TWI392427B - Manufacturing method of flexible laminated plate - Google Patents

Description

Method for manufacturing flexible laminate

The present invention relates to a method of producing a flexible laminate having an insulating layer made of a polyimide resin on a metal foil.

The flexible laminated board is composed of a metal layer and an insulating layer, and is flexible, so that it is used in a wiring board that requires flexibility and flexibility, and contributes to downsizing and weight reduction of an electronic device. Even in a flexible laminate, the insulating layer is made of a polyimide resin, and is widely used for wiring boards such as mobile phones and information terminals because of its excellent heat resistance and dimensional stability. The method for producing a flexible laminate is a method in which a polyimide film is bonded to a metal foil by a binder such as an epoxy resin, or a polyimide resin or a polyimide resin is directly coated on the metal foil. A method of producing a resin solution in advance. In particular, those obtained by the latter method do not have a property of lowering the characteristics due to the binder, and become a flexible laminate which utilizes the properties of a polyimide-based resin. (For example, refer to Patent Document 1)

In recent years, the miniaturization and weight reduction of portable electronic devices are increasing, and it is necessary to bend and mount the wiring substrate in a very narrow space inside the machine. Therefore, the flexible laminate will be required to be softer and easier to bend. A method of improving the bending property of a flexible laminate is, for example, a method of thinning a metal foil or an insulating layer or reducing a tensile modulus of an insulating layer. Among them, in order to reduce the tensile modulus of the polyimine resin which is effectively used as the insulating layer, it is generally considered to introduce a bendable ether bond or a methylene bond or the like in the molecular main chain of the polyimide. For example, a polyiminoimine precursor resin using 4,4'-oxydiphenylamine (ODA, oxydianiline) as a raw material monomer is synthesized, and by yttrium yttrium, the tensile modulus is low. Polyimine resin insulating layer (for example, refer to Patent Documents 2, 3, and 4).

However, in the case of the single-layer film of the polyimide film described in the above patent documents, when the metal foil is coated or laminated to form a flexible laminate, it is difficult to form between the polyimide and the metal layer. Get sufficient bond strength. The method for solving the above problem is to multilayer the polyimide layer of the polyimide, and to provide a thermoplastic polyimide-based resin layer having good adhesion to the metal foil on the side adjacent to the metal foil, and to form the thermoplastic polyimide layer. The outer side of the imide resin layer (the side opposite to the metal foil side) forms a polyimine-based resin layer having a low modulus of elasticity.

[Patent Document 1] Japanese Patent No. 3034838 (Patent Document 2) Japanese Laid-Open Patent Publication No. 2003-109788 (Patent Document 3) Japanese Patent Publication No. 2003-192788 (Patent Document 4) Japanese Patent No. 3523952

However, when the insulating layer is multilayered by 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 when used as a flexible laminate, it is necessary to lengthen the heat treatment time after the application of the resin solution, which causes a problem of reduced productivity.

The present invention has been intensively studied in order to solve the problem, and an object thereof is to provide a flexible laminate in which a polyimide polyimide precursor solution is applied to conductivity in a manufacturing step of a flexible laminate. The heating step after the metal foil is required to have a short processing time, a low tensile modulus, a good bending property, and a good dimensional stability.

In order to solve the above-mentioned problems, the inventors of the present invention have found out that in the method for producing a flexible laminated board by a coating method, a heat treatment step after applying a polyimide resin precursor resin solution By setting the specific conditions, it is possible to control the characteristics of the insulating layer, and the present invention has been completed. In other words, the method for producing a flexible laminate of the present invention is to apply a solution of a polyimide precursor resin onto a conductive metal foil, and to heat the polyimine precursor resin solution by heat treatment. Further, in the method of producing a cured flexible laminate, the heating time of 90 ° C or more is set to a range of 5 to 25 minutes, and the heating time of 90 ° C or more and 200 ° C or less is used in the heat treatment. And the ratio of the heating time at a temperature exceeding 200 ° C is set to 9:1 to 7:3, and the tensile modulus of the polyimide film formed on the conductive metal foil is controlled to 3 to 6 GPa. The coefficient of thermal expansion is controlled in the range of 16 to 28 ppm / ° C.

According to the present invention, it is possible to manufacture a flexible laminate having excellent bending property and dimensional stability with a short heat treatment time, and to have an effect of improving the productivity of a flexible laminate having such superior characteristics.

Hereinafter, the present invention will be described in detail.

The flexible laminate produced by the present invention has a polyimide resin layer on a conductive metal foil (hereinafter referred to as "metal foil"). Further, a method of forming a polyimide layer on a metal foil is carried out by coating a polyimide film on a metal foil, and then performing a heat treatment of drying and hardening. The above polyimine precursor is converted into a polyimine. Further, the polyimine resin layer of the manufactured flexible laminate has a tensile modulus of 3 to 6 GPa and a coefficient of thermal expansion of 16 to 28 ppm/°C. In addition, the term "polyimine resin" as used in the present invention means, for example, a polyimine, a polyamidimide, a polyether quinone, a polyoxy decylene imine, or the like, and has a molecular structure. A resin composed of a quinone imine-based polymer.

The conductive metal foil used in the present invention may, for example, be a metal foil containing copper, aluminum, stainless steel, iron, silver, palladium, nickel, cobalt, chromium, molybdenum, tungsten, or the like as a constituent element. Among the metal foils, copper foil or alloy copper foil is preferred. The thickness of the metal foil is preferably in the range of 5 to 35 μm, particularly preferably in the range of 9 to 18 μm. When the metal foil is thicker than 35 μm, the laminated plate becomes hard, resulting in deterioration of bendability and bending property. When the metal foil is thinner than 5 μm, it is difficult to adjust the tension or the like in the manufacturing step of the laminated board, and it is easy to cause defects such as wrinkles. In addition, the metal foils may be subjected to a chemical or mechanical surface treatment for the purpose of improving the adhesion.

The polybendylene precursor resin solution used in the present invention can be produced in accordance with a known method. For example, a dicarboxylic acid tetraindole and a diamine compound are dissolved in a substantially equimolar organic solvent, and stirred at 0 to 100 ° C for 30 minutes to 24 hours to obtain a reaction. Examples of the organic solvent used in the polymerization include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-N-pyrrolidone, and dimethylene. Bismuth, dimethyl sulfate, phenol, halogenated phenol, cyclohexanone, two Alkane, tetrahydrofuran, diglyme, triglyme, and the like. Two or more of the above compounds may also be used in combination. The viscosity of the polyimine precursor resin solution is preferably in the range of 500 CP to 100,000 CP. When it exceeds this range, when a coating operation is performed by a coater or the like, it is easy to cause defects such as thickness unevenness and streaking on the film.

The tetracarboxylic dianhydride and the diamine compound to be used may be one or two or more of the above compounds, as appropriate, in combination with the properties of the polyimine resin layer of the flexible laminate of the present invention. In the present invention, the tensile modulus of the polyimine resin layer must be set in the range of 3 to 6 GPa, and the coefficient of thermal expansion is set in the range of 16 to 28 ppm/° C., in order to form the metal in the formation of the flexible laminate. The adhesion between the foil and the polyimide film layer is in a good state, and it is preferable to form the polyimide layer into a plurality of layers.

When the polyimine resin layer is formed into a plurality of layers, the layer adjacent to the metal foil is preferably set to have a high thermal expansion coefficient polyimine resin layer having a thermal expansion coefficient of 30 ppm/° C. or more. In the case of a high thermal expansion coefficient polyimine resin layer, it is preferred to have a structural unit represented by the general formula (1).

In the formula, R ₁ is a group selected from at least one of the groups represented by the following structural formulas (2) and (3), and R ₂ is selected from the groups represented by the following (4) and (5). At least one type of base. Further, in the following structural formula (4), X means any one of -SO ₂ -, -CO-, and direct bonding.

When the polyimine resin layer is formed into a plurality of layers, it is preferable to provide a substrate having a tensile modulus of 4 to 8 GPa adjacent to the outer side (the side opposite to the side of the metal foil) of the above-mentioned high thermal expansion coefficient polyimide resin layer. A layer of quinone imine resin. The base polyimide layer preferably has a structural unit represented by the general formula (6):

In the formula, R ₃ is any one of -CH ₃ , -C ₂ H ₅ , -OCH ₃ or -OC ₂ H ₅ . Preferably, R ₃ is -CH ₃ . Further, in the formula, x and y respectively mean the constituent ratio of the constituent units, x is set in the range of 0.4 to 0.6, y is set in the range of 0.6 to 0.4, and x + y = 1. In the ratio of x to y, when x is less than 0.4, the thermal expansion coefficient of the polyimide resin is increased, and the dimensional stability at the time of forming the flexible laminate is lowered, and the laminate tends to be curled. On the other hand, when x is more than 0.6, the tensile modulus of polyimine will increase, and the bendability at the time of forming a flexible laminate tends to be lowered.

When the polyimine resin layer is formed into a plurality of layers, the layer structure of the flexible laminate is preferably configured to provide a layer of high thermal expansion coefficient polyimine resin on the metal foil, and sequentially laminate the substrate on the substrate. The structure of the amine resin layer. A more preferable layer structure is a metal foil/high thermal expansion coefficient polyimine resin layer/substrate polyimide film layer/high thermal expansion coefficient polyimine resin layer. Thus, after the single-sided flexible laminate having the metal foil on one side of the polyimide layer is formed, the metal foil is heat-bonded to the resin side, preferably a high thermal expansion coefficient polyimide resin. On the layer, a double-sided flexible laminate having a metal foil on both sides of the polyimide resin layer can also be produced.

The present invention adopts a production method in which a coating of a polyimide polyimide precursor solution is applied to a metal foil and heat treatment is performed, but in the drying and hardening steps in the production step, a total heating of 90 ° C or more is required. The time is set to 5 to 25 minutes. Among them, when the total heating time is shorter than 5 minutes, the polyimine resin is likely to cause problems such as foaming. On the other hand, if the total heating time exceeds 25 minutes, the productivity of the flexible laminate will deteriorate. Further, it is necessary to set the ratio of the heating time in the drying and hardening steps, the heating time of 90 ° C or more and 200 ° C or less, and the heating time of the temperature exceeding 200 ° C to 9:1 to 7:3. When the ratio of the heating time at a temperature of 90 ° C or more and less than 200 ° C is less than 70% of the total heating time, the thermal expansion coefficient of the polyimide layer becomes large, or the dimensional stability of the flexible laminate is lowered. Or the case where the laminate is curled. On the other hand, when the ratio of the heating time at a temperature lower than 200 ° C exceeds 90% of the total heating time, when the heat treatment is performed at a temperature exceeding 200 ° C, the temperature increase rate is too large, and the polyimide is likely to cause foaming or the like. . Further, when the polyimine resin layer is composed of a plurality of layers, the time for drying the polyimine precursor resin solution applied to each layer is further increased, and the hardening time is further determined. Take the heating time. Further, regarding the heating temperature exceeding 200 ° C, since the polyimide layer of the polyimide begins to deteriorate, it is preferable to set the upper limit of the heating temperature to 450 °C.

The thickness of the polyimide layer of the flexible laminate is preferably set in the range of 5 to 40 μm. Especially 8 to 35 μm is preferred. When the thickness of the polyimide layer is less than 5 μm, the strength when used as an insulating layer is weak, and when the flexible laminate is processed, the film is likely to be broken. On the other hand, if the thickness is thicker than 40 μm, the film is less likely to be bent, resulting in a decrease in the bending property of the flexible laminate. When the polyimine resin layer is a plurality of layers, a preferred ratio of the base polyimide film layer to the high thermal expansion coefficient polyimide film layer is based on the total thickness of each layer, and the base polyimide The resin layer/high thermal expansion coefficient polyimine resin layer is from 1 to 40, more preferably from 2 to 30.

In the method for producing a flexible laminate according to the present invention, the tensile modulus of the polyimide layer must be set to 3 to 6 GPa, and at the same time, the coefficient of thermal expansion must be set to 16 to 28 ppm/°C. The preferred range of the tensile modulus of the polyimide layer is from 3.5 to 5.5 GPa. When the tensile modulus is less than 3 GPa, it is difficult to handle the processing of the flexible laminate, and if it is higher than 6 GPa, the flexibility of the flexible laminate is lowered. The thermal expansion coefficient of the polyimide film layer is preferably in the range of 17 to 27 pm/°C. When the thermal expansion coefficient of the polyimine resin layer exceeds this range, since the difference between the thermal expansion coefficient and the copper foil becomes large, the dimensional change of the flexible laminate becomes large, and the laminated sheet is curled. In order to control the tensile modulus and the coefficient of thermal expansion of the polyimide layer in the above range, it is preferable to select a constituent unit suitable for forming the polyimide layer and adjust the heat treatment conditions. The manufacture of a flexible laminate is carried out.

(Example)

Hereinafter, the present invention will be described in more detail by way of examples. Further, the abbreviations used in the examples are as follows: DMAC: N,N-dimethylacetamide m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl ODA :44'-Diaminodiphenyl ether BAPP: 2,2'-bis(4-aminophenoxyphenyl)propane PMDA: pyromellitic anhydride BPDA: 3,3'-4,4'-linked Phenyltetracarboxylic dianhydride

In the examples, the evaluation of the tensile modulus and the coefficient of thermal expansion of the polyimide layer of the polyimide resin was carried out in the following manner.

Tensile modulus: Strograph made with Toyo Seiki Co., Ltd. R-1 is measured. (according to IPC-TM-650, 2.4.19)

Thermal expansion coefficient: After heating to 255 ° C using a thermostat TMA-100 manufactured by Seiko Instruments, the temperature was maintained at this temperature for 10 minutes, and then cooled at a rate of 5 ° C /min to obtain a temperature from 240 ° C to 100 ° C. °C average thermal expansion coefficient (thermal expansion coefficient).

[Synthesis Example 1]

M-TB (6 equivalents) and ODA (4 equivalents) were stirred at room temperature to dissolve the DMAc in a separable flask. Next, PMDA (9.86 equivalents) was added. Then, stirring was continued for about 3 hours to carry out a polymerization reaction, and a polybendylene precursor resin solution a was obtained. Further, DMAc used an amount of loading of m-TB, ODA, and PMDA of 16% by weight. The polyethylenimine precursor resin solution a prepared in copper foil (a steel foil BHY-22B-T made by Nikko Materials Co., Ltd., thickness: 18 μm. Hereinafter referred to as "copper foil" means copper foil) The coating was uniformly applied to a thickness of 260 μm, and heat-dried at 125 ° C for 3 minutes to remove the solvent. Then, in a temperature range of 130 ° C to 200 ° C for 8 minutes and 30 seconds, in the temperature range of 201 ° C to 360 ° C for 3 minutes and 30 seconds of heat treatment, and the oxime imidization reaction, to obtain on the copper foil A laminate having a layer of polyimine having a thickness of about 28 μm. The copper foil layer of the laminate is removed by an etching treatment to obtain a polyimide film. The tensile modulus and coefficient of thermal expansion of the polyimide film obtained by the measurement were 6.8 GPa and 12.6 ppm/°C, respectively.

[Synthesis Example 2]

The polymerization reaction was carried out in the same manner as in Synthesis Example 1 except that 5 equivalents of the m-TB system and 5 equivalents of the ODA system were used to obtain a polybendylene precursor resin solution b. Using the prepared polyimine precursor resin solution b, a polyimide film was obtained in the same manner as in Synthesis Example 1, and tensile modulus and coefficient of thermal expansion were measured, and the results were 5.9 GPa and 17.1 ppm/°C, respectively.

[Synthesis Example 3]

The polymerization reaction was carried out in the same manner as in Synthesis Example 1 except that 4 equivalents of the m-TB system and 6 equivalents of the ODA system were used, and a polybendylene precursor resin solution c was obtained. Using the prepared polyimine precursor resin solution c, a polyimide film was obtained in the same manner as in Synthesis Example 1, and the tensile modulus and the coefficient of thermal expansion were measured, and the results were 5.1 GPa and 23.1 ppm/°C, respectively.

[Synthesis Example 4]

The polymerization reaction was carried out in the same manner as in Synthesis Example 1 except that m-TB was used in an amount of 10 equivalents, and ODA was used in an amount of 0 equivalents to obtain a polyimine precursor resin solution d. Using the prepared polyimine precursor resin solution d, a polyimide film was obtained in the same manner as in Synthesis Example 1, and tensile modulus and coefficient of thermal expansion were measured, and the results were 13.8 GPa and -5.1 ppm/° C, respectively. .

[Synthesis Example 5]

The polymerization reaction was carried out in the same manner as in Synthesis Example 1 except that the m-TB system was used in an amount of 10 equivalents and the ODA system was used in an amount of 10 equivalents to obtain a polybendylene precursor resin solution e. Using the prepared polyimine precursor resin solution e, a polyimide film was obtained in the same manner as in Synthesis Example 1, and the tensile modulus and the coefficient of thermal expansion were measured, and the results were 2.7 GPa and 43.4 ppm/°C, respectively.

[Synthesis Example 6]

BAPP (10 equivalents) was stirred at room temperature to dissolve the DMAc in a separable flask. Next, PMDA (9.69 equivalents) and BPDA (0.51 equivalents) were added. Then, stirring was continued for about 3 hours to carry out a polymerization reaction, and a polybendylene precursor resin solution f was obtained. Further, DMAc uses a loading concentration of BAPP, PMDA, and BPDA of 12% by weight. A polyimine film having a thickness of about 28 μm was obtained in the same manner as in Synthesis Example 1, except that the prepared polyamidene precursor resin solution f was applied to a thickness of 350 μm, and the tensile film was measured and stretched. The modulus of elasticity and the coefficient of thermal expansion were 2.6 GPa and 50.7 ppm/°C, respectively.

[Example 1]

On the copper foil, the polyiminoimine precursor resin solution f prepared in Synthesis Example 6 was uniformly coated to a thickness of 50 μm, and dried by heating at 125 ° C to remove the solvent. Next, the polyimine precursor resin solution a prepared in accordance with Synthesis Example 1 was uniformly applied to a thickness of 190 μm so as to be laminated thereon, and dried by heating at 125 °C. Further, on top of this, the polyiminoimine precursor resin solution f was uniformly coated to a thickness of 50 μm, and heat-dried at 125 ° C. The total heating and drying time up to this point was set to 3 minutes. Then, heat treatment is performed for 8 minutes and 30 seconds in a temperature range of 130 ° C to 200 ° C, and heat treatment is performed for 3 minutes and 30 seconds in a temperature range of 201 ° C to 360 ° C to carry out a hydrazine imidization reaction to obtain copper. A laminate of a layer of polyimine having a thickness of about 28 μm was formed on the foil. The copper foil layer of the laminate is removed by an 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.

[Embodiment 2]

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

[Comparative Example 3]

The coating was carried out in the same manner as in Example 1 except that the coating of the polyimide precursor resin solution and heating and drying (125 ° C, 3 minutes) were carried out. Then, heat treatment is performed for 6 minutes in a temperature range of 130 ° C to 200 ° C, heat treatment is performed for 6 minutes in a temperature range of 201 ° C to 360 ° C, and hydrazine imidization reaction is carried out to obtain a thick layer formed on the copper foil. A laminate of about 28 μm polyimine layer. The copper foil layer of the laminate is removed by an 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 (1)

A method for producing a flexible laminated board by applying a solution of a polyimide polyimide precursor resin onto a conductive metal foil and drying and hardening the polyimide resin precursor resin solution by heat treatment The method for producing a laminated sheet is characterized in that, in the heat treatment, the total heating time of 90 ° C or more is set to a range of 5 to 25 minutes, and the heating time of 90 ° C or more and 200 ° C or less is exceeded. The ratio of the heating time at a temperature of 200 ° C is set to be 9:1 to 7:3, and a high thermal expansion coefficient polyimine resin layer having a thermal expansion coefficient of 30 ppm/° C. or higher and a base having a tensile modulus of 4 to 8 GPa are aggregated. The yttrium imide resin layer and the polyamidene resin layer having a high thermal expansion coefficient of a polyimide resin layer having a thermal expansion coefficient of 30 ppm/° C. or more are formed on the conductive metal foil, and the thickness of the polyimide layer is The range of 5 to 40 μm, and the tensile modulus of the polyimide layer is controlled to be 3 to 6 GPa, and the coefficient of thermal expansion is controlled to be in the range of 16 to 28 ppm/°C.