JP2012049368A - Coverlay film and flexible printed wiring board using the same - Google Patents

Abstract

To provide a coverlay film having both excellent insulation reliability and electromagnetic shielding characteristics.
A cover lay film including a cured resin layer, a conductive layer having a first surface and a second surface, an insulating film layer, and an adhesive layer, wherein the first layer of the conductive layer is provided. The cured resin layer is laminated on the surface, and the insulating film layer is laminated on the second surface of the conductive layer,
The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, or the insulating film layer is opposite to the surface on which the conductive layer is laminated. A coverlay film that is laminated on the surface.
[Selection figure] None

Description

  The present invention relates to a cover lay film and a flexible printed wiring board using the cover lay film.

Conventionally, resin layers such as polyimide films and polyamide films having electrical insulation properties; adhesive layers mainly composed of epoxy resins or polyimide resins; metal foil layers such as conductive copper foil, silver foil, and aluminum foil; A flexible printed wiring board (hereinafter also referred to as “FPC”) such as a coverlay film or a metal-clad laminate is used in combination as appropriate.
FPC is frequently used to incorporate a circuit in a complicated mechanism in electronic devices such as mobile phones, video cameras, and notebook computers, which are rapidly becoming smaller and more functional. In these electronic devices, countermeasures against electromagnetic wave shielding are indispensable, and FPCs with countermeasures against electromagnetic wave shielding have been used in FPCs used in apparatuses.
For example, Patent Document 1 discloses a coverlay film having an insulating plastic film layer, an adhesive layer, and a protective layer, and an electrically conductive layer having an electrical resistance value of 500 Ω / □ or less on at least one surface of the insulating plastic film layer. A coverlay film is disclosed.
Patent Document 2 discloses a flexible circuit board in which a predetermined circuit is formed on a base film and a coverlay film is provided on the circuit side, and a metal layer is formed on at least one side of the flexible circuit board. A flexible circuit board is disclosed.

JP 2002-361770 A JP-A-8-153940

However, the coverlay film disclosed in Patent Document 1, for example, has an insulating plastic film layer / conductive layer / adhesive layer when the coverlay film is thermocompression bonded to the circuit surface. Since the agent layer melts, there is a possibility that the circuit and the conductive layer come into contact with each other, and there is a problem that the insulation reliability is inferior. Further, as another structure of the coverlay film disclosed in Patent Document 1, there is a conductive layer / insulating plastic film layer / adhesive layer. In this case, the conductive layer is present on the surface of the coverlay film. However, when an FPC using a coverlay film having this configuration is used (for example, inside a mobile phone), the conductive layer may be peeled off or scraped off due to contact (rubbing) with the casing or other members, resulting in electromagnetic waves. There is a problem that the shield function is lost.
The flexible circuit board disclosed in Patent Document 2 also has the same problem as described above.

  In view of the above circumstances, an object of the present invention is to provide a coverlay film having both excellent insulation reliability and electromagnetic wave shielding characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have found a cured resin layer, a conductive layer having a first surface and a second surface, an insulating film layer, and an adhesive layer. The cured resin layer is laminated on the first surface of the conductive layer, the insulating film layer is laminated on the second surface of the conductive layer, and the adhesive layer is The resin layer is laminated on the surface opposite to the surface on which the conductive layer is laminated, or the insulating film layer is laminated on the surface opposite to the surface on which the conductive layer is laminated, The present inventors have found that a coverlay film can solve the above-mentioned problems, and have completed the present invention.

That is, the present invention is as follows.
[1]
A cover lay film including a cured resin layer, a conductive layer having a first surface and a second surface, an insulating film layer, and an adhesive layer,
The cured resin layer is laminated on the first surface of the conductive layer, the insulating film layer is laminated on the second surface of the conductive layer,
The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, or the insulating film layer is opposite to the surface on which the conductive layer is laminated. A coverlay film that is laminated on the surface.
[2]
The coverlay film according to the above [1], wherein the conductive layer is a metal vapor deposition film (plating) having a three-layer structure of Ni—Cr / Cu / Ni—Cr.
[3]
The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, and the elastic modulus of the cured resin layer is 0.1 to 1.5 GPa. The coverlay film according to the above [1] or [2], wherein the elastic modulus of the layer is 2 to 4 GPa.
[4]
The coverlay film according to any one of the above [1] to [3];
A flexible printed wiring board body in which a circuit is formed on an insulating film;
The flexible printed wiring board by which the said cover-lay film was affixed on the said flexible printed wiring board main body.

  According to the present invention, a coverlay film having both excellent insulation reliability and electromagnetic wave shielding characteristics can be provided.

The schematic of FPC used for evaluation of the resistance value between circuits in an Example is shown. The schematic of FPC used for evaluation of the slide sliding characteristic in an Example is shown.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
In addition, in this embodiment and the Example mentioned later, a "mass part" shows the mass part by solid content conversion.

The coverlay film of this embodiment is
A cover lay film including a cured resin layer, a conductive layer having a first surface and a second surface, an insulating film layer, and an adhesive layer,
The cured resin layer is laminated on the first surface of the conductive layer, the insulating film layer is laminated on the second surface of the conductive layer,
The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, or the insulating film layer is opposite to the surface on which the conductive layer is laminated. It is laminated on the surface.

As a structure of the coverlay film of this embodiment, the following structures (1) or (2) are mentioned.
Configuration (1): Cured resin layer / conductive layer / insulating film layer / adhesive layer configuration (2): Insulating film layer / conductive layer / cured resin layer / adhesive layer The coverlay film of the present embodiment has the above-described configuration. As described above, since the insulating film layer or the cured resin layer is provided between the conductive layer and the adhesive layer, when the coverlay film is thermocompression bonded to the circuit surface, the adhesive layer melts and the circuit and the conductive layer Is not in contact and conducting, and has a feature of excellent insulation reliability.
Furthermore, since the coverlay film of this embodiment has a cured resin layer or an insulating film layer outside the conductive layer as described above, the conductive layer is brought into contact with the casing or other members (rubbed). Is not peeled off or scraped off, and excellent electromagnetic wave shielding characteristics can be maintained.
As described above, the cover lay film of the present embodiment can achieve both excellent insulation reliability and electromagnetic wave shielding characteristics over a long period of time by having the configuration (1) or (2).
In addition, the cover-lay film of this embodiment may contain layers other than the above, such as a protective film layer, in an arbitrary place as needed, as long as the above-described configuration is included.

[Hardened resin layer]
The resin constituting the cured resin layer in the present embodiment is not particularly limited, and examples thereof include a thermosetting resin and a thermosetting resin in which a thermosetting resin and a thermoplastic resin are mixed. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, xylene resin, furan resin, and cyanate ester resin. Examples of the thermoplastic resin include polyamide resin, polyester resin, polyacrylic resin, phenoxy resin, and polyurethane resin. Among these, from the viewpoint of heat resistance and flexibility, an epoxy resin is preferable, and a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a novolac type epoxy resin are more preferable.

  Further, from the viewpoint of further improving adhesiveness and flexibility, it is preferable to add a rubber-based resin such as acrylic rubber to the cured resin layer. In this case, the compounding amount of the rubber-based resin is preferably 10 to 100 parts by mass, more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the resin constituting the cured resin layer.

In addition to the resin, the cured resin layer may contain a curing agent, a curing accelerator, other additives, and the like.
It does not specifically limit as a hardening | curing agent and a hardening accelerator, Various well-known things can be selected suitably and can be used. Specific examples of the curing agent include diaminodiphenyl sulfone, dicyandiamide, and acid anhydrides. The molar ratio of the curing agent functional group to the reactive functional group of the resin constituting the cured resin layer is preferably 0.1 to 1.5, and more preferably 0.3 to 1. 2, More preferably, it is 0.5-1.0. Specifically as a hardening accelerator, a boron trifluoride monoethylamine, an imidazole compound, etc. are mentioned, for example. The blending amount of the curing accelerator is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 2 parts by mass, and still more preferably 0.1 to 100 parts by mass of the resin constituting the cured resin layer. 1 part by mass.
As other additives, various known additives such as inorganic fillers such as aluminum hydroxide, magnesium hydroxide, silica and alumina, surfactants, dispersants, phosphorus flame retardants and the like can be used. The compounding quantity of an additive can be suitably adjusted according to the objective.

  Although it does not specifically limit as thickness of a cured resin layer, Preferably it is 1-30 micrometers, More preferably, it is 5-10 micrometers. When the thickness of the cured resin layer is 1 μm or more, the insulation reliability tends to be good, and when it is 30 μm or less, the flexibility tends to be good.

[Conductive layer]
The conductive layer in this embodiment is a layer containing a conductive material. Conductive materials include metals (gold, silver, copper, aluminum, nickel, etc.); conductive resins (conductive paste, etc.) in which conductive particles (metal particles, etc.) and conductive fibers (metal fibers, etc.) are mixed with resin Etc.
Examples of the form of the conductive layer include a metal vapor-deposited film (plating), a metal foil, a film or a coating film made of a conductive resin, and the metal vapor-deposited film is from the viewpoint of flexibility, thinning, durability, and conductivity. preferable.

  The metal vapor deposition film is particularly preferably a metal vapor deposition film having a three-layer structure of Ni—Cr / Cu / Ni—Cr. By providing the Ni—Cr layer, the adhesion of the metal vapor deposition film can be improved, and chemical resistance can be imparted to the conductive layer. This metal vapor deposition film can be formed, for example, by physical vapor deposition such as EB vapor deposition, ion beam vapor deposition, or sputtering, or vacuum vapor deposition. Further explanation regarding the forming method will be described later.

  The thickness of the Ni—Cr layer constituting the metal vapor deposition film as the conductive layer is preferably from 10 to 500 mm from the viewpoint of obtaining the above effect, and from the viewpoint of further prominent effects, from 30 to 100 mm. The following is more preferable. The mixing ratio of Ni and Cr is not particularly limited. However, for example, if the ratio of Ni: Cr is 97: 3 to 50:50, the above effect can be sufficiently obtained. The thickness of the Cu layer is preferably from 500 to 3000 mm from the viewpoint of obtaining a conductive layer having good physical properties. By setting the thicknesses of the Ni—Cr layer and the Cu layer in the above ranges, the electromagnetic wave shielding characteristics are good and the folding resistance is also good.

[Insulating film layer]
Examples of the resin constituting the insulating film layer in the present embodiment include polyimide resin, polyamide resin, polyamideimide resin, polyaramid resin, polyphenylene sulfide resin, polyetherimide resin, polyethylene naphthalate resin, and polyethylene terephthalate resin. Among these, polyimide resins are preferable from the viewpoints of insulation and heat resistance.

  As a method of manufacturing an insulating film made of a polyimide resin, tetracarboxylic dianhydride and diamine are reacted in a polar organic solvent to create a polyamic acid, which is cast on a support, imidized and dried. The method to obtain is mentioned. In that case, it may peel from a support body suitably and may be extended and heat-treated.

  Specific examples of the diamine component include, for example, paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 1,4-bis (3-methyl- 5-aminophenyl) benzene and their amide-forming derivatives.

  Specific examples of the tetracarboxylic dianhydride component include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5 , 6-tetracarboxylic acid and acid anhydrides such as amide-forming derivatives thereof.

  In addition to the resin, other various known additives may be blended in the insulating film layer. Examples of other additives include titanium oxide, silicon dioxide, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, and alumina. The compounding amount of other additives is preferably 0.01 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, and still more preferably 0.05 to 100 parts by mass of the resin constituting the insulating film layer. -1 part by mass.

  The thickness of the insulating film layer is preferably 4 to 50 μm, more preferably 7 to 25 μm. When the thickness of the insulating film layer is 4 μm or more, the insulation reliability tends to be good, and when it is 50 μm or less, the flexibility tends to be good.

[Adhesive layer]
As resin which comprises the adhesive bond layer in this embodiment, it is not specifically limited, Resin similar to resin which comprises the cured resin layer mentioned above is mentioned. As resin which comprises an adhesive bond layer, an epoxy resin is preferable from a heat resistant and flexible viewpoint.

  In addition to the resin, the adhesive layer may contain a curing agent, a curing accelerator, other additives, and the like. About the kind of hardening | curing agent, hardening accelerator, and another additive, the thing similar to what is contained in the cured resin layer mentioned above is mentioned.

  The thickness of the adhesive layer is preferably 10 to 30 μm, more preferably 10 to 20 μm. When the thickness of the adhesive layer is 10 μm or more, the adhesiveness to the flexible printed wiring board body and the circuit embedding tend to be good, and when it is 30 μm or less, the flexibility tends to be good. .

[Protective film layer]
As a protective film layer in this embodiment, the mold release film layer etc. which were provided in the surface on the opposite side to the surface where the cured resin layer of the adhesive bond layer or the insulating film layer were laminated | stacked, etc. are mentioned, for example. Examples of the resin constituting the protective film layer include polyethylene terephthalate (PET) resin, polypropylene (PP) resin, polyethylene (PE) resin, and the like.

Furthermore, the cover-lay film of this embodiment can improve a slide sliding characteristic and folding resistance by adjusting the elasticity modulus of a cured resin layer and an adhesive bond layer to a specific range.
When the coverlay film has the configuration (1): cured resin layer / conductive layer / insulating film layer / adhesive layer, the elastic modulus of the cured resin layer is preferably 0 from the viewpoint of improving the folding resistance. 0.05 to 2 GPa, more preferably 0.1 to 1.5 GPa. From the viewpoint of improving the sliding property, the elastic modulus of the adhesive layer is preferably 1 to 5 GPa, more preferably 2 to 4 GPa. .
When the coverlay film has the configuration (2): insulating film layer / conductive layer / cured resin layer / adhesive layer, the elastic modulus of the adhesive layer is preferably from the viewpoint of improving the sliding property. 1-5 GPa, more preferably 2-4 GPa.
In addition, the elasticity modulus of the said cured resin layer and an adhesive bond layer shows the elasticity modulus of the state (C stage) after fully curing each layer.

  Further, when the coverlay film has the configuration (1): cured resin layer / conductive layer / insulating film layer / adhesive layer, the elongation rate of the cured resin layer is preferably from the viewpoint of improving the folding resistance. Is 10 to 100%, more preferably 40 to 70%. The elongation can be measured and calculated by the same method as the method for measuring the tensile elastic modulus described later.

  As a method of adjusting the elastic modulus and elongation rate of the cured resin layer and the adhesive layer to the above ranges, the amount of the curing agent, the amount of rubber and inorganic filler, and the curing conditions are appropriately set, and the cured state of each layer is adjusted. And the like.

[Method for producing coverlay film]
It does not specifically limit as a manufacturing method of the coverlay film in this embodiment, For example, it can manufacture by the method which has the process of the following (a)-(c).
(A) A step of performing metal plating on one surface of the insulating film layer to obtain an insulating film with a conductive layer;
(B) A step of obtaining a cured resin layer and an insulating film with a conductive layer by applying varnish A for forming a cured resin layer on the conductive layer surface side of the insulating film with a conductive layer, and heating and curing.
(C) The process of apply | coating and drying the varnish B which forms an adhesive bond layer on the surface on the opposite side to the surface where the cured resin layer of the insulating film obtained at the said (b) process was laminated | stacked.
Hereinafter, each step will be described.

[Step (a)]
(A) A process is a process of giving the metal plating process to the single side | surface of an insulating film layer, and obtaining the insulating film with a conductive layer.
The metal plating treatment can be performed by physical vapor deposition such as EB vapor deposition, ion beam vapor deposition, or sputtering, or by vacuum vapor deposition, and among these, sputtering is preferable.

In the coverlay film of this embodiment, the metal vapor deposition film having a three-layer configuration of Ni—Cr / Cu / Ni—Cr, which is a preferred aspect of the conductive layer, is laminated as follows, for example.
First, a Ni—Cr layer is laminated on the surface of the insulating film layer. This is laminated by a sputtering method using a Ni—Cr alloy having a Ni: Cr mixing ratio of, for example, 93: 7 as a target so that the thickness is 10 to 500 mm. Next, the Cu layer is laminated on the surface of the Ni—Cr layer laminated on the surface of the insulating film layer by a sputtering method using Cu as a target so that the thickness becomes 500 mm or more and 3000 mm or less. Next, a Ni—Cr layer is laminated on the surface of the Cu layer in the same manner as described above.
In this way, a conductive layer having a three-layer structure of Ni—Cr / Cu / Ni—Cr is laminated on the surface of the insulating film layer. Prior to laminating the Ni—Cr layer on the surface of the insulating film layer, the surface of the insulating film layer is subjected to a pretreatment such as plasma treatment for the purpose of obtaining a better interlayer adhesion. It doesn't matter.

[Step (b)]
(B) A process is a process of obtaining the cured resin layer and the insulating film with a conductive layer by apply | coating the varnish A which forms a cured resin layer on the conductive layer surface side of the said insulating film with a conductive layer, and making it heat-harden.
(B) Varnish A in a process contains resin, a hardening | curing agent, etc. which are contained in a cured resin layer, and a solvent. Examples of the solvent used for varnish A include toluene, methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether, dimethylacetamide, and the like.

  As a method of applying varnish A, a comma coater, a die coater, a gravure coater, or the like can be appropriately employed depending on the application thickness.

  The method of heat-curing the varnish A applied to the insulating film with a conductive layer is not particularly limited, but it is cured / cured until it becomes a semi-cured state (hereinafter also referred to as “B stage”) under certain curing / drying conditions. After drying, it is preferable to dry at a higher temperature and cure almost completely. For example, when the resin contained in varnish A is a bisphenol A type epoxy resin and the curing agent is diaminodiphenyl sulfone, it can be completely cured by drying at 150 ° C. for 5 minutes and then heat curing at 160 ° C. for 1 hour. .

[(C) Step]
Step (c) is a step of applying and drying varnish B for forming an adhesive layer on the surface opposite to the surface on which the cured resin layer of the insulating film obtained in step (b) is laminated. is there.
The varnish B in the step (c) includes a resin, a curing agent and the like contained in the adhesive layer and a solvent. Examples of the solvent used for the varnish B include the same solvents as the varnish A described above. Moreover, as a method of apply | coating varnish B, the method similar to the above can be used.

Although it does not specifically limit as a method of drying the varnish B apply | coated to the curable resin and the insulating film with a conductive layer, It is preferable to make it harden and dry to a B stage on fixed hardening and drying conditions. For example, when the resin contained in varnish A is a bisphenol A type epoxy resin and the curing agent is diaminodiphenyl sulfone, it can be made a B stage by drying at 150 ° C. for 5 minutes.
The curing conditions in the above-described steps (b) and (c) can be appropriately adjusted depending on the amount of the main resin, the amount of the curing agent, and the like.

When the coverlay film of this embodiment has a protective film layer, a protective film layer can be further provided by the following (d) process, for example.
(D) The resin film constituting the protective film layer is bonded to the surface opposite to the surface on which the cured resin layer or the insulating film layer of the adhesive layer provided in the step (c) is laminated. Process.
Here, as a method of laminating the resin film, a method using a press, a laminating method using a hot roll, or the like can be used. The bonding conditions can be performed, for example, at a temperature of 40 to 120 ° C. and a pressure of 0.1 to 3 MPa.

[Flexible printed wiring board]
The flexible printed wiring board of the present embodiment includes the cover lay film of the present embodiment and a flexible printed wiring board main body having a circuit formed on an insulating film, and the cover lay film is the flexible printed wiring board main body. It is affixed to.
Here, the flexible printed wiring board body is obtained by forming a metal foil of a metal-clad laminate into a pattern having a desired shape by an existing etching method.
The flexible printed wiring board of this embodiment can be produced, for example, by laminating a coverlay film on a circuit forming surface exposed on a metal foil and heating and pressing under predetermined conditions.

  The metal-clad laminate is obtained by laminating an insulating resin layer made of polyimide resin or the like on a metal foil. The metal-clad laminate may be a three-layer flexible metal laminate composed of a metal foil, a resin layer, and an adhesive layer, or a two-layer flexible metal laminate composed of a metal foil and a resin layer.

  Examples of the resin constituting the resin layer include a polyimide resin, a polyamide resin, and a polyamideimide resin.

  Examples of the metal foil include copper foil, SUS foil, aluminum foil, and the like, and copper foil is preferable from the viewpoint of conductivity and circuit workability. Moreover, when using metal foil, you may perform the inorganic surface treatment by zinc plating, chromium plating, etc., and the organic surface treatment by a silane coupling agent etc.

  As resin which comprises an adhesive bond layer, 1 or more types of resin selected from an epoxy resin, a phenoxy resin, an acrylic resin, and a urethane resin can be included, for example. Moreover, additives, such as a hardening | curing agent, can be added to an adhesive bond layer according to the kind of said resin in order to adjust the hardening degree.

  The flexible printed wiring board of this embodiment is suitably applied as a movable part flexible printed wiring board inside a mobile phone, for example.

  In addition, unless otherwise specified, the measurement and evaluation of each physical property in this specification can be performed according to the methods described in the following examples.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited only to these Examples.
In Examples and Comparative Examples, each physical property was measured and evaluated by the following methods.

(Thickness of each layer)
The thickness of each layer other than the conductive layer was measured with a film thickness meter (LITEMATIC VL-50 manufactured by Mitutoyo Corporation).
The thickness of the conductive layer was measured by fluorescent X-rays (Rigaku Corporation RIX-2000).

(Evaluation method for inter-circuit resistance)
A circuit of line / space = 100 μm / 100 μm is formed on a single-sided copper-clad plate “PNS H0512RAH (manufactured by Arisawa Manufacturing Co., Ltd.)” composed of a polyimide layer of 12.5 μm and a rolled copper foil of 12 μm. The adhesive layer surfaces from which the protective film of the film was peeled were combined and pressed at 160 ° C. and 3 Mpa for 1 hour to obtain an FPC with an electromagnetic wave shield coverlay film as shown in FIG.
The insulation resistance value between these circuits was measured with an insulation resistance measuring instrument (R8340A manufactured by Advantest). Usually, if there is a resistance value of 1E + 10Ω or more, it is determined that the insulation is maintained.

(Evaluation of peeling of conductive layer after repeated bending)
A circuit of 10 reciprocations in series of line / space = 75 μm / 75 μm is formed on a single-sided copper-clad plate “PNS H0512RAH (manufactured by Arisawa Manufacturing Co., Ltd.)” composed of a polyimide layer of 12.5 μm and a rolled copper foil of 12 μm. The surface of the adhesive layer from which the protective film of the electromagnetic wave shield coverlay film was peeled off was combined and pressed at 160 ° C. and 3 MPa for 1 hour to obtain an FPC with an electromagnetic wave shield coverlay film as shown in FIG.
The obtained FPC was repeatedly bent with a slide bending tester (manufactured by Arisawa Manufacturing Co., Ltd.) under the conditions that the bending radius was 0.65 mmR, the speed was 60 rpm, the stroke was 50 mm, and the coverlay film was on the outside. The presence or absence of peeling or shaving of the conductive layer was visually confirmed.

(Evaluation of adhesive strength at insulating film layer / conductive layer interface)
An 18 μm copper plating layer is formed by electroless copper plating on the conductive layer surface side of the insulating film with the conductive layer before forming the cured resin layer, and the formed copper plating layer is subjected to a tensile tester (Shimadzu Corporation Autograph). Was peeled off in the 90 ° direction, and the peel strength was measured.

(Evaluation of adhesive strength at the conductive layer / cured resin layer interface)
The cured resin layer was reinforced by sticking a SUS plate with adhesive tape, and the insulating film with a conductive layer was peeled off in a 90 ° direction with a tensile tester (manufactured by Shimadzu Corporation), and the peel strength was measured. .

(Evaluation of chemical resistance)
The appearance after immersion in 2N HCl at room temperature for 5 minutes was visually observed. Those without peeling or soaking were accepted, and those with peeling or soaking were judged as unacceptable.

(Measurement method of elastic modulus, elongation rate of cured resin layer and elastic modulus of adhesive layer)
Varnish A or varnish B was applied to a release surface of a release PET having a thickness of 30 μm so that the thickness after drying was 20 μm, dried at 150 ° C. for 5 minutes, and then heat-cured at 160 ° C. for 1 hour. Thereafter, the release film was peeled off to obtain a cured resin film of a single resin.
The obtained resin film was cut into a size of 10 mm × 140 mm.
Set the cut resin film so that the distance between the grip part of the tensile tester (manufactured by Shimadzu Corporation) is 100 mm, and the resin film breaks at a speed of 50 mm / min. Pulled up.
The tensile modulus and elongation were calculated from the obtained chart.

(Evaluation of slide sliding characteristics)
A circuit of 10 reciprocations in series of line / space = 75 μm / 75 μm is formed on a single-sided copper-clad plate “PNS H0512RAH (manufactured by Arisawa Manufacturing Co., Ltd.)” composed of a polyimide layer of 12.5 μm and a rolled copper foil of 12 μm. The surface of the adhesive layer from which the protective film of the electromagnetic wave shield coverlay film was peeled off was combined and pressed at 160 ° C. and 3 MPa for 1 hour to obtain an FPC with an electromagnetic wave shield coverlay film as shown in FIG.
The obtained FPC was repeatedly bent by a slide bending tester (manufactured by Arisawa Manufacturing Co., Ltd.) with a bending radius of 0.65 mmR, a speed of 60 rpm, a stroke of 50 mm, and the coverlay film facing outward, and the resistance value between the terminals. The number of bendings until the resistance value increased by 20% before bending was measured.
Usually, when the number of slide bends is 200,000 times or more, it can be determined that the slide sliding characteristics are good.

(Evaluation of folding resistance)
The FPC produced by the slide sliding characteristic evaluation was bent 180 ° with the coverlay film facing outward, and a load of 200 gf / cm was applied. After returning to the flat once, the bent portion was further bent 180 ° with the coverlay film inside, and a load of 200 gf / cm was applied. After repeating this five times, it was confirmed with a magnifying glass whether the cured resin layer had any abnormalities such as cracks and cracks.

(Preparation of varnish A)
Bisphenol A type epoxy resin “JER1001 (Mitsubishi Chemical Corporation)” 100 parts by mass, 4,4′-diaminodiphenylsulfone 8 parts by mass, boron trifluoride monoethylamine 0.5 parts by mass, acrylic rubber “Baymac G (Mitsui DuPont) 80 parts by mass of Polychemical Co.) was dissolved in 180 parts by mass of toluene and 100 parts by mass of methyl ethyl ketone to obtain varnish A.

(Preparation of varnish B)
Tris-hydroxyphenylmethane type epoxy resin “JER1032 (Mitsubishi Chemical)” 30 parts by mass, bisphenol A type epoxy resin “JER828 (Mitsubishi Chemical)” 70 parts by mass, 4,4′-diaminodiphenylsulfone 20 parts by mass Varnish B was obtained by dissolving 0.5 parts by mass of boron trifluoride monoethylamine and 30 parts by mass of phenoxy resin “YX8100 (manufactured by Mitsubishi Chemical)” in 70 parts by mass of cyclohexanone and 80 parts by mass of methyl ethyl ketone.

(Preparation of insulating film with conductive layer)
A Ni—Cr layer (thickness 50 mm), a Cu layer (thickness 1000 mm), and a Ni—Cr layer (thickness 50 mm) are sequentially laminated on the surface of the polyimide film “Kapton 50EN (manufactured by Toray DuPont)” using a sputtering method. Thus, an insulating film with a conductive layer in which a conductive layer having a thickness of 110 nm was laminated was obtained.

Example 1
Varnish A was applied to the conductive layer surface of the insulating film with the conductive layer obtained above so that the thickness after drying was 5 μm, dried at 150 ° C. for 5 minutes, and then heat-cured at 160 ° C. for 1 hour to cure. An insulating film with a resin layer (A) and a conductive layer was obtained.
Furthermore, varnish B was applied to the opposite surface (polyimide film surface) of the cured resin layer so that the thickness after drying was 10 μm, and dried at 150 ° C. for 5 minutes to form an adhesive layer (B).
The release layer of the release PET film was opposed to the adhesive layer (B) as a protective film layer, and was bonded by roll lamination to obtain an electromagnetic wave shield coverlay film.

(Example 2)
Example 1 except that the adhesive layer (B) was formed by the same method as in Example 1 on the cured resin layer surface side of the cured resin layer (A) obtained in Example 1 and the insulating film with conductive layer. An electromagnetic wave shield cover lay film was obtained by the same method.

(Comparative Example 1)
An electromagnetic wave shield coverlay film was obtained by forming an adhesive layer (B) by the same method as in Example 1 on the insulating film surface of the insulating film with a conductive layer obtained above.

(Comparative Example 2)
An electromagnetic wave shield coverlay film was obtained by forming an adhesive layer (B) on the conductive layer surface of the insulating film with a conductive layer obtained above by the same method as in Example 1.
Table 1 shows the cross-sectional configurations and evaluation results of the coverlay films of Examples 1 and 2 and Comparative Examples 1 and 2.

  From the results of Table 1, it can be seen that the cover lay film of the present embodiment has both insulation reliability and electromagnetic shielding characteristics.

(Examples 3 to 5)
An electromagnetic wave shield coverlay film was obtained by the same method as in Examples 1 and 2 except that varnish A or varnish B was used for the cured resin layer and adhesive layer as in the configuration described in Table 2. .
In addition, (A) and (B) in a table | surface show that each layer was produced using varnish A and B, respectively.

From the results in Table 2, the cover lay film of the present embodiment further improves the sliding property and folding resistance by adjusting the elastic modulus of the cured resin layer and the adhesive layer to a specific range. Is possible.

Furthermore, the effectiveness of the Ni—Cr layer will be described using the following reference example.
(Reference Example 1)
A Ni—Cr layer (thickness 50 mm), a Cu layer (thickness 1000 mm), and a Ni—Cr layer (thickness 50 mm) are sequentially laminated on the surface of the polyimide film “Kapton 50EN (manufactured by Toray DuPont)” using a sputtering method. As a result, an insulating film in which a conductive layer having a thickness of 110 nm was laminated was obtained. Further, varnish A is applied to the surface so that the thickness after drying becomes 5 μm, dried at 150 ° C. for 5 minutes, and then heat-cured at 160 ° C. for 1 hour to obtain a cured resin layer and an insulating film with a conductive layer. Obtained.
Varnish A was prepared as follows.
Bisphenol A type epoxy resin “JER1001 (Mitsubishi Chemical Corporation)” 100 parts by mass, 4,4′-diaminodiphenylsulfone 8 parts by mass, boron trifluoride monoethylamine 0.5 parts by mass, acrylic rubber “Baymac G (Mitsui DuPont) 80 parts by mass of Polychemical Co.) was dissolved in 180 parts by mass of toluene and 100 parts by mass of methyl ethyl ketone to obtain varnish A.

(Reference Example 2)
An insulating film in which a Cu layer (thickness: 1000 mm) was laminated on one side of a polyimide film “Kapton 50EN (manufactured by Toray DuPont)” by a sputtering method was obtained.
A cured resin layer was formed on the conductive layer surface of the insulating film with a conductive layer obtained above by the same method as in Reference Example 1 to obtain a cured resin layer and an insulating film with a conductive layer.
Table 3 shows the cross-sectional configuration and evaluation results of the insulating films of Reference Examples 1 and 2.

As can be seen from the results in Table 3, the reference example 1 in which the conductive layer has a three-layer structure of Ni—Cr / Cu / Ni—Cr is compared to the reference example 2 having a conductive layer made of only the Cu layer. It turns out that it is excellent in adhesiveness and chemical resistance. Since the difference between the two is only the presence or absence of the Ni—Cr layer, it can be seen that the interlayer adhesion and chemical resistance can be improved by providing the Ni—Cr layer.

  The coverlay film of this embodiment has industrial applicability to the use of a flexible printed wiring board.

Claims (4)

A cover lay film including a cured resin layer, a conductive layer having a first surface and a second surface, an insulating film layer, and an adhesive layer,
The cured resin layer is laminated on the first surface of the conductive layer, the insulating film layer is laminated on the second surface of the conductive layer,
The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, or the insulating film layer is opposite to the surface on which the conductive layer is laminated. A coverlay film that is laminated on the surface.   The coverlay film according to claim 1, wherein the conductive layer is a metal vapor deposition film (plating) having a three-layer structure of Ni—Cr / Cu / Ni—Cr.   The adhesive layer is laminated on a surface of the cured resin layer opposite to the surface on which the conductive layer is laminated, and the elastic modulus of the cured resin layer is 0.1 to 1.5 GPa. The coverlay film according to claim 1 or 2, wherein the elastic modulus of the layer is 2 to 4 GPa. The coverlay film according to any one of claims 1 to 3,
A flexible printed wiring board body in which a circuit is formed on an insulating film;
The flexible printed wiring board by which the said cover-lay film was affixed on the said flexible printed wiring board main body.