JP2708505B2 - Flexible metal foil laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flexible copper foil laminate (Flexible Copper Clad Laminat) which is becoming widespread in the electronics industry.
e, hereinafter abbreviated as FMCL).

2. Description of the Related Art FMCL is mainly used as a base material for a flexible printed wiring board, but is also used as a material for electromagnetic wave shielding, a surface heating element, 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, for example, a reduction in the size of kales that house the printed wiring boards.

Conventionally, such an FMCL is usually manufactured by bonding a heat-resistant polymer film to a metal foil using an adhesive made of an organic polymer having a thickness of 5 μm or more. However, FMCL using this adhesive cannot fully utilize the excellent properties of the heat-resistant polymer film due to insufficient properties of the adhesive, and there is a problem in particular in terms of heat resistance. Was.

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.
179,634, 3,736,170, JP-A-49-129,862, 58
-190,091 and 59-162,044.

However, adhesive free FM by these methods
When CL is used for a printed wiring board, it is often immersed in solder. However, at this time, curl, wrinkles, irregularities, and the like are generated due to heat shrinkage, and there is a defect in practical use. In particular, in the case of polyimide and polyamideimide among the heat-resistant polymers, it is difficult to reduce the heat shrinkage due to various causes.

[Problems to be Solved by the Invention] FMCL in which a polyimide film is bonded to a metal foil via an adhesive layer made of an organic polymer such as an epoxy resin or an acrylic resin having a thickness of 5 μm or more has already been proposed. Existing FMCLs using adhesives made of such organic polymers do not attain the required properties in many respects. Further, FMCL without an adhesive layer is superior to FMCL with an adhesive layer in terms of heat resistance, but it cannot be said that heat shrinkage has been sufficiently studied.

In view of such a situation, the present invention maintains the situation in which the excellent properties of the heat-resistant polymer film are utilized, while the heat-resistant polymer film is firmly and stably bonded to the metal foil, and has a small heat shrinkage. Providing excellent FMCL,
Such FMCLs are extremely useful in industrial settings, especially in the electronics industry.

Means for Solving the Problems That is, the present invention provides: (1) a heat-resistant polymer film layer, and a flexible metal foil laminate having a metal foil layer on at least one surface of the heat-resistant polymer film layer In the above, the heat shrinkage of the heat-resistant polymer film layer at 260 ° C. is 0.1% or less, and
A flexible metal foil laminate, wherein the metal foil layer is subjected to compression plastic deformation and subsequently heated at a temperature not higher than the glass transition temperature of the heat-resistant polymer film layer for 30 seconds or more; (3) The flexible metal foil laminate according to the above (1), wherein after the flexible metal foil laminate is heated, the metal foil layer of the flexible metal foil laminate is further subjected to compression plastic deformation. When the metal foil is completely etched after the foil layer is compression-plastically deformed, the shrinkage of the polymer film layer is reduced by the compression-plastic deformation of the metal foil layer before etching. ± based on the dimensions of the laminate
The flexible metal foil laminate according to the above (2), which is within 0.3%.

That is, the gist of the present invention is that, after a heat-resistant polymer film layer having a large adhesive force with a metal foil is formed on the surface of the metal foil to form an FMCL, the FMCL is annealed by heating to significantly reduce the heat shrinkage. Reduced
The point is FMCL.

 Hereinafter, the present invention will be described in detail.

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, Examples thereof include polyamideimide, polyhydantoin, polyparabanic acid, and polyoxazineone. Examples of the heat-resistant polymer having a heterocyclic ring other than the imide bond include polybenzimidazole, polyimidazopyrrolone, and a triazine derivative.

In the present invention, a heat-resistant polymer having an imide bond is preferred, more preferably a polyimide or a polyamideimide, and these may be combined.

A typical polyimide is represented by the following structural formula.

The structural formula of the polyamideimide is shown below.

Further, a polymer obtained from pyromellitic dianhydride having a repeating unit represented by the structural formula (1) and an aromatic diamine, a polymer having a repeating unit represented by a structural formula (2),
Polymer obtained from 3 ', 4,4'-benzophenonetetracarboxylic dianhydride and aromatic diamine, and 3,3', 4,4'- having a repeating unit represented by structural formula (3) Also suitable are polymers obtained from biphenyltetracarboxylic dianhydrides and aromatic diamines.

In the above structural formula, R is a residue excluding the amino group of the starting diamine, and examples of the diamine containing R as the starting material include o, m, p-phenylenediamine, 4,4′-diaminodiphenylmethane , 3,3'-diaminodiphenylmethane, 4,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminoterphenyl, 3,3'-diaminoterphenyl, 4,4'-diaminodiphenyl ether , 3,3'-diaminodiphenyl ether, 4,4'diaminodiphenylsulfone, 3,3'diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, 3,3 '
-Diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulphoxide, 3,3'-diaminodiphenyl sulphoxide, 4,4'-diaminobenzophenone, 3,
3'-diaminobenzophenone, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, bis [4- (4-aminophenoxy) phenyl] methane, bis [4- (3-aminophenoxy)
Phenyl] methane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-
Aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,
3,3-hexafluoropropane, 2,2-bis [4- (3-
Aminophenoxy) phenyl] 1,1,1,3,3,3-hexafluoropropane, 1,3-bis (4-aminophenoxy)
Benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, bis [4- (4- Aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl]
Ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy)
Phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4-
(3-aminophenoxy) phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] ether, 4,4′-bis (4-aminophenylsulfonyl) ) Diphenyl ether, 4,4'-bis (3-aminophenylsulfonyl) diphenyl ether, 4,4'-bis (4-aminothiophenoxy) diphenylsulfone,
Symmetric diamines such as 4'-bis (3-aminothiophenoxy) diphenylsulfone and 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene are mentioned, and these may be used alone or in combination of two or more. And a copolymer.

To synthesize the above heat-resistant polymer, an organic solvent such as N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, γ-butyrolactone, cresol, phenol, halogenated phenol, etc. It is preferably carried out in a solvent of

In the present invention, usually, a heat-resistant polymer is 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 a precursor of the heat-resistant polymer is dissolved in the solvent. It is applied on a metal foil in a dissolved state. 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.

After this, a heat-resistant polymer or a precursor thereof is applied and dried to form a heat-resistant polymer film, and then the metal foil is heated.The heating method may be a known method such as hot nitrogen, far infrared rays, and high frequency. Can be used. The residual solvent concentration of the heat-resistant polymer film of FMCL thus obtained is
1% or less, preferably 0.1% or less, more preferably 0.0%
5% or less, most preferably substantially zero.

In the present invention, the heat-resistant polymer formed on the metal foil may be composed of two or more layers of the heat-resistant polymer.
For example, after forming the first layer of the heat-resistant polymer on the metal foil, a second layer of the heat-resistant polymer having a composition different from that of the first layer of the heat-resistant polymer may be formed. . In such a case as well, the method of applying the heat-resistant polymer and the method of heating are not particularly limited, but the above-mentioned known devices can be used.

The thickness of the metal foil can be arbitrarily selected, but usually 10 to 10
It is in the range of 0 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 coalesced and the metal foil.

The FMCL prepared as described above has a difference in dimension between the heat-resistant polymer and the metal foil due to a difference in the coefficient of thermal expansion between the metal foil and the heat-resistant polymer, and a drying shrinkage of the heat-resistant polymer. May have occurred. In such a case, as shown in Japanese Patent Application No. 62-238864, filed by the present applicant, the metal foil layer of the FMCL is formed not in the thickness direction of the layer but in the longitudinal direction (plane direction) along the layer. It is also preferable to reduce the dimensional difference between the metal foil layer and the heat-resistant polymer film layer by shrinking (compressing) plastic deformation. By this operation, the dimensional difference between the metal foil layer and the heat-resistant polymer film layer can be made preferably within ± 0.3%.

The FMCL obtained as described above is often immersed in a solder bath after circuit processing. At this time, this FM
In CL, the heat-resistant polymer film layer often shrinks due to residual stress, residual solvent, and the like. In such a case, in the present invention, after the heat-resistant polymer is formed on the metal foil,
It is preferable to reduce the heat shrinkage by heating at least 30 seconds or more at a temperature lower than the glass transition temperature of the heat-resistant polymer film layer. Originally, when used as a printed wiring board, FMCL is suitable because it has a small heat shrinkage and a small difference in size between the metal foil layer and the heat-resistant polymer film layer. Perform the operation.

The heat shrinkage is a value measured after heating at 260, returning to room temperature and 1 hour later. Measurement conditions other than temperature
IPC-TM-650 method 2.2.4 Method c.

After performing the heating operation as described above, the dimensional difference between the metal foil layer and the heat-resistant polymer film layer may increase. In such a case, Japanese Patent Application No. 62-238864 is again filed.
It is also preferable to reduce the dimensional difference by shrinking (compressing) plastically deforming the metal foil layer of the FMCL as shown in the above item.

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

Example 1 (1) Synthesis of polyamic acid varnish 147 g (0.40 mol) of 4,4'-bis (3-aminophenoxy) biphenyl and 4,4 'in a vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube. Dissolve 320 g (1.60 mol) of diaminodiphenyl ether in 3500 ml of N, N-dimethylacetamide, cool to about 0 ° C., add 436 g (2.0 mol) of pyromellitic dianhydride under nitrogen atmosphere, and add Stirred for 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 glass transition temperature is 370 ° C.

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

(2) 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. After heating and drying at 180 ° C. for 5 minutes and further at 250 ° C. for 5 minutes, FMCL having a polyimide layer on a copper foil was obtained by heating in a nitrogen atmosphere at 250 ° C. for 5 minutes. The total thickness of the FMCL thus obtained was 65 μm.

The copper foil layer of the FMCL obtained above was shrunk (compressed) and plastically deformed by the method shown in Japanese Patent Application No. 62-238864, so that the dimensional difference between the copper foil layer and the heat-resistant polymer film layer was ± 0.3. %.

The FMCL obtained above was converted to a glass transition temperature of 260 ° C.
For 1 minute. When the film obtained by removing the copper foil of the FMCL obtained by etching was heated at 260 ° C. for 1 minute and returned to room temperature, the film shrunk by 0.05% compared to the film before heating. That is, the heat shrinkage of the heat-resistant polymer film layer of the FMCL thus obtained is 0.05%. The method of measuring the heat shrinkage was in accordance with IPC-TM-650 method 2.2.4 method c except for the heating temperature and time.

Thereafter, the copper foil layer of this FMCL was subjected to shrinkage plastic deformation by the method shown in Japanese Patent Application No. 62-238864. This FMCL is wrinkled even when immersed in a solder bath at 260 ° C after the circuit is formed.
It was confirmed that a good printed wiring board having almost no shrinkage, unevenness, etc. was obtained.

Comparative Example 1 In Example 1, a heat-resistant polymer film layer was formed on a copper foil to form an FMCL. After the copper foil layer was subjected to shrinkage (compression) plastic deformation, the circuit was heated at 260 ° C. without heating. When formed and immersed in a 260 ° C. solder bath, wrinkles, shrinkage, and irregularities occurred. When the film from which the copper foil of the FMCL was removed by etching was heated to 260 ° C. for 1 minute and returned to room temperature, the film shrank by 0.25% compared to the film before heating.

[Effect of the Invention] The FMCL proposed by the present invention, in which the heat-shrinkage rate of the heat-resistant polymer film layer is within 0.1%, is the same as the FMCL in which wrinkles, shrinkage, irregularities and the like generated after immersion of solder after circuit formation are extremely small. Can be.

Such FMCL has good heat resistance because it does not have an adhesive layer, and is excellent in adhesiveness, heat deterioration property of adhesiveness, folding resistance and the like.

Claims (3)

(57) [Claims] A flexible metal foil laminate having a heat-resistant polymer film layer and a metal foil layer on at least one surface of the heat-resistant polymer film layer, wherein the heat-resistant polymer film layer has a temperature of 260 ° C. Has a heat shrinkage of 0.1% or less,
And, the metal foil layer is compression-plastically deformed, and subsequently, at a temperature equal to or lower than the glass transition temperature of the heat-resistant polymer film layer, for 30 seconds.
A flexible metal foil laminate characterized by being heated for at least two seconds. 2. The flexible metal foil laminate according to claim 1, wherein the metal foil layer of the flexible metal foil laminate is further compression-plastically deformed after the flexible metal foil laminate is heated. 3. When the metal foil layer is completely etched after the metal foil layer is compression-plastically deformed, the shrinkage of the polymer film layer is caused by the compression-plastic deformation of the metal foil layer. 3. The flexible metal foil laminate according to claim 2, wherein (a) is within ± 0.3% based on the dimensions of the laminate before etching.