shield sheet 1 can be adhere | attached on the printed wiring board 50, without requiring a conductive adhesive layer.
As the thermosetting resin composition, a resin composition containing a thermosetting resin (thermosetting resin) alone, not thermosetting alone, but thermosetting by reaction with other components having a reactive functional group Examples thereof include a resin composition containing a possible resin and the other components, or a mixture thereof. In the electromagnetic wave shielding sheet 1, the thermosetting resin composition is in an uncured (unreacted) state, and is cured by heating when adhering to the printed wiring board 50 as described above.

The thermosetting resin is not particularly limited, and examples thereof include an epoxy resin, a phenol resin, a cresol resin, a melamine resin, a polyester resin, and a polyamide resin.
Note that polyimide resins and polyamideimide resins, which are a kind of thermosetting resin, have low fluidity at the processing temperature. Therefore, when the electromagnetic wave shielding sheet 1 is bonded to the printed wiring board 50, depending on the opening ratio of the conductive layer 3 or the like, it is difficult to sufficiently fill the bonding layer 2 in the opening 31 of the conductive layer 3. There is. In this case, it becomes difficult to obtain sufficient bonding strength between the bonding layer 2 and the first insulating layer 80. Therefore, as the thermosetting resin, the resins listed above are preferable.
In addition, the resin that can be thermoset by reaction with other components is not particularly limited, but, for example, a chemical structure capable of reacting with a reactive functional group possessed by other components such as urethane resins and urethane urea resins. A resin having On the other hand, examples of other components include epoxy resins.
Among the resins described above, in consideration of harsh conditions when manufacturing an electronic device on which the printed wiring board 50 is mounted (for example, during reflow), the thermosetting resin composition is an epoxy resin, a polyester resin, or a urethane. It is preferable that at least one of a series resin and a urethane urea series resin is included, and it is more preferable that at least one of an epoxy series resin, a urethane series resin, and a urethane urea series resin is contained.
Moreover, it is preferable that the thermosetting resin composition contains the hardening | curing agent in addition to resin mentioned above. Examples of such a curing agent include, but are not limited to, phenolic curing agents such as phenol novolac resin, and amine curing agents such as dicyandiamide and aromatic diamine.

  The thermosetting resin composition may further contain a thermoplastic resin. Such a thermoplastic resin is not particularly limited, and examples thereof include polyurethane, polyester, polystyrene, polyolefin, polyamide and the like.

Furthermore, the thermosetting resin composition may contain a colorant, a flame retardant, an inorganic additive, a lubricant, an antiblocking agent, and the like.
Examples of the colorant include organic pigments, carbon black, ultramarine blue, petals, zinc white, titanium oxide, and graphite.
Examples of the flame retardant include a halogen-containing flame retardant, a phosphorus-containing flame retardant, a nitrogen-containing flame retardant, and an inorganic flame retardant.
Examples of the inorganic additive include glass fiber, silica, talc, and ceramic.
Examples of the lubricant include fatty acid esters, hydrocarbon resins, paraffin, higher fatty acids, fatty acid amides, aliphatic alcohols, metal soaps, and modified silicones.
Examples of the anti-blocking agent include calcium carbonate, silica, polymethylsilsesquiosan, aluminum silicate salt and the like.

  The thickness of the bonding layer 2 is sufficient to fill the opening 31 of the conductive layer 3, and the bonding layer 2 (second insulating layer 20) and the first insulating layer 80 of the printed wiring board 50 are practical. There is no particular limitation as long as adhesion is performed with a required bonding strength. However, although the thickness of the bonding layer 2 depends on the thickness of the conductive layer 3, it is practically preferably about 1 to 40 μm, more preferably about 1 to 20 μm, and further preferably about 3 to 15 μm. Thereby, the joining layer 2 which was excellent in all of insulation, the adhesiveness to the printed wiring board 50, and a softness | flexibility can be obtained.

  As described above, the conductive layer 3 has a plurality of openings 31 (opening). By appropriately setting the shape and the aperture ratio of the opening 31, the electromagnetic wave shielding sheet 1 exhibits excellent impedance controllability according to the design of the printed wiring board 50 and is excellent in the wiring board 100 with the electromagnetic wave shielding layer. Excellent electromagnetic shielding properties.

5 is a plan view showing a configuration example of the conductive layer of the electromagnetic wave shielding sheet shown in FIG. 4, and FIGS. 6 and 7 are plan views showing other configuration examples of the conductive layer of the electromagnetic wave shielding sheet shown in FIG. FIG. 8 is an enlarged plan view showing one of the plurality of openings provided in the conductive layer shown in FIG.
The opening 31 of the conductive layer 3 is designed to have a shape capable of efficiently capturing electromagnetic waves generated from the printed wiring board 50 (signal wiring 71) and electromagnetic waves entering from the outside. The shape of the opening 31 (planar shape of the opening 31) when such a conductive layer 3 is viewed from above is polygonal (n-gonal, n = about 3 to 300), circular, star-shaped, trapezoidal, etc. There are various shapes.
In the conductive layer 3 shown in FIG. 5, square-shaped openings 31 having the same shape are arranged in a matrix at equal intervals, and form a mesh shape (lattice shape) as a whole. The conductive layer 3 shown in FIG. 6 has hexagonal openings 31 having the same shape arranged at equal intervals, and has a honeycomb shape as a whole. Further, the conductive layer 3 shown in FIG. 7 includes a row in which the first openings 31a having the same triangular shape are linearly arranged, and a second opening portion 31b having the same shape in the inverted triangle is linearly arranged. The rows are alternately arranged. That is, in the conductive layer 3 shown in FIG. 7, a certain unit of the combination of the openings 31 is repeatedly arranged like the combination of the first openings 31a and the second openings 31b.
Among these, the mesh-like conductive layer 3 as shown in FIG. 5 is preferable. Since the conductive layer 3 is in a uniform opening state (opening shape), it has an advantage that the impedance controllability can be easily adjusted and that the manufacturing is easy (productivity is good). As described above, the planar shape of the opening 31 is preferably the same. Thereby, the aperture ratio of the conductive layer 3 can be easily adjusted. Note that “the same planar shape” includes not only the case where all the planar shapes of the plurality of openings 31 are completely the same, but also the case where the planar shapes of the plurality of openings 31 are approximate.
Further, as described above, the openings 31 are preferably arranged at equal intervals. Thereby, electromagnetic waves can be captured by the whole conductive layer 3 without deviation. Therefore, the electromagnetic wave shielding property in the entire wiring board 100 with the electromagnetic wave shielding layer can be further stabilized. The “equal interval” includes not only the case where the intervals between the openings 31 are exactly the same, but also the case where there is some variation in the intervals between the openings 31.

  In the electromagnetic wave shielding sheet 1, as shown in FIG. 4, it is preferable that the plane area of the bonding layer 2 and the plane area of the conductive layer 3 including the plane area of the opening 31 are the same (match). . In other words, it is preferable that the outer shape and size of the bonding layer 2 and the conductive layer 3 are the same. The plane area of the portion (non-opening portion) excluding the opening portion 31 of the conductive layer 3 can be appropriately set because the characteristic impedance is adjusted according to the printed wiring board 50. However, in the conductive layer 3 used for the printed wiring board 50 through which a high-frequency signal flows, when the plane area of the bonding layer 2 is 100, the plane area of the non-opening portion is a ratio of 0.05 to 0.8. A ratio of 0.05 to 0.6 is more preferable. Thereby, the characteristic impedance of the wiring board 100 with an electromagnetic wave shield layer can be adjusted regardless of the shape of the conductive layer 3.

Further, in one opening 31 of the conductive layer 3 shown in FIG. 8, the circumferential length of the inner peripheral surface defining the opening 31 (inner peripheral length of the opening 31) is the signal of the printed wiring board 50. 1 of the wavelength of the signal having the maximum frequency input to the wiring 71 and the signal having the maximum frequency among the signals generating the electromagnetic waves entering from the outside (that is, the signal having the maximum frequency among the signals from which the electromagnetic waves are generated). / 4 or less is preferable.
For example, a high frequency signal having a maximum frequency of 2.5 to 7.5 GHz band is used as a signal input to the signal wiring 71. If the frequency is a high-frequency signal in the 2.5 GHz band, the wavelength is approximately 120 mm, and if the frequency is a high-frequency signal in the 7.5 GHz band, the wavelength is approximately 40 mm.
Therefore, if the maximum frequency of the signal input to the signal wiring 71 is about 2.5 GHz, the inner peripheral length of the opening 31 is preferably 30 mm or less, which is 1/4 or less of the wavelength of the high-frequency signal. . On the other hand, when a high-frequency signal having a frequency of 7.5 GHz is input to the signal wiring 71, the inner peripheral length of the opening 31 is preferably 10 mm or less, which is ¼ or less of the wavelength of the high-frequency signal. . By satisfying the above conditions, the electromagnetic wave shielding sheet 1 can easily control the impedance of the printed wiring board 50 (the wiring board 100 with the electromagnetic wave shielding layer) while maintaining the electromagnetic wave shielding property.

  The conductive layer 3 having a plurality of openings 31 is formed by, for example, a method of printing a conductive ink or conductive paste in a predetermined pattern on a base film, or a method of forming the openings 31 by etching a metal foil. It can be obtained by a method of forming a metal layer having a predetermined pattern by vapor deposition or sputtering of metal. Moreover, as such a conductive layer 3, a wire mesh itself can also be used.

  As the material of the conductive layer 3, it is preferable to use a metal such as gold, silver, or copper and an alloy thereof, a conductive filler-containing resin, a conductive polymer, or the like.

The thickness of the conductive layer 3 may be appropriately set according to the conductivity of the material used, but is preferably about 0.1 to 20 μm, more preferably about 1 to 10 μm.
The electromagnetic wave shielding sheet 1 is superimposed on the printed wiring board 50 so that the conductive layer 3 is in contact with the printed wiring board 50, and is adhered to the printed wiring board 50 under the conditions of a temperature of 150 ° C. and a pressure of 5 kg / cm ^2. However, it is preferable that the bonding layer 20 does not protrude from the edge of the conductive layer 3 when the printed wiring board 50 is viewed from the electromagnetic wave shielding sheet 1 side (from above the electromagnetic wave shielding sheet 1). Even if it protrudes, the following degree is preferable.
That is, when the bonding layer 20 protrudes, the bonding layer 2 protrudes from the edge of the conductive layer 3 around the electromagnetic wave shielding sheet 1 on the printed wiring board 50 when the electromagnetic wave shielding sheet 1 is viewed from above. Although the protruding portion is formed, the average width of the protruding portion is preferably less than 1 mm, and more preferably less than 0.5 mm.
If the protruding amount of the bonding layer 2 is the above level, a part of the flowing bonding layer 2 reaches the terminal portions 731 and 732 of the printed wiring board 50 when the electromagnetic wave shielding sheet 1 is bonded to the printed wiring board 50. Can be surely prevented. Therefore, in the obtained wiring board 100 with an electromagnetic wave shielding layer, the terminal portions 731 and 732 are reliably exposed. Therefore, when connecting the terminal portions 731 and 732 and the circuit element, the electromagnetic wave shielding layer-equipped wiring board 100 and the circuit element can be reliably connected without causing connection failure.
The electromagnetic wave shielding sheet 1 may include another resin layer on the surface of the bonding layer 2 opposite to the conductive layer 3. Although it does not specifically limit as another resin layer, The layer which has hard-coat property is preferable. As a constituent material of the layer having such hard coat properties, for example, a polyimide resin, an epoxy resin, an acrylic resin, and the like are preferable. In the electromagnetic wave shielding sheet 1 of the present invention, the function as the electromagnetic wave shielding layer 10 is obtained by the bonding layer 2 and the conductive layer 3.

  Such an electromagnetic wave shielding sheet 1 is obtained by, for example, applying the thermosetting resin composition as described above on a peelable sheet and drying it to obtain the bonding layer 2, and then on the bonding layer 2. It can be obtained by forming the conductive layer 3 by a method such as printing, etching, vapor deposition or sputtering. Alternatively, immediately after the formation of the bonding layer 2, the electromagnetic wave shielding sheet 1 can be obtained by superimposing the previously prepared conductive layer 3 on the bonding layer 2.

Next, the manufacturing method of the wiring board 100 with an electromagnetic wave shielding layer using the electromagnetic wave shielding sheet 1 will be described.
[1] First, the electromagnetic wave shielding sheet 1 and the printed wiring board 50 described above are prepared.
[2] Next, the electromagnetic wave shielding sheet 1 is overlaid on the printed wiring board 50 so that the conductive layer 3 and the first insulating layer 80 of the printed wiring board 50 are in contact with each other.
[3] Next, from this state, the electromagnetic wave shielding sheet 1 and the printed wiring board 50 are heated and pressurized in a direction approaching each other. At this time, when the bonding layer 2 and the conductive layer 3 are pressed, a part of the conductive layer 3 is deformed so as to bend toward the printed wiring board 50, and is grounded via the via 81 of the first insulating layer 80. A state of being in contact (connected) with the wiring 72 is obtained.
On the other hand, the bonding layer 2 is melted or softened by heating and flows, and as shown in FIG. 3, the bonding layer 2 is filled in the opening 31 of the conductive layer 3 and the via 81 of the first insulating layer 80. Also filled.
Thereafter, by further heating, the bonding layer 2 (thermosetting resin composition) is cured, and the second insulating layer 20 is formed by the cured product of the bonding layer 2 and is bonded to the first insulating layer 80. The electromagnetic wave shielding layer 10 is formed on the printed wiring board 50. Thus, the wiring board 100 with an electromagnetic wave shielding layer can be obtained.
The heating temperature and pressurizing pressure at this time are such that the bonding layer 2 flows by heating and pressurizing to sufficiently fill the opening 31 of the conductive layer 3, and the bonding layer 2 and the first insulating layer 80 Can be appropriately selected so as to ensure sufficient adhesion.
Specifically, the heating temperature is preferably about 100 to 200 ° C, more preferably about 130 to 200 ° C, and further preferably about 140 to 170 ° C. The pressure of the pressure is preferably in the range of about 1~200kg / cm ^2, more preferably about 1 to 100 kg / cm ^2, more preferably in the range of about 1~80kg / cm ^2, 5 Most preferably, it is about ˜50 kg / cm ² .
Therefore, the conditions of heat and pressure is in the range of temperature 100 to 200 ° C. approximately and a pressure 1~200kg / cm ² of about preferably, in the range of temperature 100 to 200 ° C. approximately and a pressure 1 to 100 kg / cm ² about the More preferably, the temperature is about 130 to 200 ° C. and the pressure is about 1 to 80 kg / cm ² , and the temperature is preferably about 140 to 170 ° C. and the pressure is about 5 to 50 kg / cm ² .
In the present invention, the bonding layer 2 is designed to flow under the conditions of a temperature of 150 ° C. and a pressure of 1 kg / cm ² (preferably a temperature of 150 ° C. and a pressure of 5 kg / cm ² ). As a result, the bonding layer 2 that has flowed through the opening 31 of the conductive layer 3 can be reliably filled, and a high bonding strength can be obtained between the electromagnetic wave shielding sheet 1 (electromagnetic wave shielding layer 10) and the printed wiring board 50. Is obtained.
In this heating and pressurizing step, an apparatus generally used in the production of a printed wiring board can be used. Specifically, as such an apparatus, for example, a flat plate press machine, a biaxial roll press machine and the like provided with a temperature controller can be cited.

The thus obtained wiring board 100 with an electromagnetic wave shielding layer can be made much thinner than a conventional wiring board with an electromagnetic wave shielding layer. In particular, in this embodiment, since the FPC board is used as the board 60 of the printed wiring board 50, the entire thickness of the wiring board 100 with the electromagnetic wave shielding layer can be particularly reduced. Thereby, for example, by mounting the wiring board 100 with an electromagnetic wave shielding layer on a consumer electronic device such as a mobile phone, a digital camera, a personal computer, or an industrial electronic device such as a medical device or an electronic computer, It can contribute to miniaturization and thinning.
As mentioned above, although preferred embodiment of the electromagnetic wave shielding sheet of this invention, the manufacturing method of the wiring board with an electromagnetic wave shield layer, and the wiring board with an electromagnetic wave shield layer was described, this invention is not limited to this.
For example, in the above-described wiring board 100 with an electromagnetic wave shielding layer, the position of the ground wiring 72 in the printed wiring board 50 is provided on the same plane as the signal wiring 71 as shown in FIGS. The wiring 72 is provided on the upper surface of the electromagnetic wave shielding layer 10 (that is, above the signal wiring 71) or the lower surface of the substrate 60 of the printed wiring board 50 (that is, below the signal wiring 71), and conductive paste, conductive pins, etc. It is good also as a structure which takes the continuity with the conductive layer 3 of the electromagnetic wave shield layer 10 by the well-known method using this.
Moreover, the wiring board 100 with an electromagnetic wave shielding layer shown in FIGS. 2 and 3 is an example of the wiring board with an electromagnetic wave shielding layer of the present invention, and the mode in which the electromagnetic wave shielding layer is laminated on the printed wiring board is shown in FIGS. It is not limited to.
Furthermore, according to the method for manufacturing a wiring board with an electromagnetic wave shielding layer of the present invention, by heating and pressurizing the electromagnetic wave shielding sheet 1 on the upper surface and the lower surface of the printed wiring board 50, respectively, You may make it obtain the wiring board 100 with an electromagnetic wave shield layer.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by the following Example.

In addition, the weight average molecular weight of the polyurethane polyurea resin described in the following Example is the weight average molecular weight and number average molecular weight of polystyrene conversion calculated | required by GPC measurement, The conditions of GPC measurement are as follows.
Equipment: Shodex GPC System-21 (manufactured by Showa Denko)
Column: Shodex KF-802, KF-803L, KF-805L
A total of 3 (made by Showa Denko) are connected and used.
Solvent: Tetrahydrofuran Flow rate: 1.0 ml / min
Temperature: 40 ° C
Sample concentration: 0.3% by weight
Sample injection volume: 100 μl

[Synthesis of polyurethane polyurea resin]
[Synthesis Example 1]
A number average molecular weight obtained from adipic acid, terephthalic acid and 3-methyl-1,5-pentanediol (hereinafter, “ 414 parts by weight of diol (Mn) = 1006, 8 parts by weight of dimethylolbutanoic acid, 145 parts by weight of isophorone diisocyanate, and 40 parts by weight of toluene were charged and reacted at 90 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, 300 parts by weight of toluene was further added to the reaction solution to obtain a urethane prepolymer solution having an isocyanate group at the terminal.
Next, 816 parts by weight of the resulting urethane prepolymer solution was added to a mixture of 27 parts by weight of isophoronediamine, 3 parts by weight of di-n-butylamine, 342 parts by weight of 2-propanol, and 576 parts by weight of toluene. The mixture was reacted at 70 ° C. for 3 hours to obtain a polyurethane polyurea resin solution having a weight average molecular weight (hereinafter referred to as “Mw”) = 54,000 and an acid value of 5 mgKOH / g. To this, 144 parts by weight of toluene and 72 parts by weight of 2-propanol were added to obtain a polyurethane polyurea resin solution (C) having a solid content of 30%.

[Example 1]
20 parts by weight of bisphenol A type epoxy resin (“JER828” manufactured by Japan Epoxy Resin) (D) was added to 333 parts by weight of the polyurethane polyurea resin solution (C) to obtain a resin composition solution. With respect to 353 parts by weight of this resin composition solution, 180 parts by weight of a conductive filler (“AgXF-301” manufactured by Fukuda Metal Foil Powder Industry) is added and mixed by stirring to give a total of 100 of polyurethane polyurea resin and epoxy resin (D). A conductive resin composition solution containing 300 parts by weight of a conductive filler with respect to parts by weight was obtained.
Separately, 20 parts by weight of bisphenol A type epoxy resin (D) was added to 333 parts by weight of polyurethane polyurea resin solution (C) to obtain a thermosetting resin composition solution.
Next, a polyethylene terephthalate film having a thickness of 75 μm was prepared as a first peelable film, and a peeling treatment was performed on one surface thereof. The obtained conductive resin composition solution is printed and dried in a mesh shape of L (line) / S (space) = 100 μm / 300 μm on the release-treated surface of the first peelable film. A 5 μm conductive layer (B-1) was formed.
Separately, a polyethylene terephthalate film having a thickness of 50 μm was prepared as a second peelable film, and one surface thereof was peeled. The obtained thermosetting resin composition solution was applied and dried on the release-treated surface of the second peelable film to form a bonding layer (A-1) having a dry film thickness of 15 μm. And the electroconductive layer (B-1) formed on the 1st peelable film and the joining layer (A-1) formed on the 2nd peelable film were bonded together, and the electromagnetic wave shield sheet was obtained.
In addition, when the thermosetting resin composition was obtained by drying the obtained thermosetting resin composition solution and the glass transition temperature was measured, it was 30 degreeC. The glass transition temperature was measured using a differential scanning calorimeter (DSC) at a temperature increase rate of 10 ° C./min.

[Example 2]
An electromagnetic wave shielding sheet was obtained in the same manner as in Example 1 except that the bonding layer (A-1) was changed to the bonding layer (A-2) prepared by the following method.
A thermosetting resin composition solution was obtained by adding 50 parts by weight of a phenol resin as a curing agent and 100 parts by weight of a polysiloxane to 100 parts by weight of a cresol novolac type epoxy resin. On the release treatment surface of the second peelable film, the thermosetting resin composition solution was applied and dried to form a bonding layer (A-2) having a dry film thickness of 15 μm.
In addition, it was 90 degreeC when the glass transition temperature of the thermosetting resin composition was measured like the above.

[Examples 3 to 8]
An electromagnetic wave shielding sheet was produced in the same manner as in Example 1 except that the conductive layer and the bonding layer described in Table 1 were used.

[Example 9]
In the same manner as in Example 1, the conductive resin composition solution of the conductive layer (B-1) is formed on the release treatment surface of the first peelable film so that the dry film thickness is 1 μm. (Space) = printed on a mesh having openings of 100 μm / 300 μm, dried, and further heated at 150 ° C. for 30 minutes to obtain a ground layer of a conductive layer. Next, a plating layer was formed by performing electroplating on the base layer. Thereby, a mesh-like conductive layer (B-4) having a thickness of 10 μm was obtained.
Separately, in the same manner as in Example 1, the bonding layer (A-1) was formed and bonded to the conductive layer (B-2) formed on the first peelable film to obtain an electromagnetic wave shield sheet.
[Example 10]
An electromagnetic wave shielding sheet was produced in the same manner as in Example 1 except that the conductive layer and the bonding layer described in Table 1 were used.

[Comparative Example 1]
An electromagnetic wave shield sheet was prepared in the same manner as in Example 1 except that the conductive layer (B-1) was changed to the conductive layer (B-6) prepared by the following method.
On the release treatment surface of the first peelable film, the conductive resin composition solution of the conductive layer (B-1) is applied and dried, and the conductive layer (B -6) was formed.

[Comparative Example 2]
An electromagnetic wave shielding sheet was obtained in the same manner as in Example 1 except that the bonding layer (A-1) was changed to the bonding layer (A-3) prepared by the following method.
An acrylic pressure-sensitive adhesive (glass transition temperature Tg: −40 ° C.) is coated on the release surface of the second peelable film and dried to form a bonding layer (A-3) having a dry film thickness of 25 μm. did.

[Comparative Example 3]
Example 1 except that the bonding layer (A-1) was changed to a polyethylene naphthalate (PEN) film having a glass transition temperature Tg of 150 ° C. and a thickness of 12 μm (“Teonex” manufactured by Teijin DuPont Films Ltd.). An electromagnetic wave shielding sheet was obtained.

[Comparative Example 4]
First, Example 1 except that the conductive layer (B-1) was changed to a conductive layer printed in a mesh shape so that the circumferential length of the inner peripheral surface defining the opening of the conductive layer was 100 mm. In the same manner as above, the bonding layer and the conductive layer were bonded together to obtain a laminate.
Next, a conductive adhesive layer, a silver deposited layer (thickness 0.1 μm), and a PET film (glass transition temperature Tg: 105 ° C., thickness 9 μm) are sequentially laminated on the surface of the bonding layer opposite to the conductive layer. did. The conductive adhesive layer contained silver-coated copper powder as a conductive filler and a polyester-based adhesive as an adhesive, and had a thickness of 20 μm.

(1) Evaluation of heat resistance The obtained electromagnetic wave shielding sheet was cut into a size of width 12 mm x length 60 mm to prepare five samples. The first peelable film is removed from each sample, and a polyimide film (“Kapton 200EN” manufactured by Toray DuPont Co., Ltd.) having a thickness of 50 μm is pressure-bonded to the conductive layer of each sample under the conditions shown in Table 1. Cured.
After curing, the second peelable film was removed, and heat treatment was performed in an electric oven at 180 ° C. for 3 minutes and then in an electric oven at 280 ° C. for 90 seconds. By visually observing the appearance of the sample after the heat treatment, the presence or absence of appearance defects such as foaming, floating, and peeling was confirmed, and the heat resistance was evaluated according to the following criteria.
[Evaluation criteria]
A: No appearance defect in any sample.
B: Unevenness is observed in some samples, but there is no appearance defect.
C: Appearance defect in one or two samples.
D: Appearance defect with 3 or more samples.

(2) Evaluation of adhesive force The obtained electromagnetic wave shielding sheet was cut | disconnected to the magnitude | size of width 20mm x length 70mm, and the sample was prepared. The first peelable film was removed from the sample, and a polyimide film having a thickness of 50 μm (“Kapton 200EN” manufactured by Toray DuPont) was pressure-bonded to the sample conductive layer under the conditions shown in Table 1 to cure the bonding layer. .
After curing, the second peelable film is removed, and a 90 ° peel test is performed at a pulling speed of 50 mm / min in an atmosphere of 23 ° C. and a relative humidity of 50%, and the adhesion force between the sample and the polyimide film (N / cm ) Was measured.

(3) Evaluation by IPC bending test L / S = 0.1 mm / 0.1 mm, 6 lines of sliding on a two-layer CCL obtained by laminating a polyimide film (thickness 12.5 μm) and a copper foil (thickness 18 μm). A dynamic bending pattern was formed, and a coverlay composed of 12.5 μm of polyimide and 25 μm of adhesive was laminated on this pattern to prepare a flexible printed wiring board.
The obtained electromagnetic shielding sheet was pressure-bonded on both surfaces of the flexible printed wiring board under the conditions shown in Table 1 to obtain a wiring board with an electromagnetic shielding layer. A bending test was performed on this wiring board with an electromagnetic wave shielding layer under the conditions of a radius of curvature: R = 2 mm, a stroke of 30 mm, and a bending speed: 60 cpm. Then, by measuring the number of bendings when the resistance value of this flexible printed wiring board is increased by 30% with respect to the initial resistance value, the rate of decrease in the number of bendings can be determined from the difference in the number of bendings before and after joining the electromagnetic shielding sheet. The flexibility was evaluated according to the following criteria.
[Evaluation criteria]
A: 85% or more, 100% or less B: 50% or more, less than 85% C: 15% or more, less than 50% D: less than 15%

(4) Electromagnetic wave shielding property (transmission attenuation rate) In accordance with ASTM D4935, using a coaxial tube type shielding effect measuring system manufactured by Keycom Corporation, the electromagnetic wave is irradiated under conditions of 100 MHz to 6 GHz, and the electromagnetic wave is attenuated by the electromagnetic wave shielding sheet. The amount of attenuation to be measured was measured, and the electromagnetic shielding properties were evaluated according to the following criteria. Note that the measured value of attenuation is expressed in decibels (unit dB).
[Evaluation criteria]
A: 45 dB or more when irradiated with 6 GHz electromagnetic waves in the microwave region.
B: 40 dB or more and less than 45 dB when irradiated with 6 GHz electromagnetic waves.
C: 35 dB or more and less than 40 dB when irradiated with 6 GHz electromagnetic waves.
D: Less than 35 dB when irradiated with 6 GHz electromagnetic waves.
In general, the electromagnetic wave shielding property is good as long as it is 40 dB (or more than 99% of electromagnetic waves are blocked).

(5) Characteristic impedance measurement A double-sided two-layer CCL is prepared by laminating a copper foil (thickness 18 μm, copper plating thickness 10 μm) on both sides of a polyimide film (thickness 12.5 μm), and polyimide 12.5 μm on both sides. And a coverlay composed of 25 μm adhesive. At that time, two signal wirings (signal circuits) are formed on one copper foil, and two ground wirings (ground circuits) parallel to the signal wirings are formed on both sides of the signal wiring. A flexible printed wiring board was obtained.
At this time, the line width of the signal wiring was 0.05 mm, the line width of the ground wiring was 0.5 mm, the distance between each signal wiring and the ground wiring was 0.05 mm, and the circuit length was 100 mm.
An electromagnetic wave shielding sheet having a width of 10 mm and a length of 95 mm was crimped to the circuit forming surface of the flexible printed wiring board under the conditions shown in Table 1 to obtain a wiring board with an electromagnetic wave shielding layer. With respect to this wiring board with an electromagnetic wave shielding layer, characteristic impedance was measured using a network analyzer E5071C (manufactured by Agilent Japan).
The rate of change of the characteristic impedance before and after pressure bonding of the electromagnetic wave shielding sheet in the wiring board with the electromagnetic wave shielding layer (= characteristic impedance after attaching the shield sheet / characteristic impedance before attaching the shield sheet) was calculated and evaluated according to the following criteria.
[Evaluation criteria]
A: 85% or more, 100% or less B: 70% or more, less than 85% C: 55% or more, less than 70% D: less than 55%

(6) Evaluation of protruding property of bonding layer The obtained electromagnetic wave shielding sheet was superposed on a polyimide film having a thickness of 50 μm (“Kapton 200EN” manufactured by Toray DuPont), heating temperature: 150 ° C., pressure: 5 kgf The pressure bonding process was performed under the conditions of / cm ² and processing time: 30 min. After the crimping process, the protruding portion of the bonding layer that protruded from the edge of the conductive layer was observed using a magnifying glass, the average width of the protruding portion was measured, and the protruding property was evaluated according to the following criteria.
[Evaluation criteria]
A: The average width of the protruding portion is less than 0.5 mm.
B: The average width of the protruding portion is 0.5 mm or more and less than 1 mm.
C: The average width of the protruding portion is 1 mm or more and less than 1.5 mm.
D: The average width of the protruding portion is 1.5 mm or more.
Moreover, in order to evaluate the protrusion property by the difference in the thickness of a joining layer, also about the Example shown below, it evaluated similarly to the above.

[Example 11]
An electromagnetic wave shielding sheet was produced in the same manner as in Example 1 except that the joining layer (A-1) was changed to the joining layer (A-4) prepared by the following method.
On the release-treated surface of the second peelable film, the thermosetting resin composition solution of the joining layer (A-1) is applied and dried to form a joining layer (A-4) having a dry film thickness of 10 μm. did.

[Example 12]
An electromagnetic wave shielding sheet was produced in the same manner as in Example 1 except that the joining layer (A-1) was changed to the joining layer (A-5) prepared by the following method.
On the release treatment surface of the second peelable film, the thermosetting resin composition solution of the joining layer (A-1) is applied and dried to form a joining layer (A-5) having a dry film thickness of 40 μm. did.

  From the results of Table 1, the electromagnetic wave shielding sheets of Examples 1 to 10 have a two-layer configuration of a bonding layer and a conductive layer, but the insulating film (PET film) / silver vapor deposition layer / conductive adhesive shown in Comparative Example 4 It was possible to realize a thin layer while obtaining the same physical properties (heat resistance, adhesiveness, electromagnetic wave shielding properties and impedance characteristics) as the five-layered electromagnetic wave shielding sheet of layer / bonding layer / conductive layer. Further, as shown in Table 2, it was confirmed that the bonding layer used in the present invention can suppress the protrusion of the bonding layer regardless of its thickness.

Claims (8)

An electromagnetic wave shielding sheet used by adhering to a wiring board having signal wiring,
A bonding layer comprising a thermosetting resin composition having a glass transition temperature of 0 to 150 ° C. and having an insulating property capable of flowing under conditions of a temperature of 150 ° C. and a pressure of 1 kg / cm ² ;
An electromagnetic wave shielding sheet comprising a conductive layer provided on one surface of the bonding layer and having a plurality of openings. When the electromagnetic wave shielding sheet and the wiring board are overlapped so that the conductive layer is in contact with the wiring board and bonded to the wiring board at a temperature of 150 ° C. and a pressure of 5 kg / cm ² , the wiring board is 2. The electromagnetic wave shielding sheet according to claim 1, wherein when viewed from the electromagnetic shielding sheet side, an protruding portion is formed in which the bonding layer protrudes from an edge portion of the conductive layer, and an average width of the protruding portion is less than 1 mm. .   The electromagnetic wave shielding sheet according to claim 1, wherein the plurality of openings include openings having the same planar shape.   The electromagnetic wave shielding sheet according to claim 1, wherein the plurality of openings are arranged at equal intervals.   2. The electromagnetic wave shielding sheet according to claim 1, wherein when the plane area of the bonding layer is 100, the plane area of the conductive layer excluding the plurality of openings is 0.05 to 0.8. The wiring board further includes ground wiring,
The electromagnetic wave shielding sheet according to claim 1, wherein a part of the conductive layer constitutes a connection portion that is directly connected to the ground wiring. A wiring board having a signal wiring and an insulating layer covering the signal wiring, and a thermosetting resin composition having a glass transition temperature of 0 to 150 ° C., under conditions of a temperature of 150 ° C. and a pressure of 1 kg / cm ² Preparing an electromagnetic wave shielding sheet having a bonding layer having a fluid insulating property, and a conductive layer provided on one surface of the bonding layer and having a plurality of openings;
The electromagnetic shielding sheet and the wiring board are overlapped so that the insulating layer of the wiring board and the conductive layer of the electromagnetic shielding sheet are in contact with each other,
At least the electromagnetic wave shielding sheet is heated and the electromagnetic wave shielding sheet and the wiring board are pressurized in a direction approaching each other, thereby causing the bonding layer to flow and the insulation through the openings of the conductive layer. A method of manufacturing a wiring board with an electromagnetic wave shielding layer, characterized in that an electromagnetic wave shielding layer is formed by bonding to the layer. The wiring board further includes a ground wiring covered with the insulating layer, and the insulating layer includes a via in which a part of the ground wiring is exposed,
The method for manufacturing a wiring board with an electromagnetic wave shielding layer according to claim 7, wherein a part of the conductive layer is directly connected to the ground wiring through the via when the electromagnetic shielding sheet and the wiring board are bonded.

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