KR20060006389A - Method of manufacturing surface-treated copper foil for pcb having fine-circuit pattern and surface-treated copper foil thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a surface-treated copper foil for a microcircuit board suitable for the production of a substrate having a microcircuit pattern.

Placing copper foil as a cathode in an electroplating bath containing Co, Ni, ammonium salt and citric acid, and depositing a roughened layer of Co—Ni alloy on the surface of the copper foil so that the surface roughness is 0.5 μm or less; Forming a pure Zn or Zn alloy coating layer on the roughened layer; Forming an electrolytic chromate layer on the coating layer; Forming a silane coupling agent treatment layer on the electrolytic chromate layer; Characterized in that comprises a.

The surface-treated copper foil produced by the manufacturing method of the present invention is excellent in overall required properties as a copper foil such as adhesive strength with the substrate, heat-resistant adhesive strength, chemical resistance, and etching resistance, and is very suitable as a copper foil for a microcircuit board. .

Microcircuit Board, Ammonium Salt, Citric Acid, Adhesive Strength, Chemical Resistance, Etchability, Silane Coupling Agent

Description

Method for manufacturing surface-treated copper foil for PCB having fine-circuit pattern and surface-treated copper foil

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to surface-treated copper foil for printed circuit boards, and more particularly, to a method for producing a surface-treated copper foil for microcircuit boards suitable for the production of a substrate having a fine circuit pattern having a circuit width of 20 µm or less.

Background Art Conventionally, surface-treated copper foil has been widely used as a base material of printed circuit boards used in the fields of the electric and electronic industries. In general, the surface-treated copper foil is used in the manufacture of a printed circuit board by joining a polymer insulating substrate such as a glass-epoxy substrate, a phenol substrate, a polyimide, or the like by hot press molding.

As the most basic characteristic required for such a copper foil, it is required to have excellent adhesive strength between the copper foil and the insulating base substrate. In particular, the copper foil must maintain the adhesive strength above the required characteristics not only immediately after heating and pressing and laminating with an insulating substrate, but also after various treatments in subsequent post-processing steps. To this end, the chemical resistance, heat resistance, and the like to acids, alkalis, and the like should be excellent. In addition, in the etching process for forming the circuit pattern to form a printed wiring board, it is required that the etching residual material be excellent in etching property such as not remaining in the non-pattern portion.

In order to improve the adhesive strength of copper foil, the process of increasing the surface area of copper foil surface is normally used by performing what is called roughening process which precipitates fine copper particle on the copper foil surface. However, even if the roughening treatment alone can improve the adhesive strength, it does not prevent the adhesive strength from being degraded by various chemicals or heat in subsequent processes. In order to overcome this, various post-treatment steps are performed, such as forming a zinc film after the roughening treatment, and forming an anti-corrosive treatment layer of an electrolytic chromate layer and a silane coupling agent treatment layer.

On the other hand, in recent years, due to the high density, high performance, and miniaturization of electronic components, substrate circuits used are also high in density and accordingly, miniaturization of circuit widths is required. For this reason, copper foil for printed circuit boards is also required to have fine roughness so as to be suitable for forming such a fine circuit width pattern.

However, when the roughness of the roughened layer becomes fine, there is a contradiction that not only the adhesive strength of the surface of the copper foil is lowered, but also the required properties required for the copper foil are difficult to be achieved.

Therefore, in order to improve the various characteristics required for copper foil while having a fine roughness, much research is performed. For example, Cu-Ni (Japanese Patent Laid-Open No. 52-145769 and Japanese Patent Laid-Open No. 55-058502), Cu-Co-based (Japanese Patent Laid-Open No. 58-028893, Japanese Patent Laid-Open No. 2-292895), Cu-Co-Ni-based (Japanese Patent Application Laid-Open No. 02-292894) and the like.

However, the above-described conventional techniques, although fine roughening treatment is possible, use Cu as an alloy theme, and thus partially improve the above characteristics required as copper foil for a printed circuit board, and further improve acid resistance and alkali resistance. It was not possible to evenly improve the overall required properties such as chemical resistance, heat resistance and etching resistance. Therefore, in order to improve the overall required characteristics, a separate additional plating process or post-treatment process was required, and thus there was a disadvantage in that productivity was lowered and manufacturing cost was increased.

An object of the present invention is to provide a method for producing a surface-treated copper foil for a microcircuit board which can improve overall the properties required for a printed circuit board while having a fine roughness suitable for a microcircuit board.

In order to achieve the above object, the method for producing a surface-treated copper foil for a microcircuit board of the present invention,

Placing copper foil as a cathode in an electroplating bath containing Co, Ni, ammonium salt and citric acid, and depositing a roughened layer of Co—Ni alloy on the surface of the copper foil so that the surface roughness is 0.5 μm or less;

Forming a pure Zn or Zn alloy coating layer on the roughened layer;

Forming an electrolytic chromate layer on the coating layer;

Forming a silane coupling agent treatment layer on the electrolytic chromate layer;

Characterized in that comprises a.

It is preferable that the said electroplating bath contains Co: 1-40 g / l, Ni: 0.1-40 g / l, ammonium salt: 5-50 g / l, citric acid: 5-100 g / l.

In addition, the electroplating bath additionally includes one or more of Fe, Zn, Cr, Mo, W, V, Mn, Ti, Sn, Co, Ni essentially include Fe, Zn, Cr, Mo, W It is also preferable to form a roughened layer that additionally contains at least one of V, Mn, Ti, and Sn.

Hereinafter, the present invention will be described in detail.

The present invention can be applied to any type of copper foil such as electrolytic copper foil or rolled copper foil, and can be applied to both rigid and flexible printed circuit boards. In particular, according to the manufacturing method of the present invention, since the fine roughness can be achieved while satisfying all the required characteristics of the copper foil, it can be preferably used for the production of so-called copper foil laminated film (fccl) for flexible printed circuit boards requiring a fine circuit width. have.

In order to use fccl copper foil, it is required to have a roughened layer having roughness of at least 0.5 μm or less. In this case, when the roughness is lowered, required characteristics such as adhesive strength, chemical resistance, heat resistance, and etching resistance are required. There is a problem of deterioration.

The main feature of the present invention is that, unlike the prior art, the roughened layer is composed of nickel-cobalt alloy as essential, and the ammonium salt and citric acid are used as mediators of the electrolytic reaction so that the intrinsic properties of the nickel-cobalt alloy can be best expressed. The electrolytic plating is added to an electrolytic plating bath to provide a roughened layer having fine roughness and satisfying all the required characteristics of the copper foil.

Nickel improves chemical resistance and heat resistance, but when the roughening layer is formed of nickel alone, it is difficult to precipitate with fine roughness, and there is a disadvantage that residues are generated during alkali etching. In addition, cobalt is precipitated with fine roughness as opposed to nickel and has an advantage of good alkali etching, but there is a problem in that chemical resistance is deteriorated when cobalt is formed alone. Therefore, if nickel and cobalt are simultaneously added in an appropriate ratio, it is expected that all the required characteristics can be simultaneously satisfied. However, as described below, when a roughened layer is formed based only on nickel and cobalt, fine roughening treatments as desired can be achieved. Not only was the layer not formed, but it was found that the adhesive strength did not improve as expected, and there were problems in chemical resistance and etching resistance.

The present inventors have studied diligently to improve the results, and when the ammonium salt and citric acid are added to the electroplating bath, the effect of nickel and cobalt can be expressed to the maximum, thereby forming a roughened layer of fine roughness with various characteristics significantly improved. I figured it out.

The ammonium salt is thought to play a role in causing the nickel-cobalt alloy to be precipitated in the form of finer nodule by being involved in the electrolytic precipitation reaction path of nickel and cobalt, and more evenly in the nodule. The type of ammonium salt that can be applied is not particularly limited, and for example, ammonium sulfate, ammonium chloride, ammonium acetate salt and the like can be used.

In addition, citric acid is a metal ions such as ammonium salt and nickel or cobalt to form a stable complex and serves to improve the heat resistance. Citric acid as a complexing agent has particular suitability as a chemical reaction aid of nickel-cobalt and ammonium salts, and is believed to play a role in helping the nodule of nickel-cobalt formed by the ammonium salt to be firmly attached to the copper foil. Examples of citric acid suitable for the present invention include sodium citrate, potassium citrate, ammonium citrate, diammonium citrate, and ammonium ferric citrate.

On the other hand, for the purpose of adding physical or mechanical properties necessary for copper foil, such as further improving the etching resistance and chemical resistance, or for improving the peel strength between the transparent substrate and the copper foil, Fe, Zn in addition to Co, Ni, etc. One or more components of Cr, Mo, W, V, Mn, Ti, Sn may be additionally added to the plating bath. For example, when Fe or Zn is included in the blackening plating layer, the adhesive strength with the PET substrate is improved, and the etching rate is also relatively fast.

The composition of the preferred electroplating bath used to form the roughened layer according to the present invention is as follows, but is not particularly limited.

Co metal ion concentration: 1 ~ 40 g / l

Ni metal ion concentration: 0.1 ~ 40 g / l

Concentration of other metal ions: 0.001 ~ 5 g / l

Ammonium salts; 5-50 g / l

Sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 5 ~ 100 g / l

When the roughening layer is formed using the plating bath of the above composition, there is an advantage that a more uniform roughening layer is formed.

In addition, the electrolytic conditions are to be delivered in the vicinity of the limit current density of the plating bath so that the roughening layer can be formed, it is also preferable to select generally in the following range from the viewpoint of forming a uniform roughening treatment layer.

pH: 2 ~ 6

Plating solution temperature: 20 ~ 60 ℃

Current density: 1 ~ 50 A / dm ²

Processing time; 1-20 seconds

On the other hand, in order to prevent heat discoloration, a pure Zn or Zn alloy coating layer is deposited on the roughened layer. Examples of the available Zn alloys include Zn-Ni, Zn-Mo, Zn-Cr, Zn-CO, Zn-Ni-Co, Zn-Ni-Mo, Zn-Co-Mo and the like. The coating layer formation conditions can be selected and used under conditions which are usually used, but are not particularly limited, and more preferable effects can be obtained, for example, under the following conditions.

Electrolytic bath composition;

Zn metal ion: 0.5 ~ 15 g / l, other metal ion: 0.1 ~ 10 g / l

pH; 3.0-4.0

Temperature ; Room temperature

Current Density: 0/1 ~ 3 A / dm

Processing time: 1-4 seconds

In addition, after formation of the Zn coating layer, ordinary anticorrosive treatment layers such as an electrolytic chromate layer and a silane coupling agent treatment layer are formed to complete the surface-treated copper foil for a microcircuit board according to the present invention.

The chromate treatment conditions can be selected and used under ordinary treatment conditions, and are not particularly limited. For example, the chromate treatment conditions can provide more preferable effects.

CrO ₃ concentration in electrolytic bath: 0.1 ~ 10 g / l,

PH of electrolyte: 4.0 ~ 5.0

Electrolyte Temperature: Room Temperature

Current Density: 0.2 ~ 2 A / dm

Processing time: 2 ~ 5 seconds

When chromate treatment is performed, a rustproof layer of chromium hydroxide and chromium oxide is formed thinly.

The silane coupling agent treatment is performed by, for example, diluting 0.005 to 2 wt% of the silane coupling agent in water, applying it on a chromate layer, and drying it.

Example

Example 1

A rolled copper foil having a surface roughness Rz of 1.0 µm or less and a thickness of 18 µm was used. Electrolytic alkali degreasing was performed on the copper foil surface, immersed in 100 g / l sulfuric acid for 10 seconds, washed with pure water, and a roughened layer was formed under the following conditions. Thereafter, the surface of the roughened layer was subjected to Zn coating layer formation, Cr rust prevention treatment, and silane coupling treatment sequentially.

<Condition Formation Conditions>

Electrolytic bath composition:

Co metal ion (CoS0 ₄ ㆍ 7H ₂ O) concentration: 5 g / l, Ni metal ion (NiS0 ₄ ㆍ 6H ₂ O) concentration: 2 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l

pH: 5.4

Temperature of electrolyte: 25 ℃

Current density: 25 A / dm ²

Plating time: 8 seconds

<Zn film layer formation condition>

ZnSO ₄ ㆍ H ₂ O: 5 g / l

pH: 3.0

Temperature: Room temperature

Current density: 1 A / dm

Processing time: 4 seconds

<Chromate Antirust Treatment Condition>

CrO ₃ concentration: 5 g / l

pH: 5.0

Temperature: Room temperature

Current density: 0.5 A / dm

Processing time: 4 seconds

<Silane coupling process conditions>

After chromate rust treatment, a 3-glycidoxy propyltrimethoxy silane 0.1 wt% aqueous solution was applied by spraying and then dried in a 150 ^° C. drying furnace for 30 seconds.

Example 2

Except the conditions for forming the roughened layer described below, the type of copper foil used, pretreatment conditions such as degreasing, pickling and washing and other surface treatment conditions (Zn film layer formation, chromate treatment and silane coupling agent treatment conditions) are the same as in Example 1. .

<Condition Formation Conditions>

Electrolytic bath composition:

Co metal ion (CoS0 ₄ ㆍ 7H ₂ O) concentration: 6 g / l, Ni metal ion (NiS0 ₄ ㆍ 6H ₂ O) concentration: 0.5 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l

pH: 5.4

Temperature of electrolyte: 25 ℃

Current density: 20 A / dm ²

Plating time: 10 seconds

Example 3

Except the conditions for forming the roughened layer described below, the type of copper foil used, pretreatment conditions such as degreasing, pickling and washing and other surface treatment conditions (Zn film layer formation, chromate treatment and silane coupling agent treatment conditions) are the same as in Example 1. .

<Condition Formation Conditions>

Electrolytic bath composition:

Co metal ion (CoS0 ₄ ㆍ 7H ₂ O) concentration: 6 g / l, Ni metal ion (NiS0 ₄ ㆍ 6H ₂ O) concentration: 1 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l

pH: 5.4

Temperature of electrolyte: 25 ℃

Current density: 22 A / dm ²

Plating time: 10 seconds

Example 4

Except the conditions for forming the roughened layer described below, the type of copper foil used, pretreatment conditions such as degreasing, pickling and washing and other surface treatment conditions (Zn film layer formation, chromate treatment and silane coupling agent treatment conditions) are the same as in Example 1. .

<Condition Formation Conditions>

Electrolytic bath composition:

Concentration of Co metal ion (CoS0 ₄ ㆍ 7H ₂ O): 5 g / l, Concentration of Ni metal ion (NiS0 ₄ ㆍ 6H ₂ O): 2 g / l, Fe metal ion (FeS0 ₄ ㆍ 7H ₂ O) Concentration: 1 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l

pH: 5.4

Temperature of electrolyte: 25 ℃

Current density: 25 A / dm ²

Plating time: 8 seconds

Example 5

Except the conditions for forming the roughened layer described below, the type of copper foil used, pretreatment conditions such as degreasing, pickling and washing and other surface treatment conditions (Zn film layer formation, chromate treatment and silane coupling agent treatment conditions) are the same as in Example 1. .

<Condition Formation Conditions>

Electrolytic bath composition:

Concentration of Co metal ion (CoS0 ₄ ㆍ 7H ₂ O): 5 g / l, Concentration of Ni metal ion (NiS0 ₄ ㆍ 6H ₂ O): 2 g / l, Zn metal ion (ZnS0 ₄ ㆍ H ₂ O) Concentration: 1 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ㆍ 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l

pH: 5.4

Temperature of electrolyte: 25 ℃

Current density: 25 A / dm ²

Plating time: 8 seconds

Comparative Example 1

Except that ammonium sulfate was not included in the plating bath among the roughening layer forming conditions of Example 1, the remaining conditions were the same as in Example 1.

Comparative Example 2

Except that sodium citrate was not included in the plating bath among the roughening layer forming conditions of Example 1, the remaining conditions were the same as in Example 1.

Comparative Example 3

Except that Ni was not included in the plating bath among the roughening layer forming conditions of Example 1, the remaining conditions were the same as in Example 1.

[Comparative Example 4]

Except that Co was not included in the plating bath among the roughening layer forming conditions of Example 1, the remaining conditions were the same as in Example 1.

Table 1 shows the result of measuring and comparing various required characteristics with the following test conditions with respect to an Example and a comparative example.

division Characteristic test result Adhesion Strength (kgf / cm) Heat resistance adhesive strength (kgf / cm) HCl resistance KCN resistance Self-resistance Alkali etching Example One 0.95 0.73 ○ ○ ○ ○ 2 0.94 0.75 ○ ○ ○ ○ 3 0.96 0.74 ○ ○ ○ ○ 4 1.01 0.74 ○ ○ ○ ○ 5 1.04 0.76 ○ ○ ○ ○ Comparative example One 0.68 0.49 ○ △ X X 2 0.85 0.57 ○ ○ X △ 3 0.85 0.52 X △ X ○ 4 0.76 0.51 ○ ○ △ X

* Characteristic test condition

ｏAdhesive strength: Epoxy resin impregnated base material and copper foil non-smooth surface are laminated to laminate and test piece is 10mm wide and measured by using adhesive tester (Universal Test Machine: UTM).

ｏ Heat-resistant adhesive strength: Measure the adhesive strength after baking for 240 hours in 177 ℃ Dry oven.

ｏ HCl resistance: 18%-Degradation rate of adhesion strength after 1 hour immersion in HCl.

ｏ KCN resistance: 10%-Determination of adhesive strength deterioration rate after immersion in KCN for 30 minutes.

ｏ Loss in after boiling in water: Adhesion strength deterioration rate is measured after 2 hours immersion in H ₂ O at 100 ℃

<HCl resistance, KCN resistance, self-resistance evaluation criteria>

 ○: degradation rate before and after immersion is 5% or less

△: degradation rate before and after immersion is 5 to 25% or less

     X: deterioration rate before and after immersion is 25% or more

Alkali etching property: The residual copper which remained in the base material in the range of 10 dm <2> after 8 minute immersion in the etching liquid of pH 9.7-10.2, specific gravity 1.19-1.21 at 50 degreeC conditions was observed using the optical microscope.

<Alkali Etchability Evaluation Criteria>

○: There is no residual copper or alloy layer remaining on the substrate after etching.

(Triangle | delta): There exists some residual copper or an alloy layer which remain | survives in a base material after an etching.

X: There are many residual copper or alloy layers which remain in a base material after an etching.

As shown in the table, in the embodiment of the present invention, it can be seen that the chemical resistance, heat resistance and alkali etching resistance, such as adhesive strength, heat resistance (heat resistance strength), hydrochloric acid resistance, potassium cyanide resistance and the like evenly.

On the other hand, in the case of a comparative example in which at least one of the essential constituents of the roughening layer according to the manufacturing method of the present invention is omitted, it can be seen that at least one of the above characteristics is inferior to the embodiment of the present invention. For example, in terms of adhesive strength and heat-resistant adhesive strength, the inventive examples were improved by at least 9.6% and 21.9%, respectively, compared to the comparative examples.

As described above, the surface-treated copper foil manufactured by the manufacturing method of the present invention has excellent overall characteristics required as the copper foil such as adhesive strength with the substrate, heat-resistant adhesive strength, chemical resistance, and etching resistance, and thus, fine circuit boards. It is very suitable as a copper foil.

Claims (4)

Placing copper foil as a cathode in an electroplating bath containing Co, Ni, ammonium salt and citric acid, and depositing a roughened layer of Co—Ni alloy on the surface of the copper foil so that the surface roughness is 0.5 μm or less; Forming a pure Zn or Zn alloy coating layer on the roughened layer; Forming an electrolytic chromate layer on the coating layer; Forming a silane coupling agent treatment layer on the electrolytic chromate layer; Method for producing a surface-treated copper foil for a fine circuit board, characterized in that comprising a. The method of claim 1, Electrolytic plating bath, Co: 1 ~ 40 g / l, Ni: 0.1 ~ 40 g / l, ammonium salt: 5 ~ 50 g / l, citric acid: 5 ~ 100 g / l for a microcircuit board Method for producing surface treated copper foil. The method of claim 1, One or more components of Fe, Zn, Cr, Mo, W, V, Mn, Ti, and Sn are additionally included in the electroplating bath, and essentially include Co, Ni, and Fe, Zn, Cr, Mo, W, V. A method for producing a surface-treated copper foil for a microcircuit board, characterized in that a roughened layer further comprising at least one component of Mn, Ti, Sn is formed. A surface-treated copper foil for a microcircuit board, which is produced by the method of any one of claims 1 to 3.