JP2729063B2 - Method of manufacturing flexible metal foil laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flexible metal foil laminate (Flexible Metal Clad Laminat) which is becoming widespread in the electronics industry.
e, hereafter also abbreviated as FMCL), and particularly relates to an FMCL having excellent durability such as heat resistance and moisture resistance.

[Related Art] FMCL is mainly used as a base material for a flexible printed wiring board, but is also used as a surface heating element, a material for electromagnetic wave shielding, a flat cable, a packaging material, and the like.

In recent years, the use of FMCL as a base material for printed wiring boards has been increasing due to cases such as cases where printed wiring boards are housed being made compact.

Conventionally, such FMCLs are conventionally manufactured by laminating a heat-resistant polymer film to a copper foil using an adhesive composed of an organic polymer having a thickness of 5 μm or more. However, FMCLs using this adhesive do not fully utilize the excellent properties of the heat-resistant polymer film due to insufficient properties of the adhesive, and have a problem particularly in terms of heat resistance.

For this purpose, a method in which a heat-resistant polymer film and a metal foil are directly fixed without using an adhesive to form an FMCL has been conventionally studied. For example, U.S. Pat.
9,634, 3,736,170, JP-A-49-129,862, JP-A-58-190,0
91 and 59-162,044.

However, adhesive free FM by these methods
CL has insufficient adhesive strength between the heat-resistant polymer film and the metal foil, or its strength is not stable even if the adhesive strength is sufficient. Had various disadvantages.

Particularly, in the case of polyimide and polyamideimide among the heat-resistant polymers, it is difficult to stably obtain a large adhesive force due to various causes.

Further, as described in the examples of U.S. Patent 3,736,170 and JP-A-59-162,044, in the case of polyimide insoluble in a phenolic solvent suitable as a heat-resistant polymer for FCL, a heat-resistant polymer film The peel strength between copper foil and copper foil is 0.30 to 0.60 kg / cm.If the bending stress is large or the circuit width is narrow, it is considered that the adhesive strength is sufficient considering the reliability of the circuit. I can not say.

In addition, the FMCL often covers the circuit surface with a cover material to protect the circuit after the circuit is formed, but FMCL, which has excellent adhesion between the cover material and the base film layer, is still in practical use. Not reached.

In addition, important characteristics of the FMCL are that the heat-resistant polymer film does not deform in the solder bath, or that the soldering iron (≧ 250 ° C) is less deformed when it directly touches the heat-resistant polymer film. Although high-temperature film properties are required, if a configuration is made with emphasis on the adhesion between the heat-resistant polymer and the metal foil, the film properties at high temperatures of the heat-resistant polymer often have a glass transition, for example. It is not sufficient, such as low temperature and high thermoplasticity. That is, a material satisfying all of the adhesiveness to the metal foil, the film characteristics at high temperature, the adhesiveness to the cover material, and other physical and chemical film characteristics as FMCL has not been obtained.

[Problems to be Solved by the Invention] FMCL in which a polyimide film is bonded to a copper foil via an adhesive layer made of an organic polymer such as an epoxy resin or an acrylic resin having a thickness of about 5 μm or more has already been proposed. Existing FMCLs using an adhesive made of such an organic polymer have not reached the required levels in many points, such as adhesive strength when heated and heat resistance such as heat deterioration resistance.

On the other hand, a conventional FMCL without an adhesive layer is superior to an FMCL with an adhesive layer in terms of heat resistance, but has reached the required level in terms of adhesive strength and properties of a heat-resistant polymer film. In many cases, the adhesive strength between the heat-resistant polymer film and the cover material is poor.

In view of this situation, the present invention allows the heat-resistant polymer film to be firmly and stably adhered to the metal foil while maintaining the situation where the excellent properties of the heat-resistant polymer film are utilized, and the durability of the adhesive force. It is an object of the present invention to provide an excellent FMCL, and such an FMCL is extremely useful in industry, particularly in the electronics industry.

[Means for Solving the Problems] That is, the present invention relates to a method for producing an adhesive polyimide film layer having a glass transition temperature of 170 ° C. or higher and a glass transition temperature of 300 ° C. or higher, which is directly in contact with a metal foil. The thickness ratio of the following polyimide film layer is 0.001 or more, 0.2 or less, and, after sequentially applying polyimide or a precursor thereof dissolved in a solvent on a metal foil, heating to form two or more film layers. A method for producing a flexible metal foil laminate, characterized in that the method further comprises: forming, in the method described above, a residual solvent concentration of 30% after applying an adhesive polyimide or a precursor thereof dissolved in a solvent on the metal foil. Heat and dry until the following, then apply a polyimide or a precursor thereof having a composition different from that of the adhesive polyimide or a precursor thereof, and then heat dry to reduce the amount of A method for manufacturing a flexible metal foil laminate, comprising a step of forming at least two polyimide film layers.

Specifically, the gist of the present invention is that a heat-resistant polymer or a precursor thereof has a large adhesive force with the metal foil on the surface of the metal foil and a large adhesive force with a heat-resistant polymer or a precursor thereof to be formed later. After the body solution is applied, it is heated and dried, first, a first layer made of a heat-resistant polymer or a precursor thereof is provided, and then a glass transition temperature higher than that of the heat-resistant polymer is formed on the layer. A solution of a heat-resistant polymer or a precursor thereof is applied and heated and dried to form a second layer, thereby forming two or more different heat-resistant polymers. FM in which a polymer film is formed and the aforementioned problems are solved
It is now possible to provide CL.

In the present invention, the first heat-resistant polymer film is formed on the metal foil in this way, and a second heat-resistant polymer different from the heat-resistant polymer is formed on the heat-resistant polymer film layer. However, by appropriately selecting the two heat-resistant polymers, an FMCL having excellent characteristics can be provided. For example, as the first heat-resistant polymer, using a material having excellent heat resistance and adhesion to the metal foil layer,
When a material with high heat resistance and high glass transition temperature is used as the second layer heat-resistant polymer, there is almost no deterioration in adhesion even under severe conditions such as solder immersion, high-temperature continuous processing, and high-temperature and high-humidity processing. Thus, an FMCL suitable for circuit formation can be manufactured. Also, a cover film is often formed after the circuit is formed to protect the circuit. In this case, however, the first layer (that is, when the metal is etched, is exposed, and the cover lay film or the like is directly exposed). It is preferable to use a heat-resistant polymer having a large adhesive strength with the cover film for the film layer that comes into contact with the cover material.

The heat-resistant polymer film layer used in the present invention is made of a heat-resistant polymer having an imide bond, and / or a heat-resistant polymer having a heterocyclic ring other than the imide bond. Examples of the polymer having an imide bond include polyimide, Polyamide imide, polyhydantoin, polyparabanic acid, polyoxazinedione, and the like. Examples of the heat-resistant polymer having a heterocyclic ring other than the imide bond include polybenzimidazole, polyimidazopyrololone, and a triazine derivative.

In the present invention, a heat-resistant polymer film having an imide bond is preferable, and more preferably polyimide,
It is a film of what is called polyamideimide, and these may be a composite film.

Typical polyimides are those whose structural formulas (repeating units) are shown below.

The structural formula of the polyamideimide is shown below.

Further, a polymer obtained from 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride having a repeating unit represented by the structural formula (1) or (2) and an aromatic diamine, 3,3 ', 4,4'-bisphenyltetracarboxylic dianhydride having a repeating unit represented by (3) or (4) is also suitable.

In the above structural formula, X is O, SO ₂ , S, CO, CH ₂ , C
(CH ₃ ) ₂ , C (CF ₃ ) ₂ or a direct bond.

Examples of the aromatic diamine represented by the above structural formula include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, and 3,3'-diamino Examples thereof include diphenylmethane, 3,3'-diaminodiphenyl ether, and 3,3'-diaminodiphenylsulfone.

The aromatic polyimide and / or polyamideimide need not be a single one, but may be a mixture of two or more.

In the present invention, the first layer of the heat-resistant polymer is first formed on a metal foil, and the heat-resistant polymer is applied on the metal foil in a state of being dissolved in a solvent, or the heat-resistant polymer Is applied on a metal substrate in a state where the precursor is dissolved in a solvent. There is no particular limitation on the method of coating, but a known coating device such as a comma coater, a knife coater, a roll coater, or a reverse coater can be used.

Thereafter, the heat-resistant polymer or its precursor is dried by heating to form the first layer, and the residual solvent concentration after the heating and drying is at least 30% or less, preferably 15% or less, and ideally substantially 0%. It is desirable that In addition, when a precursor of a heat-resistant polymer is applied on a metal foil, a reaction such as condensation or cross-linking does not have to proceed during the heating and drying.

For the first heat-resistant polymer film layer, a heat-resistant polymer having excellent adhesion to the metal foil layer is preferably used. Generally, a heat-resistant polymer generally has a lower glass transition temperature and lower adhesive strength.However, the first heat-resistant polymer film layer which is in direct contact with the metal foil is formed after forming the metal foil and the circuit. It is preferable to have a high glass transition temperature of 170 ° C. or more while having a high adhesive strength to the cover material. More specifically, an adhesive polyimide film layer having a glass transition temperature of 170 ° C. or higher is preferable as the first heat-resistant polymer film layer.

In the present invention, a second layer different from the first layer heat-resistant polymer on the first layer heat-resistant polymer side of the laminate in which the first layer heat-resistant polymer is formed on the metal foil [The second layer is not a single layer, and may have a plurality of layers (for example, two layers, three layers) as long as it has the following characteristics.
,...), But in the following description, it will be cumbersome to explain all of them,
Including this, it will be simply described as the second layer. In this case, the heat-resistant polymer dissolved in the solvent or its precursor is applied in the same manner as in the case of forming the first layer of the heat-resistant polymer on the metal foil. The method of applying the polymer of the second layer can be the same as the method of the first layer.

This laminate is then heated and dried to form a second layer. When a heat-resistant polymer precursor is used as the first layer and / or the second layer of the heat-resistant polymer, At this stage, reactions such as condensation and crosslinking must proceed. In such a case, the concentration of the residual solvent is reduced to 30% or less, preferably 15% by heating and drying before performing a reaction such as condensation or crosslinking.
It is desirable that:

The second layer of the heat-resistant polymer that is not directly in contact with the metal foil layer has a high adhesive force with the first layer of the heat-resistant polymer layer,
Further, it is desirable that the glass transition temperature is higher than the glass transition temperature of the first layer, preferably about 300 ° C. or more and about 500 ° C. or less.

The two or more heat-resistant polymer film layers in the present invention, as a basic concept, the adhesive strength to the first heat-resistant polymer film layer that is in direct contact with the metal foil,
The second heat-resistant polymer film layer has high film properties such as heat resistance. For this reason, if the second heat-resistant polymer film layer having relatively high heat resistance with respect to the first layer is too thin, it does not become an excellent FMCL. According to the study of the present inventors, the thickness of the first layer of the heat-resistant polymer film layer is 0.1 to 50 μm, that of the second layer is 0.5 to 250 μm, the first layer of the heat-resistant polymer film The thickness ratio between the layer and the second layer of the heat-resistant polymer film is preferably 0.2 or less and 0.001 or more. If the difference in the coefficient of thermal expansion between the metal foil layer and the second layer of the heat-resistant polymer film that is not directly in contact with the metal foil layer is too large, the curl may occur when the FMCL is heated. Etc. occur. The inventors obtained an excellent FMCL such as a very small curl if the difference in the coefficient of thermal expansion between the metal foil layer and the second heat-resistant polymer film layer was 1.5 × 10 ⁻⁵ or less. Was found to be.

The type of metal foil used in the present invention is not particularly limited, but usually copper, nickel, aluminum and the like are preferably used. The thickness of the metal foil can be arbitrarily selected, but usually
It is in the range of 10 to 100 μm, preferably in the range of 10 to 50 μm.

In addition, in order to increase the adhesive strength between the heat-resistant polymer and the metal foil which are in direct contact with the metal foil, a simple metal or an oxide or alloy thereof on the metal foil, for example, a simple copper when the metal foil is a copper foil It is also preferable to form an inorganic substance such as copper oxide, a nickel-copper alloy, and a zinc-copper alloy. Further, in addition to inorganic substances, a coupling agent such as aminosilane, epoxysilane, mercaptosilane or the like is formed on a metal foil, or a heat-resistant polymer or a precursor solution thereof is mixed with the above-mentioned coupling agent to form a heat-resistant polymer. It is also possible to improve the adhesive strength between the united material and the metal foil.

The FMCL prepared as described above has a dimension between the heat-resistant polymer film layer and the metal foil due to the difference in the coefficient of thermal expansion between the metal foil and the heat-resistant polymer, and the drying shrinkage of the heat-resistant polymer. May have occurred. In such a case, it is also preferable to perform a curl correction operation as shown in International Publication WO 87/05859 to obtain a flat FMCL.

 Next, the present invention will be further described with reference to examples.

Example 1 (1) Synthesis of polyamic acid varnish 1 In a vessel equipped with a stirrer, reflux condenser and nitrogen inlet tube, 221 g (0.60 mol) of 4,4'-bis (3-aminophenoxy) biphenyl and 4,4'-bis (3-aminophenoxy) biphenyl 280 g (1.40 mol) of '-diaminodiphenyl ether was dissolved in 3500 ml of N, N-dimethylacetamide, cooled to about 0 ° C, and 436 g (2.0 mol) of pyromellitic dianhydride was added under a nitrogen atmosphere. Stir for 2 hours. Next, the solution was returned to room temperature and stirred under a nitrogen atmosphere for about 20 hours. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.7 dl / g. This polyamic acid solution was diluted to 19% with N, N-dimethylacetamide, and the rotational viscosity was adjusted to 120,000 cps.

The logarithmic viscosity of the polyamic acid solution thus obtained is 1.8 d
l / g.

(2) Synthesis of polyamic acid varnish 2 In a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube, 421 g of 4,4'-diaminodiphenyl ether (2.1 g) was prepared.
Was dissolved in 4000 ml of N-methylpyrrolidone, and 458 g (2.1 mol) of pyromellitic dianhydride was added under a nitrogen atmosphere, followed by stirring at room temperature for 24 hours.

The logarithmic viscosity of the polyamic acid solution thus obtained is 1.8 d
l / g.

This polyamic acid solution is mixed with N-methylpyrrolidone for 16 hours.
%, And the rotational viscosity was adjusted to 100,000 cps.

(3) Preparation of FMCL The polyamic acid solution obtained in (1) was uniformly cast and applied on an electrolytic copper foil (3EC-III, manufactured by Mitsui Mining & Smelting Co., Ltd., thickness 35 μm), and heated at 135 ° C. The resultant was dried by heating at 180 ° C. for 5 minutes and further at 180 ° C. to form a first layer of a heat-resistant polymer precursor film (polyamic acid) of 5 μm on the copper foil. The total thickness of the thus obtained laminate was 40 μm. In addition, the residual solvent in the polymer layer was 0.01%.

Next, the polyamic acid solution obtained in (2) was uniformly cast and applied on the first polyamic acid layer, and dried by heating at 135 ° C. for 5 minutes and further at 180 ° C. for 4 minutes. Was heated in a nitrogen atmosphere for 5 minutes to obtain FMCL having two polyimide layers on a copper foil. The total thickness of the FMCL thus obtained is 68
μm (the second layer was 28 μm). The glass transition temperature of the first layer is 430 ° C, that of the second layer is 380 ° C, and the coefficient of thermal expansion is
3.1 × 10 ⁻⁵ (/ ° C.).

 The characteristics of this FMCL were as shown in Table 1.

Comparative Example 1 In Example 1, an FMCL was prepared by applying the polyamic acid solution of the second layer directly to a copper foil without applying the polyamic acid of the first layer. The total thickness of the FMCL thus obtained was 68 μm.

 The characteristics of this FMCL were as shown in Table 1.

Example 2 (1) Synthesis of polyamic acid varnish 1,3-bis (3-aminophenoxy) benzene 5 in a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
84 g (2.0 mol) in N, N-dimethylacetamide 3700 ml
At room temperature under a nitrogen atmosphere at 3,3 ', 4,4'-
64 g (2.0 mol) of benzophenonetetracarboxylic dianhydride was added in four portions while paying attention to the rise in solution temperature, and the mixture was reacted at room temperature for about 24 hours.

The logarithmic viscosity of the polyamic acid solution thus obtained is 1.2 d
l / g.

(2) Preparation of FMCL The polyamic acid solution obtained in (1) is uniformly cast and applied on rolled copper foil (Mitsui Mining & Smelting Co., Ltd., BSH, thickness 35 μm), and then at 100 ° C. for 20 minutes. Then, the film was further heated and dried at 150 ° C. for 20 minutes to form a first layer of a heat-resistant polymer precursor film (polyamic acid) on the metal foil. The total thickness of the thus obtained laminate was 39 μm (first layer 4 μm).

Next, a commercially available polyamic acid varnish (Ube Industries, Ltd.)
Co., Ltd., U-varnish S) is uniformly cast and applied on the first polyamic acid layer, and dried by heating at 150 ° C. for 20 minutes.
10 minutes in a nitrogen atmosphere at 400 ° C and 20 minutes in a nitrogen atmosphere at 400 ° C.
FMCL with two polyimide layers on copper foil after heating for a minute
I got The total thickness of the FMCL thus obtained is 68 μm (second layer
29 μm). The glass transition temperature of the first layer is 20
0 ° C, that of the second layer is 340 ° C, and the coefficient of thermal expansion is 1.8 × 10 ^-5 (/
° C).

 The characteristics of this FMCL were as shown in Table 1.

Comparative Example 2 An adhesive between a polyimide film and a copper foil was prepared as follows.

A composition consisting of 50 parts by weight of Epicoat 1001FR manufactured by Yuka Shell Epoxy Co., Ltd., 2 parts by weight of dicyandiamide, and 100 parts by weight of Nipol 1432J manufactured by Nippon Synthetic Rubber Industry as an acrylonitrile butadiene copolymer was used as an epoxy resin. Dissolve to a concentration of 20
% Adhesive solution.

Next, after drying the adhesive on Kapton H manufactured by Dupont Toray Co., Ltd.
It was applied so as to have a thickness of 25 μm, and was run on a heating roll through a predrying furnace. Heating conditions in the predrying oven are 80
C for 3 minutes and 123 C for 5 minutes.

On the other hand, a rolled copper foil (KDK-FLEX, thickness 35 μm, manufactured by K-DKK) is run from the other side of the laminator to a heating roll, and continuously pressed so as to be in close contact with the polyimide film via the adhesive composition. Laminated and wound continuously.

The roll surface temperature of the heating roll was adjusted to 150 ± 2 ° C.

 The pressing time between the rolls is about 0.5 seconds.

Next, the wound laminate is kept at 155 ° C.
Received 2 hours after cure.

 The characteristics of this FMCL were as shown in Table 1.

[Effect of the Invention] Two or more layers on the metal foil proposed by the present invention An FMCL having a heat-resistant polymer film layer can provide excellent properties as shown in Examples and Table 1 by appropriately selecting a heat-resistant polymer.

That is, since such FMCL does not have an adhesive layer, it has good heat resistance, and can be excellent in adhesiveness, folding resistance, heat deterioration, and the like.

Claims (2)

(57) [Claims] (1) The thickness of an adhesive polyimide film layer having a glass transition temperature of 170 ° C. or more and a polyimide film layer having a glass transition temperature of 300 ° C. or more and 500 ° C. or less, which is in direct contact with a metal foil. A flexible metal foil characterized in that the ratio is 0.001 or more and 0.2 or less, and a polyimide or a precursor thereof dissolved in a solvent is sequentially applied onto the metal foil and then heated to form two or more film layers. A method for manufacturing a laminate. 2. An adhesive polyimide or a precursor thereof dissolved in a solvent is coated on a metal foil, and the residual solvent concentration is 30%.
Step of heating and drying until the following, and then applying a polyimide or a precursor thereof having a different composition from the adhesive polyimide or a precursor thereof, followed by heating and drying to form at least two polyimide film layers on the metal foil. The method for producing a flexible metal foil laminate according to claim 1, comprising: