JP2000052480A - Flexible metal laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dimensional stability of a flexible metal laminate by using an adhesive sheet controlled to have a thickness such that the thermal expansion coefficient is the same as the metal as an insulation layer between the metals. SOLUTION: This metal laminate has an adhesive sheet on an insulation layer. An example of a non-thermoplastic resin used in a base film on the adhesive sheet may be polyimide, amideimide, amide or the like. The thermal expansion coefficient of the adhesive sheet is controlled such that, after the base film having a lower thermal expansion coefficient than the thermal expansion coefficient of the metal used is selected, the thermal expansion coefficient of the thermoplastic resin polyimide forming the base film and the adhesive layer is satisfied with the following equation: the thermal expansion coefficient of the metal = the thermal expansion coefficient of the adhesive sheet = (thermal expansion coefficient of the base film × the thickness of the base film + the thermal expansion coefficient of the adhesive × the total thickness of the adhesive layer)/(the total thickness of the adhesive sheet), thereby determining the thickness of the adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible metal laminate obtained by heat-pressing a metal to a metal using an adhesive sheet, among metal foil laminates that are becoming widespread in the electronics industry.

[0002]

2. Description of the Related Art In a flexible metal laminate used for a printed circuit board or the like, the coefficient of thermal expansion of a metal portion and that of an insulating layer made of a polymer material are significantly different.

However, there is a problem that such a metal laminate is deviated from zero in proportion to the difference in thermal expansion coefficient between the metal and the insulating layer in terms of dimensional stability, which is a problem when processing wiring or the like. Was.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a flexible metal laminate having excellent dimensional stability.

[0005]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that the thermal expansion coefficient and the thickness of the adhesive film and the base film of the adhesive sheet forming the insulating layer are controlled to reduce the thermal expansion coefficient of the insulating layer. The inventors have found that the thermal expansion coefficient is equal to that of metal, and have completed the present invention. That is, the present invention provides a metal laminate having improved dimensional stability by making the thermal expansion coefficients of the respective layers uniform with respect to a temperature change of the metal laminate, and as an insulating layer between the metal and the metal, A base film made of a non-thermoplastic resin having a smaller coefficient of thermal expansion than the metal to be bonded is used. On both sides of the base film, the base film is made of a thermoplastic resin or a thermosetting resin having a larger coefficient of thermal expansion than the metal to be bonded. The present invention is characterized in that the adhesive layer is formed by controlling the thickness of the adhesive sheet so that the coefficient of thermal expansion of the entire adhesive sheet becomes the same as that of the metal to be adhered.

According to the present invention, a metal laminate having the same thermal expansion coefficient as the entire product and the same thermal expansion coefficient as the material constituting each layer can be obtained. When used in a processed product formed in a layer, excellent dimensional stability is exhibited without impairing the inherent adhesive properties of the adhesive layer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The metal laminate according to the present invention is basically provided with an adhesive sheet on an insulating layer, and the metal adhered to both sides thereof may be made of any material as long as it has the same coefficient of thermal expansion. But the same is true. Examples of the type of the metal foil layer include a metal foil made of copper, iron, nickel, chromium, molybdenum, aluminum, and an alloy mainly containing these. In particular, typical alloys include stainless steel, beryllium copper alloy, copper nickel alloy and the like.

As the base film used for the adhesive sheet, a commercially available non-thermoplastic resin film may be used, or a film formed by a casting method, an injection method, a stretching method or the like may be used. However, the selection of the base film depends on the kind of metal of the adherend. Non-thermoplastic resins usually used as a base film include polyimide, amide imide and amide.

More specifically, there may be mentioned a polyimide film Upilex series manufactured by Ube Industries, Ltd., a polyimide film Apical series manufactured by Kanegafuchi Chemical Co., a polyimide film Kapton series manufactured by DuPont, and an amide film Aramica series manufactured by Toray Industries. Can be

The control of the thermal expansion coefficient of the adhesive sheet is as follows.
Basically, after selecting a base film with a coefficient of thermal expansion lower than the coefficient of thermal expansion of the metal to be used, the coefficient of thermal expansion of the thermoplastic polyimide forming the base film and the adhesive layer is determined using the following empirical formula. Estimate the layer thickness.

Coefficient of thermal expansion of metal = Coefficient of thermal expansion of adhesive sheet = (Coefficient of thermal expansion of base film × Thickness of base film + Coefficient of thermal expansion of adhesive × Total thickness of adhesive layer) / Total thickness of adhesive sheet The same or different adhesive layers may be used on both sides of the adhesive layer.

After the adhesive sheet having the adhesive layer thickness estimated as described above is prepared, the thermal expansion coefficient is measured, and the thickness is again adjusted and controlled so that the adhesive layer thickness is actually the same as that of the metal. Here, the same coefficient of thermal expansion as the metal means that the coefficient of thermal expansion of the adhesive sheet is ± 5 with respect to the coefficient of thermal expansion of the metal.
While the object of the present invention is sufficiently achieved within the range of ppm or less, it is preferably ± 2 ppm or less.

The thermoplastic resin used as the adhesive layer may be a thermosetting resin such as polyimide, polyamide, polyamideimide, polyetherimide, polyether, epoxy or acrylic. Preferably, as an adhesive layer, in order to obtain good adhesion to various metals and metal foils with a thickness of 10 μm or less, thermoplastic polyimide, thermoplastic polyamide, thermoplastic polyamide-imide,
Thermoplastic polyetherimide is used. The bonding with the metal is performed by press bonding with a press, a laminator or the like.

[0014]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. Example 1 An all-polyimide adhesive sheet formed by using a polyimide film, Apical NPI (12.5 μm in thickness) manufactured by Kaneka Chemical Industry Co., Ltd. as a base film, and a thermoplastic polyimide made by Mitsui Chemicals, PI-A (2 μm in thickness) on both sides, and OLIN Rolled copper foil C7025 (18μm thickness), Nippon Steel stainless steel foil SUS304
H-TA (thickness: 20 μm) was laminated on both sides of the adhesive sheet, and hot-pressed using a hot press. The thus obtained adhesive sheet had a coefficient of thermal expansion of 22 ppm, and the dimensional stability of the metal laminate was -0.04%.

COMPARATIVE EXAMPLE 1 A polyimide film, Apical NPI (12.5 μm in thickness) manufactured by Kanefuchi Chemical Industry Co., Ltd. was used as a base film, and all-polyimide bonding was performed by forming thermoplastic polyimide, PI-A (10 μm in thickness) on both sides thereof. Sheet and rolled OLIN rolled copper foil C7025 (18μm thick), Nippon Steel stainless steel foil SUS304
H-TA (thickness: 20 μm) was laminated on both sides of the adhesive sheet, and hot-pressed using a hot press. The adhesive sheet thus obtained had a coefficient of thermal expansion of 40 ppm, and the dimensional stability of the metal laminate was -0.15%.

Example 2 A polyimide film made of Dupont, Ka was used as a base film.
pton-ENZT (thickness: 50 μm) and thermoplastic polyimide PI-AU (thickness: 4)
μ) formed all-polyimide adhesive sheet and rolled copper foil BHY-02B-T (thickness 1
8 μm). The adhesive sheet thus obtained had a coefficient of thermal expansion of 18 ppm, and the dimensional stability of the metal laminate was -0.02%.

Comparative Example 2 A base film made of a polyimide film made of Dupont, Ka
pton-ENZT (thickness: 50 μm) and thermoplastic polyimide PI-AU (thickness: 10 μm)
μ) formed all-polyimide adhesive sheet and rolled copper foil BHY-02B-T (thickness 1
8 μm). The adhesive sheet thus obtained had a coefficient of thermal expansion of 27 ppm, and the dimensional stability of the metal laminate was -0.12%.

Example 3 A polyimide film made of Dupont, Ka was used as a base film.
pton-ENZT (thickness: 50 μm) and thermoplastic polyimide PI-AU (thickness: 4)
μ) formed all-polyimide adhesive sheet and rolled copper foil BHY-02B-T (thickness 12
μm) The adhesive sheet thus obtained had a coefficient of thermal expansion of 18 ppm and the dimensional stability of the metal laminate was -0.01%.

Comparative Example 3 A base film made of a polyimide film made of Dupont, Ka
pton-ENZT (thickness: 50 μm) and thermoplastic polyimide PI-AU (thickness: 4)
μ) formed all-polyimide adhesive sheet and rolled copper foil BHY-02B-T (thickness 12
μm) The adhesive sheet thus obtained had a coefficient of thermal expansion of 18 ppm and the dimensional stability of the metal laminate was -0.01%.

[0020]

As described above, according to the present invention,
A metal laminate having excellent dimensional stability when absorbing moisture can be manufactured by a very simple method. As a result, there is no need to develop a new adhesive having a reduced coefficient of hygroscopic expansion, which has been a problem, and the cost of material development can be reduced. Furthermore, it is possible to manufacture a metal foil laminate in which dimensional stability at the time of moisture absorption is controlled only by the moisture absorption coefficient and the thickness of the base film and the adhesive with respect to various kinds of metal foils.

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Claims (1)

[Claims] 1. A flexible metal laminate, wherein an adhesive sheet having a coefficient of thermal expansion equal to that of a metal is interposed between metals to be bonded.