JP6694763B2 - Electromagnetic wave shield film and printed wiring board with electromagnetic wave shield film - Google Patents

Description

  The present invention relates to an electromagnetic wave shield film and a printed wiring board provided with the electromagnetic wave shield film.

  In order to shield the electromagnetic noise generated from the flexible printed wiring board and the electromagnetic noise from the outside, an insulating resin layer and a conductive layer adjacent to the insulating resin layer and composed of a metal thin film layer and a conductive adhesive layer are provided. The electromagnetic wave shielding film may be provided on the surface of the flexible printed wiring board (see, for example, Patent Documents 1 and 2).

FIG. 6 is a cross-sectional view showing an example of a manufacturing process of a conventional flexible printed wiring board with an electromagnetic wave shielding film.
The flexible printed wiring board 101 with an electromagnetic wave shield film includes a flexible printed wiring board 130, an insulating film 140, and an electromagnetic wave shield film 110 from which the first release film 118 is peeled off.
The flexible printed wiring board 130 has a printed circuit 134 provided on one surface of a base film 132.
The insulating film 140 is provided on the surface of the flexible printed wiring board 130 on the side where the printed circuit 134 is provided.
The electromagnetic wave shielding film 110 has an insulating resin layer 112, a metal thin film layer 114 adjacent to the insulating resin layer 112, a conductive adhesive layer 116 adjacent to the metal thin film layer 114 opposite to the insulating resin layer 112, and an insulating layer. The resin layer 112 has a first release film 118 (carrier film) adjacent to the metal thin film layer 114 on the opposite side.
The conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is adhered and cured on the surface of the insulating film 140. Further, the conductive adhesive layer 116 is electrically connected to the printed circuit 134 through the through hole 142 formed in the insulating film 140.

The flexible printed wiring board 101 with the electromagnetic wave shielding film is manufactured through the following steps, for example, as shown in FIG.
Step (i): A step of providing an insulating film 140 having a through hole 142 formed at a position corresponding to the ground of the printed circuit 134 on the surface of the flexible printed wiring board 130 where the printed circuit 134 is provided.
Step (ii): The electromagnetic wave shielding film 110 is superposed on the surface of the insulating film 140 so that the conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is in contact with the surface of the insulating film 140 by hot pressing. A step of adhering the conductive adhesive layer 116 and electrically connecting the conductive adhesive layer 116 to the ground of the printed circuit 134 through the through hole 142.
Step (iii): A step of obtaining the flexible printed wiring board 101 with an electromagnetic wave shielding film by peeling and removing the first release film 118 that has finished the role of a carrier film after hot pressing from the insulating resin layer 112. ..

JP, 2000-269632, A JP, 2005-109404, A

  However, when the conductive adhesive layer of the electromagnetic wave shielding film is adhered to the printed circuit of the printed wiring board through the through hole of the insulating film, the adhesion between the ground and the conductive adhesive layer tends to be insufficient. Therefore, when the first release film is peeled from the insulating resin layer or when the flexible printed wiring board with the electromagnetic wave shielding film is heated at a high temperature to fully cure the conductive adhesive layer, the ground and the conductive adhesive are Peeling easily occurs between the layers. Therefore, the connection resistance between the ground and the conductive adhesive layer becomes high, and electrical connection may not be performed reliably.

  The present invention provides an electromagnetic wave shield film that can be reliably electrically connected to a printed circuit of a printed wiring board through a through hole of an insulating film provided on the surface of the printed wiring board, and an insulation provided on the surface of the printed wiring board. Provided is a printed wiring board with an electromagnetic wave shielding film, in which a conductive adhesive layer of an electromagnetic wave shielding film is surely electrically connected to a printed circuit of the printed wiring board through a through hole of the film.

The present invention has the following aspects.
<1> Insulating resin layer; Metal thin film layer adjacent to the insulating resin layer; Conductive adhesive layer adjacent to the metal thin film layer on the opposite side to the insulating resin layer; The metal of the insulating resin layer An electromagnetic wave shielding film, comprising: a first release film adjacent to the thin film layer on the opposite side; and the metal thin film layer has a thickness of 150 nm or more and 400 nm or less.
<2> The electromagnetic wave shielding film according to <1>, wherein the metal thin film layer has a hardness of 0.3 GPa or more and 2.0 GPa or less according to a nanoindentation method.
<3> The electromagnetic wave shielding film according to <1> or <2>, wherein the conductive adhesive layer contains conductive particles; and the 10% compressive strength of the conductive particles is 30 MPa or more and 200 MPa or less.
<4> In the above <1> to <3>, the conductive adhesive layer contains metal particles as conductive particles; the metal forming the metal thin film layer and the metal forming the metal particles are copper. Either electromagnetic shielding film.
<5> The electromagnetic wave shielding film according to any one of <1> to <4>, wherein the metal thin film layer is a vapor deposition film.
<6> The electromagnetic wave shielding film according to any one of <1> to <5>, wherein the conductive adhesive layer has a storage elastic modulus at 180 ° C. of 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less.
<7> The electromagnetic wave shielding film according to any one of the above items <1> to <6>, wherein the first release film has a storage elastic modulus at 180 ° C. of 8 × 10 ⁷ Pa or more and 5 × 10 ⁹ Pa or less.
<8> The electromagnetic wave shield film according to any one of <1> to <7>, wherein the insulating resin layer has a storage elastic modulus at 180 ° C. of 5 × 10 ⁶ Pa or more and 5 × 10 ⁹ Pa or less.
<9> The electromagnetic wave shielding film according to any one of <1> to <8>, further including a second release film adjacent to the side of the conductive adhesive layer opposite to the metal thin film.
<10> A printed wiring board having a printed circuit provided on at least one surface of a substrate; an insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided; The electromagnetic wave shielding film according to any one of <1> to <8>, which is adjacent to a film and in which the conductive adhesive layer is electrically connected to the printed circuit through a through hole formed in the insulating film. And a printed wiring board with an electromagnetic wave shielding film.

The electromagnetic wave shielding film of the present invention can be reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film provided on the surface of the printed wiring board.
In the printed wiring board with an electromagnetic shielding film of the present invention, the conductive adhesive layer of the electromagnetic shielding film is surely electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film provided on the surface of the printed wiring board. Connected to each other.

It is sectional drawing which shows one Embodiment of the electromagnetic wave shield film of this invention. It is sectional drawing which shows other embodiment of the electromagnetic wave shield film of this invention. It is sectional drawing which shows the manufacturing process of the electromagnetic wave shield film of FIG. It is sectional drawing which shows one Embodiment of the printed wiring board with an electromagnetic wave shield film of this invention. It is sectional drawing which shows the manufacturing process of the printed wiring board with an electromagnetic wave shield film of FIG. It is sectional drawing which shows an example of the manufacturing process of the conventional flexible printed wiring board with an electromagnetic wave shield film.

The following definitions of terms apply throughout the specification and claims.
The “isotropic conductive adhesive layer” means a conductive adhesive layer having conductivity in the thickness direction and the plane direction.
The "anisotropic conductive adhesive layer" means a conductive adhesive layer that has conductivity in the thickness direction and does not have conductivity in the plane direction.
The “conductive adhesive layer having no conductivity in the plane direction” means a conductive adhesive layer having a surface resistance of 1 × 10 ⁴ Ω or more.

For the average particle diameter of the conductive particles, 30 conductive particles are randomly selected from the microscope image of the conductive particles, and the minimum diameter and the maximum diameter of each conductive particle are measured. Is the value obtained by arithmetically averaging the measured particle diameters of the 30 conductive particles, where the median value of is the particle diameter of one particle.
The thickness of the film (release film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), metal thin film layer, etc. can be measured at 5 locations by observing the cross section of the measurement object using a microscope. It is a value obtained by measuring and averaging the thickness.

The storage elastic modulus is calculated as one of the viscoelastic properties using a dynamic viscoelasticity measuring device which is calculated from the stress applied to the measurement target and the detected strain and outputs as a function of temperature or time.
For the surface resistance, two thin-film metal electrodes (length 10 mm, width 5 mm, inter-electrode distance 10 mm) formed by vapor-depositing gold on quartz glass were used. The resistance between the electrodes is measured by pressing a region of 10 mm × 20 mm of the object to be measured with a load of 0.049 N from above the object and measuring with a measuring current of 1 mA or less.

The hardness of the metal thin film layer by the nano indentation method is measured by the following nano indentation method (continuous stiffness measurement method) using an ultra-micro hardness meter and a diamond triangular pyramid indenter as the indenter. From the following calculation method.
An indentation load / unload test is performed on the metal thin film layer using a triangular pyramid indenter (Berkovich indenter) to obtain a load-indentation depth diagram.
The hardness H at the maximum load is defined by the following formula (1) using the load P and the projected area A of the indentation remaining after the elastic deformation after the pushing.
H = P / A (1)
The projected area A of the indentation is obtained from the following equation (2).
A = ηkh _c ² (2)
However, η is a correction coefficient of the indenter tip shape, k is a constant obtained from the geometric shape of the indenter, k = 24.56 in the Berkovich indenter, h _c is the effective contact depth, and the following equation ( It is represented by 3).
h _c = h−ε {c / (dP / dh)} (3)
However, h is the total displacement measured, dP / dh is the initial gradient at the time of unloading in the obtained load-pushing depth diagram, and ε is a constant obtained from the geometrical shape of the indenter, The value is 0.75 with the Berkovich indenter.
From Equations (1), (2) and (3), the hardness at maximum load P _max is calculated from Equation (4) below.
H = P _max / (ηkh _c ² ) (4)

In addition, dP / dh in Formula (3) is calculated by the following nanoindentation method (continuous rigidity measurement method).
The continuous stiffness measurement method is that the indenter is slightly vibrated during the indentation test, and the response amplitude and phase difference to the vibration are acquired as a function of time, and dP / dh is calculated in response to the continuous change of the indentation depth. It is a method of continuously calculating. The principle is shown below.
The total force (detection load component) F (t) in the direction in which the indenter enters the metal thin film layer is represented by the following formula (5).
F (t) = m (d ² h / dt ² ) + D (dh / dt) + Kh (5)
However, the first term of the formula (5) is the force (m: mass of the indenter shaft) derived from the indenter shaft, and the second term of the formula (5) is the force derived from the viscous component of the metal thin film layer and the indenter system ( D is the loss constant), and the third term of equation (5) is a combined force of the metal thin film layer, the compliance of the load system frame (load frame), and the rigidity of the leaf spring supporting the indenter shaft (K: compound rigidity). And t is time. D and K in the equation (5) are represented by the following equations (6) and (7).
K = {(dh / dP) + C _r } ^-1 + K _s (6)
D = D _s + D _i (7)
However, C _r is the compliance of the load frame, K _s is the rigidity of the leaf spring that supports the indenter shaft, D _s is the loss constant of the indenter system, and D _i is the loss constant of the metal thin film layer. Further, F (t) of the equation (5) is represented by the following equation (8) because it depends on time.
F (t) = F ₀ exp (iωt) (8)
However, F ₀ is a constant and ω is an angular frequency. Substituting equation (8) into equation (5) and substituting equation (9) below, which is a special solution of the ordinary differential equation, to solve the equation, dP / dh is calculated as in equation (10) below. It
h = h ₀ exp {i (ωt−φ)} (9)
_{dP / dh = [1 / {} (F 0 / h 0) cosφ- (K s -mω 2)} - C r] -1 (10)
However, φ is a phase difference. In the formula (10), since C _r , m, and K _s are known at the time of measurement, the vibration amplitude (h ₀ ) of displacement, the phase difference (φ), and the excitation vibration are measured when measuring the metal thin film layer. By measuring the amplitude (F ₀ ), dP / dh can be continuously calculated from Expression (10) in accordance with the continuous change in the indentation depth. Therefore, the hardness of the metal thin film layer can be calculated by substituting the calculated value into the equation (3).

The 10% compressive strength of the conductive particles is obtained by the above-mentioned formula (11) from the measurement result using a micro compression tester.
C (x) = 2.48P / πd ² (11)
However, C (x) is 10% compressive strength (MPa), P is the test force (N) at the time of 10% displacement of the particle diameter, and d is the particle diameter (mm).

<Electromagnetic wave shield film>
FIG. 1 is a sectional view showing a first embodiment of the electromagnetic wave shielding film of the present invention, and FIG. 2 is a sectional view showing a second embodiment of the electromagnetic wave shielding film of the present invention.
The electromagnetic wave shielding film 1 of the first and second embodiments includes an insulating resin layer 10, a conductive layer 20 adjacent to the insulating resin layer 10, and an opposite side of the insulating resin layer 10 to the conductive layer 20. A first release film 30 and a second release film 40 adjacent to the conductive layer 20 on the opposite side of the insulating resin layer 10.

In the electromagnetic wave shielding film 1 of the first embodiment, the conductive layer 20 includes the metal thin film layer 22 adjacent to the insulating resin layer 10 and the anisotropic conductive adhesive layer 24 adjacent to the second release film 40. It is an example to have.
In the electromagnetic wave shielding film 1 of the second embodiment, the conductive layer 20 includes the metal thin film layer 22 adjacent to the insulating resin layer 10 and the isotropic conductive adhesive layer 26 adjacent to the second release film 40. It is an example to have.

(Insulating resin layer)
The insulating resin layer 10 serves as a base (base) when forming the metal thin film layer 22, and after the electromagnetic wave shielding film 1 is attached to the surface of the insulating film provided on the surface of the flexible printed wiring board, the metal thin film is formed. It serves as a protective layer for the layer 22.

  The insulating resin layer 10 is preferably a coating film formed by applying a coating material containing a thermosetting resin and a curing agent and semi-curing or curing it from the viewpoint of heat resistance when soldering by a reflow method or the like. ..

Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curing acrylate resin. As the thermosetting resin, an amide resin and an epoxy resin are preferable from the viewpoint of excellent heat resistance.
Examples of the curing agent include known curing agents depending on the type of thermosetting resin.

The storage elastic modulus at 180 ° C. of the insulating resin layer 10 before hot pressing is preferably 5 × 10 ⁶ Pa or more and 5 × 10 ⁹ Pa or less, more preferably 1 × 10 ⁷ Pa or more and 1 × 10 ⁹ Pa or less. If the storage elastic modulus at 180 ° C. of the insulating resin layer 10 is equal to or higher than the lower limit value of the above range, the insulating resin layer 10 will have more appropriate hardness, and the pressure loss in the insulating resin layer 10 at the time of hot pressing. Can be further reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently adhered, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film. To be done. When the storage elastic modulus at 180 ° C. of the insulating resin layer 10 is equal to or lower than the upper limit value of the above range, the flexibility of the electromagnetic wave shielding film 1 is further improved. As a result, the electromagnetic wave shielding film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. ..

The insulating resin layer 10 may be colored in order to impart a design property to the printed wiring board with the electromagnetic wave shielding film.
On the surface of the insulating resin layer 10, in order to make scratches on the surface of the insulating resin layer 10 inconspicuous, the unevenness of the first release film 30 that has been embossed or blasted may be transferred. ..
The insulating resin layer 10 may include other components (flame retardant, etc.).

The surface resistance of the insulating resin layer 10 is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the insulating resin layer 10 is preferably 1 × 10 ¹⁹ Ω or less from the practical point of view.
The thickness of the insulating resin layer 10 is preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 20 μm or less. When the thickness of the insulating resin layer 10 is equal to or more than the lower limit value of the above range, the insulating resin layer 10 can sufficiently exhibit its function as a protective layer. If the thickness of the insulating resin layer 10 is equal to or less than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned.

(Conductive layer)
As the conductive layer 20, a metal thin film layer 22 adjacent to the insulating resin layer 10 and a conductive adhesive layer (anisotropic conductive adhesive layer 24 which is the outermost layer on the opposite side of the conductive layer 20 from the insulating resin layer 10). Alternatively, a conductive layer (I) having an isotropic conductive adhesive layer 26); or a conductive layer (II) including only the isotropic conductive adhesive layer 26 may be used. In the present invention, the conductive layer (I) is used as the conductive layer 20 because it can sufficiently function as an electromagnetic wave shield layer.

(Metal thin film layer)
The metal thin film layer 22 is a layer made of a metal thin film. Since the metal thin film layer 22 is formed so as to spread in the plane direction, it has conductivity in the plane direction and functions as an electromagnetic wave shield layer or the like.

  Examples of the metal thin film layer 22 include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or CVD, a plating film formed by plating, a metal foil, and the like. From the viewpoint of excellent conductivity in the surface direction, a vapor deposition film and a plating film are preferable, the thickness can be made thin, and even if the thickness is thin, the conductivity in the surface direction is excellent, and since it can be easily formed by a dry process, A vapor-deposited film is more preferable, and a vapor-deposited film formed by physical vapor deposition is further preferable.

  Examples of the metal forming the metal thin film layer 22 include aluminum, silver, copper, gold, conductive ceramics and the like. Copper is preferable from the viewpoint of electrical conductivity and the fact that the metal thin film layer 22 has an appropriate hardness and the pressure loss in the metal thin film layer 22 during hot pressing can be reduced.

  The hardness of the metal thin film layer 22 by the nanoindentation method is preferably 0.3 GPa or more and 2.0 GPa or less, more preferably 0.4 GPa or more and 1.5 GPa or less, and further preferably 0.5 GPa or more and 1.0 GPa or less. If the hardness of the metal thin film layer 22 by the nanoindentation method is equal to or higher than the lower limit value of the above range, the metal thin film layer 22 will have a more appropriate hardness, and the pressure in the metal thin film layer 22 at the time of hot pressing. The loss can be further reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently adhered, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film. To be done. When the hardness of the metal thin film layer 22 by the nanoindentation method is not more than the upper limit value of the above range, the flexibility of the electromagnetic wave shielding film 1 is further improved. As a result, the electromagnetic wave shielding film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. ..

  The surface resistance of the metal thin film layer 22 is preferably 0.001 Ω or more and 1 Ω or less, and more preferably 0.001 Ω or more and 0.1 Ω or less. If the surface resistance of the metal thin film layer 22 is at least the lower limit value of the above range, the metal thin film layer 22 can be made sufficiently thin. When the surface resistance of the metal thin film layer 22 is equal to or less than the upper limit value of the above range, it can sufficiently function as an electromagnetic wave shield layer.

  The thickness of the metal thin film layer 22 is 150 nm or more and 400 nm or less, preferably 200 nm or more and 350 nm or less, and more preferably 250 nm or more and 300 nm or less. When the thickness of the metal thin film layer 22 is equal to or more than the lower limit value of the above range, the metal thin film layer 22 has appropriate hardness, and the pressure loss in the metal thin film layer 22 during hot pressing can be reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are sufficiently adhered, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. It When the thickness of the metal thin film layer 22 is equal to or less than the upper limit value of the above range, the flexibility of the electromagnetic wave shielding film 1 is improved. As a result, the electromagnetic wave shielding film 1 easily sinks into the through hole of the insulating film, and the conductive adhesive layer is surely electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film.

(Conductive adhesive layer)
The conductive adhesive layer has conductivity and adhesiveness at least in the thickness direction.
As the conductive adhesive layer, an anisotropic conductive adhesive layer 24 that has conductivity in the thickness direction and does not have conductivity in the plane direction, or has conductivity in the thickness direction and the plane direction, etc. The one-way conductive adhesive layer 26 is included. As the conductive adhesive layer in the conductive layer (I), the anisotropic conductive adhesive layer 24 is preferable from the following points.
The conductive adhesive layer has an appropriate hardness, and the pressure loss in the conductive adhesive layer during hot pressing can be further reduced.
-The conductive adhesive layer can be made thin, the amount of conductive particles can be reduced, and as a result, the electromagnetic wave shielding film 1 can be made thin and the electromagnetic wave shielding film 1 can be made flexible.
As the conductive adhesive layer in the conductive layer (I), the isotropic conductive adhesive layer 26 is preferable because it can sufficiently function as an electromagnetic wave shield layer.

As the conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting conductive adhesive layer may be in an uncured state or in a B-staged state.
The thermosetting anisotropic conductive adhesive layer 24 includes, for example, a thermosetting adhesive 24a and conductive particles 24b. The thermosetting anisotropically conductive adhesive layer 24 may include a flame retardant as needed.
The thermosetting isotropic conductive adhesive layer 26 includes, for example, a thermosetting adhesive 26a and conductive particles 26b. The thermosetting isotropic conductive adhesive layer 26 may include a flame retardant, if necessary.

Examples of the thermosetting adhesive include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curable acrylate resin. Epoxy resin is preferable from the viewpoint of excellent heat resistance. The epoxy resin may include a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, and the like.
The thermosetting adhesive may contain a cellulose resin or microfibril (glass fiber or the like) in order to increase the strength of the conductive adhesive layer and improve the punching property.

  Examples of the conductive particles include particles of metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.), graphite powder, fired carbon particles, plated fired carbon particles, and the like. As the conductive particles, the conductive adhesive layer comes to have a more appropriate hardness, and from the viewpoint that the pressure loss in the conductive adhesive layer during hot pressing can be further reduced, metal particles are preferable, and copper is preferable. Particles are more preferred.

  The 10% compressive strength of the conductive particles is preferably 30 MPa or more and 200 MPa or less, more preferably 50 MPa or more and 150 MPa or less, and further preferably 70 MPa or more and 100 MPa or less. When the 10% compressive strength of the conductive particles is equal to or higher than the lower limit value of the above range, the conductive adhesive layer does not significantly lose the pressure applied to the metal thin film layer 22 during the hot pressing, and the conductive adhesive layer forms through holes of the insulating film. The printed circuit of the printed wiring board is securely connected electrically through. When the 10% compressive strength of the conductive particles is equal to or less than the upper limit value of the above range, the contact with the metal thin film layer 22 is improved and the electrical connection is ensured.

  The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, and more preferably 4 μm or more and 16 μm or less. When the average particle diameter of the conductive particles 24b is equal to or larger than the lower limit value of the above range, the thickness of the anisotropic conductive adhesive layer 24 can be secured and sufficient adhesive strength can be obtained. When the average particle diameter of the conductive particles 24b is equal to or less than the upper limit value of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through hole of the insulating film) can be secured, and the insulating film The inside of the through hole can be sufficiently filled with a conductive adhesive.

  The average particle diameter of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 1 μm or less. When the average particle diameter of the conductive particles 26b is equal to or more than the lower limit value of the above range, the number of contact points of the conductive particles 26b increases, and the conductivity in the three-dimensional direction can be stably increased. When the average particle diameter of the conductive particles 26b is equal to or less than the upper limit value of the above range, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be secured, and the insulating film The inside of the through hole can be sufficiently filled with a conductive adhesive.

  The ratio of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1% by volume or more and 30% by volume or less, preferably 2% by volume or more and 10% by volume, in 100% by volume of the anisotropic conductive adhesive layer 24. The following is more preferable. When the ratio of the conductive particles 24b is at least the lower limit value of the above range, the conductivity of the anisotropic conductive adhesive layer 24 will be good. When the ratio of the conductive particles 24b is equal to or less than the upper limit value of the above range, the anisotropic conductive adhesive layer 24 has good adhesiveness and fluidity (following the shape of the through holes of the insulating film). Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

  The proportion of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 50% by volume or more and 80% by volume or less, and 60% by volume or more and 70% by volume, of 100% by volume of the isotropic conductive adhesive layer 26. The following is more preferable. When the ratio of the conductive particles 26b is at least the lower limit value of the above range, the conductivity of the isotropic conductive adhesive layer 26 will be good. When the ratio of the conductive particles 26b is equal to or less than the upper limit value of the above range, the adhesiveness and fluidity of the isotropic conductive adhesive layer 26 (the conformability to the shape of the through hole of the insulating film) will be good. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

The surface resistance of the anisotropic conductive adhesive layer 24 is preferably 1 × 10 ⁴ Ω or more and 1 × 10 ¹⁶ Ω or less, more preferably 1 × 10 ⁶ Ω or more and 1 × 10 ¹⁴ Ω or less. When the surface resistance of the anisotropic conductive adhesive layer 24 is at least the lower limit value of the above range, the content of the conductive particles 24b can be suppressed to be low. When the surface resistance of the anisotropic conductive adhesive layer 24 is not more than the upper limit value of the above range, there is no problem in anisotropy in practical use.

  The surface resistance of the isotropic conductive adhesive layer 26 is preferably 0.05Ω or more and 2.0Ω or less, more preferably 0.1Ω or more and 1.0Ω or less. When the surface resistance of the isotropic conductive adhesive layer 26 is at least the lower limit value of the above range, the content of the conductive particles 26b is suppressed to be low, the viscosity of the conductive adhesive does not become too high, and the coating property is further improved. It will be good. Further, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be further secured. When the surface resistance of the isotropic conductive adhesive layer 26 is not more than the upper limit value of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

The storage elastic modulus at 180 ° C. of the conductive adhesive layer is preferably 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less, more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. If the storage elastic modulus at 180 ° C. of the conductive adhesive layer is at least the lower limit value of the above range, the conductive adhesive layer will have a more appropriate hardness, and the conductive adhesive layer at the time of hot pressing It is possible to further reduce the pressure loss at. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently adhered, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film. To be done. When the storage elastic modulus at 180 ° C. of the conductive adhesive layer is at most the upper limit value of the above range, the flexibility of the electromagnetic wave shielding film 1 will be further improved. As a result, the electromagnetic wave shielding film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. ..

  The thickness of the anisotropic conductive adhesive layer 24 is preferably 3 μm or more and 25 μm or less, more preferably 5 μm or more and 15 μm or less. If the thickness of the anisotropic conductive adhesive layer 24 is at least the lower limit value of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through hole of the insulating film) can be secured, The through holes of the insulating film can be sufficiently filled with the conductive adhesive. When the thickness of the anisotropic conductive adhesive layer 24 is not more than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

  The thickness of the isotropic conductive adhesive layer 26 is preferably 5 μm or more and 20 μm or less, more preferably 7 μm or more and 17 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is not less than the lower limit value of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good, and the isotropic conductive adhesive layer 26 can sufficiently function as an electromagnetic wave shield layer. Further, the fluidity of the isotropic conductive adhesive layer 26 (the conformability to the shape of the through hole of the insulating film) can be secured, and the through hole of the insulating film can be sufficiently filled with the conductive adhesive, and Foldability can be ensured and the isotropic conductive adhesive layer 26 will not be broken even if it is repeatedly bent. If the thickness of the isotropic conductive adhesive layer 26 is not more than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

(First release film)
The first release film 30 serves as a carrier film when the insulating resin layer 10 and the conductive layer 20 are formed, and improves the handleability of the electromagnetic wave shield film 1. The first release film 30 is peeled from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like.

  The first release film 30 has, for example, a release film body 32 and a release agent layer 34 provided on the surface of the release film body 32 on the insulating resin layer 10 side.

  As the resin material of the release film body 32, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, Polyvinylidene chloride, synthetic rubber, liquid crystal polymer and the like are mentioned, and polyethylene terephthalate is preferable from the viewpoint of heat resistance (dimensional stability) and cost when the electromagnetic wave shielding film 1 is manufactured.

The storage elastic modulus at 180 ° C. of the release film body 32 is preferably 8 × 10 ⁷ Pa or more and 5 × 10 ⁹ Pa, more preferably 1 × 10 ⁸ Pa or more and 8 × 10 ⁸ Pa. When the storage elastic modulus at 180 ° C. of the release film main body 32 is equal to or higher than the lower limit value of the above range, the first release film 30 has a more appropriate hardness, and the first release film 30 has a first hardness during hot pressing. The pressure loss in the release film 30 can be further reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently adhered, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film. To be done. When the storage elastic modulus at 180 ° C. of the release film main body 32 is at most the upper limit value of the above range, the flexibility of the electromagnetic wave shielding film 1 will be further improved. As a result, the electromagnetic wave shielding film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. ..

  The thickness of the release film main body 32 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less. When the thickness of the release film main body 32 is not less than the lower limit value of the above range, the handling property of the electromagnetic wave shielding film 1 becomes good. When the thickness of the release film main body 32 is equal to or less than the upper limit value of the above range, heat is easily transferred to the conductive adhesive layer when the conductive adhesive layer of the electromagnetic wave shielding film 1 is hot pressed onto the surface of the insulating film. ..

The release agent layer 34 is formed by subjecting the surface of the release film body 32 to a release treatment with a release agent. Since the first release film 30 has the release agent layer 34, when the first release film 30 is peeled from the insulating resin layer 10, the first release film 30 is easily peeled off, and the insulating resin The layer 10 and the conductive adhesive layer after curing are less likely to break.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 34 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. When the thickness of the release agent layer 34 is within the above range, the first release film 30 can be more easily peeled off.

(Second release film)
The second release film 40 protects the conductive adhesive layer and improves the handleability of the electromagnetic wave shielding film 1. The second release film 40 is peeled off from the conductive adhesive layer before the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like.

  The second release film 40 includes, for example, a release film body 42 and a release agent layer 44 provided on the surface of the release film body 42 on the side of the conductive adhesive layer.

As the resin material of the release film main body 42, the same material as the resin material of the release film main body 32 can be mentioned.
The thickness of the release film main body 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less.

The release agent layer 44 is formed by subjecting the surface of the release film main body 42 to a release treatment with a release agent. Since the second release film 40 has the release agent layer 44, when the second release film 40 is released from the conductive adhesive layer, the second release film 40 is easily released, and the second release film 40 is electrically conductive. Of the adhesive layer becomes difficult to break.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 34 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. When the thickness of the release agent layer 34 is within the above range, the second release film 40 can be more easily peeled off.

(Thickness of electromagnetic wave shield film)
The thickness of the electromagnetic wave shielding film 1 (excluding the release film) is preferably 10 μm or more and 45 μm or less, more preferably 10 μm or more and 30 μm or less. When the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or more than the lower limit value of the above range, the first release film 30 is less likely to break when peeled off. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is not more than the upper limit value of the above range, the printed wiring board with the electromagnetic wave shielding film can be made thin.

(Method for manufacturing electromagnetic wave shielding film)
The electromagnetic wave shielding film of the present invention can be produced, for example, by the method (α) including the following steps (a) to (c).
Step (a): A step of forming an insulating resin layer on one surface of the first release film.
Step (b): A step of forming a conductive layer on the surface of the insulating resin layer after the step (a).
Step (c): A step of attaching the second release film to the surface of the conductive layer after the step (b).

Moreover, the electromagnetic wave shielding film of the present invention can be produced, for example, by the method (β) having the following steps (a ′), (b′1), (b′2) and (c ′).
Step (a '): A step of forming an insulating resin layer on one surface of the first release film.
Step (b'1): A metal thin film layer is formed on the surface of the insulating resin layer to obtain a first layered product including a first release film, an insulating resin layer, and a metal thin film layer in order. Process.
Step (b′2): A second laminate provided with a second release film and a conductive adhesive layer in that order by forming a conductive adhesive layer on one surface of the second release film. To obtain.
Step (c ′): A step of bonding the first laminated body and the second laminated body so that the metal thin film layer and the conductive adhesive layer are in contact with each other.

  Hereinafter, a method for manufacturing the electromagnetic wave shielding film 1 shown in FIG. 1 by the method (α) will be described with reference to FIG.

Step (a):
As shown in FIG. 3, the insulating resin layer 10 is formed on one surface of the first release film 30.
As a method of forming the insulating resin layer 10, a method of applying a coating material containing a thermosetting resin and a curing agent and semi-curing or curing is preferable from the viewpoint of heat resistance when soldering by a reflow method.
The coating material containing the thermosetting resin and the curing agent may contain a solvent and other components (flame retardant, etc.) as necessary.

  The storage elastic modulus of the insulating resin layer 10 is controlled by selecting the type and composition of the thermosetting resin, the curing agent, etc., adjusting the curing conditions such as temperature and time when the thermosetting resin is semi-cured or cured, It can be carried out by adding a thermoplastic resin such as a thermoplastic elastomer as a component having no curability.

Step (b):
As shown in FIG. 3, the metal thin film layer 22 is formed on the surface of the insulating resin layer 10 (step (b1)), and the anisotropic conductive adhesive layer 24 is formed on the surface of the metal thin film layer 22 (step (b2). )).

  Examples of the method of forming the metal thin film layer 22 include physical vapor deposition, a method of forming a vapor deposition film formed by CVD, a method of forming a plating film by plating, a method of attaching a metal foil, and the like. From the viewpoint that the metal thin film layer 22 having excellent conductivity in the surface direction can be formed, a method of forming a vapor deposition film by physical vapor deposition, CVD, or a method of forming a plating film by plating is preferable, and the thickness of the metal thin film layer 22 can be reduced. The metal thin film layer 22 having excellent conductivity in the surface direction can be formed even if the thickness is thin, and the metal thin film layer 22 can be easily formed by a dry process. Therefore, the vapor deposition film is formed by physical vapor deposition or CVD. The method is more preferable, and the method of forming a vapor deposition film by physical vapor deposition is still more preferable.

Examples of the method of forming the anisotropic conductive adhesive layer 24 include a method of applying a thermosetting conductive adhesive composition to the surface of the metal thin film layer 22.
As the thermosetting conductive adhesive composition, a composition containing a thermosetting adhesive 24a and conductive particles 24b is used.
The storage elastic modulus of the anisotropic conductive adhesive layer 24 can be controlled in the same manner as the storage elastic modulus of the insulating resin layer 10.

Step (c):
As shown in FIG. 3, the second release film 40 is attached to the surface of the anisotropic conductive adhesive layer 24 to obtain the electromagnetic wave shielding film 1.

(Effect)
In the electromagnetic wave shielding film 1 described above, the thickness of the metal thin film layer 22 is 150 nm or more, so that the metal thin film layer 22 has an appropriate hardness, and the metal thin film layer 22 at the time of hot pressing. It is possible to reduce the pressure loss at. As a result, the conductive adhesive layer is sufficiently adhered to the printed circuit of the printed wiring board, and the conductive adhesive layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. It Moreover, since the thickness of the metal thin film layer 22 is 400 nm or less, the flexibility of the electromagnetic wave shielding film 1 is improved. As a result, the electromagnetic wave shielding film 1 easily sinks into the through hole of the insulating film, and the conductive adhesive layer is surely electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film having a first release film, an insulating resin layer, a metal thin film layer and a conductive adhesive layer in this order, and the metal thin film layer has a thickness of 150 nm to 400 nm. The following is acceptable, and the present invention is not limited to the illustrated embodiment.
For example, the insulating resin layer may be two or more layers.
When the tackiness of the surface of the conductive adhesive layer is small, the second release film 40 may be omitted.
The release film may not have the release agent layer when the release film itself has sufficient release properties.
The release film may have an adhesive layer instead of the release agent layer.

<Printed wiring board with electromagnetic wave shielding film>
FIG. 4 is a sectional view showing an embodiment of a printed wiring board with an electromagnetic wave shielding film of the present invention.
The flexible printed wiring board 2 with the electromagnetic wave shielding film includes the flexible printed wiring board 50, the insulating film 60, and the electromagnetic wave shielding film 1 of the first embodiment.
The flexible printed wiring board 50 is one in which a printed circuit 54 is provided on at least one surface of a base film 52.
The insulating film 60 is provided on the surface of the flexible printed wiring board 50 on the side where the printed circuit 54 is provided.
The anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 1 is adhered and cured on the surface of the insulating film 60. Further, the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through a through hole (not shown) formed in the insulating film 60.
In the flexible printed wiring board 2 with the electromagnetic wave shielding film, the second release film 40 is peeled off from the anisotropic conductive adhesive layer 24.
When the first release film 30 is no longer necessary in the flexible printed wiring board 2 with the electromagnetic wave shielding film, the first release film 30 is peeled off from the insulating resin layer 10.

The metal thin film layer 22 of the electromagnetic wave shielding film 1 includes the insulating film 60 and the anisotropic conductive adhesive layer 24 in the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) except for the portion having the through holes. They are spaced apart and are opposed to each other.
The distance between the printed circuit 54 and the metal thin film layer 22 excluding the portion having the through hole is substantially equal to the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24. The separation distance is preferably 30 μm or more and 200 μm or less, and more preferably 60 μm or more and 200 μm or less. If the separation distance is less than 30 μm, the impedance of the signal circuit becomes low. Therefore, in order to have a characteristic impedance of 100Ω or the like, the line width of the signal circuit must be made small, and the variation in the line width causes the variation in the characteristic impedance. Then, the reflected resonance noise due to the impedance mismatch becomes easy to be carried on the electric signal. If the separation distance is larger than 200 μm, the flexible printed wiring board 2 with the electromagnetic wave shielding film becomes thick and the flexibility becomes insufficient.

(Flexible printed wiring board)
The flexible printed wiring board 50 is a printed circuit (power circuit, ground circuit, ground layer, etc.) obtained by processing a copper foil of a copper clad laminate into a desired pattern by a known etching method.
As the copper clad laminate, a copper foil is attached to one surface or both surfaces of the base film 52 via an adhesive layer (not shown); a resin solution for forming the base film 52 is cast on the surface of the copper foil. The thing etc. are mentioned.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, acrylic resin, and melamine resin.
The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

(Base film)
As the base film 52, a film having heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The surface resistance of the base film 52 is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film 52 is preferably 1 × 10 ¹⁹ Ω or less from the practical point of view.
The thickness of the base film 52 is preferably 5 μm or more and 200 μm or less, more preferably 6 μm or more and 25 μm or less, and more preferably 10 μm or more and 25 μm or less from the viewpoint of flexibility.

(Printed circuit)
Examples of the copper foil forming the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil, electrolytic copper foil and the like, and rolled copper foil is preferable from the viewpoint of flexibility.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, more preferably 18 μm or more and 35 μm or less.
The lengthwise ends (terminals) of the printed circuit 54 are not covered with the insulating film 60 or the electromagnetic wave shielding film 1 because of solder connection, connector connection, component mounting, and the like.

(Insulating film)
The insulating film 60 is formed by forming an adhesive layer (not shown) on one surface of a base film (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the base film is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film is preferably 1 × 10 ¹⁹ Ω or less from the practical point of view.
As the substrate film, a film having heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The thickness of the base film is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 25 μm or less from the viewpoint of flexibility.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, acrylic resin, melamine resin, polystyrene and polyolefin. The epoxy resin may include a rubber component (carboxyl-modified nitrile rubber or the like) for imparting flexibility.
The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, and more preferably 1.5 μm or more and 60 μm or less.

  The shape of the opening of the through hole is not particularly limited. Examples of the shape of the opening of the through hole 62 include a circle, an ellipse, and a quadrangle.

(Method for manufacturing printed wiring board with electromagnetic wave shielding film)
The printed wiring board with an electromagnetic wave shielding film of the present invention can be produced, for example, by a method having the following steps (d) to (g).
Step (d): A step of providing a printed wiring board with an insulating film by providing an insulating film having through holes formed at positions corresponding to the printed circuit on the surface of the printed wiring board on which the printed circuit is provided.
Step (e): After step (d), the conductive adhesive layer is brought into contact with the surface of the insulating film between the printed wiring board with the insulating film and the electromagnetic wave shielding film of the present invention from which the second release film has been peeled off. And then heat-pressing these to bond the conductive adhesive layer to the surface of the insulating film, and the conductive adhesive layer is electrically connected to the printed circuit through the through-hole to prevent electromagnetic waves. The process of obtaining a printed wiring board with a shield film.
Step (f): A step of peeling the first release film after the step (e) when the first release film is no longer needed.
Step (g): A step of main curing the anisotropic conductive adhesive layer between step (e) and step (f) or after step (f), if necessary.

  Hereinafter, a method for manufacturing the flexible printed wiring board with the electromagnetic wave shielding film will be described with reference to FIG.

(Process (d))
As shown in FIG. 5, an insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is overlaid on the flexible printed wiring board 50, and an adhesive layer of the insulating film 60 is formed on the surface of the flexible printed wiring board 50. By bonding (not shown) and curing the adhesive layer, the flexible printed wiring board 3 with an insulating film is obtained. The adhesive layer of the insulating film 60 may be temporarily adhered to the surface of the flexible printed wiring board 50, and the adhesive layer may be fully cured in the step (g).
Adhesion and curing of the adhesive layer are performed, for example, by hot pressing using a pressing machine (not shown) or the like.

(Process (e))
As shown in FIG. 5, the electromagnetic shielding film 1 from which the second release film 40 has been peeled off is placed on the flexible printed wiring board 3 with an insulating film, and hot-pressed to make the surface of the insulating film 60 anisotropically conductive. The flexible printed wiring board 2 with an electromagnetic wave shielding film is obtained in which the adhesive layer 24 is adhered and the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62.

The anisotropic conductive adhesive layer 24 is adhered and cured by, for example, hot pressing using a pressing machine (not shown) or the like.
The time of hot pressing is 20 seconds or more and 60 minutes or less, and more preferably 30 seconds or more and 30 minutes or less. When the time of hot pressing is not less than the lower limit value of the above range, the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60. If the time of hot pressing is not more than the upper limit value of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.

  The temperature of the hot press (the temperature of the hot plate of the press) is preferably 140 ° C or higher and 190 ° C or lower, and more preferably 150 ° C or higher and 175 ° C or lower. When the temperature of hot pressing is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60. In addition, the time of hot pressing can be shortened. When the temperature of the hot press is equal to or lower than the upper limit value of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like can be suppressed.

  The pressure of the hot press is preferably 0.5 MPa or more and 20 MPa or less, more preferably 1 MPa or more and 16 MPa or less. If the pressure of the hot press is equal to or higher than the lower limit value of the above range, the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60. In addition, the time of hot pressing can be shortened. If the pressure of the hot press is equal to or lower than the upper limit value of the above range, it is possible to suppress damage to the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like.

(Process (f))
As shown in FIG. 5, when the first release film is no longer needed, the first release film 30 is peeled from the insulating resin layer 10.

(Process (g))
When the time of hot pressing in the step (e) is a short time of 20 seconds or more and 10 minutes or less, the anisotropic conductive adhesive layer is provided between the step (e) and the step (f) or after the step (f). It is preferable to perform 24 main curings.
The main curing of the anisotropic conductive adhesive layer 24 is performed using a heating device such as an oven.
The heating time is 15 minutes or more and 120 minutes or less, and preferably 30 minutes or more and 60 minutes or less. When the heating time is at least the lower limit value of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. If the heating time is not more than the upper limit of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.
The heating temperature (ambient temperature in the oven) is preferably 120 ° C or higher and 180 ° C or lower, and more preferably 120 ° C or higher and 150 ° C or lower. When the heating temperature is at least the lower limit value of the above range, the heating time can be shortened. When the heating temperature is equal to or lower than the upper limit value of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like can be suppressed.
It is preferable to perform heating without pressurization, because a special device does not have to be used.

(Effect)
In the flexible printed wiring board 2 with the electromagnetic wave shielding film described above, since the electromagnetic wave shielding film 1 is used, the flexible print is passed through the through hole 62 of the insulating film 60 provided on the surface of the flexible printed wiring board 50. The conductive adhesive layer of the electromagnetic wave shielding film 1 is surely electrically connected to the printed circuit 54 of the wiring board 50.

(Other embodiments)
The printed wiring board with an electromagnetic wave shielding film of the present invention includes a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided, a conductive layer adjacent to the insulating film, and a conductive film. Any layer may be used as long as it has an electromagnetic wave shielding film electrically connected to a printed circuit through a through hole formed in the insulating film, and the embodiment is not limited to the illustrated embodiment.
For example, the flexible printed wiring board may have a ground layer on the back surface side. Further, the flexible printed wiring board may have printed circuits on both sides, and an insulating film and an electromagnetic wave shielding film may be attached to both sides.
Instead of the flexible printed wiring board, an inflexible rigid printed board may be used.
The electromagnetic wave shielding film 1 of the second embodiment may be used instead of the electromagnetic wave shielding film 1 of the first embodiment.

  Examples will be shown below. The present invention is not limited to the embodiments.

(Hardness of metal thin film layer by nanoindentation method)
The hardness of the metal thin film layer by the nano indentation method is the above-mentioned nano indentation method (continuous stiffness) using an ultra-micro hardness meter (Nano Indenter XP, manufactured by MTS systems) and a diamond triangular pyramid indenter as an indenter. Measurement method) was used, and it was determined from the measurement results by the above-described calculation method.

(10% compressive strength of conductive particles)
The 10% compressive strength of the conductive particles was obtained from the measurement result using a micro compression tester (manufactured by Shimadzu Corporation, MCT-510) by the formula (11).

(Storage elastic modulus)
The storage elastic modulus was measured by using a dynamic viscoelasticity measuring device (RSII manufactured by Rheometric Scientific, Inc.) under the conditions of temperature: 180 ° C., frequency: 1 Hz, temperature rising rate: 10 ° C./min.

(Electrical connection)
By the step (f) described later, the connection resistance between the ground of the printed circuit 54 corresponding to the position where the through hole 62 is formed and the metal thin film layer 22 of the electromagnetic wave shielding film 1 is measured and evaluated according to the following criteria. did.
⊚ (excellent): The connection resistance is less than 0.5Ω.
◯ (Good): The connection resistance is 0.5Ω or more and less than 1Ω.
X (Poor): The connection resistance is 1Ω or more.

(Example 1)
As the first release film 30 and the second release film 40, a polyethylene terephthalate film (T157, manufactured by Lintec Co., thickness: 50 μm, at 180 ° C.) one side of which has been release-treated with a non-silicone release agent is used. Storage elastic modulus: 5 × 10 ⁸ Pa) was prepared.

  As the paint, 100 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER (registered trademark) 828), 15 parts by mass of a curing agent (N-aminopiperazine), and 5 parts by mass of carbon black are used as a solvent (methyl ethyl ketone). A coating material dissolved in 200 parts by mass of was prepared.

  As the thermosetting conductive adhesive composition, 100 parts by mass of the thermosetting adhesive 24a (epoxy resin (manufactured by DIC, EXA-4816) and 15 parts by mass of curing agent (PN-23 manufactured by Ajinomoto Fine-Techno Co., Ltd.). Curable epoxy resin), and 40 parts by mass of conductive particles 24b (copper particles, average particle size: 8 μm, 10% compressive strength: 85.1 MPa) are mixed with 200 parts of a solvent (methyl ethyl ketone). What was melt | dissolved or disperse | distributed in the mass part was prepared.

Step (a):
The coating material is applied to the surface of the release agent layer 34 of the first release film 30, heated at 60 ° C. for 2 minutes and semi-cured, and the insulating resin layer 10 (thickness: 10 μm, storage elastic modulus at 180 ° C.) 1.9 × 10 ⁷ Pa) was formed.

Step (b1):
Copper is physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a metal thin film layer 22 (deposited film, thickness: 300 nm, surface resistance: 0.07 Ω, hardness by nanoindentation method: 0.66 GPa) was formed.

Step (b2):
The thermosetting conductive adhesive composition is applied to the surface of the metal thin film layer 22 by using a die coater, and the solvent is volatilized to form the B-stage, whereby the anisotropic conductive adhesive layer 24 (thickness: 7 μm, copper particles: 4.5% by volume, storage elastic modulus at 180 ° C .: 2 × 10 ⁴ Pa).

Step (c):
The second release film 40 was attached to the surface of the anisotropic conductive adhesive layer 24 to obtain the electromagnetic wave shielding film 1.

Step (d):
An insulating adhesive composition composed of a nitrile rubber-modified epoxy resin is applied to the surface of a 12 μm-thick polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film) so that the dry film thickness is 12 μm. Then, an adhesive layer was formed to obtain an insulating film 60 (thickness: 25 μm). A through hole 62 (hole diameter: 2 mm) was formed at a position corresponding to the ground of the printed circuit 54.

A flexible printed wiring board 50 having a printed circuit 54 formed on the surface of a polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film 52) having a thickness of 12 μm was prepared.
An insulating film 60 was attached to the flexible printed wiring board 50 by hot pressing to obtain a flexible printed wiring board 3 with an insulating film.

Process (e):
The electromagnetic shield film 1 from which the second release film 40 has been peeled off is stacked on the flexible printed wiring board 3 with an insulating film, and a hot press machine (G-12 manufactured by Orihara Manufacturing Co., Ltd.) is used to heat the platen at a temperature of 170 ° C. A pressure was applied at a pressure of 2 MPa for 60 seconds to temporarily bond the anisotropic conductive adhesive layer 24 to the surface of the insulating film 60 to obtain a flexible printed wiring board 2 with an electromagnetic wave shielding film.

Process (f):
The anisotropic conductive adhesive layer 24 was fully cured by heating the flexible printed wiring board 2 with an electromagnetic wave shielding film 2 at a temperature of 160 ° C. for 1 hour using a high temperature incubator (HT210 manufactured by Kusumoto Kasei Co., Ltd.). .. The first release film 30 was peeled from the insulating resin layer 10.
The connection resistance between the ground of the printed circuit 54 corresponding to the position where the through hole 62 was formed and the metal thin film layer 22 of the electromagnetic wave shielding film 1 was measured. The results are shown in Table 1.

(Examples 2-5, Comparative Examples 1-2)
Example 1 except that the type of metal forming the metal thin film layer 22, the thickness of the metal thin film layer 22, the type of conductive particles 24b, and the average particle size of the conductive particles 24b were changed as shown in Table 1. Similarly, an electromagnetic wave shield film 1 was obtained. Further, a flexible printed wiring board 2 with an electromagnetic wave shielding film was obtained in the same manner as in Example 1 except that the electromagnetic wave shielding film 1 was changed. The connection resistance between the ground of the printed circuit 54 corresponding to the position where the through hole 62 was formed and the metal thin film layer 22 of the electromagnetic wave shielding film 1 was measured. The results are shown in Table 1.

In Examples 1 to 5 in which the thickness of the metal thin film layer 22 is in the range of 150 nm to 400 nm, the connection resistance between the ground of the printed circuit 54 and the metal thin film layer 22 of the electromagnetic wave shielding film 1 is low, and the conductivity is low. The adhesive layer was surely electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film.
In Example 5 in which silver was used as both the metal forming the metal thin film layer 22 and the metal forming the conductive particles 24b, the connection resistance was slightly higher.

  The electromagnetic wave shielding film of the present invention is useful as an electromagnetic wave shielding member in a flexible printed wiring board for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game machines, notebook computers and medical instruments.

1 Electromagnetic Wave Shielding Film 2 Flexible Printed Wiring Board with Electromagnetic Wave Shielding Film 3 Flexible Printed Wiring Board with Insulating Film 10 Insulating Resin Layer 20 Conductive Layer 22 Metal Thin Film Layer 24 Anisotropic Conductive Adhesive Layer 24a Thermosetting Adhesive 24b Conductive Particles 26 isotropic conductive adhesive layer 26a thermosetting adhesive 26b conductive particles 30 first release film 32 release film main body 34 release agent layer 40 second release film 42 release film main body 44 release Agent layer 50 Flexible printed wiring board 52 Base film 54 Printed circuit 60 Insulating film 62 Through hole 101 Flexible printed wiring board with electromagnetic wave shielding film 110 Electromagnetic wave shielding film 112 Insulating resin layer 114 Metal thin film layer 116 Conductive adhesive layer 118 First Release film 130 Flexible printed wiring board 132 Base film 134 Printed circuit 140 Insulation film 142 Through hole

Claims (8)

An insulating resin layer,
A metal thin film layer adjacent to the insulating resin layer,
A conductive adhesive layer adjacent to the insulating resin layer on the side opposite to the metal thin film layer,
A first release film adjacent to the side opposite to the metal thin film layer of the insulating resin layer,
The thickness of the metal thin film layer state, and are more 400nm or less 150 nm,
The hardness of the metal thin film layer by the nanoindentation method is 0.46 GPa or more and 1.0 GPa or less,
The electromagnetic wave shielding film , wherein the conductive adhesive layer contains conductive particles, and the 10% compressive strength of the conductive particles is 50 MPa or more and 100 MPa or less . Metal constituting the metal and the metal particles constituting the front Symbol metal thin film layer is a copper, electromagnetic wave shielding film according to claim 1. The metal thin film layer is a vapor-deposited film, an electromagnetic wave shielding film according to claim 1 or 2. The conductive adhesive layer a storage elastic modulus at 180 ° C. of, 1 × is ¹⁰ 3 Pa or more 5 × ¹⁰ 7 Pa or less, the electromagnetic wave shielding film according to any one of claims 1-3. It said first storage modulus at 180 ° C. of the release film, 8 × or less ¹⁰ 7 Pa or more 5 × ¹⁰ 9 Pa, electromagnetic wave shielding film according to any one of claims 1-4. The storage modulus at 180 ° C. of the insulating resin layer, 5 × or less ¹⁰ 6 Pa or more 5 × 10 ⁹ Pa, electromagnetic wave shielding film according to any one of claims 1-5. The said metal thin film of the conductive adhesive layer further comprises a second release film adjacent to the opposite side, an electromagnetic wave shielding film according to any one of claims 1-6. A printed wiring board provided with a printed circuit on at least one surface of the substrate;
An insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided,
The conductive adhesive layer is adjacent to the insulating film, and the conductive adhesive layer is the insulating film through the through-hole formed in claim 1 to 6 which is electrically connected to the printed circuit A printed wiring board with an electromagnetic wave shielding film, comprising: the electromagnetic wave shielding film according to any one of items.

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