JPH02122926A - Flexible copper-clad board - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of a heat resistance covering material and copper foil formed after circuit formation by fixing a metallic simple substance, the oxide thereby or the alloy thereof on the surface being out of contact with the heat resistance polymeric film layer of one copper foil layer. CONSTITUTION:A metallic simple substance, the oxide thereof or the alloy thereof is fixed on the surface being out of the heat resistance polymeric film layer of at least one copper foil layer. Particularly, the polymeric film layer is a heat resistance film layer, and the metallic simple substance, the oxide thereof or the alloy thereof is a kind or two kinds or more selected from copper simple substance, copper oxide, nickel-copper alloy, and zinc-copper alloy. Namely, a specific surface treatment is preferably performed on the surface being out of contact with the resistance polymeric film between two copper foil surfaces, thereby considerably improving the adhesive strength of a heat resistance covering material with copper foil formed after circuit formation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to flexible copper-clad laminates that are becoming popular in the electronics industry.
Clad Lam1nate (hereinafter also abbreviated as FCL)
And, flexible printed wiring board (Flexible)
e Pr1ntedC4rcuit (hereinafter also abbreviated as FPC).

[Prior Art] FCL is mainly used as a base material for flexible printed wiring boards, but is also used for surface heating elements, electromagnetic shielding materials, flat cables, packaging materials, and the like.

In recent years, the use of FCL as a base material for printed wiring boards has increased because case necks in which printed wiring boards are housed have become more compact.

Among these FCLs, FCLs in which the heat-resistant polymer base film and copper foil are directly bonded without using adhesives are
F made by pasting copper foil and heat-resistant polymer together using adhesive
It has extremely superior heat resistance compared to CL.

This FCL is obtained by forming a heat-resistant polymer on a copper foil to obtain an FCL consisting of a copper foil and a heat-resistant polymer base film, and then a circuit is formed thereon to form a flexible printed wiring board (FPC).

For this FPC, a polymer film called a cover material is often formed on the circuit to protect the circuit.The cover material is made by pasting a polymer film with the FPC using a heat press or the like, or by using a polymer-containing material. It is formed by applying varnish onto the FPC and drying it. Since the FPC manufactured from adhesive-free FCL has excellent heat resistance as described above, it is necessary that this cover material also has excellent heat resistance. However, the heat-resistant cover materials that have been considered so far have insufficient adhesion to copper foil, and have not been put into practical use.

[Problem to be solved by the invention] Copper F! FCL, which has a heat-resistant polymer base film directly formed on top and does not have an adhesive layer, has the advantage of heat resistance due to the presence of an adhesive layer, which is made by laminating a copper foil and a heat-resistant polymer base film together using an adhesive. However, the adhesive strength between the copper foil and the heat-resistant cover material that is fixed to protect the circuit after the circuit is formed does not reach the required level.

In view of this situation, the present invention manufactures an FPC with excellent adhesive strength between the heat-resistant cover material and the copper foil formed after circuit formation, while maintaining the situation where the excellent properties of the heat-resistant polymer are utilized. The purpose of this invention is to provide an FCL that can be passed through the FCL, and such an FCL is extremely useful in industry, particularly in the electronics industry.

[Means for Solving the Problems] That is, the present invention provides a flexible copper-clad laminate having copper foil on at least one of the polymer film layer and the polymer film layer, wherein the heat resistance of at least one of the copper foil layers is A flexible copper-clad laminate in which an elemental metal, its oxide, or its alloy is fixed to the surface not in contact with a heat-resistant polymer film layer, and in particular, the polymer film layer is a heat-resistant polymer film layer. A laminate, and especially a laminate in which the elemental metal, its oxide, or its alloy is one or more selected from elemental copper, copper oxide, nickel-copper alloy, and zinc-copper alloy, Further, it is a flexible printed wiring board in which a circuit is formed on the copper foil layer of the flexible copper-clad laminate thus obtained, and a circuit is formed on the copper foil layer of the flexible copper-clad laminate thus obtained. This is a flexible printed wiring board in which a circuit is formed and then a cover material made of a heat-resistant polymer is formed on the circuit surface.

That is, the gist of the present invention is, in short, to perform a specific surface treatment on the two surfaces of the copper foil, preferably the surface that is not in contact with the heat-resistant polymer film (base film), so that the circuit formed after the circuit is formed is The present invention provides FCL and FPC in which the adhesive strength between the heat-resistant cover material and the copper foil can be significantly improved, and the above-mentioned problems have been solved.

The present invention will be explained in detail below.

The polymeric film layer used as a base film in the present invention is preferably a heat-resistant polymeric base film, as described in detail below, but as can be easily understood, from the basic concept of the present invention However, it is not necessarily limited to heat-resistant polymers.

The present invention is directed to a flexible copper-clad laminate having copper foil on at least one of the polymer film layers. r! Copper alone, copper oxide, nickel-m alloy, zinc-copper alloy, etc. are formed on the foil. When a heat-resistant cover material is formed on this surface-treated copper foil, the adhesion between the copper foil and the heat-resistant cover material is excellent, and it can withstand harsh conditions such as solder immersion, high-temperature continuous processing, and high-temperature high-temperature processing. The present inventors have discovered that it continues to maintain high peel strength even after aging.

In the present invention, the thickness of the copper foil can be arbitrarily selected, but is usually within the range of 10 to 100 μm, preferably 1
It is within the range of 0 to 50 μm.

Furthermore, in the present invention, a surface treatment is performed on the copper foil in order to improve the adhesion between the heat-resistant cover material formed after circuit formation and the copper foil, but preferably the heat-resistant polymer as a base is It is preferable that the adhesion between the heat-resistant polymer base film and the copper foil is also high. Therefore, the surface of the copper foil that is directly bonded to the heat-resistant polymer base film may also be surface-treated with copper alone, copper oxide, nickel-zinc alloy, zinc-copper alloy, etc. Among these surface treatments, nickel-copper alloy treatment is particularly preferred in terms of its heat resistance and moisture resistance.

In the present invention, there are no particular limitations on the method of forming a single metal, its oxide, or its alloy on a copper foil layer, but metals or alloys may be formed on a copper foil by electrolytic plating or electroless plating, or by vacuum plating. It can be formed by vapor deposition or sputtering. The thickness of the metal or alloy produced at this time is preferably 0.1 to 2 μm. If it is less than 0.1 μm, the adhesive strength and heat resistance with the heat-resistant cover material will be insufficient, and if it exceeds 2 μm, the surface treatment This is undesirable because problems such as layer drop-off, deterioration of electrical properties, and residual surface treatment layer after copper etching occur.

Furthermore, after this surface treatment, it is also preferable to perform various known rust prevention treatments such as zinc oxide treatment, chromium oxide treatment, zinc-chromate treatment, etc. For example, after nickel-copper alloy treatment, zinc-chromate treatment is performed to prevent rust. Providing this layer can further improve the durability of the nickel-copper alloy treated layer.

In addition, rust prevention treatments such as zinc oxide treatment, zinc-chromate treatment, and chromium oxide treatment are applied without surface treatment of one or more selected from copper alone, copper oxide, nickel-copper alloy, and zinc-copper alloy. The peel strength of a polymer cover material formed on copper foil is not practically sufficient for FCL, and the deterioration is particularly large under high temperature and high temperature and high humidity conditions, resulting in poor durability. I understand.

Furthermore, the heat-resistant polymer base 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 heterocycle other than an imide bond. , polyimide, polyamideimide, polyhydantoin, polyparabanic acid, polyoxazinedione, etc. Heat-resistant polymers having heterocycles other than imide bonds include polybenzimidazole, polyimidazopyrrolone, triazine derivatives, etc.

In this invention, a film of a heat-resistant polymer having an imide bond is preferable, and more preferably a film of polyimide,
These are films of what is called polyamideimide, and these may be made into composite films.

Typical polyimides are Its structural formula (anti- unit) is shown below.

In addition, as polyamideimide, 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 containing repeating units represented by structural formula (3) or (4) are also suitable. .

In the above structural formula, χ is o, so, , s, C01
CHz, C(CHsh, C(CFz)z or a direct bond.

Examples of aromatic diamines represented by the above structural formula include 4,4°-diaminodiphenylmethane, 4゜4゛-diaminodiphenyl-thyl, 4.4°-diaminodiphenyl sulfone, 3,3゛-diamino diphenylmethane, 3
．． Examples include 3°-diaminodiphenyl ether and 33″-diaminodiphenyl sulfone.

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

The FCL obtained in the present invention is often formed with a circuit and becomes an FPC as specified in the present invention. However, as the heat-resistant cover material formed after the circuit is formed, the following are preferable. The heat-resistant cover material layer suitable for the FCL obtained in is made of a heat-resistant polymer having an imide bond and/or a heat-resistant polymer having a heterocycle other than an imide bond. As the polymer having an imide bond, polyimide , polyamideimide, polyetherimide, polyhydantoin, polyparabanic acid, polyoxazinedione, etc. These polymers may be modified with bismaleimide, epoxy resin, etc., and can also be used as heat-resistant polymers with heterocycles other than imide bonds. Examples include polybenzimidazole, polyimidazopyrrolone, and triazine derivatives.

Next, the present invention will be further explained by showing examples.

Example 1 (1) Synthesis of amic acid varnish 421 g of 4,4''-diaminodiphenyl ether was added in a container equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube.
(2.1 mol), N-methylpyrrolidone 4000Ii
dissolved in 458 g (2.1 mol) of pyromellitic dianhydride was added to this solution under a nitrogen atmosphere, and the mixture was reacted at room temperature for 24 hours.

The logarithmic viscosity of the polyamic acid solution thus obtained was 1.8.
It was dl/g.

This polyamic acid solution was diluted with N-methylpyrrolidone for 16
% and the rotational viscosity was adjusted to 100.0OOcps.

(2) Creation of FCL The polyamic acid solution obtained in (1) is applied to electrolytic copper foil (manufactured by Mitsui Mining & Mining Co., Ltd., 3EC-DT, thickness 35 μm), heated and dried at 135°C for 5 minutes, then at 180°C for 4 minutes, and then heated in a nitrogen atmosphere at 250°C for 3 minutes.
A flexible substrate made of copper foil and polyimide was obtained by heating for 5 minutes in a nitrogen atmosphere at 350°C.

The thickness of the polyimide layer of the flexible substrate thus obtained was 35 μm.

(3) Preparation of heat-resistant cover material In a container equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube, 584 g (2.0 mol) of 1,3-bis(3-aminophenoxy)benzene was added to N,N-dimethyl Inserted into 3700-mL acetamide, 644 g (2.0 mol) of 33°, 4.4°-benzophenone tetracarboxylic dianhydride was added in 4 portions at room temperature under a nitrogen atmosphere while being careful not to increase the solution temperature. , and allowed to react at room temperature for about 24 hours.

The logarithmic viscosity of the polyamic acid solution thus obtained is 1,
It was 2 a/g.

10 g of bismaleimide-3 (4,4° bismaleimide diphenylmethane) manufactured by Ciba Geigy was added to this polyamic acid solution ti, loOg and stirred for 2 hours.

After casting this polyamic acid-bismaleimide solution onto a glass substrate, it was heated at 100°C and 1200°C for 3
Each film was heated at 00°C for 1 hour to obtain a bismaleimide-modified polyimide film with a thickness of 20 μm. The glass transition temperature of this heat-resistant cover material was 153°C.

(4) Formation of heat-resistant cover film on FCL (2)
The heat-resistant cover material obtained in (3) was placed on the copper foil surface of the FCL obtained in (3), and the heat-resistant cover material obtained in (3) was
A heat-resistant cover material was formed on the FCL by pressing for a minute.

The peel strength between the cover material and the copper foil of the FCL with the cover material obtained in this way was 0°95Kg/c.
It was "m".

Comparative Example 1 An electrolytic copper foil (manufactured by Mitsui Metal Mining Co., Ltd., 3EC) which was subjected to copper plating treatment on only one side as the copper foil in Example 1.
An FCL with a cover material was obtained by carrying out the same operation as in Example 1, except that a material (with a thickness of 35 μm) was used.

The peel strength between the cover material and the copper foil of the FCL with the cover material obtained in this way is 0.10 kg/c.
+s'', which of course shows that the peel strength between the FPC formed from 33 F CL, the cover material and the copper foil is basically the same.

[Effects of the invention] An elemental metal such as copper, nickel, or chromium, or an oxide thereof or an alloy thereof is fixed to the surface of the copper foil layer proposed by the present invention that is not in contact with the heat-resistant polymer base film layer. The flexible copper-clad laminate has increased adhesive strength between the heat-resistant polymer film and the copper foil, and has a peel strength of 0.7 kg/cm or more. It goes without saying that a peeling strength of 0.7 kg/Ω is considered sufficient for boat fishing, and the upper limit is not particularly stipulated; the stronger the better. It is.

This type of FCL has good heat resistance because it does not have an adhesive layer, and due to the effects of single metals such as copper, nickel, and chromium, or their alloys, oxides, etc., after FCL is formed into a circuit. It has very good adhesion between the formed FPC and the heat-resistant cover material, and its thermal deterioration resistance.

As described above, according to the present invention, it is possible to provide a flexible copper-clad laminate and a flexible printed wiring board with excellent characteristics.

Claims (5)

[Claims] 1. In a flexible copper-clad laminate having a polymer film layer and a copper foil on at least one of the polymer film layers, a single metal or its Flexible copper-clad laminate with fixed oxide or its alloy. 2. A laminate according to claim 1, wherein the polymer film layer is a heat-resistant polymer film layer. 3. 2. The laminate according to claim 1, wherein the elemental metal, its oxide, or its alloy is one or more selected from elemental copper, copper oxide, nickel-copper alloy, and zinc-copper alloy. 4. A flexible printed wiring board obtained by forming a circuit on the copper foil layer of the flexible copper-clad laminate obtained in claim 1. 5. A flexible printed wiring board obtained by forming a circuit on the copper foil layer of the flexible copper-clad laminate obtained in claim 1, and then forming a cover material made of a heat-resistant polymer on the circuit surface.