KR20010018724A - Composition for enhancing adhesion of multilayer printed circuit, inner circuitry substrate for multilayer printed circuit formed using the same and surface-treating method of the same - Google Patents

Abstract

PURPOSE: Provided is composition for multilayer printed circuit, which doesn't occur phenomenon of pink ring and improves adhesive strength of copper foil of multilayer printed circuit with polymer resin matrix. CONSTITUTION: The composition is characterized by containing a solvent and a silane compound of formula: (Si(X)3(Y), wherein, X is one selected from halogen atom, C1-C5 alkyl group and C1-C5 alkoxy group; Y is one selected from the group consisting of C1-C5 alkyl, C1-C5 alkoxy, vinyl, allyl, cyanoalkyl group, -(CH2)m-NH-CO-NH2, -(CH2)m-O-C(CH3)=CH2, -(CH2)m-NH2, -(CH2)m-SH, -(CH2)m-Cl, -(CH2)mN-(CH2)n-NH2, , , and the following formula; and m and n are independently integer of 1-5).

Description

Composition for enhancing adhesion of multilayer printed circuit, inner circuitry substrate for multilayer printed circuit formed using the same and surface-treating method of the same }

The present invention relates to an adhesive improving composition for a multilayer printed circuit, an inner layer circuit board formed using the same, and a surface treatment method of the inner layer circuit board, and more particularly, to improve adhesion between copper foil and a polymer resin substrate of a multilayer printed circuit board. It relates to an adhesive improving composition, an inner layer circuit board of a multilayer printed circuit formed using the same, and a surface treatment method thereof.

Printed circuits are widely used as precision control circuits of various electric and electronic communication devices such as televisions, radios, computers, telephone exchanges, and wireless transceivers.

Copper-clad laminate for printed circuit is a copper foil is laminated on a glass-epoxy resin-impregnated substrate, a phenol resin, an epoxy resin, polyimide, polyester, and the like by heating, pressing and laminating it, and etching it. After the formation, the semiconductor device is fabricated by mounting an element such as a semiconductor device thereon.

Looking at the conventional manufacturing process of the copper foil for a printed circuit described above, first, a copper foil is obtained through a process of reducing copper ions to a metal by an electrolysis method, and then washed with water and dried. Then, a processus | protrusion process is performed on the contact surface with the insulating base material of copper foil, ie, a non-gloss surface. Here, the projection process is a process of improving the adhesion between the copper foil and the insulating substrate by forming a projection on the surface of the copper foil using copper oxide powder to increase the surface area of the copper foil and the insulating substrate.

Thereafter, a metal barrier layer is formed on the copper foil that has undergone the roughening step to prevent diffusion of copper ions, and then antirust treatment is performed.

Finally, in order to improve the adhesive force between the copper foil and the insulating substrate, chemical adhesion improving treatment using a chemical binder is carried out (Japanese Patent Laid-Open No. 63-183178 and Japanese Patent Laid-Open No. 2-26097).

On the other hand, in recent years, as the circuit of the substrate is gradually miniaturized, highly integrated and miniaturized according to the high quality of the printed circuit board, the demand for the multilayer printed circuit board is gradually increasing.

In the case of a multilayer printed circuit board, in order to improve the adhesive force between the copper foil surface of the internal circuit board and the polymer substrate, a so-called copper oxide treatment commonly referred to as "black oxide treatment" is performed.

By the way, when the copper oxide treatment is performed in this way, the adhesion between the copper foil and the polymer resin substrate is improved, but it is not preferable in terms of health and safety of the worker because it is made at a high temperature while using a strong alkaline solution. In addition, foreign matters such as black spots and dust remain on the surface of the copper foil obtained by the copper oxide treatment, and the surface smoothness becomes poor. In addition, there is a problem in that the oxide is deteriorated during the overtreatment, the adhesive strength with the resin layer is lowered.

Multilayer printed circuits have plated through-holes so that the circuits of each layer can be electrically connected to one another. The through hole plating process includes a step of removing resin from the hole surface, an activation step using a catalyst, an electroless copper plating, an electrolytic copper plating, and the like. However, in such a plating process, an inorganic acid is frequently used, and the inorganic acid dissolves an adhesion improving layer, such as copper oxide, which is exposed to a through hole or a region near it. The dissolution of a part of copper oxide is called a pink ring or haloing, and the copper metal present in the lower layer is exposed to pink color, thereby causing local circuit peeling.

In order to solve the above problems, a method of increasing the thickness of copper oxide has been proposed, but there is a problem in that a thick copper oxide layer lowers the effect of improving adhesion between the copper foil and the polymer resin substrate.

According to U.S. Patent No. 4,775,44, a multi-layer is formed by inserting a pre-preg layer, a semi-cured non-conductive polymer resin layer, between inner-layer circuit boards surface-treated with an adhesion promoter, copper oxide. A method of completing a printed circuit board is known, which comprises contacting an aqueous chromic acid solution prior to laminating a printed circuit board comprising a prepreg layer and an inner layer circuit board surface-treated with copper oxide. The contact with the aqueous chromic acid solution here is intended to prevent the copper oxide layer from partially dissolving by the acidic medium to prevent pink ring and local circuit peeling.

U.S. Patent Nos. 4,642,161, 4,902,551 and 4,981,560 disclose a method of treating copper oxide on the surface of copper foil with an adhesion enhancer before constructing a multilayer printed circuit board. To metal copper. As a result, there is no pinking phenomenon due to the dissolution of copper oxide in the inner layer circuit of the multilayer printed circuit board, but peeling occurs easily at the phase interface due to peeling of metal copper, that is, phase separation of copper and electrolytic copper foil by reduction of copper oxide. There is a problem.

WO 96/19097 discloses a method of contacting a metal surface with an adhesion enhancing composition containing hydrogen peroxide, an inorganic acid, a preservative and a quaternary ammonium salt, which is a surfactant, in order to improve the adhesion of the polymeric resin substrate to the internal circuit board. According to this method, the pink ring phenomenon is slightly reduced compared with the prior art, but there is a lot of room for improvement because the pink ring phenomenon should be minimized and the economy is inferior.

U.S. Patent 5,869,130 also discloses a method of contacting a metal surface with an adhesion enhancing composition containing an oxidizing agent, an acid, a corrosion inhibitor, a source of chlorine ions, and a water soluble polymer, and then bonding the polymeric material to the metal surface. Known. According to this method, the adhesion of the polymer resin substrate to the surface of the metal, in particular copper or copper alloy, can be improved, but the phenomenon that the copper oxide layer formed on the surface of the copper foil is corroded, that is, the pink ring phenomenon cannot be completely eliminated. There was no.

The technical problem to be achieved by the present invention is to solve the above problems and to provide an adhesive improving composition for a multilayer printed circuit that can improve the adhesion between the copper foil and the polymer resin substrate without any pinking phenomenon.

Another object of the present invention is to provide an inner circuit board of a multilayer printed circuit obtained by using the adhesion improving composition for multilayer printed circuits.

Another technical problem to be achieved by the present invention is to provide a surface treatment method of the inner circuit board.

In the present invention to achieve the first technical problem,

It provides an adhesive improving composition for a multilayer printed circuit comprising a silane compound of Formula 1 and a solvent.

<Formula 1>

Si (X) ₃ (Y)

Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms,

Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group,

Selected from the group consisting of

m and n are integers of 1 to 5 irrespective of each other.

A second object of the present invention is to form a rust-proof film on the glossy surface of the copper foil without copper oxide treatment on the surface of the copper foil laminated substrate including the copper foil and an insulating substrate interposed therebetween, It consists of the internal circuit board for multilayer circuits characterized by the surface treatment film formed by coating and drying a silane compound containing composition.

<Formula 1>

Si (X) ₃ (Y)

Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms,

Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group,

Selected from the group consisting of

m and n are integers of 1 to 5 irrespective of each other.

The silane compound of Chemical Formula 1 may include, in particular, vinyltrichlorosilane (H ₂ C═CHSiCl ₃ ), vinyltriethoxysilane [H ₂ C═CHSi (OC ₂ H ₅ ) ₃ ], vinyltrimethoxysilane [H ₂ C = CHSi (OCH ₃ ) ₃ ], allyltriethoxysilane [H ₂ C = CHCH ₂ Si (OC ₂ H ₅ ) ₃ ], allyltrimethoxysilane [H ₂ C = CHCH ₂ Si (OCH ₃ ) ₃ ], Cyanoethyltriethoxysilane [CNCH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ ], cyanomethyltrimethoxysilane [CNCH ₂ Si (OCH ₃ ) ₃ ], N- (triethoxysilyl) Propylurea [(C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ NHC (= 0) NH ₂ ], N- [3- (triethoxysilyl) -propyl-4,5- of Structural Formula (A) Dihydroimidazole, 3-methacryloxypropyltrimethoxysilane [H ₂ C═C (CH ₃ ) OCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ] 3-glycidoxypropyl of the following structural formula (B) Trimethoxysilane, ß- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane of the following structural formula (C), N-2- (aminoethyl) -3-aminopropyltrimethoxysilane [H ₂ NCH _{2 CH 2 N (CH 2)} 3 Si (OCH 3) 3], 3- O The exposure profile triethoxysilane _{[H 2 N (CH 2)} 3 Si (OCH 2 CH 3) 3], 3- mercaptopropyltrimethoxysilane _{[HS (CH 2) 3 Si} (OCH 3) 3], or It is preferably 3-chloropropyltrimethoxysilane [Cl (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ], the content of which is 0.001 to 5% by weight based on the total weight of the composition.

The third technical problem of the present invention is the step of (a) forming a rustproof layer on the glossy surface of the copper foil, without the copper oxide treatment on the surface of the copper foil of the copper foil laminated substrate including the copper foil and an insulating substrate inserted therebetween; And

(b) washing and drying the copper foil laminated substrate on which the rust-preventing layer is formed, and then coating and drying the composition comprising the silane compound of Formula 1 on the rust-proof layer to form a surface treatment film. It is made by the surface treatment method of the inner layer circuit board for circuits.

<Formula 1>

Si (X) ₃ (Y)

Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms,

Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group,

Selected from the group consisting of

m and n are integers of 1 to 5 irrespective of each other.

This invention has the characteristics in providing the adhesive improvement composition for improving the adhesive force between the copper foil of an internal circuit board, and a polymeric resin base material. Moreover, this invention forms the copper foil laminated board | substrate by inserting copper foil and the polymeric resin base material which is an insulation base material between them, and a rustproof layer directly on the copper foil glossy surface, without going through copper oxide treatment on the copper foil glossy surface of this copper foil laminated substrate, It is characterized by coating and drying the adhesion improving composition containing the silane compound of Formula 1 to form a surface treatment film.

The silane compound of Formula 1 may be coated only on its own, or may be coated in a state dissolved in a solvent. In the case of coating the silane compound itself, it is allowed to stand in the air for a predetermined time after the coating so that the silane compound coated on the surface of the copper foil and the moisture in the air may react. As a result of this reaction, the surface treatment film is made of the result of the self-condensation reaction of the hydrolyzate of the silane compound.

As described above, the silane compound of Formula 1 may be coated in a state dissolved in water or a mixed solvent of water and an organic solvent. When dissolved in water as described above, the silane compound is hydrolyzed and the hydrolyzate condenses itself to form a polymer resin. The polymer resin thus formed serves to improve adhesion between the copper foil of the internal circuit board and the polymer resin substrate.

In the present invention, as mentioned above, the resist film is completely removed and a circuit treatment film is formed on the copper foil surface of the inner circuit board in a state where the circuit is completely formed. The phenomenon does not occur at all. And because the thickness of the surface treatment film is several to several tens of microns, it is possible to improve the adhesion between the surface of the copper foil and the polymer resin substrate while maintaining the thickness and surface roughness characteristics. Therefore, it is advantageous to microcircuit and it is possible to configure the inner layer circuit of the multilayer printed circuit board without any pinking phenomenon.

Hereinafter, a method of treating a surface of an internal circuit board of a multilayer printed circuit according to the present invention will be described.

First, a circuit pattern is formed on copper foil as desired using a resist, and an internal circuit board which is a patterned copper foil laminated substrate is manufactured. The antirust process is given to the gloss surface of copper foil in the state which has not provided the processus process, ie, copper oxide process, on the copper foil surface of this internal circuit board. The antirust treatment method is not particularly limited, but in the present invention, the glossy surface of the copper foil is deposited in an electrolytic plating bath containing a chromium compound as a rust preventive agent, and then a predetermined current is applied to the electrolytic bath so that the chromium of the cathode is coated on the copper foil surface of the anode. Electrodeposition method is used.

Examples of the chromium compound include chromium trioxide, chromium anhydride, chromic acid, potassium dichromate, dichromate such as sodium dichromate and chromate such as potassium chromate. The concentration of the chromium compound is preferably 0.1 to 10 g / l, preferably 1.0 to 10 g / l.

In order to increase the electrodeposition efficiency of the chromium compound during the rust prevention treatment, an effect enhancer may be further added to the electrolytic plating bath. Here, the effect enhancer may be zinc compounds such as zinc acetate, zinc chloride, zinc cyanide, zinc nitrate, zinc sulfate, or phosphoric acid compounds such as phosphoric acid, phosphorous acid, polyphosphoric acid, pyrophosphate, phosphate, pyrophosphate, and the like.

The temperature of the electrolytic plating bath in the antirust treatment step is about 15 to 40 ° C, preferably 20 to 25 ° C. The hydrogen ion concentration of the electrolytic plating bath containing the chromium compound is not so important because it depends on the type of the chromium compound.

The current density is about 0.1 to 10 A / dm ² , preferably 0.5 to 5 A / dm ² , and the time for electrodepositing the copper foil surface to the electrolytic plating bath is about 1 to 20 seconds, preferably 5 to 10 seconds. The thickness of the antirust layer formed by such a process is about 25-100 kPa.

Subsequently, the internal circuit board on which the rust preventive layer was formed is washed with deionized water and then dried. The cleaning solution then serves to remove excess chromium solution from the surface of the circuit.

Thereafter, the adhesion improving composition comprising the silane compound of Formula 1 and a solvent is coated and dried. At this time, the solvent is water or at least one mixed solvent selected from ethanol, methanol, methyl ethyl ketone and benzene.

Herein, the coating method of the adhesion improving composition containing the silane compound of Formula 1 is not particularly limited. As a specific example, a deposition method, a spray method, an electrochemical coating method, etc. are possible, and a spray method is a simpler method among these. And after coating of the composition, it is preferable to squeeze uniformly with a rubber roller or the like.

The silane compound may be coated directly on the copper foil of the compound itself, it is also possible to coat a composition dissolved in a solvent such as water, ethanol, methanol, methyl ethyl ketone, benzene, and more particularly, the coating in the composition state Do. This is because the concentration control and the coating amount control is easier. At this time, the content of the silane compound is preferably 0.001 to 5% by weight, particularly 0.1 to 1% by weight based on the total weight of the composition. In the case where the content of the silane compound is less than 0.001% by weight, the adhesion between the copper foil and the insulating substrate is not sufficient, and when the content of the silane compound exceeds 5% by weight, the production cost of the copper foil is increased, which is not economical.

Although the temperature in particular of a silane compound containing composition is not restrict | limited, It is preferable to adjust to 15-45 degreeC, More preferably, it is about 20-30 degreeC. And the drying temperature of the internal circuit board after coating a silane compound containing composition is 60-170 degreeC, More preferably, it is about 90-150 degreeC. In the case where the drying temperature is less than 60 ° C, the self-condensation reaction of the hydrolyzate of the silane compound is not desired, and the effect of improving adhesion between the copper foil and the insulating substrate is insignificant, and when it exceeds 170 ° C, the copper is oxidized by high heat. I can't.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

Example 1

The copper foil polished surface of the copper foil laminated substrate was washed with deionized water, and then plated for 5 seconds at a current density of 1 A / dm ² in an electrolytic plating bath containing 2 g / l of chromic anhydride to form an rust preventive film.

The copper foil surface on which the rust preventive film was formed was washed with water and dried, which was then immersed in the adhesion improving composition for 30 seconds, and then dried at 110 ° C. for 5 minutes. The adhesion improving composition was prepared by diluting 0.2 wt% of 3-aminopropyltriethoxysilane with 99.8 wt% of water.

Subsequently, the resultant copper foil was molded on an epoxy resin-impregnated glass fiber substrate (ANSI grade FR-4) at 175 ° C. at 30 kgf / cm 2 for 2 hours to complete a multilayer printed circuit.

Example 2

Except that 3-glycidoxypropyltrimethoxysilane was used instead of 3-aminopropyltriethoxysilane in preparing the adhesion improving composition, the same procedure as in Example 1 was performed to complete a multilayer printed circuit.

Example 3

A multilayer printed circuit was completed in the same manner as in Example 1, except that 3-mercaptopropyltrimethoxysilane was used instead of 3-aminopropyltriethoxysilane in the preparation of the adhesion improving composition.

Comparative example

A multilayer printed circuit was completed in the same manner as in Example 1 except that the bond promoting treatment using the adhesion improving composition was not performed.

In the multilayer printed circuit manufactured according to the said Example 1-3 and the comparative example, the peeling strength of copper foil and FR-4 resin base material was measured according to JIS C6481.

As a result of the measurement, in the case of Example 1, it was 1.0kgf / cm, in the case of Example 2, 0.98kgf / cm, and in Example 3, it was 0.89kgf / cm, whereas in the comparative example, it was 0.2kgf / cm. Thus, in the case of Example 1-3, compared with the case of the comparative example, it was confirmed that the adhesive force of copper foil and FR-4 resin base material improves.

In addition, according to the above Example 1-3, there was no conventional pinking phenomenon since the process of performing copper oxide treatment on the surface of the copper foil was not performed. Since the copper oxide treatment process can be omitted, the surface treatment process is simpler than the conventional case and the treatment cost is reduced.

According to the present invention, since the surface treatment film for improving the adhesion to the rust-proof layer and the adhesion on the copper foil glossy surface of the inner layer circuit board without the process of copper oxide treatment, the adhesion between the copper foil surface and the insulating substrate without any pinking phenomenon occurs Can be improved. In addition, since the copper oxide treatment process is unnecessary, the surface treatment process is simpler and the treatment cost is reduced, and the by-product gas generated during the copper oxide treatment, the treatment and washing and drying processes are omitted, and there is no foreign matter on the glossy surface. Defective rate is also significantly reduced.

Therefore, according to the present invention, it is possible to obtain an inner circuit board of a multilayer printed circuit, which is advantageous for microcircuiting and without any pinking phenomenon.

Claims (11)

An adhesion improving composition for a multilayer printed circuit comprising a silane compound of Formula 1 and a solvent. <Formula 1> Si (X) ₃ (Y) Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms, Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group, Selected from the group consisting of m and n are integers of 1 to 5 irrespective of each other. The silane compound of claim 1, wherein the silane compound of Formula 1 is vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, cyanoethyltriethoxysilane, Cyanomethyltrimethoxysilane, N- (triethoxysilyl) propylurea, N- [3- (triethoxysilyl) -propyl] -4,5-dihydroimidazole, 3-methacryloxypropyltri Methoxysilane, 3-glycidoxypropyltrimethoxysilane, ß- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane And at least one selected from the group consisting of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and 3-chloropropyltrimethoxysilane. A rustproof film is formed on the gloss surface of the copper foil without copper oxide treatment on the surface of the copper foil laminated substrate including the copper foil and the insulating substrate interposed therebetween, and the silane compound-containing composition of formula 1 is coated on the rustproof film and The dried surface treatment film is formed, The internal circuit board for multilayer printed circuits characterized by the above-mentioned. <Formula 1> Si (X) ₃ (Y) Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms, Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group, Selected from the group consisting of m and n are integers of 1 to 5 irrespective of each other. The silane compound of claim 3, wherein the silane compound of Formula 1 is vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, cyanoethyltriethoxysilane, Cyanomethyltrimethoxysilane, N- (triethoxysilyl) propylurea, N- [3- (triethoxysilyl) -propyl] -4,5-dihydroimidazole, 3-methacryloxypropyltri Methoxysilane, 3-glycidoxypropyltrimethoxysilane, ß- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane At least one selected from the group consisting of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. 4. The internal circuit board of claim 3, wherein the surface treatment film comprises a condensation reaction product of a hydrolyzate of the silane compound of formula (1). (a) forming a rustproof layer on the glossy surface of the copper foil without the copper oxide treatment on the surface of the copper foil of the copper foil laminated substrate including the copper foil and an insulating base sandwiched therebetween; And (b) washing and drying the copper foil laminated substrate on which the rust-preventing layer is formed, and then coating and drying the composition comprising the silane compound of Formula 1 on the rust-proof layer to form a surface treatment film. Surface treatment method of inner layer circuit board for circuits. <Formula 1> Si (X) ₃ (Y) Wherein X is selected from the group consisting of a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, Y is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a vinyl group, an allyl group, a cyanoalkyl group, Selected from the group consisting of m and n are integers of 1 to 5 irrespective of each other. The method of claim 6, wherein the silane compound represented by Formula 1 is vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, cyanoethyltriethoxysilane, Cyanomethyltrimethoxysilane, N- (triethoxysilyl) propylurea, N- [3- (triethoxysilyl) -propyl] -4,5-dihydroimidazole, 3-methacryloxypropyltri Methoxysilane, 3-glycidoxypropyltrimethoxysilane, ß- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane At least one selected from the group consisting of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and 3-chloropropyltrimethoxysilane. The method of claim 6, wherein the content of the silane compound of Formula 1 is 0.001 to 5% by weight based on the total weight of the composition. The method of claim 6, wherein in step (b), the copper foil coated with the silane compound-containing composition of Formula 1 is dried at 60 to 170 ° C. The method of claim 6, wherein the silane compound-containing composition of Formula 1 of step (b) comprises water or at least one mixed solvent selected from the group consisting of water and ethanol, methanol, methyl ethyl ketone and benzene. Way. The method of claim 6, wherein the anti-rust layer forming step (a) is formed by electroplating a rust-preventing composition comprising chromic acid, dichromic acid or salts thereof.