JP2007168123A - Flexible substrate with metal foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of manufacturing sufficiently thin flexible printed wiring board, which is sufficiently high in the peeling strength of a metal foil from a resin film even if no adhesive is used while keeping sufficient high heat resistance by a simple process. <P>SOLUTION: The manufacturing method of a flexible substrate with a metal foil, wherein the metal foil 12 is provided at least on one side of the resin film 11, has a process for bonding the metal foil 12 to the resin film 11 at 300-500°C under heating and pressure and the resin film 11 contains a non-thermoplastic polyimide resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible substrate with a metal foil that is suitably used for manufacturing a flexible printed wiring board and a method for manufacturing the same. The present invention also relates to a flexible printed wiring board.

  BACKGROUND ART A flexible printed wiring board is a flexible wiring board in which a conductor circuit is formed on an insulating film, and has recently been frequently used as a means for achieving miniaturization and high density of electronic devices. A flexible printed wiring board is manufactured by processing a metal foil of a flexible substrate with a metal foil provided with a metal foil on an insulating film as a conductor circuit. As the insulating film of the flexible substrate with metal foil, a film of non-thermoplastic polyimide resin dominates.

  Conventionally, a flexible substrate with a metal foil using a film of a non-thermoplastic polyimide resin has been manufactured by a method of bonding a film of a non-thermoplastic polyimide resin and a metal foil with an adhesive such as an epoxy resin or an acrylic resin. Therefore, the characteristics of the flexible substrate with metal foil, such as heat resistance, chemical resistance, flame retardancy, electrical characteristics or adhesion, are governed by the characteristics of the adhesive, and the excellent characteristics of the non-thermoplastic polyimide resin are sufficiently obtained. I couldn't save it.

As a method for solving this problem, a method using a thermoplastic polyimide resin that is considered to have a relatively small effect on properties as an adhesive (Patent Documents 1 to 3), a polyamic acid that is a precursor of a non-thermoplastic polyimide resin Have been proposed (Patent Documents 4 and 5) and a method of forming a metal film on a non-thermoplastic polyimide resin by vapor deposition or sputtering (Patent Document 6).
Japanese Patent Publication No. 6-93537 Japanese Patent Laid-Open No. 2005-44880 JP-A-2005-96251 JP 2005-15596 A Japanese Patent Publication No. 64-6556 Japanese Patent No. 3447070

  However, although the method of Patent Documents 1 to 3 has a relatively small influence on the characteristics, since the thermoplastic polyimide resin is used, the high heat resistance of the non-thermoplastic polyimide resin tends to be impaired. Furthermore, in the methods of Patent Documents 1 to 5, there is a problem that the flexible substrate with metal foil includes an adhesive layer and thus becomes thick.

  On the other hand, the method of Patent Document 6 requires a special apparatus such as a sputtering apparatus and may require a plating process and the like, resulting in a complicated manufacturing process.

  Therefore, the present invention provides a sufficiently thin flexible printed wiring board in a simple process while maintaining sufficiently high heat resistance and sufficiently strong to peel off the metal foil from the resin film without using an adhesive. It aims at providing the manufacturing method which can be manufactured.

  The present invention is a method for producing a flexible substrate with a metal foil in which a metal foil is provided on at least one surface of a resin film, comprising a step of thermocompression bonding the metal foil to a resin film at 300 to 500 ° C. A film is a manufacturing method containing a non-thermoplastic polyimide resin.

  According to the production method of the present invention, a metal foil is thermocompression bonded to a resin film at a temperature within the above specific range without using an adhesive, thereby maintaining a sufficiently high heat resistance and without using an adhesive. The peel strength of the foil from the resin film is sufficiently strong, and a sufficiently thin flexible printed wiring board can be produced by a simple process.

  In the manufacturing method of this invention, it is preferable to thermocompression-bond the said metal foil by a hot press or a thermal lamination. As a result, it is possible to prevent a decrease in heat resistance caused by an adhesive that is a concern when using an adhesive that is one of other manufacturing methods, and further to simplify the process of forming an adhesive layer. In addition, while maintaining high heat resistance, it has become possible to produce a flexible printed wiring board that is sufficiently thin and sufficiently thin to peel from a resin film of a metal foil in a simple process.

  The metal foil is preferably thermocompression bonded in an atmosphere having an oxygen concentration of 5% by volume or less. Thereby, oxidation of the metal foil of the flexible substrate with metal foil can be prevented.

  The metal foil is preferably a copper foil. Thereby, the circuit workability of the flexible printed wiring board and the physical properties of the wiring material are improved.

  The flexible substrate with metal foil of the present invention is obtained by the production method of the present invention. By using this flexible substrate with metal foil, a sufficiently reliable flexible printed wiring board can be produced in a simple process.

  In the flexible substrate with metal foil of the present invention, the glass transition temperature of the resin film is 300 ° C. or more, the relative dielectric constant of 5 GHz is 3.3 or less, and the linear thermal expansion coefficient is 25 ppm / ° C. or less. The peel strength from the resin film is preferably 0.5 kN / m or more. Thereby, the reliability of a flexible printed wiring board can further be improved.

  The flexible printed wiring board of the present invention forms a conductor pattern by removing a part of the metal foil of the flexible substrate with metal foil, or removes the metal foil of the flexible substrate with metal foil and exposes the resin. A conductor pattern is formed on a film. These flexible printed wiring boards are sufficiently reliable because they are manufactured using the flexible substrate with metal foil of the present invention.

  According to the production method of the present invention, while maintaining sufficiently high heat resistance, the peel strength from the resin film of the metal foil is sufficiently strong without using an adhesive, and a sufficiently thin flexible printed wiring board, It becomes possible to manufacture with a simple process. Further, the present invention makes it possible to manufacture a flexible printed wiring board that is less likely to oxidize the metal foil and is sufficiently reliable for use.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of a flexible substrate with metal foil of the present invention. A flexible substrate 1 a with metal foil shown in FIG. 1 is composed of a laminate 10 in which a metal foil 12 is provided in close contact with one surface of a resin film 11.

  The flexible substrate with metal foil of the present invention may be one in which the metal foil 12 is in close contact with both surfaces of the resin film 11 in addition to the embodiment like the flexible substrate with metal foil 1a of FIG.

  A flexible printed wiring board can be obtained by a method of removing a part of the metal foil from the flexible substrate and forming a conductor pattern. FIG. 2 is a sectional view showing an embodiment of the flexible printed wiring board of the present invention.

  A flexible printed wiring board 2 a shown in FIG. 2 includes a resin film 11 and a conductor pattern 20 formed on one surface of the resin film 11. The conductor pattern 20 is formed by removing a part of the metal foil 12 of the flexible substrate with metal foil 1a and patterning it. The metal foil 12 is patterned by a method such as photolithography. Alternatively, the flexible printed circuit board 2a can be obtained by removing the metal foil 12 from the flexible board with metal foil 1a and drawing a conductive material directly on the exposed resin film 11 to form a conductor pattern.

  The flexible wiring board of the present invention may be one in which a conductor pattern is formed on both surfaces of the resin film 11 in addition to the embodiment like the flexible wiring board 2a of FIG.

  The resin film 11 is a film containing a non-thermoplastic polyimide resin described later as a main component. The content ratio of the non-thermoplastic polyimide resin in the resin film 11 is preferably 50% by mass or more of the entire resin film 11, and the resin film 11 is more preferably substantially made of a non-thermoplastic polyimide resin.

  The linear thermal expansion coefficient of the resin film 11 is preferably 25 ppm / ° C. or less, and more preferably 10 to 25 ppm / ° C. The coefficient of linear thermal expansion is an index indicating the rate of elongation of the material due to heat. When two or more different materials are bonded, the difference in the coefficient of linear thermal expansion between the materials from the viewpoint of the reliability of the flexible printed wiring board 2a. Is desired to be small. Generally, the linear thermal expansion coefficient of the metal foil is 10 to 25 ppm / ° C. (for example, stainless steel 10 ppm / ° C., copper alloy 20 ppm / ° C., aluminum alloy 22 ppm / ° C.). When a resin film with a linear thermal expansion coefficient exceeding 25 ppm / ° C is bonded to these metal foils, warping is likely to occur when bonded or heated after bonding, resulting in wiring breakage or molding defects. Etc., and the reliability of the flexible printed wiring board 2a tends to decrease.

  The linear thermal expansion coefficient of the resin film 11 can be easily measured by a method using TMA. When measuring the linear thermal expansion coefficient by TMA, for example, a test piece having a thickness of 0.025 mm, a width of 13 mm, and a length of 15 mm is used from 50 ° C. by using “TMA2940” (trade name) manufactured by TA Instruments. After raising the temperature to 300 ° C. at a load of 0.5 gf and 10 ° C./min, cooling to room temperature, again raising the temperature from 50 ° C. to 350 ° C. at a load of 0.5 gf and 10 ° C./min, 50 ° C. to 250 ° C. The linear thermal expansion coefficient can be obtained by calculating the linear thermal expansion coefficient in the range.

  In recent years, it has been desired to connect wiring by using solder (melting point: 288 ° C.) that does not contain lead for environmental measures. For this reason, it is preferable that the glass transition temperature of the resin film 11 used for the flexible substrate 1a with metal foil is 288 degreeC or more, and it is more preferable that it is 300 degreeC or more.

  In addition, the said glass transition temperature is an inflection point which appears by glass transition in the graph which shows the relationship between the linear thermal expansion coefficient and temperature obtained when the linear thermal expansion coefficient of the resin film 11 is measured on the same conditions as the above. A tangent line is drawn on the preceding and following curves, and is obtained from the intersection of these two tangent lines.

  The relative dielectric constant of the resin film 11 at 5 GHz is preferably 3.3 or less. The relative dielectric constant is an index indicating the insulating property of the resin film. When narrowing the pitch between copper wirings or reducing the film thickness as means for achieving miniaturization and high density of electronic equipment, it is desirable to reduce the relative dielectric constant of the resin film. Further, electronic devices are desired to operate at a high frequency, and it is particularly desired that the dielectric constant in the gigahertz band is low. The relative dielectric constant of the resin film 11 is preferably low, but the lower limit is usually about 2.5.

  The relative dielectric constant of the resin film 11 can be easily measured by a method using a cavity resonator perturbation method complex dielectric constant evaluation apparatus (hereinafter referred to as a cavity resonator). When measuring the relative dielectric constant using a cavity resonator, for example, “CP511” (trade name) manufactured by Kanto Electronics Application Development Co., Ltd., resin film having a thickness of 0.6 mm, a width of 1.8 mm, and a length of 80 mm The measurement can be performed on three test pieces, and the average can be used as the relative dielectric constant. When the thickness of the test piece is insufficient, a predetermined thickness can be secured by stacking a plurality of resin films.

  The peel strength of the metal foil 12 from the resin film 11 is preferably 0.5 kN / m or more. The peel strength of the metal foil from the resin film, that is, the adhesive strength, relates to the reliability of the flexible printed wiring board 2a when the wiring is formed by etching or the like. In order to improve reliability, it is desired that peeling and disconnection do not occur when subjected to stress such as repeated bending or thermal history. The peel strength of the metal foil 12 from the resin film 11 is the stress when the metal foil is peeled off at an angle of 90 degrees with respect to the main surface of the resin film for a test piece having a thickness of 0.025 mm and a width of 10 mm. Is the maximum value. This peel strength is preferably large.

  The present inventors measured the linear thermal expansion coefficient and the like by the above method. However, the measurement method is not limited to this, and it can be compared by correcting the values measured by methods having different machine differences, sample shapes, and other conditions.

  Specific examples of the metal foil 12 include copper, aluminum, iron, gold, silver, nickel palladium, chromium, molybdenum, or an alloy thereof. In order to increase the adhesive strength with the resin film 11, the surface thereof is mechanically or chemically treated by chemical roughening, corona discharge, sanding, plating, aluminum alcoholate, aluminum chelate, silane coupling agent, etc. Also good. When the roughness of the surface of the metal foil is increased, the adhesive force tends to increase, but there is also a tendency that transmission loss increases and fine processing becomes difficult. Among the metal foils, copper or an alloy foil containing copper is preferably used, and copper foil is more preferably used from the viewpoint of circuit processability and physical properties of the wiring material. As the copper foil, either a general rolled foil or an electrolytic foil can be used.

  The flexible substrate 1a with metal foil can be easily manufactured by thermocompression bonding of a metal foil of a resin film containing a non-thermoplastic polyimide resin at 300 to 500 ° C.

  The resin film 11 is, for example, a coating step of applying a varnish containing at least one of a non-thermoplastic polyimide resin and a precursor thereof and a solvent onto a releasable substrate, and the ratio of the solvent in the varnish as a whole. A drying process for forming a resin composition layer by removing until ˜60 wt%, and a solvent remaining in the resin composition layer by heating the resin composition layer to 250 to 550 ° C. in a reducing atmosphere A resin film forming step of forming a resin film containing a non-thermoplastic polyimide resin by forming a non-thermoplastic polyimide resin from a non-thermoplastic polyimide resin precursor, and releasing the resin film from the substrate And a manufacturing method comprising the steps.

  The varnish used in the coating step includes one or more of at least one of a non-thermoplastic polyimide resin and a precursor thereof. The non-thermoplastic polyimide resin precursor is converted into a non-thermoplastic polyimide resin mainly by heating in the resin film forming step.

  Additives such as curing agents such as epoxy compounds, acrylic compounds, diisocyanate compounds, phenol compounds, fillers, particles, coloring materials, leveling agents, coupling agents, etc. can be optionally added to the varnish. However, when more curing components and / or additional components than the amount of the non-thermoplastic polyimide resin and its precursor are added, the reliability of the resin film 11 tends to decrease.

  The ratio of the non-thermoplastic polyimide resin and its precursor to the entire varnish is preferably 8 to 40% by mass, and the viscosity of the varnish is preferably 10 to 40 Pa · s. If the varnish viscosity is outside this range, repelling or the like will occur in the coating process, resulting in poor appearance or reduced film thickness accuracy.

  The varnish can be applied to the metal foil using a roll coater, comma coater, knife coater, doctor blade flow coater, hermetic coater, die coater, lip coater or the like. In this case, the varnish is discharged from the film-forming slit and applied as uniformly as possible.

  Examples of the releasable substrate on which the varnish is applied include a resin film, a SUS plate, and a glass plate that have been subjected to a release treatment with a silicon compound, a fluorine compound, or the like.

  The non-thermoplastic polyimide resin is a polymer having an imide group in the main chain and does not exhibit thermoplasticity. This non-thermoplastic polyimide resin has, for example, a polymer chain represented by the following general formula (1).

  The precursor of the non-thermoplastic polyimide resin is a polyamic acid having an amide group and a carboxyl group. The polyamic acid generates a polyimide resin by reacting an amide group and a carboxyl group by heating. At this time, a non-thermoplastic polyimide resin can be obtained by appropriately selecting the type of polyamic acid. The polyamic acid has, for example, a polymer chain represented by the following general formula (2).

In the formulas (1) and (2), R ¹ represents a residue obtained by removing an amino group from a diamine or a residue obtained by removing an isocyanate group from a diisocyanate, and R ² represents a carboxylic acid of an aromatic tetracarboxylic acid derivative. The residue excluding the acid induction part is shown. n represents an integer of 1 or more.

  A polyamic acid can be synthesized by reacting a diamine and / or diisocyanate with a tetracarboxylic acid and / or a derivative thereof.

  As the diamine, an aromatic diamine is preferable. Specific examples of the aromatic diamine include p, m or o-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, diaminodiurene 1,5-diaminonaphthalene, 2,6. -Diaminonaphthalene, benzidine, 4,4'-diaminoterphenyl, 4,4 '' '-diaminoquaterphenyl, 4,4'-diaminodiphenylmethane, 1,2-bis (anilino) ethane, 4,4'-diamino Diphenyl ether, 4,4′-diaminodiphenyl sulfone, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 2,6-diaminonaphthalene, 3,3- Dimethylbenzidine, 3,3′-dimethyl-4,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4 ′ Diaminodiphenylmethane, diaminotoluene, diaminobenzotrifluoride, 1,4-bis (p-aminophenoxy) benzene, 4,4'-bis (p-aminophenoxy) biphenyl, 2,2'-bis [4- (p- Aminophenoxy) phenyl] propane, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) decafluorobutane, 2,2-bis [4- (p-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [ 4- (3-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (2-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphenyl] hexafluoropropane, 2,2-bis [4- (4-amino) Phenoxy) -3,5-ditrifluoromethylphenyl] hexafluoropropane, p-bis (4-amino-2-trifluoromethylphenoxy) benzene, 4,4′-bis (4-amino-2-trifluoromethylphenoxy) ) Biphenyl, 4,4′-bis (4-amino-3-trifluoromethylphenoxy) biphenyl, 4,4′-bis (4-amino-2-trifluoromethylphenoxy) diphenylsulfone, 4,4′-bis (3-Amino-5-trifluoromethylphenoxy) diphenylsulfone, 2,2-bis [4- (4-amino-3-trif Oro-methylphenoxy) phenyl] hexafluoropropane and the like.

  As diamine, the siloxane diamine represented by following General formula (3) can also be used.

In formula (3), R ³ represents a monovalent organic group, and R ⁴ represents a divalent organic group. Each R ³ and each R ⁴ may be the same as or different from each other. n represents an integer of 1 or more.

  As the diisocyanate, an aromatic diisocyanate obtained by a reaction of the above aromatic diamine with phosgene or the like is preferable. Specific examples of the aromatic diisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, and phenylene-1,3-diisocyanate.

  As the tetracarboxylic acid, a tetracarboxylic acid having two sets of two adjacent carboxyl groups is preferable. Specific examples of tetracarboxylic acid include pyromellitic acid, 2,3,3 ′, 4′-tetracarboxydiphenyl, 3,3 ′, 4,4′-tetracarboxydiphenyl, 3,3 ′, 4,4 ′. -Tetracarboxydiphenyl ether, 2,3,3 ', 4'-tetracarboxydiphenyl ether, 3,3', 4,4'-tetracarboxybenzophenone, 2,3,3 ', 4'-tetracarboxybenzophenone, 2,3 , 6,7-tetracarboxynaphthalene, 1,4,5,7-tetracarboxynaphthalene, 1,2,5,6-tetracarboxynaphthalene, 3,3 ′, 4,4′-tetracarboxydiphenylmethane, 2,2 -Bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ′, 4,4′-tetracarboxydiphenyl Sulfone, 3,4,9,10-tetracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxy) Phenoxy) phenyl] hexafluoropropane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid. Of these tetracarboxylic acids, aromatic tetracarboxylic acids are more preferred.

  The tetracarboxylic acid derivative is preferably an esterified product, acid anhydride, or chloride of the tetracarboxylic acid, more preferably the acid anhydride of the tetracarboxylic acid, and the acid anhydride of the aromatic tetracarboxylic acid. Particularly preferred.

  Among the specific examples of the above diamine and / or diisocyanate and tetracarboxylic acid and / or tetracarboxylic acid derivative, examples of the combination that gives a non-thermoplastic polyimide resin after reaction include m-phenylenediamine and p-phenylenediamine. , A diamine selected from the group consisting of 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone and 2,2′-bis [4- (p-aminophenoxy) phenyl] propane and / or derived from these diamines Diisocyanates, and tetracarboxylic acids selected from the group consisting of pyromellitic acid, 3,3 ′, 4,4′-tetracarboxydiphenyl and 3,3 ′, 4,4′-tetracarboxybenzophenone and / or The combination of tetracarboxylic acid anhydrides It is.

  In the reaction of diamine and / or diisocyanate with tetracarboxylic acid and / or derivative thereof, the ratio of the number of moles of diamine and / or diisocyanate to the number of moles of tetracarboxylic acid and / or derivative thereof is set to 0. It is preferable to set it to 95-1.05. If the ratio during the reaction is outside this range, the molecular weight of the polyamic acid to be produced and the polyimide resin produced therefrom will be small, the film will become brittle, it will be difficult to maintain the shape of the film, etc. The physical properties of the film tend to decrease.

  The above reaction is usually performed using N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, The reaction is carried out in a solvent such as γ-butyrolactone, cresol, phenol, halogenated phenol, cyclohexane, dioxane and the like. The reaction temperature is preferably 0 to 200 ° C.

  During the reaction, a modifying compound can be added to introduce a crosslinked structure or a ladder structure into the non-thermoplastic polyimide resin. As the modifying compound in this case, for example, a compound represented by the following general formula (4) is used. By using this modifying compound, a pyrrolone ring, an isoindoloquinazolinedione ring, or the like is introduced into the non-thermoplastic polyimide resin.

R ⁵ represents a (2 + x) -valent aromatic organic group, Z represents NH ₂ , CONH ₂ , SO ₂ NH ₂ or OH, and is positioned ortho to the amino group. x represents 1 or 2.

  As the other modifying compound, a compound having a polymerizable unsaturated bond, which is a derivative of amine, diamine, dicarboxylic acid, tricarboxylic acid or tetracarboxylic acid can be used. Thereby, a crosslinked structure is formed in the polyimide resin. Examples of such a compound include maleic acid, nadic acid, tetrahydrophthalic acid, and ethynylaniline.

  As a method for thermocompression bonding the metal foil to the resin film, a hot press or a thermal lamination is preferable. In order to prevent oxidation of the copper foil and the substrate, it is preferable to thermocompression-bond the metal foil in an atmosphere having an oxygen concentration of 5% by volume or less. In the case of hot pressing, it is preferable to press under reduced pressure. In the case of thermal lamination, it is preferably performed in nitrogen gas, more preferably in a reducing atmosphere formed by a mixed gas of nitrogen gas and hydrogen gas of 0.1% to less than 4% by volume of the whole. preferable.

  In either case, it is essential to heat to 300 ° C. to 500 ° C., preferably 350 ° C. to 500 ° C. When heated to a temperature exceeding 500 ° C., it may be accompanied by thermal decomposition of the polyimide resin. In the case of thermal lamination, the portion where the metal foil and the resin film are bonded is heated to 300 ° C. to 500 ° C. in advance, and further, the thermocompression bonding roll and the metal foil and the resin film are bonded. Bonding can be effectively performed by keeping the temperature at 300 ° C. to 500 ° C. Any device may be used for such heating and heat retention, but it is preferable to use a far infrared heater (IR) with high thermal efficiency.

  Further, it is essential to pressurize together with heating. In the case of hot pressing, the pressure is 1 MPa or more, preferably 2 to 5 MPa, and in the case of thermal lamination, the pressure is 50 kN / m or more, preferably 100 to 400 kN / m.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.

  The linear thermal expansion coefficient, glass transition temperature, relative dielectric constant and peel strength of the metal foil of the resin film of the flexible substrate with metal foil were measured by the following procedure.

(Linear thermal expansion coefficient)
A rectangular test piece having a width of 5 mm and a length of 15 mm was cut out from a resin film obtained by removing the metal foil of the flexible substrate with metal foil by etching. The tensile mode of this test piece was measured using “TMA2940” manufactured by TA Instruments. The linear thermal expansion coefficient was calculated from the elongation amount of 50 to 250 ° C.

(Glass-transition temperature)
The glass transition temperature of the resin film is obtained from the intersection of these two tangent lines by drawing a tangent to the curve before and after the glass transition region in the graph of the relationship between the linear expansion coefficient and the temperature obtained by the above-described measurement of the linear expansion coefficient. It was.

(Relative permittivity)
A rectangular test piece having a width of 2 mm and a length of 80 mm was cut out from a resin film obtained by etching away the metal foil of the flexible substrate with metal foil, and dried at 105 ° C. for 30 minutes. In a state where 200 dried test pieces were stacked, the relative dielectric constant was measured at 5 GHz by the cavity resonator method. The measurement was performed using “CP511” manufactured by Kanto Electronics Application Development Co., which is a cavity resonator, and Agilent “E7350A”, which is a network analyzer.

(Stripping strength of metal foil)
A test piece having a metal foil with a width of 1 mm was prepared by etching in a state where the metal foil of the flexible substrate with metal foil was masked with a width of 1 mm. A load was measured when a 1 mm wide metal foil part was peeled off at a peeling angle of 90 degrees and a peeling speed of 50 mm / min, and the maximum load at that time was taken as the peel strength.

(Example of synthesis process)
While flowing about 300 ml / min of nitrogen into a 60 L stainless steel reaction kettle equipped with a thermocouple, stirrer and nitrogen inlet, 867.8 g of p-phenylenediamine and 1606.9 g of 4,4′-diaminodiphenyl ether and N-methyl 2-kg pyrrolidone was added and stirred. While this solution was cooled to 50 ° C. or lower with a water jacket, 4722.2 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was gradually added to obtain polyamic acid and N-methyl-2-pyrrolidone. A viscous polyamic acid varnish containing was obtained. Then, in order to improve the coating workability, cooking was performed at 80 ° C. until the rotational viscosity of the varnish reached 10 Pa · s.

(Drying process example 1)
The polyamic acid varnish obtained in the above synthesis example was applied on the roughened surface of the copper foil to a thickness of 50 μm using a coating machine (comma coater). As the copper foil, a rolled copper foil (trade name “BHY-02B-T” manufactured by Nikko Materials) having a width of 540 mm and a thickness of 12 μm was used. Using a forced air drying oven, the solvent was removed from the polyamic acid varnish applied to the copper foil until the residual solvent amount was 20% by weight to form a resin composition layer containing polyamic acid.

(Drying process example 2)
The polyamic acid varnish obtained in the above synthesis process example was applied to a thickness of 50 μm on PET which was subjected to a release treatment using a coating machine (comma coater). As the release-treated PET, a width of 600 mm and a thickness of 25 μm (trade name “Purex A70” manufactured by Teijin DuPont) were used. Using a forced air drying oven, the solvent was removed from the polyamic acid varnish applied to the release-treated PET to a residual solvent amount of 20% by weight to form a resin composition layer containing polyamic acid.

(Film forming process example 1)
The resin composition layer containing the polyamic acid obtained in the drying process example 1 is formed with a mixed gas composed of nitrogen gas and hydrogen gas of 0.1% by volume or more and less than 4% by volume using a hot air circulation oven. Under the atmosphere, it was continuously heated at 250 ° C. to 400 ° C. to prepare a resin film with a single-sided metal foil.

(Film forming process example 2)
The resin composition layer containing the polyamic acid obtained in the drying process example 2 is peeled off from the release-treated PET and heated stepwise from 250 ° C. to 400 ° C. in a nitrogen gas atmosphere using a hot air circulating oven. A resin film was prepared.

Example 1
Using a thermal lamination apparatus manufactured by Yuri Roll Machinery Co., Ltd., the above-mentioned single-sided metal foil-attached resin film was bonded to the glossy surface (Rz = 1.2) of the electrolytic copper foil. The thermal lamination was performed under the conditions of a heating heater temperature and a heating roll temperature of 350 ° C. to 400 ° C., a pressurizing linear pressure of 100 to 400 kN / m, and a roll speed of 0.5 m / min. .

(Example 2)
Using a thermal lamination apparatus manufactured by Yuri Roll Machinery Co., Ltd., the above-mentioned single-sided metal foil-attached resin film and the roughened surface of the electrolytic copper foil (Rz = 1.9) were bonded. The conditions for thermal lamination were the same as in Example 1.

(Example 3)
Using a 70 t hot press machine manufactured by Meiki Seisakusho, the resin film and the glossy surface (Rz = 1.2) of the electrolytic copper foil were bonded together. The hot pressing was performed under a reduced pressure of about 20 mmHg at a heating temperature of 350 ° C., a pressure of 4 MPa, a heating time of 1 hour.

(Comparative Example 1)
Using a thermal laminating device manufactured by Yuri Roll Machinery Co., Ltd., the glossy surface (Rz = 1.2) of the single-sided metal foil-attached resin film and the electrolytic copper foil was bonded. The heat lamination conditions were a heating heater temperature and a heating roll temperature of 260 ° C. to 300 ° C., a pressurizing linear pressure of 100 to 400 KN / m, and a roll speed of 0.5 m / min.

  As shown in Table 1, the flexible substrate with metal foils of the examples exhibited good characteristics with respect to the peel strength of the copper foil, the glass transition temperature, the relative dielectric constant, and the linear thermal expansion coefficient of the resin. This means that the flexible substrate with metal foil obtained by the present invention has a sufficiently strong peel strength while maintaining a sufficiently high heat resistance. The flexible substrate of Comparative Example 1 was not strong enough to peel off the copper foil.

It is sectional drawing which shows one Embodiment of the flexible substrate with metal foil of this invention. It is sectional drawing which shows one Embodiment of the flexible printed wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Flexible board with metal foil, 2a ... Flexible printed wiring board, 10 ... Laminated body, 11 ... Resin film, 12 ... Metal foil, 20 ... Conductor pattern.

Claims (8)

A method for producing a flexible substrate with a metal foil in which a metal foil is provided on at least one surface of a resin film,
A step of thermocompression bonding the metal foil to the resin film at 300 to 500 ° C .;
The said resin film is a manufacturing method containing a non-thermoplastic polyimide resin.   The manufacturing method of Claim 1 which thermocompression-bonds the said metal foil with a hot press or a heat lamination.   The manufacturing method of Claim 1 or 2 which thermocompression-bonds the said metal foil in the atmosphere whose oxygen concentration is 5 volume% or less of the whole.   The manufacturing method as described in any one of Claims 1-3 whose said metal foil is copper foil.   The flexible substrate with metal foil obtained by the manufacturing method as described in any one of Claims 1-4. The resin film has a glass transition temperature of 300 ° C. or higher, a relative dielectric constant of 5 GHz of 3.3 or lower, and a linear thermal expansion coefficient of 25 ppm / ° C. or lower.
The flexible substrate with metal foil according to claim 5, wherein the peel strength of the metal foil from the resin film is 0.5 kN / m or more.   A flexible printed wiring board in which a conductor pattern is formed by removing a part of the metal foil of the flexible substrate with metal foil according to claim 5. The flexible printed wiring board which removed the metal foil of the flexible substrate with a metal foil of Claim 5 or 6, and formed the conductor pattern on the exposed resin film.

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