JP2007268892A - Manufacturing method for flexible laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible laminate with a small tensile modulus of elasticity, which shortens a treatment time required for a heating step after a polyimide precursor resin solution is applied onto conductive metallic foil, in a manufacturing process for the flexible laminate, and which is excellent in bendability and dimensional stability. <P>SOLUTION: In this manufacturing method for the flexible laminate, the polyimide precursor resin solution is applied onto the conductive metallic foil, and subjected to heating treatment, so as to be dried and cured. Characteristically, the total of heating time at 90°C or higher in the heating treatment is in the range of 5-25 minutes; the ratio between heating time at 90-200°C and heating time at a temperature exceeding 200°C is set to be in the range of 9:1-7:3; and control is performed so that the tensile modulus of elasticity of a polyimide resin layer formed on the conductive metallic foil can be in the range of 3-6 GPa and so that a coefficient of thermal expansion thereof can be in the range of 16-28 ppm/°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a flexible laminate in which an insulating layer made of a polyimide resin is provided on a metal foil.

  A flexible laminate consists of a metal layer and an insulating layer and has flexibility, so it is used for wiring boards where flexibility and flexibility are required, contributing to the downsizing and weight reduction of electronic devices. ing. Among flexible laminates, those using a polyimide resin as an insulating layer are widely used for wiring boards of cellular phones, information terminals, and the like because of their excellent heat resistance and dimensional stability. As a method of manufacturing a flexible laminate, a method of manufacturing a polyimide foil by bonding a polyimide resin film to a metal foil with an adhesive such as an epoxy resin or a method of manufacturing by directly applying a polyimide resin or its precursor resin solution on a metal foil The method of doing is mentioned. In particular, what is obtained by the latter is a flexible laminate that takes advantage of the characteristics of a polyimide-based resin without causing deterioration in characteristics due to the adhesive. (For example, refer to Patent Document 1.)

  In recent years, portable electronic devices are becoming smaller and lighter, and a wiring board must be bent and mounted in a very narrow space in the device. Therefore, the flexible laminate is required to be more flexible and easy to bend. Examples of methods for improving the bendability of the flexible laminate include thinning the metal foil and the insulating layer, and reducing the tensile elastic modulus of the insulating layer. Among these, in order to lower the tensile modulus of the polyimide resin useful as an insulating layer, it is generally considered to introduce a bendable ether bond or methylene bond into the molecular main chain of polyimide. For example, by synthesizing a polyimide precursor resin using 4,4′-oxydianiline (ODA) as a raw material monomer and imidizing it, an insulating layer of a polyimide resin having a low tensile elastic modulus can be obtained. (For example, see Patent Documents 2, 3, and 4.)

However, it is difficult to obtain sufficient adhesive strength between the polyimide and the metal layer when the polyimide resin single-layer film described in these patent documents is applied or laminated on a metal foil to form a flexible laminate. is there. As a method for solving the above problem, a polyimide resin layer is multilayered, and a thermoplastic polyimide resin layer having good adhesion to the metal foil is provided on the side in contact with the metal foil. A method of forming a polyimide resin layer having a low elastic modulus on the outer side (the side opposite to the metal foil) can be mentioned.
Japanese Patent No. 3034838 JP 2003-109989 A JP 2003-192788 A Japanese Patent No. 3523952

  However, when the insulating layer is multilayered using the thermoplastic polyimide resin as described above, generally, the thermal expansion coefficient of the entire insulating layer is increased, and the dimensional stability of the flexible laminate is deteriorated. In order to maintain sufficient dimensional stability that can withstand use as a flexible laminate, the heat treatment time after application of the resin solution must be lengthened, resulting in reduced productivity.

  This invention is made | formed as a result of examining in order to solve the problem which concerns, and becomes a heating process after apply | coating a polyimide precursor resin solution on electroconductive metal foil in the manufacturing process of a flexible laminated board. An object is to provide a flexible laminate having a short treatment time, a low tensile elastic modulus, excellent bendability, and excellent dimensional stability.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors set the heat treatment step after applying the polyimide precursor resin solution as a specific condition in the method for producing a flexible laminate by a coating method. Thus, the inventors have found that the characteristics of the insulating layer can be controlled, and have completed the present invention. That is, the present invention applies a polyimide precursor resin solution onto a conductive metal foil and heat-treats the polyimide precursor resin solution to dry and cure the polyimide laminate resin solution. The ratio of the heating time at 90 ° C. or more and 200 ° C. or less and the heating time at a temperature exceeding 200 ° C. is 9: 1 to 7: 3, and the conductivity is 5 to 25 minutes. It is a method for producing a flexible laminate, wherein the polyimide resin layer formed on the metal foil has a tensile elastic modulus of 3 to 6 GPa and a thermal expansion coefficient of 16 to 28 ppm / ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible laminated board which is excellent in a bendability and dimensional stability can be manufactured in short heat processing time, and there exists an effect which improves the productivity of the flexible laminated board which has such an outstanding characteristic.

Hereinafter, the present invention will be described in detail.
The flexible laminated board manufactured by this invention has a polyimide resin layer on electroconductive metal foil (henceforth only metal foil). And the formation of the polyimide resin layer on the metal foil is performed by applying the polyimide precursor resin solution on the metal foil and performing the drying and curing heat treatment to convert the polyimide precursor to polyimide. Is called. And the polyimide resin layer of the manufactured flexible laminated board has the tensile elasticity modulus in the range of 3-6 GPa, and a thermal expansion coefficient in 16-28 ppm / degreeC. In addition, the polyimide resin as used in the field of this invention means resin which consists of a polymer which has an imide group in molecular structures, such as a polyimide, polyamideimide, polyetherimide, polysiloxaneimide.

  Examples of the conductive metal foil used in the present invention include metal foils containing copper, aluminum, stainless steel, iron, silver, palladium, nickel, cobalt, chromium, molybdenum, tungsten, or alloys thereof as constituent elements. . Among metal foils, copper foil or alloy copper foil is preferable. The thickness of the metal foil is preferably in the range of 5 to 35 μm, more preferably in the range of 9 to 18 μm. When the metal foil is thicker than 35 μm, the laminated plate becomes hard and the flexibility and bendability deteriorate. When the metal foil is thinner than 5 μm, it is difficult to adjust the tension and the like in the manufacturing process of the laminate, and defects such as wrinkles are likely to occur. In addition, these metal foils may be subjected to chemical or mechanical surface treatment on the surface for the purpose of improving adhesive strength or the like.

  The polyimide precursor resin solution used in the present invention can be produced by a known method. For example, it can be obtained by dissolving tetracarboxylic dianhydride and diamine compound in an approximately equimolar organic solvent, and stirring and reacting at 0 to 100 ° C. for 30 minutes to 24 hours. As for the organic solvent used for polymerization, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-N-pyrrolidone, dimethyl sulfoxide, dimethyl sulfate, phenol, halogenated phenol, cyclohexanone, dioxane, Tetrahydrofuran, diglyme, triglyme and the like can be mentioned. Two or more of these can be used in combination. The viscosity of the polyimide precursor resin solution is preferably in the range of 500 cP to 100,000 cP. If it is out of this range, defects such as uneven thickness and streaks are likely to occur in the film during coating by a coater or the like.

  About the tetracarboxylic dianhydride and diamine compound to be used, the 1 type (s) or 2 or more types can each be selected suitably according to the characteristic of the polyimide resin layer of the flexible laminated board of this invention. In the present invention, it is necessary that the tensile modulus of the polyimide resin layer is in the range of 3 to 6 GPa and the thermal expansion coefficient is in the range of 16 to 28 ppm / ° C. In order to improve the adhesiveness between the foil and the polyimide resin layer, the polyimide resin layer is preferably a plurality of layers.

式中、Ｒ₁は下記構造式（２）及び（３）で表される基から選択される少なくとも１種の基であり、Ｒ₂は下記（４）及び（５）で表される基から選択される少なくとも１種の基である。また、下記構造式（４）中、Ｘは−ＳＯ₂−、−ＣＯ−及び直結合のいずれかである。

In the case where a plurality of polyimide resin layers are used, the layer in contact with the metal foil is preferably a high thermal expansion coefficient polyimide resin layer having a thermal expansion coefficient of 30 ppm / ° C. or higher. The high thermal expansion coefficient polyimide resin layer preferably has a structural unit represented by the general formula (1).

In the formula, R ₁ is at least one group selected from the groups represented by the following structural formulas (2) and (3), and R ₂ is a group represented by the following (4) and (5). At least one group selected. In the following structural formula (4), X is any of —SO ₂ —, —CO—, and a direct bond.

式中、R₃は、−CH₃、−C₂H₅、−OCH₃、−OC₂H₅のいずれかの置換基である。好ましくは、R₃は−CH₃である。また、式中、ｘ、ｙは、それぞれの構成単位の構成比率を表し、ｘは０．４〜０．６の範囲、ｙは０．６〜０．４の範囲とすることが好ましく、ｘ＋ｙ＝１である。xとyの割合において、xが０．４より小さくなると、ポリイミド樹脂の熱膨張係数が大きくなり、フレキシブル積層板とした際の寸法安定性が低下したり、積層板のカールが生じやすくなる傾向にある。一方、xが０．６より大きくなると、ポリイミドの引張り弾性率が大きくなり、フレキシブル積層板とした際の折り曲げ性が低下する傾向にある。 When making a polyimide resin layer into multiple layers, it is preferable to provide the base polyimide resin layer whose tensile elasticity modulus is 4-8 GPa adjacent to the outer side (opposite side to metal foil) of the said high thermal expansion coefficient polyimide resin layer. As a base polyimide resin layer, what has a structural unit represented by General formula (6) is preferable.

In the formula, R ₃ is a substituent of any of —CH ₃ , —C ₂ H ₅ , —OCH ₃ , and —OC ₂ H ₅ . Preferably R ₃ is —CH ₃ . In the formula, x and y represent the constituent ratio of each constituent unit, x is preferably in the range of 0.4 to 0.6, and y is preferably in the range of 0.6 to 0.4, x + y = 1. When x is smaller than 0.4 in the ratio of x and y, the thermal expansion coefficient of the polyimide resin increases, and the dimensional stability of the flexible laminated board tends to decrease, or the laminated board tends to curl. It is in. On the other hand, when x is larger than 0.6, the tensile elastic modulus of the polyimide is increased, and the bending property of the flexible laminate tends to be lowered.

  As a layer structure of the flexible laminate in the case where a plurality of polyimide resin layers are used, a structure in which a high thermal expansion coefficient polyimide resin layer is provided on a metal foil and a base polyimide resin layer is sequentially laminated thereon is preferable. A more preferable layer configuration is metal foil / high thermal expansion coefficient polyimide resin layer / base polyimide resin layer / high thermal expansion coefficient polyimide resin layer. Thus, after producing the single-sided flexible laminated board which has metal foil on the one side of a polyimide resin layer, it is polyimide by thermocompression-bonding metal foil with respect to the resin surface side, Preferably it is a high thermal expansion coefficient polyimide resin layer. It can also be set as the double-sided flexible laminated board which has metal foil on both surfaces of a resin layer.

  In this invention, although the manufacturing method which apply | coats and heat-processes the polyimide precursor resin solution on metal foil is employ | adopted, the total heating time of 90 degreeC or more in the drying and hardening process in the manufacturing process is 5-25. It is necessary to make minutes. Here, if the total heating time is shorter than 5 minutes, defects such as foaming are likely to occur in the polyimide resin. Conversely, when the total heating time exceeds 25 minutes, the productivity of the flexible laminate is deteriorated. Moreover, it is necessary to set the ratio of the heating time at 90 ° C. or more and 200 ° C. or less and the heating time at a temperature exceeding 200 ° C. in the total heating time in the drying and curing steps to 9: 1 to 7: 3. . If the ratio of the heating time at a temperature of 90 ° C. or higher and lower than 200 ° C. is less than 70% of the total heating time, the thermal expansion coefficient of the polyimide layer increases and the dimensional stability of the flexible laminate decreases. The laminated board curls. On the other hand, if the ratio of the heating time at a temperature lower than 200 ° C. exceeds 90% of the total heating time, the rate of temperature increase becomes too high during the heat treatment at a temperature exceeding 200 ° C. It is easy for defects to occur. When the polyimide resin layer is composed of a plurality of layers, the time for drying the polyimide precursor resin solution applied for each layer is totaled, and the time for curing these is added to determine the heating time. . Moreover, about the heating temperature over 200 degreeC, since the deterioration of a polyimide resin layer starts, the upper limit is good to set it as 450 degreeC.

  The thickness of the polyimide resin layer in the flexible laminate is preferably in the range of 5 to 40 μm. More preferably, it is 8-35 micrometers. When the thickness of the polyimide resin layer is less than 5 μm, the strength as an insulating layer is weak, and film breakage or the like easily occurs during processing of the flexible laminate. On the other hand, if the thickness is greater than 40 μm, the film is difficult to bend and the bendability of the flexible laminate is lowered. The preferred ratio of the base polyimide resin layer and the high thermal expansion coefficient polyimide resin layer when the polyimide resin layer is a plurality of layers is based on the total thickness of each base polyimide resin layer / high thermal expansion coefficient polyimide resin layer, 40 is preferably 2-30.

  In the manufacturing method of the flexible laminated board of this invention, the tensile elasticity modulus of a polyimide resin layer needs to be 3-6 GPa, and it is necessary to make the thermal expansion coefficient into 16-28 ppm / degreeC simultaneously. A preferable range of the tensile elastic modulus of the polyimide resin layer is 3.5 to 5.5 GPa. When the tensile elastic modulus is lower than 3 GPa, handling becomes difficult during processing of the flexible laminate, and when it is higher than 6 GPa, the bendability of the flexible laminate is lowered. A preferable range of the thermal expansion coefficient of the polyimide resin layer is 17 to 27 pm / ° C. When the thermal expansion coefficient of the polyimide resin layer is out of this range, the difference from the thermal expansion coefficient of the copper foil becomes large, so that the dimensional change of the flexible laminated board becomes large, and further, the laminated board is curled. In order to control the tensile elastic modulus and thermal expansion coefficient of the polyimide resin layer within the above ranges, it is possible to efficiently select the unit suitable for the structural unit constituting the polyimide resin layer and adjust the heat treatment conditions. It is possible to manufacture flexible laminates.

Hereinafter, the present invention will be described in detail with reference to examples. The abbreviations used in the examples are as follows.
DMAc: N, N-dimethylacetamide m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl
ODA: 4,4'-diaminodiphenyl ether
BAPP: 2,2'-bis (4-aminophenoxyphenyl) propane
PMDA: pyromellitic anhydride
BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride

Evaluation of the tensile elastic modulus and thermal expansion coefficient of the polyimide resin layer in the examples is based on the following method.
Tensile elastic modulus: Measured using a Strograph R-1 manufactured by Toyo Seiki Co., Ltd. (Conforms to IPC-TM-650, 2.4.19.)
Coefficient of thermal expansion: Using a thermal analyzer TMA-100 manufactured by Seiko Instruments Inc., the temperature was raised to 255 ° C. and held at that temperature for 10 minutes, and then cooled at a rate of 5 ° C./minute and 240 ° C. to 100 ° C. The average thermal expansion coefficient (thermal expansion coefficient) up to ° C. was determined.

[Synthesis Example 1]
In DMAc in a separable flask, 6 equivalents of m-TB and 4 equivalents of ODA were dissolved by stirring at room temperature. Next, 9.86 equivalents of PMDA were added. Thereafter, stirring was continued for about 3 hours to carry out a polymerization reaction to obtain a polyimide precursor resin solution a. DMAc was used in such an amount that the charged concentration of m-TB, ODA and PMDA was 16% by weight. The prepared polyimide precursor resin solution a is coated on a copper foil (Nikko Materials Co., Ltd., copper foil BHY-22B-T, 18 μm thickness. In the following, when simply referred to as copper foil, this copper foil is referred to) with a thickness of 260 μm. The solution was uniformly applied and dried by heating at 125 ° C. for 3 minutes to remove the solvent. Then, the heat treatment was carried out at a temperature range of 130 ° C. to 200 ° C. for 8 minutes and 30 seconds, and a temperature range of 201 ° C. to 360 ° C. for 3 minutes and 30 seconds to advance the imidization reaction. A formed laminate was obtained. The copper foil layer of the laminate was removed by etching treatment to obtain a polyimide film. When the tensile modulus and thermal expansion coefficient of the obtained polyimide film were measured, they were 6.8 GPa and 12.6 ppm / ° C., respectively.

[Synthesis Example 2]
Except for using 5 equivalents of m-TB and 5 equivalents of ODA, a polymerization reaction was performed in the same manner as in Synthesis Example 1 to obtain a polyimide precursor resin solution b. Using the prepared polyimide precursor resin solution b, a polyimide film was obtained in the same manner as in Synthesis Example 1, and the tensile modulus and the thermal expansion coefficient were measured, and were 5.9 GPa and 17.1 ppm / ° C., respectively. .

[Synthesis Example 3]
Except for using 4 equivalents of m-TB and 6 equivalents of ODA, a polymerization reaction was performed in the same manner as in Synthesis Example 1 to obtain a polyimide precursor resin solution c. Using the prepared polyimide precursor resin solution c, a polyimide film was obtained by the same method as in Synthesis Example 1, and the tensile modulus and the thermal expansion coefficient were measured, and were 5.1 GPa and 23.1 ppm / ° C., respectively. .

[Synthesis Example 4]
A polyimide precursor resin solution d was obtained by carrying out a polymerization reaction in the same manner as in Synthesis Example 1 except that 10 equivalents of m-TB and 0 equivalents of ODA were used. Using the prepared polyimide precursor resin solution d, a polyimide film was obtained in the same manner as in Synthesis Example 1 and the tensile modulus and thermal expansion coefficient were measured. The results were 13.8 GPa and −5.1 ppm / ° C., respectively. It was.

[Synthesis Example 5]
A polyimide precursor resin solution e was obtained by carrying out a polymerization reaction in the same manner as in Synthesis Example 1, except that 0 equivalent of m-TB and 10 equivalents of ODA were used. Using the prepared polyimide precursor resin solution e, a polyimide film was obtained in the same manner as in Synthesis Example 1, and the tensile modulus and the thermal expansion coefficient were measured, and were 2.7 GPa and 43.4 ppm / ° C., respectively. .

[Synthesis Example 6]
In DMAc in a separable flask, 10 equivalents of BAPP were dissolved by stirring at room temperature. Next, 9.69 equivalents of PMDA and 0.51 equivalents of BPDA were added. Thereafter, stirring was continued for about 3 hours to carry out a polymerization reaction to obtain a polyimide precursor resin solution f. DMAc was used in such an amount that the charged concentration of BAPP, PMDA and BPDA was 12% by weight. Using the prepared polyimide precursor resin solution f, except that the coating thickness was 350 μm, a polyimide film having a thickness of about 28 μm was obtained in the same manner as in Synthesis Example 1, and the tensile modulus and thermal expansion coefficient were measured. It was 2.6 GPa and 50.7 ppm / ° C.

[Example 1]
On the copper foil, the polyimide precursor resin solution f prepared in Synthesis Example 6 was uniformly applied with a thickness of 50 μm, and dried by heating at 125 ° C. to remove the solvent. Next, the polyimide precursor resin solution a prepared in Synthesis Example 1 so as to be laminated thereon was uniformly applied with a thickness of 190 μm, and dried by heating at 125 ° C. Furthermore, the polyimide precursor resin solution f was uniformly applied thereon with a thickness of 50 μm, and dried by heating at 125 ° C. The total heating and drying time so far was 3 minutes. Then, the heat treatment was carried out at a temperature range of 130 ° C. to 200 ° C. for 8 minutes and 30 seconds, and a temperature range of 201 ° C. to 360 ° C. for 3 minutes and 30 seconds to advance the imidization reaction. A formed laminate was obtained. The copper foil layer of the laminate was removed by etching treatment to obtain a polyimide film. The tensile modulus and thermal expansion coefficient of the obtained polyimide film were measured, and the results are shown in Table 1.

[Example 2]
A polyimide film was obtained in the same manner as in Example 1 except that the solution b was used in place of the polyimide precursor resin solution a, and the tensile modulus and thermal expansion coefficient were measured. The results are shown in Table 1.

[Example 3]
A polyimide film was obtained in the same manner as in Example 1 except that the solution c was used in place of the polyimide precursor resin solution a, and the tensile modulus and thermal expansion coefficient were measured. The results are shown in Table 1.

[Comparative Example 1]
A polyimide film was obtained in the same manner as in Example 1 except that the solution d was used in place of the polyimide precursor resin solution a, and the tensile modulus and thermal expansion coefficient were measured. The results are shown in Table 1.

[Comparative Example 2]
A polyimide film was obtained in the same manner as in Example 1 except that the solution e was used instead of the polyimide precursor resin solution a, and the tensile modulus and thermal expansion coefficient were measured. The results are shown in Table 1.

[Comparative Example 3]
The application of the polyimide precursor resin solution and heat drying (125 ° C., 3 minutes) were performed in the same manner as in Example 1. Then, the heat treatment is performed for 6 minutes in the temperature range of 130 ° C. to 200 ° C. and for 6 minutes in the temperature range of 201 ° C. to 360 ° C. to advance the imidization reaction, and a laminate in which a polyimide layer having a thickness of about 28 μm is formed on the copper foil Got the body. The copper foil layer of the laminate was removed by etching treatment to obtain a polyimide film. The tensile modulus and thermal expansion coefficient of the obtained polyimide film were measured, and the results are shown in Table 1.

Claims (2)

  In the manufacturing method of the flexible laminated board which dries and hardens a polyimide precursor resin solution by apply | coating a polyimide precursor resin solution on electroconductive metal foil, and heat-processing, the total heating time of 90 degreeC or more in heat processing is 5 The ratio of the heating time at 90 ° C. or more and 200 ° C. or less and the heating time at a temperature exceeding 200 ° C. is 9: 1 to 7: 3, and is formed on the conductive metal foil. A method for producing a flexible laminate, comprising controlling a tensile elastic modulus of the polyimide resin layer in a range of 3 to 6 GPa and a thermal expansion coefficient in a range of 16 to 28 ppm / ° C.   The polyimide resin layer has a thickness in the range of 5 to 40 μm, and is composed of a plurality of layers. At least one layer has a high coefficient of thermal expansion of 30 ppm / ° C. or higher, and at least one layer has a tensile modulus of 4 to 8 GPa. The method for producing a flexible laminate according to claim 1, wherein the layer having a base polyimide resin layer and in contact with the conductive metal foil is a high thermal expansion coefficient polyimide resin layer.