WO2007119513A1

WO2007119513A1 - Shield film and shield printed wiring board

Info

Publication number: WO2007119513A1
Application number: PCT/JP2007/056182
Authority: WO
Inventors: Kenji Kamino; Yoshinori Kawakami; Syohei Morimoto; Kazuhiro Hashimoto
Original assignee: Tatsuta System Electronics Co., Ltd.
Priority date: 2006-03-29
Filing date: 2007-03-26
Publication date: 2007-10-25
Also published as: TW200803664A

Abstract

In a shield film (1), a metal layer (3) and an adhesive layer (4) are successively arranged on one surface of an insulating layer (2). In the adhesive layer (4), a thermosetting resin, preferably, a flame retardant thermosetting resin, is used as a main component, and a conductive filler is added to the main component. In the adhesive layer (4), a flame retardant of 10-180 pts.wt. is preferably mixed to a flame retardant resin of 100 pts.wt. Thus, the flame retardant shield film is provided to be used even in the environment where the film is heated in a subsequent step, as in a case of performing reflow process.

Description

Specification

Shield film and shield printed wiring board

Technical field

[0001] The present invention relates to a shield film that can be used for a printed wiring board used in a computer, a cellular phone, a communication device, a video camera, or the like, and the shield film. The present invention relates to a shielded printed wiring board.

Background art

Conventionally, shield films using metal thin films have been publicly known. For example, there is one disclosed in Patent Document 1 below. Specifically, a metal layer is formed on one surface of an electrically insulating substrate, and a conductive filler and a hard filler are added to the resin composition mainly composed of a thermoplastic resin having heat sealability on the metal layer. A flat cable shield material is disclosed in which an adhesive layer having conductivity and flame retardancy is formed using a resin composition containing a flammable filler.

[0003] However, although the shielding material of Patent Document 1 is suitable as a necessary flame-retardant shielding film for a flat cable, it is used for reflow mounting at high temperatures because it uses thermoplastic resin. Since it is not heat resistant, it cannot be used as a flame retardant shield film for printed wiring boards.

[0004] Therefore, the present inventors have added a flame retardant to the thermosetting resin of a shield film (for example, described in Patent Document 2 below) using a thermosetting resin so as to have heat resistance. And a shield film having both heat resistance and flame resistance was verified.

Patent Document 1: Japanese Patent Application Laid-Open No. 2002-279831

Patent Document 2: JP 2004-95566 A

Disclosure of the invention

Problems to be solved by the invention

[0006] However, as a result of the above verification, although the flame retardancy can be improved by increasing the amount of the flame retardant added to the thermosetting resin, the adhesion of the shield film to the printed circuit, etc. It was surprising that problems would occur when the price dropped. [0007] Therefore, an object of the present invention is to provide flame retardancy that can be used even in an environment where heating is performed in a later process, such as when performing reflow mounting without reducing adhesion to a printed circuit or the like. A shield film and a shield printed wiring board using the shield film.

Means and effects for solving the problems

The shield film of the present invention has an insulating layer and a shield layer containing a flame retardant resin.

With the above configuration, the shield film of the present invention has a shield layer containing a flame retardant resin, and has a flame retardant resin (in particular, a highly heat resistant flame retardant thermosetting resin). ) Can provide a flame-retardant shield film that can be used without problems even if it is reflow-mounted in a later process without lowering the adhesion to printed circuits.

In the shield film of the present invention, it is preferable that the shield layer has at least one isotropic conductive adhesive layer formed on at least one side of the insulating layer. According to the above configuration, when the shield film of the present invention is bonded to a printed circuit, the isotropic conductive adhesive layer can exhibit an electromagnetic wave shielding property due to the conduction of the pattern force of the ground circuit.

[0010] The shield layer of the shield film of the present invention preferably has one or more metal layers formed on at least one surface of the insulating layer and one or more anisotropic conductive adhesive layers. . According to the above configuration, when the shield film of the present invention is bonded to the printed circuit, the anisotropic conductive adhesive layer conductively connects the ground circuit pattern and the metal layer of the shield film of the present invention. Shielding performance can be demonstrated.

[0011] In the shield film of the present invention, the conductive adhesive layer further contains a flame retardant, and the flame retardant is 10 to 180 weights per 100 parts by weight of the flame retardant resin. It is preferable that it is partially blended. With the above configuration, even a very thin film of 35 / zm or less passes the UL94 vertical flammability test (VTM standard), and has high adhesion to substrates, etc., and is flexible. In addition, a shield film excellent in storage stability can be provided with certainty.

[0012] In the shield film of the present invention, the flame retardant resin is a phosphorus-containing flame retardant resin. It is preferable to contain. With the above configuration, a highly flame-retardant shield film can be provided reliably.

[0013] The shielded printed wiring board of the present invention has the above-described one-strength shield film on at least one surface of a substrate including one or more printed circuits. With the above configuration, the printed circuit board having excellent electromagnetic wave shielding properties can be provided because the pattern of the Darnd circuit and the metal layer in the shield film of the present invention are conductively connected. We can also provide shielded printed wiring boards that pass the UL94 vertical flammability test (V standard).

[0014] In the shielded printed wiring board of the present invention, the base is preferably a flexible printed wiring board. The above configuration provides a shielded printed wiring board that is excellent in electromagnetic wave shielding properties and can be used for parts that need to be bent because the substrate is a flexible printed wiring board having flexibility. it can.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a shield film according to an embodiment of the present invention.

A shield film 1 shown in FIG. 1 is obtained by sequentially providing a metal layer 3 and an adhesive layer 4 on one surface of an insulating layer 2.

[0017] The insulating layer 2 also has a coating layer force of a cover film or an insulating resin.

The cover film also has an engineering plastic power. For example, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, aramid, polyimide, polyimide amide, polyether imide, polyphenylene sulfide (PPS), polyethylene naphthalate (PEN) and the like can be mentioned.

When heat resistance is not required, a low-cost polyester film is preferred, and when flame retardancy is required, a polysulfide sulfide film, and when heat resistance is required, aramid film or polyimide film Is preferred.

The insulating resin is not particularly limited as long as it has insulating properties, and examples thereof include thermosetting resins and ultraviolet ray curable resins. Examples of the thermosetting resin include phenol resin, acrylic resin, epoxy resin, melamine resin, silicone resin, and acrylic modified silicone resin. Examples of the ultraviolet curable resin include epoxy acrylate resin, polyester, and the like. Examples include reester acrylate, and their metatarylate-modified products. As the curing form, any curing such as thermal curing, ultraviolet curing, electron beam curing, etc. may be used.

The insulating layer 2 has a thickness of 1 m to: LO / z m, preferably 3 μm to 7 μm.

[0018] Examples of the metal material forming the metal layer 3 include copper, aluminum, silver, and gold. What is necessary is just to select a metal material suitably according to the required shield characteristic. The metal layer 3 can be formed by vacuum deposition, sputtering, CVD, MO (metal organic), metal plating, etc., but considering the mass productivity, vacuum deposition is desirable and cheap and stable. Can be obtained. The metal layer 3 is not limited to a metal thin film, and a metal foil may be used. In general, the thickness of the metal layer 3 is preferably 0.01 to 10 m. If the distance is below 0.01 m, the shielding effect will be insufficient, and if it exceeds 10 m, the flexibility will deteriorate. Especially when flexibility is required, 2 m or less is preferable. Particularly when shielding effect is required, 10 m or less is preferable.

As the adhesive layer 4, a heat-resistant thermosetting resin capable of withstanding 260 ° C. substrate mounting (reflow), preferably a flame-retardant thermosetting resin, is used. A conductive filler is added, and it has isotropic conductivity or anisotropic conductivity. The thickness of the adhesive layer 4 is preferably 5 μm force or 30 μm. If it is thinner than 5 μm, sufficient adhesion cannot be obtained, and if it exceeds 30 μm, flexibility is impaired. When the adhesive layer 4 is isotropically conductive, the metal layer 3 may be omitted.

[0020] Examples of the flame retardant thermosetting resin include phosphorus-containing thermosetting resin, bisphenol A type, bisphenol F type, and novolak type.

Here, examples of the phosphorus-containing thermosetting resin include an epoxy resin, a thermoplastic resin, and a phosphorus compound.

As the epoxy resin, bisphenol A, bisphenol F, or bisphenol S can be used as a starting material and reacted with epichlorohydrin. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol, 0-cresol or naphthalenediol As a starting material, a product condensed with formaldehyde can be obtained by reacting with epichlorohydrin. You can use it alone or in combination of two or more.

The thermoplastic resin used here includes polyamide resin, phenoxy resin, polyester resin, polycarbonate resin, polyethylene resin oxide resin, polyurethane resin, polyacetal resin, polyethylene resin. Examples thereof include fat, polypropylene-based resin, and polyvinyl-based resin. These may be used alone or in combination of two or more.

It is possible to obtain a flexible thermosetting resin by blending an epoxy resin with a thermoplastic resin.

In addition, the phosphorus compound here may be a reactive type that reacts directly with epoxy resin, or a non-reactive type that does not react directly. The reaction type that directly reacts with epoxy resin is not particularly limited, and examples thereof include those having a functional group such as a hydroxyl group, an amino group, a carboxyl group, a methylol group, an epoxy group, an isocyanate group, a silanol group, and a vinyl group. Good heat resistance and adhesion.

The compounding ratio of the phosphorus-containing thermosetting resin is (A) 5 to 60 parts by weight of epoxy resin, (B) 100 parts by weight of thermoplastic resin, and (C) the total weight of (A) and (B). 10 to 35% by mass. This makes it possible to provide a flexible shield film that can withstand board mounting (reflow).

[0021] As flame retardants, environmentally problematic non-halogen flame retardants are preferred, such as melamine cyanurate, melamine polyphosphate and other nitrogen-based flame retardants, and metal water such as magnesium hydroxide and aluminum hydroxide. Examples include Japanese, or phosphoric acid flame retardants such as phosphoric acid esters and red phosphorus. When heat resistance is required, melamine cyanurate and magnesium hydroxide are preferred. The blending ratio of the flame retardant is preferably 10 to 180 parts by weight, more preferably 50 to 150 parts by weight with respect to 100 parts by weight of the flame retardant resin. If it exceeds 180 parts by weight, sufficient adhesion cannot be obtained, and if it is less than 10 parts by weight, the flame-retardant performance becomes insufficient.

[0022] As the conductive filler, a silver coated copper filler obtained by applying silver plating to carbon, silver, copper, nickel, solder, aluminum, and copper powder, and further, a metallic metal such as a resin ball or glass bead. A filler with a key or a mixture of these fillers is used. Silver is expensive, copper lacks heat resistance reliability, aluminum lacks moisture resistance reliability, and solder is difficult to obtain sufficient conductivity. In addition, it is preferable to use silver coated copper filler or nickel, which is more reliable.

[0023] The blending ratio of the conductive filler depends on the filler shape and the like, but is preferably 10 to: LOO parts by weight with respect to 100 parts by weight of the flame-retardant resin. It should be 15-50 parts by weight. If it exceeds 100 parts by weight, the adhesion to the ground circuit (copper foil) will decrease, the flexibility of the shield flexible printed wiring board (hereinafter referred to as shielded FPC) will deteriorate, and the flame retardancy will decrease. . On the other hand, when the amount is less than 10 parts by weight, the conductivity is remarkably lowered and the flame retardancy is lowered. The shape of the metal filler may be any of spherical, needle-like, fibrous, flake-like, and greave-like.

[0024] According to the above embodiment, since the heat-resistant and thermosetting resin is used, a flame-retardant shield film that can be used without any problem even if it is subjected to a reflow process in a later step. Can be provided.

[0025] In addition, it is very thin at 35 μm or less! Even for films, it passes the UL94 vertical flammability test (VT M standard), has high adhesion to substrates, and is flexible. It is possible to reliably provide a shield film that is excellent in stability and storage stability.

[0026] Furthermore, since the flame retardant resin contains phosphorus, a highly flame retardant shield film can be provided reliably.

[0027] Power! In addition, when the shield film of this embodiment is bonded to a printed circuit, the circuit pattern and the metal layer of the shield film of the present invention are conductively connected, and at this time, the electromagnetic wave shielding property can be exhibited.

[0028] The shield film of the present invention can be used for FPC, COF (chip on flex), RF (rigid flex printed board), multilayer flexible board, rigid board, etc., but is not necessarily limited thereto. In addition, as a structure when affixed to FPC, for example, a shield printed wiring board 10 as shown in FIG. 2 is obtained. Here, 5 is a base film, 6 is a printed circuit, 7 is an insulating film, and 8 is a base film.

[0029] The surface of the printed circuit 6 includes a signal circuit 6a and a ground circuit 6b. Is covered with an insulating film 7 except for at least a part (non-insulating part) 6c. The insulating film 7 has an insulating removal portion 7a into which a part of the adhesive layer 4 of the shield film 1 flows. As a result, the ground circuit 6b and the metal layer 3 are electrically connected.

[0030] Here, the base film 5 and the printed circuit 6 may be joined together with an adhesive, or in the same manner as a so-called non-adhesive copper clad laminate without using an adhesive. Also good. The insulating film 7 may be formed by a series of techniques such as application, drying, exposure, development, and heat treatment of a photosensitive insulating resin by bonding a flexible insulating film using an adhesive. good. Furthermore, the base film 8 has a single-sided FPC having a printed circuit only on one side of the base film, a double-sided FPC having a printed circuit on both sides of the base film, and a plurality of such FPCs laminated. Suitable for multilayer FPC, Fretasboard (registered trademark) with multilayer component mounting part and cable part, flex-rigid board with rigid members constituting multilayer part, or TAB tape for tape carrier package It can be carried out with appropriate adoption.

[0031] The base film 5 and the insulating film 6 are both made of engineering plastic. Examples thereof include resins such as polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyether imide, and polyphenylene sulfide (PPS). When heat resistance is not required, a low-cost polyester film is preferred, and when flame retardancy is required, polyphenylene sulfide film is preferred, and when heat resistance is required, polyimide film is preferred. .

[0032] With the above configuration, since the pattern of the ground circuit 6b and the metal layer 3 in the shield film 1 of the above embodiment are conductively connected, the shield printed wiring board 10 having excellent electromagnetic shielding properties can be provided. In addition, even a very thin film of 35 m or less can provide a shield printed wiring board that passes the UL94 vertical flammability test (V standard). In addition, since the base film 8 is FPC, it has excellent electromagnetic wave shielding properties and has flexibility, so that it is possible to provide the shield printed wiring board 10 that can be used in a portion that needs to be bent.

Example [0033] Shield films according to Examples 1 to 4 and Comparative Examples 1 to 4 having the same configuration as the shield film 1 shown in Fig. 1 were produced. Hereinafter, the shield films according to Examples 1 to 4 and Comparative Examples 1 to 4 will be described. In the shield films according to Examples 1 to 4 and Comparative Examples 1 to 4, the insulating layer 2 is made of an epoxy resin having a thickness of 5 μm, and the metal layer 3 has a thickness of 0.1 / 1 /. An xm silver deposition layer was used. Adhesive layer 4 has a thickness of 100 parts by weight of a phosphorus-containing epoxy resin (flame retardant resin), and a predetermined amount of a flame retardant composed of melamine cyanurate is added to each layer, and the silver-coated copper powder is also conductive. The ones added with 20 parts by weight of the filler were used (see Table 1).

[0034] [Table 1]

(Method for producing shield films of Examples 1 to 4 and Comparative Examples 1 to 4)

First, the metal layer 3 and the adhesive layer 4 having the components of each Example and each Comparative Example in Table 1 above were provided on one surface of the insulating layer 2 to obtain shield films for each Example and each Comparative Example. . In the tests other than the flame retardancy test and the flexibility test, in order to evaluate the shield films of Examples 1 to 4 and Comparative Examples 1 to 4, the shield films of each Example and each Comparative Example were used. After 3MPa pressing at 3 ° C for 3 minutes and bonding to the substrate of each test, after-curing at 150 ° C for 60 minutes is used.

[0036] (Reflow resistance test method) The following reflow resistance test was performed on the shield films of Examples 1 to 4 and Comparative Examples 1 to 4. Each shield film is bonded to the copper foil of the copper-clad laminate (F-30VC1 made by Futtsukan Kogyo Co., Ltd.) as the base material so that the adhesive layer adheres, with the insulation layer side of the shield film facing up. And passed through an IR reflow furnace (peak temperature: 265 ° C). Thereafter, the appearance of abnormal appearance such as swelling and peeling of the insulating layer surface of the shield film was visually evaluated. The results are shown in Table 1, with 〇 indicating that there are no abnormalities such as blistering and peeling, and X indicating that there are abnormalities such as blistering and peeling.

[0037] (Flame retardance test (VTM standard) method)

The following flame retardancy tests were conducted on the shield films of Examples 1 to 4 and Comparative Examples 1 to 4. First, after the transfer film was formed on the surface of the adhesive layer of each shield film using the above production method, each shield film alone was pressed at 170 ° C. for 3 minutes for 3 MPa. Next, the transfer film was peeled off and after-curing was performed at 150 ° C. for 60 minutes. Each shield film was wound around a mandrel, rolled, removed, and each was evaluated for flame retardancy according to the UL-94 vertical flammability test (VTM standard). The results are shown in Table 1, where V TM-0 passed 0 and X failed.

[0038] (Method of flame retardancy test (V standard))

The UL-94 vertical combustion was applied to the shield films of Examples 1 to 4 and Comparative Examples 1 to 4 bonded to a polyimide film with a thickness of 25 μm (Kapton 100H manufactured by Toray DuPont Co., Ltd.). The flame retardancy was evaluated according to the property test (V standard). Table 1 shows the results when V—0 passed and O, and X failed.

[0039] (Adhesion test method)

The following adhesion tests were performed on the shield films of Examples 1 to 4 and Comparative Examples 1 to 4. First, using the above production method, each shield film was bonded to a polyimide film with a thickness of 25 m (Kapton 100H, manufactured by Toray DuPont Co., Ltd.) so that the adhesive layer would adhere. . Next, the polyimide film was peeled 180 °, and the strength (adhesion) of the shield film was measured. The results are shown in Table 1 with a strength of 4. ONZcm or higher as ○ (passed) and 4. less than ON / cm as X (failed).

[0040] From the above results, it is necessary to perform reflow in a later process without lowering the adhesion to a printed circuit or the like. It can be seen that a flame-retardant shield film that can be used without problems even if it is mounted, and a shield printed wiring board using the same can be provided.

It should be noted that the present invention can be modified in design without departing from the scope of the claims, and is not limited to the above embodiment.

Brief Description of Drawings

FIG. 1 is a partial cross-sectional view of a shield film according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of an FPC with the shield film of FIG.

Explanation of symbols

1 Shield film

2 Insulating layer

3 Metal layer

4 Adhesive layer

5 Base Finolem

6 Printed circuit

6a Signal circuit

6b Ground circuit

6c Non-insulated part

7 Insulating film

7a Insulation removal part

8 Substrate film

10 Shield printed wiring board

Claims

The scope of the claims

[1] A shield film comprising an insulating layer and a shield layer containing a highly heat-resistant flame retardant resin.

[2] The shield film according to claim 1, wherein the shield layer has one or more isotropic conductive adhesive layers formed on at least one surface of the insulating layer.

3. The shield layer according to claim 1, wherein the shield layer has one or more metal layers formed on at least one surface of the insulating layer and one or more anisotropic conductive adhesive layers. Noh.

[4] The conductive adhesive layer further contains a flame retardant,

The shield film according to any one of claims 1 to 3, wherein the flame retardant is blended in an amount of 10 to 180 parts by weight with respect to 100 parts by weight of the flame retardant resin.

[5] The flame retardant resin contains a phosphorus-containing flame retardant resin!

The shield film according to item 1 to ~ 3!

[6] A shield printed wiring board comprising the shield film according to any one of claims 1 to 3 on at least one surface of a substrate including one or more printed circuits.

7. The shielded printed wiring board according to claim 6, wherein the substrate is a flexible printed wiring board.