JP7506391B2 - Metal-polyimide laminate - Google Patents

Description

The present invention relates to a metal-polyimide laminate, a polyimide resin varnish used therein, and a method for producing a metal-polyimide laminate.

Conventionally, laminates of metal and polyimide have been manufactured by various methods. Patent Document 1 discloses a flexible wiring board in which a polyimide layer of a specific structure is formed by applying directly onto a metal conductor such as copper foil. However, in the method disclosed in Patent Document 1, since the polyimide layer is formed by applying directly onto the metal conductor, the surface of the resulting polyimide layer is easily affected by the surface condition of the metal conductor. Therefore, if the surface of the metal conductor is uneven, there is a problem that unevenness is also likely to be formed on the surface of the polyimide layer. On the other hand, if the surface of the metal conductor is not uneven, there is a problem that sufficient adhesive strength cannot be obtained between the polyimide layer and the metal conductor.

Patent Document 2 discloses a method for producing a metal-coated polyimide substrate in which a metal layer is formed on a polyimide resin layer by electroless plating. However, in the method disclosed in Patent Document 2, the polyimide layer is not supported by a support material. Therefore, when forming a metal layer using electroless plating, warping and wrinkles are likely to occur, making it difficult to use a thin polyimide resin layer.

Patent Document 3 discloses a TAB tape carrier in which an insulating layer such as a polyimide resin layer is formed on a reinforcing layer made of stainless steel, a conductor layer is further formed on the insulating layer, and then a part of the reinforcing layer is removed by etching. However, the TAB tape carrier disclosed in Patent Document 3 does not take into consideration the thermal expansion coefficient of the reinforcing layer. That is, Patent Document 3 uses SUS304, which has a large thermal expansion coefficient of 17 ppm/K to 19 ppm/K, as an example, and does not take into consideration the thermal expansion coefficient of the insulating layer such as polyimide. Therefore, when the insulating layer such as polyimide is made thin, problems such as warping and wrinkles are likely to occur after the metal support layer is removed by etching, and there is also a large change in dimensions, making it difficult to apply to high-definition patterning.

Japanese Patent Application Laid-Open No. 04-274382 Japanese Patent Application Laid-Open No. 05-235114 JP 2004-134442 A

The object of the present invention is to provide a metal-polyimide laminate suitable for circuit boards, deposition masks, etc., a polyimide resin varnish for use therein, and a method for producing a metal-polyimide laminate.

The inventors discovered that a metal-polyimide laminate with excellent thickness accuracy, flatness, and dimensional stability can be obtained by coating a resin varnish that gives a polyimide resin film with a linear expansion coefficient of -5 to 15 ppm/K on a supporting substrate with a removable thermal expansion coefficient in the range of -5 to 12 ppm/K, forming a metal layer on top of the resin varnish by plating, and then removing part or all of the supporting substrate, thus completing the present invention.

Specifically, the metal-polyimide laminate of this embodiment includes a polyimide resin film and a metal layer. The polyimide resin film is formed by curing a polyimide varnish containing a polyimide resin, and has a thermal expansion coefficient of −5 ppm/K to 15 ppm/K. The metal layer is formed on the polyimide resin film by plating.
The polyimide resin film preferably has a thickness of 1 μm to 15 μm.
The metal layer preferably comprises copper or nickel.
The polyimide-based varnish of the present embodiment is for forming the polyimide-based resin film in the metal-polyimide laminate. The polyimide-based resin is synthesized from a diamine and a tetracarboxylic dianhydride, and the diamine preferably contains 70 mol % or more of 2,2'-dimethyl-4,4'-diaminobiphenyl or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.
The concentration of the polyimide resin is preferably 1% by mass to 15% by mass.
The polyimide-based varnish preferably has a viscosity at 25° C. of 100 mPa·s to 100,000 mPa·s.
Further, the method for producing the metal-polyimide laminate of the present embodiment includes the steps of:
A step of applying a polyimide-based resin varnish to a supporting substrate having a thermal expansion coefficient of −5 ppm/K to 12 ppm/K to form a polyimide-based resin film having a thermal expansion coefficient of −5 ppm/K to 15 ppm/K;
forming a metal layer by plating on a surface of the polyimide-based resin film opposite to the supporting substrate;
a step of removing a part or all of the supporting substrate provided on the opposite side of the metal layer with respect to the polyimide-based resin film after forming the metal layer;
including.

The following describes in detail the embodiments of the polyimide resin varnish, the metal-polyimide laminate, and the method for producing the same.

(Polyimide resin varnish)
The polyimide-based resin varnish of this embodiment (hereinafter, simply referred to as "resin varnish") is produced by using diamine and tetracarboxylic dianhydride as raw materials. The resin varnish is capable of forming a polyimide-based resin film having a thermal expansion coefficient in the range of -5 ppm/K to 15 ppm/K. This resin varnish is applied to a supporting substrate having a removable thermal expansion coefficient in the range of -5 ppm/K to 12 ppm/K to form a polyimide-based resin film, and then a metal layer is formed on the polyimide-based resin film by plating. After the metal layer is formed, the supporting substrate is partially or entirely removed. As a result, the flatness, heat resistance, and mechanical properties of the metal-polyimide laminate are improved, and the adhesion between the metal layer and the polyimide-based resin film is improved.

In this embodiment, the resin varnish is a solution of polyimide resin that forms a polyimide resin film of -5 ppm/K to 15 ppm/K. Polyimide resins are not limited to polyimides, but include all polymers having imide bonds such as polyamideimide, polyesterimide, and polyetherimide, as well as polyimide precursor resins such as polyamic acid that give polymers having imide bonds through an imidization reaction. Polyimide resins also include polymers in which a portion of polyamic acid has been imidized, and in which imide bonds and amide bonds are mixed.

Several examples of the method for producing the resin varnish will be described.
(Production method 1)
Using diamine and tetracarboxylic dianhydride as raw materials, a polyamic acid varnish, which is a precursor of polyimide, is synthesized by solution polymerization in a solvent. The obtained polyamic acid varnish becomes the resin varnish of this embodiment. In this case, the diamine and the tetracarboxylic dianhydride may be reacted by any addition method, such as a method in which the diamine is dissolved or dispersed in a solvent and the tetracarboxylic dianhydride is added thereto for polymerization, a method in which the tetracarboxylic dianhydride is dissolved or dispersed in a solvent and the diamine is added thereto for polymerization, a method in which the diamine and the tetracarboxylic dianhydride are added simultaneously to the solvent, or a method in which the diamine and the tetracarboxylic dianhydride are added alternately. In this case, the polymerization of the diamine and the tetracarboxylic dianhydride is preferably performed with stirring. It may also be performed under an inert atmosphere such as nitrogen or argon.

(Production method 2)
The polyamic acid varnish obtained by the above (Production Method 1) is further converted into polyimide by thermal imidization or chemical imidization, and the polyimide solution is used as the polyimide-based resin varnish of this embodiment.
Of the above two methods, the method of converting a polyamic acid varnish into a polyimide-based resin varnish as in (Production Method 1) is easy to synthesize and is preferable in terms of controlling the thermal expansion coefficient of the resulting polyimide-based resin film within the range of -5 ppm/K to 15 ppm/K.

As the diamine used in the production of the resin varnish of this embodiment, any diamine can be used as long as it has a linear expansion coefficient of -5 ppm/K to 15 ppm/K. Examples of diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, paraphenylenediamine, metaphenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,3'-diaminodiphenyl methane, 3,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl methane, 2,2-bis(4-aminophenyl)propane propane, 2,2-bis(3-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 1,3- Bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 3,4'-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(4 bis[4-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenyl)sulfone, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenyl)sulfone , bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, 2,2-bis[4-( 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane Suitable diamines include 2,2'-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, etc. In addition, it is preferable to use 2,2'-dimethyl-4,4'-diaminobiphenyl or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl in an amount of 70 mol % or more based on the total amount of diamines used in order to control the thermal expansion coefficient to -5 ppm/K to 15 ppm/K and obtain a polyimide-based resin film having excellent mechanical strength. In particular, it is more preferable to use 2,2'-dimethyl-4,4'-diaminobiphenyl or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl in an amount of 80 mol% or more relative to the total amount of diamines used.

Tetracarboxylic dianhydrides used in the production of resin varnish include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)diphthalic dianhydride, 1,4-hydroquinone dibenzoate-3,3',4,4'-tetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, etc. In particular, to obtain a resin varnish that gives a polyimide resin film with a linear expansion coefficient of -5 ppm/K to 15 ppm/K, it is preferable to use pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

The diamine and tetracarboxylic dianhydride used in the production of the resin varnish are roughly equal in molar amounts. On the other hand, the molar amount of either the diamine or the tetracarboxylic dianhydride may be intentionally increased slightly in order to control the molecular weight of the polyimide resin or to improve the adhesive strength of the metal layer formed by plating on the polyimide resin film obtained from the resin varnish.

The concentration of the polyimide resin in the resin varnish is determined taking into consideration the thickness and workability of the polyimide resin film obtained by applying it to the support substrate. In this case, the concentration of the polyamide resin is preferably 1% by mass to 20% by mass, more preferably 3% by mass to 15% by mass, and even more preferably 5% by mass to 10% by mass. If the concentration of the polyimide resin in the resin varnish is less than 1% by mass, the thickness of the polyimide resin film obtained by applying it to the support substrate will be too small, and it may be difficult to obtain a polyimide resin film with sufficient strength. Furthermore, if the concentration of the polyimide resin exceeds 20% by mass, the viscosity of the resin varnish increases, and it may be difficult to form a polyimide resin film with a uniform thickness.

The viscosity of the resin varnish is appropriately set taking into consideration the ease of application of the resin varnish to the supporting substrate. To facilitate application and obtain a polyimide resin film with a uniform thickness, the viscosity of the resin varnish is preferably in the range of 100 mPa·s to 100,000 mPa·s, more preferably in the range of 500 Pa·s to 50,000 mPa·s, and even more preferably in the range of 1,000 Pa·s to 10,000 mPa·s.

(Metal-Polyimide Laminate)
The metal-polyimide laminate of the present embodiment is produced by applying the above-mentioned resin varnish to a supporting substrate having a removable thermal expansion coefficient in the range of -5 ppm/K to 12 ppm/K to form a polyimide-based resin film having a thermal expansion coefficient of -5 ppm/K to 15 ppm/K, preferably -3 ppm/K to 12 ppm/K, and more preferably -2 ppm/K to 5 ppm/K, and then forming a metal layer by a plating method, and then removing a part or all of the supporting substrate.

The supporting substrate used in the manufacture of the metal-polyimide laminate of this embodiment can be any supporting substrate that has a thermal expansion coefficient in the range of -5 ppm/K to 12 ppm/K and can be removed after forming a polyimide resin film and a metal layer thereon, and performing necessary processing such as external processing and drilling, if necessary. Examples of supporting substrates include metal foils such as stainless steel foil and Invar foil, glass plate, ceramic plate, etc. By using a metal foil with a thermal expansion coefficient in the range of -5 ppm/K to 12 ppm/K as the supporting substrate, the supporting substrate can be removed by an etching method. Examples of suitable metal foils with a thermal expansion coefficient in the range of -5 ppm/K to 12 ppm/K include SUS410, SUS430, and Invar foil. Another preferred supporting substrate is a glass plate. When a glass plate is used as the supporting substrate, dimensional changes due to thermal changes are significantly suppressed, and a metal-polyimide laminate with good dimensional accuracy can be formed.

The thickness of the support substrate may be any thickness as long as the applied resin varnish has sufficient rigidity to form a polyimide resin film. In particular, from the viewpoints of suppressing curling, dimensional stability, and suppressing wrinkles after applying the resin varnish and drying the solvent, the thickness of the support substrate is preferably 0.03 mm or more, more preferably 0.05 mm or more. The upper limit of the thickness of the support substrate is appropriately determined in consideration of the type of support substrate used and the removal method. For example, when a support substrate formed of metal foil is removed by an etching method, the thickness of the support substrate is preferably 0.5 mm or less, more preferably 0.3 mm or less. When a support substrate other than metal foil, such as a glass plate or a ceramic plate, is used, the upper limit of the thickness of the support substrate is preferably 10 mm or less, more preferably 5 mm or less.

On these support substrates, a polyimide-based resin film having a linear expansion coefficient of -5 ppm/K to 15 ppm/K is formed. The polyimide-based resin film is obtained by applying the above-mentioned resin varnish to the support substrate and curing it.

The thickness of the polyimide-based resin film can be set appropriately depending on the application and purpose of the metal-polyimide laminate. A thickness of 1 μm to 15 μm is preferable for obtaining a polyimide-based resin film with a thermal expansion coefficient of -5 ppm/K to 15 ppm/K while ensuring the necessary mechanical strength. In particular, a thickness of 2 μm to 10 μm is more preferable.

To form a polyimide-based resin film, a known method can be used as the coating method for coating the resin varnish on the supporting substrate. For example, the resin varnish can be coated on the supporting substrate by any method such as a gravure coater, knife coater, die coater, bar coater, spin coater, etc., and the solvent contained in the resin varnish is dried, and then heat-treated at a high temperature to obtain a polyimide-based resin film having excellent heat resistance. When the resin varnish is a polyamic acid varnish, which is a polyimide precursor resin, the solvent is mostly dried at a temperature of 200°C or less, and then heat-treated at a temperature of 300°C or more to perform imidization, thereby obtaining a polyimide-based resin film having excellent heat resistance.

A metal layer is formed on the surface of the polyimide resin film formed on the supporting substrate opposite the supporting substrate by plating. In this case, the plating method used may be either electroless plating or electrolytic plating, or these may be used in combination. The metal layer may be formed as a thick layer by electrolytic plating after forming a thin metal film by electroless plating, sputtering, vapor deposition, or other methods, for example. The metal layer may also be formed by a so-called semi-additive method in which a photoresist layer for plating is formed on a thin metal film formed by electroless plating, sputtering, vapor deposition, or other methods, and the resist is patterned by exposure and development, and then the layer is partially thickened by electrolytic plating. In this case, it is also possible to remove the resist layer and then remove the thin metal film by soft etching or other methods to form a metal-polyimide laminate in which the metal layer is partially formed on the polyimide resin film.

In this way, a metal layer is formed on the polyimide-based resin film by a plating method, which is a wet process. Therefore, it is preferable that the polyimide-based resin film has a small elongation percentage when immersed in a water-based chemical solution. Specifically, the elongation percentage Z calculated by the following formula from the polyimide dimension Y measured immediately after immersing in pure water for 12 hours or more and wiping off the pure water, relative to the polyimide dimension X in a dry state that does not substantially contain moisture, is preferably 0.12% or less, and more preferably 0.1% or less.
Elongation rate Z (%) = (Y-X) / X x 100
By controlling the elongation of the polyimide after immersion in pure water to 0.12% or less, peeling of the polyimide-based resin film from the supporting substrate during the plating step for forming the metal layer can be reduced.

The thickness of the metal layer in the metal-polyimide laminate can be set as desired. In particular, from the standpoint of mechanical strength, productivity, etc., the thickness of the metal layer is preferably 0.1 μm to 100 μm, and more preferably 0.5 μm to 50 μm.

The laminate on which the metal layer is formed becomes a metal-polyimide laminate by removing a part or all of the supporting substrate.
The method of removing the support substrate can be appropriately selected depending on the support substrate used. For example, the support substrate may be physically peeled off. In addition, for example, when a metal foil such as stainless steel foil or invar foil is used as the support substrate, the metal foil as the support substrate may be removed by etching with an etchant such as iron chloride or copper chloride after protecting the metal layer formed on the polyimide resin film. Furthermore, when glass is used as the support substrate, the support substrate may be removed by lift-off using a laser.

To prevent curling or wrinkling of the metal-polyimide laminate after removing the supporting substrate and to suppress dimensional changes, some parts of the metal-polyimide laminate, such as the periphery, may be reinforced with another member. Also, openings may be formed in parts of the polyimide resin film by a method such as laser or etching.

Examples will be specifically described below. Note that the following examples are provided to facilitate understanding, and the present invention is not limited to these examples.
The abbreviations used in the present examples are as follows:
m-TBHG: 2,2'-dimethyl-4,4'-diaminobiphenyl TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl TPE-M: 1,3-bis(3-aminophenoxy)benzene TPE-R: 1,3-bis(4-aminophenoxy)benzene PMDA: pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride DMAc: N,N-dimethylacetamide

<Measurement of Adhesion Strength of Metal-Polyimide Laminate>
A photosensitive dry film resist was laminated onto the metal layer of the metal-polyimide laminate, and then exposed through a specified mask. The metal layer was etched using an aqueous solution of ferric chloride. The dry film resist was then peeled off, washed with water, and dried, and the metal layer was etched into multiple patterns of 1 mm x 150 mm.

Next, the polyimide resin film surface of the etched metal-polyimide laminate was fixed to a 1 mm thick stainless steel plate using double-sided tape, and the metal layer etched to a width of 1 mm was peeled off at a 90° angle from the polyimide resin film using a tensile tester (Shimadzu Corporation Autograph AGS-H) to measure the adhesive strength.

<Measurement of thermal expansion coefficient of polyimide resin film>
The polyimide-based resin film obtained by the method described in each example was cut into a size of 3 mm x 15 mm to prepare a measurement sample. Using a thermomechanical analyzer (TMA-60 manufactured by Shimadzu Corporation), the sample was heated from room temperature to 210°C at a rate of 10°C/min while applying a load of 2.5 g, held at 210°C for 10 minutes, and then cooled at a rate of 10°C/min to determine the thermal expansion coefficient of the polyimide-based resin film from the dimensional change upon cooling from 200°C to 100°C.

<Measurement of elongation of polyimide resin film after immersion in pure water>
The polyimide resin film obtained by the method described in each example was cut into a size of about 10 mm x about 70 mm to be used as a measurement sample. The polyimide resin film was left in a desiccator controlled to a humidity of 1% or less at 23 ° C for 12 hours to obtain a dry polyimide resin film, and the length of a side of about 70 mm was accurately measured using a two-dimensional length measuring machine (Nikon MM-60), and the length of the dry polyimide resin film was determined as X mm. Next, the polyimide resin film was immersed in pure water at 23 ° C for 12 hours, and then it was taken out of the pure water and immediately wiped off the pure water using a wiping material until the pure water could no longer be visually confirmed, and the side dimension (Y mm) previously measured was measured using the two-dimensional length measuring machine, and the elongation Z (%) after immersion in pure water was calculated from the following formula.
Elongation rate Z (%) = (Y-X) / X x 100

Example 1
In a 2L separable flask equipped with a stirrer and a stirring blade, 20.168g (0.095 mol) of m-TBHG and 1.462g (0.005 mol) of TPE-M, which are diamines, were placed, and 890g of DMAc was added thereto and stirred to dissolve and disperse the diamine compound. Next, while continuing stirring in a nitrogen stream, 11.997g (0.055 mol) of PMDA and 13.240g (0.045 mol) of tetracarboxylic dianhydride were added, and further stirring was continued for 6 hours at room temperature to carry out polymerization, thereby obtaining a viscous polyamic acid solution. The concentration of polyamic acid in the polyamic acid solution was 5%, and the viscosity was 2,500 mPa·s. Using an applicator, the obtained polyamic acid varnish was applied to a glass plate having a thermal expansion coefficient of 3 ppm/K so that the thickness after curing was 5 μm, and the solvent was dried at 130° C. for 10 minutes, and then heat treatment was performed for 2 minutes at each temperature of 160° C., 200° C., 270° C., and 360° C. to obtain a polyimide film. The polyimide film was then peeled off from the glass plate to leave only the polyimide film, and its thermal expansion coefficient was measured, which was 2 ppm/K. In addition, the elongation of the polyimide film after immersing it in pure water was 0.05%.

Example 2
In a 2L separable flask equipped with a stirrer and a stirring blade, 19.106g (0.09 mol) of m-TBHG and 2.923g (0.01 mol) of TPE-M, which are diamines, were placed, and 613g of DMAc was added thereto and stirred to dissolve and disperse the diamine compound. Next, while continuing stirring in a nitrogen stream, 15.268g (0.07 mol) of PMDA and 8.827g (0.03 mol) of tetracarboxylic dianhydride were added, and stirring was continued for another 6 hours at room temperature to perform polymerization, thereby obtaining a viscous polyamic acid solution. The concentration of polyamic acid in the polyamic acid solution was 7%, and the viscosity was 5,000 mPa·s. Thereafter, the thermal expansion coefficient of the polyimide resin film having a thickness of 5 μm obtained in the same manner as in Example 1 was 1 ppm/K. In addition, the elongation rate of the polyimide film after immersing it in pure water was 0.04%.

Example 3
In a 2L separable flask equipped with a stirrer and a stirring blade, 20.168g (0.095 mol) of m-TBHG and 1.462g (0.005 mol) of TPE-R, which are diamines, were placed, and 623g of DMAc was added thereto and stirred to dissolve and disperse the diamine compound. Next, while continuing stirring in a nitrogen stream, 11.997g (0.055 mol) of PMDA and 13.240g (0.045 mol) of tetracarboxylic dianhydride were added, and stirring was continued for another 6 hours at room temperature to carry out polymerization, thereby obtaining a viscous polyamic acid solution. The concentration of polyamic acid in the polyamic acid solution was 7%, and the viscosity was 7,000 mPa·s. Thereafter, the thermal expansion coefficient of the polyimide resin film having a thickness of 5 μm obtained in the same manner as in Example 1 was 3 ppm/K. In addition, the elongation rate after immersing the polyimide film in pure water was 0.07%.

Example 4
In a 2L separable flask equipped with a stirrer and agitating blades, 21.229g (0.10 mol) of m-TBHG, which is a diamine, was placed, and 893g of DMAc was added thereto and stirred to dissolve and disperse the diamine compound. Next, while continuing stirring in a nitrogen stream, 10.906g (0.05 mol) of PMDA, 13.240g (0.045 mol) of BPDA, and 1.611g (0.005 mol) of BTDA, which are tetracarboxylic dianhydrides, were added, and stirring was continued for another 6 hours at room temperature to carry out polymerization, thereby obtaining a viscous polyamic acid solution. The concentration of polyamic acid in the polyamic acid solution was 5%, and the viscosity was 2,000 mPa·s. Thereafter, the thermal expansion coefficient of the polyimide-based resin film having a thickness of 5 μm obtained in the same manner as in Example 1 was 0 ppm/K. In addition, the elongation rate of the polyimide film after immersing it in pure water was 0.06%.

Example 5
In a 2L separable flask equipped with a stirrer and a stirring blade, 28.822g (0.09 mol) of TFMB and 2.923g (0.01 mol) of TPE-M, which are diamines, were placed, and 742g of DMAc was added thereto and stirred to dissolve and disperse the diamine compound. Next, while continuing stirring in a nitrogen stream, 15.268g (0.07 mol) of PMDA and 8.827g (0.03 mol) of tetracarboxylic dianhydride were added, and further stirring was continued for 6 hours at room temperature to perform polymerization, thereby obtaining a viscous polyamic acid solution. The concentration of polyamic acid in the polyamic acid solution was 7%, and the viscosity was 6,000 mPa·s. Thereafter, the thermal expansion coefficient of the polyimide resin film having a thickness of 5 μm obtained in the same manner as in Example 1 was 3 ppm/K. In addition, the elongation rate of the polyimide film after immersing it in pure water was 0.03%.

Example 6
A 50 μm-thick stainless steel foil (SUS430, thermal expansion coefficient 10 ppm/K) was prepared, and the polyamic acid varnish obtained in Example 1 was applied thereon using an applicator. The solvent was dried at 130° C. for 30 minutes, and then heat treatment was performed at temperatures of 160° C., 200° C., 270° C., and 360° C. to form a 5 μm-thick polyimide-based resin film on the stainless steel foil.

Next, a thin copper layer of approximately 200 nm was formed by sputtering on the polyimide resin film formed on the stainless steel foil, and a copper layer of 10 μm was then formed by electrolytic plating. The copper layer formed by electrolytic plating was then protected with a dry film resist, and the stainless steel foil was etched away with an aqueous ferric chloride solution to obtain a metal-polyimide laminate in which the metal layer was a copper layer. The obtained metal-polyimide laminate was generally flat, and the adhesive strength of the metal (copper) was 0.6 kN/m.

(Example 7)
A metal-polyimide laminate was obtained in the same manner as in Example 6, except that the polyamic acid varnish obtained in Example 2 was used instead of the polyamic acid varnish obtained in Example 1, in which a copper layer having a thickness of 10 μm was formed on a polyimide-based resin film having a thickness of 5 μm. The obtained metal-polyimide laminate was generally flat, and the adhesive strength of the metal (copper) was 0.5 kN/m.

(Example 8)
A metal-polyimide laminate having a copper layer of 10 μm thickness formed on a polyimide resin film of 5 μm thickness was obtained in the same manner as in Example 6, except that the polyamic acid varnish obtained in Example 3 was used instead of the polyamic acid varnish obtained in Example 1. The obtained metal-polyimide laminate was generally flat, and the adhesive strength of the metal (copper) was 0.5 kN/m.

Example 9
A metal-polyimide laminate having a copper layer of 10 μm thickness formed on a polyimide resin film of 5 μm thickness was obtained in the same manner as in Example 6, except that the polyamic acid varnish obtained in Example 4 was used instead of the polyamic acid varnish obtained in Example 1. The obtained metal-polyimide laminate was generally flat, and the adhesive strength of the metal (copper) was 0.5 kN/m.

Example 10
A metal-polyimide laminate having a copper layer of 10 μm thickness formed on a polyimide resin film of 5 μm thickness was obtained in the same manner as in Example 6, except that the polyamic acid varnish obtained in Example 5 was used instead of the polyamic acid varnish obtained in Example 1. The obtained metal-polyimide laminate was generally flat, and the adhesive strength of the metal (copper) was 0.5 kN/m.

(Example 11)
A 50 μm-thick stainless steel foil (SUS430) was prepared, and the polyamic acid varnish obtained in Example 1 was applied thereon using an applicator. The solvent was dried at 130° C. for 30 minutes, and then heat treatment was performed at temperatures of 160° C., 200° C., 270° C., and 360° C. to form a 5 μm-thick polyimide-based resin film on the stainless steel foil.

Next, an alloy layer of 80% nickel and 20% chromium and a copper layer were formed in that order on the polyimide resin film by sputtering to thicknesses of approximately 10 nm and approximately 200 nm, respectively, to form a thin metal film layer. After that, a resist for plating was formed in a lattice shape on the thin metal film layer formed by sputtering, and a lattice-like copper layer pattern with a thickness of 5 μm was formed by electrolytic plating. The resist for plating was then peeled off and removed, and the thin metal film layer that was only sputtered and did not have electrolytically plated copper was removed using a soft etching solution.

Next, the remaining copper layer was protected with a dry film resist, and the stainless steel foil was etched away with an aqueous solution of ferric chloride to obtain a metal-polyimide laminate with a metal layer patterned in a grid pattern.

Example 12
A glass plate having a thickness of 1 mm was prepared as a supporting substrate, and the polyamic acid varnish obtained in Example 1 was applied thereon using an applicator, dried at 130° C. for 30 minutes, and then heat-treated at temperatures of 160° C., 200° C., 270° C., and 360° C. for 2 minutes each to form a polyimide-based resin film having a thickness of 5 μm on the glass plate.

Next, a nickel thin film layer with a thickness of about 200 nm was formed on the polyimide resin film by electroless plating, a plating resist was formed on top of it so as to have a lattice shape, and further, the nickel layer was thickened by electrolytic plating so as to have a thickness of 10 μm. Thereafter, the plating resist was peeled off and removed, and the nickel thin film layer formed only by electroless plating was etched off using a soft etching solution, to obtain a metal-polyimide laminate in which the nickel layer was formed in a lattice shape.
Next, the glass plate was removed from the polyimide resin film by lift-off using a laser beam, to obtain the desired metal-polyimide laminate.

(Comparative Example 1)
In a 1L separable flask equipped with a stirrer and a stirring blade, 10.615g (0.05 mol) of m-TBHG and 14.617g (0.05 mol) of TPE-M, which are diamine compounds, were placed, and 671g of DMAc was added thereto and stirred to dissolve and disperse the diamine compounds. Next, while continuing stirring in a nitrogen stream, 11.997g (0.055 mol) of PMDA, which is a tetracarboxylic dianhydride, and 13.240g (0.045 mol) of BPDA were added, and further stirring was continued at room temperature for 6 hours to carry out polymerization, thereby obtaining a viscous polyamic acid solution.

The thermal expansion coefficient of the polyimide resin film having a thickness of 5 μm obtained in the same manner as in Example 1 was 30 ppm/K. In addition, the elongation percentage of the polyimide film after immersing it in pure water was 0.14%.
Thereafter, the same treatment as in Example 6 was carried out to obtain a metal-polyimide laminate in which a copper layer having a thickness of 10 μm was formed on a polyimide-based resin film having a thickness of 5 μm. However, the obtained metal-polyimide laminate had severe warping and wrinkling and was not suitable for practical use.

Claims (3)

a polyimide-based resin film formed by curing a polyimide-based varnish containing a polyimide-based resin and having a thermal expansion coefficient of −2 ppm/K to 5 ppm/K;
a metal layer formed by plating on the polyimide-based resin film;
Equipped with
The polyimide-based resin film is synthesized from a diamine and a tetracarboxylic dianhydride,
The diamine is formed of a polyimide resin varnish containing 80 mol % or more of 2,2'-dimethyl-4,4'-diaminobiphenyl or 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl,
The polyimide resin film has a dimension in a dry state of X and a dimension measured after immersion in pure water for 12 hours or more of Y, and the polyimide resin film has an elongation percentage Z (%) calculated by Z = (Y - X) / X x 100, Z ≦ 0.1%. The metal-polyimide laminate according to claim 1, wherein the polyimide resin film has a thickness of 1 μm to 15 μm. The metal-polyimide laminate according to claim 1 or 2, wherein the metal layer contains copper or nickel.