JP2005193404A - Manufacturing method of flexible metal clad laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving a manufacturing method of a flexible metal clad laminate excellent in dimensional stability. <P>SOLUTION: The manufacturing method of the flexible metal clad laminate includes at least a process (A) for obtaining a metal clad laminate by continuously laminating a metal foil on one side or both sides of a polyimide film through an adhesive layer while applying tension to the polyimide film in its MD direction and a process (B) for continuously heat-treating the metal clad laminate while applying tension lower than that in the process (A) to the metal clad laminate in its MD direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flexible metal-clad laminate excellent in 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, it is expected that required characteristics such as heat resistance, flexibility and electrical reliability will become severe in the future. As an FPC that can meet such demands, there is 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 heat-resistant resin such as a thermoplastic polyimide is used for an adhesive layer. Proposed and expected to increase demand 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 an adhesive sheet having high heat resistance. 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 a resin having high heat resistance 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 exhibit heat fusion. For this reason, residual distortion occurs in the flexible metal-clad laminate obtained by laminating and appears as a dimensional change when forming a wiring by etching, or when performing solder reflow to mount a component.

  In particular, in the laminating method, when an adhesive layer is provided on a polyimide film, the material is placed under a heating environment in a tensioned state because it is continuously heated and pressurized when the metal foil is bonded. Many. 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 particular, when thermoplastic polyimide is used as the adhesive layer, the precursor polyamic acid is cast and applied, and then continuously heated to imidize and adhere to the metal foil. Heat is also applied, and this behavior is remarkable.

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.

On the other hand, a method for improving the dimensional stability by heat-treating the flexible metal foil laminate has been proposed (Patent Document 4). However, it is said that the heat treatment in this case needs to be performed in a state of being wound around a sheet or a core material, and there is no description about performing the heat treatment continuously under a specific tension. Also, when heat treatment is performed on a single wafer, the appearance of the flexible metal foil laminate is impaired if the temperature is increased in order to exert the effect of improving the dimensional stability greatly, or the roll is wrinkled when wound around the core material and heat-treated in a roll shape. There are disadvantages such as the effect of improving the dimensional stability is different because the radius of curvature is different between the winding core side and the winding outer side.
JP-A-9-199830 JP 2002-326308 A JP 2002-326280 A JP 2001-270035 A

  This invention is made | formed in view of said subject, The objective is to provide the method of improving the manufacturing method of the flexible metal-clad laminated board which is excellent in dimensional stability.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have conducted heat treatment at 250 ° C. for 30 minutes after removing the metal foil and the dimensional change rate before and after removing the metal foil by heating the flexible metal-clad laminate under specific conditions. The inventors have found that the dimensional change rate before and after can be improved and have completed the present invention.

That is, the present invention relates to a method for producing a flexible metal-clad laminate including at least the following steps.
(A) A process of obtaining a metal-clad laminate by continuously laminating with a metal foil while applying tension in the MD direction to one or both sides of a polyimide film via an adhesive layer (B) A) A step of continuously heat-treating while applying a lower tension in the MD direction than the step. Further, in the present invention, the bonding with the metal layer in the step (A) is performed by a hot roll laminator having a pair of metal rolls. The method for producing a flexible metal-clad laminate according to claim 1.

  Furthermore, the present invention relates to the method for producing a flexible metal-clad laminate according to claim 1 or 2, wherein the heat treatment temperature in step (B) is not less than the glass transition temperature of the adhesive layer and not more than the laminate temperature.

  Furthermore, in the present invention, the adhesive layer contains a thermoplastic polyimide, and the method for improving the dimensional stability of a flexible metal-clad laminate according to any one of claims 1 to 3.

  Further, 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 performing heat treatment at 250 ° C. for 30 minutes after removing the metal foil are −0.15 in both the MD direction and the TD direction. It is in the range of-+ 0.15, It is related with the flexible metal-clad laminate obtained by the manufacturing method of Claims 1-4.

  According to the present invention, it is possible to improve the dimensional stability of a flexible metal-clad laminate, particularly a flexible printed circuit board manufactured by a laminating method. 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 method for producing a flexible metal-clad laminate according to the present invention is a method for producing a flexible metal-clad laminate including at least the following steps.
(A) A process of obtaining a metal-clad laminate by continuously laminating with a metal foil while applying tension in the MD direction to one or both sides of a polyimide film via an adhesive layer (B) A) The process of heat-treating continuously, applying the tension | tensile_strength lower than a process to MD direction.
(A) Step (A) In step (A), one side or both sides of a polyimide film are continuously bonded to a metal foil via an adhesive.

  The polyimide film will be described. The polyimide film used in the present invention is manufactured using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid. Usually, aromatic tetracarboxylic dianhydride and aromatic diamine are reacted in a substantially equimolar amount dissolved in an organic solvent, and controlled. And stirring under the 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.

  In this invention, it is also preferable to use the polymerization method which obtains a prepolymer using the diamine component which has a rigid structure mentioned later. When the diamine component used in preparing the prepolymer is a diamine composed of a diamine having a rigid structure, a polyimide film having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained. In this method, the molar ratio of the diamine having a rigid structure used in preparing the prepolymer to the acid dianhydride 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, bis (2,3 -Dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 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 alone or Any proportion of the mixture can be preferably used.

  Among these acid dianhydrides, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′ It is preferable to use at least one selected from 4,4'-biphenyltetracarboxylic dianhydride.

  Among these acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetra The preferred amount of use in the case of using at least one selected from carboxylic dianhydrides is 60 mol% or less, preferably 55 mol% or less, more preferably 50 mol% or less, based on the total acid dianhydrides. 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride When using at least one kind, if the amount used exceeds this range, the glass transition temperature of the polyimide film may become too low, or the storage elastic modulus at the time of heating may become too low, making film formation itself difficult. Therefore, it 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 polyamic acid according to the present invention include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, and 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'-diaminodiphenylethylphosphineoxy 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diamino Benzene, 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'-diaminobenzophenone and its And La analogs thereof.

    As the diamine component, a diamine having a rigid structure and an amine having a flexible structure can be used in combination, and the preferred use ratio in that case is 80/20 to 20/80, more preferably 70/30 to 30/70, in molar ratio. Particularly, it is 60/40 to 30/70. 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. In some cases, the film formation is difficult, and it may be harmful.

  In the present invention, the diamine having a rigid structure is

R2 in the formula is

And R _{3 in} the formula is the same or different and is H—, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —, or a group selected from the group consisting of divalent aromatic groups. Any one group selected from the group consisting of COOH, —CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—)
The one represented by

  Further, the diamine having a flexible structure is a diamine having a flexible structure such as an ether group, a sulfone group, a ketone group, and a sulfido group, and is preferably represented by the following general formula (2). .

(R ₄ in the formula is

R _{5 in} the formula is the same or different and is H—, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —, or a group selected from the group consisting of divalent organic groups represented by One group selected from the group consisting of COOH, —CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—. )
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 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. In the region, it is partially cured and / or dried by activating the dehydrating agent and imidization catalyst by heating for 30 seconds to 10 minutes, and then peeled off from the support to form a polyamic acid film (hereinafter referred to as gel film). Get.
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. If outside the above range, defects such as film breakage, uneven color tone of the film due to uneven drying, 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.

  The polyimide film thus obtained may be subjected to any known surface treatment for improving the adhesive strength. Examples of the surface treatment method include titanium or silane coupling agent treatment, corona discharge treatment, and plasma treatment.

  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. Preferably it is 1-50 kg / m, More preferably, it is 1.5-40 kg / m, Most preferably, it is 2-30 kg / m. 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).

  The metal foil will be described. 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.

    The adhesive layer will be described. The adhesive layer used in the present invention remarkably exhibits dimensional stability, which is an effect of the invention, particularly when an adhesive layer containing a resin having high heat resistance is used. Of course, any resin may be used. Absent. Examples of heat-sealable thermoplastic resins include polyimide resins, polyamide resins, polyester resins, polycarbonate resins, polyketone resins, polysulfone resins, polyphenylene ether resins, polyolefin resins, polyphenylene sulfide resins, fluororesins, poly resins Examples include arylate resins and liquid crystal polymer resins, and it is preferable to contain a thermoplastic polyimide resin in terms of insulation reliability and laminate processability. Examples of the thermosetting resin include acrylic resins, epoxy resins, modified epoxy resins, phenol resins, bismaleimide resins, and methacrylic resins. These resins can be used in appropriate combination.

  As the thermoplastic polyimide, thermoplastic polyimide, thermoplastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide, and the like can be suitably used.

  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).

  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 characteristics can be adjusted by combining various raw materials to be used, but generally the glass transition temperature becomes higher and / or the storage elastic modulus during heating becomes higher when the ratio of rigid-structure diamine is increased. 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.

  In order to provide an adhesive layer from the above polyamic acid solution, a method of providing an adhesive layer by casting on a polyimide film and / or a metal foil, drying and imidizing, a polyimide film and / or a cast film on a PET film, etc. Any method such as a method of transferring to a metal foil to provide an adhesive layer or a method of forming a thermoplastic polyimide film and using it as an adhesive film may be used. Another resin can be dissolved in the polyamic acid solution and used as a polymer blend. The method of casting and coating on the polyimide film is not particularly limited, and existing methods such as a die coater, a reverse coater, and a blade coater can be used. The coating thickness is not particularly limited, and may be adjusted appropriately for each application. However, if the coating thickness becomes too thick, the time required for curing becomes long, so that problems such as reduced productivity are likely to occur. It is preferable to apply so that the thickness after the formation becomes 10 μm or less.

  In general, a polyimide is obtained by imidizing a polyamic acid which is a precursor thereof. For imidization, a thermal imidization method or a chemical imidization method is used alone or in combination. In the chemical imidization method, examples of the dehydrating agent include aliphatic acid anhydrides, aromatic acid anhydrides, N, N′-dialkylcarbodiimides, halogenated lower aliphatics, halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, And thionyl halide, or a mixture of two or more thereof. Among these, from the viewpoint of easy availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic acid anhydride, or a mixture of two or more thereof can be preferably used. Moreover, as an imidation catalyst, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, etc. are used, for example. Among them, those selected from heterocyclic tertiary amines are particularly preferably used from the viewpoint of reactivity as a catalyst. Specifically, quinoline, isoquinoline, β-picoline, pyridine and the like are preferably used.

Any method requires imidization and / or drying by heating, and the higher the heating temperature, the easier the imidization occurs. Is preferable. 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.

  Except changing to the said temperature range, the manufacturing method of a thermoplastic polyimide film can be performed by performing just like the case where a polyimide film is manufactured.

  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.

  Alternatively, a thermoplastic polyimide layer can be provided by applying a solvent-soluble polyimide solution on the polyimide film.

  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. The protective material is not particularly limited as long as it can withstand the heating temperature in the heat laminating process, and preferably a heat-resistant plastic such as a non-thermoplastic polyimide film, a metal foil such as a copper foil, an aluminum foil, or a SUS foil. Can be used. Among these, a non-thermoplastic polyimide film is more preferably used from the viewpoint of excellent balance between heat resistance and reusability. In addition, if the thickness is thin, the protective material does not sufficiently fulfill the role of buffering and protection at the time of lamination. Therefore, the thickness of the protective material is preferably 75 μm or more.

  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.

  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.

  When an adhesive layer containing a resin having high heat resistance as described above is used, it is necessary to increase the laminating temperature. For example, when a heat-sealing resin is used, it is preferable that the thermoplastic resin constituting the adhesive layer has a Tg of at least 180 ° C. or higher. Lamination temperature is required. For this reason, residual distortion occurs in the flexible metal-clad laminate obtained by laminating and appears as a dimensional change when forming a wiring by etching, or when performing solder reflow to mount a component. Therefore, in the present invention, when the heat laminating temperature is 200 ° C. or higher, preferably, or higher, the effect is remarkably exhibited.

  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.

(B) Step (B) In the step (B), the metal-clad laminate obtained in the step (A) is continuously heat-treated while applying a lower tension in the MD direction than in the step (A).

  The tension in the MD direction when the heat treatment is performed in the step (B) may be lower than the tension in the step (A), but it is preferable to reduce the tension as much as possible without affecting the transportability and the winding property. The tension is preferably 90% or less, preferably 80% or less of the tension during lamination. If the tension exceeds this range, the effect of improving the dimensional stability becomes difficult to develop, and the MD / TD (film width direction) anisotropy of the dimensional stability increases.

  For the heat treatment, a heating means employing a conventionally known method capable of heating at a predetermined temperature, such as a hot air circulation method, a hot air heating method, an induction heating method, or the like can be used. The heat treatment temperature is not less than the glass transition temperature of the adhesive layer and is preferably not more than the lamination temperature. When the temperature is not higher than the glass transition temperature of the adhesive layer, it is difficult to obtain an effect of improving dimensional stability. Moreover, when it heat-processes above lamination temperature, it exists in the tendency for the external appearance of a flexible metal-clad laminated board to be impaired easily.

  The heat treatment may be performed before winding after obtaining the metal laminate obtained in the step (A), or may be heat treated after winding. In addition, when the heat treatment is performed, the metal conductor layer is easily oxidized at a temperature of 200 ° C. or higher, particularly 250 ° C. or higher.

  In the flexible metal-clad laminate obtained by the manufacturing method according to the present invention, the dimensional change rate before and after completely removing the metal foil, and the dimensional change rate before and after heating at 250 ° C. for 30 minutes after removing the metal foil. It is very preferable that the total value is in the range of -0.10 to +0.10 in both the MD direction and the TD direction. 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 before the heating 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 -0.10 to +0.10.

  In addition, the specific conditions of the metal foil whole surface 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 and thickness of the metal foil, the conditions of the etching process when measuring the dimensional change rate in the present invention may be any conventionally known conditions. 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 method of the glass transition temperature of the thermoplastic polyimide in a synthesis example, an Example, and a comparative example, the dimensional change rate of a flexible laminated board, and metal foil peeling strength is as follows.

(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 before 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.
Moreover, the dimensional change rate after heat processing calculated | required the dimensional change rate by following Formula from the measured value D2 of the distance of each hole after metal foil removal, and distance D3 of each hole after heat-processing for 30 minutes at 250 degreeC.
Dimensional change rate (%) = {(D3-D2) / D2} × 100
In addition, the distance measurement of each hole was measured after adjusting the humidity for 12 hours or more in an environment of 23 ° C. and 55% RH.
(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.
(Elastic modulus)
The elastic modulus was measured according to ASTM D882.
(Linear expansion coefficient)
The linear expansion coefficient at 50 to 200 ° C. was measured by using TMA120C manufactured by Seiko Electronics Co., Ltd. (sample size: 3 mm width, 10 mm length), and the temperature was temporarily increased from 10 ° C. to 400 ° C. at a load of 3 g at 10 ° C./min. After heating, the temperature was cooled to 10 ° C., the temperature was further increased at 10 ° C./min, and the average value was calculated from the thermal expansion coefficients at 50 ° C. and 200 ° C. during the second temperature increase.
(Hygroscopic expansion coefficient)
The hygroscopic expansion coefficient was determined by measuring the film dimensions (L1) in an environment of 50 ° C. and 30% Rh, and then changing the humidity to measure the film dimensions in an environment of 50 ° C. and 80% Rh (L2). Calculate from the formula.
Hygroscopic expansion coefficient (ppm) = (L1−L2) ÷ L1 ÷ (80−30) × 10 ⁶
(Dynamic viscoelasticity measurement)
Using DMS200 manufactured by Seiko Electronics Co., Ltd. (sample size: width 9 mm, length 40 mm), the frequency was 1, 5 and 10 Hz, and the temperature increase rate was 3 ° C./min. The temperature at which the inflection point of the curve in which the storage elastic modulus was plotted against the temperature was taken as the glass transition temperature.
(Judgment of thermoplasticity)
Using TMA120C manufactured by Seiko Electronics Co., Ltd., compression mode (probe diameter: 3 mmφ), 10 ° C / min at a load of 5 g, the temperature was once raised from 10 ° C to 400 ° C, cooled to 10 ° C, and subjected to permanent compression deformation The presence or absence was judged.

(Reference Example 1: Production of polyimide film)
After dissolving 3.75 kg of p-phenylenediamine (p-PDA) in 231 kg of N, N-dimethylformamide (DMF) cooled to 10 ° C., 7.50 kg of pyromellitic dianhydride (PMDA) was added for 1 hour. Stir to dissolve. After dissolving 20.85 kg of 4,4′-oxydianiline (ODA), 8.17 kg of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added for 2 hours. Stir to dissolve. To this, 21.05 kg of PMDA was further added and stirred for 1 hour to completely dissolve PMDA.

A separately prepared DMF solution of PMDA (PMDA: DMF = 0.91 kg: 12.1 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 3000 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution having a solid content of 19% by weight and a rotational viscosity at 23 ° C. of 3400 poise. (Molar ratio: p-PDA / ODA / BPDA / PMDA = 25/75/20/80).
This polyamic acid solution is composed of acetic anhydride / isoquinoline / DMF (weight ratio 18.90 / 7.17 / 18.93) (2.22 mol of acetic anhydride and 0.666 mol of isoquinoline with respect to 1 mol of amic acid). The curing agent was continuously stirred by a mixer at a weight ratio of 50% with respect to the polyamic acid solution, extruded from a T die, and cast on a stainless endless belt running 20 mm below the die. The 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 45% by weight) and fixed to the tenter clip, 300 ° C. for 20 seconds, 450 ° C. × 20 After being dried and imidized at 500 ° C. for 20 seconds, plasma treatment was performed to obtain a 17 μm polyimide film.
Elastic modulus 5.5GPa
Hygroscopic expansion coefficient 10ppm
Linear expansion coefficient 18ppm (average value of 100-200 ° C)
(Reference Example 2: 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. Further, in the determination of thermoplasticity, it was found that the thermoplastic has thermoplasticity due to the occurrence of permanent compression deformation.

(Reference Example 3, production of flexible copper clad laminate (FCCL))
After diluting the polyamic acid solution obtained in Reference Example 2 with DMF until the solid content concentration becomes 10% by weight, the final one side of the thermoplastic polyimide layer (adhesive layer) is formed on both sides of the polyimide film obtained in Reference Example 1 Polyamic acid was applied so that the thickness 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. By using 18 μm rolled copper foil (BHY-22B-T, manufactured by Japan Energy Co., Ltd.) on both sides of the obtained adhesive film, and further using a protective material (Apical 125 NPI; manufactured by Kaneka Chemical Co., Ltd.) on both sides of the copper foil, FCCL was prepared by continuous thermal lamination under the conditions of polyimide film tension 0.4 N / cm, laminating temperature 360 ° C., laminating pressure 196 N / cm (20 kgf / cm), laminating speed 1.5 m / min. Table 1 shows the characteristics of this FCCL.

(Examples 1-3, Comparative Example 1)
Table 1 shows the results of continuously heat-treating the FCCL obtained in Reference Example 1 under various conditions in a nitrogen atmosphere using a hot air circulation oven.

(Comparative Example 2)
When FCCL obtained in Reference Example 1 was heat treated at 300 ° C. for 2 minutes in a nitrogen atmosphere in a single wafer, FCCL wavy and FCCL with good appearance could not be obtained.

(Comparative Example 3)
When the FCCL obtained in Reference Example 1 was wound 100 times on a stainless steel tube with a thickness of 3 mm and an inner diameter of 6 inches and heat-treated at 360 ° C. for 10 minutes in a nitrogen atmosphere, the curl was attached and a flat FCCL could not be obtained. It was.

Claims (5)

A method for producing a flexible metal-clad laminate including at least the following steps (A) A metal-clad laminate by continuously bonding with a metal foil while applying tension in the MD direction to one or both sides of a polyimide film via an adhesive layer Step of obtaining plate (B) Step of continuously heat-treating metal-clad laminate while applying lower tension in MD direction than step (A) The method for producing a flexible metal-clad laminate according to claim 1, wherein the bonding with the metal layer in the step (A) is performed by a hot roll laminator having a pair of metal rolls. The method for producing a flexible metal-clad laminate according to claim 1 or 2, wherein the heat treatment temperature in step (B) is not less than the glass transition temperature of the adhesive layer and not more than the lamination temperature. The method for improving dimensional stability of 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 −0.15 to +0.15 in both the MD direction and the TD direction. The flexible metal-clad laminate obtained by the production method according to claim 1, wherein the laminate is in a range.