CN207124801U - Electromagnetic shielding film and the printing distributing board with electromagnetic shielding film - Google Patents

Abstract

The utility model provides an electromagnetic wave shielding film and a printed wiring board with the electromagnetic wave shielding film. The electromagnetic wave shielding film can be reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film arranged on the surface of the printed wiring board. . The electromagnetic wave shielding film has: an insulating resin layer (10); a metal thin film layer (22), adjacent to the insulating resin layer (10); an anisotropic conductive adhesive layer (24), and the metal thin film layer (22). The opposite side of the insulating resin layer (10) is adjacent; and the first release film (30), adjacent to the opposite side of the insulating resin layer (10) and the metal film layer (22), the metal film layer (22) The thickness is not less than 150 nm and not more than 400 nm.

Description

Electromagnetic wave shielding film and printed wiring board with electromagnetic wave shielding film

technical field

The utility model relates to an electromagnetic wave shielding film and a printed wiring board provided with the electromagnetic wave shielding film.

Background technique

In order to shield the electromagnetic wave noise generated from the flexible printed wiring board and the electromagnetic wave noise from the outside, an electromagnetic wave shielding film is sometimes provided on the surface of the flexible printed wiring board. The electromagnetic wave shielding film includes: an insulating resin layer; A conductive layer composed of a metal thin film layer and a conductive adhesive layer (for example, refer to Patent Documents 1 and 2).

6 is a cross-sectional view illustrating an example of a conventional manufacturing process of a flexible printed wiring board with an electromagnetic wave shielding film.

Flexible printed wiring board 101 with electromagnetic wave shielding film includes flexible printed wiring board 130 , insulating film 140 , and electromagnetic wave shielding film 110 from which first release film 118 was peeled off.

In flexible printed wiring board 130 , printed circuit 134 is provided on one surface of base film 132 .

The insulating film 140 is provided on the surface of the flexible printed wiring board 130 on which 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 side opposite to the insulating resin layer 112 of the metal thin film layer 114; A release film 118 (carrier film) adjoins the side of the insulating resin layer 112 opposite to the metal thin film layer 114 .

The conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is adhered to the surface of the insulating film 140 and cured. In addition, 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 an electromagnetic wave shielding film is manufactured through the following process as shown in FIG. 6, for example.

Step (i): The step of forming insulating film 140 on the surface of flexible printed wiring board 130 on which printed circuit 134 is provided, and forming through hole 142 in position corresponding to the ground of printed circuit 134 in insulating film 140 .

Step (ii): The electromagnetic wave shielding film 110 is superimposed on the surface of the insulating film 140 in such a manner that the conductive adhesive layer 116 of the electromagnetic wave shielding film 110 contacts the surface of the insulating film 140, and the conductive adhesive is formed by hot pressing them. A process of bonding the mixture layer 116 to the surface of the insulating film 140 and electrically connecting the conductive adhesive layer 116 to the ground of the printed circuit 134 through the through hole 142 .

Step (iii): After hot pressing, the first release film 118 that has completed its role as a carrier film is peeled and removed from the insulating resin layer 112 to obtain the flexible printed wiring board 101 with an electromagnetic wave shielding film.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2000-269632

Patent Document 2: Japanese Patent Laid-Open No. 2015-109404

Utility model content

Technical problems to be solved by utility models

However, when the conductive adhesive layer of the electromagnetic wave shielding film is bonded to the printed circuit of the printed wiring board through the through-hole of the insulating film, the bonding between the ground wire and the conductive adhesive layer tends to become insufficient. full. For this reason, when the first release film is peeled from the insulating resin layer, or when the flexible printed wiring board with an electromagnetic wave shielding film is heated at high temperature to completely cure the conductive adhesive layer, there is a gap between the ground wire and the conductive adhesive layer. The mixture layer is prone to peeling off. For this reason, the connection resistance between the ground wire and the conductive adhesive layer increases, and electrical connection may not be reliably performed.

The utility model provides an electromagnetic wave shielding film and a printed wiring board with the electromagnetic wave shielding film. The electromagnetic wave shielding film can be reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film arranged on the surface of the printed wiring board. , in the printed wiring board with electromagnetic wave shielding film, the conductive adhesive layer of the electromagnetic wave shielding film is reliably 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 .

Solutions for technical problems

The utility model has the following aspects.

[1] The electromagnetic wave shielding film has: an insulating resin layer; a metal thin film layer adjacent to the insulating resin layer; a conductive adhesive layer adjacent to a side of the metal thin film layer opposite to the insulating resin layer; And the first release film is adjacent to the side of the insulating resin layer opposite to the metal thin film layer, and the thickness of the metal thin film layer is not less than 150 nm and not more than 400 nm.

[2] In the electromagnetic wave shielding film described in [1], the thickness of the insulating resin layer is not less than 0.1 μm and not more than 30 μm.

[3] In the electromagnetic wave shielding film described in [1] or [2], the conductive adhesive layer contains conductive particles having an average particle diameter of 2 μm or more and 26 μm or less, and the conductive adhesive layer The thickness is not less than 3 μm and not more than 25 μm.

[4] In the electromagnetic wave shielding film described in [1] or [2], the conductive adhesive layer contains conductive particles having an average particle diameter of 0.1 μm or more and 10 μm or less, and the conductive adhesive The thickness of the layer is not less than 5 μm and not more than 20 μm.

[5] A printed wiring board with an electromagnetic shielding film comprising: a printed wiring board having a printed circuit on at least one side of a substrate; and an insulating film on the side of the printed wiring board on which the printed circuit is provided surface adjoining; and the electromagnetic wave shielding film described in [1] or [2], the conductive adhesive layer of the electromagnetic wave shielding film is adjacent to the insulating film, and the conductive adhesive layer passes through The through hole formed in the insulating film is electrically connected to the printed circuit.

[6] In the printed wiring board with an electromagnetic shielding film described in [5], a portion of the insulating resin layer above the through hole is recessed toward the through hole.

Utility Model Effect

The electromagnetic wave shielding film of the present invention can reliably be 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.

In the printed wiring board with electromagnetic wave shielding film of the present invention, the conductive adhesive layer of the electromagnetic wave shielding film is reliably electrically connected to the printed wiring board through the through hole of the insulating film provided on the surface of the printed wiring board. printed circuit.

Description of drawings

FIG. 1 is a cross-sectional view showing one embodiment of the electromagnetic wave shielding film of the present invention.

Fig. 2 is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film of the present invention.

Fig. 3 is a cross-sectional view illustrating a manufacturing process of the electromagnetic wave shielding film of Fig. 1 .

Fig. 4 is a cross-sectional view showing an embodiment of a printed wiring board with an electromagnetic shielding film of the present invention.

Fig. 5 is a cross-sectional view showing a manufacturing process of the printed wiring board with an electromagnetic wave shielding film shown in Fig. 4 .

6 is a cross-sectional view illustrating an example of a conventional manufacturing process of a flexible printed wiring board with an electromagnetic wave shielding film.

Detailed ways

The following definitions of terms apply to the present specification and claims.

The "isotropic conductive adhesive layer" refers to a conductive adhesive layer having conductivity in the thickness direction and the surface direction.

The "anisotropic conductive adhesive layer" refers to a conductive adhesive layer having conductivity in the thickness direction but not having conductivity in the plane direction.

The "conductive adhesive layer having no conductivity in the plane direction" refers to a conductive adhesive layer having a surface resistance of 1×10 ⁴ Ω or more.

The average particle diameter of conductive particles is 30 conductive particles randomly selected from the microscope image of conductive particles, the minimum diameter and maximum diameter are measured for each conductive particle, and the median value of the minimum diameter and maximum diameter is taken as the average value of one particle. Particle size, and the value obtained by arithmetically averaging the measured particle sizes of 30 conductive particles.

The thickness of the film (release film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), metal thin film layer, etc. is measured by observing the cross-section of the measurement object with a microscope and measuring the thickness of five parts and averaging them. And get the value.

The storage modulus is calculated from the stress applied to the measurement object and the detected strain, and is measured as one of the viscoelastic properties using a dynamic viscoelasticity measuring device whose output is a function of temperature or time.

The surface resistance is obtained by using two thin-film metal electrodes (length 10mm, width 5mm, and distance between electrodes 10mm) formed by evaporating gold on quartz glass. The object to be measured is placed on the electrodes, and a load of 0.049N is applied from above the object to be measured. Press the area of 10mm x 20mm on the object to be measured, and measure the resistance between electrodes under the measurement current of 1mA or less.

The hardness of the metal thin film layer based on the nanoindentation (nanoindentation) method is measured by the following nanoindentation method (continuous stiffness measurement method) using an ultramicrohardness tester, and using a diamond triangular cone indenter as the indenter. Calculated from the measurement results by the following calculation method.

The indentation load/unloading test was carried out on the metal film layer using a triangular cone indenter (Berkovich indenter), and a load-displacement (indentation depth) curve was obtained.

The hardness H at the maximum load is defined by the following equation (1) using the load P and the projected area A of the indentation remaining after the elastic deformation is partially recovered after pressing.

H=P/A (1)

The projected area A of the indentation was obtained by the following formula (2).

A=ηkh _c ² (2)

Among them, η is a correction coefficient for the shape of the front end of the indenter, k is a constant obtained from the geometric shape of the indenter, k=24.56 in the Berkovich indenter, and _hc is the effective contact depth, which is represented by the following formula (3).

h _c = h－ε{c/(dP/dh)} (3)

Among them, h is the total displacement measured, dP/dh is the initial gradient at the time of unloading in the obtained load-displacement (indentation depth) curve, ε is a constant obtained according to the geometry of the indenter. 0.75 in the head.

Based on the formula (1), formula (2) and formula (3), the hardness at the maximum load P _max was calculated from the following formula (4).

H＝P _max /(ηkh _c ² ) (4)

dP/dh in the formula (3) was calculated by the following nanoindentation method (continuous stiffness measurement method).

The continuous stiffness measurement method is to vibrate the indenter slightly during the indentation test, obtain the response amplitude and phase difference relative to the vibration as a function of time, and continuously calculate dP/dh corresponding to the continuous change of the indentation depth . The principle is shown below.

The total force (detection load component) F(t) of the direction in which the indenter penetrates into the metal thin film layer is expressed by the following formula (5).

F(t)＝m(d ² h/dt ² )+D(dh/dt)+Kh (5)

Among them, the first term of formula (5) is the force derived from the indenter shaft (m: mass of the indenter shaft), and the second term of formula (5) is derived from the viscous component of the metal film layer and the indenter system Force (D: Loss constant), the third term of Equation (5) is the combination of the metal film layer, the compliance of the load frame (load frame), and the stiffness of the leaf spring supporting the indenter shaft After the force (K: composite stiffness), t is time. D and K in the formula (5) are represented by the following formulas (6) and (7).

K＝{(dh/dP)+C _r } ^－1 +K _s (6)

D＝D _s +D _i (7)

where C _r is the compliance of the load frame, K _s is the stiffness of the leaf spring supporting the indenter shaft, D _s is the loss constant of the indenter system, and D _i is the loss constant of the metal film layer.

In addition, since F(t) of the formula (5) depends on time, it is represented as the following formula (8).

F(t)＝F ₀ exp(iωt) (8)

where _F0 is a constant and ω is the angular vibration frequency. When the equation is solved by substituting equation (8) into equation (5) and equation (9) below which is a special solution of an ordinary differential equation, dP/dh is calculated as in equation (10) below.

in, is the phase difference. In formula (10), since _Cr , m, and K _s are known at the time of measurement, when measuring the metal thin film layer, the vibration amplitude (h ₀ ) and phase difference of the measurement displacement and the excitation vibration amplitude (F ₀ ), dP/dh can be continuously calculated corresponding to the continuous change of the indentation depth according to the formula (10). Therefore, the hardness of the metal thin film layer can be calculated by substituting the calculated value into the formula (3).

The 10% compressive strength of electroconductive particle was calculated|required by following formula (11) from the measurement result using the microcompression tester.

C(x)＝2.48P/πd ² (11)

Here, C(x) is the 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 shielding film＞

FIG. 1 is a cross-sectional view showing the first embodiment of the electromagnetic wave shielding film of the present invention, and FIG. 2 is a cross-sectional view showing the second embodiment of the electromagnetic wave shielding film of the present invention.

The electromagnetic wave shielding film 1 of the first embodiment and the second embodiment has: an insulating resin layer 10; a conductive layer 20, adjacent to the insulating resin layer 10; a first release (release) film 30, and the insulating resin layer 10 The opposite side of the conductive layer 20 is adjacent; and the second release (release) film 40 is adjacent to the opposite side of the conductive layer 20 to the insulating resin layer 10 .

The electromagnetic wave shielding film 1 of the first embodiment is an example in which the conductive layer 20 has 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 .

The electromagnetic shielding film 1 of the second embodiment is an example in which the conductive layer 20 has 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 .

(insulating resin layer)

The insulating resin layer 10 serves as a base (priming) when forming the metal thin film layer 22, and becomes a protective layer of the metal thin film layer 22 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. .

As the insulating resin layer 10 , a coating film formed by applying a coating containing a thermosetting resin and a curing agent and semi-curing or curing it is preferable from the viewpoint of heat resistance during reflow soldering or the like.

Examples of thermosetting resins include polyamide resins, epoxy resins, phenolic resins, amino resins, alkyd resins, polyurethane resins, synthetic rubbers, and ultraviolet-curable acrylate resins. As the thermosetting resin, polyamide resin and epoxy resin are preferable from the viewpoint of excellent heat resistance.

Examples of the curing agent include known curing agents corresponding to the type of thermosetting resin.

The storage modulus at 180°C of the insulating resin layer 10 before hot pressing is preferably 5×10 ⁶ Pa to 5×10 ⁹ Pa, more preferably 1×10 ⁷ Pa to 1×10 ⁹ Pa. When the storage modulus at 180° C. of the insulating resin layer 10 is equal to or greater than the lower limit of the above range, the insulating resin layer 10 has more appropriate hardness, and the pressure loss in the insulating resin layer 10 during hot pressing can be further reduced. As a result, the conductive adhesive layer is more fully bonded to the printed circuit of the printed wiring board, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through-hole of the insulating film. The flexibility of the electromagnetic wave shielding film 1 will become more favorable as the storage elastic modulus in 180 degreeC of the insulating resin layer 10 is below the upper limit of the said range. As a result, the electromagnetic shielding film 1 sinks more easily into the through-holes of the insulating film, 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.

The insulating resin layer 10 may be colored in order to impart designability to the printed wiring board with the electromagnetic shielding film.

The unevenness of the first release film 30 embossed or blasted may be transferred onto the surface of the insulating resin layer 10 in order not to conspicuous scratches or the like on the surface of the insulating resin layer 10 .

The insulating resin layer 10 may also contain other components (flame retardant, etc.).

From the viewpoint of electrical insulation, the surface resistance of the insulating resin layer 10 is preferably 1×10 ⁶ Ω or more. From a practical point of view, the surface resistance of the insulating resin layer 10 is preferably 1×10 ¹⁹ Ω or less.

The thickness of the insulating resin layer 10 is preferably not less than 0.1 μm and not more than 30 μm, more preferably not less than 0.5 μm and not more than 20 μm. The insulating resin layer 10 can fully exhibit the function as a protective layer as the thickness of the insulating resin layer 10 is more than the lower limit of the said range. The electromagnetic wave shielding film 1 can be thinned as the thickness of the insulating resin layer 10 is below the upper limit of the said range.

(conductive layer)

As the conductive layer 20, a conductive layer (I) or a conductive layer (II) can be mentioned, and the conductive layer (I) has a metal thin film layer 22 adjacent to the insulating resin layer 10 and a layer opposite to the insulating resin layer 10 in the conductive layer 20. As the conductive adhesive layer (anisotropic conductive adhesive layer 24 or isotropic conductive adhesive layer 26) on the side as the outermost layer, the conductive layer (II) is only bonded by isotropic conductive adhesive Agent layer 26 constitutes. In the present invention, as the conductive layer 20 , the conductive layer (I) is employed from the viewpoint of being able to sufficiently function as an electromagnetic wave shielding layer.

(metal thin film layer)

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

Examples of the metal thin film layer 22 include vapor deposition films formed by physical vapor deposition (vacuum deposition, sputtering, ion beam deposition, electron beam deposition, etc.) or CVD, plated films formed by electroplating, and metal foils. From the point of view of excellent electrical conductivity in the plane direction, vapor-deposited films and plated films are preferred, and from the perspective that the thickness can be made thinner, the electrical conductivity in the plane direction is excellent even if the thickness is thin, and it can be easily formed by a dry process. A vapor-deposited film is preferable, and a vapor-deposited film by physical vapor deposition is more preferable.

Examples of the metal constituting 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, the metal thin film layer 22 has moderate hardness, and the pressure loss in the metal thin film layer 22 can be reduced during hot pressing.

The hardness of the metal thin film layer 22 by the nanoindentation method is preferably not less than 0.3 GPa and not more than 2.0 GPa, more preferably not less than 0.4 GPa and not more than 1.5 GPa, still more preferably not less than 0.5 GPa and not more than 1.0 GPa. When the hardness of the metal thin film layer 22 by the nanoindentation method is above the lower limit of the above range, the metal thin film layer 22 has a more moderate hardness, and the pressure loss in the metal thin film layer 22 during hot pressing can be further reduced. As a result, the conductive adhesive layer is more fully bonded to the printed circuit of the printed wiring board, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through-hole of the insulating film. When the hardness by the nanoindentation method of the metal thin film layer 22 is below the upper limit of the said range, the flexibility of the electromagnetic wave shielding film 1 will become more favorable. As a result, the electromagnetic shielding film 1 sinks more easily into the through-holes of the insulating film, 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.

The surface resistance of the metal thin film layer 22 is preferably not less than 0.001Ω and not more than 1Ω, more preferably not less than 0.001Ω and not more than 0.1Ω. If the surface resistance of the metal thin film layer 22 is more than the lower limit value of the said range, the metal thin film layer 22 can be made thin enough. If the surface resistance of the metal thin film layer 22 is below the upper limit of the said range, it can fully function as an electromagnetic wave shielding layer.

The thickness of the metal thin film layer 22 is not less than 150 nm and not more than 400 nm, preferably not less than 200 nm and not more than 350 nm, more preferably not less than 250 nm and not more than 300 nm. When the thickness of the metal thin film layer 22 is more than the lower limit of the above-mentioned range, the metal thin film layer 22 has moderate 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 bonded, 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 flexibility of the electromagnetic wave shielding film 1 will be favorable as the thickness of the metal thin film layer 22 is below the upper limit of the said range. As a result, the electromagnetic shielding film 1 sinks easily into the through-holes 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-holes of the insulating film.

(conductive adhesive layer)

The conductive adhesive layer has conductivity and adhesiveness at least in the thickness direction.

Examples of the conductive adhesive layer include an anisotropic conductive adhesive layer 24 having conductivity in the thickness direction but not having conductivity in the plane direction, or an anisotropic conductive adhesive layer 24 having conductivity in both the thickness direction and the plane direction. Isotropic conductive adhesive layer 26 . As the conductive adhesive layer in the conductive layer (I), the anisotropic conductive adhesive layer 24 is preferable from the following viewpoints.

·The conductive adhesive layer has more appropriate hardness, which can further reduce the pressure loss in the conductive adhesive layer at the time of hot pressing.

·The conductive adhesive layer can be made thinner, and the amount of conductive particles can be reduced. As a result, the electromagnetic wave shielding film 1 can be made thinner, and the flexibility of the electromagnetic wave shielding film 1 is good.

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 shielding layer.

As the conductive adhesive layer, a thermosetting conductive adhesive layer is preferable from the viewpoint of exhibiting 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 anisotropic conductive adhesive layer 24 may contain 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 contain a flame retardant as needed.

Examples of thermosetting adhesives include epoxy resins, phenolic resins, amino resins, alkyd resins, polyurethane resins, synthetic rubbers, and ultraviolet-curable acrylate resins. From the viewpoint of excellent heat resistance, epoxy resin is preferable. The epoxy resin may also contain a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.), a tackifier, and the like for imparting flexibility.

In order to increase the strength of the conductive adhesive layer and improve the stamping characteristics, the thermosetting adhesive may contain cellulose resin, microfiber (microfibril, glass fiber, etc.).

Examples of the conductive particles include metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, graphite powder, calcined carbon particles, and plated calcined carbon particles. As the electroconductive particles, metal particles are preferable, and copper particles are more preferable because the electroconductive adhesive layer has more appropriate hardness and can further reduce pressure loss in the electroconductive adhesive layer during hot pressing.

The 10% compressive strength of the electroconductive particle is preferably 30 MPa to 200 MPa, more preferably 50 MPa to 150 MPa, still more preferably 70 MPa to 100 MPa. If the 10% compressive strength of the conductive particles is more than the lower limit of the above range, the pressure applied to the metal thin film layer 22 will not be greatly lost during hot pressing, and the conductive adhesive layer will pass through the through holes of the insulating film. A printed circuit that is electrically connected to a printed wiring board more reliably. If the 10% compressive strength of electroconductive particle is below the upper limit of the said range, contact with the metal thin film layer 22 will be favorable and electrical connection will be reliable.

The average particle diameter of the electroconductive particle 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, more preferably 4 μm or more and 16 μm or less. The thickness of the anisotropic electroconductive adhesive layer 24 can be ensured as the average particle diameter of the electroconductive particle 24b is more than the lower limit of the said range, and sufficient adhesive strength can be acquired. If the average particle diameter of the conductive particles 24b is below the upper limit of the above-mentioned range, the fluidity of the anisotropic conductive adhesive layer 24 (followability to the shape of the through-hole of the insulating film) can be ensured, and the conductivity can be used. The permanent adhesive fully fills the through-holes of the insulating film.

The average particle diameter of the electroconductive particle 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 1 μm or less. The number of contact points of the electroconductive particle 26b increases that the average particle diameter of the electroconductive particle 26b is more than the lower limit of the said range, and can improve the conductivity of a three-dimensional direction stably. If the average particle size of the conductive particles 26b is below the upper limit of the above-mentioned range, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through-hole of the insulating film) can be ensured, and the conductivity can be used. The permanent adhesive fully fills the through-holes of the insulating film.

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, more preferably 2% by volume, in 100% by volume of the anisotropic conductive adhesive layer 24. Volume % or more and 10 volume % or less. The electroconductivity of the anisotropic electroconductive adhesive layer 24 becomes favorable that the ratio of the electroconductive particle 24b is more than the lower limit of the said range. When the ratio of electroconductive particle 24b is below the upper limit of the said range, the adhesiveness of the anisotropic electroconductive adhesive layer 24 and fluidity (followability to the shape of the through-hole of an insulating film) will become favorable. In addition, the electromagnetic wave shielding film 1 has good flexibility.

The ratio 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, more preferably 60% by volume in 100% by volume of the isotropic conductive adhesive layer 26. Volume % or more and 70 volume % or less. The electroconductivity of the isotropic electroconductive adhesive layer 26 becomes favorable that the ratio of the electroconductive particle 26b is more than the lower limit of the said range. When the ratio of electroconductive particle 26b is below the upper limit of the said range, the adhesiveness of the isotropic electroconductive adhesive layer 26 and fluidity (followability to the through-hole shape of an insulating film) are favorable. In addition, the electromagnetic wave shielding film 1 has good flexibility.

The surface resistance of the anisotropic conductive adhesive layer 24 is preferably not less than 1×10 ⁴ Ω and not more than 1×10 ¹⁶ Ω, more preferably not less than 1×10 ⁶ Ω and not more than 1×10 ¹⁴ Ω. Content of the electroconductive particle 24b can be suppressed low as the surface resistance of the anisotropic electroconductive adhesive layer 24 is more than the lower limit of the said range.

When the surface resistance of the anisotropic electroconductive adhesive layer 24 is below the upper limit of the said range, there will be no problem practically in terms of anisotropy.

The surface resistance of the isotropic conductive adhesive layer 26 is preferably not less than 0.05Ω and not more than 2.0Ω, more preferably not less than 0.1Ω and not more than 1.0Ω. If the surface resistance of the isotropic conductive adhesive layer 26 is more than the lower limit of the above-mentioned range, the content of the conductive particles 26b can be suppressed at a low level, and the viscosity of the conductive adhesive will not be too high. Cloth is better. In addition, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through-hole of the insulating film) can be further ensured. If the surface resistance of the isotropic conductive adhesive layer 26 is below the upper limit of the said range, the whole surface of the isotropic conductive adhesive layer 26 will have uniform conductivity.

The storage modulus at 180° C. of the conductive adhesive layer is preferably not less than 1×10 ³ Pa and not more than 5×10 ⁷ Pa, more preferably not less than 5×10 ³ Pa and not more than 1×10 ⁷ Pa. If the storage modulus of the conductive adhesive layer at 180° C. is more than the lower limit of the above range, the conductive adhesive layer has a more moderate hardness, and the conductive adhesive layer can be further reduced during hot pressing. pressure loss in. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more fully bonded, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through-hole of the insulating film. . The flexibility of the electromagnetic wave shielding film 1 will become more favorable as the storage elastic modulus in 180 degreeC of a conductive adhesive layer is below the upper limit of the said range. As a result, the electromagnetic shielding film 1 sinks more easily into the through-holes of the insulating film, 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.

The thickness of the anisotropic conductive adhesive layer 24 is preferably not less than 3 μm and not more than 25 μm, more preferably not less than 5 μm and not more than 15 μm. When the thickness of the anisotropic conductive adhesive layer 24 is more than the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (followability to the shape of the through hole of the insulating film) can be ensured. Therefore, the inside of the through-hole of the insulating film can be sufficiently filled with the conductive adhesive. The electromagnetic wave shielding film 1 can be thinned as the thickness of the anisotropic conductive adhesive layer 24 is below the upper limit of the said range. In addition, the electromagnetic wave shielding film 1 has good flexibility.

The thickness of the isotropic conductive adhesive layer 26 is preferably not less than 5 μm and not more than 20 μm, more preferably not less than 7 μm and not more than 17 μm. When the thickness of the isotropic conductive adhesive layer 26 is more than the lower limit of the above-mentioned range, the conductivity of the isotropic conductive adhesive layer 26 is good, and it can fully function as an electromagnetic wave shielding layer. In addition, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through-hole of the insulating film) can be ensured, and the inside of the through-hole of the insulating film can be sufficiently filled with the conductive adhesive. The folding resistance can be ensured, and the isotropic conductive adhesive layer 26 will not be broken even if it is repeatedly bent. The electromagnetic wave shielding film 1 can be thinned as the thickness of the isotropic conductive adhesive layer 26 is below the upper limit of the said range. In addition, the electromagnetic wave shielding film 1 has good flexibility.

(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 shielding 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 main body 32 and a release agent layer 34 provided on the surface of the release film main body 32 on the insulating resin layer 10 side.

Examples of the resin material for the release film main body 32 include polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polybutylene terephthalate. , polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, etc., from the manufacture of electromagnetic wave shielding From the viewpoint of heat resistance (dimensional stability) and cost in the case of the film 1, polyethylene terephthalate is preferable.

The storage modulus at 180° C. of the release film main body 32 is preferably not less than 8×10 ⁷ Pa and not more than 5×10 ⁹ Pa, more preferably not less than 1×10 ⁸ Pa and not more than 8×10 ⁸ Pa. If the storage modulus at 180°C of the release film main body 32 is above the lower limit of the above-mentioned range, the first release film 30 will have a more moderate hardness, which can further reduce the hardness of the first release film 30 during hot pressing. pressure loss in. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more fully bonded, and the conductive adhesive layer is more reliably electrically connected to the printed circuit of the printed wiring board through the through-hole of the insulating film. . The flexibility of the electromagnetic wave shielding film 1 will become more favorable as the storage modulus in 180 degreeC of the release film main body 32 is below the upper limit of the said range. As a result, the electromagnetic shielding film 1 sinks more easily into the through-holes of the insulating film, 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.

The thickness of the release film main body 32 is preferably not less than 5 μm and not more than 500 μm, more preferably not less than 10 μm and not more than 150 μm, and still more preferably not less than 25 μm and not more than 100 μm. The handleability of the electromagnetic wave shielding film 1 becomes favorable that the thickness of the release film main body 32 is more than the lower limit of the said range. When the thickness of the release film main body 32 is below the upper limit 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 on the surface of the insulating film. .

The release agent layer 34 is a layer formed by subjecting the surface of the release film main body 32 to a release treatment with a release agent. Since the first release film 30 has a release agent layer 34, when the first release film 30 is peeled off from the insulating resin layer 10, the first release film 30 is easy to peel off, and the insulating resin layer 10 and the cured conductivity The adhesive layer is not easy to break.

As a mold release agent, what is necessary is just to use a well-known mold release agent.

The thickness of the release agent layer 34 is preferably not less than 0.05 μm and not more than 2.0 μm, more preferably not less than 0.1 μm and not more than 1.5 μm. When the thickness of the release agent layer 34 is within the above-mentioned range, it will be easier to peel the first release film 30 .

(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 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 has, for example, a release film main body 42 and a release agent layer 44 provided on the surface of the release film main body 42 on the side of the conductive adhesive layer.

As the resin material of the release film main body 42, the resin material similar to the resin material of the release film main body 32 is mentioned.

The thickness of the release film main body 42 is preferably not less than 5 μm and not more than 500 μm, more preferably not less than 10 μm and not more than 150 μm, and still more preferably not less than 25 μm and not more than 100 μm.

The release agent layer 44 is a layer 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 peeled off from the conductive adhesive layer, the second release film 40 is easily peeled off, and the conductive adhesive layer is not easily fracture.

As a mold release agent, what is necessary is just to use a well-known mold release agent.

The thickness of the release agent layer 34 is preferably not less than 0.05 μm and not more than 2.0 μm, more preferably not less than 0.1 μm and not more than 1.5 μm. When the thickness of the release agent layer 34 is within the above-mentioned range, it will be easier to peel the second release film 40 .

(thickness of electromagnetic wave shielding film)

The thickness of the electromagnetic wave shielding film 1 (excluding the mold release film) is preferably 10 μm to 45 μm, more preferably 10 μm to 30 μm. When the thickness (except the release film) of the electromagnetic wave shielding film 1 is more than the lower limit of the said range, when peeling the 1st release film 30, it will become difficult to break. The printed wiring board with an electromagnetic wave shielding film can be thinned as the thickness (except a mold release film) of the electromagnetic wave shielding film 1 is below the upper limit of the said range.

(Manufacturing method of electromagnetic wave shielding film)

The electromagnetic wave shielding film of this invention can be manufactured by the method (α) which has the following process (a)-(c), for example.

Step (a): a step of forming an insulating resin layer on one surface of the first release film.

Step (b): After step (a), a step of forming a conductive layer on the surface of the insulating resin layer.

Process (c): The process of affixing a 2nd release film to the surface of a conductive layer after process (b).

Moreover, the electromagnetic wave shielding film of this invention can be manufactured by the method (β) which has following process (a'), (b'1), (b'2), (c'), for example.

Step (a'): a step of forming an insulating resin layer on one surface of the first release film.

Step (b'1): A step of obtaining a first laminate having a first release film, an insulating resin layer, and a metal thin film layer in this order by forming a metal thin film layer on the surface of the insulating resin layer.

Step (b'2): A step of obtaining a second laminate having a second release film and a conductive adhesive layer in this order by forming a conductive adhesive layer on one side of the second release film.

Step (c'): a step of bonding the first laminate and the second laminate so that the metal thin film layer and the conductive adhesive layer are in contact with each other.

Next, a method of manufacturing the electromagnetic wave shielding film 1 shown in FIG. 1 by the method (α) will be described with reference to FIG. 3 .

Process (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 containing a thermosetting resin and a curing agent and semi-curing or curing it is preferable from the viewpoint of heat resistance during reflow soldering or the like.

The paint containing a thermosetting resin and a curing agent may also contain a solvent and other components (flame retardant, etc.) as necessary.

The storage modulus of the insulating resin layer 10 can be controlled by selecting the type and composition of the thermosetting resin, curing agent, etc., adjusting the curing conditions such as temperature and time when the thermosetting resin is semi-cured or solidified, adding as Thermoplastic resins such as thermoplastic elastomers with thermosetting components are used.

Process (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)).

The method of forming the metal thin film layer 22 includes a method of forming a deposited film by physical vapor deposition or CVD, a method of forming a plated film by electroplating, and a method of attaching a metal foil. From the viewpoint of being able to form the metal thin film layer 22 with excellent electrical conductivity in the plane direction, the method of forming an evaporated film by physical vapor deposition, CVD, or the method of forming an electroplated film by electroplating is preferred, and the thickness of the metal thin film layer 22 can be made relatively It is thin, and can form a metal thin film layer 22 with excellent electrical conductivity in the plane direction even if the thickness is thin, and can form the metal thin film layer 22 simply by a dry process, and it is more preferable to form a vapor-deposited film by physical vapor deposition or CVD. method, more preferably a method of forming a deposited film by physical vapor deposition.

As a method of forming the anisotropic conductive adhesive layer 24, a method of applying a thermosetting conductive adhesive composition to the surface of the metal thin film layer 22 is mentioned.

As a thermosetting conductive adhesive composition, what contains thermosetting adhesive 24a and electroconductive particle 24b is used.

The storage modulus of the anisotropic conductive adhesive layer 24 can be controlled similarly to the storage modulus of the insulating resin layer 10 .

Process (c):

As shown in FIG. 3, the 2nd release film 40 is stuck on the surface of the anisotropic conductive adhesive layer 24, and the electromagnetic wave shielding film 1 is obtained.

(Effect)

Regarding the electromagnetic wave shielding film 1 described above, since the metal thin film layer 22 has a thickness of 150 nm or more, the metal thin film layer 22 has moderate hardness and can reduce pressure loss in the metal thin film layer 22 during hot pressing. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are sufficiently bonded, 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. In addition, 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 good. As a result, the electromagnetic shielding film 1 sinks easily into the through-holes 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-holes of the insulating film.

(Other implementations)

The electromagnetic wave shielding film of the present utility model 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 sequence, and the thickness of the metal thin film layer can be more than 150nm and less than 400nm, and is not limited to The embodiment illustrated in the accompanying drawings.

For example, there may be two or more insulating resin layers.

When the tackiness of the surface of the conductive adhesive layer is small, the second release film 40 may be omitted.

When the release film has sufficient releasability only by the release film main body, it does not need to have a release agent layer.

The release film may have an adhesive layer instead of the release agent layer.

<Printed wiring boards with electromagnetic wave shielding film>

Fig. 4 is a cross-sectional view showing an embodiment of a printed wiring board with an electromagnetic shielding film of the present invention.

The flexible printed wiring board 2 with an electromagnetic wave shielding film includes the flexible printed wiring board 50, the insulating film 60, and the electromagnetic wave shielding film 1 of 1st Embodiment.

In the flexible printed wiring board 50 , 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 bonded to the surface of the insulating film 60 and cured. In addition, 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 an electromagnetic wave shielding film, the 2nd release film 40 is peeled from the anisotropic conductive adhesive layer 24.

When the first release film 30 is unnecessary in the flexible printed wiring board 2 with an electromagnetic wave shielding film, the first release film 30 is peeled from the insulating resin layer 10 .

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) 24 and separate and relatively configured.

The distance between the printed circuit 54 and the metal thin film layer 22 is substantially equal to the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24 excluding the portion having the through hole. The separation distance is preferably not less than 30 μm and not more than 200 μm, more preferably not less than 60 μm and not more than 200 μm. When the spacing distance is less than 30μm, 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 reduced. The unevenness of the line width leads to the unevenness of the characteristic impedance and the imbalance of the impedance. Reflection resonance noise tends to be superimposed on electrical signals. When the separation distance is greater than 200 μm, the flexible printed wiring board 2 with an electromagnetic wave shielding film becomes thick and has insufficient flexibility.

(Flexible Printed Wiring Board)

The flexible printed wiring board 50 is a wiring board in which a printed circuit (power circuit, ground circuit, ground layer, etc.) is formed by processing the copper foil of the copper-clad laminate into a desired pattern by a known etching method.

Examples of copper-clad laminates include laminates in which copper foil is attached to one or both sides of the base film 52 via an adhesive layer (not shown), and the base film 52 is formed by casting on the surface of the copper foil. Laminates made of resin solutions, etc.

Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenolic resin, polyurethane, acrylic resin, melamine resin and the like.

The thickness of the pressure-sensitive adhesive layer is preferably not less than 0.5 μm and not more than 30 μm.

(basement membrane)

The base film 52 is preferably a heat-resistant film, more preferably a polyimide film or a liquid crystal polymer film, and still more preferably a polyimide film.

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 a practical point of view.

The thickness of the base film 52 is preferably not less than 5 μm and not more than 200 μm, more preferably not less than 6 μm and not more than 25 μm, and still more preferably not less than 10 μm and not more than 25 μm in terms of flexibility.

(printed circuit)

Examples of the copper foil constituting 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 not less than 1 μm and not more than 50 μm, more preferably not less than 18 μm and not more than 35 μm.

Ends (terminals) in the longitudinal direction 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 a film in which an adhesive layer (not shown) is formed 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 a practical point of view.

The base film is preferably a heat-resistant film, more preferably a polyimide film or a liquid crystal polymer film, and even more preferably a polyimide film.

The thickness of the base film is preferably not less than 1 μm and not more than 100 μm, and more preferably not less than 3 μm and not more than 25 μm from the viewpoint of flexibility.

Examples of materials for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenolic resin, polyurethane, acrylic resin, melamine resin, polystyrene, polyolefin, etc. . The epoxy resin may also contain a rubber component (carboxy-modified nitrile rubber, etc.) for imparting flexibility.

The thickness of the adhesive layer is preferably not less than 1 μm and not more than 100 μm, more preferably not less than 1.5 μm and not more than 60 μm.

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, a rectangle, and the like.

(Manufacturing method of printed wiring board with electromagnetic wave shielding film)

The printed wiring board with the electromagnetic wave shielding film of this invention can be manufactured by the method which has the following process (d)-(g), for example.

Process (d): The process of providing the insulating film in which the through-hole was formed in the position corresponding to a printed circuit on the surface of the printed wiring board provided with a printed circuit, and obtaining the printed wiring board with an insulating film.

Step (e): After step (d), the printed wiring board with insulating film and the electromagnetic wave shielding film of the present invention from which the second release film has been peeled off are brought into contact with the surface of the insulating film through a conductive adhesive layer. They are overlapped in a way, and they are hot-pressed, so that the conductive adhesive layer is bonded to the surface of the insulating film and the conductive adhesive layer is electrically connected to the printed circuit through the through hole, and a printed distribution with an electromagnetic wave shielding film is obtained. The process of line board.

Step (f): a step of peeling the first release film when the first release film is unnecessary after the step (e).

Step (g): A step of completely curing the anisotropic conductive adhesive layer between the step (e) and the step (f) or after the step (f) as necessary.

Next, a method of manufacturing a flexible printed wiring board with an electromagnetic shielding film will be described with reference to FIG. 5 .

(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 superimposed on the flexible printed wiring board 50 , and the insulating film 60 is bonded to the surface of the flexible printed wiring board 50 . An agent layer (not shown in the figure) is formed, and the adhesive layer is cured to obtain a flexible printed wiring board 3 with an insulating film. The adhesive layer of the insulating film 60 may be bonded temporarily to the surface of the flexible printed wiring board 50, and the adhesive layer may be fully hardened by process (g).

Adhesion and curing of the adhesive layer are performed, for example, by hot pressing using a press (not shown) or the like.

(Process (e))

As shown in FIG. 5 , the electromagnetic wave shielding film 1 from which the second release film 40 has been peeled off is superimposed on the flexible printed wiring board 3 with an insulating film, and the anisotropic conductive adhesive layer 24 is bonded by hot pressing. On the surface of the insulating film 60, the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62, and the flexible printed wiring board 2 with an electromagnetic wave shielding film is obtained.

Part of the electromagnetic wave shielding film 1 sinks into the through hole 62 by hot pressing, and the insulating resin layer 10 , metal thin film layer 22 and anisotropic conductive adhesive layer 24 in the electromagnetic wave shielding film 1 are dented toward the through hole 62 side. Accordingly, the portion of the insulating resin layer 10 located above the through hole 62 is recessed toward the through hole 62 side, and pits are observed on the surface of the insulating resin layer 10 . When such dimples exist, the surface area of the insulating resin layer 10 increases, thereby contributing to heat dissipation of heat generated in the printed wiring board 50 .

Adhesion and curing of the anisotropic conductive adhesive layer 24 are performed, for example, by heat press using a press (not shown in the figure) or the like.

The hot pressing time is not less than 20 seconds and not more than 60 minutes, more preferably not less than 30 seconds and not more than 30 minutes. The anisotropic conductive adhesive layer 24 adheres to the surface of the insulating film 60 as the hot pressing time is more than the lower limit of the said range. The manufacturing time of the flexible printed wiring board 2 with an electromagnetic wave shielding film can be shortened as heat press time is below the upper limit of the said range.

The temperature of hot pressing (the temperature of the hot plate of the press) is preferably 140°C to 190°C, more preferably 150°C to 175°C. When the temperature of hot pressing is more than the lower limit of the said range, the anisotropic conductive adhesive layer 24 will adhere to the surface of the insulating film 60. In addition, the time for hot pressing can be shortened. The deterioration etc. of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed as the temperature of hot-pressing is below the upper limit of the said range.

The pressure of hot pressing is preferably 0.5 MPa to 20 MPa, more preferably 1 MPa to 16 MPa. The anisotropic conductive adhesive layer 24 adheres to the surface of the insulating film 60 as the pressure of hot pressing is more than the lower limit of the said range. In addition, the time for hot pressing can be shortened. The damage etc. of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed as the pressure of a hot press is below the upper limit of the said range.

(Process (f))

As shown in FIG. 5 , when the first release film is unnecessary, the first release film 30 is peeled from the insulating resin layer 10 .

(Process (g))

When the hot pressing time in the step (e) is as short as 20 seconds to 10 minutes, it is preferable to carry out the anisotropic conductive bonding between the step (e) and the step (f) or after the step (f). The complete curing of the mixture layer 24.

Complete curing of the anisotropic conductive adhesive layer 24 is performed, for example, using a heating device such as an oven.

The heating time is not less than 15 minutes and not more than 120 minutes, preferably not less than 30 minutes and not more than 60 minutes. The anisotropic conductive adhesive layer 24 can be fully hardened as heating time is more than the lower limit of the said range. The manufacturing time of the flexible printed wiring board 2 with an electromagnetic wave shielding film can be shortened as heating time is below the upper limit of the said range.

The heating temperature (atmospheric temperature in the oven) is preferably not less than 120°C and not more than 180°C, more preferably not less than 120°C and not more than 150°C. Heating time can be shortened as heating temperature is more than the lower limit of the said range. If heating temperature is below the upper limit of the said range, deterioration, etc. of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed.

It is preferable to heat without pressurization from the viewpoint that no special equipment can be used.

(Effect)

Regarding the flexible printed wiring board 2 with the electromagnetic wave shielding film described above, since the electromagnetic wave shielding film 1 is used, the conductive adhesive layer of the electromagnetic wave shielding film 1 passes through the insulating film provided on the surface of the flexible printed wiring board 50 . The through-hole 62 of 60 is reliably electrically connected to the printed circuit 54 of the flexible printed wiring board 50 .

(Other implementations)

The printed wiring board with the electromagnetic wave shielding film of the present invention only needs to include the printed wiring board, the insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the conductive layer adjacent to the insulating film through which the conductive layer passes. The through-holes formed in the insulating film may be electrically connected to the electromagnetic wave shielding film of the printed circuit, and are not limited to the embodiments illustrated in the drawings.

For example, a flexible printed wiring board may have a ground layer on the back side. In addition, the flexible printed wiring board may have a printed circuit on both surfaces, and an insulating film and an electromagnetic wave shielding film may be attached on both surfaces.

Instead of the flexible printed wiring board, a non-flexible rigid printed circuit board may be used.

The electromagnetic wave shielding film 1 etc. of 2nd Embodiment may be used instead of the electromagnetic wave shielding film 1 of 1st Embodiment.

[Example]

Examples are shown below. It should be noted that the present utility model is not limited to the examples.

(Hardness of metal thin film layer based on nanoindentation method)

The hardness of the metal thin film layer based on the nanoindentation method was carried out by the above-mentioned nanoindentation method (continuous The measurement of stiffness measurement method) is obtained by the above-mentioned calculation method according to the measurement results.

(10% compressive strength of conductive particles)

The 10% compressive strength of electroconductive particle was calculated|required by said Formula (11) from the measurement result using the microcompression tester (Shimadzu Corporation make, MCT-510).

(storage modulus)

The storage modulus was measured using a dynamic viscoelasticity measuring device (manufactured by Rheometric Scientific, Inc., RSAII) under the conditions of temperature: 180° C., frequency: 1 Hz, and heating rate: 10° C./minute.

(electrical connection)

The connection resistance between the ground wire 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 was measured by the step (f) described later, and was carried out according to the following standard. commented.

◎(Excellent): The connection resistance is less than 0.5Ω.

〇 (good): The connection resistance is 0.5Ω or more but less than 1Ω.

× (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 (Lintec Corporation ( Lintec Corporation), T157, thickness: 50 μm, storage modulus at 180° C.: 5×10 ⁸ Pa).

As a 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 curing agent (N-aminopiperazine), and 5 parts by mass of carbon black were dissolved in A paint obtained in 200 parts by mass of a solvent (methyl ethyl ketone).

As a thermosetting conductive adhesive composition, a thermosetting adhesive 24a (100 parts by mass of epoxy resin (manufactured by DIC Corporation, EXA-4816) and a curing agent (manufactured by Ajinomoto Fine-Techno Corporation, PN-23) 15 parts by mass of latent curable epoxy resin) and 40 parts by mass of conductive particles 24b (copper particles, average particle diameter: 8 μm, 10% compressive strength: 85.1 MPa) were dissolved or dispersed in a solvent ( A composition obtained in 200 parts by mass of methyl ethyl ketone).

Process (a):

The coating is applied on the surface of the release agent layer 34 of the first release film 30, heated at 60°C for 2 minutes to make it semi-cured, and the insulating resin layer 10 (thickness: 10 μm, energy storage mold at 180°C) is formed. Volume: 1.9×10 ⁷ Pa).

Process (b1):

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

Process (b2):

A thermally curable conductive adhesive composition is coated on the surface of the metal thin film layer 22 using a slot die coating head, and the solvent is volatilized into a B-stage (B-stage) to form an anisotropic conductive adhesive composition. Adhesive layer 24 (thickness: 7 μm, copper particles: 4.5 vol%, storage modulus at 180° C.: 2×10 ⁴ Pa).

Process (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 .

Process (d):

On the surface of a polyimide film (surface resistance: 1×10 ¹⁷ Ω) (substrate film) with a thickness of 12 μm, an insulating adhesive composition composed of a nitrile rubber-modified epoxy resin is applied as a dry film The thickness was 12 μm, an adhesive layer was formed, and an insulating film 60 (thickness: 25 μm) was obtained. A through-hole 62 (aperture diameter: 2 mm) is formed at a position corresponding to the ground of the printed circuit 54 .

The flexible printed wiring board 50 in which the printed circuit 54 was formed on the surface of the 12-micrometer-thick polyimide film (surface resistance: 1× ^1017Ω ) (base film 52) was prepared.

The insulating film 60 was attached to the flexible printed wiring board 50 by hot pressing, and the flexible printed wiring board 3 with an insulating film was obtained.

Process (e):

The electromagnetic wave shielding film 1 from which the second release film 40 was peeled off was superimposed on the flexible printed wiring board 3 with an insulating film, and a hot pressing plate temperature: 170° C. . Pressure: 2MPa heat press for 60 seconds, temporarily bond the anisotropic conductive adhesive layer 24 to the surface of the insulating film 60, and obtain the flexible printed wiring board 2 with the electromagnetic wave shielding film.

Process (f):

The flexible printed wiring board 2 with an electromagnetic shielding film was heated at 160° C. for 1 hour using a high temperature thermostat (manufactured by Kusumoto Kasei Co., Ltd., HT210) to completely cure the anisotropic conductive adhesive layer 24 . The first release film 30 was peeled off from the insulating resin layer 10 .

The connection resistance between the ground wire 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)

Except that the kind of metal constituting the metal thin film layer 22, the thickness of the metal thin film layer 22, the kind of the conductive particles 24b, and the average particle diameter of the conductive particles 24b were changed as shown in Table 1, it was the same as in Example 1. The electromagnetic wave shielding film 1 was thus obtained. Moreover, except having changed the electromagnetic wave shielding film 1, it carried out similarly to Example 1, and obtained the flexible printed wiring board 2 with an electromagnetic wave shielding film. The connection resistance between the ground wire 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.

[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 wire of the printed circuit 54 and the metal thin film layer 22 of the electromagnetic wave shielding film 1 is low, and the conductive adhesion The agent layer is reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film.

In Example 5 which used silver as both the metal which comprises the metal thin film layer 22, and the metal which comprises electroconductive particle 24b, connection resistance became slightly high.

Industrial availability

The electromagnetic wave shielding film of the present invention is useful as a component for electromagnetic wave shielding in flexible printed wiring boards for electronic equipment such as smart phones, mobile phones, optical modules, digital cameras, game machines, notebook computers, and medical equipment.

Explanation of reference signs

1 Electromagnetic wave shielding film

2 Flexible printed wiring board with electromagnetic shielding film

3 Flexible printed wiring board with insulating film

10 insulating resin layer

20 conductive layer

22 metal film layer

24 Anisotropic conductive adhesive layer

24a Heat-curing adhesives

24b Conductive particles

26 isotropic conductive adhesive layer

26a Thermosetting adhesives

26b Conductive particles

30 first release film

32 release film body

34 release agent layer

40 Second release film

42 release film body

44 release agent layer

50 Flexible printed wiring board

52 basement membrane

54 printed circuit

60 insulating film

62 through hole

101 Flexible printed wiring board with electromagnetic shielding film

110 Electromagnetic wave shielding film

112 insulating resin layer

114 metal film layer

116 conductive adhesive layer

118 The first release film

130 flexible printed wiring board

132 Basement membrane

134 printed circuits

140 insulating film

142 Through hole.

Claims (6)

1. An electromagnetic wave shielding film, comprising:

an insulating resin layer;

a metal thin film layer adjacent to the insulating resin layer;

a conductive adhesive layer adjacent to a side of the metal thin film layer opposite to the insulating resin layer; and

a first release film adjacent to a side of the insulating resin layer opposite to the metal thin film layer,

the thickness of the metal film layer is more than 150nm and less than 400 nm.

2. The electromagnetic wave-shielding film according to claim 1,

the thickness of the insulating resin layer is 0.1 [ mu ] m or more and 30 [ mu ] m or less.

3. The electromagnetic wave shielding film according to claim 1 or 2,

the conductive adhesive layer contains conductive particles having an average particle diameter of 2 to 26 [ mu ] m,

the thickness of the conductive adhesive layer is 3 [ mu ] m to 25 [ mu ] m.

4. The electromagnetic wave shielding film according to claim 1 or 2,

the conductive adhesive layer contains conductive particles having an average particle diameter of 0.1 to 10 [ mu ] m,

the thickness of the conductive adhesive layer is 5 [ mu ] m to 20 [ mu ] m.

5. A printed wiring board with an electromagnetic wave shielding film, comprising:

a printed wiring board having a printed circuit provided on at least one surface of a substrate;

an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided; and

the electromagnetic wave-shielding film according to claim 1 or 2, wherein the conductive adhesive layer of the electromagnetic wave-shielding film is adjacent to the insulating film, and the conductive adhesive layer is electrically connected to the printed circuit through a through hole formed in the insulating film.

6. The printed wiring board with an electromagnetic wave-shielding film according to claim 5,

the portion of the insulating resin layer located above the through hole is recessed toward the through hole.