WO2010067485A1

WO2010067485A1 - Shield film and shielded circuit board

Info

Publication number: WO2010067485A1
Application number: PCT/JP2009/003677
Authority: WO
Inventors: 大門正英; 木村武雄; 石井淳一; 須永友康; 野村麻美子; 金谷紘希
Original assignee: ソニーケミカル＆インフォメーションデバイス株式会社
Priority date: 2008-12-12
Filing date: 2009-08-03
Publication date: 2010-06-17
Also published as: TW201022029A; JP2010161324A

Abstract

A shield film which eliminates the possibility of phosphorus precipitation during solder reflow and also eliminates impairment of electromagnetic shielding even when ground openings are small is formed by laminating to a protective layer an electrically conductive adhesive layer of an electrically conductive filler dispersed in a binder resin. The binder resin contains a siloxane residue-containing polyimide, and the siloxane residue-containing polyimide has a repeating structural unit represented by formula (A). (In the formula, n is an integer from 1-30, and m is an integer from 0-20.)

Description

Shield film and shield wiring board

The present invention relates to a shield film excellent in electromagnetic wave shielding properties and a shield wiring board having the shield film attached thereto.

Since recent precision electronic devices such as personal computers and mobile phones are easily affected by electromagnetic waves, circuit electromagnetic wave shielding films are stuck on the circuit forming surfaces of various wiring boards in the devices. Here, an overcoat layer is provided on the circuit forming surface of the wiring board, and a ground opening for conducting the ground circuit and the shield film is formed in the overcoat layer.

As such a shield film, a film in which a shield layer is laminated on an insulating layer located on the outermost surface after being attached to a wiring board has been proposed (Patent Document 1). In the Example of this patent document 1, as a shield layer, the silver vapor deposition layer laminated | stacked on the epoxy resin insulating layer, and 20 weight part of silver coat copper powder as an electroconductive filler in the silver vapor deposition layer are flame-retardant. There has been proposed an anisotropic conductive adhesive layer formed by uniformly dispersing in a blend of 100 parts by weight of a thermosetting phosphorus-containing epoxy resin and 10 to 180 parts by weight of a non-halogen flame retardant. Yes.

When sticking such a shield film to a wiring board, the anisotropic conductive adhesive layer of the wiring board is laminated on the anisotropic conductive adhesive layer of the shield film on the circuit forming surface of the wiring board and hot-pressed. The electromagnetic wave shielding property of the shield film is realized by curing while pushing into the ground opening, thereby conducting the ground circuit and the silver deposited layer.

JP 2007-294918 A

However, in the case of the shield film of Patent Document 1, there is a concern that phosphorus precipitates during the solder reflow treatment and damages wiring and electronic components. In addition, as the mounting density is improved, the diameter of the ground opening is reduced (for example, 0.2 mm or less), so that it is difficult to sufficiently push the anisotropic conductive adhesive layer. There is also a concern that the conduction reliability between the two will decrease and the electromagnetic shielding characteristics will deteriorate.

The object of the present invention is to solve the above-mentioned problems of the prior art, and there is no possibility of precipitation of phosphorus during solder reflow, and the shielding film does not impair electromagnetic wave shielding even when the ground opening is small. Is to provide.

Since the present inventors have a limit in the use of the anisotropic conductive adhesive layer in relation to the ground opening diameter, the conductive property in which the conductive filler is dispersed in the binder resin in the insulating protective layer. In the two-layer type shield film provided with an adhesive layer, the above-mentioned object can be achieved by including a specific siloxane residue-containing polyimide, which is a kind of thermoplastic resin that is flexible and has excellent indentability, in the binder resin. The present invention was completed.

That is, the present invention is a shield film in which a conductive adhesive layer in which a conductive filler is dispersed in a binder resin is laminated on a protective layer, and the binder resin contains a siloxane residue-containing polyimide. A shield film is provided.

Moreover, this invention is a manufacturing method of the above-mentioned shield film, Comprising: The following processes:
Applying a coating material for forming a protective layer to the first release substrate, and forming a protective layer by drying;
Applying a conductive adhesive layer-forming coating material containing a binder resin containing a siloxane residue-containing polyimide and a conductive filler to the second release substrate, and forming a conductive adhesive layer by drying;
There is provided a manufacturing method comprising a step of forming a shield film by bonding a protective layer and a conductive adhesive layer to each other.

Furthermore, the present invention provides a shield wiring board characterized in that the above-mentioned shield film is laminated with a conductive adhesive layer so as to be electrically connected to the ground wiring on the wiring board on which the ground wiring is formed. provide.

Since the shield film of the present invention does not use a phosphorus-containing epoxy resin for the binder resin of the conductive adhesive layer, there is no possibility that phosphorus will precipitate during solder reflow. In addition, since a specific polyimide containing thermoplastic siloxane residue is used, even when the ground opening of the wiring board is small, it is easy to push into the ground opening, so the reliability of conduction between the ground circuit and the conductive adhesive layer And high electromagnetic shielding properties can be realized. Moreover, good flame retardancy can be achieved.

FIG. 1 is a cross-sectional view of a shield film. FIG. 2 is an overall view of a synthesis apparatus for producing a siloxane polyimide resin. FIG. 3 is a plan perspective view of the shield wiring board (the shield film is seen through). FIG. 4 is a measurement view of the shielding effect of the shielding film. FIG. 5 is a GC-MS chart of the vacuum recovery A obtained in Reference Example 1.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a shield film 10 of the present invention. This shield film 10 has a structure in which a conductive adhesive layer 4 in which a conductive filler 2 is dispersed in a binder resin 3 is laminated on a protective layer 1, and the binder resin 3 contains a siloxane residue-containing polyimide. It is characterized by that.

(I) Protective layer 1
The protective layer 1 constituting the shield film 10 of the present invention is located on the outer surface when the shield film is applied to an adherend such as a wiring board, and from the force or humidity from the outside of the adherend. It has a function to protect and also functions as a support for the conductive adhesive layer 4 described above.

As such a protective layer 1, the same configuration as the protective layer in the conventional shield film 10 can be adopted. For example, a resin film having a thickness of 5 to 15 μm, for example, a polyester film, a polyimide film, a polyether film, a polyphenylene sulfide film, or the like can be used. Among these, from the viewpoint of flame retardancy, flexibility, and flexibility, a film in which a siloxane residue-containing polyimide constituting the binder resin of the conductive adhesive layer 4 described later is formed can be preferably used. In this case, it is preferable to form a film with a siloxane residue-containing polyimide alone, but it may be formed from a binder resin containing a siloxane residue-containing polyimide.

(II) Conductive adhesive layer 4
The conductive adhesive layer 4 constituting the shield film 10 of the present invention is a layer that adheres the shield film 10 to an adherend such as a wiring board and exhibits electromagnetic shielding properties.

If the thickness of the conductive adhesive layer 4 is too thin, the conductivity and shielding properties are insufficient, and if it is too thick, the flexibility and flexibility are lowered. Therefore, the thickness is preferably 5 to 20 μm, more preferably 7 to 15 μm.

(IIA) Siloxane residue-containing polyimide constituting the binder resin 3 As described above, in the present invention, the siloxane residue-containing polyimide is blended in the conductive adhesive layer, but this resin is thermoplastic, and when melted. It has a siloxane residue that contributes to improved fluidity. Moreover, it has an imide bond and a benzene ring that contribute to flame retardancy. Therefore, in the shield film of the present invention, there is no possibility that phosphorus is precipitated during solder reflow. Moreover, even when the ground opening of the wiring board is small, the conduction reliability between the ground circuit and the conductive adhesive layer can be improved, and good electromagnetic shielding properties can be realized. In addition, good flame retardancy can be achieved.

In the present invention, preferred siloxane residue-containing polyimides include those having a repeating structural unit of the formula (A).

In the formula (A), n is an integer of 1 to 30, preferably 1 to 20, and m is an integer of 0 to 20, preferably 1 to 20. When flame retardancy is not particularly required, it is preferable to use a siloxane diamine having m = 0, and when flame retardancy is required, m having 1 or more is preferably used. Specific examples of the siloxane residue-containing polyimide of the formula (A) include m-22, X-22-161A, X-22-161B, KF8008, KF8012 (above, Shin-Etsu Chemical Co., Ltd.), BY16-871, BY16. -853C, BY16-853u (above, Toray Dow Corning), Silaace FM3311 (Chisso), etc., and m> 1, X-22-1660B3 (Shin-Etsu Chemical Co., Ltd.), etc. it can.

The siloxane residue of the siloxane residue-containing polyimide of the formula (A) is preferably derived from the siloxane diamine component when producing the polyimide, specifically derived from the siloxane diamine of the formula (1). To do. In the formula (1), n and m are as described in the formula (A). Specific examples of such siloxane diamines include KF-8010 (m = 0) and X-22-9409 (m> 1) manufactured by Shin-Etsu Chemical Co., Ltd. As the siloxane diamine, those having an amino group protected by a carbamate type such as a tert-butoxycarbonyl group, an imide type such as a phthaloyl group, or a sulfonamide type such as a p-toluenesulfonyl group can be used.

If the content of the siloxane residue-containing polyimide in the conductive adhesive layer 4 of the shield film 10 of the present invention is too small, it is difficult to push into the ground opening, and if it is too large, the content of the conductive filler is relatively reduced. In either case, the conduction reliability is lowered, so the content is preferably 4 to 12% by mass, more preferably 6 to 9% by mass.

(IIB) Production Method of Siloxane Residue-Containing Polyimide As the siloxane residue-containing polyimide used in the present invention, one produced by a known method can be used, but at least tetracarboxylic dianhydride, siloxane diamine, What was obtained by the method of manufacturing siloxane polyimide resin by making this react can be used preferably. Specifically, those obtained by the production method having the following steps (a) to (c) can be preferably used.

(A) a step of imidizing a first tetracarboxylic dianhydride and a siloxane diamine in a solvent under a reflux condition to obtain a reaction mixture containing an acid anhydride terminal or an amine terminal siloxane imide oligomer;
(B) concentrating the reaction mixture obtained in step (a) under reduced pressure to obtain a reaction concentrate; and (c) adding a solvent and a siloxane-free diamine to the reaction concentrate obtained in step (b). And the siloxane-free diamine and the acid anhydride-terminated siloxane imide oligomer in the reaction concentrate are imidized, or the solvent and the second tetracarboxylic dianhydride are added, and the second tetracarboxylic acid is added. A step of imidizing the dianhydride and the amine-terminated siloxane imide oligomer in the reaction concentrate, thereby obtaining a siloxane polyimide resin.

Hereafter, each process will be described, but the effect of this manufacturing method will be added. That is, in this production method, siloxane diamine out of diamine components is first subjected to an imidization reaction with a tetracarboxylic dianhydride component to obtain an acid anhydride terminal or amine terminal siloxane imide oligomer, and after the reaction is completed. The volatile impurities such as cyclic siloxane oligomer are removed together with the solvent under reduced pressure. For this reason, not only cyclic siloxane oligomers up to hexamers but also siloxane oligomers and free siloxane compounds of 7-mers or more that bleed out can be removed. Therefore, cyclic siloxanes that affect the properties of siloxane polyimide resins when an acid-terminated or amine-terminated siloxane imide oligomer is additionally imidized with a siloxane-free diamine or tetracarboxylic dianhydride. No ring opening of the oligomer occurs. Therefore, the shield film using the siloxane residue-containing polyimide obtained by this production method prevents the bleed-out phenomenon of the cyclic siloxane oligomer, and greatly reduces the amount of outgas generated from the cyclic siloxane oligomer during reheating. Therefore, it is suitable for electromagnetic wave shielding use of wiring boards for various electronic components.

Step (a)
First, the first tetracarboxylic dianhydride and siloxane diamine are imidized under reflux conditions in a solvent to obtain a reaction mixture containing an acid anhydride terminal or amine terminal siloxane imide oligomer.

In order to obtain an acid anhydride-terminated siloxane imide oligomer, the molar amount of the first tetracarboxylic dianhydride may be increased as compared with siloxane diamine. Conversely, in order to obtain an amine-terminated siloxane imide oligomer, the molar amount of the first tetracarboxylic dianhydride may be made smaller than that of siloxane diamine. However, if the amount of siloxane diamine used is too small relative to 1 mol of all tetracarboxylic dianhydrides, it tends to be difficult to maintain adhesion and flexibility, and if too large, heat resistance tends to decrease. Therefore, the amount is preferably 0.1 to 0.9 mol, more preferably 0.3 to 0.8 mol.

In the step (a), the reason for carrying out the imidization reaction under reflux is to remove the imidized water by azeotropic distillation with a solvent using a Dean-Stark separation tube or the like. Therefore, as the solvent, a solvent that is refluxed at a temperature at which an imidization reaction between tetracarboxylic dianhydride and siloxane diamine occurs and can separate water by azeotropy is used. Examples of such a solvent include glymes such as diglyme and triglyme, ether solvents such as dioxane and tetrahydrofuran, lactone solvents such as γ-butyrolactone and γ-valerolactone, and mixtures thereof. In addition, a nonpolar solvent such as toluene, xylene, benzene or mesitylene and a solvent such as N-methyl-2-pyrrolidone may be used in combination as long as the effects of the invention are not impaired. In this step (a), a mixed solvent of glymes and a nonpolar solvent, preferably a mixed solvent of triglyme and at least one selected from the group consisting of benzene, toluene, xylene and mesitylene, in view of reflux temperature and the like. (W / w = 1 / (0.1 to 10)) can be preferably used.

The amount of solvent used in step (a) varies depending on the type of solvent and reaction substrate, but if it is too small, it will cause poor monomer dispersion and decrease in reflux efficiency. If it is too large, the heat of vaporization of the solvent will increase and the temperature in the reaction vessel will increase. Therefore, the total mass of the first tetracarboxylic dianhydride and the siloxane diamine is preferably used in an amount of 5 to 60% by mass.

The reaction temperature of the imidation reaction varies depending on the type and amount of the solvent and reaction substrate, but if it is too low, the imidization reaction cannot be completed, and if it is too high, side reactions other than the imidization reaction may occur. The temperature is preferably 150 to 220 ° C, more preferably 160 to 200 ° C. The reaction time is the time required to remove the theoretical amount of imidized water, and is usually 0.5 to 12 hours, preferably 1 to 8 hours.

Specific examples of the first tetracarboxylic dianhydride used in the present invention include pyromellitic dianhydride, 3,4,3 ', 4'-biphenyltetracarboxylic dianhydride, 4,4'- Oxydiphthalic dianhydride, 3,4,3 ', 4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride, 9,9-bis (3 , 4-Dicarboxyphenyl) fluorene dianhydride, 9,9-bis [4- (3,4-dicarboxyphenoxy) phenyl] fluorene dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3 5,6-tetracarboxylic dianhydride, ethylene glycol Visto Increment Ried dianhydride, 2,2-bis (4- (3,4-dicarboxyphenoxy) phenyl) can be mentioned propane dianhydride and the like. Of these, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride can be preferably used.

The siloxane diamine used in the present invention is a compound having a dimethylsilylene skeleton at least in the molecule, and those conventionally used for siloxane modification of polyimide resins can be used. Especially, what has the structure of Formula (1) mentioned above from the point of a flame retardance and compatibility ensuring can be used preferably.

In addition, in the imidization in the step (a), a tertiary amine such as triethylamine, a basic catalyst such as aromatic isoquinoline and pyridine, and an acid catalyst such as benzoic acid and parahydroxybenzoic acid are added as necessary. May be.

Step (b)
After completion of the reaction in step (a), the reaction mixture obtained in step (a) is concentrated under reduced pressure to obtain a reaction concentrate. This step (b) is a step of removing the cyclic siloxane oligomer when the cyclic siloxane oligomer is contained as an impurity in the siloxane diamine used in the step (a). That is, by concentrating under reduced pressure, a volatile cyclic siloxane oligomer and a free siloxane compound (for example, low molecular weight siloxane monoamine, low molecular weight siloxane) can be efficiently removed together with a solvent and a small amount of water. If the temperature during this concentration under reduced pressure is too low, the removal efficiency of the cyclic siloxane oligomer or free siloxane compound deteriorates, so the temperature is the same as the imidation reaction temperature in step (a) or the solvent boiling temperature at atmospheric pressure. It is preferable.

The pressure at the time of concentration under reduced pressure is preferably 0.3 because the removal efficiency of the cyclic siloxane oligomer or free siloxane compound deteriorates if the degree of pressure reduction is not sufficient, and conversely, excessive pressure reduction causes an excessive increase in processing costs. ~ 91kPa, more preferably 11 ~ 51kPa.

Step (c)
Next, when the reaction concentrate obtained in step (b) is an acid anhydride-terminated siloxane imide oligomer, a solvent and a siloxane-free diamine are added to the reaction concentrate, and a siloxane-free diamine and an acid are added. An anhydride-terminated siloxane imide oligomer is imidized to obtain a siloxane polyimide resin. In this case, you may add a 2nd tetracarboxylic dianhydride with a siloxane non-containing diamine as needed.

Alternatively, when the reaction concentrate is an amine-terminated siloxane imide oligomer, a solvent and a second tetracarboxylic dianhydride are added to the reaction concentrate, and the reaction concentration with the second tetracarboxylic dianhydride is added. The amine-terminated siloxane imide oligomer in the product is imidized to obtain a siloxane polyimide resin. In this case, a siloxane-free diamine may be added together with the second tetracarboxylic dianhydride as necessary.

The reason why the solvent is added after the step (b) is to adjust the solvent, and the polyimide solid content concentration can be adjusted by the step. As the solvent, those that can be used in step (a) can be used. In particular, when a siloxane polyimide resin is used as a varnish, in order to prevent polyimide precipitation due to moisture absorption during coating, an ether solvent, a lactone solvent, a nonpolar solvent, etc., which are relatively low hygroscopic solvents, or Can be used as a mixture. In particular, in this step (c), a mixed solvent of triglyme (also known as triethylene glycol dimethyl ether) and γ-butyrolactone (w / w = 1 / (0.1 to 10)) can be preferably used.

As the “siloxane-free diamine” used in the step (c), a diamine having no dimethylsilylene skeleton in the molecule can be used, and specific examples thereof include 3,3′-diamino-4,4 ′. -Dihydroxydiphenylsulfone, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) propane, 3,3'-diamino-4, Diaminophenol derivatives such as 4'-dihydroxydiphenylmethane, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,4-diaminophenol, 9,9-bis (3-amino-4-hydroxyphenyl) fluorene; p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis [4- (4 Aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 1,3-bis (4-aminophenoxy) benzene, 2,2'-bis (trifluoromethyl) -4,4 ' -Diaminobiphenyl, 1,3-bis (3-aminophenoxy) benzene, 4,4'-diaminobenzanilide, 5,5'-methylene-bis (anthranic acid), 9,9-bis [4- (4 -Aminophenoxyphenyl)] fluorene, 9,9-bis (4-aminophenoxy) fluorene, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl ether, 2,2-bis [4- (4-amino Phenoxy) phenyl] hexafluoropropane, 4,4′-bis (4-aminophenoxy) biphenyl, 1,4-bis (4- Minophenoxy) aromatic diamines such as benzene and o-tolidine sulfone; aliphatic diamines such as trans-1,4-cyclohexanediamine, cis-1,4-cyclohexanediamine, and 4,4'-methylenebis (cyclohexylamine) However, it is not limited to these.

On the other hand, as the “second tetracarboxylic dianhydride”, those similar to the first tetracarboxylic dianhydride already exemplified can be used. Here, the first tetracarboxylic dianhydride and the second tetracarboxylic dianhydride may be the same or different.

When the reaction concentrate obtained in step (b) is an acid anhydride-terminated siloxane imide oligomer, the amount of siloxane-free diamine used in step (c) is the molecular weight for obtaining a coverlay with sufficient mechanical properties. In order to ensure the above, the total number of moles of siloxane diamine is preferably 0.1 to 0.9 mol, more preferably 0.3 to 0.8 mol, relative to 1 mol of all tetracarboxylic dianhydrides. This is the amount.

On the other hand, when the reaction concentrate obtained in step (b) is an amine-terminated siloxane imide oligomer, the amount of the second tetracarboxylic dianhydride used in step (c) is sufficient in mechanical properties. In order to ensure the molecular weight for obtaining the coverlay, siloxane diamine and siloxane are not contained with respect to 1 mole of the total number of moles of the first tetracarboxylic dianhydride and the second tetracarboxylic dianhydride. The total amount of diamine components combined with diamine is preferably 0.8 to 1.2 mol, more preferably 0.9 to 1.1 mol.

In the imidization in the step (c), as in the case of the step (a), a tertiary catalyst such as triethylamine, a basic catalyst such as aromatic isoquinoline, pyridine, benzoic acid, An acid catalyst such as parahydroxybenzoic acid may be added.

When an acid dianhydride or diamine component having a polar group is used in step (c), the viscosity of the siloxane polyimide resin produced by the Weiselberg effect increases, and a phenomenon of winding around the stirring rod may occur. is there. In order to avoid an increase in the viscosity of the produced siloxane polyimide resin, it is preferable that water be present in the reaction system. In this case, if the amount of water is too small, the risk of thickening increases, and if it is too large, the molecular weight of the polyimide may decrease. Therefore, water is added at a ratio of 0.01 to 1.1% by mass in the reaction mixture. Preferably it is present.

The reaction temperature at the time of imidization in step (c) varies depending on the type and amount of the solvent and reaction substrate, but if it is too low, the imidization reaction is not completed, and if it is too high, side reactions other than the imidization reaction occur. Since there is a possibility, it is preferably 150 to 220 ° C., more preferably 160 to 200 ° C. The reaction time is usually 0.5 to 12 hours, preferably 1 to 8 hours. Thereby, the siloxane residue containing polyimide with little content of a cyclic siloxane oligomer and a free siloxane compound is obtained in a varnish state.

The siloxane residue-containing polyimide used in the present invention can be produced in one batch using the synthesis apparatus shown in FIG.

FIG. 2 is an overall view of a synthesis apparatus for producing a siloxane polyimide resin. This synthesizer includes a reaction vessel 22 that can be heated by a heating device 21, a condenser 23 mounted above the reaction vessel 22, a condensation trap tank 24 that traps condensate condensed in the condenser 23, and a reaction vessel. 22 has a gas introduction pipe 25 for introducing gas. The condensation trap tank 24 is provided with a drain 24a for discharging the stored condensate out of the system. The condensation trap tank 24 and the reaction vessel 22 are connected by an overflow pipe 26 for returning excess condensate to the reaction vessel 22 when a predetermined amount or more of condensate is stored in the condensation trap vessel 24. Yes. The gas introduction pipe 25 is installed in the reaction vessel 22 so as to be positioned below the overflow surface 26 a of the overflow pipe 26. Further, a pressure reducing device 27 is connected to the reaction vessel 22. Here, the reason for installing the gas introduction pipe 25 in the reaction vessel 22 so as to be positioned below the overflow surface 26a of the overflow pipe 26 is that the gas introduction pipe 25 is close to the liquid level of the reaction mixture RM in the reaction vessel 22. This is because the cyclic siloxane oligomer volatilized from the liquid level of the reaction mixture RM, water, and the solvent can be efficiently guided to the condenser 23 on the gas flow. The reaction vessel 22 is provided with a stirring device 28. Although not shown, a temperature measuring device is also installed.

As the individual parts constituting the synthesis apparatus of FIG. 2, those used in the conventional chemical reaction apparatus can be appropriately selected and used.

(IIC) Components other than the siloxane residue-containing polyimide of binder resin 3
(IICa) In order to provide the conductive adhesive layer 4 with thermosetting property to the binder resin 3 constituting the epoxy resin and the epoxy resin curing agent conductive adhesive layer 4 in order to ensure the conduction reliability of the shield film. Various thermosetting resins and curing agents therefor can be blended. An epoxy resin can be used as a particularly preferable thermosetting resin. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, alicyclic epoxy resin, and the like can be used. These may be liquid or solid. Moreover, as a hardening | curing agent for epoxy resins, a well-known hardening | curing agent (For example, an amine type hardening | curing agent, an imidazole type hardening | curing agent, a polymercaptan type hardening | curing agent, an acid anhydride type hardening | curing agent etc.) can be mentioned. Among them, although it has a relatively high curing temperature, it has a relatively long pot life and can provide a well-balanced cured product having electrical, chemical and mechanical properties (for example, phthalic anhydride). Aromatic acid anhydrides such as acids, alicyclic acid anhydrides such as tetrahydrophthalic anhydride, and aliphatic acid anhydrides such as succinic anhydride can be preferably used. Especially, since it is a low-viscosity liquid at room temperature, an alicyclic acid anhydride can be preferably used.

When the binder resin is used in combination with the epoxy resin and the epoxy resin curing agent in addition to the siloxane residue-containing polyimide, the binder resin preferably contains 65 to 230 parts by mass of the epoxy resin with respect to 100 parts by mass of the siloxane residue-containing polyimide. More preferably, it is contained in an amount of 100 to 140 parts by mass. The epoxy resin curing agent is preferably contained in an amount of 45 to 150 parts by mass, more preferably 70 to 100 parts by mass.

(IICb) Conductive filler As the conductive filler 2 used in the present invention, a conductive filler used in a so-called conductive paste can be used. For example, metal powder such as flat silver and copper, metal coat metal powder such as silver coat copper powder, Ni coat of flat styrene particle core, metal coat resin powder such as Au flash plating, etc. can be used. Spherical conductive particles such as those used in anisotropic conductive adhesives can also be used. You may mix and use both.

The average particle size of the conductive filler 2 is preferably 2 to 20 μm, more preferably 5 to 10 μm, because if it is too small, the conductivity will be insufficient, and if it is too large, the pushability to the ground will deteriorate. . When the conductive filler is flat, the particle size corresponds to the major axis, and the thickness is preferably 5 to 40% of the major axis.

If the content of the conductive filler 2 in the conductive adhesive layer 4 is too small, the conduction reliability of the shield film becomes insufficient, and if it is too large, the film strength of the conductive adhesive layer 4 itself is lowered. It is ˜85 mass%, more preferably 70 to 80 mass%.

(IICc) Other components In the conductive adhesive layer 4 in the present invention, a thermoplastic resin such as polyester and polyamide, a colorant, an antiseptic, a dispersing agent, and the like are added to the conductive adhesive layer 4 as long as the effects of the present invention are not impaired. It can be included.

(IID) Production of shield film The shield film of the present invention can be produced according to a conventional method. For example, a conductive adhesive layer is formed by uniformly mixing a siloxane residue-containing polyimide, a conductive filler, and, if necessary, a curing agent for an epoxy resin and an epoxy resin together with a solvent solvent such as toluene using a known mixer. It can be manufactured by preparing a coating material for coating, and applying and drying the obtained coating material to the resin film to be the protective layer 1. If necessary, a release sheet can be laminated on the conductive adhesive layer side of the shield film. Moreover, it obtained by apply | coating and drying the resin liquid which mixed the siloxane residue containing polyimide, the epoxy resin, and another thermoplastic resin on the peeling PET (polyethylene terephthalate) film as a resin film used as the protective layer 1. A protective layer film with release PET can also be used.

In addition, the shield film of the present invention, as an alternative method, includes the following steps:
Applying a protective layer-forming coating material to the first release substrate and drying to form a protective layer;
Applying a conductive adhesive layer-forming coating material containing a binder resin containing a siloxane residue-containing polyimide and a conductive filler to the second release substrate, and forming a conductive adhesive layer by drying;
It can manufacture with the manufacturing method which has the process of forming a shield film by bonding together a protective layer and a conductive contact bonding layer.

As the first release substrate, for example, a known release-treated polyester film, polyolefin film, nylon film or the like can be used. As the protective layer-forming coating material, an insulating resin-based coating material can be widely used. However, it is difficult to use a coating material in which the siloxane residue-containing polyimide characterizing the present invention is dissolved in a solvent such as triglyme or γ-butyrolactone. It can be preferably used in terms of flammability, flexibility and insulation. It should be noted that publicly known techniques and conditions can be employed for applying and drying the protective layer-forming paint.

As the second peeling substrate, the same one as the first peeling substrate can be used. The conductive adhesive layer-forming coating material is obtained by dissolving and dispersing a binder resin containing a siloxane residue-containing polyimide and a conductive filler in a solvent such as triglyme or γ-butyrolactone. Known techniques and conditions can be employed for applying and drying the conductive adhesive layer-forming coating material.

The lamination of the protective layer and the conductive adhesive layer can be preferably performed with a heat laminator or a hot press plate at 100 to 130 ° C.

As a specific production example of a shield film, first, a resin solution in which a siloxane residue-containing polyimide varnish, an epoxy resin, or another thermoplastic resin is mixed is applied onto a silicone release-treated PET film with a bar coater. The protective layer 1 with peeled PET is formed by putting in a drying furnace at 100 to 150 ° C. and drying. Separately, the conductive adhesive layer 4 with peeled PET is formed by applying and drying a varnish for forming a conductive adhesive layer on the peeled PET film. Then, the protective layer 1 and the conductive adhesive layer 4 are overlapped with each other and bonded together with a heat laminator at 100 to 130 ° C., whereby a shield film in which both surfaces are sandwiched with a peeled PET film can be manufactured. Such a shield film is used by peeling the peeled PET film on the conductive adhesive layer side, bringing the conductive adhesive layer into contact with the adherend, and hot pressing.

(III) Shield Wiring Board The shield film of the present invention described above can be preferably used for electromagnetic wave shielding of the wiring board on which the ground wiring is formed. FIG. 3 shows a plan perspective view of the shield wiring board 30. The shield wiring board 30 has a ground wiring 32 formed on a known wiring board 31 such as a flexible substrate or a glass epoxy substrate, and a cover coat layer 33 having a thickness of 10 to 37 μm such as a polyimide film. Are stacked. A ground opening 34 having a diameter of 0.2 to 1.8 μm is formed in the cover coat layer 33 up to the ground wiring 32. The shield film 35 is attached to the cover coat layer 33 of the wiring board 31 from the conductive adhesive layer side by hot pressing and is pressed into the ground opening 34. In addition, a conduction measurement opening 36 is formed at the end of the wiring board 31.

This shield wiring board 30 does not deposit phosphorus even if it is subjected to solder reflow treatment, and uses a specific thermoplastic siloxane residue-containing polyimide without using an anisotropic conductive adhesive. Therefore, the conductive adhesive layer can be sufficiently pushed into the ground opening, and a good magnetic wave shielding property is realized. Moreover, the flame retardancy is also good.

Such a shield wiring board 30 can be manufactured using, for example, a shield film having both surfaces sandwiched by a peeled PET film. That is, by peeling the peeled PET film on the conductive adhesive layer side of the shield film sandwiched between the peeled PET films on both sides, overlapping the conductive adhesive layer on the ground wiring side of the substrate, and hot pressing from the peeled PET film side Can be manufactured. Finally, the peeled PET film on the surface may be removed.

Hereinafter, the present invention will be specifically described with reference to examples.

Reference Example 1 (Example of synthesizing a siloxane residue-containing polyimide via an acid anhydride-terminated siloxane imide oligomer)
In a reaction vessel (20 L) of the siloxane residue-containing polyimide synthesizer in FIG. 2, 4372.65 g (3.24 mol) of diaminosiloxane (amine equivalent 675 g / mol, X-22-9409, manufactured by Shin-Etsu Chemical Co., Ltd.) 1994.54 g (5.54 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (Ricacid DSDA, Shin Nihon Rika Co., Ltd .; purity 99.6%), 3000 g of triglyme, 1100 g of toluene was added and the mixture was stirred well for 2 hours. Thereafter, the temperature was raised to 185 ° C., maintained at that temperature for 2 hours, and the reaction liquid was stirred under reflux while collecting water in a condensation trap tank.

While maintaining the temperature of the reaction solution at 185 ° C., the pressure in the system is reduced to 11 KPa to obtain a reduced-pressure recovered product A containing a solvent, water, and a cyclic siloxane oligomer, and a reaction concentrate (acid anhydride-terminated siloxane imide). Oligomer). The oligomer solution was applied on the silicon wafer from which the oxide film was removed, dried at 100 ° C. for 10 minutes, and terminal functional groups were identified by the FT-IR transmission method. Absorption of imide carbonyl appeared in the vicinity of 1780 cm ⁻¹ , and absorption of cyclic acid anhydride carbonyl stretching vibration was confirmed in the vicinity of 1860 cm ⁻¹ , confirming the formation of an acid anhydride-terminated siloxane imide oligomer.

The reaction concentrate was allowed to cool to 80 ° C., and 632.81 g (2.25 mol) of 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone (BSDA, manufactured by Konishi Chemical Industries, Ltd .; purity 99.75) was added to the reaction concentrate. 7%), 3300 g of triglyme (TriGL) and 700 g of γ-butyrolactone were added and stirred at room temperature for 12 hours. After stirring, the temperature was raised to 185 ° C., and the mixture was heated and stirred at that temperature for 2 hours. Then, it cooled to room temperature and obtained the varnish of the siloxane residue containing polyimide. In this reference example, the total acid dianhydride / total diamine ratio was 1.01. The synthesis route is shown below.

Example 1
The siloxane residue-containing polyimide varnish prepared in Reference Example 1 was diluted with a mixed solvent of 9: 1 (mass ratio) of triglyme and γ-butyrolactone so that the resin ratio was 48% by mass. The obtained diluted solution was coated and dried on a peeled PET (polyethylene terephthalate) film so as to have a dry thickness of 7 μm with a bar coater to form a protective layer with a peeled PET film.

Separately, an epoxy resin mixture [mixture of 6 parts by mass of jER828US (Japan Epoxy Resin Co., Ltd.) and 2 parts by mass of jER807 (Japan Epoxy Resin Co., Ltd.)] 8 parts by mass of silver-coated copper particles (Ag Coat 1400 YP, Mitsui Kinzoku Kogyo Co., Ltd.) 78 parts by mass, 8 parts by mass of the siloxane residue-containing polyimide varnish of Reference Example 1, and 6 parts by mass of acid anhydride curing agent (Rikasit MH-700, Shin Nippon Rika Co., Ltd.) The resin solution obtained by diluting with a mixed solvent of triglyme and γ-butyrolactone to a solid ratio of 93% by mass with a mixed solvent of 9: 1 (weight ratio) was dried with a bar coater on another peeled PET. A conductive adhesive layer with a release PET film was formed by coating and drying so that the thickness was 10 μm.

The protective layer with the peeled PET film and the conductive adhesive layer with the peeled PET film obtained as described above are overlaid so that the respective peeled PET films are on the outside, and passed through a 120 ° C. thermal laminator, and both sides are peeled. A shield film sandwiched between PET films was obtained.

Example 2
The size shown in Table 1 with respect to the ground wiring 32 as shown in FIG. 3 from the conductive adhesive layer side after peeling off the release PET film on the conductive adhesive layer side of the shield film obtained in Example 1. Is temporarily attached to the wiring board 31 having the cover coat layer 33 in which the ground opening 34 is formed, and the conductive adhesive layer is opened to the ground by a vacuum high temperature press (160 to 180 ° C., 1 to 4 MPa, 45 to 75 minutes). The shield film 35 was laminated | stacked on the wiring board 31 by making it thermoset, pushing in in 34, and the shield wiring board was obtained. Here, openings 36 for continuity measurement were formed at both ends of the cover coat layer 33. An electroless nickel plating layer having a thickness of 1 to 6 μm was formed on the ground wiring at the bottom of each opening, and an electroless gold plating layer having a thickness of 0.03 to 0.15 μm was further formed.

<Evaluation>
Conduction Resistance Value Measurement For the shielded wiring board obtained in Example 2, the conduction resistance value was measured. The obtained results are shown in Table 1. In practice, the conduction resistance value is desirably 1Ω or less. As can be seen from Table 1, even when the ground opening diameter is 0.2 mm, it is 1Ω or less, indicating a good conduction resistance value, and it can be seen that the electromagnetic wave shielding is sufficiently performed.

Flame retardancy test (UL-94 VTM test)
The shield film of Example 1 was temporarily pasted on both sides of a 20 μm-thick polyimide film (Espaneck M series, Nippon Steel Chemical Co., Ltd.), and vacuum high-temperature press (160 to 180 ° C., 1 to 4 MPa, 45 to 75 minutes) A test sheet bonded together was prepared, and a UL-94 VTM test was performed on the test sheet. As a result, VTM-0 was achieved and good flame retardancy was exhibited.

Create the same test sheet and those that you created in the shielding effect measurement flame retardancy test was carried out to measure the shielding effect in the KEC method (Kansai Electronic Industry Development Center method). The obtained results are shown in FIG. As a control, the result of measuring the shielding effect of a 18 μm thick copper foil is also shown in FIG. From the results of FIG. 4, it can be seen that the shield film of Example 1 has a good shielding effect equivalent to that of the copper foil up to around 70 MHz.

Analysis of normal pressure recovered material A during production of the siloxane residue-containing polyimide of Reference Example 1 The reduced pressure recovered material A was measured using GC-MS (6890/5973 GC-MS, manufactured by Agilent). The obtained results are shown in FIG. As can be seen from these figures, not only the cyclic siloxane oligomer of 3 to 6 mer but also the cyclic siloxane oligomer of 7 mer (D7) and a free siloxane compound having a higher molecular weight can be recovered and removed.

Since the shield film of the present invention does not use a phosphorus-containing epoxy resin for the binder resin of the conductive adhesive layer, there is no possibility that phosphorus will precipitate during solder reflow. In addition, since a specific polyimide containing thermoplastic siloxane residue is used, even when the ground opening of the wiring board is small, it is easy to push into the ground opening, so the reliability of conduction between the ground circuit and the conductive adhesive layer And high electromagnetic shielding properties can be realized. Moreover, good flame retardancy can be achieved. Therefore, the shield film of the present invention is useful as an electromagnetic wave shielding material for various wiring boards.

DESCRIPTION OF SYMBOLS 1 Protective layer 2 Conductive filler 3 Binder resin 4 Conductive adhesive layer 10 Shield film 21 Heating device 22 Reaction vessel 23 Condenser 24 Condensation trap tank 24a Drain 25 Gas introduction tube 26 Overflow tube 26a Overflow surface 27 Decompression device 28 Stirrer RM Reaction mixture 30 Shield wiring board 31 Wiring board 32 Ground wiring 33 Cover coat layer 34 Ground opening 35 Shield film 36 Conduction measurement opening

Claims

A shield film in which a conductive adhesive layer in which a conductive filler is dispersed in a binder resin is laminated on a protective layer, wherein the binder resin contains a siloxane residue-containing polyimide.
The shield film according to claim 1, wherein the siloxane residue-containing polyimide has a repeating structural unit of the formula (A).

(In the formula, n is an integer of 1 to 30, and m is an integer of 0 to 20.)
The shield film according to claim 2, wherein the siloxane residue of the siloxane residue-containing polyimide is derived from the siloxane diamine of formula (1).

(In the formula, n is an integer of 1 to 30, and m is an integer of 0 to 20.)
4. The shield film according to claim 1, wherein the binder resin further contains an epoxy resin and an epoxy resin curing agent.
The shield film according to claim 4, wherein the binder resin contains 65 to 230 parts by mass of an epoxy resin and 45 to 150 parts by mass of a curing agent for epoxy resin with respect to 100 parts by mass of a siloxane residue-containing polyimide.
The shield film according to claim 4 or 5, wherein the epoxy resin curing agent is an acid anhydride curing agent.
A method for producing a siloxane polyimide resin by reacting at least tetracarboxylic dianhydride and siloxane diamine with a siloxane residue-containing polyimide, comprising the following steps (a) to (c):
(A) A step of imidizing the first tetracarboxylic dianhydride and siloxane diamine in a solvent under reflux conditions to obtain a reaction mixture containing an acid anhydride terminal or amine terminal siloxane imide oligomer (b) step Step of obtaining a reaction concentrate by concentrating the reaction mixture obtained in (a) under reduced pressure (c) Adding a solvent and a siloxane-free diamine to the reaction concentrate obtained in Step (b), and containing no siloxane The diamine and the acid anhydride-terminated siloxane imide oligomer in the reaction concentrate are imidized, or the solvent and the second tetracarboxylic dianhydride are added, and the second tetracarboxylic dianhydride is reacted and concentrated. Produced by a production method comprising a step of imidizing an amine-terminated siloxane imide oligomer in a product to thereby obtain a siloxane polyimide resin Shielding film of a claim 1, wherein.
It is a manufacturing method of the shield film of Claim 1, Comprising: The following processes:
Applying a coating material for forming a protective layer to the first release substrate, and forming a protective layer by drying;
Applying a conductive adhesive layer-forming coating material containing a binder resin containing a siloxane residue-containing polyimide and a conductive filler to the second release substrate, and forming a conductive adhesive layer by drying;
A manufacturing method comprising a step of forming a shield film by bonding a protective layer and a conductive adhesive layer together.
The manufacturing method according to claim 8, wherein the protective layer-forming coating material contains a siloxane residue-containing polyimide.
A shield film characterized in that the shield film according to any one of claims 1 to 7 is laminated with a conductive adhesive layer so as to be electrically connected to the ground wiring on a wiring board on which the ground wiring is formed. Wiring board.