JPH08281866A - Production of flexible metal foil laminated sheet - Google Patents

Abstract

PURPOSE: To produce a flexible metal foil laminated sheet reduced in material cost by requiring no special surface treatment to metal foil, capable of corresponding to various metal foils and excellent in heat resistance, chemical resistance and electric characteristics. CONSTITUTION: In a method for producing a flexible metal foil laminated sheet wherein a polyimide layer is provided between two metal foil layers, the amt. of the volatile component present in the polyimide layer is below 0.3% by wt. of the polyimide layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a flexible metal foil laminate, which is becoming popular in the electronic industry.

[0002]

2. Description of the Related Art A polyimide metal foil laminate is mainly used as a base material for a flexible printed wiring board,
In addition, it is also used for sheet heating elements, electromagnetic wave shielding materials, flat cables, packaging materials, etc. In recent years,
As electronic devices using printed wiring boards are becoming smaller and higher in density, the use of polyimide metal foil laminates, which enables high-density mounting of components and elements, is increasing. However, since the conventional flexible metal foil laminate is manufactured by bonding a polyimide film and a metal foil using an adhesive such as an epoxy resin, heat resistance, chemical resistance, electrical characteristics, etc. The characteristics are dominated by the characteristics of the adhesive used, the excellent various characteristics of the polyimide are not fully utilized, and particularly the heat resistance is not sufficient.

In order to overcome the drawbacks of the conventional flexible metal foil laminate having an adhesive, usually, a polyimide solution or a polyamic acid solution which is a precursor of a polyimide is directly cast and coated on the metal foil, Attempts have been made to obtain a flexible metal foil laminate which has no adhesive layer and whose insulating layer is entirely made of polyimide.
In addition, one or both sides of the polyimide film, laminated polyimide having adhesiveness, the polyimide laminate and a metal foil are overlaid and thermocompression bonded, a flexible metal foil laminate plate in which the same insulating layer is entirely made of polyimide. Attempts have been made to obtain it.

However, when a copper foil is selected as the metal foil by using these methods, the adhesive strength between the copper foil having a smooth surface and the polyimide is low, and a satisfactory product cannot be obtained. In order to overcome this drawback, the surface of the copper foil in contact with the polyimide is subjected to various surface treatments such that the surface of the copper foil is made uneven in advance to increase the surface area.

[0005]

However, as the applications of flexible metal foil laminates have expanded, a surface treatment effective for polyimide has been developed not only for copper foil but also for various metal foils. It is necessary to increase the material cost and development period.
Therefore, there is a demand for a technique for adhering a metal and a polyimide that can obtain a sufficient adhesive force even on a smooth surface of a metal foil that has not been surface-treated. The present invention is a flexible metal foil laminate using polyimide having excellent heat resistance, chemical resistance, electrical characteristics, etc. as an insulator, and provides sufficient adhesion between the metal foil having a smooth surface and the polyimide. The present invention provides a method for producing a flexible metal foil laminate, which can be obtained.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, by controlling the amount of volatile components present in the polyimide layer, conventionally, the adhesion of the interface between the metal foil and the adhesive layer of the polyimide layer was adhered. The inventors have found that good adhesive strength can be obtained even with a smooth metal foil having low strength, and completed the present invention.

That is, the present invention is a method for producing a flexible metal foil laminate having a polyimide layer between two metal foil layers, wherein the polyimide layer is formed with thermoplastic polyimide on both sides. , A flexible metal foil laminate comprising a polyimide laminate having a three-layer structure, and laminating metal foil layers on both sides of the polyimide laminate, followed by thermocompression bonding, of a volatile component present in the polyimide layer. A method for producing a flexible metal foil laminate, characterized in that the amount is less than 0.3% by weight relative to the polyimide layer, and a flexible metal having a polyimide layer between two metal foil layers. A method for manufacturing a foil laminate, wherein at least the outermost polyimide layer with respect to the metal foil layer is thermoplastic thermoplastic resin on one metal foil layer. Flexible metal produced by stacking a thermoplastic polyimide layer and a metal foil layer on a polyimide / metal foil laminate on which a polyimide layer made of rimide is formed, and the other metal foil layer, and heating and pressing the thermoplastic polyimide layer and the metal foil layer. In the foil laminate, the amount of volatile components present in the polyimide layer is in a weight ratio to the polyimide layer.
A method for producing a flexible metal foil laminate, wherein the center line average roughness of the metal foil surface of at least one of the metal foil layers is 0.10 μm.
And / or a ten-point average roughness of less than 1.00 μm, which is a method for producing a flexible metal foil laminate, wherein the type of the metal foil layer is copper, iron,
A method for producing a flexible metal foil laminate, which is a metal foil made of nickel, chromium, molybdenum, aluminum or an alloy mainly containing these.
Hereinafter, the present invention will be described in detail.

There is no particular limitation on the type of metal foil used in the present invention, and copper and copper alloys, iron, nickel, chromium,
Molybdenum, aluminum, stainless steel, beryllium copper alloy, etc. can be used.

The thickness of the metal foil used in the present invention is not particularly limited, but it is usually in the range of 5 to 175 μm, and preferably in the range of 9 to 105 μm.

Although the present invention is not governed by the surface roughness of the metal foil in contact with the polyimide, the center line average roughness (hereinafter referred to as Ra) and the standard roughness in JIS B 0601 (definition and indication of surface roughness) and Point average roughness (hereinafter referred to as Rz)
The value indicated by is less than 0.10 μm for Ra and / or less than 1.00 μm for Rz, the effect is particularly great.

Further, the present invention is not governed by the surface roughness of the metal foil in contact with the polyimide, but on the metal foil, an inorganic substance such as a simple substance of metal or its oxide, or a coupling of aminosilane, epoxysilane, mercaptosilane, etc. Forming an agent, sandblasting the metal foil surface,
Treatments such as honing treatment, corona treatment, plasma treatment, and etching treatment can be used together.

The polyimide layer of the present invention is formed by laminating thermoplastic polyimide on both sides of a polyimide film. The polyimide film used here, even if using a commercially available polyimide film,
A material formed by a casting method, an injection method, a stretching method or the like may be used.

The thermoplastic polyimide in the present invention is
A polymer having an imide structure in its main chain, which has a glass transition temperature preferably in the range of 150 to 350 ° C., and whose elastic modulus sharply decreases in the temperature range above this glass transition temperature.

The polyimide layer of the present invention can also be formed by laminating a metal foil with polyimide and / or thermoplastic polyimide. The polyimide layer may be thermoplastic polyimide as the outermost layer involved in the adhesion with the metal foil layer, and may be a single layer or different polyimide layers. The polyimide other than the polyimide of the surface layer is not necessarily a thermoplastic polyimide. Also, if even the surface layer is a thermoplastic polyimide,
A gradient material composed of a plurality of polyimide components may be used.

The thickness of the polyimide layer as the insulating layer in the present invention is not particularly limited, but is usually in the range of 5 to 150 μm, and preferably in the range of 8 to 50 μm. Further, the thickness of the thermoplastic polyimide layer,
It can be made sufficiently thin within a range not lower than the surface roughness of the metal foil. However, even if there are irregularities in the equipment and auxiliary materials used in the thermocompression bonding process, 1
μm or more is preferred.

The surface of the polyimide layer or the polyimide film of the present invention may be subjected to treatments such as sandblasting, honing, corona treatment, plasma treatment and etching treatment.

In the present invention, a thermoplastic polyimide is laminated on a polyimide film or a polyimide and / or a thermoplastic polyimide is laminated on a metal foil to form a polyimide layer. The polyimide and / or the thermoplastic polyimide is It is preferable that the polyimide or a precursor of the polyimide is dissolved in a solvent and applied onto a polyimide film or a metal foil, and this is heated to a tack-free state. There is no particular limitation on the coating method, and a comma coater, knife coater,
A known coating device such as a roll coater, a reverse coater, a die coater, a gravure coater, and a wire bar can be used. The heating method is hot air, hot nitrogen,
A well-known method such as far infrared ray or high frequency wave can be used.

After the desired polyimide layer is formed on the polyimide film or the metal foil, the volatile components in the layer are removed, and when the polyimide precursor is applied, the condensation reaction is completed, so it is sufficient. It is necessary to heat. As the heating method in this case, various known methods according to the above can be used. The heating temperature is preferably higher than the glass transition temperature of the polyimide to be laminated. When the polyimide layers are formed on both sides of the polyimide film, it is particularly useful to use the air float method in order to avoid contact with other objects during heating. When formed on the metal foil layer, heating in an inert gas is also useful in order to avoid oxidative deterioration of the metal foil.

In the present invention, it is very important that the amount of volatile components contained in the polyimide layer is less than 0.3% by weight with respect to the polyimide layer. The volatile component mentioned here refers to water, residual solvent, and the like generated when the polyimide precursor undergoes dehydration ring closure. As a method for quantifying these, for example, a method of capturing a component generated at a temperature of about 300 ° C. by a gas chromatograph device and the like are used. If the amount of this volatile component is 0.3% or more in terms of weight ratio with respect to the polyimide layer, the adhesive force with a smooth metal surface is reduced. This volatile component can be removed by drying the polyimide laminate or the polyimide / metal foil laminate before the above heating step and thermocompression bonding.

As a method of reducing the volatile component in the polyimide layer to less than 0.3%, the temperature in the heating step, the boiling point of the solvent of the polyimide or polyimide precursor,
It is necessary to set the glass transition temperature of the polyimide to a temperature higher than both of them, preferably to 40 ° C. or higher, and to heat. If the heating temperature is simply higher than the boiling point of the solvent, the amount of volatile components will be 0.3% regardless of the heating time.
It is difficult to make it less than%. By heating not only at the boiling point of the solvent but also at a temperature higher than the glass transition temperature of the polyimide, the volatile component in the polyimide layer is 0.3%.
It can be less than. In this way, by setting the volatile component in the polyimide layer to less than 0.3%, it is possible to obtain a sufficient adhesive force between the polyimide and the metal foil without subjecting the metal foil to the surface treatment.

The flexible metal foil laminate is completed by stacking the polyimide laminate or the polyimide / metal foil laminate and the metal foil obtained as described above and heat-pressing them. As the method for thermocompression bonding, a known method such as hot lamination using a hot roll or hot pressing can be appropriately used. The heating conditions depend on the glass transition temperature of the thermoplastic polyimide used,
It is preferably at least the glass transition temperature, more preferably at least 20 ° C from this point. Pressurization conditions are generally 20-150k
A range of g / cm2 is used.

[0022]

The present invention will be described in more detail with reference to the following examples and comparative examples. [Examples 1 to 3 and Comparative Examples 1 to 3] Commercially available polyimide film (Kanefuchi Chemical Co., Ltd., Apical AH, thickness; 25 μm)
m) was applied with a polyamic acid solution (PI-A, manufactured by Mitsui Toatsu Chemical Co., Inc.), which is a precursor of thermoplastic polyimide, on both sides of the polyimide film with a coater and dried to obtain a polyimide laminate. At this time, the amount of volatile components in the polyimide laminate was controlled by changing the drying conditions as follows. For Examples 1 to 3, 30, 20, and 10 at 240 ° C., which is approximately 40 ° C. higher than the glass transition temperature, respectively.
Heated for minutes. Comparative Examples 1 to 3 were respectively heated at 200 ° C., which is a glass transition temperature, for 30, 20 and 10 minutes. The amount of volatile components was measured using a gas chromatograph (manufactured by Shimadzu Corporation, GC-14A). The thickness of the obtained thermoplastic polyimide layer was 2.5 μm on each side for each of the examples and comparative examples.

A rolled copper foil (manufactured by Japan Energy, BHY-02B-T, thickness: 18 μm, Ra;
0.14 μm, Rz; 1.85 μm) and stainless steel foil (Nisshin Steel, SUS304H-TA, thickness; 50 μm, Ra; 0.04 μm, Rz; 0.4
7 μm) were laminated in a combination of three types, that is, rolled copper foil on both sides, stainless steel foil on both sides, and rolled copper foil on one side and stainless steel foil on the other side, and hot pressed using a hot press. The surface roughness of copper foil and stainless steel foil is measured by a surface roughness meter (Kosaka Laboratory, Surfcoder SE-3).
It is the value measured in 0D). The peel strength of each metal foil / polyimide interface of the obtained flexible metal foil laminate was measured. As described above, Examples 1 to 3 and Comparative Examples 1 to 3
The results are shown in Table 1. SUS in the table is stainless steel foil, RC
u indicates rolled copper foil.

[0024]

[Table 1]

[Examples 4 to 6 and Comparative Examples 4 to 6] Commercially available electrolytic copper foil (manufactured by Nippon Denshoku Co., Ltd., SLP, thickness; 35 μm, Ra; 0.52)
μm, Rz; 4.48 μm) with a polyamic acid solution (Mitsui Toatsu Chemical Co., PI-KBP2) applied by a coating machine and dried,
Further, a polyamic acid solution (PI-A manufactured by Mitsui Toatsu Chemical Co., Inc.), which is a precursor of thermoplastic polyimide, was applied and dried to obtain a polyimide / metal foil laminate. At this time, the amount of volatile components in the polyimide layer was controlled by changing the drying conditions as follows. For Examples 4 to 6, heating was carried out for 15 minutes, 10 minutes, and 5 minutes at 400 ° C., which is approximately 50 ° C. higher than the glass transition temperature. For Comparative Examples 4 to 6, the glass transition temperature was about 15 ° C.
Heated for min, 10 min, 5 min. The thickness of the obtained polyimide layer was 15 μm in all the polyimide layers for each of the examples and comparative examples, and the thickness of the thermoplastic polyimide layer was 2.5 μm.

On the polyimide side of this polyimide / metal foil laminate, the above-mentioned stainless steel foil, rolled copper foil, nickel foil (made by Toyo Seifun, thickness: 20 μm, Ra; 0.05 μm, Rz; 0.55 μ
m) were overlaid and thermocompression bonded using a hot press. The peel strength of each metal foil / polyimide interface of the obtained flexible metal foil laminate was measured. The results of Examples 4 to 6 and Comparative Examples 4 to 6 are shown in Table 2 above. In the table, ECu indicates electrolytic copper foil, RCu indicates rolled copper foil, SUS indicates stainless steel foil, and Ni indicates nickel foil.

[0027]

[Table 2]

[0028]

As described above, according to the present invention,
It is possible to manufacture a flexible metal foil laminate having excellent adhesiveness at the interface between a metal foil having a smooth surface and a polyimide and having excellent heat resistance, chemical resistance, electrical characteristics, and the like. As a result, it is possible to omit the surface treatment step for the metal foil, which has been essential until now, and it is possible to reduce the material cost. Further, it is possible to manufacture a flexible metal foil laminated plate which can be applied to a wide variety of metal foils regardless of the surface condition of the metal foil.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Takahashi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A method for producing a flexible metal foil laminate having a polyimide layer between two metal foil layers, the method comprising:
The polyimide layer is composed of a polyimide laminate having a three-layer structure in which thermoplastic polyimide is formed on both sides of the polyimide film, and is manufactured by stacking metal foil layers on both sides of the polyimide laminate and thermocompression bonding. In the flexible metal foil laminate, the amount of volatile components present in the polyimide layer is less than 0.3% in weight ratio with respect to the polyimide layer. 2. A method for producing a flexible metal foil laminate having a polyimide layer between two metal foil layers, the method comprising:
A polyimide / metal foil laminate in which a polyimide layer in which at least the outermost polyimide layer is made of thermoplastic polyimide is formed on at least one metal foil layer,
The other metal foil layer, the thermoplastic polyimide layer and the metal foil layer are overlapped, in a flexible metal foil laminate produced by heat-pressing, the amount of volatile components present in the polyimide layer, A method for producing a flexible metal foil laminate, characterized in that the weight ratio to the polyimide layer is less than 0.3%. 3. The center line average roughness of the metal foil surface of at least one of the metal foil layers is less than 0.10 μm and / or the ten-point average roughness is less than 1.00 μm. 2. The method for producing a flexible metal foil laminate according to 2. 4. The type of metal foil layer is a metal foil made of copper, iron, nickel, chromium, molybdenum, aluminum or an alloy mainly containing these, and any one of claims 1 to 3 is provided. A method for producing a flexible metal foil laminate according to.