JP2009172996A - Flexible copper clad laminated board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high flexible copper clad laminate having a resistance increasing rate of not higher than 10% at 300,000 times of bending, and its manufacturing method. <P>SOLUTION: The flexible copper clad laminate is comprised of a polyimide type resin layer made of a polyimide film and a polyimide adhesive layer formed on one side or both sides of the polyimide film and a copper foil laminated on one side or both sides of the polyimide resin layer through the polyimide resin adhesive layer. A manufacturing method of the flexible copper clad laminate is also disclosed. The copper foil has a tensile strength of 100 MPa-300 MPa after heat treatment by a heat treatment process when the flexible copper clad laminate is manufactured and the polyimide type resin layer has an elastic modulus at 20 °C of 3 GPa-8 GPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flexible copper clad laminate used for a flexible printed circuit board and a method for producing the same.

  Due to the miniaturization and thinning of electronic devices, flexible printed circuit boards used in bending operation parts in electronic devices are required to have high bending characteristics. That is, the flexible printed circuit board does not break even when the bending radius of the substrate is smaller, the resistance increase rate is low, and good bending characteristics are required. The flexible copper-clad laminate used for this is also the same The characteristics are necessary.

  A flexible copper clad laminate is usually composed of a copper foil and a polyimide resin layer, and is characterized by being thin and having flexibility and flexibility. This copper clad laminate is used for a flexible printed circuit board of a small and highly functional electronic device.

For flexible copper clad laminates,
1) A copper-clad laminate by applying a polyimide resin solution or a polyimide resin precursor resin solution, such as a polyamic acid solution, onto a copper foil, drying and curing to form a polyimide layer, so-called cast copper-clad Laminated board,
2) A copper-clad laminate that forms a copper layer by sputtering and plating copper alloy or copper directly on the polyimide film, that is, a copper-clad laminate by plating, and 3) bonding the polyimide film and copper foil together Copper-clad laminate by lamination method,
There is.

  The copper-clad laminate produced by the casting method 1) does not have a so-called stiffness in the polyimide layer, and if the polyimide layer has a thickness of 20 μm or more, the bending properties after circuit formation are inferior. In addition, in order to make the thickness of the cured polyimide layer 20 μm or more, it is necessary to apply several times. In this case, the polyimide layer tends to be discontinuous in both the thickness direction and the surface direction, and the bending characteristics are satisfactory. It wasn't going.

  The copper-clad laminate by the plating method 2) is expensive in equipment, strictly managed in processing conditions, and has a low production yield. Sputtering tends to cause pinholes, poor plating, and formation of a uniform plating layer is difficult, and the peel strength is thus reduced. Also, there are many cases where problems arise in the bending characteristics due to insufficient strength of the copper layer itself.

  On the other hand, it is known that the copper-clad laminate by the laminating method of 3) has excellent bending characteristics. As this copper-clad laminate, for example, a polyamic acid solution is applied and dried on a copper foil, a polyimide film is laminated to a semi-dried adhesive layer with a heating roll, and further heated, the adhesive layer A single-sided copper-clad laminate produced by a laminating method in which a solvent is dried and a polyamic acid is imidized is known. Also known is a double-sided copper-clad laminate by a laminating method in which a copper foil is laminated on both sides of a polyimide film having a thermocompression bonding polyimide layer. Since both copper clad laminates are copper clad laminates having a polyimide film, they are flexible copper clad laminates that sufficiently reflect the excellent properties (heat resistance, dimensional stability, bending properties) of polyimide films. .

  As described above, a flexible copper-clad laminate having a polyimide film by a laminating method has excellent bending properties. However, in recent years, electronic devices are becoming smaller and thinner, and a flexible printed circuit board used therefor needs to have a smaller bending radius and a low resistance increase rate without disconnection. With such a small bend radius, even in the case of flexible copper clad laminates made by the conventional laminating method, the ductile fatigue of the copper foil due to repeated bending increases the number of fractures and increases the resistance rise rate. May end up. Therefore, a higher bending property with higher electrical reliability is required.

  As a flexible copper-clad laminate with improved flexibility, a polyamic acid is applied and dried on an electrolytic copper foil to form a resin layer, heat-treated for several hours, and the resin layer is cured to form a polyimide layer. In addition, there is a flexible copper-clad laminate obtained by subjecting a copper foil to heat treatment (Patent Document 1). In this copper clad laminate, the tensile strength is lowered by heat treatment of the copper foil, and the flexibility and folding resistance are good. However, the manufacturing method of this patent document is a method in which a polyimide layer is directly formed on a copper foil, and is the above-described casting method. Even if the folding resistance of the copper foil is improved and the folding resistance of the flexible copper-clad laminate is improved, the bending portion has a wide range as in the case of an actual electronic component having a wide bending operation portion. In the IPC bending characteristic test, the rate of increase in resistance is 30% or more. In particular, when the bending radius of the flexible printed circuit board is smaller, there is a problem that it breaks. In this patent document, no mention is made of the elastic modulus of the polyimide layer. Therefore, when the elastic modulus of the polyimide layer is not in a specific range, there is a problem that the bending property is inferior.

  As described above, there has been no flexible copper-clad laminate having high bending characteristics even when the bending radius is small.

JP2004-237596

  The present invention has been made in view of the above circumstances, and provides a flexible copper-clad laminate having improved flexibility and a method for producing the same, making full use of the properties of a polyimide film having excellent bending properties. Objective. In particular, in a wide range of bending operation in the actual operating part of the electronic equipment, the resistance increase rate at 300,000 times of bending is 10% or less in the IPC bending test at normal temperature, bending radius of 0.65 mm, bending speed of 100 times / min. An object of the present invention is to provide a flexible copper-clad laminate having a high bending property and a method for manufacturing the same.

  As a result of intensive studies and studies to obtain a flexible copper-clad laminate having very excellent bending characteristics even when performing an IPC bending test at a bending radius R = 0.65 mm, the present inventors have found that flexible copper as a copper foil. Excellent bending properties when using a material that has a specific value for the tensile strength after heating in the heat treatment process during the manufacture of the tension laminate and a polyimide resin layer having a specific range of elastic modulus It has been found that a flexible copper-clad laminate having fully improved characteristics of the polyimide film it has and further improved in bending properties has been achieved.

  That is, the first invention of the present application is a polyimide resin layer composed of a polyimide film and a polyimide adhesive layer provided on one side or both sides of the polyimide film, and one side of the polyimide resin layer provided with the polyimide adhesive layer or A flexible copper-clad laminate in which copper foil is laminated on both sides via the polyimide adhesive layer, and the copper foil has a tensile strength after heating by a heat treatment step in the production of the flexible copper-clad laminate of 100 MPa to 300 MPa. The polyimide resin layer is a flexible copper-clad laminate having an elastic modulus at 20 ° C. of 3 GPa to 8 GPa.

  In the second invention of the present application, a polyimide precursor solution or a polyimide solution is applied and dried on a copper foil having a tensile strength before production of a flexible copper-clad laminate of 330 MPa to 530 MPa to form a semi-dry adhesive layer. And after laminating a polyimide film on the adhesive layer with a heating roll, further heating and applying a solution of the polyimide precursor, solvent drying and imidization of the adhesive layer, and applying a polyimide solution Is characterized by performing solvent drying, and the tensile strength of the copper foil after heating in the heat treatment step during the production of the flexible copper clad laminate is 100 MPa to 300 MPa, and the modulus of elasticity of the polyimide resin layer at 20 ° C. Is a method for producing a flexible single-sided copper-clad laminate with 3 GPa to 8 GPa.

  3rd invention of this application consists of a polyimide film provided with a thermocompression bonding polyimide adhesive layer on one side or both sides, and on the thermocompression bonding adhesive layer of a polyimide resin layer having an elastic modulus at 20 ° C. of 3 GPa to 8 GPa. The strength of the copper foil after heating by the heat treatment process during the production of the flexible copper clad laminate is characterized in that the copper foil having a tensile strength before production of the flexible copper clad laminate of 330 MPa to 530 MPa is thermocompression bonded. This is a method for producing a flexible single-sided or double-sided copper-clad laminate in which the elastic modulus at 20 ° C. of the polyimide-based resin layer is 3 GPa to 8 GPa.

  The flexible copper-clad laminate of the present invention has a resistance increase rate of 10% or less after 300,000 bendings in an IPC bending test at normal temperature, a bending radius R = 0.65 mm, and a bending speed of 100 times / min. High bending properties.

<Flexible copper-clad laminate>
The flexible copper-clad laminate of the present invention is a single-sided or double-sided copper-clad laminate in which a copper foil is laminated by a laminating method on one or both sides of a polyimide-based resin layer via an adhesive layer of the polyimide-based resin layer. is there.

<Copper foil>
The copper foil used in the flexible copper-clad laminate of the present invention has a tensile strength after heating due to a heat treatment process during the production of the flexible copper-clad laminate, that is, a tensile strength specified in JIS C 5016 is 100 MPa to 300 MPa. Is essential, and preferably 150 MPa to 250 MPa. When the tensile strength after heating is less than 100 MPa, the strength is small and the copper foil layer is easily broken. In addition, the obtained copper-clad laminate tends to warp, making circuit formation difficult. When the tensile strength after heating exceeds 300 MPa, the copper foil is too rigid and the resulting copper-clad laminate is not flexible and has poor bending performance.

  Copper foil that can be used as a copper foil with a post-heat tensile strength of 100 MPa to 300 MPa due to a heat treatment process during the production of a flexible copper clad laminate is copper with a tensile strength before production of the flexible copper clad laminate of 330 MPa to 530 MPa. A foil can be used, and a commercially available rolled copper foil or electrolytic copper foil can be used. For example, BHY-T foil (trade name) and BHY-HA foil (trade name) manufactured by Nikko Metal Co., Ltd. Super-HTE foil (trade name) and DFF foil (trade name) manufactured by Mitsui Metal Mining Co., Ltd., manufactured by Microhardware VSRD foil (trade name).

  The thickness of the copper foil layer is preferably 3 μm to 20 μm, particularly preferably 10 μm to 18 μm. If the copper foil is thick, it becomes rigid and inferior in bending properties. If it is too thin, the copper foil may be cut during lamination.

<Polyimide resin layer>
The polyimide resin layer is composed of a polyimide film and a polyimide adhesive layer provided on one side or both sides of the polyimide film. The polyimide resin layer has an elastic modulus at 20 ° C. of 3 GPa to 8 GPa, preferably 4 GPa to 6 GPa. If it is less than 3 GPa, it is too soft, and it tends to be poor in appearance such as wrinkles or creases during lamination, and the film may break. If it exceeds 8 GPa, it is rigid and inferior in bending performance.
The polyimide resin refers to a resin having an imide group, and examples thereof include polyimide, polyamideimide, and polyesterimide.

  The total thickness of the polyimide resin layer (polyimide film and adhesive layer) is preferably 10 μm to 30 μm. If it is less than 10μm, it tends to wrinkle during transportation and lamination, and it is easy to cut. When it exceeds 30 μm, the bending performance is inferior.

As the polyimide resin layer, a thermocompression bonding polyimide film having a thermocompression bonding adhesive layer formed on one side or both sides, preferably both sides, of a polyimide film can be used. The thermocompression bonding polyimide film is a polyimide film provided with a thermocompression bonding adhesive layer having a glass transition temperature of 300 ° C. or lower on one or both sides, preferably both surfaces of a polyimide film having a glass transition temperature of 350 ° C. or higher. The thermocompression bonding polyimide film having a thermocompression bonding polyimide adhesive layer formed on both sides of the polyimide film is not particularly limited. For example, Upilex VT (trade name) manufactured by Ube Industries, Pixio (trade name) manufactured by Kaneka Corporation and so on.
Alternatively, the polyimide-based resin layer is formed by applying a polyimide precursor, for example, a polyamic acid solution or a polyimide solution on a copper foil to form a polyimide adhesive layer on the copper foil as described below. A polyimide resin layer composed of a polyimide film and a polyimide adhesive layer may be formed by laminating the copper foil and the polyimide film so that the polyimide film overlaps the polyimide adhesive layer and heat-treating.

A commercially available polyimide film can be used as the usable polyimide film. Examples include Apical NPI (trade name) and Apical AH (trade name) manufactured by Kaneka Corporation, Kapton EN (trade name), Kapton H (trade name), and Kapton V (trade name) manufactured by Toray DuPont. It is done.
The thickness of the polyimide film is preferably 10 μm to 25 μm.
The polyimide film may be subjected to plasma treatment or etching treatment on the surface on which the adhesive layer is provided.

  The polyimide adhesive layer may be a thermocompression bonding polyimide adhesive layer included in the thermocompression bonding polyimide film, or may be a polyimide adhesive layer formed on a copper foil as described above. The thickness of the adhesive layer is preferably 10 μm or less, and in the case of a polyimide adhesive layer formed on a copper foil, it is preferably 1 to 10 μm. When the thickness is 10 μm or less, it is not affected by thermal deformation of the copper foil, and therefore, appearance abnormality (wrinkle, curl) does not occur, and thickness unevenness does not cause a problem because it is thin.

<Manufacturing method>
Although the manufacturing method of the flexible copper clad laminated board of this invention is not specifically limited, The polyimide adhesive layer is formed on copper foil, The manufacturing method of the single-sided copper clad laminated board bonded with a polyimide film, and the single side | surface or both sides of a polyimide film And a method for producing a single-sided or double-sided copper-clad laminate in which a polyimide film is bonded to a thermocompression-bondable polyimide film and a copper foil.

Specifically as a manufacturing method of a flexible copper clad laminate,
1) A polyimide adhesive layer is formed by applying, heating, and drying a polyamic acid solution or a polyimide resin solution, which is a polyimide precursor, on a copper foil, and the resulting copper foil and polyimide film are bonded to the adhesive layer. The polyimide adhesive layer is further dried after being laminated, and 2) a method for producing a single-sided copper-clad laminate, and 2) an adhesive layer of a thermoplastic polyimide layer is formed on one or both sides, preferably both sides of a polyimide film After that, one side or both sides, preferably one side or both sides of the double-sided copper-clad laminate, preferably a double-sided copper-clad laminate,
Is mentioned.

As a method of laminating copper foil, for example,
i) A roll press method in which a sheet-like copper foil and a polyimide film are superposed via an adhesive layer and thermocompression bonded by a heated roll press machine,
ii) A continuous roll laminating method in which copper foil and a polyimide film having an adhesive layer are continuously supplied to two upper and lower heating rolls and sandwiched between the rolls, and
iii) a double belt press method in which a copper foil and a polyimide film are heated and pressure-bonded through an adhesive layer by a pair of endless belts having a pressure mechanism inside;
Is mentioned.

As the method for producing a single-sided copper-clad laminate of 1) above, in particular, a solution containing polyamic acid, preferably 50% by mass or more, is applied onto a copper foil, heated and pressed after semi-drying, and a polyimide film. Is preferably used, followed by solvent drying and imidization of polyamic acid.
The apparatus for applying the polyamic acid solution and the method for semi-drying are not particularly limited, but the application may be performed using a comma coater, die coater, roll coater, knife coater, reverse coater, lip coater, etc. The imidation ratio may be less than 5%, preferably 40 ° C to 120 ° C. If it is less than 40 ° C, it will not be laminated, and if it exceeds 120 ° C, it will foam during lamination. In the heated roll press, the roll is heated with oil, steam, or the like, and a metal roll such as carbon steel, or a rubber roll made of heat-resistant NBR rubber, fluorine rubber, or silicon rubber is used. The roll press conditions are not particularly limited. Usually, the roll temperature is 100 to 150 ° C., which is not lower than the softening point of the polyamic acid after semi-drying and not higher than the boiling point of DMAc (dimethylacetoside) used as a solvent. The linear pressure is in the range of 5 to 100 kg / cm. The solvent is dried at a temperature below the boiling point of the solvent until the solvent runs out. That is, the temperature may be 30 ° C. to 200 ° C. and the drying time may be 3 to 30 hours. Imidation of the polyamic acid after removal of the solvent may be performed at an oxygen concentration that does not oxidize the copper foil at a temperature of 250 ° C. to 400 ° C. for 3 to 20 hours under reduced pressure or in a nitrogen atmosphere. The copper foil undergoes heat treatment by solvent drying and imidization.

  As the method for producing a single-sided or double-sided copper-clad laminate of 2) above, a method in which a copper foil is disposed on one side or both sides of a polyimide film provided with a thermocompression-bonding polyimide adhesive layer on both sides and heat-pressed is particularly preferable. . The method for heat pressing is not particularly limited, and may be sandwiched between press plates, between a pair of endless belts having a pressure mechanism inside, or between one or more metal rolls. The temperature at the time of hot pressing is a temperature that is 15 ° C. or more higher than the glass transition temperature of the thermocompression bonding polyimide layer, and preferably 400 ° C. or less. When the temperature is lower than the glass transition temperature by 15 ° C. or more, it does not adhere to the glass transition temperature. In the heating press, conductive heating such as a heater, radiation heating such as far infrared, induction heating, or the like is used. The pressure during pressing is usually a linear pressure of 50 N / cm to 150 N / cm. The hot pressing is performed at an oxygen concentration that does not oxidize the copper foil, and is usually performed under reduced pressure or in a nitrogen atmosphere.

  The copper foil is subjected to a heat treatment at the time of hot pressing, but after the hot pressing, it is also preferable to heat anneal for about 20 to 40 minutes in a temperature range of 100 ° C. to 400 ° C.

  The thus obtained flexible copper-clad laminate of the present invention has an increase rate of resistance of 10 times at 300,000 bends in an IPC bendability test at normal temperature, a bend radius of 0.65 mm, and a bend speed of 100 times / min. % Or less.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<Example 1>
On a rolled copper foil “BHY-HA foil” (trade name) made of Nikko Metal with a thickness of 12 μm, a polyamic acid solution was applied to a thickness of 15 μm with an applicator and dried in an oven at 120 ° C. for 2 minutes. . A 10μm thick Kaneka Co., Ltd. polyimide film “Apical NPI” (trade name) was layered on this and laminated at a test roll laminator manufactured by Nishimura Machinery at 120 ° C x 15kfg / cm x 4m / min. . This was heat-treated continuously in a vacuum oven with an internal pressure of 100 Pa at 160 ° C. for 8 hours, 250 ° C. for 3 hours, and 350 ° C. for 3 hours. As a result, a single-sided copper-clad laminate having a copper foil of 12 μm and a polyimide resin layer of 12 μm was obtained.

<Examples 2 to 5>
A single-sided copper-clad laminate was obtained in the same manner as in Example 1 except for the conditions shown in Table 1.

<Comparative Examples 1-2>
A single-sided copper clad laminate was obtained in the same manner as in Example 1 except for the conditions shown in Table 3.

<Example 6>
Rolled copper foil “BHY-HA foil” (product name) 12 μm thick made of Nikko Metal on both sides of polyimide film “Pixio BP” (product name) with Kaneka thermocompression bonding polyimide adhesive layer 14 μm thick ) And laminated at 300 ° C. × 20 kfg / cm × 5 m / min. Using a test roll laminator manufactured by Nishimura Machinery. This obtained the double-sided copper clad laminated board.

<Examples 7 to 10>
A double-sided copper clad laminate was obtained in the same manner as in Example 6 except for the conditions shown in Table 2.

<Comparative Example 3>
A double-sided copper clad laminate was obtained in the same manner as in Example 6 except for the conditions shown in Table 3.

Using the flexible copper-clad laminates of Examples 1 to 10 and Comparative Examples 1 to 3, the modulus of elasticity of the polyimide-based resin layer, the tensile strength after heat by the heat treatment process during the production of the copper foil, and the IPC bend The sex was measured. The results are shown in Tables 1-3.
<Measurement of elastic modulus of polyimide resin layer>
The measurement was performed according to ASTM D882 standard.

  A sample cut out to 100 mm × 10 mm was used as a test piece. Using a tensile tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., model name: Strograph V10D), the tensile modulus was measured in each of the MD and TD directions under the conditions of a tensile speed of 50 mm / min and a distance between chucks of 40 mm. Then, the elastic modulus of the polyimide resin layer was averaged.

<Tensile strength after heating by heat treatment process during copper foil production>
The copper foil in the produced copper clad laminate was taken out and the tensile strength was measured according to JIS C 5016.

<IPC flexural property test evaluation>
A circuit pattern defined in IPC FC 241 was produced on the copper foil layer of the copper clad laminate. A coverlay was pressed on the circuit surface. The press conditions are: press temperature: 160 ° C., press pressure: 4.9 MPa, press time: 30 minutes. Thus, an IPC flexibility test piece was obtained. Using this, with the copper foil facing outside, repeated bending at normal temperature, bending radius of 0.65 mm, bending speed of 100 times / minute, stroke of 30 mm, the number of times the circuit resistance value exceeded 10% or the circuit broke The number of times was defined as the number of bending times.

Claims (10)

  A polyimide resin layer composed of a polyimide film and a polyimide adhesive layer provided on one or both sides of the polyimide film, and one or both surfaces of the polyimide resin layer provided with the polyimide adhesive layer via the polyimide adhesive layer The copper foil is a flexible copper clad laminate, and the copper foil has a tensile strength after heating in a heat treatment step during the production of the flexible copper clad laminate of 100 MPa to 300 MPa, and the polyimide resin layer is A flexible copper-clad laminate having an elastic modulus at 20 ° C. of 3 GPa to 8 GPa.   The flexible copper-clad laminate according to claim 1, wherein, in an IPC bendability test at normal temperature, a bend radius of 0.65 mm, and a bend speed of 100 times / min., The rate of increase in resistance at a bend number of 300,000 is 10% or less.   The flexible copper clad laminate according to claim 1, wherein the copper foil is a rolled copper foil or an electrolytic copper foil having a thickness of 3 μm to 20 μm.   The flexible copper clad laminate according to claim 1, wherein the polyimide resin layer has a thickness of 10 μm to 30 μm.   When the polyimide-based resin layer is coated with a polyimide film and a polyimide precursor solution or a polyimide solution on the copper foil, and a polyimide precursor solution is applied, it is formed by heating imidization or a polyimide solution is applied. The flexible copper-clad laminate according to any one of claims 1 to 4, comprising a polyimide adhesive layer formed by heating and drying, wherein the copper-clad laminate is a single-sided copper-clad laminate.   The flexible copper-clad laminate according to claim 5, wherein the polyimide resin layer comprises a polyimide film and a polyimide adhesive layer formed by applying a polyamic acid solution containing 50% by mass or more of polyamic acid and heating imidization. Board.   The flexible copper clad laminated board of any one of Claims 1-4 which the said polyimide-type resin layer consists of a polyimide film provided with the thermocompression-bonding polyimide adhesion layer on the single side | surface or both surfaces.   A polyimide precursor solution or a polyimide solution is applied and dried on a copper foil having a tensile strength of 330 MPa to 530 MPa before production of a flexible copper-clad laminate to form a semi-dried adhesive layer, and a polyimide film is formed on the adhesive layer. After laminating with a heating roll, when further heated, when the polyimide precursor solution is applied, the adhesive layer is solvent-dried and imidized, and when the polyimide solution is applied, the solvent is dried. The manufacturing method of the flexible single-sided copper clad laminated board of Claim 5 or 6.   A flexible copper-clad laminate comprising a polyimide film having a thermocompression bonding adhesive layer on one or both sides, and a polyimide resin layer having an elastic modulus at 20 ° C. of 3 GPa to 8 GPa. The method for producing a flexible single-sided or double-sided copper-clad laminate according to any one of claims 1 to 4 and 7, wherein a copper foil having a tensile strength before the production of is from 330 MPa to 530 MPa.   10. The flexible double-sided structure according to claim 9, wherein a copper foil is thermocompression-bonded on each thermocompression-bonding polyimide adhesive layer of a polyimide resin layer comprising a polyimide film provided with a thermocompression-bonding polyimide adhesive layer on both sides. A method for producing a copper clad laminate.