JP2009154446A - Metal-clad laminate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide resin layer with adhesiveness to stainless foil or conductor metal foil through a simple process and to facilitate control of an etched shape of the polyimide resin layer that is produced by wet etching using an alkali aqueous solution or the like. <P>SOLUTION: This metal-clad laminate includes a metallic layer A, a polyimide resin layer B, an adhesive layer C, and a metallic layer D arranged in this order. The polyimide resin layer B is a single layer 5 to 50 μm thick and has an efficient of thermal expansion of 10 x 10<SP>-6</SP>to 30 x 10<SP>-6</SP>(1/K). The adhesive layer C is a layer containing a thermoplastic polyimide resin and 0.001 to 1.0 μm thick. A polyamide acid layer, i.e., a precursor of the polyimide resin layer not less than 50% of which forms the polyimide resin layer B as the volume percentage of the adhesive layer C, is impregnated with a precursor solution of a thermoplastic polyimide resin and is then dried and heat treated to form the metal-clad laminate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal-clad laminate and a method for manufacturing the same, and more particularly to a metal-clad laminate suitable for hard disk drive (HDD) suspension applications and a method for producing the same.

  HDD production has been increasing with the recent increase in demand for personal computers and new installations in home appliances and car navigation systems. In addition, HDDs are expected to increase in capacity and miniaturization in the future, and suspension parts constituting flexure blanks that read magnetism in HDDs are becoming smaller, more diversified in wiring, and thinner. As capacity increases, most of the wireless type suspensions that have been used in the past are replaced by suspensions with integrated wiring that have stable buoyancy and positional accuracy with respect to the disk that is the storage medium. Among wiring-integrated suspensions, there is a type called a TSA (Trace Suspension Assembly) method in which a laminate of stainless steel foil-polyimide resin-copper foil is processed into a predetermined shape by etching.

  The method of etching polyimide is roughly divided into a dry etching type using a plasma method and a wet etching type using an alkaline solution, but the latter wet etching type method has recently been applied from the viewpoint of processing cost and the like. . In addition, with the technological innovation of suspensions such as fly-high control and microactuators, the number of signal lines has also increased, and this has led to thinner wires. Metal-clad laminates used as HDD suspension materials are also required to have metal-polyimide adhesive strength and dimensional stability during circuit processing. Further, there is no exception with respect to the etching accuracy at the time of polyimide processing, and the requirements are severe regarding the processed shape after etching. In general, the polyimide used in these suspension materials has a three-layer structure that uses thermoplastic polyimide and low thermal expansion polyimide to develop metal-polyimide bond strength when thermocompression bonding the metal. It is configured. The thermoplastic polyimide used here and the low thermal expansion polyimide have different dissolution rates (etching rates) due to the alkali treatment liquid, etc., so, for example, the etching rate of thermoplastic polyimide is faster than the etching rate of low thermal expansion polyimide. In such a case, an undercut may occur during the etching process, or on the contrary, if it is slow, a thermoplastic polyimide layer having a slow etching rate may remain in a bowl shape after the etching. With regard to suspensions that require strict cleanliness, such a polyimide shape defect may cause generation of particles during ultrasonic cleaning, or may cause malfunction when mounted on a hard disk.

  On the other hand, methods for reducing the thickness of thermoplastic polyimide and materials that do not contain thermoplastic polyimide have been proposed. For example, in Japanese Patent Application Laid-Open No. 2006-190824 (Patent Document 1), the thickness of a polyimide layer in contact with a conductor is set to 2.0 μm in order to prevent wiring sinking when an IC chip is mounted in a COF (chip on film) manufacturing process. The following laminates have been proposed. However, such a laminate does not take into account the difference in the etching rate between non-thermoplastic polyimide and thermoplastic polyimide, and tends to cause shape defects after etching of the polyimide resin layer.

  On the other hand, a method has been proposed in which the thickness ratio of the thermoplastic polyimide in the outermost layer of the non-thermoplastic polyimide is defined to control overetching or undercut during wet etching (Patent Document 2). However, with this method, it is difficult to completely match the etching rates of the non-thermoplastic polyimide and the thermoplastic polyimide, so it is difficult to accurately control the etching shape including overetching and undercutting. .

  Moreover, in order to control overetching and undercut during wet etching, a metal laminate having a single polyimide resin layer has been proposed (Patent Document 3). However, such a polyimide resin layer is thermoplastic, and its molecular structure has a larger coefficient of thermal expansion than that of metal, and it is considered that there is a problem in dimensional stability of the material.

JP 2006-190824 A Japanese Patent Laying-Open No. 2005-111858 JP 2004-276413 A

  The present invention improves the dimensional stability as a metal-clad laminate while preventing the occurrence of undercuts and wrinkle-like etching residues during polyimide etching while imparting high adhesion to the metal layer to the polyimide resin layer. Another object of the present invention is to provide a metal-clad laminate suitable for HDD suspension applications that can sufficiently meet the demand for higher-level microcircuits. Another object is to provide an HDD suspension manufactured from the metal-clad laminate.

  As a result of intensive studies to achieve the above object, the present inventors have found that when a specific adhesive layer is present between a specific polyimide resin layer and a metal foil, it is insulated from the conductor layer of the manufactured laminate. It is possible to have excellent uniformity of adhesion between the surfaces of the resin layer, to control the dimensional change rate of the laminate, to be a material that does not generate warpage, and to control the shape during polyimide etching. It has been found that it becomes easy and the present invention has been completed.

That is, the present invention is a metal-clad laminate composed of a metal layer A, a polyimide resin layer B, an adhesive layer C and a metal layer D in this order, and the polyimide resin layer B is a single layer having a thickness of 5 to 50 μm. Yes, the thermal expansion coefficient is 10 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K), the adhesive layer C is a layer containing a thermoplastic polyimide resin, and the thickness is 0.001 to 1.0 μm. The volume ratio of the adhesive layer C is impregnated with a precursor solution of a thermoplastic polyimide resin in a polyamic acid layer, which is a polyimide resin precursor of which 50% or more forms a polyimide resin layer B, and is dried and heat-treated. A metal-clad laminate characterized by being a modified layer formed in the above manner.

  Here, 1) the metal layer A is a conductive metal layer having a thickness of 0.1 to 50 μm, and the metal layer D is a stainless steel layer having a thickness of 10 to 50 μm, or 2) the metal layer A is 10 to 50 μm. Satisfying that the metal layer D is a conductive metal layer having a thickness of 0.01 to 50 μm gives a more excellent metal-clad laminate.

（式（１）中、Ar₁は式（２）、式（３）又は式（４）で表される２価の芳香族基を示し、Ar₂は式（５）又は式（６）で表される４価の芳香族基を示す。式（２）〜式（４）及び式（６）において、R₁は独立に炭素数１〜６の１価の炭化水素基又はアルコキシ基を示し、nは独立に０〜４の整数を示し、X及びWは独立に単結合又は-C(CH₃)₂-、-(CH₂)m-、-O-、-S-、-CO-、-SO₂-、-NH-若しくは-CONH-から選ばれる２価の基を示し、mは１〜５の整数を示す。そして、Ar₁1モル中に-(CH₂)m-、-O-、-S-、-CO-、-SO₂-、-NH-及び-CONH-から選ばれる２価の基を合計で１〜３モル含む。） Moreover, this invention is a metal-clad laminated body whose precursor of a thermoplastic polyimide resin has a structural unit represented by following formula (1).

(In formula (1), Ar ₁ represents a divalent aromatic group represented by formula (2), formula (3) or formula (4), and Ar ₂ represents formula (5) or formula (6). In the formulas (2) to (4) and (6), R ₁ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms. , N independently represents an integer of 0 to 4, and X and W independently represent a single bond or —C (CH ₃ ) ₂ —, — (CH ₂ ) m—, —O—, —S—, —CO—. , —SO ₂ —, —NH— or —CONH—, wherein m represents an integer of 1 to 5. And in 1 mol of Ar ₁ , — (CH ₂ ) m—, — (Inclusive of 1 to 3 mol of divalent groups selected from O-, -S-, -CO-, -SO _2- , -NH- and -CONH-)

In the above formula (1), having a tetravalent aromatic group in which Ar ₂ is represented by formula (6) and W is —SO ₂ — gives a more excellent metal-clad laminate.

  The present invention also includes a metal-clad laminate for an HDD suspension comprising the above-described metal-clad laminate, and a HDD suspension formed by processing the metal-clad laminate.

Furthermore, the present invention is a method for producing a metal-clad laminate, characterized in that the following steps a) to d) are essential in producing the metal-clad laminate.
a) A precursor solution of a low thermal expansion polyimide resin having a linear thermal expansion coefficient of 10 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K) is applied onto the metal layer A and dried to obtain a thickness of 5 Forming a polyamic acid layer of ˜50 μm,
b) A thermoplastic polyimide resin precursor solution having a solid content concentration of 0.1% by weight to 3% by weight is applied to the surface side of the polyamic acid layer with a thickness of 1.0 μm or more, and the thermoplastic polyimide Impregnating a resin precursor solution from the surface of the polyamic acid layer into the interior;
c) drying and heat-treating the layer containing the precursor of the thermoplastic polyimide resin to form an adhesive layer C having a thickness of 0.001 to 1.0 μm; and
d) A step of forming a metal layer D on the surface of the adhesive layer C.

  Here, the metal layer D can be formed on the surface of the adhesive layer C. d1) The metal foil is superimposed on the surface of the adhesive layer C and thermocompression bonded, or d2) the metal is formed on the surface of the adhesive layer C. Suitably this is done by depositing a thin film layer.

  Hereinafter, the present invention relating to a metal-clad laminate will be described, and then the present invention relating to a method for producing a metal-clad laminate will be described, but common parts will be described simultaneously.

  The metal-clad laminate of the present invention is composed of a metal layer A, a polyimide resin layer B, an adhesive layer C, and a metal layer D in this order.

  The material of the metal layer A and the metal layer D is not particularly limited as long as it is a layer made of metal. For example, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, stainless steel, tantalum , Titanium, copper, lead, magnesium, manganese, and metals made of these alloys. Among these, stainless steel, copper, or a copper alloy is suitable.

  When the metal layer A or the metal layer D is used for an application requiring spring characteristics or dimensional stability, the material is preferably stainless steel. When electrical conductivity is required, the material is preferably a conductive metal such as copper or a copper alloy. When one of the metal layer A or the metal layer D is required for spring characteristics and dimensional stability and the other is required for electrical conductivity, it is preferable that one material is stainless steel and the other material is a conductive metal. . As an application in which such a case occurs, there is an HDD suspension application. In addition, as both applications requiring electrical conductivity, there is a double-sided flexible printed circuit board (double-sided FPC) application.

  As the stainless steel, for example, a highly elastic and high strength stainless steel such as SUS304 is preferable. Furthermore, in order to suppress the warp of the metal-clad laminate, SUS304 annealed at a temperature of 300 ° C. or higher is preferable. When the metal-clad laminate is applied as an HDD suspension, the thickness of the stainless steel layer is preferably 10 to 50 μm, more preferably 10 to 30 μm, and even more preferably 15 to 25 μm. If the thickness of the stainless steel layer is less than 10 μm, there arises a problem that it is not possible to secure a spring property that sufficiently suppresses the flying height of the slider. On the other hand, if the thickness exceeds 50 μm, the rigidity becomes high and it becomes difficult to lower the mounted slider. .

  As the conductive metal, copper or a copper alloy is preferable. Here, the copper alloy refers to an alloy containing copper as an essential element and containing at least one different element other than copper, such as chromium, zirconium, nickel, silicon, zinc, and beryllium. Say something more than weight percent. As the copper alloy, it is preferable to use copper having a copper content of 95% by weight or more. Examples of the metal contained in copper include chromium, zirconium, nickel, silicon, zinc, and beryllium. An alloy containing two or more of these metals may also be used.

  It is also advantageous that the conductive metal layer is made of a rolled copper foil or an electrolytic copper foil. The rolled copper foil and the electrolytic copper foil can be produced by a known method, and the former can be produced by rolling a copper ingot to a predetermined thickness and repeating heat treatment. Moreover, the electrolytic copper foil can be obtained by depositing copper sulfate as a main component from an electrolytic solution by electrolysis. When used as a HDD suspension, for example, when a fine flying lead with a circuit width of 40 μm or less is formed, a problem such as disconnection is particularly likely to occur. Therefore, the tensile strength of the laminated copper foil is 400 MPa or more. The upper limit is not particularly limited, but 1000 MPa or less is preferable. The thickness of the copper or copper alloy used is preferably 5 to 25 μm, more preferably 7 to 12 μm, and even more preferably 8 to 10 μm. In particular, when the thickness of the conductive metal layer is in the range of 5 to 10 μm, it is preferable to use a highly conductive electrolytic copper foil, and the conductivity is 95% or more, preferably 97% or more, more preferably. It is good that it is 98% or more. By using such a metal layer, it is easy to generate electrical resistance, and heat dissipation can be suppressed to a low level. As a result, impedance can be easily controlled.

  When the conductive metal layer has a thickness of 0.1 to 9 μm, from the viewpoint of handling properties in the laminate manufacturing process, the conductor with the support in which the conductive metal layer is laminated with the support metal layer through the release layer It is preferred to use a metal layer. The conductor metal layer from which the support metal layer has been peeled can be formed into a circuit by a subtractive method or a semi-additive method.

  When using a conductive metal layer with a support, the peel strength between the support metal layer and the conductive metal layer is preferably 1 N / m or more and 100 N / m or less. Preferably it is 1 N / m to 50 N / m, more preferably 3 N / m to 15 N / m, still more preferably 4 N / m to 10 N / m. When the peel strength is less than 1 N / m, the conductor metal layer may peel from the support metal layer in the laminate manufacturing process, which causes a problem in stable operation. On the other hand, when the peel strength exceeds 100 N / m, the laminated body after peeling of the support metal layer is likely to warp. The peel strength here refers to a metal foil 1 mm width 90 ° peeling method (JIS C6471). This peel strength can be changed by adjusting the adhesive strength between the support metal layer and the conductor metal layer (by using a release agent or a low-tack material).

  When the conductive metal layer has a thickness of 0.001 to 1.0 μm, the conductive metal layer can be formed by, for example, a sputtering method. Although details will be described later, when the conductor metal layer is further thickened, it can be formed into a thick film by electroless plating or electrolytic plating. Which metal layer is used as the metal layer A and the metal layer D is determined by the use of the metal-clad laminate, the adhesion between the metal layer and the polyimide resin layer, the ease of manufacturing the metal-clad laminate, and the like.

  The metal-clad laminate of the present invention has a polyimide resin layer B and an adhesive layer C in addition to the metal layer A and the metal layer D. The polyimide resin layer B is formed from a single layer. A single layer having a simple layer structure can be advantageously obtained industrially.

  Hereinafter, the precursor of the polyimide resin that forms the polyimide resin layer B may be abbreviated as polyamic acid b. The precursor of the thermoplastic polyimide resin may be abbreviated as precursor c. Since the polyamic acid or precursor and the polyimide resin are in a relationship between the precursor and the product, the structure of the other is understood by explaining one of them. A distinction is made between the polyamic acid b and the precursor c of the thermoplastic polyimide resin.

  The polyimide resin that forms the polyimide resin layer B can be formed by curing (imidizing) the polyamic acid b that is a precursor of the polyimide resin. Details of the curing will be described later.

  Examples of the polyimide resin that forms the polyimide resin layer B include heat-resistant resins having an imide group in the structure such as polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, polysiloxaneimide, including so-called polyimide resin. . Commercially available polyimide resins (precursors) can also be used suitably.

The polyimide resin layer B is preferably a low thermal expansion polyimide resin from the viewpoint of reducing the warpage of the laminate when the metal layer A or the metal layer D is removed by etching. Specifically, the coefficient of thermal expansion is in the range of 10 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K), preferably 13 × 10 ^{−6 to} 25 × 10 ⁻⁶ (1 / K). Within the range, more preferably within the range of 15 × 10 ⁻⁶ to 23 × 10 ⁻⁶ (1 / K). Such a low thermal expansion polyimide resin is a non-thermoplastic polyimide resin. A non-thermoplastic polyimide resin is excellent in low thermal expansion, but has a feature of poor adhesion.

As the polyimide resin constituting the polyimide resin layer B, a polyimide resin having a structural unit represented by the general formula (7) is preferable. In General Formula (7), Ar ₃ represents a tetravalent aromatic group represented by Formula (8) or Formula (9), and Ar ₄ represents a divalent group represented by Formula (10) or Formula (11). R ₂ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, and V and Y independently represent a single bond or a divalent hydrocarbon having 1 to 15 carbon atoms. A divalent group selected from a group, O, S, CO, SO, SO ₂ or CONH, m independently represents an integer of 0 to 4, q represents a molar ratio of constituent units, 0.1 It is in the range of -1.0.

  The structural unit may be present in the homopolymer or may be present as a structural unit of the copolymer. In the case of a copolymer having a plurality of structural units, it may exist as a block or may exist randomly.

Since a polyimide resin is generally produced by reacting an acid anhydride and a diamine, a specific example of the polyimide resin can be understood by explaining the acid anhydride and the diamine. In the general formula (7), Ar ₃ can be referred to as an acid anhydride residue, and Ar ₄ can be referred to as a diamine residue. Therefore, a preferred polyimide resin will be described using an acid anhydride and a diamine. However, it is not limited to the polyimide resin obtained by this method.

  Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2 ', 3,3'-, 2,3,3', 4'- or 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,3 ', 3,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,3 ', 3,4'-diphenyl ether tetracarboxylic acid Preferred examples include dianhydrides and bis (2,3-dicarboxyphenyl) ether dianhydrides. Also 3,3``, 4,4 ''-, 2,3,3``, 4 ''-or 2,2 '', 3,3 ''-p-terphenyltetracarboxylic dianhydride 2,2-bis (2,3- or 3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3- or 3.4-dicarboxyphenyl) methane dianhydride, bis (2,3- Or 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3- or 3,4-dicarboxyphenyl) ethane dianhydride, 1,2,7,8-, 1,2 , 6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis (3,4-di Carboxyphenyl) tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic Acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6 -Tet Carboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7- (or 1,4,5,8 -) Tetrachloronaphthalene-1,4,5,8- (or 2,3,6,7-) tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3, 5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'- Bis (2,3-dicarboxyphenoxy) diphenylmethane dianhydride and the like can also be mentioned. Among these, the preferred acid anhydride used particularly for HDD suspension applications is one selected from pyromellitic anhydride (PMDA) and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA). There are the above acid anhydrides.

  Examples of the diamine include 4,4′-diaminodiphenyl ether, 4,4′-diamino-2′-methoxy-benzanilide, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-amino). Phenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-diamino-2,2'-dimethylbiphenyl, 3,3'-dihydroxy-4,4'- Diaminobiphenyl, 4,4′-diaminobenzanilide, 2,2-bis- [4- (3-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- ( 3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)] biphenyl, bis [4- (3-aminophenoxy) biphenyl, bis [1- (4-aminophenoxy)] biphenyl, bis [1 -(3-Aminophenoxy)] biphenyl, bis [4- (4-aminophenoxy) ) Phenyl] methane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] ether, bis [4 -(4-Aminophenoxy)] benzophenone, bis [4- (3-aminophenoxy)] benzophenone, bis [4,4 '-(4-aminophenoxy)] benzanilide, bis [4,4'-(3-amino Phenoxy)] benzanilide, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene, 9,9-bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- (4-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis- [4- (3-aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi -2,6-xylidine, 4,4'-methylene-2,6- Diethylaniline, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3 '-Diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3 , 3-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4 '' -Diamino-p-terphenyl, 3,3 ''-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 1,4-bis (4-aminophenoxy) ) Zen, 1,3-bis (4-aminophenoxy) benzene, 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 4,4'-[1,3-phenylenebis (1 -Methylethylidene)] bisaniline, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis ( 2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β- Amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6 -Diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine and the like can be mentioned. Among these, preferable diamines particularly used for HDD suspension applications include 4,4′-diamino-2,2′-dimethylbiphenyl (m-TB), 4,4′-diamino-2′-methoxybenzanilide (MABA). ), 3,4'-diaminodiphenyl ether (DAPE34), 4,4'-diaminodiphenyl ether (DAPE44), 4,4'-bis (4-aminophenoxy) biphenyl (BAPB), 2,7'-bis (4- One or more diamines selected from aminophenoxy) naphthalene (NBOA), 1,3-bis (4-aminophenoxy) benzene (TPE-R), and 1,3-bis (3-aminophenoxy) benzene (APB) is there.

  About said acid anhydride and diamine, only 1 type may be used, respectively, and 2 or more types can also be used together. Thermal dimensional stability can be maintained by selecting and using the above acid anhydrides and diamines. In addition, acid anhydrides and diamines other than those mentioned above can be used in combination, and in this case, the proportions of acid anhydrides and diamines other than those mentioned above are 90 mol% or less, preferably 50 mol% or less. Control the thermal expansion, adhesiveness, glass transition point (Tg), etc. by selecting the types of acid anhydrides and diamines and the molar ratios when using two or more acid anhydrides and diamines. be able to.

  In order to obtain a preferable polyimide resin layer B, when the diamine component is 100 mol%, 4,4′-diamino-2,2′-dimethylbiphenyl (m-TB) is an essential component as the diamine, preferably 50 to It is preferable to use 100 mol%, more preferably 60 to 90 mol%. When diamine other than m-TB is used in combination, 2,7'-bis (4-aminophenoxy) naphthalene (NBOA) and 1,3-bis (4-aminophenoxy) benzene (TPE-R) It is preferred to use at least one 10-30 mol%, more preferably at least one 10-30 mol% of MBOA and TPE-R, and 3,4'-diaminodiphenyl ether (DAPE34) and 4,4 It is preferred to use 1-20 mol% of at least one of '-diaminodiphenyl ether (DAPE44). Furthermore, when the acid anhydride component is 100 mol%, one kind selected from pyromellitic anhydride (PMDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) as the acid anhydride. Or it is preferable to use 100 mol% of 2 types, More preferably, it is good to use only 100 mol% of PMDA. By using such diamines and acid anhydrides, it is possible not only to ensure a sufficient adhesive strength with the metal layer A while improving the low thermal expansion characteristics, but also properties such as high heat resistance and toughness. It is also possible to improve. Also, such a resin layer has excellent etching characteristics with an alkaline aqueous solution, and the polyamic acid layer, which is a precursor of the polyimide resin layer having such characteristics, has an impregnation characteristic of a precursor solution of a thermoplastic polyimide resin. Is also considered excellent. In addition, properties, such as toughness of a polyimide resin layer, can be improved by controlling the weight average molecular weight of the polyamic acid obtained by making the said monomer react. Specifically, the weight average molecular weight (Mw) is controlled to be in the range of 150,000 to 800,000, preferably in the range of 200,000 to 800,000. Here, the weight average molecular weight of the polyamic acid can be determined by a standard polystyrene equivalent weight average molecular weight measured using gel permeation chromatography (GPC).

  The synthesis of the polyamic acid, which is a precursor of the polyimide resin, can be performed by reacting approximately equimolar amounts of diamine and acid anhydride in a solvent. Examples of the solvent to be used include N, N-dimethylacetamide (DMAc), n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and these may be used alone or in combination of two or more. it can.

  The synthesized polyamic acid is used as a solution. Usually, it is advantageous to use as a reaction solvent solution, but if necessary, it can be concentrated, diluted or replaced with another organic solvent. Moreover, since polyamic acid is generally excellent in solvent solubility, it is advantageously used.

  The method of providing the polyimide resin layer B on the metal layer A is to directly apply the polyamide acid b resin solution, which is a precursor of the polyimide resin B, to the metal layer A in order to ensure sufficient adhesive strength with the metal layer A. A method in which the polyimide resin layer B is formed by drying and imidization is preferable. By directly applying a polyamic acid resin solution to the metal layer A, variation in adhesion between the metal layer A and the polyimide resin layer B can be suppressed, and the adhesive strength can be improved. The method for applying the polyamic acid resin solution to the metal layer A is not particularly limited, and can be applied by a coater such as a comma, a die, a knife, or a lip. As the metal layer A, a conductive metal layer having a thickness of 0.1 to 50 μm or a stainless steel layer having a thickness of 10 to 50 μm is suitable. After applying the polyamic acid, it is dried to form a polyamic acid layer. The adhesive strength between the metal layer A and the polyimide resin layer B is preferably 0.5 kN / m or more.

It does not restrict | limit especially as a method to dry, For example, it is good to dry for 1 to 60 minutes on 60-200 degreeC temperature conditions. In this drying step, the temperature is controlled on the side where the adhesive layer is formed so that imidization due to the progress of dehydration and ring closure of the polyamic acid is not completed. For this purpose, it is preferable to perform drying under a temperature condition of 60 to 150 ° C. It is necessary to leave the polyamic acid state on the side on which the adhesive layer is formed in order to impregnate the precursor solution of the thermoplastic polyimide resin. The polyamic acid layer after drying may have part of the polyamic acid structure imidated as described above, but the imidization ratio is 50% or less, more preferably 20% or less, leaving 50% or more of the polyamic acid structure. It is good. The imidization ratio of the polyamic acid is 1,000 cm by measuring the infrared absorption spectrum of the polyimide thin film by a transmission method using a Fourier transform infrared spectrophotometer (commercial product: FT / IR620 manufactured by JASCO Corporation). ^{Based on} the benzene ring carbon hydrogen bond of ⁻¹ , it is calculated from the absorbance derived from the imide group of 1,720 cm ⁻¹ . The thickness of the polyamic acid layer (after drying) is preferably in the range of 5 to 50 μm.

  An adhesive layer C is provided between the polyimide resin layer B and the metal layer D. The adhesive layer C includes 50 vol% or more of a layer in which a part of the surface side of the low thermal expansion polyimide resin layer B (the layer on the metal layer D side) is modified with a precursor solution of a thermoplastic polyimide resin. . The thermoplastic polyimide resin is excellent in adhesiveness, but is different in etching characteristics from the low thermal expansion polyimide resin. Therefore, the adhesiveness is improved while modifying the surface side layer of the low thermal expansion polyimide resin layer B while maintaining the characteristics of the polyimide resin layer B as much as possible. The adhesive layer C includes a modified polyimide resin layer (also referred to as a modified layer or a modified layer B ′) of 50 vol% or more. Here, since the modified polyimide resin layer present in the adhesive layer C is a modified layer of the polyimide resin layer B, its etching property and the like are similar to those of the polyimide resin layer B.

  The adhesive layer C functions as an adhesive layer between the polyimide resin layer B and the metal layer D. An example of a method for obtaining such an adhesive layer C includes a step of producing a metal-clad laminate in which a polyamic acid layer to be a polyimide resin layer B is laminated on the metal layer A (step a), and then the polyamide Applying a precursor solution of thermoplastic polyimide resin to the surface layer of the acid layer to impregnate the polyamide acid layer with the precursor solution of thermoplastic polyimide resin (step b), and drying and heat treatment And a step of forming the adhesive layer C (step c).

Hereinafter, each process will be briefly described by taking the above method as an example.
About the polyamic acid layer formed in step a, a precursor solution of a thermoplastic polyimide resin having a solid content concentration of 0.1 to 3% by weight is added to the surface side layer of the polyamic acid layer in step b by 1.0 μm or more. The polyamic acid layer is impregnated with a precursor solution of a thermoplastic polyimide resin.

  The precursor c of the thermoplastic polyimide resin may be a known thermoplastic polyimide resin precursor obtained from a known acid anhydride and diamine, and can be produced by a known method. For example, it can be obtained by dissolving tetracarboxylic dianhydride and diamine in an organic solvent in approximately equimolar amounts and stirring at 0 to 100 ° C. for 30 minutes to 24 hours to cause a polymerization reaction. In the reaction, it is preferable to dissolve the reaction components so that the obtained polyimide precursor c is 5 to 30% by weight, preferably 10 to 20% by weight, in the organic solvent. As the organic solvent used in the polymerization reaction, it is preferable to use a polar one. Examples of the organic polar solvent include N, N-dimethylformamide, N, N-dimethylacetamide (DMAc), N-methyl. -2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfate, phenol, halogenated phenol, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme and the like. Two or more of these can be used in combination, and some aromatic hydrocarbons such as xylene and toluene can also be used.

  The weight average molecular weight of the precursor c of the thermoplastic polyimide resin is preferably in the range of 10,000 to 500,000, more preferably 100,000 to 400,000, still more preferably 200,000 to 300,000. It is good to set it as the range. The weight average molecular weight can be controlled by the use ratio of tetracarboxylic dianhydride and diamine, and the reaction temperature and reaction time of the polymerization reaction when the precursor of the thermoplastic polyimide resin is produced.

  The solid content concentration of the thermoplastic polyimide resin precursor c solution (hereinafter also referred to as polyimide precursor resin solution) is 0.1 wt% to 3 wt%, preferably 0.5 wt% to 2.5 wt%. The solid content here is understood to be the precursor of the thermoplastic polyimide resin itself, more preferably 1% by weight to 2% by weight. Further, in calculating the solid content concentration, the weight of the solid content is divided by the weight of the polyimide precursor resin solution and expressed as a percentage (%). When the solid content concentration is higher than 3% by weight, it becomes difficult to ensure sufficient adhesive strength with the metal layer when the thickness of the adhesive layer is 1 μm or less.

  The polyimide precursor resin solution may contain an unreacted anhydride and a diamine or oligomer, and the carboxyl group or amino group they have is coupled with the carboxyl group or amino group present in the polyamic acid layer. Thus, it is considered that the adhesiveness is further improved.

  The solid content concentration of the precursor of the thermoplastic polyimide resin is within the above range, so that the impregnation effect can be effectively utilized regardless of the weight average molecular weight of the precursor of the thermoplastic polyimide resin. For example, a low molecular weight type polyimide precursor having a weight average molecular weight of less than 10,000 can suppress in-plane variation of the adhesive layer accompanying the thinning of the adhesive layer, while the weight average molecular weight is 200,000. Also in the above high molecular weight type polyimide precursor, the polyamic acid layer can be easily impregnated, and the amount of the polyimide precursor deposited on the surface of the polyamic acid layer can be suppressed. When the amount is less than the above lower limit, even if the amount of the precursor solution impregnated in the polyamic acid layer is constant, the amount of the precursor of the thermoplastic polyimide resin is insufficient, so that the adhesive strength tends to decrease. . When the above upper limit is exceeded, the impregnation effect of the polyimide precursor resin solution is difficult to obtain, and the amount of the polyimide precursor c deposited on the surface of the polyamic acid layer increases. The thickness tends to change.

  In addition, by setting the solid content concentration within the above range, the surface layer of the polyamic acid layer is likely to swell due to contact with the solvent of the polyimide precursor resin solution, and the polyimide precursor resin is effectively impregnated in this swollen portion. It is considered to be done. This effect is considered to appear immediately after the start of application of the polyimide precursor resin solution, that is, when the polyamic acid layer comes into contact with the polyimide precursor resin solution, and thus can be dealt with by a conventionally known application method, for example, application time A certain effect can be obtained without increasing the length of the film, or increasing the time for which the coating is left after the application is completed, or without special control in the application process.

  A polyimide precursor resin solution is applied to the surface of the polyamic acid layer, and a part or all of the solution is impregnated in the polyamic acid layer. By this impregnation, 50% or more, preferably 70% or more, more preferably 80% or more of the volume ratio of the adhesive layer C becomes an impregnation layer containing the precursor c in the polyamic acid layer. Therefore, after coating and impregnation, each layer includes a polyamic acid layer, an impregnated layer, and an unimpregnated precursor resin solution layer (when there is unimpregnated). That is, a precursor solution of polyamic acid layer / impregnation layer / thermoplastic polyimide resin is formed by applying and impregnating a precursor solution of a thermoplastic polyimide resin on the surface side of the polyamic acid layer. Here, the polyamic acid layer is a layer into which the precursor solution of the thermoplastic polyimide resin is not permeated, and becomes a polyimide resin layer B by imidization by heat treatment. The impregnated layer is a layer in which the precursor solution of the thermoplastic polyimide resin is infiltrated, and becomes a modified layer B 'by imidization by heat treatment. The precursor layer of the thermoplastic polyimide resin is heat-treated and imidized to become a thermoplastic polyimide resin layer C ′.

  A polyimide resin layer B, a modified layer B ′, and a thermoplastic polyimide resin layer C ′ are formed by imidizing the polyamic acid layer and the precursor layer having the above layers by heat treatment. Here, in the modified layer B ′, the concentration of the thermoplastic polyimide resin gradually decreases in the depth direction. The modified layer B ′ and the thermoplastic polyimide resin layer C ′ become the adhesive layer C. The volume, that is, the thickness of the modified layer B ′ in the adhesive layer C is in the above range. The thermoplastic polyimide resin layer C ′ is preferably 0 or as small as possible in order to make the properties of the entire polyimide resin layer uniform, but if the thickness is 1/100 or less of the total thickness of the polyimide resin layer, etching is performed. Even if there is a difference in speed, the overall etching shape is not greatly affected.

  Here, since the polyamic acid layer is a polyimide resin layer that gives the basic performance (low thermal expansion, etc.) of the polyimide resin layer having an adhesive layer, the total thickness of the polyimide resin layer B and the adhesive layer C is 50. % Or more, preferably 80 to 95%. Since the impregnated layer and the precursor resin solution layer provide an adhesive layer, the thickness is preferably 0.001 to 1 μm, more preferably 0.2 to 0.8 μm. The amount of impregnation can be controlled by adjusting the solid content concentration within the above range. And the property such as the etching property of the modified layer generated from the impregnated layer is almost equal to the main component polyimide resin layer B, but the polyimide resin layer generated from the unimpregnated precursor resin solution layer is different from the polyimide resin layer B. Since it is a polyimide resin layer, its thickness should be less than 0.5 μm, preferably less than 0.2 μm. From another viewpoint, the thickness ratio of the modified layer and the thermoplastic polyimide resin layer in the adhesive layer is 10: 0 to 5, preferably 10: 0 to 3, more preferably 10: 0 to 2. The thickness of the adhesive layer with respect to the total thickness 100 of the polyimide resin layer having the adhesive layer is preferably 0.5 to 20, and preferably 1 to 10. In order to control to such a thickness, it is possible to control the concentration of the precursor resin solution and the coating thickness and impregnation time of the precursor resin solution, particularly the concentration and the coating thickness.

  After coating and impregnation, the polyamic acid and the precursor are cured by drying and heat treatment to form a polyimide resin, and a polyimide resin layer B and an adhesive layer C having a thickness of 1 μm or less are formed (step c). Here, the adhesive layer C formed by the heat treatment is generated from the impregnated layer and the unimpregnated precursor resin layer, and the thickness of the adhesive layer C can be measured by a transmission electron microscope (TEM).

  The polyimide precursor resin solution is preferably used after the reaction solvent solution is diluted with an organic polar solvent to obtain a concentration within the above range. The organic polar solvent is preferably one used for the polymerization reaction, more preferably N, N-dimethylacetamide or N-methyl-2-pyrrolidone, and by selecting such a solvent as a dilution solvent, The impregnation effect on the polyamic acid layer is easily obtained.

  The polyimide precursor resin solution has a coating thickness (hereinafter referred to as wet thickness) of 1.0 μm or more, and the thickness of the adhesive layer C formed in the subsequent adhesive layer forming step is 1.0 μm or less, preferably 0. The thickness should be in the range of 0.05 to 0.8 μm, more preferably 0.1 to 0.5 μm. The wet thickness of the polyimide precursor resin solution is preferably 10 to 70 μm, more preferably 20 to 50 μm, and the thickness of the adhesive layer C formed in the adhesive layer forming step is controlled in such a range. Can be within the above range. The method of applying the polyimide precursor resin solution is not particularly limited, and can be applied with a coater such as a comma, die, knife, lip, etc. The application may be performed in several steps. It is industrially advantageous to make the wet thickness by applying the resin once. When the desired wet thickness is 30 μm or more and the desired wet thickness is obtained by applying only once, for example, a die coater having a discharge port height equivalent to the wet thickness can be used, It is preferable to use a lip coater in which the gap distance is a wet thickness. Further, the impregnation method does not require any special operation, and the impregnation can be performed in the process of the above-described application and the operation by drying described later. For example, it is possible to increase the impregnation time by setting the drying temperature lower.

  Also, the drying and curing methods are not particularly limited, and for example, heat treatment such as heating for 1 to 60 minutes at a temperature of 80 to 400 ° C. is suitably employed. In order to obtain the impregnation effect, the drying preferably has a step of holding at 120 to 130 ° C. for 1 to 3 minutes. The total thickness of the polyimide resin layer B and the adhesive layer C is preferably in the range of 5 to 50 μm, more preferably in the range of 7 to 25 μm, and still more preferably in the range of 8 to 12 μm. . Setting the thickness in such a range is suitable when the metal-clad laminate of the present invention is used for HDD suspension applications.

The precursor of the thermoplastic polyimide resin preferably has a structural unit represented by the above formula (1). In Formula (1), Ar ₁ represents a divalent aromatic group represented by Formula (2), Formula (3), or Formula (4), and Ar ₂ is represented by Formula (5) or Formula (6). Represents a tetravalent aromatic group. In the formulas (2) to (4), R ₁ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, n independently represents an integer of 0 to 4, and X and W are 2 independently selected from a single bond or —C (CH ₃ ) ₂ —, — (CH ₂ ) m—, —O—, —S—, —CO—, —SO ₂ —, —NH— or —CONH—. Represents a valent group, and m represents an integer of 1 to 5. Here, a divalent group selected from — (CH ₂ ) m—, —O—, —S—, —CO—, —SO ₂ —, —NH— or —CONH— (hereinafter referred to as a divalent group ( Y)) is a flexible group that gives flexibility to the polyimide resin, and a single bond and -C (CH ₃ ) ₂ -is a group that gives rigidity, so the thermoplastic polyimide can be controlled by controlling the balance The properties of the resin can be adjusted.

In the above general formula (1), Ar ₁ can be referred to as a diamine residue, and Ar ₂ can be referred to as an acid anhydride residue. Therefore, a preferred polyimide resin will be described using a diamine and an acid anhydride. However, it is not limited to the polyimide precursor resin obtained by this method.

  Examples of the diamine include 4,4′-diaminodiphenyl ether, 2′-methoxy-4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-amino). Phenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diamino Biphenyl, 4,4′-diaminobenzanilide and the like can be mentioned. In addition, the diamine mentioned by description of the said polyimide resin can be mentioned. Among these, particularly preferable diamine components include 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane (DANPG), 2,2-bis [4- (4-aminophenoxy) phenyl] propane ( BAPP), 1,3-bis (3-aminophenoxy) benzene (APB), paraphenylenediamine (p-PDA), 3,4'-diaminodiphenyl ether (DAPE34), 4,4'-diaminodiphenyl ether (DAPE44) One or more selected diamines are preferred.

  Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride. In addition, the acid anhydride mentioned by description of the said polyimide resin can be mentioned. Among these, particularly preferred acid anhydrides include pyromellitic anhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3', 4,4'- Examples thereof include at least one acid anhydride selected from benzophenone tetracarboxylic dianhydride (BTDA) and 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA).

  Each of the diamine and acid anhydride may be used alone or in combination of two or more. In addition, diamines and acid anhydrides other than those described above can be used in combination.

  The precursor of the thermoplastic polyimide resin may be a structural unit represented by the formula (1) in the homopolymer or may be present as a structural unit of the copolymer. When they are combined, they may exist as blocks or randomly. There are a plurality of structural units represented by the formula (1), but they may be one type or two or more types. Advantageously, the main component is the structural unit represented by the formula (1), and it is preferably a polyimide precursor resin containing 60 mol% or more, more preferably 80 mol% or more.

The divalent group (Y) which is a flexible group contributes to the adhesiveness of the obtained polyimide resin. The adhesiveness of the polyimide resin is preferably such that the ratio of the divalent group (Y) contained in the polyimide precursor resin is 1.0 mol or more with respect to 1 mol of Ar _2. As the proportion of Y) increases, the mechanical strength (for example, tear strength) of the polyimide resin itself tends to decrease. Therefore, the proportion of the divalent group (Y) is set to 3.0 with respect to 1 mol of Ar _2. It is preferable to make it less than mol.

Further, the precursor of the thermoplastic polyimide resin, in the formula (1), the divalent group in Ar ₂ relative to Ar ₁ 1 mole (Y) is good to be included from 0.4 to 0.8 mol. Preferably, the divalent group (Y) is contained in an amount of 1.6 to 2.4 mol with respect to 2 mol in total of Ar ₁ and Ar ₂ . Since the thermoplastic polyimide resin obtained from the precursor of the thermoplastic polyimide resin can advantageously utilize the impregnation effect according to the present invention, the function as an adhesive layer can be improved. Incidentally, Ar ₁ and Ar ₂ as is apparent from equation (1) because there equimolar except end, Ar ₁ 1 mole is calculated to Ar ₂ 1 mol.

In addition, the precursor of the thermoplastic polyimide resin in Formula (1), more preferably, includes those in which W is —SO ₂ — in Formula (6). Such a thermoplastic polyimide resin precursor is considered to have a high impregnation effect because it has a high polarity —SO ₂ — to improve compatibility with an organic polar solvent.

  In the precursor of the thermoplastic polyimide resin used in the present invention, a specific example of a preferable combination of a diamine component and an acid anhydride component will be described. When the diamine component is 100 mol%, APB is an essential component as the diamine, preferably 50 to 100 mol%, more preferably 60 to 90 mol%. Moreover, when using together diamine other than APB, it is preferable to use 10-30 mol% of p-PDA, More preferably, 10-30 mol%. Furthermore, when the acid anhydride component is 100 mol%, DSDA is an essential component as the acid anhydride, preferably 50 to 100 mol%, more preferably 60 to 90 mol%. When an acid anhydride other than DSDA is used in combination, at least one of PMDA and BPDA is used in an amount of 10 to 40 mol%, more preferably 20 to 40 mol%.

  The metal layer D is provided on the adhesive layer C. As a method of providing the metal layer D, a method of superimposing a metal foil on the surface of the adhesive layer C and thermocompression bonding, or a method of forming a metal thin film layer is available. is there.

  The metal layer A or the metal layer D may be subjected to a silane coupling agent treatment on the surface on which the polyimide resin layer is laminated. In particular, when thermocompression bonding is performed and the metal layer A or the metal layer D is a stainless steel layer, it is preferable to perform a silane coupling agent treatment. The silane coupling agent is preferably a silane coupling agent having a functional group such as an amino group or a mercapto group, more preferably a silane coupling agent having an amino group. Specific examples include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyl. Examples include trimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like. Among these, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyl It may be at least one selected from dimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine and N-phenyl-3-aminopropyltrimethoxysilane. In particular, 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane are preferable.

  The silane coupling agent is used as a polar solvent solution. As the polar solvent, water or a polar organic solvent containing water is suitable. The polar organic solvent is not particularly limited as long as it is a polar liquid having an affinity for water. Examples of such a polar organic solvent include methanol, ethanol, propanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, dimethylacetamide and the like. The silane coupling agent solution has a concentration of 0.01 to 5% by weight, preferably 0.1 to 2.0% by weight, more preferably 0.5 to 1.0% by weight.

  The silane coupling agent treatment is not particularly limited as long as it is a method in which a solution of a polar solvent containing a silane coupling agent contacts, and a known method can be used. For example, a dipping method, a spray method, a brush coating method or a printing method can be used. The temperature may be 0 to 100 ° C., preferably 10 to 40 ° C. Moreover, as for immersion time, when applying the immersion method, it is effective to process for 10 second-1 hour, Preferably it is 30 second-15 minutes. Dry after treatment. The drying method is not particularly limited, and natural drying, spray drying with an air gun, oven drying, or the like can be used. The drying conditions depend on the type of polar solvent, but are 10 to 150 ° C. for 5 seconds to 60 minutes, preferably 25 to 150 ° C. for 10 seconds to 30 minutes, more preferably 30 to 120 ° C. for 1 minute to 10 minutes. It is.

  When the metal-clad laminate of the present invention is applied as an HDD suspension application, the total thickness of the polyimide resin layer B and the adhesive layer C is preferably in the range of 5 to 50 μm, more preferably 7 to 25 μm. Within the range, more preferably within the range of 8 to 12 μm. Further, each of the metal layer A and the metal layer D is preferably a stainless steel layer having a thickness of 10 to 50 μm, and the metal layer D is preferably a conductive metal layer having a thickness of 0.01 to 50 μm, or metal It is preferable that the layer A is a conductive metal layer having a thickness of 0.1 to 50 μm, and the metal layer D is a stainless steel layer having a thickness of 10 to 50 μm. Furthermore, when the conductor metal layer is formed as a fine flying lead having a circuit width of 40 μm or less, for example, from the viewpoint of in-plane adhesion variation or chemical resistance, the metal-clad laminate of the present invention is used. The layer structure of the body is preferably conductive metal layer / polyimide resin layer / adhesive layer / stainless steel layer. In addition, the range of the material and thickness of each layer is as having mentioned above.

  Next, the manufacturing method of the metal clad laminated body of this invention is demonstrated in detail. The method for producing a metal-clad laminate includes steps a) to d). Steps a) to c) can be performed by the method described above.

  Step d) is a step of providing a metal layer D on the adhesive layer C formed in step c). As a method of providing the metal layer D, there is a method of overlaying a metal foil on the surface of the adhesive layer C and thermocompression bonding (step d1), or a method of forming a metal thin film (step d2).

  In the step d1, a method for thermocompression bonding is not particularly limited, and a known method can be appropriately employed. Examples of the method of laminating the metal foil include a normal hydro press, a vacuum type hydro press, an autoclave pressurizing vacuum press, and a continuous thermal laminator. Among the methods of laminating metal foils, a vacuum hydropress and a continuous thermal laminator are used from the viewpoint that sufficient pressing pressure is obtained, residual volatiles can be easily removed, and oxidation of the metal foil can be prevented. It is preferable to use it.

  Moreover, it is preferable to press the metal foil used as the metal layer D, heating in the range of 150-450 degreeC for thermocompression bonding. More preferably, it exists in the range of 150-400 degreeC. Furthermore, it is preferably in the range of 150 to 380 ° C. From another viewpoint, the temperature may be equal to or higher than the glass transition temperature of the polyimide resin layer or the adhesive layer. The press pressure is usually about 1 to 50 MPa, although it depends on the type of press equipment used.

  As metal foil, iron foil, nickel foil, beryllium foil, aluminum foil, zinc foil, indium foil, silver foil, gold foil, tin foil, zirconium foil, stainless steel foil, tantalum foil, titanium foil, copper foil, lead foil, magnesium foil , Manganese foils and alloy foils thereof. Among these, stainless steel foil, copper foil or copper alloy foil is suitable. The thickness is preferably in the range of 0.1 to 50 μm.

In step d2, the metal thin film layer is formed by a vapor deposition method. The vapor deposition method is not particularly limited. For example, a vacuum vapor deposition method, a sputtering method, an electron beam vapor deposition method, an ion plating method, or the like can be used, and the sputtering method is particularly preferable. This sputtering method includes various methods such as DC sputtering, RF sputtering, DC magnetron sputtering, RF magnetron sputtering, EC sputtering, and laser beam sputtering, but is not particularly limited and can be appropriately employed. Regarding the conditions for forming the metal thin film layer by sputtering, for example, argon gas is used as the sputtering gas, and the pressure is preferably 1 × 10 ^{−2 to 1} Pa, more preferably 5 × 10 ^{−2 to} 5 × 10 ⁻¹ Pa. The sputtering power density is preferably 1 to 100 Wcm ⁻² , more preferably 1 to 50 Wcm ⁻² . In this case, the metal layer comprising the metal thin film layer can be made sufficiently thin. A thick conductive metal layer may be appropriately formed on the thin metal film layer thus formed by electroless plating or electrolytic plating. That is, the thickness can be 0.01 to 50 μm, preferably 0.05 to 5 μm, more preferably 0.1 to 1.0 μm.

  Examples of metals suitable for the metal thin film layer provided by vapor deposition include copper, nickel, chromium, and alloys thereof. The vapor deposition method has an advantage that a metal thin film can be formed, but is not suitable for forming a thick film. Therefore, when the metal thin film layer is thickened to lower the electrical resistance or increase the strength, a relatively thick copper thin film layer may be provided thereon. That is, a metal thin film having a thickness of about 0.001 to 0.5 μm is formed by vapor deposition, and a plating layer may be provided when the thickness is more than that. As the vapor deposition method, a known method such as sputtering or CVD can be employed.

  Formation of the metal thin film by the vapor deposition method preferably uses copper as the thin film layer. Under the present circumstances, the base metal thin film layer which improves adhesiveness more may be provided in a surface treatment polyimide resin layer, and a copper thin film layer may be provided on it. Examples of the base metal thin film layer include nickel, chromium, and an alloy layer thereof. When the base metal thin film layer is provided, the thickness is 1/2 or less, preferably 1/5 or less of the thickness of the copper thin film layer, and is preferably about 1 to 50 nm. This underlying metal thin film layer is also preferably formed by sputtering.

  The copper used here may be alloy copper partially containing other metals. The copper or copper alloy formed by the sputtering method preferably has a copper content of 90% by mass or more, particularly preferably 95% by mass or more. Examples of the metal that copper can contain include chromium, zirconium, nickel, silicon, zinc, and beryllium. Moreover, the copper alloy in which these metals contain 2 or more types may be sufficient.

  The thickness of the metal thin film layer formed in step d2 is preferably in the range of 0.01 to 1.0 μm, preferably 0.05 to 0.5 μm, more preferably 0.1 to 0.5 μm. . When the thin film layer is further thickened, it may be thickened by electroless plating or electrolytic plating. The metal layer formed in this way can be formed into a circuit by a subtractive method or a semi-additive method.

  The metal-clad laminate of the present invention is suitable for double-sided FPC, HDD suspension applications and the like. The metal-clad laminate for HDD suspension of the present invention is the metal-clad laminate of the present invention, wherein one metal layer is made of a stainless steel layer and the other layer is made of a conductive metal layer such as copper.

  The HDD suspension of the present invention can be obtained by processing the metal-clad laminate. As a preferable processing method, there is a method called a TSA method in which a laminate of stainless steel foil-polyimide resin-copper foil is processed into a predetermined shape by etching to form a wiring integrated suspension.

  According to the present invention, the polyimide resin layer is provided with adhesion to the stainless steel foil or the conductive metal foil by a simple treatment, and the polyimide resin layer is substantially a single layer. It becomes easy to control the etching shape of the resin layer. Therefore, it is possible to provide a highly reliable and highly accurate HDD suspension in response to the demand for a HDD suspension with high density and ultra-fine wiring.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this. In the following examples, various evaluations are based on the following unless otherwise specified. Moreover, the symbol of the compound used for the present Example is as having mentioned above.

[Measurement of adhesive strength]
The adhesive strength between the metal layer and the polyimide resin layer is as follows. For the metal-clad laminate, a test piece for measuring 1/8 inch wiring width is prepared by circuit processing, and the metal layer side is attached to the fixing plate. Then, using a tensile tester (Strograph-M1 manufactured by Toyo Seiki Co., Ltd.), the metal foil was peeled off in the 90 ° direction and the strength was measured.
Moreover, it measured similarly about the adhesive strength of the metal layer and polyimide resin layer through an adhesive layer.
The peel strength between the support copper foil and the ultrathin copper foil was fixed to the stainless steel plate with double-sided tape using a Tensilon tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a double-sided tape. The support copper foil was peeled off at a rate of 50 mm / min in the 90 ° direction.

[Measurement of dimensional change rate]
First, a test piece 1 is formed by using a 300 mm square metal-clad laminate and exposing and developing a dry film resist with a target for position measurement at intervals of 200 mm. After measuring the dimensions before etching (normal state) in an atmosphere with a temperature of 23 ± 2 ° C and a relative humidity of 50 ± 5%, etch the copper other than the target of the test piece 1 (liquid temperature 40 # C or less, time 10 minutes or less) ) To form the test piece 2. After being left for 24 ± 4 hours in an atmosphere having a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%, the dimensions after etching are measured in the same manner as in the normal state. The dimensional change rate with respect to the normal state at each of the three positions in the vertical direction and the horizontal direction is calculated, and the average value of each is taken as the dimensional change rate after etching.

[Measurement of polyimide etching shape]
First, a 100 mm square metal-clad laminate was used, the copper foil side was etched, and a via having a diameter of 100 μm was formed as a test piece. Thereafter, using the copper foil as an etching mask, an aqueous solution consisting of 33.5 wt% potassium hydroxide, 11 wt% ethylenediamine and 22 wt% ethylene glycol was used as an etching solution, and the test piece was immersed in an etching solution at 80 ° C. for 10 to 60 seconds. . After immersion, the cross section of the test piece was polished, and the side etching shape of polyimide was observed.

[Measurement of linear thermal expansion coefficient]
The linear thermal expansion coefficient was raised to 255 ° C. at a rate of 20 ° C./min using a thermomechanical analyzer (manufactured by Seiko Instruments Inc.), held at that temperature for 10 minutes, and then at a constant rate of 5 ° C./min. After cooling, the average thermal expansion coefficient (linear thermal expansion coefficient) from 240 ° C. to 100 ° C. during cooling was calculated.

[Measurement of adhesive layer thickness]
The adhesive layer was measured by setting the transmission mode using a scanning transmission electron microscope (manufactured by Hitachi High-Technologies Corporation), observing the cross section of the metal-clad laminate, and confirming the thickness of the adhesive layer.

[Measurement of weight average molecular weight (Mw)]
The weight average molecular weight (Mw) was measured using a column in which four TSK-GEL SUPER HM-Ms manufactured by Tosoh Corporation were connected using HLC-8220GPC manufactured by Tosoh Corporation. A calibration curve for determining the weight average molecular weight was prepared using polystyrene as a standard substance. As a developing solvent, a solution in which lithium bromide and phosphoric acid were mixed with N, N-dimethylacetamide so as to be 0.03 mol / L was used.

Synthesis example 1
In a 500 ml separable flask, 11.7 g APB (0.04 mol) and 2.2 g p-PDA (0.02 mol) were dissolved in 262 g DMAc with stirring. The solution was then charged with 4.4 g PMDA (0.02 mol) and 14.3 g DSDA (0.04 mol) in a stream of nitrogen. Thereafter, stirring was continued for about 4 hours to carry out a polymerization reaction to obtain a viscous polyimide precursor resin p1 solution (solid content concentration 12.0% by weight).
The weight average molecular weight of the obtained polyimide precursor resin p1 was 286,000. Further, the polyimide precursor resin p1, in the above-mentioned formula (1), the divalent group Ar ₁ relative to Ar ₂ 1 mole (Y) is the Ar ₂ relative to 1.33 mole, Ar ₁ 1 mole 2 valent group (Y) is 0.66 moles, divalent groups of Ar ₁ and Ar ₂ relative to Ar ₁ 1 mole (Y) contains 1.99 mol.

Synthesis example 2
In a 1000 ml separable flask, 41.1 g BAPP (0.1 mol) was dissolved in 524 g DMAc with stirring. Next, 32.2 g of BTDA (0.1 mol) was added to the solution in a nitrogen stream. Thereafter, stirring was continued for about 2 hours to conduct a polymerization reaction, and a viscous polyimide precursor resin p2 solution (solid content concentration 13.6% by weight) was obtained.
Here, the polyimide precursor resin p2, in the above-mentioned formula (1), the divalent Ar ₁ relative to Ar ₂ 1 mole group (Y) is 2.0 moles, of Ar ₂ with respect to Ar ₁ 1 mole divalent group (Y) is 1.0 mol, the divalent group of Ar ₁ and Ar ₂ relative to Ar ₁ 1 mole (Y) comprises 3.0 mol.

Production Example 1
In a 500 ml separable flask, 15.77 g m-TB (0.074 mol) and 2.41 g TPE-R (0.008 mol) were dissolved in 264 g DMAc with stirring. Next, 17.82 g PMDA (0.082 mol) was added to the solution under a nitrogen stream. Thereafter, stirring was continued for 4 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamide acid resin solution 1a. The viscosity of the polyamic acid resin solution 1a at 25 ° C. was 29,200 cP. The viscosity was measured at 25 ° C. with a cone plate viscometer (manufactured by Tokimec Co., Ltd.) equipped with a constant temperature water bath. Moreover, the weight average molecular weight (Mw) of the polyamic acid in the resin solution 1a was 210,000.
The obtained polyamic acid resin solution 1a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was removed. A 12 μm polyimide resin film 1b was obtained. It was 12 * 10 < ^-6 > / K when the coefficient of thermal expansion of the obtained polyimide resin film 1b was measured.

Production Example 2
In a 500 ml separable flask, 12.76 g m-TB (0.06 mol) and 5.49 g NBOA (0.024 mol) were dissolved in 268 g DMAc with stirring. Next, 18.31 g of PMDA (0.084 mol) was added to the solution under a nitrogen stream. Thereafter, the polymerization reaction was continued by stirring for 4 hours to obtain a viscous polyamide acid resin solution 2a. The viscosity of the polyamic acid resin solution 2a at 25 ° C. was 30,000 cP. Moreover, the weight average molecular weight (Mw) in the resin solution 2a was 180,000.
The obtained polyamic acid resin solution 2a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was removed. A 12 μm polyimide resin film 2b was obtained. It was 16 * 10 < ^-6 > / K when the coefficient of thermal expansion of the obtained polyimide resin film 2b was measured.

Production Example 3
In a 500 ml separable flask, with stirring, 12.08 g m-TB (0.057 mol), 4.75 g TPE-R (0.016 mol) and 1.63 g DAPE34 (0.008 mol) Was dissolved in 264 g of DMAc. The solution was then added 17.55 g PMDA (0.08 mol) under a stream of nitrogen. Thereafter, stirring was continued for 4 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamide acid resin solution 3a. The viscosity of the polyamic acid resin solution 3a at 25 ° C. was 13,200 cP. Moreover, the weight average molecular weight (Mw) of the polyamic acid in the resin solution 3a was 219,000.
The obtained polyamic acid resin solution 3a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was reduced. A 12 μm polyimide resin film 3b was obtained. It was 22 * 10 < ^-6 > / K when the thermal expansion coefficient of the obtained polyimide resin film 3b was measured.

Production Example 4
In a 500 ml separable flask, with stirring, 12.08 g m-TB (0.057 mol), 4.75 g TPE-R (0.016 mol) and 1.63 g DAPE44 (0.008 mol) Was dissolved in 264 g of DMAc. The solution was then added 17.55 g PMDA (0.08 mol) under a stream of nitrogen. Thereafter, stirring was continued for 4 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamide acid resin solution 4a. The viscosity of the polyamic acid resin solution 4a at 25 ° C. was 19,200 cP. Moreover, the weight average molecular weight (Mw) of the polyamic acid in the resin solution 4a was 235,000.
The obtained polyamic acid resin solution 4a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was reduced. A 12 μm polyimide resin film 4b was obtained. It was 17 * 10 < ^-6 > / K when the thermal expansion coefficient of the obtained polyimide resin film 4b was measured.

Production Example 5
264 g of 12.08 g m-TB (0.057 mol), 4.75 g NBOA (0.016 mol) and 1.63 g DAPE34 (0.008 mol) with stirring in a 500 ml separable flask. In DMAc. The solution was then added 17.55 g PMDA (0.08 mol) under a stream of nitrogen. Thereafter, stirring was continued for 4 hours to carry out a polymerization reaction, thereby obtaining a viscous polyamide acid resin solution 5a. The viscosity of the polyamic acid resin solution 5a at 25 ° C. was 3,400 cP. Moreover, the weight average molecular weight (Mw) of the polyamic acid in the resin solution 5a was 150,000.
The obtained polyamic acid resin solution 5a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was reduced. A 12 μm polyimide resin film 5b was obtained. It was 19 * 10 < ^-6 > / K when the coefficient of thermal expansion of the obtained polyimide resin film 5b was measured.

Production Example 6
In a 500 ml separable flask, 30.3 g of 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane (DANPG) (0.057 mol) was dissolved in 352 g of DMAc with stirring. . The solution was then added with 9.3 g PMDA (0.04 mol) and 20.5 g BTDA (0.06 mol) under a stream of nitrogen. Thereafter, stirring was continued for about 3 hours to conduct a polymerization reaction, thereby obtaining a viscous polyamic acid resin solution 6a.
The obtained polyamic acid resin solution 6a was applied onto a substrate, dried at 130 ° C. for 5 minutes, then heated to 360 ° C. over 15 minutes to complete imidization, the substrate was removed, and the thickness was reduced. A 12 μm polyimide resin film 6b was obtained. It was 35 * 10 < ^-6 > / K when the thermal expansion coefficient of the obtained polyimide resin film 6b was measured.

Production Example 7
A silane coupling agent solution was prepared by mixing 5 g of 3-aminopropyltrimethoxysilane, 500 g of methanol and 2.5 g of water and stirring for 2 hours. After pre-washing stainless steel foil 1 (SUS304 H-TA, manufactured by Nippon Steel Corp., thickness 20 μm) for 30 seconds in a silane coupling agent solution (liquid temperature of about 20 ° C.), the steel foil was once pulled up into the atmosphere to remove excess The liquid was dropped. Then, it was dried by blowing compressed air for about 15 seconds. Then, heat processing were performed for 30 minutes at 110 degreeC, and the stainless steel foil 2 of a silane coupling agent process was obtained.

Reference example 1
A polyimide precursor resin solution s1 was prepared by adding 478 g of DMAc to 22 g of the polyimide precursor resin p1 solution of Synthesis Example 1 and adjusting the solid content concentration to 0.5 wt%.
After applying the polyimide precursor resin solution s1 to a wet thickness of 70 μm on a stainless steel substrate using a lip coater, the polyimide precursor resin solution s1 is dried at 130 ° C. for 2 minutes and heated to 360 ° C. over 15 minutes to complete imidization. By doing so, resin layer S1 was obtained. The thickness of this resin layer was 0.1 μm.

Reference example 2
A polyimide precursor resin solution s2 having a solid content concentration adjusted to 2% by weight was prepared by adding 407 g of DMAc to 93 g of the polyimide precursor resin p1 solution of Synthesis Example 1.
A polyimide precursor resin solution s2 is applied on a stainless steel substrate using a lip coater with a wet thickness of 20 μm, dried at 130 ° C. for 2 minutes, and heated to 360 ° C. over 15 minutes to complete imidization. By doing so, resin layer S2 was obtained. The thickness of this resin layer was 0.1 μm.
The polyimide resin constituting the resin layer S1 and the resin layer S2 were both thermoplastic polyimide resins.

Reference example 3
A polyimide precursor resin solution s3 in which 458 g of DMAc was added to 42 g of the polyimide precursor resin p2 solution of Synthesis Example 2 to adjust the solid content concentration to 1 wt% was prepared.
After applying polyimide precursor resin solution s3 with a wet thickness of 50 μm on a stainless steel substrate using a lip coater, it is dried at 130 ° C. for 2 minutes and heated to 360 ° C. over 15 minutes to complete imidization. As a result, a resin layer S3 was obtained. The thickness of this resin layer was 0.1 μm.

The resin solution 1a obtained in Production Example 1 was applied to the stainless steel foil 1 using an applicator and dried at 130 ° C. for 5 minutes to produce a polyamic acid layer so that the thickness after curing was 12 μm.
On the polyamic acid layer, the polyimide precursor resin solution s1 obtained in Reference Example 1 was applied with a wet thickness of 70 μm using a comma coater, then dried at 130 ° C. for 2 minutes, and 360 ° C. over 15 minutes. Until the temperature was raised to complete imidization, and a laminate L1 composed of a stainless steel layer, a polyimide resin layer and an adhesive layer was produced. The thickness of the adhesive layer of this laminate was 0.8 μm. In addition, in the cross-sectional observation of the adhesive layer with a transmission electron microscope, no interface in the adhesive layer was observed, and therefore it is estimated that almost 100% of the adhesive layer is a modified layer derived from the impregnated layer. The volume ratio of the modified layer in the adhesive layer in the present invention is obtained directly by observing the cross section of the adhesive layer with a transmission electron microscope, but the boundary between the modified layer and the thermoplastic polyimide resin layer C ′ is unclear. In some cases, it can also be determined based on the following idea. When the modified layer B ′ is not formed at all and only the polyimide resin layer B and the thermoplastic polyimide resin layer C ′ are present, the calculated thickness of the adhesive layer is observed because it is the thickness of the thermoplastic polyimide resin layer C ′. From the thickness of the adhesive layer, the thickness of the modified layer B ′ and the volume ratio of the modified layer in the adhesive layer can be roughly calculated by the following equation. For example, when considering the thickness (0.1 μm) of the resin layer S1 of Reference Example 1 and the thickness (0.8 μm) of the adhesive layer of Example 1, the volume ratio of the modified layer is calculated as 88% or more by the following formula: It becomes. [(0.8-0.1) /0.8] × 100.
Electrolytic copper foil 1 (manufactured by Mitsui Kinzoku Co., Ltd., NS-VLP foil, copper foil thickness 9 μm) is superimposed on the surface of the adhesive layer of the obtained laminate, and is 20 MPa and temperature 370 by a high-performance high-temperature vacuum press. The metal-clad laminate 1 composed of a stainless steel layer, an insulating resin layer, and a copper foil layer was obtained by thermocompression bonding under the conditions of ° C and a press time of 1 minute. The adhesive strength on the stainless steel side and the copper foil side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 1 was excellent in adhesive strength and dimensional stability, and the shape of the insulating resin layer of the etching solution was not particularly problematic. What is the adhesive strength? 0.5 kN / m or more was regarded as no problem.

The resin solution 2a obtained in Production Example 2 was applied to the electrolytic copper foil 1 using an applicator and dried at 130 ° C. for 5 minutes to produce a polyamic acid layer so that the thickness after curing was 12 μm.
On the polyamic acid layer, the polyimide precursor resin solution s1 of Reference Example 1 was applied with a wet thickness of 70 μm using a comma coater, dried at 130 ° C. for 2 minutes, and then heated to 360 ° C. over 15 minutes. Thus, imidization was completed to produce a laminate L2 composed of a copper foil layer, a polyimide resin layer, and an adhesive layer. The thickness of the adhesive layer of this laminate was 0.8 μm.
A metal-clad laminate composed of a copper foil layer, an insulating resin layer, and a stainless steel layer is laminated with the stainless steel foil 1 on the surface of the adhesive layer of the obtained laminate, and heat-pressed in the same manner as in Example 1. Body 2 was obtained. The adhesive strength on the stainless steel side and the copper side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 2 was excellent in adhesive strength and dimensional stability, and there was no particular problem with the shape of the insulating resin layer of the etchant.

The resin solution 3a obtained in Preparation Example 3 was used as an ultrathin copper foil 1 with a support copper foil (manufactured by Nihon Electrolysis Co., Ltd., YSNAP-3B, support copper foil thickness 18 μm, ultrathin copper foil thickness 1 μm, inorganic release) Layer) was applied using an applicator and dried at 130 ° C. for 5 minutes to prepare a polyamic acid layer so that the thickness after curing was 12 μm.
On the polyamic acid layer, the polyimide precursor resin solution s1 of Reference Example 1 was applied with a wet thickness of 70 μm using a comma coater, dried at 130 ° C. for 2 minutes, and then heated to 360 ° C. over 15 minutes. Thus, imidization was completed, and a laminate L3 with a support composed of a copper foil layer, a polyimide resin layer, and an adhesive layer was produced. The thickness of the adhesive layer of this laminate was 0.8 μm.
With the support composed of a copper foil layer, an insulating resin layer, and a stainless steel layer, the stainless steel foil 2 is superposed on the surface of the adhesive layer of the obtained laminate and heat-pressed in the same manner as in Example 1. The metal-clad laminate 3 was obtained, and the support copper foil was peeled off to obtain a metal-clad laminate 3. The adhesive strength on the stainless steel side and the copper side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 3 was excellent in adhesive strength and dimensional stability, and there was no particular problem with the shape of the insulating resin layer of the etchant. The peel strength between the support copper foil and the ultrathin copper foil was 10 N / m, and the laminate after peeling the support copper foil was free of wrinkles and warpage and had a good appearance.

The resin solution 4a obtained in Production Example 4 was applied to the stainless steel foil 2 using an applicator and dried at 130 ° C. for 5 minutes to produce a polyamic acid layer so that the thickness after curing was 12 μm.
On the polyamic acid layer, the polyimide precursor resin solution s1 obtained in Reference Example 1 was applied with a wet thickness of 70 μm using a comma coater, then dried at 130 ° C. for 2 minutes, and 360 ° C. over 15 minutes. Until the temperature was raised to complete imidization, and a laminate L4 composed of a stainless steel layer, a polyimide resin layer, and an adhesive layer was produced. The thickness of the adhesive layer of this laminate was 0.8 μm.
It was set in an RF magnetron sputtering apparatus (ANELVA; SPF-332HS) so that a metal raw material was formed on the surface of the obtained laminate on the resin layer side, and the inside of the tank was depressurized to 3 × 10 ⁻⁴ Pa. Thereafter, argon gas was introduced to make the degree of vacuum 2 × 10 ⁻¹ Pa, and plasma was generated by an RF power source. A nickel: chromium alloy layer [ratio 8: 2, 99.9 wt%, hereinafter referred to as a nichrome layer (first sputtering layer)] was formed on the polyimide film by this plasma so as to have a film thickness of 30 nm. After forming the nichrome layer, a copper layer (99.99 wt%) was further formed on the nichrome layer by sputtering in the same atmosphere to form a second sputtering layer.
Next, a copper plating layer having a thickness of 8 μm was formed in an electrolytic plating bath using the sputtered film (second sputtering layer) as an electrode. As an electrolytic plating bath, a copper sulfate bath (copper sulfate 100 g / L, sulfuric acid 220 g / L, chlorine 40 mg / L, anode is phosphorus-containing copper) is used, and a plating film is formed at a current density of 2.0 A / dm ² . did. After plating, it was washed with sufficient distilled water and dried. In this way, a metal-clad laminate 4 composed of a stainless steel layer, an insulating resin layer, a nichrome layer, a copper sputter layer, and an electroplated copper layer was obtained. The adhesive strength on the stainless steel side and the copper side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 4 was excellent in adhesive strength and dimensional stability, and the shape of the insulating resin layer after etching was also good.

The resin solution 5a obtained in Production Example 5 was applied to the stainless steel foil 1 using an applicator and dried at 130 ° C. for 5 minutes to produce a polyamic acid layer so that the thickness after curing was 12 μm.
On the above-mentioned polyamic acid layer, the polyimide precursor resin solution s2 obtained in Reference Example 2 was applied with a wet thickness of 20 μm using a comma coater, then dried at 130 ° C. for 2 minutes, and 360 ° C. over 15 minutes. Until the temperature was raised to complete imidization, and a laminate L5 composed of a stainless steel layer, a polyimide resin layer and an adhesive layer was produced. The thickness of the adhesive layer of this laminate was 0.8 μm.
The electrolytic copper foil 1 is overlaid on the surface of the adhesive layer of the obtained laminate, and is heat-pressed in the same manner as in Example 1 to form a metal tension composed of a stainless steel layer, an insulating resin layer, and a copper foil layer. A laminate 5 was obtained. The adhesive strength on the stainless steel side and the copper foil side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 5 was excellent in adhesive strength and dimensional stability, and the shape of the insulating resin layer of the etching solution was not particularly problematic.

Example 1 is the same as Example 1 except that the polyimide precursor resin solution s3 obtained in Reference Example 3 was applied with a wet thickness of 50 μm instead of applying the polyimide precursor resin solution s1 with a wet thickness of 70 μm in Example 1. Thus, a laminated plate L6 was produced. The thickness of the adhesive layer of this laminate was 0.5 μm.
A metal-clad laminate composed of a stainless steel layer, an insulating resin layer, and a copper foil layer by heat-pressing the electrolytic copper foil 1 on the surface of the obtained laminate L6 on the resin layer side in the same manner as in Example 1. 6 was obtained. The adhesive strength on the stainless steel side and the copper foil side and the etching shape of the insulating resin layer were evaluated. The results are shown in Table 1. The obtained metal-clad laminate 6 was excellent in adhesive strength and dimensional stability, and there was no particular problem with the shape of the insulating resin layer of the etchant.
In Examples 2 to 6, in the cross-sectional observation of the adhesive layer using a transmission electron microscope, the interface in the adhesive layer was not recognized, so almost 100% of the adhesive layer was a modified layer derived from the impregnated layer. Presumed to be.

Comparative Example 1
The resin solution 1a of Production Example 1 was applied to the stainless steel foil 1 using an applicator, dried at 130 ° C. for 5 minutes, and then heated to 360 ° C. over 15 minutes to complete imidization. A laminate having a 12 μm thick polyimide resin layer laminated thereon was produced. Electrolytic copper foil 1 is superposed on the surface of the obtained laminate on the resin layer side, and heat-pressed with a high-performance high-temperature vacuum press at 20 MPa, temperature of 370 ° C., and press time of 1 minute, and metal-clad laminate Body 7 was obtained. The adhesive strength on the copper side was 0.1 kN / m or less.

Comparative Example 2
Instead of coating the polyimide precursor resin solution s1 in Example 1 with a wet thickness of 70 μm, the polyimide precursor resin p1 solution obtained in Synthesis Example 1 (solid content concentration 12.0% by weight) was cured. A laminate was produced in the same manner as in Example 1 except that the coating was applied so that the thickness of the laminate was 2 μm. The thickness of the adhesive layer at this time was 2.0 μm. The electrolytic copper foil 1 was superposed on the surface of the obtained laminate on the adhesive layer side, and a metal-clad laminate 8 was produced in the same manner as in Example 1. The obtained metal-clad laminate 8 had no problem in adhesive strength and dimensional stability, but unevenness occurred in the shape of the insulating resin layer after etching.

Comparative Example 3
The resin solution 6a obtained in Production Example 6 was applied to the stainless steel foil 1 using an applicator, dried at 130 ° C. for 5 minutes, and then heated to 360 ° C. over 15 minutes to complete imidization, A laminate was produced in which a polyimide resin layer having a thickness of 12 μm was laminated on the stainless steel layer. Electrolytic copper foil 1 is superposed on the surface of the obtained laminate on the resin layer side, and heat-pressed with a high-performance high-temperature vacuum press at 20 MPa, temperature of 370 ° C., and press time of 1 minute, and metal-clad laminate Body 9 was obtained. Although there was no problem in the adhesive strength on the copper side, the dimensional change rate was -0.80%, and the warpage of the laminate occurred.

Comparative Example 4
The resin solution 4a obtained in Production Example 4 was applied to the stainless steel foil 2 using an applicator, dried at 130 ° C. for 5 minutes, and then heated to 360 ° C. over 15 minutes to complete imidization, A laminate was produced in which a polyimide resin layer having a thickness of 12 μm was laminated on the stainless steel layer. A metal-clad laminate was set in an RF magnetron sputtering apparatus so that a metal raw material was formed on the surface of the resulting laminate on the resin layer side, and subjected to sputtering and electrolytic plating in the same manner as in Example 4. 10 was obtained. The adhesive strength on the copper side was 0.2 kN / m.

Comparative Example 5
Instead of coating the polyimide precursor resin solution s1 in Example 1 with a wet thickness of 70 μm, the polyimide precursor resin p1 solution obtained in Synthesis Example 1 (solid content concentration 12.0% by weight) was cured. A laminate was produced in the same manner as in Example 1 except that the coating was performed so that the thickness of the laminate was 0.5 μm. At this time, the thickness of the adhesive layer was 0.5 μm, and the presence of the modified layer was not observed in the adhesive layer. In addition, from the measured values of the theoretical thickness F0 (μm) after imidization of the polyamic acid layer, the thickness F1 (μm) of the polyimide resin layer of the laminate and the thickness T (μm) of the adhesive layer, The ratio (%) of the quality layer was calculated as [T− (F1−F0)] / T × 100 (%), and it was less than 1%. Here, “theoretical thickness after imidization of the polyamic acid layer” means that after the polyamic acid layer is formed, the polyamic acid layer is simply imidized without applying the precursor solution of the thermoplastic polyimide resin. This is the thickness of the layer.
The electrolytic copper foil 1 was superposed on the surface of the obtained laminate on the adhesive layer side, and a metal-clad laminate 11 was produced in the same manner as in Example 1. The adhesive strength on the copper side was 0.4 kN / m.

The above results are summarized in Table 1. In Table 1, the resin layer (μm) indicates the total thickness (μm) of the polyimide resin layer and the adhesive layer of the obtained metal-clad laminate, and the adhesive layer (μm) is the adhesive layer or Indicates the thickness (μm) of the adhesive layer, CTE (ppm / K) indicates the coefficient of thermal expansion (× 10 ^-6 / K) of the polyimide resin layer, and the A side of the adhesive strength refers to the metal layer A and the polyimide Indicates the adhesive strength of the resin layer, the D side of the adhesive strength indicates the adhesive strength between the metal layer D and the adhesive layer C, and the dimensional change rate (%) indicates the dimensional change rate (%) after etching. The shape indicates the shape of the insulating resin layer after etching.

Claims (9)

A metal-clad laminate composed of a metal layer A, a polyimide resin layer B, an adhesive layer C and a metal layer D in this order,
The polyimide resin layer B is a single layer having a thickness of 5 to 50 μm, and the linear thermal linear expansion coefficient is 10 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K).
Adhesive layer C is a layer containing a thermoplastic polyimide resin, and has a thickness of 0.001 to 1.0 μm, and a polyimide resin precursor in which 50% or more of the adhesive layer C forms a polyimide resin layer B as a volume fraction. A modified layer formed by impregnating a precursor solution of a thermoplastic polyimide resin into a polyamic acid layer as a body, drying and heat-treating,
A metal-clad laminate characterized by the following.   The metal-clad laminate according to claim 1, wherein the metal layer A is a conductive metal layer having a thickness of 0.1 to 50 µm, and the metal layer D is a stainless steel layer having a thickness of 10 to 50 µm.   The metal-clad laminate according to claim 1, wherein the metal layer A is a stainless steel layer having a thickness of 10 to 50 µm, and the metal layer D is a conductive metal layer having a thickness of 0.01 to 50 µm. The metal-clad laminate according to any one of claims 1 to 3, wherein the precursor of the thermoplastic polyimide resin has a structural unit represented by the following formula (1).

(In formula (1), Ar ₁ represents a divalent aromatic group represented by formula (2), formula (3) or formula (4), and Ar ₂ represents formula (5) or formula (6). In the formulas (2) to (4) and (6), R ₁ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms. , N independently represents an integer of 0 to 4, and X and W independently represent a single bond or —C (CH ₃ ) ₂ —, — (CH ₂ ) m—, —O—, —S—, —CO—. , —SO ₂ —, —NH— or —CONH—, wherein m represents an integer of 1 to 5. And in 1 mol of Ar ₁ , — (CH ₂ ) m—, — (Inclusive of 1 to 3 mol of divalent groups selected from O-, -S-, -CO-, -SO _2- , -NH- and -CONH-) The metal-clad laminate according to claim 4, wherein in the formula (1), Ar ₂ is a tetravalent aromatic group represented by the formula (6) and W is -SO _2- .   A metal-clad laminate for an HDD suspension, comprising the metal-clad laminate according to claim 2.   An HDD suspension obtained by processing the metal-clad laminate for an HDD suspension according to claim 6. 8. The method for producing a metal-clad laminate, wherein the following steps a) to d) are essential for producing the metal-clad laminate according to any one of claims 1 to 7.
a) A low thermal expansion polyimide resin precursor solution having a linear thermal expansion coefficient of 10 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K) is applied onto the metal layer A and dried to obtain a thickness of 5 Forming a 50 μm polyamic acid layer;
b) A precursor solution of a thermoplastic polyimide resin having a solid content concentration of 0.1 to 3% by weight is applied to the layer on the surface side of the polyamic acid layer with a thickness of 1.0 μm or more. Impregnating the precursor solution into the inside from the surface of the polyamic acid layer,
c) drying and heat-treating the layer containing the polyamic acid layer and the precursor of the thermoplastic polyimide resin to form an adhesive layer C having a thickness of 0.001 to 1.0 μm; and
d) A step of forming a metal layer D on the surface of the adhesive layer C.   The metal layer D can be formed on the surface of the adhesive layer C. d1) The metal foil is superimposed on the surface of the adhesive layer C and thermocompression bonded, or d2) The metal thin film layer is formed on the surface of the adhesive layer C. The manufacturing method of the metal-clad laminated body of Claim 8 made by making it vapor-deposit.