JP2012006200A - Polyimide metal laminate and printed wiring board obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide metal laminate which is used as a two-layer flexible substrate having excellent heat resistance and has excellent connection reliability when bent in electronic equipment and to provide a printed wiring board obtained by using the polyimide metal laminate.SOLUTION: The polyimide metal laminate 1 includes: a non-thermoplastic polyimide film 13; an adhesive polyimide layer 14 arranged on at least one side of the non-thermoplastic polyimide film 13; and a metal layer 12 arranged on the adhesive polyimide layer 14. The non-thermoplastic polyimide film 13 has ≤4 GPa elastic modulus, the adhesive polyimide layer 14 has 1-3 μm thickness and the metal layer 12 has ≤1.0 μm ten-point average roughness Rz on the contact surface abutted on the adhesive polyimide layer 14.

Description

  The present invention relates to a polyimide metal laminate used for flexible wiring boards and the like.

  In recent years, along with higher performance of electronic devices, technological advances such as miniaturization and higher functionality have been demanded, and electronic components that make up these devices are also required to have higher performance in terms of electrical characteristics, mechanical characteristics, heat resistance, etc. It has been.

  2. Description of the Related Art Conventionally, printed wiring boards in which a circuit is formed on a mounting surface for electronic components and semiconductor chips have been widely used for mounting electronic components and semiconductor chips. Conventionally, a copper clad laminate in which a metal foil and a heat resistant film (for example, a polyimide film) are laminated via a thermosetting adhesive such as an epoxy resin has been used. The copper clad laminate material used for such purposes is generally called a three-layer flexible substrate.

  However, the three-layer flexible substrate uses an epoxy resin as an adhesive, so there is a problem in heat resistance, and there is a problem in a process requiring high temperature such as a bonding process between an electrode on a substrate and a semiconductor chip using solder or ultrasonic waves. There was a problem that occurred.

  As a means for solving these problems, various materials based on a method of forming a metal layer on a polyimide layer without using a low heat-resistant thermosetting adhesive such as an epoxy resin have been put on the market. In contrast to a three-layer flexible substrate, it is called a two-layer flexible substrate.

  As electronic devices have become lighter, thinner, more sophisticated, and more sophisticated in recent years, there has been a strong demand for miniaturization and easy folding of printed wiring boards. For example, a mobile phone which is one of electronic devices is required to have excellent resistance to repeated bending of the hinge portion. By adjusting the elastic modulus and bending rigidity of the coverlay film, the hinge having high flexibility A mobile phone using a part is disclosed (Patent Document 1).

  In addition, as electronic devices become lighter, thinner, and smaller, it is required to be incorporated in an electronic device in a state where a printed wiring board is bent in order to effectively use the space in the electronic device. As a printed wiring board that is easy to bend, a flexible printed wiring board having an adjusted stiffness value is disclosed (Patent Document 2).

  However, the printed wiring board incorporated in the electronic device in a bent state has a repulsive force to return to the original, and the connection reliability of the printed wiring board component mounting part and the joint part via the anisotropic conductive film There was a problem of insufficient sex.

JP 2006-261444 A JP 2007-208087 A

  The present invention has been made in view of such a point, and in a two-layer flexible substrate excellent in heat resistance, a polyimide metal laminate excellent in connection reliability in a state folded in an electronic device and a print using the same An object is to provide a wiring board.

As a result of intensive studies to solve the above problems, the present inventors have made the present invention. That is, the present invention is as follows.

  The polyimide metal laminate of the present invention includes a non-thermoplastic polyimide film, an adhesive polyimide layer provided on at least one surface of the non-thermoplastic polyimide film, and a metal layer provided on the adhesive polyimide layer. The elastic modulus of the non-thermoplastic polyimide film is 4 GPa or less, the thickness of the adhesive polyimide layer is 1 μm to 3 μm, and the metal layer has a contact surface in contact with the adhesive polyimide layer. The point average roughness Rz is 1.0 μm or less.

  In the polyimide metal laminate of the present invention, it is preferable that the test value for the fold resistance is one or more.

  The printed wiring board of the present invention is characterized in that a circuit is formed on the metal layer of the polyimide metal laminate.

  A printed wiring board with a cover lay according to the present invention includes the printed wiring board and a cover lay provided on a circuit forming surface of the printed wiring board.

  In the printed wiring board with a coverlay of the present invention, it is preferable that the test value of the fold resistance is 4 times or more.

  In the printed wiring board with a coverlay of the present invention, the coverlay preferably has an elastic modulus of 4 GPa or less.

  ADVANTAGE OF THE INVENTION According to this invention, in the two-layer flexible substrate excellent in heat resistance, the polyimide metal laminated body which is excellent in the connection reliability in the state bent in the electronic device, and a printed wiring board using the same can be provided. .

(A), (b) is a cross-sectional schematic diagram of the polyimide metal laminated body which concerns on embodiment of this invention.

  The present invention relates to a polyimide metal laminate having excellent heat resistance and excellent connection reliability in a bent state, and a printed wiring board using the same.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
First, with reference to FIG. 1, the laminated structure of the polyimide metal laminated body which concerns on this Embodiment is demonstrated. 1A and 1B are schematic cross-sectional views of a polyimide metal laminate according to an embodiment of the present invention. As shown in FIG. 1A, the polyimide metal laminate 1 according to the present embodiment includes a polyimide layer 11 and a metal layer 12 provided on one main surface of the polyimide layer 11. The polyimide layer 11 is provided between the non-thermoplastic polyimide film 13 and the non-thermoplastic polyimide film 13 and the metal layer 12, and an adhesive polyimide layer 14 that adheres the non-thermoplastic polyimide film 13 and the metal layer 12. including. In addition, as shown in FIG.1 (b), it is good also as a structure which further provides the metal layer 15 on the other main surface of the polyimide layer 11. FIG. In this case, the polyimide layer 11 includes an adhesive polyimide layer 16 that is provided between the non-thermoplastic polyimide film 13 and the metal layer 15 and adheres the non-thermoplastic polyimide film 13 and the metal layer 15.

  Thus, in the polyimide metal laminate according to the present embodiment, the metal layers 12 and 15 are provided on one or both sides of the polyimide layer 11, and the polyimide layer 11 includes the non-thermoplastic polyimide film 13 and the metal layer 12. And an adhesive polyimide layer 16 capable of thermocompression bonding the non-thermoplastic polyimide film 13 and the metal layer 15. And the non-thermoplastic polyimide film 13 and the metal layers 12 and 15 become the laminated body couple | bonded through the adhesive polyimide layers 14 and 16. FIG.

(Non-thermoplastic polyimide film)
As the non-thermoplastic polyimide film, any known polyimide or polyimide obtained by imidizing polyamic acid which is a polyimide precursor can be applied. The polyamic acid used in the present invention can be usually obtained by dissolving and reacting at least one tetracarboxylic dianhydride and at least one diamine in a substantially equimolar amount in an organic solvent.

  For the imidization of the polyamic acid, either a thermal cure method or a chemical cure method is used. The thermal cure method is a method in which an imidization reaction proceeds by heating alone without using a dehydrating ring-closing agent or the like. In addition, the chemical cure method includes a polyamic acid organic solvent solution, a chemical conversion agent (dehydrating agent) represented by acid anhydrides such as acetic anhydride, and tertiary amines such as isoquinoline, β-picoline, and pyridine. This is a method in which a catalyst represented by A chemical cure method and a thermal cure method can be used in combination. The reaction conditions for imidization can vary depending on the type of polyamic acid, film thickness, thermal curing method and / or chemical curing method.

  A conventionally well-known thing can be used as a tetracarboxylic dianhydride component in a non-thermoplastic polyimide film. Specifically, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester, 3 ', 4'-biphenyltetracarboxylic acid, pyromellitic acid, benzophenonetetracarboxylic acid, oxydiphthalic acid, diphenylsulfonetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, cyclobutanetetracarboxylic acid, cyclohexanetetracarboxylic And acid dianhydrides such as acids. From the viewpoint of heat resistance such as thermal expansion coefficient and glass transition temperature, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic It is preferable to use acid-1,4-phenylene ester dianhydride, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride. Moreover, each tetracarboxylic dianhydride may be used alone or in combination. From the viewpoint of elastic modulus, it is more preferable to use pyromellitic dianhydride.

  A conventionally well-known thing can be used as a diamine component in a non-thermoplastic polyimide film. For example, paraphenylenediamine, metaphenylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, 2,2-dimethyl-4,4-diaminobiphenyl, 1, 3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis (4-aminophenoxyphenyl) propane, bis (4- (4-aminophenoxy) phenyl) Examples include sulfone and bis (4- (3-aminophenoxy) phenyl) sulfone. Each diamine may be used alone or in combination. From the viewpoint of heat resistance such as thermal expansion coefficient and glass transition temperature, and from the viewpoint of elastic modulus, it is preferable to use paraphenylenediamine and 4,4'-diaminodiphenyl ether in combination.

  A particularly preferred combination of an acid dianhydride component and a diamine component for a non-thermoplastic polyimide film is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, p-phenylenebis. A combination of at least one acid dianhydride selected from the group consisting of (trimellitic acid monoester acid anhydride) and 4,4′-diaminodiphenyl ether and / or paraphenylenediamine. Polyimides synthesized by combining these monomers exhibit excellent properties such as moderate elastic modulus, dimensional stability, and low water absorption, and are suitable for use in the polyimide metal laminate according to the present invention.

  Preferable solvents for synthesizing the polyamic acid include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. These solvents can be used alone or in combination.

  Lubricants and antioxidants such as inorganic or organic fillers and organic phosphorus compounds can be added to the non-thermoplastic polyimide film by known methods.

  Further, the surface of the non-thermoplastic polyimide film may be subjected to a known and conventional treatment such as plasma treatment, corona treatment, sand blast treatment and the like.

  Further, the elastic modulus of the non-thermoplastic polyimide film is preferably 4 GPa or less from the viewpoint of ease of bending. When the elastic modulus is 4 GPa or less, the non-thermoplastic polyimide film is easily bent and the connection reliability in the bent state is improved. The elastic modulus is preferably 3.8 GPa or less. Moreover, 3.0 GPa or more is preferable from a viewpoint of the ease of handling at the time of non-thermoplastic polyimide film travel.

  A commercially available polyimide film can also be used as the non-thermoplastic polyimide film. For example, Upilex (registered trademark) S, Upilex (registered trademark) SGA, Upilex (registered trademark) SN (trade name), Kapton (registered trademark) H, Kapton (registered trademark) V, Kapton (registered trademark) ) EN (made by Toray DuPont, trade name), Apical (registered trademark) AH, Apical (registered trademark) NPI, Apical (registered trademark) NPP, Apical (registered trademark) HP, Apical (registered trademark) FPI (Kaneka Corporation) Product name).

  The thickness of the non-thermoplastic polyimide film is preferably 2 μm to 125 μm. Furthermore, from a viewpoint that it is easy to bend and it is easy to handle, 5 micrometers-50 micrometers are preferable.

(Adhesive polyimide layer)
The adhesive polyimide layer is coated with a soluble polyimide solution, and then the solvent is dried by heating, or after applying the polyamic acid solution and drying the solvent by heating, amidic acid is heated or combined with an imidization catalyst. It is obtained by ring-closing imidization of the site. It is preferable to use a soluble polyimide solution from the viewpoint that it is easy to obtain thickness accuracy because the step after coating only needs to dry the solvent.

  The structure of the soluble polyimide is not particularly limited as long as it can be bonded to the metal layer (metal foil) under heat and pressure, and a known and conventional one can be used. From the viewpoint of adhesion to the copper foil, bicyclo [2,2 , 2] octo-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3,5-diaminobenzoic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, A structure containing 1,3-bis (3-aminophenoxy) benzene as a component is preferable. When two or more different tetracarboxylic dianhydride components and / or diamine components are used, the soluble polyimide obtained therefrom may have a random structure or a block structure. Moreover, the terminal of these polymers may be sealed with monoamine or acid anhydride. In the present invention, “soluble” means that 1% by mass or more dissolves in a solvent that can be used as a coating agent when dissolved in a temperature range of room temperature to 20 ° C. to 100 ° C.

  The structure of the polyamic acid is not particularly limited as long as the polyimide obtained by imidizing it can be bonded to the metal foil under heat and pressure, and any known and conventional one can be used. The imidization is performed by a heat cure method or a combination of a heat cure method and a chemical cure method. When two or more different tetracarboxylic dianhydride components and / or diamine components are used, the polyimide after imidization obtained therefrom may have a random structure or a block structure. Moreover, the terminal of these polymers may be sealed with monoamine or acid anhydride.

  The soluble polyimide solution or polyamic acid solution used for the adhesive polyimide layer may be added with an alkylated melamine resin or an alkylated urea resin for the purpose of improving adhesion to a non-thermoplastic polyimide film, and the physical properties are impaired. Other heat resistant resins such as polycarbonate, polyarylate, polyamide, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylsulfide, modified polyphenyleneoxide, polyamideimide, polyetherimide, polyester, It is also possible to mix an appropriate amount of cyanate ester or the like.

  Moreover, as long as the physical properties are not impaired, fillers such as a dehydrating agent and silica, and surface modifiers such as a silane coupling agent and a titanate coupling agent may be further added as additives. These fillers may be previously treated with the above surface modifier.

  The glass transition temperature of the adhesive polyimide layer is preferably 183 ° C. or higher when measured by TMA. In a printed wiring board, solder is generally used for connection with wiring. Since the melting point of eutectic solder is 183 ° C., the glass transition temperature of the adhesive polyimide layer is preferably higher than that. The melting point of the solder is more preferably 10 ° C. or higher, and the glass transition temperature of the adhesive polyimide layer is more preferably 200 ° C. or higher. From the viewpoint of productivity, it is more preferably 200 ° C. or higher and 300 ° C. or lower.

  The thickness of the adhesive polyimide layer is preferably 1 μm or more from the viewpoint of quality. In addition, when bonding with a metal layer by hot roll lamination or double belt press, defects such as scratches and distortions on the roll and belt are transferred to the polyimide metal laminate, and it is avoided that defects appear in the polyimide metal laminate. To 1 μm or more is preferable. From the viewpoint of heat resistance as the multilayer polyimide layer, the thickness of the adhesive polyimide layer is preferably 3 μm or less. In a printed wiring board, solder is generally used for connection with wiring, and a soldering iron is used. The temperature of the soldering iron is 300 ° C. or higher, and the printed wiring board is required to have heat resistance of 300 ° C. or higher. When the adhesive polyimide layer is thick, the adhesive polyimide layer is softened at a temperature equal to or higher than the glass transition temperature, so that circuit sinking or the like occurs. Therefore, the thinner adhesive polyimide layer is preferable from the viewpoint of suppressing circuit sinking. The thickness of the adhesive polyimide layer is preferably 1 μm or more and 3 μm or less.

(Metal layer)
As the metal layer used in the polyimide metal laminate, known metal foils and alloy foils can be applied as long as they meet the purpose of the present invention. From the viewpoint of wiring formability, electrolytic copper foil, rolled copper foil, carrier A copper foil is preferred. Furthermore, from the viewpoint of flexibility, that is, connection reliability in a bent state, a copper foil having a thickness of 18 μm or less is preferable. The copper foil surface may be subjected to a surface treatment such as a roughening treatment, a known plating treatment such as nickel or zinc, a chromate treatment, an aluminum alcoholate treatment, an aluminum chelate treatment, or a silane coupling agent treatment.

  The metal layer in contact with the adhesive polyimide layer of the polyimide metal laminate is the metal layer on the contact surfaces 12a and 15a (see FIGS. 1A and 1B) in contact with the metal layer and the adhesive polyimide layer during bending. Stress concentration acts on the roughened portion, and the metal layer breaks starting from this portion. For this reason, it is preferable that the ten-point average roughness of the contact surface of the metal layer in contact with the adhesive polyimide layer is 1.0 μm or less from the viewpoint of avoiding breakage of the metal layer. Further, from the viewpoint of preventing the metal layer from being broken and improving the connection reliability in the bent state, the metal layer is not subjected to the roughening treatment or the roughening treatment is minimized. More preferably, it is 7 μm or less.

  In addition, since the polyimide metal laminate and the printed wiring board are bent inward or outward at the time of bending, the non-contact surfaces 12b and 15b that do not contact the adhesive polyimide layer of the metal layer (FIG. 1 ( A bending stress is generated in the same manner as in a) and (b). Therefore, the roughness of the non-contact surface that does not contact the adhesive polyimide layer of the metal layer is preferably as small as the surface that contacts the adhesive polyimide layer. The ten-point average roughness is preferably 2.0 μm or less for the purpose of preventing disconnection due to roughness.

  Moreover, in the polyimide metal laminated body 1 which concerns on this Embodiment, in order to laminate | stack a metal layer and an adhesive polyimide layer, the roughness of a metal layer is contact surface 14a, 16a (in contact with the metal layer of an adhesive polyimide layer). 1 (a) and 1 (b)). Therefore, by removing the metal layer from the polyimide metal laminate and measuring the roughness of the contact surface side in contact with the metal layer of the adhesive polyimide layer, the roughness of the metal layer on the surface in contact with the adhesive polyimide layer It can be.

(Polyimide metal laminate)
The polyimide metal laminate according to the present embodiment has a metal layer on one or both sides of the polyimide layer, and the polyimide layer includes a non-thermoplastic polyimide film and an adhesive polyimide layer. And it is a polyimide metal laminated body with which the non-thermoplastic polyimide film and the metal layer were couple | bonded through the adhesive polyimide layer. The polyimide metal laminate according to the present embodiment has a seam fold resistance test value of one or more times.

  As mentioned above, since the test value for the resistance to folding is good, when mounting electronic components on both sides of the flexible printed wiring board, avoid the occurrence of abnormalities in the circuit due to the load applied to the folding section be able to. Further, as described above, since it has a resistance to folding, a flexible wiring board can be incorporated in a small electronic device.

  “Peel fold resistance” means that the polyimide metal laminate is bent 180 ° and a load is applied to the bent portion, then the polyimide metal laminate is opened and the bent portion is bent 180 ° in the opposite direction and the load is applied to the bent portion. Call. This operation was regarded as a one-time folding resistance test, and the number of times was counted as a folding resistance test value.

  As a manufacturing method of the polyimide metal laminate according to the present embodiment, for example, a polyamic acid solution or a soluble polyimide solution that becomes an adhesive polyimide layer that can be thermocompression bonded after heat treatment is applied on a non-thermoplastic polyimide film and heated. There is a method of bonding a metal foil (hereinafter also referred to as “metal layer”) to a multilayer polyimide film obtained by performing the treatment.

  In the above method, the application to the non-thermoplastic polyimide film of the polyamic acid solution or soluble polyimide solution that becomes an adhesive polyimide layer capable of thermocompression bonding after the heat treatment is not particularly limited, but is a die coating method, a knife coating method, a gravure coating. It can be carried out by a conventional method such as a method, a comma coater, a three reverse coater, a slot die coater, a lip coater or a closed edge die. Since a coating solvent that easily absorbs moisture is used for the polyamic acid solution and the soluble polyimide solution, the liquid can be used in a closed system to suppress moisture absorption, and from the viewpoint that there is little change in liquidity during coating, a slot die coater or Particularly preferred are lip coaters and closed edge die coaters. Thereafter, a heat treatment is performed to obtain a multilayer polyimide film.

  As a multilayer polyimide film, a polyamic acid solution or a soluble polyimide solution that becomes an adhesive polyimide layer that can be thermocompression bonded after heat treatment is applied to both surfaces of the non-thermoplastic polyimide film, and a double-sided adhesive multilayer polyimide film is obtained by heat treatment. . In order to obtain such a double-sided adhesive multi-layer polyimide film, after applying a polyamic acid solution or a soluble polyimide solution to be an adhesive polyimide layer that can be thermocompression bonded after heat treatment to each of both sides by the method described above, May be dried together, or may be dried to the extent that the surface becomes tack-free after application on one side, and then the opposite side may be applied, and then both sides may be combined and dried, or application and drying may be performed. You may carry out sequentially one side at a time. Moreover, the composition of the adhesive polyimide resin layer formed on both surfaces may be the same or different. Moreover, each film thickness may be the same or different. The thickness of the adhesive polyimide resin layer is preferably 1 μm to 3 μm.

  As a heat treatment method, when applying to one side of a non-thermoplastic polyimide film, a normal roll transport dryer can be used. Moreover, when apply | coating to both surfaces of a non-thermoplastic polyimide film, a floating dryer is suitable.

  The heat treatment is performed until the amount of the solvent remaining in the coating film is reduced to a predetermined amount. The amount of residual solvent in the adhesive polyimide layer capable of thermocompression bonding remains from the viewpoint of preventing foaming when laminated with a metal foil or when a printed wiring board made of a polyimide metal laminate is subjected to a solder heat resistance test. The amount of the solvent is preferably 1% by mass or less with respect to the mass of the film after the heat treatment.

  The polyimide metal laminate using the above-mentioned multilayer polyimide film is obtained by laminating a multilayer polyimide film and a metal layer by a known method involving heating and / or pressurization, with a metal layer being stacked on one side or both sides of the multilayer polyimide film. You can get it. As the laminating method, a known method such as batch processing by a single plate press, hot roll lamination or continuous processing by a double belt press can be used. When obtaining a long length, it is preferable to use a double belt press in terms of being able to apply a uniform pressure. In particular, a double belt press that pressurizes the belt using a heating medium such as heated oil or heated gas is more uniform. It is preferable in that it is possible to apply an appropriate pressure.

  The polyimide metal laminate according to the present embodiment can be used for manufacturing a flexible printed wiring board. The heating method in the laminating method when manufacturing these printed wiring boards is not particularly limited. For example, a conventionally known method that can be heated at a predetermined temperature, such as a heat circulation method, a hot air heating method, an induction heating method, or the like. The employed heating means can be used. Similarly, the pressurization method in the laminating method is not particularly limited, and for example, a pressurization employing a conventionally known method that can apply a predetermined pressure, such as a hydraulic method, a pneumatic method, a gap pressure method, or the like. Means can be used.

(Printed wiring board)
The printed wiring board according to the present invention can be obtained by forming a circuit from the polyimide metal laminate by a subtractive method or the like. In the subtractive method, a photoresist layer is usually formed on a metal layer, this photoresist layer is selectively exposed and developed to form a wiring pattern, and the metal layer is etched using the patterned photoresist layer as an etching mask. The method is followed by processing, followed by complete removal of the photoresist layer. Here, a liquid or dry film resist is used as the photoresist, and an iron chloride-based, copper chloride-based or peracid-based solution is used as the etching solution.

  The printed wiring board according to the present invention preferably includes a printed wiring board formed from the polyimide metal laminate and a cover lay provided on the circuit of the printed wiring board. Thus, by providing the coverlay, the circuit can be protected.

(Coverlay)
As the coverlay according to the present invention, a polyimide film laminated with an adhesive can be used. What is necessary is just to protect the circuit surface of a printed wiring board through an adhesive bond layer. As the adhesive, acrylic, epoxy, polyimide, or the like can be used. Further, a method of applying the coverlay ink to the circuit surface of the printed wiring board and drying it may be used.

  The cover lay according to the present invention preferably has an elastic modulus of 4 GPa or less from the viewpoint of easy folding. When the elastic modulus is 4 GPa or less, the coverlay is easily bent, and the connection reliability in the bent state is improved. The elastic modulus is preferably 3.5 GPa or less. Moreover, 1 GPa or more is preferable from the point of circuit protection.

  The printed wiring board with coverlay according to the present invention preferably has a fold resistance test value of 4 times or more from the viewpoint of the degree of freedom of the method of incorporation into an electronic device. In general, when a coverlay is laminated as a protective film, the cover fold resistance test value deteriorates because the coverlay itself is easy to break due to rigidity. However, when the elastic modulus of the coverlay is 4 GPa or less as described above, the test value of the resistance to folding on the printed wiring board with the coverlay is also good, and the connection reliability when bent is improved. be able to.

(10-point average roughness Rz)
The ten-point average roughness Rz referred to in the present invention means that measured by the method described in JIS B0601: 1982.

(Example)
Next, although it demonstrates concretely based on the Example performed in order to clarify the effect of this invention, this invention is not limited at all by these Examples. In the following examples, ten-point average roughness Rz, elastic modulus, thickness, shell fold resistance test, and heat resistance measurement were performed as follows.

[10-point average roughness Rz measurement]
Ten-point average roughness Rz described in JIS B0601: 1982 was measured with a surf coder (SE-30D manufactured by Kosaka Laboratory Ltd.).

[Elastic modulus measurement]
The elastic modulus was measured as follows. A test specimen was cut to a width of 10 mm and a length of 320 mm, and conditioned at 23 ± 2 ° C. and humidity of 50 ± 5 RH% for 24 hours or longer in an environment, then Tensilon (manufactured by A & D). A sample set was sandwiched between test pieces at an Air pressure of 3 MPa or more. The distance between chucks was adjusted to 250 mm. Thereafter, measurement was performed at a tensile speed of 25 mm / min from the state where 0.3 N was applied, and the personal computer connected to the measuring machine sampled at a sampling interval of 20 μm. The number of measurements was five and the elastic modulus was determined. The elastic modulus was calculated by calculating the slope between the tensile elongation of 0.4% and 1.0%, and the average value was obtained.

[Thickness measurement]
The thickness of the adhesive polyimide resin layer was determined by subtracting the thickness of the non-thermoplastic polyimide film after measuring the thickness of the multilayer polyimide film. The measurement was performed with a contact-type film thickness meter (manufactured by Mitutoyo Corporation: Lightmatic VL-50AS, measuring force 0.26 N). The thickness was measured at intervals of 5 cm in the width direction, and an average value was obtained.

[Shell fold resistance test]
(Plastic fold resistance test of polyimide metal laminate)
A circuit having a line of 100 μm and a space of 100 μm was formed on one side of the polyimide metal laminate, and the metal layer on the opposite side was removed by etching, and the copper foil on the side opposite to the circuit side was left behind. A fold resistance test piece was formed. The circuit pattern of the test piece was such that six circuits having a width of 100 μm and a length of 110 mm were parallel to each other with a line of 100 μm and a space of 100 μm with reference to a sample for folding resistance test determined in JIS C 6471. In addition, the circuit at both ends was stretched to provide electrodes with a diameter of 3 mm for circuit resistance measurement, and if there was an abnormality in the circuit even at one location, the pattern was such that a change could be captured by a single resistance measurement. The test specimens were cut into a width of 10 mm and a length of 13 cm and were folded at the center in the longitudinal direction of the test piece. First, it was folded with the circuit surface inside, and a 1 kg weight was placed for 5 seconds. Then, the circuit surface was turned outside and the folded portion was folded so that the folded portion overlapped, and a 1 kg weight was placed for 5 seconds. The above operation was a one-time fold resistance test, and the resistance value of the circuit after the test was measured. The measurement of the resistance value was performed in a state where the test sample was bent at the helical fold. When there was a change in the circuit resistance value, it was regarded as a circuit breakage, and it was assumed that it had resistance to folding up to the previous number of times. The test piece from which the metal layer opposite to the circuit surface was removed by etching and the test piece from which all the metal layer opposite to the circuit surface was left had the smaller number of times of folding resistance. In addition, the load during the shell fold resistance test was set to 1 kgf with reference to the 180 ° bendability evaluation of the tin-plated COF tape in the reference literature (problems and countermeasures of materials and construction methods in densification of COF mounting). .

(Plastic fold resistance test of printed wiring board with coverlay)
Also, in the same manner as described above, a test piece in which a circuit having a line of 100 μm and a space of 100 μm is formed on one side of a polyimide metal laminate, and the metal layer on the opposite side of the circuit formation side is removed by etching, is opposite to the circuit formation side. The test piece which left all the copper foil of the side was formed. Furthermore, a coverlay was laminated on both sides of the test piece under the conditions of 160 ° C., 40 minutes, 4 MPa under vacuum, and a fold-resistant test piece with a coverlay was prepared. With a cover lay, the test piece for resistance to folding was cut to a width of 10 mm and a length of 13 cm, and then folded at the center in the longitudinal direction of the test piece. First, it was folded with the circuit surface inside, and a 1 kg weight was placed for 5 seconds. Then, the circuit surface was turned outside and the folded portion was folded so that the folded portion overlapped, and a 1 kg weight was placed for 5 seconds. The above operation was a one-time fold resistance test, the appearance of the coverlay after the test was observed, and the resistance value of the circuit was measured. The measurement of the resistance value was performed in a state where the test sample was bent at the helical fold. A four-fold resistance test was conducted. A case where there was no coverlay appearance abnormality and no change in circuit resistance value was marked with ◯, and a case where there was a coverlay appearance abnormality and circuit resistance value change was marked as x.

[Heat-resistant]
A circuit having a line of 100 μm and a space of 100 μm was formed on one surface of the polyimide metal laminate, and an electrode having a diameter of 3 mm was formed at the tip of the 100 μm circuit. A heat-resistant test piece was prepared in which all the copper foil on the side opposite to the circuit surface was left. A soldering iron heated to 350 ° C. was pressed against an electrode having a diameter of 3 mm for 10 seconds, and the appearance was observed. The test was performed with 10 electrodes. If no abnormality was found in all the electrodes, a circle was marked.

[Synthesis of thermocompressible polyamic acid varnish]
A stainless steel vessel was equipped with a stirrer and a nitrogen gas inlet tube, and reacted in a nitrogen gas stream.
1,3-bis (3-aminophenoxy) benzene and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride in N-methyl-2-pyrrolidone at a molar ratio of 1: 0.998 In addition, the solid content concentration with respect to N-methyl-2-pyrrolidone was set to 14% by mass and stirred. N-methyl-2-pyrrolidone and mesitylene were added at a mass ratio of 10: 6 to obtain a polyamic acid varnish capable of thermocompression bonding with a solid content concentration of 10% by mass.

[Example 1]
Using a closed edge die coater (manufactured by Inoue Metal Industry Co., Ltd.) having a backup roll, a thermocompression-bondable polyamic acid varnish synthesized under the above conditions on both surfaces of a non-thermoplastic polyimide film (manufactured by Kaneka Corporation, Apical 10 NPI) Each surface was coated at a line speed of 14 m / min so that the thickness of the coating film after the preliminary drying was 3.5 μm per side, and preliminarily dried at 150 ° C. Furthermore, in order to volatilize the solvent, it was dried at a temperature of 295 ° C. and a line speed of 3 m / min using a roll-to-roll type far infrared heating furnace. When the thickness of the obtained multilayer polyimide film was measured and the amount of the non-thermoplastic polyimide film was subtracted, the thickness of the adhesive polyimide layer capable of thermocompression bonding was 2.5 μm on one side. Then, using a double belt press (pressurization medium: heated oil), the maximum temperature was set to 330 ° C., and copper foil (Mitsui Metal Mining Co., Ltd.) was applied to both sides of the multilayer polyimide film at a pressure of 5 MPa and a speed of 3 m / min. Manufactured: NA-DFF (12 μm thick), Rz on the side in contact with the adhesive polyimide layer is 0.6 μm), and polyimide copper foil laminate A was obtained.

  A circuit was formed on the polyimide copper foil laminate A based on the above method, and a printed wiring board B with a coverlay was formed using a coverlay (Niskan Kogyo Co., Ltd., CISV1215).

  Table 1 below shows the non-thermoplastic polyimide film and coverlay elastic modulus measurement results, heat resistance test results, and shell fold resistance test results used in the test results based on the above test methods.

  In the shell fold resistance test of the polyimide copper foil laminate A, the test piece from which the metal layer on the side opposite to the circuit surface was removed by etching was subject to circuit breakage after eight shell fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after two helix fold resistance tests. A single fold resistance test value was shown regardless of the presence or absence of copper foil on the side opposite to the circuit surface.

  The printed wiring board with coverlay using the printed wiring board B with coverlay is a test specimen in which the metal layer on the side opposite to the circuit surface is removed by etching and all the metal layer on the side opposite to the circuit surface is left in the fold resistance test. Both test pieces showed good helix fold resistance after four helix fold resistance tests, with no coverlay appearance abnormality and no change in circuit resistance, regardless of the presence or absence of copper foil on the opposite side of the circuit surface. It was.

[Example 2]
A polyimide copper foil under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 3.0 μm on one side and the thickness of the copper foil was changed to 9 μm (Rz on the side in contact with the adhesive polyimide layer was 0.6 μm). A laminate C and a printed wiring board D with a coverlay were obtained.

  Table 1 below shows the non-thermoplastic polyimide film and coverlay elastic modulus measurement results, heat resistance test results, and shell fold resistance test results used in the test results based on the above test methods.

  In the shell fold resistance test of the polyimide copper foil laminate C, the test piece from which the metal layer opposite to the circuit surface was removed by etching was subject to circuit disconnection after the three shell fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after two helix fold resistance tests. A single fold resistance test value was shown regardless of the presence or absence of copper foil on the side opposite to the circuit surface.

  A printed wiring board with a coverlay using a printed wiring board D with a coverlay is a test specimen in which the metal layer on the side opposite to the circuit surface is removed by etching and all the metal layer on the side opposite to the circuit surface remains in the fold resistance test. Both test pieces showed good helix fold resistance after four helix fold resistance tests, with no coverlay appearance abnormality and no change in circuit resistance, regardless of the presence or absence of copper foil on the opposite side of the circuit surface. It was.

[Example 3]
A polyimide copper foil under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 1.0 μm on one side and the thickness of the copper foil was changed to 9 μm (Rz on the side in contact with the adhesive polyimide layer was 0.6 μm). A laminate E and a printed wiring board F with a coverlay were obtained.

  Table 1 below shows the non-thermoplastic polyimide film and coverlay elastic modulus measurement results, heat resistance test results, and shell fold resistance test results used in the test results based on the above test methods.

  In the shell fold resistance test of the polyimide copper foil laminate E, the test piece from which the metal layer opposite to the circuit surface was removed by etching showed circuit breakage after the five fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after two helix fold resistance tests. A single fold resistance test value was shown regardless of the presence or absence of copper foil on the side opposite to the circuit surface.

  A printed wiring board with a coverlay using a printed wiring board F with a coverlay is a test specimen in which the metal layer on the side opposite to the circuit surface is removed by etching and all the metal layer on the side opposite to the circuit surface is left in the fold resistance test. Both test pieces showed good helix fold resistance after four helix fold resistance tests, with no coverlay appearance abnormality and no change in circuit resistance, regardless of the presence or absence of copper foil on the opposite side of the circuit surface. It was.

[Example 4]
A polyimide copper foil under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 1.5 μm on one side and the thickness of the copper foil was changed to 9 μm (Rz on the side in contact with the adhesive polyimide layer was 0.6 μm). A laminate G and a printed wiring board H with a coverlay were obtained.

  Table 1 below shows the non-thermoplastic polyimide film and coverlay elastic modulus measurement results, heat resistance test results, and shell fold resistance test results used in the test results based on the above test methods.

  In the shell fold resistance test of the polyimide copper foil laminate G, the test piece from which the metal layer opposite to the circuit surface was removed by etching was subject to circuit disconnection after the five shell fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after two helix fold resistance tests. A single fold resistance test value was shown regardless of the presence or absence of copper foil on the side opposite to the circuit surface.

  The printed wiring board with coverlay using the printed wiring board H with coverlay is a test specimen in which the metal layer on the side opposite to the circuit surface is removed by etching and all the metal layer on the side opposite to the circuit surface is left in the fold resistance test. Both test pieces showed good helix fold resistance after four helix fold resistance tests, with no coverlay appearance abnormality and no change in circuit resistance, regardless of the presence or absence of copper foil on the opposite side of the circuit surface. It was.

[Example 5]
A polyimide copper foil under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 2.5 μm on one side and the thickness of the copper foil was changed to 9 μm (Rz on the side in contact with the adhesive polyimide layer was 0.6 μm). Laminated body I and printed wiring board J with coverlay were obtained.

  Table 1 shows the non-thermoplastic polyimide film using the test results based on the above test method, the elastic modulus measurement results of the coverlay, the heat resistance test results, and the shell fold resistance test results.

  In the shell fold resistance test of the polyimide copper foil laminate I, the test piece from which the metal layer opposite to the circuit surface was removed by etching was subject to circuit breakage after the three shell fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after two helix fold resistance tests. A single fold resistance test value was shown regardless of the presence or absence of copper foil on the side opposite to the circuit surface.

  The printed wiring board with coverlay using the printed wiring board J with coverlay is a test piece in which the metal layer on the side opposite to the circuit surface is removed by etching and the metal layer on the side opposite to the circuit surface remains in the fold resistance test. Both test pieces showed good helix fold resistance after four helix fold resistance tests, with no coverlay appearance abnormality and no change in circuit resistance, regardless of the presence or absence of copper foil on the opposite side of the circuit surface. It was.

[Comparative Example 1]
A polyimide copper foil laminate K and a printed wiring board L with a coverlay were obtained under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 3.1 μm on one side.

  Table 1 below shows the non-thermoplastic polyimide film and coverlay elastic modulus measurement results, heat resistance test results, and shell fold resistance test results used in the test results based on the above test methods. In the heat resistance test, 1 electrode out of 10 electrodes was displaced, resulting in poor heat resistance.

[Comparative Example 2]
A polyimide copper foil laminate M and a printed wiring board N with a coverlay were obtained under the same conditions as in Example 1 except that the thickness of the adhesive polyimide layer was changed to 0.9 μm on one side. When the copper foil of the polyimide copper foil laminate M was etched, voids were seen in the adhesive polyimide layer, and a good printed wiring board could not be obtained. Table 1 below shows the non-thermoplastic polyimide film, the elastic modulus measurement results of the coverlay, and the heat resistance test results used for the test results based on the above test method.

[Comparative Example 3]
Polyimide copper foil laminate O and cover under the same conditions as in Example 1 except that the copper foil was changed to (made by Nippon Electrolytic Co., Ltd .: USLPSE (12 μm thick), Rz on the side in contact with the adhesive polyimide layer was 1.6 μm) A printed wiring board P with a lay was obtained.

  Table 1 below shows the non-thermoplastic polyimide film using the test results based on the above test method, the elastic modulus measurement results of the coverlay, the heat resistance test results, and the shell fold resistance test results.

  In the shell fold resistance test of the polyimide copper foil laminate O, the test piece from which the metal layer opposite to the circuit surface was removed by etching was subject to circuit breakage after three shell fold resistance tests. The test piece in which all the metal layer on the side opposite to the circuit surface was left had circuit breakage after a single shell fold resistance test.

  A printed wiring board with a coverlay using a printed wiring board P with a coverlay was subjected to a test after four rounds of folding resistance tests on a test piece in which all the metal layer on the side opposite to the circuit surface was left. Disconnection occurred.

  As shown in Table 1, the polyimide metal laminate according to the present embodiment showed good heat resistance and shell fold resistance (Examples 1 to 5). On the other hand, when the thickness of the adhesive polyimide layer was large, the heat resistance decreased (Comparative Example 1). This is presumably because circuit subsidence or the like occurred due to softening of the adhesive polyimide layer at a temperature higher than the glass transition temperature. Moreover, when the thickness of the adhesive polyimide layer was small, voids were generated in the polyimide metal laminate, so that a good polyimide metal laminate was not obtained (Comparative Example 2). Furthermore, when the surface roughness of the metal layer was large, the number of times of folding resistance of the polyimide metal laminate and the results of the resistance testing of the printed wiring board with coverlay deteriorated (Comparative Example 3). This is presumably because the stress concentration acts on the roughened portion of the metal layer and the metal layer breaks.

  Since the polyimide metal laminate and the printed wiring board of the present invention are excellent in heat resistance and folding resistance, they are suitable for wiring substrates such as high-density wiring, highly reliable flexible printed wiring boards and IC package substrates. Moreover, the flexible printed wiring board is suitable for small electronic equipment.

DESCRIPTION OF SYMBOLS 1 Polyimide metal laminated body 11 Polyimide layer 12, 15 Metal layer 12a, 14a, 15a, 16a Contact surface 12b, 15b Non-contact surface 13 Non-thermoplastic polyimide film 14, 16 Adhesive polyimide layer

Claims (6)

  A non-thermoplastic polyimide film, a non-thermoplastic polyimide film, an adhesive polyimide layer provided on at least one surface of the non-thermoplastic polyimide film, and a metal layer provided on the adhesive polyimide layer. The elastic modulus of the film is 4 GPa or less, the thickness of the adhesive polyimide layer is 1 μm to 3 μm, and the metal layer has a ten-point average roughness Rz of a contact surface in contact with the adhesive polyimide layer of 1.0 μm. A polyimide metal laminate characterized by the following.   The polyimide metal laminate according to claim 1, wherein the fracture resistance test value is one or more times.   A printed wiring board comprising a circuit formed on a metal layer of the polyimide metal laminate according to claim 1.   A printed wiring board with a cover lay comprising the printed wiring board according to claim 3 and a cover lay provided on a circuit forming surface of the printed wiring board.   The printed wiring board with coverlay according to claim 4, wherein the test value of the shell fold resistance is 4 times or more.   The printed wiring board with a cover lay according to claim 4 or 5, wherein an elastic modulus of the cover lay is 4 GPa or less.

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