WO2010008214A2

WO2010008214A2 - Copper foil for printed circuit board, method of preparing the same, and flexible copper clad laminate using polyamic acid precursor and copper foil

Info

Publication number: WO2010008214A2
Application number: PCT/KR2009/003914
Authority: WO
Inventors: Jong Ho Ryu; Jong Chan Won; Yong Seok Kim; Hyun Min Jung; Jin Young Park
Original assignee: Iljin Copper Foil Co Ltd
Current assignee: Iljin Copper Foil Co Ltd
Priority date: 2008-07-18
Filing date: 2009-07-16
Publication date: 2010-01-21
Anticipated expiration: 2011-01-18
Also published as: KR20100009263A; WO2010008214A3; TWI391531B; KR101475839B1; TW201009119A

Abstract

Provided is a surface-treated copper foil for a printed circuit board (PCB), including an antirust layer formed on a copper foil and a surface treatment film formed on the antirust layer, wherein the surface treatment film includes at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4, or hydrolysates of the silane-based compounds: wherein R₁, R₂, and R₃ are each independently a C₁-C₃ alkyl group and R₄ and R₅ are each independently hydrogen or a C₁-C₅ alkyl group.

Description

COPPER FOIL FOR PRINTED CIRCUIT BOARD, METHOD OF PREPARING THE SAME, AND FLEXIBLE COPPER CLAD LAMINATE USING POLYAMIC ACID PRECURSOR AND COPPER FOIL

Technical Field

The present invention relates to a surface-treated copper foil for a printed circuit board (PCB), a method of preparing the copper foil, and a flexible copper clad laminate (FCCL) including the copper foil, and more particularly, to a surface-treated copper foil for a PCB on which a surface treatment film including a silane-based compound or hydrolysate of the silane-based compound is formed, a method of preparing the copper foil, and a FCCL including the copper foil.

Background Art

A flexible copper clad laminate (FCCL) is a type of printed circuit board (PCB) that is currently increasingly in demand. A FCCL is a multi-layered film formed of two or three layers in which polyimide is laminated on a copper foil. As precision of wirings printed on the FCCL increases, etching precision also increases and thus it is required to reduce the surface roughness of the copper foil. However, as the surface roughness of the copper foil is reduced, peel strength between the copper foil and a substrate (for example, a polyimide film) is deteriorated. In this regard, a means to improve the peel strength is required.

A copper foil for a PCB generally processed using a silane-coupling agent as a surface treating agent of the copper foil for strengthening the peel strength between the copper foil and the substrate is disclosed in Japanese Patent Application 1990-026097.

However, as the requirement for a physical property of the copper foil used in the PCB becomes tight, the copper foil for the PCB on which the surface treatment film having more improved physical property is formed is still required .

Technical Solution

The present invention provides a surface-treated copper foil for a printed circuit board (PCB), including a new silane-based compound or hydrolysate of the silane-based compound that provide excellent peel strength between a substrate and the copper foil, a method of preparing the copper foil for the PCB, and a flexible copper clad laminate (FCCL) including polyimide layers stacked on the copper foil for the PCB.

According to an aspect of the present invention, there is provided a surface-treated copper foil for a printed circuit board (PCB), including an antirust layer formed on a copper foil and a surface treatment film formed on the antirust layer, wherein the surface treatment film includes at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4, or hydrolysates of the silane-based compounds:

wherein R₁, R₂, and R₃ may be each independently a C₁-C₃ alkyl group and R₄ and R₅ may be each independently hydrogen or a C₁-C₅ alkyl group.

According to another aspect of the present invention, there is provided a method of preparing a surface-treated copper foil for a printed circuit board (PCB) including: forming an antirust layer on a copper foil; and washing and drying the copper foil on which the antirust layer is formed and coating a composition comprising at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4 or hydrolysates of the silane-based compounds on the antirust layer and drying the coated antirust layer, thereby preparing a surface treatment film:

According to another aspect of the present invention, there is provided a flexible copper clad laminate (FCCL) including the surface-treated copper foil for the PCB above; and a polyimide film formed on a surface treatment film of the copper foil.

Advantageous Effects

A PCB on which a surface treatment film including a silane-based compound or hydrolysate of the silane-based compound is formed has improved peel strength compared with a PCB on which the surface treatment film is not formed or a PCB on which a surface treatment film including a conventional silane-based compound is formed.

Best Mode

Hereinafter, a surface-treated copper foil for a printed circuit board (PCB), a method of preparing the copper foil for the PCB, and a flexible copper clad laminate (FCCL) according to embodiments of the present invention will be described in more detail.

The surface-treated copper foil for the PCB according to the present embodiment includes an antirust layer formed on a copper foil and a surface treatment film formed on the antirust layer, wherein the surface treatment film includes at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4, or hydrolysates of the silane-based compounds.

wherein, R₁, R₂, and R₃ are each independently a C₁-C₃ alkyl group and R₄ and R₅ are each independently hydrogen or a C₁-C₅ alkyl group.

The silane-based compounds have a siloxane group at the ends thereof for a covalent bond with a copper foil and an imidazole group and/or an imide group at the other end thereof, wherein the imidazole group and/or the imide group has a structure similar to a polyimide film and thus bonding strength with a polyimide film may be improved. Thus, the bonding strength between a copper foil and a polyimide film may be improved.

Specifically, an alkoxy group -OR contained in the silane-based compounds reacts with a hydroxy group that is present in a metal surface so as to form a siloxane bond. The siloxane group contained in the silane-based compound may also form a siloxane bond with a metal surface.

According to another embodiment of the present invention, R₁, R₂, and R₃ in the silane-based compounds are each independently methyl or ethyl and R₄ and R₅ may be hydrogen.

According to another embodiment of the present invention, a heat-blocking layer may be further interposed between the copper foil and the antirust layer. The heat-blocking layer may be, for example, formed of a zinc alloy and the thickness thereof may be several tens to several hundreds of nanometers. A metal or an alloy for forming the heat-blocking layer is not particularly restricted and any metal or alloy which may be used as the heat-blocking layer in the field of the present invention may be used.

According to another embodiment of the present invention, nodules may be further interposed between the copper foil and the heat-blocking layer. The nodules may be formed by flowing a current having a current density of 10 to 150 A/dm2 through an electrolyte at a temperature of 10 to 40 ℃, wherein the electrolyte includes a copper metal of 1 to 40 g/L and a sulfuric acid of 30 to 250 g/L.

The antirust layer may include chromium trioxide, chromic acid, dichromic acid, sodium dichromate, and chromate as antirust agents. The antirust layer may be formed to have a thickness of several tens to several hundreds of nm by flowing a current having a current density of 0.01 to 10 A/dm2 through an electrolyte at a temperature of 10 to 50 ℃ and t he concentration of the antirust agents is 0.1 to 10 g/L. The heat-blocking layer may be formed of a zinc alloy, a nickel alloy, or a cobalt alloy and may be formed to have a thickness of several tens to several hundreds of nm.

The copper foil is generally formed on a substrate that is well known in the field of the present invention. Although additional description of the substrate is omitted; however, use of the substrate is not excluded.

According to another embodiment of the present invention, a method of preparing a copper foil for a PCB may include: forming an antirust layer on a copper foil; and washing and drying the copper foil on which the antirust layer is formed and coating a composition including at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4 and hydrolysates of the silane-based compounds on the antirust layer and drying the coated antirust layer, thereby preparing the surface treatment film.

The copper foil may be prepared by performing copper plating on a material to be plated or a substrate. In the copper plating, an acid plating solution or an alkaline plating solution may be used. The acid plating solution may include a copper sulfate, copper fluoroborate, or sullphamic acid copper plating solution and the alkaline plating solution may include a copper cyanide or copper pyrophosphate plating solution. The plating solution used in the preparation of the copper foil according to an embodiment of the present invention is not particularly restricted and any plating solution used in the field of the present invention may be used.

The antirust layer is formed by electro-depositing chrome on the surface of the copper foil. A chromium compound used may include, for example, chromium trioxide, chromic acid, dichromic acid, sodium dichromate, and chromate. The concentration of the chromium compound may be in a range of 0.1 to 10 g/L, for example, 1.0 to 10 g/L. When the antirust layer is formed, a synergist may be further added to improve efficiency of electro-deposition of the chrome compound. Examples of the synergist may include: a zinc compound such as zinc acetate, zinc chloride, zinc cyanide, zinc nitrate, or zinc sulfate; a phosphorus compound such as phosphoric acid, polyphosphate pyrophosphate, phosphate, or pyrophosphate; and an organic compound such as benzenetriazole. The thickness of the antirust layer may be in a range of 0.1 to 10 nm.

According to another embodiment of the present invention, the composition may include at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4, hydrolysates of the silane-based compounds, and a solvent.

The amount of the silane-based compound may be in a range of 0.001 to 5 weight % of the composition. When the amount of the silane-based compound is 0.001 weight % or less, an organic layer formed of the surface treating agent is not sufficiently coated on the copper foil and thus peel strength is not improved. When the amount of the silane-based compound is 5 weight % or greater, the thickness of an organic layer formed of the surface treating agent increases and the nodules on the copper foil are covered so that peel strength is not improved.

According to another embodiment of the present invention, the solvent may include at least one selected from the group consisting of water, methanol, ethanol, acetone, methylethylketone, ethylacetate, and benzene.

According to another embodiment of the present invention, in the method above, forming a heat-blocking layer on the copper foil may be further performed before the forming of the antirust layer. Details of forming of the heat-blocking layer is the same as described with reference to the copper foil for the PCB, and thus will not be repeated.

According to another embodiment of the present invention, in the method above, forming nodules on the copper foil may be further performed before the forming of the heat-blocking layer. In the forming of the nodules, nodules are formed on the copper foil by using a powdery cupric oxide product and thus a contact area of the copper foil and an additional coating layer increases, thereby improving peel strength between the copper foil and the additional coating layer.

A flexible copper clad laminate according to another embodiment of the present invention may include the copper foil for the PCB and a polyimide film formed on the surface treatment film on the copper foil.

The flexible copper clad laminate may have a two-layered structure (2-layer) or a three-layered structure (3-layer) according to the use thereof.

According to another embodiment of the present invention, the polyimide film may be a hardened product of a polyamic acid solution and the polyamic acid may be a reaction product of at least one dianhydride monomer and at least one diamine monomer, wherein the at least one dianhydride monomer is selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenonetetrahydrocarboxylic anhydride, 3, 3', 4, 4'- biphenyltetracarboxylic dianhydride, and 3,3',4,4'-oxydiphthalic anhydride and the at least one diamine monomer is selected from the group consisting of 4,4'-oxydianiline, para-phenylenediamine, siloxanediamine (SD), 3,4- oxydianiline and meta-phenylenediamine.

The siloxanediamine (SD) may have a structure as below.

In the structure of SD, n is in a range of 2 to 12.

The polyamic acid is a compound that is connected by -C(=O)-NH- bond after reacting the dianhydride monomer with the diamine monomer. The polyamic acid obtained by reacting, for example, pyromellitic anhydride with oxydianiline has the following structure.

When the polyamic acid is thermally treated, polyimide having the following structure may be obtained.

The thermal treatment of the polyamic acid is initiated at about 60 ℃ and is finally completed at a high temperature of about 400 ℃ under a nitrogen atmosphere. In the polyamic acid and the polyimide, n may be in a range of 40 to 200.

A polyamic acid varnish may be, for example, a PMDA/ODA mixture, a BTDA/PDA mixture, a BTDA/PMDA/ODA/PDA mixture, or a PMDA/ODA-SD mixture. Mixing ratios thereof may be appropriately selected according to the use thereof.

Mode for Invention

Hereinafter, the present invention will be described in more detail with reference to the following examples; however, the present invention is not limited thereto. Structures of compounds synthesized in the following examples are identified using a Brucker DRX-300MHz ¹H-NMR and a Jasco 610 FT-IR.

(Synthesis of silane-based compound (1))

Example 1: Synthesis of Compound 1

A Compound 1 represented by Formula 1 was synthesized according to Reaction Scheme 1 below.

[Rectified under Rule 91 27.08.2009]

162.68 g of tetrahydrofurane, 6.259 g (0.05 mol) of glycidoxypropyltrimethoxysilane, and 11.817 g (0.05 mol) of 1-(3-aminopropyl)-imidazole were charged into a reactor and were reacted for 6 hours by maintaining the temperature of the reactor at 95 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 300 rpm. After the reaction was completed, a solvent was removed from a resultant for 2 hours by using a rotary evaporator. Then the resultant was dried for 24 hours in a vacuum oven and 7 g (yield 98 %) of Compound 1 represented by Formula 1 was obtained thereby.

¹ H NMR (300 MHz, CD₃OD) : δ 0.62~0.68(m, 1H), 1.89~1.96(m ,8H), 1.64~1.67(t, 2H), ), 2.54~2.56(t, 7H), 2.58~2.61(m, 6H), 3.28~3.31(m, SiOCH₃) 3.38~3.40(d, 3H), 3.42~3.44(d,4H), .3.50~3.58(m, 5H), 3.64(s, -NH-), 3.80(s, OH), 4.05~4.10(m, 9H), 6.95(s, 10H), 7.12~7.13(t, 11H), 7.65(s, 12H)

IR (neat, cm^-1) : 3650~3200(ν_OH), 3300~3200(ν_NH), 1120~1050(ν_Si-(alkoxy))

(Manufacturing of surface treating agent composition for copper foil)

Example 2

Compound 1 prepared in Example 1 was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that a mixed solution having 1.0 weight % of Compound 1 was prepared.

(Manufacturing of 2-layer FCCL)

Example 3

The mixed solution prepared in Example 2 was left alone for 60 minutes so as to perform hydrolysis and then was spayed on a rolled copper foil (manufactured by Iljin, IL-2), on which nodules, a heat-blocking layer, and an antirust layer were sequentially formed. Then, the rolled copper foil was coated by using an applicator, C.K TRADING. Co, model name: CKAF-1003) and a coated copper foil was prepared thereby. The nodules, the heat-blocking layer, the antirust layer formed on the rolled copper foil were respectively formed of copper (Cu), a zinc alloy, and chrome. The coated copper foil was dried in an oven at 120 ℃ for 30 minutes.

The copper foil treated by using the surface treating agent composition was sprayed with a KRICT-PAA varnish (BPDA:PMDA:PDA:ODA=3:7:6:4) and was coated by using a doctor blade. The coated polyamic acid was hardened at 60 ℃ for 30 minutes, at 120 ℃ for 30 minutes, at 250 ℃ for 30 minutes, and 400 ℃ for 10 minutes under a nitrogen atmosphere so as to prepare a polyimide film and thus a copper foil on which the polyimide film was coated was prepared. The copper foil prepared in Example 3 is hereinafter referred to as Sample 1.

Example 4

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 3, except that a varnish manufactured by Jooyoung Industrial Co., Ltd. (product name: JY-001) was used instead of the KRICT-PAA varnish. The copper foil prepared in Example 4 is hereinafter referred to as Sample 2.

Example 5

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 3, except that a rolled copper foil manufactured by Nikko materials (product name: BHY-22B-T) was used instead of the rolled copper foil (manufactured by Iljin, IL-2) and a Upilex type varnish manufactured by UBE Co., Ltd. was used instead of the KRICT-PAA varnish. The copper foil prepared in Example 5 is hereinafter referred to as Sample 3.

Comparative Example 1

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 3, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 1 is hereinafter referred to as Comparative Sample 1.

Comparative Example 2

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 4, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 2 is hereinafter referred to as Comparative Sample 2.

Comparative Example 3

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 5, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 3 is hereinafter referred to as Comparative Sample 3.

Evaluative Example 1-1: peel strength test

Peel strength was measured for Samples 1 through 3 and Comparative Samples 1 through 3 by using a method prescribed by ASTM D-638. Cross-Head speed was 25 mm/min. and the widths of the samples were 5 mm. The measurement was performed using an Instron 8516. The results of the measurement are shown in Table 1 below.

As shown in Table 1, Samples 1 through 3 prepared by using the surface treating agent composition including the silane-based compound according to embodiments of the present invention shows significantly improved peel strength between the polyimide and the copper foil compared with Comparative Samples 1 through 3 prepared without using the surface treating agent composition.

Evaluative Example 1-2 : moisture resistance test

Samples 1 through 3 were stored in a thermo-hygrostat HIRAYANA PC-R7 at 50 ℃ for 7 days with a relative humidity of 80 % and discoloration of Samples 1 through 3 was distinguished. 7 days later, the colors of Samples 1 through 3 were not changed.

(Synthesis of silane-based compound (2))

Example 6A: Synthesis of Compound 2A

A Compound 2A represented by Formula 2 was synthesized according to Reaction Scheme 2 below.

[Rectified under Rule 91 27.08.2009]

wherein R is methyl.

125.712 g of tetrahydrofurane, 8.9645 g (0.05 mol) of 3-aminopropyltrimethoxysilane, and 5.0035 g (0.05 mol) of succinic anhydride were charged into a reactor and were reacted for 6 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 300 rpm. After the reaction was completed, a solvent was removed from a resultant for 2 hours by using a rotary evaporator. Then, the resultant was dried for 24 hours in a vacuum oven and 13.9 g (yield 99 %) of Compound 2A represented by Formula 2 was obtained thereby.

¹ H NMR (300 MHz) : δ 0.53~0.58(m, 1H), 1.42~1.45(m, 2H), 2.29~2.31(d, 4H), 2.38~2.43(m, 5H), 2.98~3.00(m, 3H), 3.40~3.46(m, SiOCH₃), 8.00(s, -NH-). 12.00(s,-OH)

IR (neat, cm^-1) : 3650~3200(ν_OH), 3300~3200(ν_NH), 1650(ν_CONH),1120~1050(ν_Si-(alkoxy))

Example 6B: Synthesis of compound 2B

A Compound 2B represented by Formula 2 was synthesized according to Reaction Scheme 2 below.

[Rectified under Rule 91 27.08.2009]

wherein R is ethyl.

125.712 g of tetrahydrofurane, 11.0685 g (0.05 mol) of 3-aminopropyltriethoxysilane, and 5.0035 g (0.05 mol) of succinic anhydride were charged into a reactor and were reacted for 6 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 300 rpm. After the reaction was completed, a solvent was removed from a resultant for 2 hours by using a rotary evaporator. Then, the resultant was dried for 24 hours in a vacuum oven and 16 g (yield 99 %) of Compound 2B represented by Formula 2 was obtained thereby.

¹ H NMR (300 MHz) : δ0.58~0.60(m, 1H), 1,22~1.25(m, Si-CH₂), 1.60~1.63(m, 2H), 2.45~2.49(m, 4H), 2.51~2.54(m, 5H), 3.20~3.25(m, 3H), 3.83~3.87(m, Si-CH₃)

(Manufacturing of surface treating agent composition for copper foil)

Examples 7 through 11

Compound 2A prepared in Example 6A was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that mixed solutions respectively having 0.5 weight %, 1 weight %, 2 weight %, 3 weight %, and 5 weight % of Compound 2A, were prepared.

Examples 12 through 16

Compound 2B prepared in Example 6B was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that mixed solutions respectively having 0.5 weight %, 1 weight %, 2 weight %, 3 weight %, and 5 weight % of Compound 2B were prepared.

(Manufacturing of 2-layer FCCL)

Examples 17 through 26

The mixed solutions prepared in Examples 7 through 16 were left alone for 60 minutes so as to perform hydrolysis and then were respectively sprayed on Cr-coated rolled copper foils (manufactured by Iljin, IL-2). Then, the copper foils were coated by using an applicator and coated copper foils were obtained thereby. The coated copper foils were dried in an oven at 120 ℃ for 30 minutes.

The copper foils treated by using the surface treating agent composition were sprayed with a varnish manufactured by Jooyoung Industrial Co., Ltd. (product name: JY-001) and were coated by using a doctor blade.

The coated polyamic acid was hardened at 60 ℃ for 30 minutes, at 120 ℃ for 30 minutes, at 250 ℃ for 30 minutes, and 400 ℃ for 10 minutes under a nitrogen atmosphere so as to prepare a polyimide film and thus copper foils, on which the polyimide films were respectively coated, were prepared. The copper foils prepared in Examples 17 through 26 are hereinafter referred to as Samples 4 through 13.

Comparative Example 4

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 17, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 4 is hereinafter referred to as Comparative Sample 4.

Evaluative Example 2-1: peel strength test

Peel strength of Samples 4 through 13 and Comparative Sample 4 was measured by using a method prescribed by ASTM D-638. Cross-Head speed was 25 mm/min. and the widths of the samples were 5 mm. The measurement was performed using an Instron 8516. The results of the measurement are shown in Table 2 below.

As shown in Table 2, Samples 4 through 13 prepared by using the surface treating agent composition including the silane-based compound according to embodiments of the present invention show significantly improved peel strength between the polyimide film and the copper foil compared with Comparative Sample 4 prepared without using the surface treating agent composition.

Evaluative Example 2-2: moisture resistance test

Samples 4 through 13 were stored in a thermo-hygrostat HIRAYANA PC-R7 at 50 ℃ for 7 days with relative humidity of 80 % and discoloration of Samples 4 through 13 was distinguished. 7 days later, the colors of Samples 4 through 13 were not changed.

(Synthesis of silane-based compound (3))

Example 27 : Synthesis of Compound 3

A Compound 3 represented by Formula 3 was synthesized according to Reaction Scheme 3 below.

[Rectified under Rule 91 27.08.2009]

125.712 g of tetrahydrofurane, 8.9645 g (0.05 mol) of 3-aminopropyltrimethoxysilane, and 7.4550 g (0.05 mol) of 2,3-pyridinedicarboxylic anhydride were charged into a reactor and were reacted for 5 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 300 rpm. After the reaction was completed, a solvent was removed from a resultant for 2 hours by using a rotary evaporator. Then, the resultant was dried for 24 hours in a vacuum oven and 16.4 g (yield 99 %) of Compound 3 represented by Formula 3 was obtained thereby.

¹ H NMR (300 MHz) : : δ0.57~0.59(t, 1H), 1.62~1.80(m, 2H), 03.62~3.67(m, Si-CH₃), 3.85~3.87(t, 3H), 7.93~7.95(t, 4H), 8.56(s, NH), 8.64~8.67(d, 5H), 9.09~9.11(d, 6H), 13.80(s, OH)

(Manufacturing of surface treating agent composition for copper foil)

Examples 28 through 29

Compound 3 prepared in Example 27 was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that mixed solutions respectively having 0.5 weight % and 1 weight of Compound 3 of were prepared.

(Manufacturing of 2-layer FCCL)

Examples 30 through 31

The mixed solutions prepared in Examples 28 through 29 were left alone for 60 minutes so as to perform hydrolysis and then were respectively sprayed on Cr-coated rolled copper foils (manufactured by Iljin, IL-2). Then, the copper foils were coated by using an applicator and coated copper foils were prepared. The coated copper foils were dried in an oven at 120 ℃ for 30 minutes.

The copper foils treated by using the surface treating agent composition were sprayed with a Upilex type varnish (product name :U-varnish-S) manufactured by UBE Co., Ltd. and were coated by using a doctor blade.

The coated polyamic acid was hardened at 60 ℃ for 30 minutes, at 120 ℃ for 30 minutes, at 250 ℃ for 30 minutes, and 400 ℃ for 10 minutes under a nitrogen atmosphere so as to prepare a polyimide film and thus copper foils, on which the polyimide films were respectively coated, were prepared. The copper foils prepared in Examples 30 through 31 are hereinafter referred to as Samples 14 through 15.

Comparative Example 5

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 30, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 5 is hereinafter referred to as Comparative Sample 5.

Evaluative Example 3-1: peel strength test

Peel strength of Samples 14 and 15 and Comparative Sample 5 was measured by using a method prescribed by ASTM D-638. Cross-Head speed was 25 mm/min. and the widths of the samples were 5 mm. The measurement was performed using an Instron 8516. The results of the measurement are shown in Table 3 below.

As shown in Table 3, Samples 14 through 15 prepared by using the surface treating agent including the silane-based compound according to embodiments of the present invention have significantly improved peel strength between the polyimide film and the copper foil compared with Comparative Sample 5 prepared without using the surface treating agent composition.

Evaluative Example 3-2 : moisture resistance test

Samples 14 through 15 were stored in a thermo-hygrostat HIRAYANA PC-R7 at 50 ℃ for 7 days with a relative humidity of 80 % and discoloration of Samples 14 and 15 was distinguished. 7 days later, the colors of Samples 14 and 15 were not changed.

(Synthesis of silane-based compound (4))

Example 32A : Synthesis of compound 4A

A Compound 4A represented by Formula 4 was synthesized according to Reaction Scheme 4 below.

[Rectified under Rule 91 27.08.2009]

wherein R is methyl.

125.712 g of tetrahydrofurane, 8.9645 g (0.05 mol) of 3-aminopropyltrimethoxysilane, and 9.6065 g (0.05 mol) of 1,2,4-benzenetricarboxylic acid anhydride (2,3-pyridinedicarboxylic anhydride) were charged into a reactor and were reacted for 6 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 250 rpm. When the reaction was completed, a solvent was removed from a resultant for 1 hour by using a rotary evaporator. Then, the resultant was dried for 48 hours in a vacuum oven and 18.5 g (yield 99 %) of the compound 4A represented by Formula 4 was obtained thereby.

¹ H NMR (300 MHz) : δ0.62~0.65(t, 1H), 1.71~1.76(m, 2H), 3.41~3.47(m, Si-CH₃), 3.56~3.60(m, 3H), 7.45(s, NH)

Examples 32B : Synthesis of compound 4B

A Compound 4B represented by Formula 4 was synthesized according to Reaction Scheme 4 below.

[Rectified under Rule 91 27.08.2009]

wherein R is ethyl.

125.712 g of tetrahydrofurane, 8.9645 g (0.05 mol) of 3-aminopropyltriethoxysilane, and 9.6065 g (0.05 mol) of 1,2,4-benzenetricarboxylic acid anhydride (2,3-pyridinedicarboxylic anhydride) were charged into a reactor and were reacted for 6 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 250 rpm. After the reaction was completed, a solvent was removed from a resultant for 1 hour by using a rotary evaporator. Then. the resultant was dried for 48 hours in a vacuum oven and 20.6 g (yield 99 %) of Compound 4B represented by Formula 4 was obtained thereby.

¹ H NMR (300 MHz, CD₃OD) : δ0.71~0.73(t,1H), 1.14~1.23(m, Si-CH3), 1.71~1.74(m, 2H),3.58~3.60(t, 3H), 3.79~3.86(m, Si-CH₂), 8.55(s, NH)

(Manufacturing of surface treating agent composition for copper foil)

Examples 33 through 34

Compound 4A prepared in Example 32A was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that mixed solutions respectively having 0.5 weight % and 1 weight % of Compound 4A were prepared.

Examples 35 through 36

Compound 4B prepared in Example 32B was mixed with a solvent mixture obtained by mixing water and methanol in a volume ratio of 1:9 so that mixed solutions respectively having 0.5 weight % and 1 weight % of Compound 4B were prepared.

(Manufacturing of 2-layer FCCL)

Examples 37 through 40

The mixture solutions prepared in Examples 33 through 36 were left alone for 60 minutes so as to perform hydrolysis and then were respectively sprayed on Cr-coated rolled copper foils (manufactured by Iljin, IL-2). Then, the copper foils were coated by using an applicator and coated copper foils were prepared thereby. The coated copper foils were dried in an oven at 120 ℃ for 30 minutes.

The copper foils treated by using the surface treating agent composition were sprayed with a varnish (product name: JY-001) manufactured by Jooyoung Co., Ltd. and were coated by using an applicator.

The coated polyamic acid was hardened at 60 ℃ for 30 minutes, at 120 ℃ for 30 minutes, at 250 ℃ for 30 minutes, and 400 ℃ for 10 minutes under a nitrogen atmosphere so as to prepare polyimide films and thus copper foils, on which the polyimide films were respectively coated, were prepared. The copper foils prepared in Examples 37 through 40 are hereinafter referred to as Samples 16 through 19.

Comparative Example 6

A copper foil, on which a polyimide film was coated, was prepared in the same manner as in Example 37, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foil prepared in Comparative Example 6 is hereinafter referred to as Comparative Sample 6.

Evaluative Example 4-1: peel strength test

Peel strength of Samples 16 through 19 and Comparative Sample 6 was measured by using a method prescribed by ASTM D-638. Cross-Head speed was 25 mm/min. and the widths of the samples were 5 mm. The measurement was performed using an Instron 8516. The results of the measurement are shown in Table 4 below.

As shown in Table 4, Samples 16 through 19 prepared by using the surface treating agent composition including the silane-based compound according to embodiments of the present invention have significantly improved peel strength between the polyimide film and the copper foil compared with Comparative Sample 6 prepared without using the surface treating agent composition.

Evaluative Example 4-2 : moisture resistance test

Samples 16 through 19 were stored in a thermo-hygrostat HIRAYANA PC-R7 at 50 ℃ for 7 days with relative humidity of 80 % and discoloration of Samples 16 through 19 was distinguished. 7 days later, the colors of Samples 16 through 19 were not changed.

(comparison of peel strength according to types of polyimide)

(Manufacturing of 2-layer FCCL)

Examples 41 through 44

Copper foils, on which polyimide films were respectively coated, were prepared in the same manner as in Example 37, except that a PMDA/ODA varnish, a BTDA/PDA varnish, a BTDA/PMDA/ODA/PDA varnish, and a PMDA/ODA-SD varnish were respectively used instead of the Upilex type varnish manufactured by UBE Co., Ltd. Here, 0.5 weight % of Compound 4B was used as a surface treating agent. The copper foils prepared in Examples 41 through 44 are hereinafter referred to as Samples 20 through 23.

The varnishes described above are manufactured by using methods described below.

PMDA/ODA varnish

255.000 g of DMAc (N,N-dimethylacetamide), 21.538 g (0.107563 mol) of 4,4'-oxydianiline, and 23.462 g (0.107563 mol) of pyromellitic dianhydride were sequentially charged into a reactor and were reacted for 24 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 350 rpm. Then, a varnish containing 15 weight % of polyamic acid was prepared thereby.

BTDA/PDA varnish

255.000 g of DMAc (N,N-dimethylacetamide), 11.307 g (0.104561 mol) of meta-phenylenediamine, and 33.693 g (0.104561 mol) of 3,3',4,4'-biphenontetracarboxylic acid anhydride were sequentially charged into a reactor and were reacted for 24 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 350 rpm. Then, a varnish containing 15 weight % of polyamic acid was prepared thereby.

BTDA/PMDA/ODA/PDA varnish

255 g of DMAc, 6.334 g (0.031633 mol) of 4,4'-oxydianiline, and 7.982 g (0.073811 mol) of meta-phenylenediamine were charged into a reactor and were completely dissolved. Then, 23.784 g (0.073811 mol) of 3,3',4,4'-biphenonetetracarboxylic anhydride and 6.900 g (0.031633 mol) of pyromellitic anhydride were charged into the reactor and were reacted for 24 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 350 rpm. Then, a varnish containing 15 weight % of polyamic acid was prepared thereby.

PMDA/ODA-SD varnish

127.5 g of DMAc, 9.826 g (0.04907 mol) of 4,4'-oxydianiline, and 1.408 g (0.002583 mol) of SD-545 were charged into a reactor and were completely dissolved. Then, 11.267 g (0.0.051653 mol) of pyromellitic anhydride was charged into the reactor and was reacted for 24 hours by maintaining the temperature of the reactor in a range of -5 to 5 ℃ under a nitrogen atmosphere with rotating a mechanical stirrer at 350 rpm. Then, a varnish containing 15 weight % of polyamic acid was prepared thereby.

Comparative Example 7 through 10

Copper foils, on which polyimide films were respectively coated, were prepared in the same manner as in Examples 41 through 44, except that the step of treating the surface of the copper foil by using the surface treating agent composition was omitted. The copper foils prepared in Comparative Example 7 through 10 are hereinafter referred to as Comparative Samples 7 through 10.

Evaluative Example 5 - peel strength test

Peel strength of Samples 20 through 23 and Comparative Samples 7 through 10 was measured by using a method prescribed by ASTM D-638. Cross-head speed was 25 mm/min. and the widths of the samples were 5 mm. The measurement was performed using an Instron 8516. The results of the measurement are shown in Table 5 below.

As shown in Table 5, Samples 20 through 23 prepared by using the surface treating agent composition including the silane-based compound according to embodiments of the present invention have significantly improved peel strength between the polyimide and the copper foil compared with Comparative Samples 7 through 10 prepared without using the surface treating agent composition.

As described above, according to the present invention, a PCB on which a surface treatment film including a silane-based compound or hydrolysate of the silane-based compound is formed has improved peel strength compared with a PCB on which the surface treatment film is not formed or a PCB on which a surface treatment film including a conventional silane-based compound is formed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Industrial Applicability

Claims

A surface-treated copper foil for a printed circuit board (PCB), comprising an antirust layer formed on a copper foil and a surface treatment film formed on the antirust layer, wherein the surface treatment film comprises at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4, or hydrolysates of the silane-based compounds:

<Formula 1> <Formula 2>

<Formula 3> <Formula 4>

wherein R₁, R₂, and R₃ are each independently a C₁-C₃ alkyl group and R₄ and R₅ are each independently hydrogen or a C₁-C₅ alkyl group.
The surface-treated copper foil for the PCB of claim 1, wherein the R₁, R₂, and R₃ are each independently methyl or ethyl and the R₄ and R₅ are hydrogen.
The surface-treated copper foil for the PCB of claim 1, further comprising a heat-blocking layer interposed between the copper foil and the antirust layer.
The surface-treated copper foil for the PCB of claim 3, further comprising a nodule layer interposed between the copper foil and the heat-blocking layer.
A method of preparing a surface-treated copper foil for a printed circuit board (PCB) comprising: forming an antirust layer on a copper foil; and washing and drying the copper foil on which the antirust layer is formed and coating a composition comprising at least one compound selected from the group consisting of silane-based compounds represented by Formulae 1 through 4 or hydrolysates of the silane-based compounds on the antirust layer and drying the coated antirust layer, thereby preparing a surface treatment film:

<Formula 1> <Formula 2>

<Formula 3> <Formula 4>

wherein R₁, R₂, and R₃ are each independently a C₁-C₃ alkyl group and R₄ and R₅ are each independently hydrogen or a C₁-C₅ alkyl group.
The method of claim 5, wherein the amount of the silane-based compound is in a range of 0.001 to 5 weight % based on the total amount of the composition.
The method of claim 5, wherein the composition comprises at least one solvent selected from the group consisting of water, methanol, ethanol, acetone, methylethylketone, ethylacetate, and benzene.
The method of claim 5, further comprising forming a heat-blocking layer on the copper foil before the forming of the antirust layer.
The method of claim 8, further comprising processing a nodule formed on the copper foil before the forming of the heat-blocking layer.
A flexible copper clad laminate (FCCL) comprising the surface-treated copper foil for the PCB of any one of claims 1 through 4; and a polyimide film formed on a surface treatment film of the copper foil.
The FCCL of claim 19, wherein the polyimide film comprises a hardened product of a polyamic acid consisting of a reaction product of at least one dianhydride monomer and at least one diamine monomer, wherein the at least one dianhydride monomer is selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenonetetrahydrocarboxylic dianhydride, 3, 3', 4, 4'- biphenyltetracarboxylic acid dianhydride, and 3,3',4,4'-oxydiphthalic anhydride and the at least one diamine monomer is selected from the group consisting of 4,4'-oxydianiline, para-phenylenediamine, siloxanediamine (SD), 3,4- oxydianiline and meta-phenylenediamine.