JP2005193541A - Manufacturing method of flexible metal clad laminated sheet enhanced in dimensional stability and flexible metal clad laminated sheet obtained thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a flexible metal clad laminated sheet excellent in dimensional stability. <P>SOLUTION: In the manufacturing method of the flexible metal clad laminated sheet excellent in dimensional stability obtained by laminating a metal foil on one side or both sides of a polyimide film trough an adhesive layer, a protective film is arranged between a heated and pressed surface and the metal foil to be laminated in a state stretched in an MD direction within an elastic deformation range. By this method, the flexible metal clad laminated sheet excellent in dimensional stability can be manufactured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a flexible metal-clad laminate having excellent dimensional stability, obtained by bonding a metal foil to one or both sides of a polyimide film via an adhesive layer.

  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 could be less than 200 ° C. (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, residual distortion occurs in the flexible metal-clad laminate obtained by laminating, and it appears as a dimensional change when wiring is formed by etching and when solder reflow is performed to mount components.

  In particular, in the laminating method, when an adhesive layer containing a thermoplastic polyimide is provided on a polyimide film, the polyamic acid which is a precursor of the thermoplastic polyimide is cast and applied, and then continuously heated to imidize, Since the heating and pressurization is continuously performed when the metal foil is bonded, the material is often placed in a heating environment under tension. Therefore, different thermal stresses are generated in the MD direction and the TD direction. Specifically, a pulling force acts in the MD direction where tension is applied, and conversely, a shrinking force acts in the TD direction. As a result, when the metal foil is etched from the flexible laminate and when heated through solder reflow, this strain is released, the MD direction contracts, and conversely, the TD direction expands.

In recent years, in order to achieve miniaturization and weight reduction of electronic devices, wiring provided on a substrate has been miniaturized, and components to be mounted are mounted with miniaturization and high density. For this reason, if the dimensional change after forming the fine wiring is increased, there is a problem that the component and the board are not well connected due to deviation from the component mounting position in the design stage.
Therefore, attempts have been made to suppress dimensional changes by controlling the laminating pressure or controlling the tension of the adhesive film (see Patent Document 2 or 3). However, although the dimensional change is improved by these means, it is not sufficient yet, and further improvement of the dimensional change is demanded.
JP-A-9-199830 JP 2002-326308 A JP 2002-326280 A

  The present invention has been made in view of the above-described problems, and its purpose is to provide a flexible metal-clad laminate in which the occurrence of dimensional changes during etching and heating is suppressed, particularly when produced by a laminating method. An object of the present invention is to provide a flexible metal-clad laminate that can suppress the occurrence of changes, and a method for manufacturing the same.

  As a result of intensive studies in view of the above problems, the present inventors have arranged a protective film between the heating and pressing surface and the metal foil, and laminated the protective film in a state of being stretched in the MD direction within the elastic deformation range. Thus, the present inventors have found that the dimensional change rate of the obtained flexible metal-clad laminate can be improved and have completed the present invention.

  That is, the first aspect of the present invention is a method for producing a flexible metal-clad laminate having excellent dimensional stability, obtained by bonding a metal foil to one or both sides of a polyimide film via an adhesive layer. The present invention relates to a method for producing a flexible metal-clad laminate, characterized in that a protective film is disposed between a pressure surface and a metal foil, and the protective film is laminated in a state of being stretched in the MD direction within an elastic deformation range.

  A preferred embodiment is characterized in that the flexible metal-clad laminate is obtained by laminating a metal foil and a polyimide film through an adhesive layer by a hot roll laminator having a pair of metal rolls. Regarding the method.

  A further preferred embodiment relates to the above production method, wherein the protective film tension during thermal lamination is 60 kg / m or more and 200 kg / m or less.

  A further preferred embodiment relates to the above-mentioned production method, wherein the protective film is brought into contact with a hot roll in advance so that the temperature of the protective film is 0 to −10 ° C. with respect to the roll temperature during lamination.

  A further preferred embodiment relates to the above production method, characterized in that the heat laminating temperature is 300 ° C. or higher.

  Further preferred embodiments relate to the above production method, wherein the adhesive layer contains a thermoplastic polyimide.

  A second aspect of the present invention is a flexible metal-clad laminate obtained by any one of the manufacturing methods described above, and a dimensional change rate before and after removing the metal foil, and heat treatment at 250 ° C. for 30 minutes after removing the metal foil. It is related with the flexible metal-clad laminate characterized by the total value of the dimensional change rate before and after performing in the range of -0.08 to +0.08 in both the MD direction and the TD direction.

  In the flexible metal-clad laminate obtained from the production method of the present invention, the occurrence of dimensional change is suppressed, and in particular, the occurrence of dimensional change in the laminating method can be effectively suppressed. Specifically, the dimensional change rate before and after removing the metal foil, and the dimensional change rate before and after performing heat treatment at 250 ° C. for 30 minutes after removing the metal foil can be reduced. Etc., and problems such as misalignment can be improved.

  One embodiment of the present invention will be described below.

  The protective film used in the production method of the present invention may be any film as long as it can withstand the heating temperature in the heat laminating process, and heat resistant plastic such as non-thermoplastic polyimide film, metal such as copper foil, aluminum foil, and SUS foil. Although foil etc. are mentioned, A non-thermoplastic polyimide film may be used suitably from the point which is excellent in balance, such as heat resistance and reusability. 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 polyimide film used as a protective film in the present invention is 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, the polyamic acid obtained by using any of the above polymerization methods may be used, and the polymerization method is not particularly limited.

  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.

  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.

  In the present invention, the polyimide film used as the protective film should be used 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 be obtained.

  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 characteristics of the film such as slidability and thermal conductivity. 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 the completion of polymerization. Any method such as preparing a dispersion containing filler and mixing it with a polyamic acid organic solvent solution may be used, but a method of mixing a dispersion containing filler with a polyamic acid solution, particularly immediately before film formation. This method is preferable because the 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 and dried to avoid shrinkage during curing, water, residual solvent, residual conversion agent and catalyst are removed, and the remaining amic acid is completely imidized to form a polyimide film. can get.

  It is preferable that the polyimide film is finally heated 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 monomers during polymerization, the imidization method to be selected, and the like.

  In the present invention, a commercially available polyimide film may be used as the protective film, and examples include Apical (manufactured by Kaneka Chemical Co., Ltd.), Kapton (manufactured by DuPont), and Upilex (manufactured by Ube Industries).

  In the method for producing a flexible metal-clad laminate according to the present invention, the polyimide film to be bonded to the metal foil via the adhesive layer can use conventionally known raw materials and production methods as well as the polyimide film used for the protective film. It is also possible to use a commercially available polyimide film.

  The adhesive layer used in the present invention may be any of acrylic, epoxy, modified epoxy, phenol, polyamideimide, polyimide, but from the viewpoint of heat resistance, insulation reliability, and laminate processability. It is preferable to use an adhesive layer containing thermoplastic polyimide.

  The thermoplastic polyimide in the present invention has a glass transition temperature and is 10 to 400 ° C. (temperature increase rate: 10) in thermomechanical analysis (TMA) in compression mode (probe diameter 3 mmφ, load 5 g). That which causes permanent compression deformation in the temperature range of ° C / min).

  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 polyamic acid can be used. Regarding the production of the polyamic acid solution, the raw materials and the production conditions can be used in exactly the same manner.

  Various properties can be adjusted by combining various raw materials to be used, but generally the glass transition temperature increases and / or the storage modulus during heat increases as the ratio of rigid structure diamine increases, and adhesion and processing This is not preferable because the property is low. The diamine ratio of the rigid structure is preferably 40 mol% or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

  Further, if necessary, an inorganic or organic filler may be added, and the above method can be used in the same manner as the filler addition method.

  The method for producing a flexible metal-clad laminate in the present invention is characterized in that a metal foil is bonded to one or both sides of a polyimide film via an adhesive layer. As a laminating procedure, after forming an adhesive layer on at least one side of the polyimide film, a method of laminating with the metal foil, forming the adhesive layer into a sheet shape, laminating this on the polyimide film, A method of bonding, a method of forming an adhesive layer in a sheet shape, and bonding between a metal foil and a polyimide film can be suitably exemplified. Of these, when the first method is adopted and the adhesive layer further contains a thermoplastic polyimide, the solubility in organic solvents decreases if the polyamic acid that is the precursor of the thermoplastic polyimide is completely imidized. In some cases, it may be difficult to provide the adhesive layer on the polyimide 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 polyimide film, and then imidize. As the imidization method at this time, either a thermal imidization method or a chemical imidization method can be used, but the chemical imidization method is a heating that removes a chemical conversion agent or the like without thermally deteriorating the adhesive layer. From the point that conditions may have to be set, it is more preferable to imidize by a thermal imidization method.

  The higher the temperature of thermal imidization, the easier the imidization occurs. Therefore, the imidization rate can be increased, which is preferable in terms of productivity. However, if it is too high, the thermoplastic polyimide may cause thermal decomposition. On the other hand, if the temperature of the heat cure is too low, imidization is difficult to proceed, and the time required for the imidization process becomes long. The temperature of the thermal imidization is preferably set within the range of glass transition temperature to glass transition temperature + 200 ° C. of the thermoplastic polyimide, and more preferably set within the range of glass transition temperature + 50 ° C. to glass transition temperature + 150 ° C. preferable. As for the imidization time, it suffices to take a sufficient time for the imidization and drying to be substantially completed, and although it is not uniquely limited, generally it is appropriately set within a range of about 1 to 600 seconds. Is done.

  Further, for the purpose of improving the melt fluidity of the adhesive layer, it is possible to intentionally lower the imidization rate and / or leave the solvent. 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 a contact bonding layer and a polyimide film so that it may become the total thickness according to a use. Further, if necessary, various surface treatments such as corona treatment, plasma treatment, and coupling treatment may be applied to the polyimide film surface before providing the adhesive layer.

  The metal foil used in the present invention 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 Examples include foils made of alloys, nickel, nickel alloys (including 42 alloys), aluminum, or aluminum alloys. 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 that can exhibit a sufficient function depending on the application. It is preferably -35 µm, more preferably 2-25 µm, particularly 3-18 µm. If the thickness of the metal foil is less than this range, connection failure or connection reliability is liable to decrease when mounted on various substrates using an anisotropic conductive film, etc., and if it exceeds the above range, fine wiring is formed. Tend to be difficult. The metal foil can be laminated using a thicker one, and then thinned by a known method such as etching.

  In order to bond the metal foil and the polyimide film through the adhesive layer in the present invention, for example, a hot roll laminating apparatus having a pair of metal rolls or a continuous treatment by a double belt press (DBP) can be used. Among these, it is preferable to use a hot roll laminating apparatus having a pair of metal rolls because the apparatus configuration is simple and advantageous in terms of maintenance cost. The “heat roll laminating apparatus having a pair of metal rolls” herein may be an apparatus having a metal roll for heating and pressurizing a material, and the specific apparatus configuration is particularly limited. It is not a thing.

  The specific configuration of the means for carrying out the thermal lamination is not particularly limited, but a protective material is disposed between the pressing surface and the metal foil in order to improve the appearance of the resulting laminate. It is preferable to do. As described above, as the protective material, a non-thermoplastic polyimide film is more preferably used from the viewpoint of excellent balance between heat resistance and reuse. Further, the protective material does not necessarily have to be a single layer, and may have a multilayer structure of two or more layers having different characteristics.

  In addition, when thermoplastic polyimide is contained in the adhesive layer, the laminating temperature becomes very high. Therefore, when the protective film is used as it is for laminating, the appearance and dimensions of the resulting flexible metal-clad laminate due to rapid thermal expansion. May degrade stability. Therefore, it is preferable to preheat the protective film before lamination. Examples of the preheating means include a method of bringing a protective material into contact with a heat roll. Whichever method is adopted, the temperature of the protective film is set to be within a range of 0 to −10 ° C. with respect to the roll temperature during lamination. By setting the protective film temperature within the above range, since the thermal expansion of the protective material is completed at the time of lamination, it is possible to suppress the influence on the appearance and dimensional change of the flexible metal-clad laminate. When the temperature of the protective film is out of the above range, since the lamination is performed without completing the thermal expansion of the protective material, rapid thermal expansion occurs at the time of lamination, and the appearance and dimensional change of the obtained laminated board may be deteriorated. is there. The distance and time for holding the protective material on the heating roll are not particularly limited, and may be appropriately adjusted from the thickness of the protective film, the diameter of the roll, the lamination speed, and the like.

  The heating method of the material to be laminated in the heat laminating means is not particularly limited. For example, heating using a conventionally known method capable of heating at a predetermined temperature, such as a heat circulation method, a hot air heating method, an induction heating method, or the like. 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. In addition, when the laminating temperature is 300 ° C. or higher, the effect of the present invention appears particularly remarkably, and it becomes possible to produce a flexible metal-clad laminate excellent in dimensional stability.

  The laminating speed in the thermal laminating step is preferably 0.5 m / min or more, and more preferably 1.0 m / min or more. If it is 0.5 m / min or more, sufficient thermal lamination is possible, and if it is 1.0 m / min or more, productivity can be further improved.

  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 polyimide 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, it may be difficult to obtain a flexible metal-clad laminate with good appearance, and if it exceeds this range, the dimensional stability tends to be inferior.

  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 material winding means and a protective material feeding means for winding and feeding the protective material. If these protective material take-up means and protective material feeding means are provided, the protective material can be reused by winding the protective material once used in the thermal laminating step and installing it again on the pay-out side. . Further, when winding up the protective material, end position detecting means and winding position correcting means may be provided in order to align both ends of the protective material. As a result, the end portions of the protective material can be aligned and wound with high accuracy, so that the efficiency of reuse can be increased. The specific configurations of the protective material winding means, the protective material 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.

  Next, a method for improving the dimensional stability of the flexible metal-clad laminate with a protective film will be described.

  At the time of heat laminating, a protective film is disposed between the heat-pressing surface and the metal foil to perform lamination, and after that, after cooling to Tg or less of the adhesive layer, the protective film is peeled off. In the case of heat laminating, since it is laminated in a state where tension is applied in the MD direction of the adhesive film, it is stretched in the MD direction and bonded together. Therefore, shrinkage in the MD direction and expansion strain remain in the TD direction, which are released after the metal foil is removed and heated at 250 ° C. for 30 minutes, and appear as a dimensional change in shrinkage on the base material.

  Further, the protective film protects the surface of the flexible metal-clad laminate and keeps the appearance good, and also affects the dimensional change rate after removing the metal foil and before and after heating at 250 ° C. for 30 minutes. That is, the metal foil is fixed at Tg or less of the adhesive layer after laminating, and at a temperature below that, the metal foil causes plastic deformation due to a difference in dimensional change between the protective film and the metal foil. Therefore, by laminating in a state stretched in the MD direction within the elastic deformation range in advance before thermal lamination, the protective film shrinks after lamination, and the metal foil is plastically deformed in the shrinking direction. After removing the metal foil and at 250 ° C. for 30 minutes. Shrinkage after heating can be alleviated. Although the stretch rate in the MD direction varies depending on the protective film, it is within the elastic deformation range and is 0.05 to 5%, preferably 0.1 to 3%, and more preferably 0.5 to 2%. If it is lower than this range, a sufficient dimensional improvement effect cannot be obtained. On the contrary, if it is too large, a dimensional change of expansion occurs in the MD direction.

  The elastic deformation range can be calculated from an elastic strain according to Hook's law by performing a tensile test with an autograph. That is, the point where the stress-strain curve deviates from the straight line is defined as the elastic limit.

  The tension for stretching the protective film is appropriately selected depending on the composition and thickness of the film, but is preferably 60 kg / m or more and 200 kg / m or less. If the tension is within the above range, most polyimide films can be stretched in the MD direction.

  In the flexible metal-clad laminate obtained by the manufacturing method according to the present invention, the dimensional change rate before and after removing the metal foil, and the total value of the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil. However, it is very preferable that both the MD direction and the TD direction are in the range of -0.08 to +0.08. The rate of dimensional change before and after removal of the metal foil is expressed as a ratio between a difference between a predetermined dimension in the flexible metal-clad laminate before the etching process and a predetermined dimension after the etching process and a predetermined dimension before the etching process. . The dimensional change rate before and after heating is represented by a ratio between a difference between a predetermined dimension in the flexible metal-clad laminate after the etching process and a predetermined dimension after the heating process, and a predetermined dimension after the etching process.

  If the dimensional change rate is out of this range, the defect rate at the time of component mounting tends to increase in the flexible metal-clad laminate.

  The method for measuring the dimensional change rate is not particularly limited, and any method known in the art can be used as long as it can measure the increase or decrease in dimensions that occurs before and after the etching or heating process in the flexible metal-clad laminate. Can be used.

  Here, it is essential to measure the dimensional change rate in both the MD direction and the TD direction. When imidizing and laminating continuously, the tension is different in the MD direction and the TD direction, so a difference appears in the degree of thermal expansion / contraction and the dimensional change rate is also different. Therefore, a material having a small dimensional change rate is required to have a low change rate in both the MD direction and the TD direction. In the present invention, the dimensional change rate before and after removing the metal foil of the flexible metal-clad laminate, and the total value of the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil are MD direction, It is very preferable that the TD direction is in the range of -0.08 to +0.08.

  In addition, the specific conditions of the etching process at the time of measuring a dimensional change rate are not specifically limited. That is, since the etching conditions differ depending on the type of metal foil and the shape of the pattern wiring to be formed, the etching process conditions for measuring the dimensional change rate in the present invention are any conventionally known conditions. Also good. Similarly, in the heating process, it is sufficient that heating is performed at 250 ° C. for 30 minutes, and specific conditions are not particularly limited.

  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 glass transition temperature of the thermoplastic polyimide, the elastic deformation rate of the protective film, the dimensional change rate of the flexible laminate, and the metal foil peel strength in the synthesis examples, examples, and comparative examples are as follows.

(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.

(Elastic deformation rate)
The elastic deformation range was calculated from an elastic strain according to Hook's law by performing an autograph tensile test (JIS K7127). The calculation results are shown below.
125 NPI: 4.3%, 75 NPI: 4.0%, 125AH: 5.2%

(Dimensional change rate)
Based on JIS C6481, four holes were formed in the flexible laminate, and the distance of each hole was measured. Next, after carrying out an etching process to remove the metal foil from the flexible laminate, it was left in a temperature-controlled room at 20 ° C. and 60% RH for 24 hours. Then, each distance was measured about the said four holes similarly to the etching process front. The measured value of the distance of each hole before metal foil removal was set to D1, and the measured value of the distance of each hole after metal foil removal was set to D2, and the dimensional change rate was calculated | required by following Formula.
Dimensional change rate (%) = {(D2-D1) / D1} × 100
In addition, the said dimensional change rate was measured about both MD direction and TD direction.

Subsequently, the measurement sample after etching was heated at 250 ° C. for 30 minutes and then left in a constant temperature room at 20 ° C. and 60% RH for 24 hours. Then, each distance was measured about the said four holes. The measured value of the distance of each hole after heating was set to D3, and the dimensional change rate before and after heating was obtained by the following formula.
Dimensional change rate (%) = {(D3-D2) / D2} × 100
In addition, the said dimensional change rate was measured about both MD direction and TD direction.

(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 thermoplastic polyimide precursor)
780 g of DMF and 115.6 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) were added to a glass flask having a capacity of 2000 ml, and 3,3′4 while stirring under a nitrogen atmosphere. , 4'-biphenyltetracarboxylic dianhydride (BPDA) was gradually added. Subsequently, 3.8 g of ethylenebis (trimellitic acid monoester acid anhydride) (TMEG) was added and stirred for 30 minutes in an ice bath. A solution in which 2.0 g of TMEG was dissolved in 20 g of DMF was separately prepared, and this was gradually added to the reaction solution while being careful of the viscosity and stirred. When the viscosity reached 3000 poise, addition and stirring were stopped to obtain a polyamic acid solution.

  This polyamic acid solution was cast on a 25 μm PET film (Therapy HP, manufactured by Toyo Metallizing Co., Ltd.) so as to have a final thickness of 20 μm, and dried at 120 ° C. for 5 minutes. After peeling off the dried self-supporting film from PET, it is fixed to a metal pin frame and dried at 150 ° C. for 5 minutes, 200 ° C. for 5 minutes, 250 ° C. for 5 minutes, 350 ° C. for 5 minutes, A single layer sheet was obtained. The glass transition temperature of this thermoplastic polyimide was 240 ° C.

(Examples 1-4, Reference Examples 1-3; Production of flexible copper-clad laminate (FCCL))
After diluting the polyamic acid solution obtained in Synthesis Example 1 with DMF to a solid content concentration of 10% by weight, a thermoplastic polyimide layer (adhesive layer) is formed on both sides of 17 μm apical HP (manufactured by Kaneka Chemical Co., Ltd.). The polyamic acid was applied so that the final single-side thickness of 4) was 4 μm, and then heated at 140 ° C. for 1 minute. Subsequently, heat imidization was performed by passing through a far infrared heater furnace having an atmospheric temperature of 390 ° C. for 20 seconds to obtain a heat resistant adhesive film. 18 μm rolled copper foil (BHY-22B-T, manufactured by Japan Energy Co., Ltd.) is used on both sides of the obtained adhesive film, and the protective film shown in Table 1 is used on both sides of the copper foil. A flexible metal-clad laminate is obtained by continuous thermal lamination under conditions of adhesive film tension 0.4 N / cm, laminating temperature 360 ° C., laminating pressure 196 N / cm (20 kgf / cm), laminating speed 1.5 m / min. Produced. Table 1 shows the characteristics of the flexible metal-clad laminate.

  As shown in Comparative Examples 1 to 3, when the MD stretching of the protective film was not appropriate, the resulting flexible metal-clad laminate was inferior in dimensional change. On the other hand, in Examples 1 to 4 in which the MD direction stretching of the protective film was controlled within an appropriate range, good dimensional stability was confirmed.

Claims (7)

A method for producing a flexible metal-clad laminate excellent in dimensional stability, obtained by laminating a metal foil on one or both sides of a polyimide film via an adhesive layer, between a heating and pressing surface and a metal foil A method for producing a flexible metal-clad laminate, comprising: providing a protective film; and laminating the protective film in a state of being stretched in the MD direction within an elastic deformation range. 2. The flexible metal-clad laminate according to claim 1, wherein the flexible metal-clad laminate is obtained by laminating a metal foil and a polyimide film through an adhesive layer by a hot roll laminating apparatus having a pair of metal rolls. A manufacturing method of a laminated board. The method for producing a flexible metal-clad laminate according to claim 1 or 2, wherein the protective film tension during heat lamination is 60 kg / m or more and 200 kg / m or less. The method for producing a flexible metal-clad laminate according to any one of claims 1 to 3, wherein the protective film is brought into contact with a hot roll in advance so that the temperature of the protective film is 0 to -10 ° C with respect to the roll temperature during lamination. The method for producing a flexible metal-clad laminate according to claim 1, wherein the thermal lamination temperature is 300 ° C. or higher. The method for producing a flexible metal-clad laminate according to claim 1, wherein the adhesive layer contains thermoplastic polyimide. The dimensional change rate before and after removing the metal foil, and the total value of the dimensional change rate before and after performing heat treatment at 250 ° C. for 30 minutes after removing the metal foil is −0.08 to + 0.08% in both the MD direction and the TD direction. The flexible metal-clad laminate obtained by the manufacturing method according to claim 1, wherein the laminate is in the range of