JP2005305729A - Method for producing flexible metal-clad laminate improved in productivity and flexible metal-clad laminate obtained by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a flexible metal-clad laminate excellent in adhesive properties and productivity and the flexible metal-clad laminate. <P>SOLUTION: In the method for producing the flexible metal-clad laminate, an adhesive film with an adhesive layer containing a thermoplastic polyimide formed on at least one side and metal foil are laminated by a hot-roll lamination device having at least one pair of metal rolls. The lamination is carried out while a protective film of a polyimide film at least 0.3 W/m×K in heat conductivity is arranged between the heating roll of the device and a material to be laminated. The protective film is peeled off from the laminate after cooling. The flexible metal-clad laminate obtained by the method is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a flexible metal-clad laminate obtained by bonding an adhesive film provided with an adhesive layer containing a thermoplastic polyimide on at least one side and a metal foil by a hot roll laminating apparatus having a pair of metal rolls, And a manufacturing method thereof.

  In recent years, the demand for various printed circuit boards has increased along with the reduction in weight, size and density of electronic products. In particular, the demand for flexible laminates (also referred to as flexible printed circuit boards (FPCs), etc.) has increased. ing. The flexible laminate has a structure in which a circuit made of a metal foil is formed on an insulating film.

  The flexible laminate is generally formed of various insulating materials, and a flexible insulating film is used as a substrate, and a metal foil is bonded to the surface of the substrate by heating and pressure bonding via various adhesive materials. Manufactured by. A polyimide film or the like is preferably used as the insulating film. As the adhesive material, a thermosetting adhesive such as epoxy or acrylic is generally used (FPC using these thermosetting adhesives is hereinafter also referred to as three-layer FPC).

  Thermosetting adhesives have the advantage that they can be bonded at relatively low temperatures. However, in the future, as required characteristics such as heat resistance, flexibility, and electrical reliability become stricter, it is considered that it is difficult to cope with a three-layer FPC using a thermosetting adhesive. On the other hand, an FPC (hereinafter also referred to as a two-layer FPC) in which a metal layer is directly provided on an insulating film or a thermoplastic polyimide is used for an adhesive layer has been proposed. This two-layer FPC has characteristics superior to those of the three-layer FPC, and demand is expected to increase in the future.

  As a method for producing a flexible metal-clad laminate for use in a two-layer FPC, a polyamic acid, which is a polyimide precursor, is cast on a metal foil, applied, and then casted directly onto a polyimide film by sputtering or plating. Examples thereof include a metallizing method for providing a metal layer and a laminating method for bonding a polyimide film and a metal foil through a thermoplastic polyimide. Among these, the lamination method is superior in that the thickness range of the metal foil that can be handled is wider than that of the casting method and the apparatus cost is lower than that of the metalizing method. As a device for laminating, a hot roll laminating device or a double belt press device for continuously laminating a roll-shaped material is used. Of these, the hot roll laminating method can be used more preferably from the viewpoint of productivity.

  When a conventional three-layer FPC was produced by a laminating method, a thermosetting resin was used for the adhesive layer, so that the laminating temperature was less than 200 ° C. and it was possible to perform using a rubber roll (see Patent Document 1). .

  On the other hand, since the two-layer FPC uses thermoplastic polyimide as an adhesive layer, it is necessary to apply a high temperature of 200 ° C. or higher, and in some cases, close to 400 ° C., in order to develop heat-fusibility. Therefore, rubber rolls are difficult to use from the viewpoint of heat resistance, and metal rolls must be used, but metal rolls do not have a buffering action like rubber rolls, and pressure may be applied unevenly to the material. is there. Therefore, there is a problem that it is difficult to obtain a stable adhesive strength. Then, the method of expressing a buffer effect and solving this problem by using a polyimide film as a protective film has been proposed (see Patent Document 2). A normal plastic film cannot withstand a processing temperature close to 400 ° C., but a polyimide film is excellent in heat resistance, so that it can be used without problems even at a high temperature laminate.

However, in general, plastic films have low thermal conductivity, and polyimide films are no exception. Therefore, if the laminating speed is increased in order to improve productivity, the heat of the heating roll is not sufficiently transmitted to the laminated material such as metal foil and adhesive film, and there arises a problem that the adhesive strength of the obtained laminated plate is lowered. was there. Although the above problem can be solved by making the protective film thinner, there is a problem that the buffering effect is not sufficiently exhibited if the protective film is made too thin.
JP-A-9-199830 JP 2001-129918 A

  This invention is made | formed in view of said subject, The objective is to provide the flexible metal-clad laminated board excellent in adhesiveness and productivity, and its manufacturing method.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have used a protective film having a thermal conductivity equal to or higher than a specific value, so that the heat of the heating roll can be laminated through the protective film in a short time. It has been found that the lamination speed can be improved and the present invention has been completed.

  That is, the first of the present invention is a flexible metal-clad laminate in which an adhesive film provided with an adhesive layer containing a thermoplastic polyimide on at least one surface and a metal foil are bonded together by a hot roll laminating apparatus having a pair of metal rolls. A method for producing a laminated board, comprising: laminating a protective film made of a polyimide film having a thermal conductivity of 0.3 W / m · K or more between a heating roll of the apparatus and a material to be laminated; The present invention relates to a method for producing a flexible metal-clad laminate, wherein the protective film is peeled off from the laminate after cooling.

  In a preferred embodiment, a polyimide film in which at least one additive selected from the group consisting of thermally conductive inorganic particles, carbon black, synthetic clay minerals, synthetic mica, and glass beads is dispersed and contained is used as a protective film. The present invention relates to the above manufacturing method.

  A further preferred embodiment relates to the above production method, characterized in that a non-thermoplastic polyimide or a thermoplastic polyimide having a glass transition temperature (Tg) higher by 50 ° C. or more than the lamination temperature is used as the protective film.

  2nd of this invention is related with the flexible metal tension laminated board obtained by the manufacturing method in any one of the said.

  The production method of the present invention provides a high-temperature laminating means excellent in productivity, and can efficiently produce a flexible metal-clad laminate excellent in adhesiveness.

  One embodiment of the present invention will be described below.

  The flexible metal-clad laminate according to the present invention is obtained by the production method according to the present invention, which will be described in detail later. An adhesive film and a metal foil provided with an adhesive layer containing a thermoplastic polyimide on at least one surface. If it is a laminated body containing the structure where is laminated | stacked, it will not specifically limit.

  The adhesive film used for the production of the flexible metal-clad laminate according to the present invention is generally obtained by providing an adhesive layer containing thermoplastic polyimide on a film serving as a base material (only the adhesive layer) In the case of using an adhesive film consisting of the above, it is usually used by peeling it from the base material). When using an adhesive film having a base material and an adhesive layer, the film serving as the base material may be a substrate that can withstand the heating temperature of the heat laminating step and has flexibility and flexibility. However, since the flexible laminated board concerning this invention can be used suitably for an electronic / electric equipment use (a part is also included), it is very preferable to have insulation. As an insulating film (referred to as an insulating film), generally, various resin films can be suitably used and are not particularly limited, but can exhibit excellent heat resistance. Further, a polyimide film excellent in other physical properties is preferably used.

  The polyimide film used in the present invention is generally produced using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid. Usually, the polyamic acid obtained by dissolving a substantially equimolar amount of an aromatic dianhydride and an aromatic diamine in an organic solvent is obtained. The organic solvent solution is produced by stirring under controlled temperature conditions until the polymerization of the acid dianhydride and the diamine is completed. These polyamic acid solutions are usually obtained at a concentration of 5 to 35 wt%, preferably 10 to 30 wt%. When the concentration is in this range, an appropriate molecular weight and solution viscosity are obtained.

As the polymerization method, any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of polyamic acid is the order of addition of the monomers, and the physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any method of adding monomers may be used for the polymerization of polyamic acid. The following method is mentioned as a typical polymerization method. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent and this is reacted with a substantially equimolar amount of an aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Then, the method of superposing | polymerizing using an aromatic diamine compound so that an aromatic tetracarboxylic dianhydride and an aromatic diamine compound may become substantially equimolar in all the processes.
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize.
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar.
5) A method of polymerizing by reacting a substantially equimolar mixture of aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent.
And so on. These methods may be used singly or in combination.

In the present invention, polyamic acid obtained by any polymerization method as described above may be used, and the polymerization method is not particularly limited.
In the present invention, it is also preferable to use a polymerization method in which a prepolymer is obtained using a diamine component having a rigid structure typified by paraphenylenediamine or substituted benzidine. By using this method, a polyimide film having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained. The molar ratio of the diamine having a rigid structure and the acid dianhydride used in preparing the prepolymer in the present method is 100: 70 to 100: 99 or 70: 100 to 99: 100, and further 100: 75 to 100: 90 or 75: 100-90: 100 is preferable. When this ratio is less than the above range, it is difficult to obtain the effect of improving the elastic modulus and the hygroscopic expansion coefficient, and when it exceeds the above range, there are cases where the linear expansion coefficient becomes too small or the tensile elongation becomes small.
Here, the material used for the polyamic acid composition concerning this invention is demonstrated.

  Suitable acid dianhydrides that can be used in the present invention are pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetra Carboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride , Bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) Ethane dianhydride, bi (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, including p-phenylenebis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and the like, these Can be preferably used alone or in any desired mixture. Among these acid dianhydrides, especially pyromellitic dianhydride and / or 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and It is preferable to use 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride.

  Among these acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and / or 3,3 ′, 4,4 The preferred amount of '-biphenyltetracarboxylic dianhydride is 60 mol% or less, preferably 55 mol% or less, more preferably 50 mol% or less, based on the total acid dianhydride. 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and / or 4,4′-oxyphthalic dianhydride and / or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride If the amount of use exceeds this range, the glass transition temperature of the polyimide film becomes too low, or the storage elastic modulus at the time of heating becomes too low and the film formation itself becomes difficult, which is not preferable.

  Moreover, when using pyromellitic dianhydride, the preferable usage-amount is 40-100 mol%, More preferably, it is 45-100 mol%, Most preferably, it is 50-100 mol%. By using pyromellitic dianhydride in this range, the glass transition temperature and the storage elastic modulus at the time of heating can be easily maintained in a range suitable for use or film formation.

  Suitable diamines that can be used in the polyimide precursor polyamic acid composition according to the present invention include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 3, 3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 4, 4'-diaminodiphenyl sulfone, 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenyl Tylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1, 2-diaminobenzene, bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4 '-Bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diamy Benzophenone and their analogs thereof.

  If these diamines are classified into so-called rigid diamines such as diaminobenzenes and benzidines and diamines having flexible structures such as ether groups, sulfone groups, ketone groups and sulfide groups, rigid structures and flexible diamines are considered. The use ratio of the structural diamine is 80/20 to 20/80, preferably 70/30 to 30/70, particularly preferably 60/40 to 30/70, in molar ratio. If the use ratio of the rigid diamine exceeds the above range, the tensile elongation of the resulting film tends to be small, and if it falls below this range, the glass transition temperature becomes too low or the storage modulus during heat decreases. This is not preferable because it may cause adverse effects such as difficulty in film formation.

  The polyimide film used in the present invention is obtained by appropriately determining the type and blending ratio of the aromatic dianhydride and aromatic diamine so as to be a film having desired characteristics within the above range. Can do.

As the preferred solvent for synthesizing the polyamic acid, any solvent can be used as long as it dissolves the polyamic acid. However, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N- Examples thereof include methyl-2-pyrrolidone, and N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.
In addition, a filler can be added for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

The particle size of the filler is not particularly limited because it is determined by the film characteristics to be modified and the kind of filler to be added, but generally the average particle size is 0.05 to 100 μm, preferably 0.1. It is -75 micrometers, More preferably, it is 0.1-50 micrometers, Most preferably, it is 0.1-25 micrometers. If the particle size is below this range, the modification effect is less likely to appear. If the particle size is above this range, the surface properties may be greatly impaired or the mechanical properties may be greatly deteriorated. Further, the number of added parts of the filler is not particularly limited because it is determined by the film properties to be modified, the filler particle diameter, and the like. Generally, the addition amount of the filler is 0.01 to 100 parts by weight, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight with respect to 100 parts by weight of the polyimide. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired. Addition of filler
1. 1. A method of adding to a polymerization reaction solution before or during polymerization 2. A method of kneading fillers using three rolls after completion of polymerization. A method of preparing a dispersion containing a filler and mixing it with a polyamic acid organic solvent solution.

  Any method may be used, but a method of mixing a dispersion containing a filler with a polyamic acid solution, particularly a method of mixing just before film formation, is preferable because contamination by the filler in the production line is minimized. When preparing a dispersion containing a filler, it is preferable to use the same solvent as the polymerization solvent for the polyamic acid. Further, in order to disperse the filler satisfactorily and stabilize the dispersion state, a dispersant, a thickener and the like can be used within a range not affecting the film physical properties.

  A conventionally well-known method can be used about the method of manufacturing a polyimide film from these polyamic acid solutions. This method includes a thermal imidization method and a chemical imidization method, and either method may be used to produce a film, but the imidization by the chemical imidation method is more preferably used in the present invention. It tends to be easy to obtain a polyimide film having various characteristics.

In addition, the production process of the polyimide film particularly preferable in the present invention is as follows.
a) a step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution;
b) casting a film-forming dope containing the polyamic acid solution on a support;
c) a step of peeling the gel film from the support after heating on the support;
d) further heating to imidize and dry the remaining amic acid,
It is preferable to contain.

  In the above step, a curing agent containing a dehydrating agent typified by an acid anhydride such as acetic anhydride and an imidation catalyst typified by a tertiary amine such as isoquinoline, β-picoline or pyridine may be used. .

In the following, a preferred embodiment of the present invention, the chemical imide method, is taken as an example to describe the process for producing a polyimide film. However, the present invention is not limited to the following examples. The film forming conditions and heating conditions can vary depending on the type of polyamic acid, the thickness of the film, and the like.
A film forming dope is obtained by mixing a dehydrating agent and an imidization catalyst in a polyamic acid solution at a low temperature. Subsequently, this film-forming dope is cast into a film on a support such as a glass plate, an aluminum foil, an endless stainless steel belt, or a stainless drum, and the temperature on the support is 80 ° C. to 200 ° C., preferably 100 ° C. to 180 ° C. By heating in the region, the dehydrating agent and imidization catalyst are activated to partially cure and / or dry, and then peel from the support to obtain a polyamic acid film (hereinafter referred to as gel film).

The gel film is in the intermediate stage of curing from polyamic acid to polyimide, has self-supporting properties, and has the formula (1)
(AB) × 100 / B (1)
In formula (1), A and B represent the following.
A: Weight of gel film B: The volatile content calculated from the weight after heating the gel film at 450 ° C. for 20 minutes is in the range of 5 to 500% by weight, preferably 5 to 200% by weight, more preferably 5 to 5%. It is in the range of 150% by weight. It is preferable to use a film in this range, and problems such as film breakage, uneven film color due to drying unevenness, and characteristic variations may occur during the baking process.

  The preferable amount of the dehydrating agent is 0.5 to 5 mol, preferably 1.0 to 4 mol, relative to 1 mol of the amic acid unit in the polyamic acid. Moreover, the preferable quantity of an imidation catalyst is 0.05-3 mol with respect to 1 mol of amic acid units in a polyamic acid, Preferably it is 0.2-2 mol.

  If the dehydrating agent and the imidization catalyst are below the above ranges, chemical imidization may be insufficient, and may break during firing or mechanical strength may decrease. Moreover, when these amounts exceed the above range, the progress of imidization becomes too fast, and it may be difficult to cast into a film, which is not preferable.

  The end of the gel film is fixed to avoid shrinkage during curing, water, residual solvent, residual conversion agent and catalyst are removed, and the remaining amic acid is completely imidized to obtain the present invention. A polyimide film is obtained.

  At this time, it is preferable to finally heat at a temperature of 400 to 650 ° C. for 5 to 400 seconds. Above this temperature and / or for a long time, the film may suffer from thermal degradation and may cause problems. Conversely, if the temperature is lower than this temperature and / or the time is shorter, the predetermined effect may not be exhibited.

  Moreover, in order to relieve the internal stress remaining in the film, heat treatment can be performed under the minimum tension necessary for transporting the film. This heat treatment may be performed in the film manufacturing process, or may be provided separately. The heating conditions vary depending on the characteristics of the film and the apparatus used, and therefore cannot be determined in general. The internal stress can be relaxed by heat treatment at a temperature of 450 ° C. or lower for 1 to 300 seconds, preferably 2 to 250 seconds, particularly preferably 5 to 200 seconds.

Control of various properties of the polyimide film can be appropriately controlled according to the type of monomer used, the order of addition of the monomers during polymerization, the imidization method to be selected, etc., but in the present invention, the molecular design generally has the following properties. It is preferable to do.
1. The tensile elastic modulus is 4.0 GPa or more, preferably 4.5 GPa or more, particularly preferably 5. 0 GPa or more 2. Hygroscopic expansion coefficient is 14 ppm or less, preferably 12 ppm or less. The linear expansion coefficient is 1-20 ppm, preferably 5-18 ppm
In the present invention, a commercially available polyimide film may be used, and examples thereof include apical (manufactured by Kaneka Chemical Co., Ltd.), kapton (manufactured by DuPont), and upilex (manufactured by Ube Industries). Of these, Apical HP (manufactured by Kaneka Chemical Co., Ltd.) can be preferably used from the viewpoint of elastic modulus, linear expansion coefficient, and water absorption.

  As the thermoplastic polyimide contained in the adhesive layer, thermoplastic polyimide, thermoplastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide and the like can be suitably used. Among these, thermoplastic polyesterimide is particularly preferably used from the viewpoint of low moisture absorption characteristics.

  In view of the fact that lamination with an existing apparatus is possible and the heat resistance of the resulting metal-clad laminate is not impaired, the thermoplastic polyimide in the present invention has a glass transition temperature (150 to 300 ° C.). Tg) is preferred. In addition, Tg can be calculated | required from the value of the inflexion point of the storage elastic modulus measured with the dynamic viscoelasticity measuring apparatus (DMA).

  The polyamic acid that is a precursor of the thermoplastic polyimide used in the present invention is not particularly limited, and any known polyamic acid can be used. Also for the production, known raw materials and reaction conditions can be used. Moreover, you may add an inorganic or organic filler as needed.

  The adhesive film used for the production of the flexible metal-clad laminate according to the present invention can be obtained by providing an adhesive layer containing thermoplastic polyimide on at least one surface of the base film. As a method for producing the adhesive film, a method of forming an adhesive layer on the base film, or a method of separately forming the adhesive layer into a sheet and bonding it to the base film can be suitably exemplified. Among these, when taking the former method, if the polyamic acid that is the precursor of the thermoplastic polyimide contained in the adhesive layer is completely imidized, the solubility in an organic solvent may decrease, It may be difficult to provide the adhesive layer on the base film. Therefore, from the above viewpoint, it is more preferable to prepare a solution containing polyamic acid which is a precursor of thermoplastic polyimide, apply this to a base film, and then imidize. As the imidization method at this time, either a thermal cure method or a chemical cure method can be used, but the chemical cure method sets a heating condition for removing a chemical conversion agent and the like without thermally deteriorating the adhesive layer. It is more preferable to imidize by a thermal curing method because it may be necessary.

  On the other hand, when the thermoplastic polyimide has good solubility in an organic solvent, after the polyamic acid is completely imidized to obtain a polyimide, a solution obtained by dissolving the polyimide in an appropriate organic solvent is used as the base film. You may apply to.

  In addition, the polyamic acid solution may contain other materials such as a filler, depending on the application.

  Moreover, what is necessary is just to adjust suitably about the thickness structure of each layer of an adhesive film so that it may become the total thickness according to a use. Furthermore, if necessary, various surface treatments such as corona treatment, plasma treatment, and coupling treatment may be applied to the core film surface before providing the adhesive layer.

  The flexible metal-clad laminate according to the present invention is obtained by bonding a metal foil to the adhesive film. The metal foil to be used is not particularly limited, but when the flexible metal-clad laminate of the present invention is used for electronic equipment / electric equipment, for example, copper or copper alloy, stainless steel or its alloy, nickel Alternatively, a foil made of a nickel alloy (including 42 alloy), aluminum, or an aluminum alloy can be used. In general flexible metal-clad laminates, copper foil such as rolled copper foil and electrolytic copper foil is frequently used, but it can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil.

  In the present invention, the thickness of the metal foil is not particularly limited, and may be any thickness as long as a sufficient function can be exhibited depending on the application.

  In order to obtain the flexible metal-clad laminate according to the present invention by laminating the adhesive film and the metal foil, a hot roll laminating apparatus having a pair of metal rolls is used. Other examples of the heating and pressing apparatus include a double belt press (DBP), but a hot roll laminating apparatus having a pair of metal rolls is simple because the apparatus configuration is simple and the maintenance cost is advantageous. Is preferably used. The “hot roll laminating apparatus having a pair of metal rolls” as used herein refers to an apparatus having at least a pair of metal rolls for heating and pressing a material.

  When carrying out the thermal lamination, a protective film is placed between the pressure surface and the metal foil in order to improve the appearance of the resulting laminate. The protective film needs to be a material that can withstand the heating temperature in the heat laminating process, and includes heat-resistant plastics such as polyimide films, metal foils such as copper foil, aluminum foil, and SUS foil. It is preferable to use a non-thermoplastic polyimide film or a thermoplastic polyimide having a high glass transition temperature from the viewpoint of excellent balance of properties and reuse. When using a thermoplastic polyimide for the protective film, a thermoplastic polyimide having a glass transition temperature higher by 50 ° C. or more than the lamination temperature is used. When the glass transition temperature is lower than the above value, there is a possibility of sticking to a roll or metal foil during lamination. In addition, if the thickness is thin, the function of buffering and protecting at the time of lamination will not be sufficiently fulfilled, so the thickness of the non-thermoplastic polyimide film is preferably 75 μm or more.

  The protective film used for the laminate of the present invention exhibits not only the effect of protecting the surface of the metal foil but also the effect of buffering fine irregularities on the surface of the metal roll. However, in general, plastic films have low thermal conductivity, and polyimide films are no exception. Although it depends on the structure, the thermal conductivity of a general polyimide film is less than 0.2 W / m · K. Therefore, in the case of a high temperature laminate using thermoplastic polyimide as an adhesive layer as in the present application, the lamination is performed without sufficiently transferring the heat of the heating roll to the material, and as a result, the adhesive strength between the metal foil and the adhesive film is insufficient. It may become. In particular, when the laminating speed is increased in order to improve productivity, this problem becomes remarkable. Although some improvement is possible by reducing the thickness of the protective film, as described above, if the thickness of the protective film is thin, the protective film does not sufficiently function as a buffer.

  In the present invention, by using a polyimide film having a thermal conductivity of 0.3 W / m · K or more, the above-mentioned problems can be solved, and even if a thick protective film is used, a flexible metal-clad laminate with good productivity. A board can be manufactured. It is more preferable that the thermal conductivity is 0.4 W / m · K or more because productivity can be further improved.

  The thermal conductivity of the film depends on the thickness, and tends to decrease as the film thickness increases. For this reason, a polyimide film having a thermal conductivity of 0.3 W / m · K or more at the thickness used in the laminate is appropriately selected and used.

  Regarding means for obtaining a protective film made of a polyimide film having a thermal conductivity of 0.3 W / m · K or more, which is used in the production method of the present invention, in the polyimide film, thermally conductive inorganic particles, carbon black, synthetic It is preferably formed by dispersing and containing at least one additive selected from the group consisting of clay minerals, synthetic mica, and glass beads. More specifically, a method of depositing a thin film of a metal having high thermal conductivity such as aluminum on the surface of the polyimide film, a solution containing a thermal conductive inorganic filler is applied on the surface of the polyimide film, and the thermal conductivity is high. Examples thereof include a method for forming a layer, a method for sandwiching and integrating a metal foil with a polyimide adhesive film, and a method for dispersing an additive for improving thermal conductivity in the film. Among these, taking into consideration the influence on the thermal behavior of the protective film, durability under high temperature conditions, reusability, aggressiveness to the surface of the heated roll, etc., a method of dispersing the additive in the film is adopted. Is preferred. Examples of the additive include thermally conductive inorganic particles, carbon black, synthetic clay mineral, synthetic mica, and glass beads. These additives will be described below.

  Examples of the thermally conductive inorganic filler include silica, alumina, aluminum borate, tungsten carbide, silicon nitride, boron nitride, aluminum nitride, potassium titanate, and calcium carbonate. These inorganic fillers have various shapes such as particles, flakes, and needles depending on the type.

  When the inorganic filler is in the form of particles, a particle size of 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less is used. When the inorganic filler is larger than 10 μm, local aggregation of the filler due to poor dispersion is not preferable because it affects the surface smoothness of the protective film. If the particle size is 10 μm or less, it is preferable that the surface smoothness is hardly deteriorated even if there is some aggregation.

  When the inorganic filler is in the form of needles or flakes, those having a minor axis diameter of 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less are used. When it is larger than 5 μm, it is not preferable because it affects the surface smoothness of the protective film in the same manner as the particulate filler. If the minor axis diameter is 5 μm or less, it is preferable that the surface smoothness is hardly deteriorated even if there is some aggregation.

  The blending amount of the inorganic filler with respect to the polyimide film is appropriately adjusted according to the thermal conductivity of the filler itself and the thermal conductivity of the obtained polyimide film, but is preferably 30 to 250 parts by weight with respect to 100 parts by weight of the polyimide resin. 50 to 200 parts by weight is more preferable, and 50 to 180 parts by weight is particularly preferable. If the blending amount of the filler is more than the above range, the resulting polyimide film becomes fragile, which may hinder use as a protective film. On the other hand, when the amount is less than the above range, the effect of improving the thermal conductivity is small, and it is difficult to obtain a polyimide film having the desired thermal conductivity.

  Synthetic clay minerals are swellable or non-swellable, and swellable synthetic clay minerals are those that swell in water (hydrophilic) and those that swell in organic solvents (lipophilic). Among these, a swellable synthetic clay mineral is preferable because of its excellent dispersibility, and among them, an oleophilic synthetic clay mineral is preferable because an organic solvent is used in the production process of polyimide. Moreover, since it influences the surface smoothness of a polyimide film like an inorganic filler, it is preferable to use a particle diameter of 0.005-20 micrometers, More preferably, 0.01-5 micrometers, Especially preferably, it is 0.00. A thing of 01-1 micrometer is used.

  Synthetic mica is also hydrophilic and oleophilic, similar to synthetic clay minerals. For the same reason, oleophilic ones are preferred. Further, the particle system is preferably 0.005 to 20 μm, more preferably 0.01 to 5 μm, and particularly preferably 0.01 to 1 μm. It is preferable to use glass beads having a similar particle size range.

  The blending amount of these synthetic clay minerals, synthetic mica, and glass beads with respect to the polyimide film is appropriately adjusted depending on the thermal conductivity of the additive itself and the thermal conductivity of the polyimide film to be obtained. The amount is preferably 50 parts by weight, more preferably 5 to 40 parts by weight, and particularly preferably 5 to 25 parts by weight. If the blending amount of the filler is more than the above range, the resulting polyimide film becomes fragile, which may hinder use as a protective film. On the other hand, when the amount is less than the above range, the effect of improving the thermal conductivity is small, and it is difficult to obtain a polyimide film having the desired thermal conductivity.

  As a method of dispersing and containing the inorganic filler, synthetic clay mineral, synthetic mica, and glass beads in the polyimide film, the additive is dispersed in the polyamic acid which is a polyimide precursor, and then this mixed solution is used. Examples of the method include film formation and imidization. Examples of the addition method to the polyamic acid include a method of adding the additive as a solid, and a method of dispersing the additive in a suitable solvent and then adding this solution to the polyamido acid. In order to prevent this, it is preferable to adopt the latter method. Film formation and imidization can be performed according to the above-described procedure. Moreover, in order to improve the dispersibility of the said additive, you may mix | blend various dispersing agents.

  The heating method of the material to be laminated in the heat laminating means of the present invention is not particularly limited, and a conventionally known method that can be heated at a predetermined temperature such as a heat circulation method, a hot air heating method, an induction heating method, etc. is adopted. The heating means can be used. Similarly, the pressurization method of the material to be laminated in the heat laminating means is not particularly limited, and a conventionally known method capable of applying a predetermined pressure such as a hydraulic method, a pneumatic method, a gap pressure method, etc. The pressurizing means adopting can be used.

  The heating temperature in the thermal laminating step, that is, the laminating temperature, is preferably a glass transition temperature (Tg) of the adhesive film + 50 ° C. or higher, and more preferably Tg + 100 ° C. or higher of the adhesive film. If it is Tg + 50 degreeC or more temperature, an adhesive film and metal foil can be heat-laminated favorably. Moreover, if it is Tg + 100 degreeC or more, the lamination speed | rate can be raised and the productivity can be improved more.

  The laminating speed in the thermal laminating step is preferably 1.5 m / min or more, and more preferably 2.0 m / min or more. If it is 1.5 m / min or more, sufficient thermal lamination is possible, and if it is 2.0 m / min or more, productivity can be further improved. Since the polyimide film used as the protective film in the present invention has high thermal conductivity, the laminating speed can be improved as compared with the case of using a normal polyimide film. However, if the laminating speed is increased too much, the protective film used in the present invention may not be able to transfer heat sufficiently. In that case, it is preferable to perform preliminary heating in contact with a part of the heating roll.

  The higher the pressure in the heat laminating step, that is, the laminating pressure, is advantageous in that the laminating temperature can be lowered and the laminating speed can be increased. There is a tendency to get worse. On the other hand, if the lamination pressure is too low, the adhesive strength of the metal foil of the laminate obtained is lowered. Therefore, the lamination pressure is preferably in the range of 49 to 490 N / cm (5 to 50 kgf / cm), and more preferably in the range of 98 to 294 N / cm (10 to 30 kgf / cm). Within this range, the three conditions of the lamination temperature, the lamination speed and the lamination pressure can be made favorable, and the productivity can be further improved.

  The tension of the metal foil during lamination is preferably 0.1 to 200 N / cm, more preferably 1 to 100 N / cm, and particularly preferably 5 to 50 N / cm. If the tension is below this range, sagging may occur during transportation, which may make it difficult to obtain a flexible metal-clad laminate with good appearance. Since the influence of the tension is increased, vertical flaws are generated in the metal foil along the laminating direction, and it may be difficult to uniformly press the adhesive with the adhesive film.

  The adhesive film tension during lamination is preferably 0.01 to 2 N / cm, more preferably 0.02 to 1.5 N / cm, and particularly preferably 0.05 to 1.0 N / cm. If the tension is below this range, sagging may occur during transportation, which may make it difficult to obtain a flexible metal-clad laminate with good appearance. Lamination is performed in a state of being pulled strongly to the surface, causing vertical wrinkles, which may make it difficult to uniformly press the metal foil.

  In order to obtain the flexible metal-clad laminate according to the present invention, it is preferable to use a thermal laminating apparatus that continuously press-bonds the material to be laminated while heating, but in this thermal laminating apparatus, before the thermal laminating means, A laminated material feeding means for feeding the laminated material may be provided, or a laminated material winding means for winding the laminated material may be provided after the thermal laminating means. By providing these means, the productivity of the thermal laminating apparatus can be further improved. The specific configuration of the laminated material feeding means and the laminated material winding means is not particularly limited, and for example, an adhesive film, a metal foil, or a known roll shape capable of winding up the obtained laminated plate A winder etc. can be mentioned.

  Furthermore, it is more preferable to provide a protective film winding means or a protective film feeding means for winding or feeding the protective film. If these protective film winding means and protective film feeding means are provided, the protective film can be reused by winding the protective film once used in the heat laminating step and installing it again on the feeding side. . Moreover, when winding up a protective film, in order to align the both ends of a protective film, you may provide an edge part position detection means and a winding position correction means. Thereby, since the edge part of a protective film can be aligned and wound accurately, the efficiency of reuse can be improved. The specific configurations of the protective film winding means, the protective film feeding means, the end position detecting means, and the winding position correcting means are not particularly limited, and various conventionally known devices can be used.

  As described above, the flexible metal-clad laminate obtained by the manufacturing method according to the present invention can be mounted with various miniaturized and high-density components by forming a desired pattern wiring by etching the metal foil. It can be used as a flexible wiring board. Of course, the application of the present invention is not limited to this, and it goes without saying that it can be used for various applications as long as it is a laminate including a metal foil.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

  In addition, the evaluation methods of the thermal conductivity of the polyimide film, the glass transition temperature of the adhesive film, and the metal foil peel strength in the synthesis examples, examples, and comparative examples are as follows.

(Thermal conductivity)
The thermal conductivity is TC-7000 manufactured by Vacuum Riko Co., Ltd. as a measuring device, and the thermal conductivity in the film thickness direction is measured by a laser flash method in a vacuum (pressure: about 1 × 10 ⁻² Torr) at 25 ° C. evaluated.

(Glass-transition temperature)
The glass transition temperature was measured with a DMS200 manufactured by Seiko Instruments Inc. at a temperature rising rate of 3 ° C./min in a temperature range from room temperature to 400 ° C., and the inflection point of the storage elastic modulus was taken as the glass transition temperature.

(Stripping strength of metal foil: Adhesive strength)
A sample was prepared according to “6.5 Peel Strength” of JIS C6471, and a 5 mm wide metal foil part was peeled off at a peeling angle of 180 degrees and 50 mm / min, and the load was measured.

(Synthesis Example 1: Synthesis of polyimide film used for protective film)
After dissolving 25.8 kg of 4,4′-diaminodiphenyl ether (hereinafter, also referred to as ODA) in 236 kg of N, N-dimethylformamide (hereinafter also referred to as DMF) cooled to 10 ° C., pyromellitic dianhydride (hereinafter, referred to as “DM”). 27.4 kg) was added and stirred for 1 hour to dissolve.
A separately prepared DMF solution of PMDA (PMDA: DMF = 0.90 kg: 10.2 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 3000 poise. Stirring was conducted for 1 hour to obtain a polyamic acid solution having a solid content concentration of 18% by weight and a rotational viscosity at 23 ° C. of 3400 poise.

  On the other hand, a solution obtained by adding boron nitride (UHP-S1, manufactured by Showa Denko KK) to DMF was dispersed with a homogenizer to prepare a boron nitride dispersion (solid content concentration: 18% by weight). 70 parts by weight of this boron nitride dispersion was added to 100 parts by weight of the polyamic acid solution and stirred.

  A curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 4.0 / 1.0 / 4.0) was added to the polyamic acid solution at a weight ratio of 25% with respect to the polyamic acid solution, and the mixture was continuously mixed. And then extruded from a T die and cast onto a stainless steel endless belt running 20 mm below the die. This resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt (volatile content 30% by weight) and fixed to the tenter clip, 300 ° C. × 50 seconds, 400 ° C. × 50 The film was dried and imidized at 500 ° C. for 50 seconds to obtain a 75 μm thick polyimide film.

(Synthesis Example 2: Synthesis of polyimide film used for protective film)
A solution obtained by adding synthetic clay mineral (lipophilic smectite (STN), manufactured by Co-op Chemical Co., Ltd.) to DMF was dispersed with a homogenizer to prepare a smectite dispersion (solid content concentration: 18% by weight). A 75 μm-thick polyimide film was obtained in the same manner as in Synthesis Example 1 except that 20 parts by weight of this smectite dispersion was added to 100 parts by weight of the polyamic acid solution instead of the boron nitride dispersion.

(Synthesis Example 3: Synthesis of polyimide film used for protective film)
A solution obtained by adding synthetic mica (Somasif (ME-100), manufactured by Co-op Chemical Co., Ltd.) to DMF was dispersed with a homogenizer to prepare a synthetic mica dispersion (solid content concentration: 18% by weight). A 75 μm-thick polyimide film was obtained in the same manner as in Synthesis Example 1 except that 20 parts by weight of this synthetic mica dispersion was added to 100 parts by weight of the polyamic acid solution instead of the boron nitride dispersion.

(Synthesis Example 4: Synthesis of polyimide film used for protective film)
A solution in which glass beads (Toshiba glass beads (MB-10), manufactured by Toshiba Barotini Co., Ltd.) were added to DMF was dispersed with a homogenizer to prepare a glass bead dispersion (solid content concentration: 18% by weight). A 75 μm-thick polyimide film was obtained in the same manner as in Synthesis Example 1 except that 20 parts by weight of this glass bead dispersion was added to 100 parts by weight of the polyamic acid solution instead of the boron nitride dispersion.

(Synthesis Example 5: Synthesis of polyimide film used for protective film)
Except for not adding the boron nitride dispersion, the same operation as in Synthesis Example 1 was performed to obtain a 75 μm-thick polyimide film.

(Synthesis Example 6; synthesis of polyimide film used for protective film)
Except for adding 3 parts by weight of the boron nitride dispersion to 100 parts by weight of the polyamic acid solution, the same operation as in Synthesis Example 1 was performed to obtain a 75 μm thick polyimide film.

(Example 1)
On both sides of a double-sided adhesive film (PIXEO HC-142, Kaneka Chemical Co., Ltd.) whose glass transition temperature of the adhesive layer is 240 ° C., 18 μm thick rolled copper foil (BHY-22B-T, Japan Energy Co., Ltd.) Further, the polyimide film obtained in Synthesis Example 1 is disposed as protective films on the upper and lower sides thereof, the adhesive film tension is 0.4 N / cm, the laminating temperature is 380 ° C., and the laminating pressure is 196 N / cm (20 kgf / cm). Then, heat lamination was continuously performed under the condition of a lamination speed of 2.5 m / min. After lamination, the protective films on both sides were peeled off to obtain a flexible copper clad laminate.

(Example 2)
As a protective film, the same operation as in Example 1 was performed except that the polyimide film obtained in Synthesis Example 2 was used to obtain a flexible copper-clad laminate.

(Example 3)
A flexible copper-clad laminate was obtained by performing the same operation as in Example 1 except that the polyimide film obtained in Synthesis Example 3 was used as the protective film.

Example 4
As a protective film, the same operation as in Example 1 was performed except that the polyimide film obtained in Synthesis Example 4 was used to obtain a flexible copper-clad laminate.

(Comparative Example 1)
As a protective film, the same operation as in Example 1 was performed except that the polyimide film obtained in Synthesis Example 5 was used to obtain a flexible copper-clad laminate.

(Comparative Example 2)
As a protective film, the same operation as in Example 1 was performed except that the polyimide film obtained in Synthesis Example 6 was used to obtain a flexible copper-clad laminate.

  Table 1 shows the results of evaluating the characteristics of the flexible metal-clad laminates obtained in the examples and comparative examples.

As shown in Comparative Examples 1 and 2, when the thermal conductivity of the protective film is less than 0.3 W / m · K, the heat of the roll is not sufficiently transferred to the material at a high lamination speed, and the resulting flexible metal-clad laminate is obtained. The result was that the adhesive strength of the plate was inferior. On the other hand, in Examples 1-4 using a protective film with high thermal conductivity, a flexible metal-clad laminate having sufficient adhesive strength was obtained.

Claims (4)

A method for producing a flexible metal-clad laminate in which an adhesive film provided with an adhesive layer containing a thermoplastic polyimide on at least one side and a metal foil are bonded together by a hot roll laminator having a pair of metal rolls. A protective film made of a polyimide film having a thermal conductivity of 0.3 W / m · K or more is placed between the heating roll of the device and the material to be laminated, and the protective film is laminated from the laminated plate after cooling. A method for producing a flexible metal-clad laminate, characterized by peeling. A polyimide film in which at least one additive selected from the group consisting of thermally conductive inorganic particles, carbon black, synthetic clay minerals, synthetic mica, and glass beads is dispersed and contained is used as a protective film, The method for producing a flexible metal-clad laminate according to claim 1. 3. The flexible metal-clad laminate according to claim 1, wherein a non-thermoplastic polyimide or a thermoplastic polyimide whose glass transition temperature (Tg) is 50 ° C. or more higher than the lamination temperature is used as the protective film. Production method. A flexible metal-clad laminate obtained by the production method according to claim 1.