JPH02131936A - Flexible copper-clad laminated board - Google Patents

Abstract

PURPOSE:To obtain a flexible copper-clad laminated board having excellent heat resistance, high bending resistance, high peeling strength and excellent body strength by forming a film of polyimide generated by reacting specific aromatic tetracarboxylic acid dianhydride with aromatic primary diamine on a copper foil. CONSTITUTION:Aromatic primary diamine represented by a formula 2a and aromatic primary diamine represented by a formula 2b are mixed at the ratio of 90-40:10-60 of equivalent ratio, a copper foil is coated with organic solvent solution of polyamide acid generated by reacting it with aromatic tetracarboxylic acid anhydride represented by a formula 1, then heated, dried, dehydrated to form a polyimide film layer on the foil. An operation for coating the foil with the solution is desirably conducted by casting. More specifically, polyamide acid solution is discharged from a film forming slit to the surface of the foil to form a coating film layer having a uniform thickness. The thickness of the layer is so adjusted as to obtain 1-1000mum of finally obtained polyimide film layer.

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 Laminate (hereinafter abbreviated as FCL).

[Prior Art 1 FCL is mainly used as a base material for flexible printed wiring boards, but is also used in other materials such as TM wave shielding materials, surface heating elements, flatbed cables, and packaging materials.

In recent years, the use of FCL as a base material for printed wiring boards has increased because cases in which printed wiring boards are housed have become more compact. Such FCLs have conventionally been manufactured by laminating a heat-resistant polymer film to a copper foil using an adhesive made of an organic polymer, usually with a thickness of 5 μm or more. However, FCL using this adhesive cannot take full advantage of the excellent properties of the heat-resistant polymer film because the properties of the adhesive are insufficient, and there are problems in particular in terms of heat resistance. Ta.

To this end, methods have been studied to create an FCL in which a heat-resistant polymer film and W4 foil are directly adhered to each other without using an adhesive. For example, U.S. Pat. No. 3,179,634, U.S. Pat. No. 862, No. 58-190,091, No. 59-162.044, etc. However, adhesive-free FC using these methods
L indicates that the adhesive strength between the heat-resistant polymer film and the copper foil is insufficient, or even if the adhesive strength is sufficient, the strength is unstable, and the adhesive strength deteriorates significantly in a high-temperature atmosphere. There was a drawback. In particular, among heat-resistant polymers, it is difficult to obtain stable and high adhesive strength with polyimide and polyamide-imide due to various reasons. Furthermore, U.S. Patent No. 3,736,170, Japanese Patent Application Laid-open No. 1983-
162,044, in the case of polyimides insoluble in phenolic solvents, which are suitable as heat-resistant polymers for FCLs, the tension between the heat-resistant polymer film and the copper foil is If the peel strength is not very high, the bending stress is large, or the circuit width is narrow, the adhesive strength cannot be said to be sufficient from the viewpoint of circuit reliability.

[The tiBl polyimide film to be solved by the invention is an epoxy resin with a thickness of 5μ or more,
FCL laminated to wA foil via an adhesive layer made of an organic polymer such as acrylic resin has already been proposed, but existing FCLs using adhesives made of such organic polymers have limited characteristics. has not reached the required level in many respects. In addition, FCL without an adhesive layer is superior to PCL with an adhesive layer in terms of heat resistance, but the balance of adhesive strength, strength of the heat-resistant polymer film, folding durability, etc. The obtained FCL has not yet been put into practical use.

In view of this situation, the present invention provides FCL with excellent properties such as high heat resistance, strong elasticity, excellent bending durability, high peel strength, and appropriate coefficient of thermal expansion. FCL is extremely useful in industry, especially in the electronics industry.

[Means for Solving the Problems] In other words, the present invention provides a flexible copper film in which a polyimide film produced by reacting an aromatic tetracarboxylic dianhydride and an aromatic primary diamine is formed on a copper foil. In stretched laminates,
A flexible copper-clad f characterized in that the aromatic tetracarboxylic acid anhydride is a mixture of the following formula (1) and the aromatic primary diamine is a mixture of the following formulas (2a) and (2b).
IN plate, and {2ht-@-NHz (2a)} 82N-o-0-@-G-0-@-NH2《2b》 (2a) An aromatic primary diamine represented by 2 and (2b)
The equivalent ratio with the aromatic primary diamine represented by the formula is 90~
40: It is a flexible copper-clad laminate with a rating of 10 to 60, and the manufacturing method for the flexible copper-clad laminate specified above is (
2a) The aromatic primary diamine represented by 2 and the aromatic primary diamine represented by the formula (2b) are mixed at a mixing ratio of 90 to 40.
: After coating a copper foil with an organic solvent solution of polyamic acid produced by mixing at a ratio of 10 to 60 and reacting with an aromatic tetracarboxylic acid anhydride, heating, drying,
This is a method for producing a flexible copper-clad laminate, which is characterized by forming a polyimide film layer on copper foil by dehydration. That is, the gist of the present invention is that polyimide is usually synthesized using tetracarboxylic dianhydride and diamine as raw materials, but in the present invention, polyimide is synthesized using 3 as the tetracarboxylic dianhydride (1).
, 3°, 4,4°-biphenyltetracarboxylic dianhydride, and the diamines are phenylenediamine represented by (2a) and 4,4″-bis(3-aminophenoxy)biphenyl represented by (2b). are preferably mixed at an equivalent ratio of 90 to 40:10 to 60.The above tetracarboxylic dianhydride and diamine react in an organic solvent to form polyamic acid, which is then deposited on the copper foil. After being coated, it is heated, dried, and dehydrated to form a flexible copper-clad laminate.The polyamic acid produced in the present invention is not particularly limited, but preferably has a 4.4° -bis(3-aminophenoxy)biphenyl in an equivalent ratio of 90 to 40: 10 to 60, preferably 80 to 60: 20 to 40, and the temperature is generally -2
0°C to 100°C1 Preferably, after mixing at 0°C to 40°C, the boiling point of the 3,3°,4.4'-biphenyltetracarboxylic acid anhydride and the solvent used at -20°C or higher. (Method 1) or react with paraphenylenediamine at a temperature range of 3.3".
4゜-biphenyltetracarboxylic anhydride and -20
at a temperature range of 0°C or above and below the boiling point of the solvent used, preferably 0°C to 40°C, for 10 minutes or more, preferably 1
Polyamic acid (A) produced by reaction for ~48 hours
4, under the same conditions and method as polyamic acid (A).
4°-bis(3-aminophenoxy)biphenyl and 3.
3゜． Polyamic acid (B) produced by reacting with 4,4°-biphenyltetracarboxylic acid anhydride is mixed in an equivalent ratio of 90 to 40: 10 to 60, preferably 80 to 60: 20 to 40 in terms of diamine. (Method 2)
It can be obtained by The concentration of polyamic acid in the polyamic acid solution obtained as described above is preferably 5 to 50%. Among these methods, from the viewpoint of mechanical properties, etc., particularly preferable results are obtained when manufacturing using method 1. Among the diamines, when the equivalent ratio of 4,4'-bis(3-aminophenoxy)biphenyl exceeds 60%, the resulting polyimide has strong thermoplasticity. The film may be easily damaged if it comes into direct contact with temperatures (350°C) or deformed if it is floated in a high-temperature solder bath (280°C or higher). It has poor operability when forming a circuit and connecting it to a connector, etc., making it difficult to handle it as a printed wiring board.
In addition, if the equivalent ratio of 4,4゜bis(3-aminophenoxy)biphenyl is less than 10%, the adhesive strength of the produced polyimide film to the copper foil is low, and the circuit of the flexible printed circuit can be easily removed from the film. The drawback is that it peels off easily and cannot be put to practical use. polymerization,
Examples of organic solvents used during coating include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 1
．． 3-dimethyl-2=imidazolidinone, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, dimethylsulfoxide, pyridine, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, N-methylprolactam, Tetrahydrofuran, monodioxane, p-dioxane, ■,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis-[2-(
2-methoxyethoxy)ethyl}ether, etc.

When coating a 7 volume solution of polyamic acid on W4 foil, the polyamic acid solution can be coated as it is, diluted with the above-mentioned organic solvent, or heated for 10 minutes or more at a temperature below the boiling point of the solvent. 5～
Contains 40% by weight, particularly preferably 10 to 30% by weight,
and the logarithmic viscosity is 0.5 to 6a/g (35°c,'a
The physical properties of the polyimide produced and the polyamide Preferable from the viewpoint of acid coating suitability and economic efficiency in the drying process. A simple method is to measure the viscosity using a rotational viscometer at the time of application;
It is 0~l00000cps. The operation of coating the copper foil with the polyamic acid solution is preferably carried out by casting. Specifically, the polyamic acid solution is sprayed onto the surface of the 1i1 foil from a film-forming slit to coat the copper foil with a uniform thickness. Form a membrane layer. The thickness of the coating Wj4Ji is based on the thickness of the final polyimide film layer.
The thickness is adjusted to approximately 1000 μm. As other coating means, known means such as a doctor blade, roll coater, knife coater, comma coater, flow coater, etc. can be used. Both rolled copper foil and electrolytic W4 foil can be used as W4 foil, but their thickness is usually about 1μII to 100μ. In addition, in order to increase the adhesive strength between copper foil and polyimide, metals, alloys, or oxides thereof, such as simple copper, copper oxide, Ninokeru copper alloy, zinc-copper alloy, etc., may be formed on the surface of w4Fg. It is also preferable to treat the surface of the copper foil with a cambling agent, such as an aminosilane-based camping agent, an epoxysilane-based coupling agent, a mercabutane-based coupling agent, or the like. Furthermore, in order to prevent rust on the surface of the copper foil, it is also preferable to subject the copper foil to zinc oxide treatment, zinc-chromate treatment, chromium oxide treatment, or the like.

The polyamic acid coating layer prepared as described above is then heated to perform solvent removal and dehydration condensation reactions. This operation can be performed under any conditions such as normal pressure, reduced pressure, or increased pressure. Further, as a heating method, any of hot air, infrared rays, far infrared rays, etc. may be used, and it is also possible to use them in combination. During these desolvation and dehydration processes, if the copper foil surface is exposed to temperatures higher than the oxidation temperature, the W4 foil surface will oxidize, resulting in a decline in the mechanical properties, electrical properties, and adhesive properties of the W4 foil. The desolvation and dehydration process may be performed using nitrogen, helium,
It is particularly preferable to carry out the process in an inert gas such as neon or argon in order to prevent oxidation of the copper foil surface. Here, in an inert gas atmosphere means that the surface of the copper foil is in a gas atmosphere in which it does not substantially undergo an oxidation reaction that adversely affects electrical properties or adhesive strength, etc. during heating for a predetermined period of time. Although it depends on the temperature, it usually means a gas atmosphere with an oxygen content of 10% or less, preferably 5% or less, and more preferably 1% or less. As described above, the FCL proposed in the present invention has good heat resistance because it does not contain adhesive, and has excellent bending durability, peel strength, stiffness, etc. due to the use of excellent polyimide. It has excellent characteristics. [Example] Next, the present invention will be further explained with reference to Examples. EXAMPLE In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube, 151 g (1.4 mol) of paraphenylenediamine, the diamine (2a), and 4.
221 g of 4'-(3-aminophenoxy)biphenyl (
0.6 mol), N,N-dimethylformamide 350
Dissolved in 0ad. Add 3 to this solution under nitrogen atmosphere.
．． 588 g (2.0 mol) of 3'',4,4゜-biphenyltetracarboxylic dianhydride was added and allowed to react at room temperature for 24 hours. The logarithmic viscosity of the polyamic acid solution thus obtained was 1.
It was 8 a/g. This polyamic acid solution was diluted with dimethylformamide.
It was diluted to 8% and the rotational viscosity was adjusted to 10,000 cps. This polyamic acid solution was uniformly cast onto electrolytic W4 foil (manufactured by Fukuda Metal Foil and Powder Co., Ltd., CF-T8, thickness 35 μm), heated at 135°C for 5 minutes, and then heated at 180°C.
After drying by heating for 4 minutes at 250° C. in a nitrogen atmosphere, it was further heated for 5 minutes in a nitrogen atmosphere at 350° C. to obtain a flexible copper-clad laminate with a polyimide film formed on the copper foil. Ta. The thickness of the polyimide layer of the flexible substrate thus obtained was 30 μm.

The characteristics of this flexible substrate were as shown in Table 1.

Comparative Example 1 In Example, a polyamic acid solution was synthesized using only 216 g (2.0 mol) of paraphenylene diamine as the diamine. The polyamic acid solution thus synthesized was adjusted to a concentration of 18% and a rotational viscosity of 10,000 cps.

The polyamic acid solution thus obtained was treated in the same manner as in the example.
A flexible copper-clad laminate in which a polyimide film was formed on the copper foil was obtained by uniformly casting and heating the electrolytic copper foil.

The thickness of the polyimide layer of the flexible substrate thus obtained was 30 μm. The characteristics of this flexible substrate were as shown in Table 1. Comparative Example 2 In Example, a polyamic acid solution was synthesized using only 736 g (2.0 mol) of 4.4'-(3-aminophenoxy)biphenyl as the diamine. The polyamic acid solution synthesized in this way has a concentration of 18% and a rotational viscosity of 10,000.
Adjusted to cps.

The polyamic acid solution thus obtained was treated in the same manner as in the example.
Electrolysis: 1 t: Cast coating was applied uniformly onto I foil and heated to obtain a flexible copper-clad laminate with a polyimide film formed on the foil. The thickness of the polyimide layer of the flexible substrate thus obtained was 30 μm. The characteristics of this flexible substrate were as shown in Table 1. The characteristics of the example and comparative example are compared next. Comparative Example 1 has no problem with heat resistance, but it has low peel strength and poor folding durability, so it cannot be said that it has sufficient performance as a flexible substrate, and Comparative Example 2 has no problem with peel strength. Although it has high strength and no problems with bending durability, it has the disadvantage of poor hand solderability. On the other hand, the examples have sufficient peel strength, folding durability, and hand soldering resistance to withstand use. In addition, the tensile modulus of the film can also be called "hardness", but for flexible substrates, it is easy to use a tensile modulus of about 300 to 450 kg/ms, Comparative Example 1 is too hard, Comparative Example 2 is too soft, The substrate of this example has just the right "hardness" for practical use.

[Effects of the Invention] The FCL proposed by the present invention, in which a polyimide film is formed on a copper foil, has excellent heat resistance because it does not use an adhesive layer, has good folding durability, and has high peel strength. It is a flexible copper-clad laminate with excellent characteristics of high strength and stiffness, and such a flexible steel-clad laminate is considered to be a useful material that can be gripped, especially when used as a flexible printed wiring board. Can be done.

Claims (3)

[Claims] 1. In a flexible copper-clad laminate in which a polyimide film produced by reacting an aromatic tetracarboxylic dianhydride and an aromatic primary diamine is formed on a copper foil, the aromatic tetracarboxylic anhydride is (1), the aromatic primary diamine is represented by the following formulas (2a) and (2b).
) A flexible copper-clad laminate characterized by being a mixture of the formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2a) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2b) 2. In claim 1, the equivalent ratio of the aromatic primary diamine represented by the formula (2a) to the aromatic primary diamine represented by the formula (2b) is 90-40:10-60. Flexible copper clad laminate. 3. In the method for manufacturing a flexible copper-clad laminate as defined in claim 1, the aromatic primary diamine represented by the formula (2a) and the aromatic primary diamine represented by the formula (2b) are mixed in an equivalent ratio. After coating a copper foil with an organic solvent solution of polyamic acid produced by mixing in a ratio of 90 to 40:10 to 60 and reacting with aromatic tetracarboxylic acid anhydride,
A method for producing a flexible copper-clad laminate, which comprises forming a polyimide film layer on copper foil by heating, drying, and dehydrating.