JP2007245525A - Flexible laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently prevent a polyimide resin layer from adhering to another polyimide resin layer or the polyimide resin layer from adhering to a covering material, in a process to fabricate a flexible laminate into a multi-layer flexible printing substrate, while maintaining mechanical characteristics such as tensile strength, ductility and elastic modulus of the laminated polyimide resin layers. <P>SOLUTION: This flexible laminate comprises metallic foil and a plurality of the polyimide resin layers laminated on the metallic foil. A top layer positioned on the opposite side to the metallic foil among the polyimide resin layers, is the polyimide resin layer which contains 17 to 40 mass parts inorganic filler with 0.1 to 3 μm average particle diameter for 100 mass parts resin component and has 0.5 t 10 μm thickness. In addition, the thickness of the top layer falls within the range of 3 to 15% of the overall thickness of a plurality of the polyimide resin layers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible laminate, and more particularly to a flexible laminate in which a polyimide resin layer is laminated on a metal foil.

  Conventionally, polyimide films are widely used for flexible printed circuit boards as laminates with metal foils or metal thin films because they are excellent in heat resistance, chemical resistance, mechanical strength, electrical properties and the like.

  However, since the polyimide film is generally formed by the solution casting method, the surface is very smooth. Therefore, the film surface is not slippery and is wound around the roll or has wrinkles. Therefore, the slipperiness of the surface of the polyimide film, that is, the slipperiness, is one of the important required performances.

  For this reason, as a method for imparting easy lubricity to the surface of the polyimide film, a method of performing a surface treatment such as sandblasting is known. However, in this method, blast particles or film fragments due to blast adhere to the surface of the polyimide film, so that when the adhesive is applied in the previous process for forming a flexible laminate, entrapment of bubbles and repelling occur. There was a problem that the yield decreased.

  Japanese Patent Application Laid-Open Nos. 62-68852 and 2002-256085 disclose a method for imparting slipperiness by allowing inorganic particles to be present in a polyimide film to form fine protrusions on the film surface. It is disclosed. However, these methods have a problem that the polyimide film becomes brittle and mechanical properties such as tensile strength, elongation, and elastic modulus of the polyimide resin layer in the obtained flexible laminate are deteriorated.

Furthermore, with the recent increase in functionality of portable electronic devices, the number of flexible printed circuit boards has been increasing. However, when a flexible laminate using a conventional slippery polyimide film is used, a multilayer flexible printed circuit board can be used. The problem that adhesion between polyimide resin layers or between the polyimide resin layer and the cover material occurs in the processing step and the yield is lowered has also become a new important issue.
JP-A-62-68852 JP 2002-256085 A

  The present invention has been made in view of the above-described problems of the prior art, and maintains a high level of mechanical properties such as tensile strength, elongation, and elastic modulus of the laminated polyimide resin layer while maintaining a high level of flexibility. It is an object of the present invention to provide a flexible laminate that can sufficiently prevent occurrence of adhesion between polyimide resin layers or between a polyimide resin layer and a cover material in a process of processing into a printed board.

  As a result of intensive research to achieve the above object, the present inventors have made a polyimide resin layer, which is an insulating layer, a multilayer structure, and is located on the opposite side of the metal foil among the plurality of polyimide resin layers. It has been found that the above object can be achieved by making the polyimide resin layer of the top layer a polyimide resin layer having a predetermined thickness containing a predetermined amount of inorganic filler, and has completed the present invention.

  That is, the flexible laminate of the present invention is a flexible laminate comprising a metal foil and a plurality of polyimide resin layers laminated on the metal foil, and the metal among the plurality of polyimide resin layers. A thickness of 0.5 to 10 μm, in which the top layer located on the opposite side of the foil contains an inorganic filler having an average particle diameter of 0.1 to 3 μm of 17 to 40 parts by weight with respect to 100 parts by weight of the resin component And the thickness of the top layer is in the range of 3 to 15% of the total thickness of the plurality of polyimide resin layers.

  In the flexible laminate of the present invention, the inorganic filler is preferably spherical silica.

  According to the present invention, polyimide resin layers or polyimides are processed in a process of processing into a multilayer flexible printed circuit board while maintaining mechanical properties such as tensile strength, elongation, and elastic modulus of the laminated polyimide resin layers at a high level. It is possible to provide a flexible laminate that can sufficiently prevent the occurrence of adhesion between the resin layer and the cover material.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  The flexible laminate of the present invention is a flexible laminate comprising a metal foil and a plurality of polyimide resin layers laminated on the metal foil, wherein the metal foil is the metal foil of the plurality of polyimide resin layers. On the other hand, the top layer located on the opposite side has a thickness of 0.5 to 10 μm containing an inorganic filler having an average particle diameter of 0.1 to 3 μm of 17 to 40 parts by weight with respect to 100 parts by weight of the resin component. And the top layer has a thickness in the range of 3 to 15% of the total thickness of the plurality of polyimide resin layers.

  The metal foil used by this invention should just function as a conductive layer in a flexible laminated board, and is not specifically limited. Examples of such metal foils include foils or thin films made of conductive metals such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zinc, and alloys thereof. Copper foil is preferred. In addition, as such copper foil, although rolled copper foil and electrolytic copper foil exist, either may be used. The alloy copper foil is an alloy foil containing copper as an essential element and containing at least one kind of different elements other than copper such as chromium, zirconium, nickel, silicon, zinc, beryllium, etc. Is preferably 90% by mass or more, more preferably 95% by mass or more.

  The thickness of the metal foil according to the present invention is not particularly limited, but a thinner one is desirable for finer circuit pitch, and generally a thickness of about 5 to 150 μm is preferably employed. Furthermore, for the purpose of improving the adhesive strength with the resin on the metal foil surface, chemical or physical using siding, nickel plating, copper-zinc alloy plating, aluminum alcoholate, aluminum chelate, silane coupling agent, etc. A surface treatment may be applied to the surface of the metal foil.

  The polyimide resin layer used in the present invention functions as an insulating layer of a flexible laminate, and as such a polyimide resin, an aromatic tetracarboxylic acid component and an aromatic diamine component which are resin components are polymerized. Further, a heat-resistant high molecular weight polymer obtained by imidization is preferably employed.

  Examples of the aromatic tetracarboxylic acid component include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, and 3,3 ′. , 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, and the like. As such an aromatic tetracarboxylic acid component, only 1 type may be used or it may be used in combination of 2 or more type.

  Examples of the aromatic diamine component include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and 3,3′-dimethyl. Examples include -4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis (3methyl-5aminophenyl) benzene and the like. As such an aromatic diamine component, only 1 type may be used or it may be used in combination of 2 or more type.

  The method for synthesizing the polyimide resin according to the present invention is not particularly limited, and a known method can be appropriately employed. For example, in the solvent, the aromatic tetracarboxylic acid component anhydride and the aromatic diamine component are mixed at an approximately equimolar ratio, and the reaction temperature is in the range of 0 to 200 ° C. (preferably in the range of 0 to 100 ° C.). A method of obtaining a polyimide resin by obtaining a polyamic acid which is a precursor of a polyimide resin by polymerization reaction and then further imidizing by a heat treatment or the like.

  The solvent used in the production of such a polyimide resin precursor is not particularly limited, and an organic polar solvent capable of uniformly dissolving the resin component is suitably employed. Examples of such organic polar solvents include amide solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, and such solvents include only one kind. It may be used or two or more types may be used in combination. Furthermore, an aromatic hydrocarbon solvent such as benzene and toluene or an aliphatic hydrocarbon solvent such as hexane and decane may be appropriately mixed and used in the solvent as necessary.

  In the flexible laminate of the present invention, a plurality of resin layers made of the polyimide resin are laminated on one side of the metal foil. Such a plurality of polyimide resin layers are formed by laminating a plurality of polyimide resin layers composed of mutually different components, but non-adjacent polyimide resin layers may be composed of the same components. .

  And in the flexible laminated board of this invention, the top layer located in the outermost layer on the opposite side with respect to the said metal foil among the said several polyimide resin layers is 17-40 mass with respect to 100 mass parts of resin components. It is necessary to be a polyimide resin layer having a thickness of 0.5 to 10 μm containing an inorganic filler having an average particle diameter of 0.1 to 3 μm.

  The inorganic filler used in the present invention is not particularly limited as long as it is chemically inert, and includes silica, titanium oxide, calcium carbonate, calcium hydrogen phosphate, etc. Among them, the bulk specific gravity is small, Spherical silica is particularly preferable from the viewpoint of suppressing an increase in the viscosity of the resin and enabling high filling.

  The average particle size of the inorganic filler according to the present invention is required to be 0.1 to 3 μm, and more preferably 1 to 3 μm. If the average particle size of the inorganic filler is less than 0.1 μm, the effect of preventing adhesion due to the addition of the inorganic filler is not sufficiently achieved. On the other hand, if the average particle size exceeds 3 μm, the external appearance of the film tends to be adversely affected.

  In the flexible laminated board of this invention, it is required that content of the said inorganic filler is 17-40 mass parts with respect to 100 mass parts of resin components which comprise the said top layer, and is 20-30 mass parts. More preferably. When the content of the inorganic filler is less than 17 parts by mass, the effect of preventing adhesion due to the addition of the inorganic filler is not sufficiently achieved. On the other hand, when the content exceeds 40 parts by mass, the tensile strength, elongation, elastic modulus, and the like of the polyimide resin layer obtained. Not only will the mechanical properties of the product deteriorate, but also when producing flexible laminates from the raw polyimide resin solution, clogging of the filter provided to prevent filler aggregation in the production process will occur, reducing productivity. It is not preferable.

  Moreover, in the flexible laminated board of this invention, it is necessary to make the thickness of the said top layer into 0.5-10 micrometers, and it is more preferable to set it as 1-4 micrometers. When the thickness of the top layer is less than 0.5 μm, it is difficult to uniformly form a top layer containing an inorganic filler. On the other hand, when the thickness exceeds 10 μm, circuit processing is performed using a flexible laminate obtained. For example, when the metal foil is removed, excessive curling occurs and the resin film is rounded.

  Furthermore, in the flexible laminate of the present invention, it is necessary that the ratio of the thickness of the top layer to the total thickness of the plurality of polyimide resin layers is in the range of 3 to 15%, More preferably, it is within the range of 3 to 13%. When the thickness ratio of the top layer is less than 3%, it is difficult to uniformly form a top layer containing an inorganic filler. On the other hand, when the thickness ratio exceeds 15%, the tensile strength, elongation, and elasticity of the resulting polyimide resin layer are difficult. The mechanical characteristics such as the rate are lowered, and curling is likely to occur when the metal foil is removed in the process of circuit processing using the obtained flexible laminate.

  In the flexible laminate of the present invention, the polyimide resin layer other than the top layer in the plurality of polyimide resin layers is a polyimide resin layer that does not contain the inorganic filler. There may be. The total thickness of the plurality of polyimide resin layers in the flexible laminate of the present invention is preferably 10 to 50 μm, and more preferably 15 to 40 μm. If the total thickness of the polyimide resin layers of the plurality of layers is less than the lower limit, the handleability as a flexible laminate tends to deteriorate. On the other hand, if the upper limit is exceeded, the characteristics of the flexible laminate used for small products are utilized. There is a tendency not to be.

As such a plurality of polyimide resin layers, the top layer, a bottom layer located on the innermost layer in contact with the metal foil, a base layer located between the top layer and the bottom layer, The thing provided with is preferable. The polyimide resin layers constituting the base layer and the bottom layer are not particularly limited, but from the viewpoint of suppressing warpage and curling, the top layer linear expansion coefficient (Tp) and the base layer linear expansion coefficient (Bs). And the linear expansion coefficient (Bm) of the bottom layer are as follows:
Bm>Tp> Bs
It is preferable to satisfy | fill. Moreover, the thickness of the polyimide resin layer constituting the base layer and the polyimide resin layer constituting the bottom layer is not particularly limited, but generally the former is preferably about 5 to 30 μm and the latter is preferably about 1 to 4 μm.

  Next, the suitable method for manufacturing the flexible laminated board of this invention is demonstrated. As a manufacturing method of the flexible laminated board of this invention, there exist the following two methods, for example. That is, the first method is a so-called coating method in which a plurality of polyimide resin layers are formed on a metal foil by applying a plurality of polyimide resin precursor resin solutions or polyimide resin solutions. The second method is a so-called laminating method in which a plurality of polyimide resin films prepared in advance are laminated on a metal foil. In any method, it is necessary that the above-mentioned inorganic filler is contained in the polyimide resin layer constituting the top layer.

  Hereinafter, the suitable method of manufacturing the flexible laminated board of this invention using a coating method is demonstrated. That is, first, a polyimide resin precursor resin solution or a polyimide resin solution is obtained. The polyimide resin precursor resin refers to a resin having a molecular structure that is a precursor for producing a polyimide resin, and imidized by heating or the like to become a polyimide resin. Examples of such a polyimide resin precursor resin include polyamic acid. Further, it is necessary to contain a predetermined amount of the inorganic filler in the polyimide resin precursor resin solution or the polyimide resin solution for forming the top layer. For example, the former solution is obtained as follows. be able to.

  That is, first, an inorganic filler is added to an organic polar solvent at a predetermined ratio, and dispersed using an ultrasonic wave or the like while stirring with a stirring blade or the like to prepare a dispersion called a premix. Next, the resulting premix was added to an organic polar solvent in which an aromatic diamine component was dissolved, and further, an aromatic tetracarboxylic acid component anhydride was added thereto and stirred to contain an inorganic filler. A polyamic acid solution can be obtained.

Next, a plurality of resin layers are formed on the surface of the metal foil by repeating operations of sequentially applying and drying a plurality of polyimide resin precursor resin solutions or polyimide resin solutions. In addition, application | coating of such a solution can be performed using a knife coater, a die coater, a roll coater, a curtain coater, etc. Such a plurality of resin layers may be collectively formed on the surface of the metal foil using a multilayer die or the like. Furthermore, the viscosity of such a solution is not particularly limited, but it is generally preferable that the viscosity be in the range of about 500 to 35000 cps (× 10 ⁻³ Pa · s).

  When a polyimide resin solution is used, the plurality of resin layers obtained in this way become a plurality of polyimide resin layers. On the other hand, when a solution of a polyimide resin precursor resin is used, the plurality of resin layers thus obtained are preferably subjected to heat treatment at 200 ° C. or higher, more preferably 300 ° C. or higher to imidize. Thus, a plurality of polyimide resin layers are formed.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. The presence / absence of adhesion, the thermal expansion coefficient, the curl size of the flexible laminate and the etching film, tear propagation resistance, tensile strength, elongation, and elastic modulus were evaluated or measured by the following methods, respectively.

<Evaluation of adhesion>
In the case of evaluating adhesion between polyimide resin layers, two flexible laminates are laminated so that their polyimide resin surfaces face each other and pressed (press pressure: 3.1 MPa), and interlayer adhesion of the obtained laminate is performed. The strength was measured. On the other hand, in the case of evaluating adhesion between a polyimide resin layer and a cover material, two flexible laminates laminated with a cover material (a polyimide film having a thickness of 25 μm) are laminated so that the cover materials face each other and pressed ( Press pressure: 3.1 MPa), and the interlayer adhesion strength of the obtained laminate was measured. In addition, the measurement in normal temperature (23 degreeC) and the state in the state which performed the humidification process (85 degreeC, 85RH%, 72hr) as pre-processing were performed.

  Here, when there is no adhesion so that the interlaminar adhesive strength is below the lower limit of the measuring instrument, ◎ when weak adhesion of less than 5 N / m is observed, ○ when obvious adhesion of 5 N / m or more is recognized Was evaluated as x.

<Measurement of thermal expansion coefficient>
The resin film from which the metal foil has been removed by etching the flexible laminate is cooled to 250 ° C. and then cooled at a rate of 10 ° C./min, and 240 ° C. using a thermomechanical analyzer (TMA100) manufactured by Seiko Denshi Kogyo Co., Ltd. It calculated | required by calculating the average linear expansion coefficient between -100 degreeC.

<Measurement of curl size of flexible laminate and etching film>
The curl size of the flexible laminate is measured by the radius of curvature of the flexible laminate (dimension: 50mm x 50mm) obtained by imidizing the precursor resin layer of polyimide resin formed on the metal foil. did. The curl size of the etching film was measured by measuring the radius of curvature of a resin film (size: 50 mm × 50 mm) from which the flexible foil was etched to remove the metal foil.

<Measurement of tear propagation resistance>
A cut (length: 12.7 mm) is made in the longitudinal direction of the resin film (size: 63.5 mm × 50 mm) from which the metal foil has been removed by etching the flexible laminate, and manufactured by Toyo Seiki Seisakusho Co., Ltd. Both ends of the cut were torn with a constant load using a light load tear tester, and the resistance value was measured.

<Measurement of tensile strength>
Using a universal testing machine (STROGRAPH-R1) manufactured by Toyo Seiki Seisakusho Co., Ltd., the tensile strength of the resin film from which the metal foil was removed by etching the flexible laminate was measured in an environment of 23 ° C. and 50% RH. .

<Measurement of elongation>
Using a universal testing machine (STROGRAPH-R1) manufactured by Toyo Seiki Seisakusho Co., Ltd., the elongation of the resin film from which the metal foil was removed by etching the flexible laminate was measured in an environment of 23 ° C. and 50% RH. .

<Measurement of elastic modulus>
Using a universal testing machine (STROGRAPH-R1) manufactured by Toyo Seiki Seisakusho Co., Ltd., the elastic modulus of the resin film obtained by removing the metal foil by etching the flexible laminate was measured in an environment of 23 ° C. and 50% RH. .

Moreover, the symbol of the compound used by the Example and the comparative example is shown below. Further, spherical silica having an average particle size of 1.1 μm manufactured by Admatex was used. Furthermore, F2-WS (thickness: 12 μm) manufactured by Furukawa Circuit Foil Co., Ltd. was used as the copper foil.
BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane DADMB: 4,4′-diamino-2,2′-dimethylbiphenyl DAPE: 4,4′-diamino-diphenyl ether PMDA: pyromellitic acid Dianhydride BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride BTDA: 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride DMAc: N, N-dimethylacetamide.

[Synthesis Example 1]
15.9 g of spherical silica was added to 83.1 g of dry DMAc, and the temperature was kept at 25 ° C. while stirring at 200 rpm with a stirring blade, and ultrasonic dispersion was performed for 3 hours to prepare a premix. Next, 11.59 g of DAPE (0.058 mol) was dissolved in 234.64 g of DMAc while stirring in a container, and 41.81 g of premix and 18.62 g of BTDA (0.058 mol) were then added. added. Thereafter, the stirring was continued for 3 hours to advance the polymerization reaction, thereby obtaining a polyamic acid resin solution a having an inorganic filler content of 22 phr, a polymer concentration of 10% by mass, and a solution viscosity of 18.5 poise.

[Synthesis Example 2]
12.5 g of spherical silica was added to 87.5 g of dried DMAc, and the temperature was kept at 25 ° C. while stirring with a stirring blade at 200 rpm, and ultrasonic dispersion was performed for 3 hours to prepare a premix. Next, 11.59 g of DAPE (0.058 mol) was dissolved in 234.64 g of DMAc while stirring in a container, and then 40.2 g of premix and 18.62 g of BTDA (0.058 mol) were added. added. Thereafter, the stirring was continued for 3 hours to advance the polymerization reaction, thereby obtaining a polyamic acid resin solution b having an inorganic filler content of 17 phr, a polymer concentration of 10% by mass, and a solution viscosity of 17.8 poise.

[Synthesis Example 3]
In 97.0 g of dry DMAc, 3.0 g of spherical silica was added, and the temperature was kept at 25 ° C. while stirring with a stirring blade at 200 rpm, and ultrasonic dispersion was performed for 3 hours to prepare a premix. Next, 17.37 g of DAPE (0.086 mol) was dissolved in 234.64 g of DMAc in a container with stirring, and then 36.25 g of premix and 27.62 g of BTDA (0.086 mol) were added. added. Thereafter, the stirring was continued for 3 hours to advance the polymerization reaction, thereby obtaining a polyamic acid resin solution c having an inorganic filler content of 3.6 phr, a polymer concentration of 10% by mass, and a solution viscosity of 15.6 poise.

[Synthesis Example 4]
In 255 g dry DMAc, 19.11 g DADMB (0.090 mol) and 2.92 g 1,3-BAB (0.010 mol) were dissolved in a vessel with stirring. Next, 5.79 g BPDA (0.020 mol) and 17.17 g PMDA (0.079 mol) were added. Thereafter, stirring was continued for 3 hours to advance the polymerization reaction, and a polyamic acid resin solution d having a polymer concentration of 15% by mass and a solution viscosity of 200 poise was obtained.

[Synthesis Example 5]
In 255 g dry DMAc, 28.9 g BAPP (0.070 mol) was dissolved in a vessel with stirring. Next, 1.07 g BPDA (0.004 mol) and 15.03 g PMDA (0.069 mol) were added. Thereafter, stirring was continued for 3 hours to advance the polymerization reaction, and a polyamic acid resin solution e having a polymer concentration of 15% by mass and a solution viscosity of 50 poise was obtained.

[Example 1]
On the copper foil, the polyamic acid resin solution e obtained in Synthesis Example 5 as a resin constituting the bottom layer was uniformly applied with a thickness of 15 μm, and then dried by heating at 130 ° C. to remove the solvent. Next, on the copper foil, the polyamic acid resin solution d obtained in Synthesis Example 4 as a resin constituting the base layer was uniformly applied with a thickness of 150 μm, and then dried by heating at 130 ° C. to remove the solvent. . Next, the polyamic acid resin solution a obtained in Synthesis Example 1 as a resin constituting the top layer was uniformly applied with a thickness of 30 μm on the copper foil, and then the solvent was removed by heating and drying at 130 ° C. . Thereafter, the obtained copper foil having a plurality of resin layers was heated (heat treatment) from 160 ° C. to 360 ° C. at a rate of temperature increase of about 15 ° C./min to advance the imidization reaction, and the three polyimide resin layers were copper. A flexible laminate formed on the foil was obtained. In the obtained flexible laminate, the thickness of the three polyimide resin layers was 20 μm, and the thickness of the top layer was 2.3 μm.

  When the adhesion was evaluated using the obtained flexible laminate, both the polyimide resin layers and between the polyimide resin layer and the cover material were subjected to interlayer adhesion strength in both room temperature and humidified states. Was below the lower limit of the measuring instrument, confirming that there was no adhesion. Table 1 shows the results of measuring the thermal expansion coefficient, the curl size, the tear propagation resistance, the tensile strength, the elongation, and the elastic modulus by the above-described method using the obtained flexible laminate.

[Example 2]
A flexible laminate in which three polyimide resin layers are formed on a copper foil in the same manner as in Example 1 except that the polyamic acid resin solution b obtained in Synthesis Example 2 is used as the resin constituting the top layer. Obtained.

  When the adhesion was evaluated using the obtained flexible laminate, it was about 2 N / m in a humidified state between the polyimide resin layers, and normal temperature and humidified between the polyimide resin layer and the cover material. Interlayer adhesion strength of about 2 N / m was measured in both states, but it was confirmed that adhesion was weak. Table 1 shows the results of measuring the thermal expansion coefficient, the curl size, the tear propagation resistance, the tensile strength, the elongation, and the elastic modulus by the above-described method using the obtained flexible laminate.

[Comparative Example 1]
A flexible laminate in which three polyimide resin layers are formed on a copper foil in the same manner as in Example 1 except that the polyamic acid resin solution c obtained in Synthesis Example 3 was used as the resin constituting the top layer. Obtained.

  When the adhesion was evaluated using the obtained flexible laminate, the polyimide resin layers and the polyimide resin layer and the cover material were both 5 to 7 N both at room temperature and in a humidified state. Interlaminar adhesion strength of about / m was measured, and it was confirmed that clear adhesion occurred. Table 1 shows the results of measuring the thermal expansion coefficient, the curl size, the tear propagation resistance, the tensile strength, the elongation, and the elastic modulus by the above-described method using the obtained flexible laminate.

[Comparative Example 2]
A flexible laminate having three polyimide resin layers formed on a copper foil was obtained in the same manner as in Example 2 except that the thickness of the cured top layer was 3.3 μm.

  When the adhesion was evaluated using the obtained flexible laminate, it was about 2 N / m in a humidified state between the polyimide resin layers, and normal temperature and humidified between the polyimide resin layer and the cover material. Interlayer adhesion strength of about 2 N / m was measured in both states, but it was confirmed that adhesion was weak. Table 1 shows the results of measuring the thermal expansion coefficient, the curl size, the tear propagation resistance, the tensile strength, the elongation, and the elastic modulus by the above-described method using the obtained flexible laminate.

  As is apparent from the results shown in Table 1, when the flexible laminate of the present invention is used (Examples 1 and 2), the mechanical properties such as the tensile strength, elongation, and elastic modulus of the laminated polyimide resin layer It was confirmed that the mechanical properties were maintained at a high level, and the occurrence of adhesion between the polyimide resin layers and the polyimide resin layer and the cover material at room temperature and in a humidified state was sufficiently prevented.

  In the flexible laminate of the present invention, when the ratio of the thickness of the top layer to the total thickness of the multiple polyimide resin layers is within a range of 15% or less (Examples 1 and 2), the flexible laminate It was confirmed that the curling of the plate and the etching film from which the metal foil was removed was reliably prevented.

  As described above, according to the present invention, in the process of processing into a multilayer flexible printed circuit board while maintaining mechanical properties such as tensile strength, elongation, and elastic modulus of the laminated polyimide resin layer at a high level. It is possible to provide a flexible laminate that can sufficiently prevent occurrence of adhesion between polyimide resin layers or between a polyimide resin layer and a cover material.

Therefore, the present invention is very useful as a technique for sufficiently preventing the yield reduction when manufacturing a multilayer flexible printed circuit board using a flexible laminate and improving the productivity of the multilayer flexible printed circuit board. is there.

Claims (2)

  A flexible laminate comprising a metal foil and a plurality of polyimide resin layers laminated on the metal foil, the top being located on the opposite side of the metal foil of the plurality of polyimide resin layers The layer is a polyimide resin layer having a thickness of 0.5 to 10 μm containing an inorganic filler having an average particle diameter of 0.1 to 3 μm of 17 to 40 parts by weight with respect to 100 parts by weight of the resin component; The flexible laminate has a thickness of the top layer in the range of 3 to 15% of the total thickness of the plurality of polyimide resin layers.   The flexible laminate according to claim 1, wherein the inorganic filler is spherical silica.