WO2006025684A1

WO2006025684A1 - Flexible copper-polyimide laminate and manufacturing method thereof

Info

Publication number: WO2006025684A1
Application number: PCT/KR2005/002865
Authority: WO
Inventors: Sang-Kyun Kim; Jeong-Yeol Moon; Tae-Hyung Kim; Seong-Geun Kim; Chang-Beom Chung; Jong-Min Park
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2004-09-03
Filing date: 2005-08-30
Publication date: 2006-03-09
Anticipated expiration: 2007-03-03
Also published as: TWI267442B; JP2008511475A; CN101010191A; TW200624251A; KR100591068B1; CN101010191B; KR20060021458A

Abstract

The present invention provides a flexible copper-polyimide laminate including a linear random block polyimide layer formed on the at least one side thereof, the linear random block polyimide layer comprising 0.25 to 90.25 mol.% of a repeating unit l represented by the formula 1, 0.25 to 90.25 mol.% of a repeating unit m represented by the formula 2, 0.25 to 90.25 mol.% of a repeating unit n represented by the formula 3, and 0.25 to 90.25 mol.% of a repeating unit o represented by the formula 4. The flexible copper-polyimide laminate having a polyimide layer is free from curls and excellent in dimensional stability, tensile property, folding endurance and resistance to flexural fatigue with low moisture content.

Description

Flexible Copper-Polyimide Laminate and Manufacturing Method thereof

Technical Field

The present invention relates to a flexible copper-polyimide laminate and a manufacturing method thereof. More specifically, the present invention relates to a flexible copper-polyimide laminate and a manufacturing method thereof, which flexible copper-polyimide laminate has a polyimide layer prepared by polymerizing a polyamic acid from two diamines and two dihydrides, coating the polyamic acid on a copper film and performing an imidization.

Background Art

Recently, the rapid growth of industry and technology has remarkably accelerated the development of electronic industries associated with mobile phones, PDP₅ etc. in a remarkable way, and miniaturization and flexibilization technologies have become vital and indispensable to the industry of electronic materials.

Many approaches to overcoming the problems with the use of adhesives in this field of industry have been proposed, only to solve the problem in degradation of incombustibility but cause curls and corrugations due to the difference in coefficient of linear expansion between metal and film. Polyimide generally has a high moisture content to cause many problems, and the resultant deterioration of the ductility of the adhesive leads to problems in regard to folding endurance and resistance to flexural fatigue. Many studies have been made in an attempt to solve those problems.

For example, annealing is carried out as a subsequent process to the steps of coating a polyamideimide solution and drying the coating so as to reduce curls after the coating and drying steps (Japanese Patent Laid-Open Publication No. 56-23,791). Other approaches include a method of manufacturing a laminate by coating a low- thermal-expansion resin on a metal film (Japanese Patent Laid-Open Publication Nos. 60- 157286 and 1989-244841); a method of manufacturing a laminate by coating a thermoplastic polyimide on the one side of a polyimide film and a heat-resistant polyimide on the other side (JP No. 1997-148695); and a method of manufacturing a laminate by coating a polyimide copolymer (JP No. 1993-245433).

With all these efforts, the individual method still has many problems.

As a method of attaching a polyimide on a metal film without using an adhesive, there has been proposed a method of coating a polyamic acid diluted with an organic solvent on a metal film and drying and imidizing the polyamic acid. However, this method causes curls due to the difference in rate of linear expansion between metal and polyimide.

The polyimide is excellent in heat resistance and electrical insulation property but poor in adhesiveness with metals, so an adhesive is used in some cases. But, the use of an adhesive may lead to high moisture content due to the introduction of moisture without guaranteeing a high heat resistance. To satisfy these properties, some methods involve synthesizing a polyimide copolymer, or mixing some polyamic acids and imidizing them, with no good results.

In some cases, the polyimide film is coated on a metal film several times, in which case there is an inconvenience of work. The flexible copper-clad laminate, which is much used in a repetitive driving portion, is required to have good properties such as dimensional stability, tensile property, folding endurance, resistance to flexural fatigue, and the like.

The conventional polyimide film is expensive to result in a high unit cost because of its complicated manufacturing process and also problematic in high moisture content. Such a flexible copper-clad laminate is primarily used in a repetitive driving portion and, for that reason, required to have good properties such as tensile property, folding endurance, resistance to flexural fatigue, dimensional stability, and the like.

In an attempt to solve the problems, the inventors of the present invention have found out that a copper-clad laminate manufactured by preparing a polyamic acid from two diamines and two dianhydrides by polymerization and imidization of the polymer solution satisfies the required properties through a relatively simple manufacturing process and lowers the price, thereby completing the present invention.

It is therefore an object of the present invention to provide a flexible copper-clad laminate without using an adhesive, which flexible copper-clad laminate is free from curls and excellent in dimensional stability, tensile property, folding endurance, resistance to flexural fatigue with low moisture content.

Disclosure of Invention

To achieve the above object of the present invention, there is provided a flexible copper-polyimide laminate including a linear random block polyimide layer formed on the at least one side thereof, the linear random block polyimide layer including 0.25 to 90.25 mol.% of a repeating unit /represented by the following formula 1, 0.25 to 90.25 mol.% of a repeating unit m represented by the following formula 2, 0.25 to 90.25 mol.% of a repeating unit n represented by the following formula 3, and 0.25 to 90.25 mol.% of a repeating unit o represented by the following formula 4: Formula 1

Formula 2

Formula 3

wherein Ar is,

Formula 4

wherein Ar is,

The present invention will be described in further details as follows. The present invention is directed to a flexible copper-clad laminate on which a polyimide layer is formed, the polyimide layer includes a linear random block copolymer of a repeating unit / represented by the formula 1, a repeating unit m represented by the formula 2, a repeating unit n represented by the formula 3, and a repeating unit o represented by the formula 4. The polyimide layer is formed by preparing a polyamic acid, coating the prepared polyamic acid on a copper film, and then imidizing the polyamic acid coating.

The formation of the polyimide layer of the present invention begins with the preparation of a polyamic acid from two diamines and two dianhydrides. The diamines

include 4,4'diaminophenylether (hereinafter, referred to as "ODA") and 4-amino-N-(4-

arninophenyl)benzamide (hereinafter, referred to as "DABA"). More specifically, the total

content of diamines includes x mol.% of OD A and 100- x mol.% of DABA, where x

satisfies 5.0< x <95.0.

The dianhydrides include pyromellitic dianliydride (hereinafter, referred to as

"PMDA") and 3,4,3',4'-biphenyl tetracarboxylic dianhydride (hereinafter, referred to as

"BPDA") or 3,4,3 ',4'-benzophenone tetracarboxylic dianhydride (hereinafter, referred to

as "BTDA"). More specifically, the total content of dianhydrides includes I mol.% of

PMDA and 100-ξ mol.% of BPDA or BTDA₅ wherein I satisfies 5. O≤ I ≤95.0.

The two diamines and the two dianhydrides participate in the preparation of a polyamic acid by a known polymerization method, where the reaction conditions of the diamines and the dianhydrides are not specifically limited.

The polyamic acid thus prepared is coated on a copper film and then subjected to imidization to form a random polyimide copolymer layer having a weight average molecular weight of 5,000 to 10,000,000 in the same manner as a known method for manufacturing a flexible copper-polyimide laminate. The random polyimide copolymer layer thus formed is a linear random block copolymer of 0.25 to 90.25 mol.% of a repeating unit / represented by the formula 1, 0.25 to 90.25 mol.% of a repeating unit m represented by the formula 2, 0.25 to 90.25 mol.% of a repeating unit n represented by the formula 3, and 0.25 to 90.25 mol.% of a repeating unit o represented by the formula 4.

The linear random polyimide copolymer thus obtained has a molecular weight of 5,000 to 10,000,000. It has the difficulty of film formation in the coating process when the molecular weight is less than 5,000, whereas the viscosity of the polyamic acid increases when the molecular weight exceeds 10,000,000.

More specifically, the polyamic acid is coated on a copper film with an applicator

or the like and dried at 50 to 400⁰C for 1 to 8 hours for amidization to form a polyamide

layer having a thickness of about 10 to 50 μm. Preferably, the copper film as used herein

has a thickness of, if not specifically limited to, 5 to 50 μm in the aspect of process.

The polyimide layer prepared only from DABA and PMDA is poor in adhesiveness and moisture content, whereas the polyimide layer only from ODA and BPDA has curls.

In an attempt to solve this problem, a mixture of the polyamic acid prepared from DABA/PMDA and the polyamic acid from ODA/BPDA is coated and imidized. But, this method causes an inconvenience of synthesizing polyamic acids at least twice.

For that reason, the present invention solves these problems by using all the two diamines and the two dianhydrides to prepare a polyamic acid by copolymerization and coating the polyamic acid to form a polyimide layer. The flexible copper-clad laminate having a polyimide layer thus obtained according to the present invention is free from curls with a low moisture content and excellent in dimensional stability, tensile property, folding endurance and resistance to flexural fatigue.

Particularly, the flexible copper-polyimide laminate can have good dimensional stability with a low moisture content and without curls irrespective of the thickness of the polyimide layer.

In the flexible copper-clad laminate of the present invention, inorganic particles may be dispersed in the polyimide layer. For the dispersion of inorganic particles, inorganic particles are added to the polyamic acid and dispersed, and the polyamic acid with inorganic particles dispersed therein is coated on a copper film and imidized.

Here, the inorganic particles have a particle size of 0.1 to 10 μm. The specific examples of the inorganic particles may include at least one selected from silica, quartz powder, titanium oxide, aluminum oxide, zircon powder, organo clay, magnesium oxide, calcium carbonate, or zinc oxide. Preferably, the inorganic particles are used in an amount of 0.001 to 10 parts by weight with respect to 100 parts by weight of the total solid content of the polyamic acid. With the content of the inorganic particles exceeding 10 parts by weight with respect to 100 parts by weight of the total solid content of the polyamic acid, the difficulty of dispersion occurs to cause not-dispersed particles, which act as a defective of the polyimide layer.

When larger than 10 μm, the inorganic particles stand out from the polyimide

layer to affect the appearance and physical properties of the laminate.

The dispersion of inorganic particles of an appropriate size increases the tensile modulus of the polyimide layer and makes it possible to provide a flexible copper- polyimide laminate excellent in tensile property, folding endurance and resistance to flexural fatigue.

Best Mode for Carrying out the Invention

Hereinafter, the present invention will be described in detail by way of the following examples, which are not intended to limit the scope of the present invention.

Synthesis Examples

According to the composition and the content as presented in Table 1, p-PDA or ODA, TPER and DABA as diamines and PMDA, BTDA or BPDA as dianhydrides were used to synthesize a polyamic acid by a known method. The unit of the content in Table 1 is mol.%. The diamines were sufficiently dissolved in a solvent (NMP, N-methyl pyrollidone) with stirring, and the dianhydrides were added to react with the diamines at a mole ratio of 1:1 and produce a polyamic acid. The polyamic acid thus prepared was identified by an elementary analysis(EA). The results of the elementary analysis on the polyamic acid products obtained in Synthesis Examples 1, 11, 15 and 20 are presented in Table 2. Table 1

Table 2

Examples 1 to 18

Each of the polyamic acids prepared in Synthesis Examples 1 to 18 was coated on

a 12μm-thickness copper(commercially available from Furukawa Company) with an

applicator and dried at 80⁰C for 2 hours, 200°C for 2 hours and 35O⁰C for one hour for

imidization to prepare a flexible copper-clad laminate having a 25μm-thickness polyimide

layer.

Comparative Examples 1 to 8 Each of the polyamic acids prepared in Synthesis Examples 19 to 26 was coated

on a 12μm-thickness copper(commercially available from Frukawa Company) with an

applicator and dried at 80⁰C for 2 hours, 200⁰C for 2 hours and 35O⁰C for one hour for

layer.

Examples 19 to 21

Based on 100 parts by weight of the polyamic acid solid content, 5.0 parts by weight of SiO₂ particles (Gasil 35M, supplied by Crossfϊeld Company) was added to each of the polyamic acids prepared in Synthesis Examples 2, 7 and 15, and dispersed for 5 minutes with a homogenizer (T25 basic, supplied by IKA Laboratechnik Company) at

9500 rpm.

The solution thus prepared was coated on a 12μm-thickness copper(commercially available from Frukawa Company) with an applicator and dried at 80°C for 2 hours, 200°

C for 2 hours and 350°C for one hour for imidization to prepare a flexible copper-

polyimide laminate having a 25μm-thickness polyimide layer.

Examples 22 to 24

Based on 100 parts by weight of the polyamic acid solid content, 5.0 parts by weight of TiO₂ particles (R700, supplied by DuPont Company) was added to each of the polyamic acids prepared in Synthesis Examples 2, 7 and 15, and dispersed for 5 minutes with a homogenizer (T25 basic, supplied by IKA Laboratechnik Company) at 9500 rpm.

The solution thus prepared was coated on a 12μm-thickness copper(commercially

available from Furukawa Company) with an applicator and dried at 80 ⁰C for 2 hours,

200 ⁰C for 2 hours and 350 ⁰C for one hour for imidization to prepare a flexible copper-

clad laminate having a 25μm-thickness polyimide layer.

Each of the flexible copper-clad laminates manufactured in Examples and Comparative Examples was analyzed in regard to curl, moisture content, dimensional stability, tensile property, folding endurance, resistance to flexural fatigue, and weight average molecular weight according to the methods of Table 3. The measurement results are presented in Table 4.

Table 3

Table 4

As can be seen from Table 4, the flexible copper-polyimide laminate of the present invention manufactured by coating a polyamic acid prepared from two diamines and two dianhydrides on a copper film and imidizing it is free from curls and excellent in tensile property, folding endurance, resistance to flexural fatigue with good moisture content and high dimensional stability, compared with that of Comparative Example 5 using a polyamic acid prepared from ODA as a diamine and BTDA as a dianhydride and those of Comparative Examples 3, 6 and 7 using two diamines and two dianhydrides other than those used in the present invention. In particular, the use of inorganic particles dispersed in the polyimide layer as shown in Examples 19 to 24 much enhances tensile property, folding endurance and resistance to flexural fatigue.

As described above, the flexible copper-polyimide laminate having a polyimide layer as formed by preparing a linear random block polyamic acid from ODA and DABA as diamines and PMDA and BPDA/BTDA as dianhydrides, coating the solution on a copper and imidizing it is free from curls and excellent in dimensional stability, tensile property folding endurance and resistance to flexural fatigue with low moisture content..

While this invention has been described in connection with the embodiments, it is to be understood to those skilled in the art that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements.

Claims

What is claimed is:

1. A flexible copper-polyimide laminate comprising a linear random block polyimide layer formed on the at least one side thereof, the linear random block polyimide layer comprising 0.25 to 90.25 mol.% of a repeating unit / represented by the following formula 1, 0.25 to 90.25 mol.% of a repeating unit m represented by the following formula 2, 0.25 to 90.25 mol.% of a repeating unit n represented by the following formula 3, and 0.25 to 90.25 mol.% of a repeating unit o represented by the following formula 4: Formula 1

Formula 2

Formula 3

w

herein Ar is, or Formula 4

wherein Ar is,

, or

2. The flexible copper-polyimide laminate as claimed in claim 1, wherein the linear random block polyimide layer includes inorganic particles dispersed therein.

3. The flexible copper-polyimide laminate as claimed in claim 2, wherein the inorganic particles include at least one selected from silica, quartz powder, titanium oxide, aluminum oxide, zircon powder, organo clay, magnesium oxide, calcium carbonate,

or zinc oxide, the inorganic particles having a particle size of 0.1 to 10 μm.

4. A method for manufacturing a flexible copper-polyimide laminate, which method includes the steps of polymerizing a diamine and a dianhydride to prepare a polyamic acid, coating the polyamic acid on a copper, and performing an imidization to form a polyimide layer,

the diamine comprising χmol.% of 4,4' -diaminophenyl ether and 100-χ mol.%

of 4-amino-N-(4-aminophenyl)benzamide, wherein X satisfies 5.0≤χ≤95.0,

the dianhydride comprising % mol.% of pyromellitic dianhydride and 100-ξ

mol.% of 3,4,3 ',4'-biphenyl tetracarboxylic dianhydride or 3,4,3 ',4'-benzophenone

tetracarboxylic dianhydride, wherein \ satisfies 5.0≤ I ≤95.0,

the polyimide layer comprising 0.25 to 90.25 mol.% of a repeating unit / represented by the following formula 1, 0.25 to 90.25 mol.% of a repeating unit m represented by the following formula 2, 0.25 to 90.25 mol.% of a repeating unit n represented by the following formula 3, and 0.25 to 90.25 mol.% of a repeating unit o represented by the following formula 4: Formula 1

Formula 2

Formula 3

wherein Ar is,

Formula 4

wherein Ar is, or

5. The method as claimed in claim 4, further comprising the step of dispersing inorganic particles in the polyamic acid before the steps of preparing the polyamic acid and coating the polyamic acid on the copper.

6. The method as claimed in claim 5, wherein the inorganic particles include at least one selected from silica, quartz powder, titanium oxide, aluminum oxide, zircon powder, organo clay, magnesium oxide, calcium carbonate, or zinc oxide, the inorganic particles having a particle size of 0.1 to 10 μm, the inorganic particles being dispersed in an amount of 0.001 to 10 parts by weight with respect to 100 parts by weight of the total solid content of the polyamic acid.