JP2006028635A - Method for manufacturing surface treated copper foil for microfabrication circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing copper foil having excellent strength of adhesion to a substrate and heat resistance strength. <P>SOLUTION: The method for manufacturing the surface treated copper foil for a microfabrication circuit substrate suitable for production of the substrate having a microfabrication circuit pattern comprises steps of; arranging the copper foil as a cathode in an electroplating bath including Co, Ni, ammonium salt, and citric acid and precipitating and forming a roughening treatment layer of a Co-Ni alloy on the copper foil surface in such a manner that its surface roughness attains ≤0.5 μm; forming a pure Zn or Zn alloy coating layer on the roughening treatment layer; forming an electrolytic chromate layer on the coating layer; and forming a silane coupling agent treatment layer on the electrolytic chromate layer. The manufactured surface treated copper foil is excellent overall in the requirement characteristics as the copper foil, such as the strength of adhesion to the substrate, heat resistant strength of adhesion, chemical resistance, and etching, and is particularly suitable as the copper foil for the microfabrication circuit substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-treated copper foil for a printed circuit board, and more particularly to a method for producing a surface-treated copper foil for a fine circuit board suitable for producing a board having a fine circuit pattern having a circuit width of 20 μm or less.

Conventionally, surface-treated copper foil has been widely used as a basic material for printed circuit boards used in the fields of the electrical and electronic industries. In general, the surface-treated copper foil is hot press-molded and joined with a polymer insulating base material such as a glass-epoxy base material, a phenol base material, or polyimide, and is used as a copper clad laminate to produce a printed circuit board. used.
As the most basic characteristic required for such a copper foil, it is required that the adhesive strength between the copper foil and the insulating base substrate is excellent. In particular, the copper foil must maintain its adhesive strength beyond the required characteristics not only immediately after being heated and pressed with an insulating base material and laminated, but also after various treatments in the subsequent post-treatment process. For that purpose, the chemical resistance, heat resistance, etc. with respect to an acid, an alkali, etc. must be excellent. Furthermore, in an etching process for forming a copper circuit pattern to form a printed wiring board, it is required to have excellent etching properties such that an etching residual material does not remain in a non-pattern portion.

In order to improve the adhesive strength of the copper foil, a process of increasing the surface area of the copper foil surface by performing a so-called “roughening treatment” in which fine copper particles are deposited on the surface of the copper foil is usually used. However, even if simple roughening treatment can improve the adhesive strength, it cannot prevent the adhesive strength from being deteriorated by various chemicals or heat in the subsequent steps. In order to overcome this, after the roughening treatment, various post-treatment steps such as forming a zinc layer coating and forming an anti-rust treatment layer of an electrolytic chromate layer and a silane coupling agent treatment layer are performed. .
On the other hand, recently, with the increase in density, performance, and miniaturization of electronic components, the substrate circuit to be used is also increased in density, and accordingly, the circuit width is required to be reduced. For this reason, the copper foil for printed circuit boards is also required to have a fine roughness so as to be suitable for forming such a fine circuit width pattern.

However, if the roughness of the roughened layer becomes fine, not only the adhesive strength of the copper foil surface is inferior, but also a contradiction arises that it is difficult to achieve various required characteristics required for the copper foil.
Therefore, many studies have been conducted to improve various characteristics required for copper foil while having fine roughness. For example, the technique etc. which form the alloy roughening process layer of Cu-Ni system (patent documents 1 and 2), Cu-Co system (patent documents 3 and 4), Cu-Co-Ni system (patent documents 5), etc. are mentioned. It is done.
However, in the above disclosed prior art and the like, a fine roughening treatment is possible, but since Cu is used as an alloy main material, it is required as a copper foil for a printed circuit board as described above. However, it was not possible to improve the required properties such as chemical resistance such as acid resistance and alkali resistance, heat resistance and etching property in a uniform manner by only partially improving the various characteristics. For this reason, in order to improve the overall required characteristics, a separate additional plating step or post-treatment step is required, which has the disadvantages that the productivity is lowered and the manufacturing unit price is increased.

JP 52-145769 A JP 55-0585502 JP 58-028883 JP 02-292895 JP 02-292894

  The present invention provides a method for producing a surface-treated copper foil for a fine circuit board that can improve overall characteristics required for a printed circuit board while having a fine roughness suitable for a fine circuit board. For the purpose.

In order to solve the above-described problems, a method for producing a surface-treated copper foil for a fine circuit board according to the present invention includes disposing a copper foil at a cathode in an electrolytic plating bath containing Co, Ni, ammonium salt and citric acid, Depositing a Co—Ni alloy roughening layer on the surface of the copper foil to a degree of 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 layer on the electrolytic chromate layer;
It is characterized by including.
The electrolytic plating bath preferably contains Co: 1 to 40 g / l, Ni: 0.1 to 40 g / l, ammonium salt: 5 to 50 g / l, and citric acid: 5 to 100 g / l.
Further, the electrolytic plating bath additionally includes one or more components among Fe, Zn, Cr, Mo, W, V, Mn, Ti, and Sn, and essentially includes Co and Ni, Fe, Zn It is preferable that a roughening layer containing one or more components of Cr, Mo, W, V, Mn, Ti, and Sn is additionally formed.

  The surface-treated copper foil produced by the production method of the present invention is generally excellent in the required properties as a copper foil, such as adhesion strength to a substrate, heat-resistant adhesion strength, chemical resistance, and etching property. It is very suitable as a copper foil for substrates.

The present invention will be described in detail below.
The present invention can be applied regardless of the type of copper foil such as electrolytic copper foil or rolled copper foil, and can be applied to all hard and soft printed circuit boards. In particular, according to the manufacturing method of the present invention, a fine roughness can be achieved while satisfying all the required characteristics of the copper foil, so a so-called copper foil laminated film (FCCL for flexible printed circuit board) that requires a fine circuit width is required. ) Can be preferably used.
In order to be used for the copper foil for FCCL, it is required that at least a roughening treatment layer having a roughness of 0.5 μm or less is provided. Further, there is a problem that required properties such as adhesive strength, chemical resistance, heat resistance, and etching property deteriorate.
The main feature of the present invention is that, unlike the prior art, the roughened layer is constituted so that a nickel-cobalt alloy is essentially contained as a main agent, and the inherent characteristics of such a nickel-cobalt alloy are maximized. As described above, the addition of ammonium salt and citric acid to the electrolytic plating bath as a mediator of the electrolytic reaction, and by electroplating, roughening treatment that satisfies the various required characteristics of copper foil while having fine roughness This is because a layer is formed.

  Nickel improves chemical resistance and heat resistance, but when a roughened layer is formed with nickel alone, it is difficult to deposit with a fine roughness, and there is a disadvantage that a residue is generated during alkali etching. . Furthermore, cobalt has the advantage that it is precipitated with a fine roughness, contrary to nickel, and has good alkali etching properties. However, when a roughened layer is formed with cobalt alone, the chemical resistance is deteriorated. There's a problem. Therefore, if nickel and cobalt are added at an appropriate ratio at the same time, it is expected that various required characteristics can be satisfied at the same time. However, as will be described later, the roughened layer is actually composed mainly of nickel and cobalt. In the case of forming the film, not only a fine roughening layer as fine as desired is formed, but also the adhesive strength is not improved as expected, and there is a problem in chemical resistance, etching property, and the like.

As a result of intensive studies to improve these problems, the present inventors have made various effects remarkable by maximizing the effects of nickel and cobalt by adding ammonium salt and citric acid to the electrolytic plating bath. It was found that a roughened layer having an improved fine roughness can be formed.
The ammonium salt is involved in the electrolytic deposition reaction path of nickel and cobalt, so that the nickel-cobalt alloy is deposited in a finer nodule form, and further, the nodule is deposited more uniformly. It seems to do. The kind of ammonium salt that can be applied is not particularly limited, and for example, ammonium sulfate, ammonium chloride, ammonium acetoate and the like can be used.
Further, citric acid plays a role of improving heat resistance by forming a complex compound in which an ammonium salt and metal ions such as nickel and cobalt are stabilized. As a complexing agent, citric acid has particular suitability as a chemical reaction aid for nickel-cobalt and ammonium salts so that the nickel-cobalt nodule formed by the ammonium salt is firmly attached to the copper foil. It is thought to play a role to help. Citric acid suitable for the present invention includes sodium citrate, potassium citrate, ammonium citrate, diammonium citrate, ammonium ammonium citrate and the like.

On the other hand, for the purpose of adding physical properties or mechanical properties necessary for copper foil, such as further improving etching properties and chemical resistance, and for the purpose of improving the peel strength between the transparent substrate and copper foil, In addition to Co and Ni, one or more components among Fe, Zn, Cr, Mo, W, V, Mn, Ti, and Sn can be additionally added to the plating bath. For example, when Fe or Zn is contained in the blackened plating layer, there is an advantage that the adhesive strength with the PET base material is improved and the etching rate is relatively fast.
Although the composition of the preferable electrolytic plating bath used in order to form the roughening process layer by this invention is as follows, it is not limited to these.
Co metal ion concentration: 1 to 40 g / l
Ni metal ion concentration: 0.1 to 40 g / l
Other metal ion concentrations: 0.001 to 5 g / l
Ammonium salt: 5-50 g / l
Sodium citrate _{(C 6 H 5 Na 3 O} 7 · 2H 2 O): 5~100g / l
Forming a roughened layer using a plating bath having the above composition has an advantage of forming a more uniform roughened layer.

Furthermore, the electrolytic conditions are such that the roughened layer can be formed and electrolysis is performed near the limit current density of the plating bath. From the viewpoint of forming a uniform roughened layer, the following conditions are preferably selected.
pH: 2-6
Plating solution temperature: 20-60 ° C
Current density: 1 to 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 roughening layer. Examples of the soluble Zn alloy 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 from the conditions normally used, but are not limited to these conditions. For example, the following conditions can provide a more favorable effect. .
Electrolytic bath composition:
Zn metal ions: 0.5 to 15 g / l, other metal ions: 10 g / l or less pH: 3.0 to 4.0
Temperature: Room temperature Current density: 0.1-3 A / dm ²
Processing time: 1-4 seconds

Furthermore, after forming the Zn coating layer, when a normal rust-proofing layer such as an electrolytic chromate layer and a silane coupling agent-treated layer is formed, the surface-treated copper foil for a fine circuit board according to the present invention is completed.
The chromate treatment conditions can be selected and used from normal treatment conditions and are not particularly limited. For example, if the conditions are as follows, a more preferable effect can be obtained.
CrO ₃ concentration in the electrolytic bath: 0.1 to 10 g / l,
Electrolyte pH: 4.0-5.0
Electrolyte temperature: normal temperature current density: 0.2-2 A / dm ²
Treatment time: 2 to 5 seconds When the chromate treatment is performed, a rust preventive layer composed of chromium hydroxide and chromium oxide is thinly formed.
The silane coupling agent treatment is performed, for example, by diluting 0.005 to 2 wt% of a silane coupling agent in water, applying the silane coupling agent on the chromate layer, and drying.

The following examples illustrate the invention but are not intended to limit the invention.

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

<Roughening layer formation conditions>
Electrolytic bath composition:
The concentration of Co metal ions _{(CoSO 4 · 7H 2 O)} : 5g / l, the concentration of Ni metal ions _{(NiSO 4 · 6H 2 O)} : 2g / l, sodium citrate _{(C 6 H 5 Na 3 O} 7 · 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) 2 SO ₄ ): 15 g / l
pH: 5.4
Electrolyte temperature: 25 ° C
Current density: 25 A / dm ²
Plating time: 8 seconds

<Zn coating layer formation conditions>
ZnSO ₄ · H ₂ O: 5 g / l
pH: 3.0
Temperature: normal temperature current density: 1 A / dm ²
Processing time: 4 seconds

<Chromate rust prevention treatment conditions>
CrO ₃ concentration: 5 g / l
pH: 5.0
Temperature: Normal temperature Current density: 0.5 A / dm ²
Processing time: 4 seconds
<Silane coupling treatment conditions>
After the chromate rust prevention treatment, a 0.1 wt% aqueous solution of 3-glycidoxypropyltrimethoxysilane was applied by spraying and then dried in a drying oven at 150 ° C. for 30 seconds.

Except for the following roughening treatment layer formation conditions, the same copper foil type as in Example 1, pretreatment conditions such as degreasing, pickling and washing, and other surface treatment conditions (Zn coating layer formation, chromate treatment and silane coupling) The same treatment as in Example 1 was performed using the agent treatment conditions.
<Roughening layer formation conditions>
Electrolytic bath composition:
Co metal ion (CoSO ₄ .7H ₂ O) concentration: 6 g / l, Ni metal ion (NiSO ₄ .6H ₂ O) concentration: 0.5 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ) · 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) 2 SO ₄ ): 15 g / l
pH: 5.4
Electrolyte temperature: 25 ° C
Current density: 20 A / dm ²
Plating time: 10 seconds

Except for the following roughening treatment layer formation conditions, the same copper foil type as in Example 1, pretreatment conditions such as degreasing, pickling and washing, and other surface treatment conditions (Zn coating layer formation, chromate treatment and silane coupling) The same treatment as in Example 1 was performed using the agent treatment conditions.
<Roughening layer formation conditions>
Electrolytic bath composition:
Co metal ion (CoSO ₄ .7H ₂ O) concentration: 6 g / l, Ni metal ion (NiSO ₄ .6H ₂ O) concentration: 1 g / l, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ). 2H ₂ O): 25 g / l, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ): 15 g / l
pH: 5.4
Electrolyte temperature: 25 ° C
Current density: 22 A / dm ²
Plating time: 10 seconds

Except for the following roughening treatment layer formation conditions, the same copper foil type as in Example 1, pretreatment conditions such as degreasing, pickling and washing, and other surface treatment conditions (Zn coating layer formation, chromate treatment and silane coupling) The same treatment as in Example 1 was performed using the agent treatment conditions.
<Roughening layer formation conditions>
Electrolytic bath composition:
Co metal ion (CoSO ₄ .7H ₂ O) concentration: 5 g / l, Ni metal ion (NiSO ₄ .6H ₂ O) concentration: 2 g / l, Fe metal ion (FeSO ₄ .7H ₅ O) concentration: 1 g / l, sodium citrate _{(C 6 H 5 Na 3 O} 7 · 2H 2 O): 25g / l, ammonium sulfate _{((NH 4) 2 SO 4} ): 15g / l
pH: 5.4
Electrolyte temperature: 25 ° C
Current density: 25 A / dm ²
Plating time: 8 seconds

Except for the following roughening treatment layer formation conditions, the same copper foil type as in Example 1, pretreatment conditions such as degreasing, pickling and washing, and other surface treatment conditions (Zn coating layer formation, chromate treatment and silane coupling) The same treatment as in Example 1 was performed using the agent treatment conditions.
<Roughening layer formation conditions>
Electrolytic bath composition:
Co metal ion (CoSO ₄ .7H ₂ O) concentration: 5 g / l, Ni metal ion (NiSO ₄ .6H ₂ O) concentration: 2 g / l, Zn metal ion (ZnSO ₄ .H ₂ O) concentration: 1 g / l, sodium citrate _{(C 6 H 5 Na 3 O} 7 · 2H 2 O): 25g / l, ammonium sulfate _{((NH 4) 2 SO 4} ): 15g / l
pH: 5.4
Electrolyte temperature: 25 ° C
Current density: 25 A / dm ²
Plating time: 8 seconds

Comparative Example 1
The surface treatment was performed in the same manner as in Example 1 except that ammonium sulfate was not included in the plating bath in the conditions for forming the roughened layer in Example 1.

Comparative Example 2
Surface treatment was performed in the same manner as in Example 1 except that sodium citrate was not included in the plating bath in the conditions for forming the roughened layer in Example 1.

Comparative Example 3
Surface treatment was performed in the same manner as in Example 1 except that the plating bath contained no Ni in the roughening treatment layer forming conditions of Example 1.

Comparative Example 4
The surface treatment was performed in the same manner as in Example 1 except that Co was not contained in the plating bath in the roughening treatment layer forming conditions of Example 1.

Table 1 shows the measurement results of various required characteristics in each Example and each Comparative Example.

Test conditions and evaluation criteria are shown below.
Adhesive strength: An epoxy resin-impregnated base material and a non-smooth surface of a copper foil were laminated to form a laminate, and the test piece was measured to have a width of 10 mm and measured using an adhesive strength measuring machine (Universal Test Machine: UTM).
Heat-resistant adhesive strength: After baking for 240 hours with Dry oven at 177 ° C., the adhesive strength was measured.

HCl resistance: After being deposited in 18% -KCl for 1 hour, the adhesive strength deterioration rate was measured.
KCN resistance: 10% -After being deposited in KCN for 30 minutes, the adhesive strength deterioration rate was measured.
Boil resistance (Loss in after boiling in water): After depositing in H ₂ O at 100 ° C. for 2 hours, the adhesive strength deterioration rate was measured.
<Evaluation criteria for HCl resistance, KCN resistance, and boiling resistance>
○: Deterioration rate before and after immersion is 5% or less Δ: Deterioration rate before and after immersion is 5% to 25% or less ×: Deterioration rate before and after immersion is 25% or more

Alkali etching property: After depositing in an etching solution having a pH of 9.7 to 10.2 and a specific gravity of 1.19 to 1.21 at a temperature of 50 ° C. for 8 minutes, the remaining copper remaining on the base material within the range of 10 dm ² is optical. Observation was performed using a microscope.
<Alkali etching property evaluation criteria>
○: There is no residual copper or alloy layer remaining on the substrate after etching.
Δ: After etching, there is some residual copper or alloy layer remaining on the substrate.
X: Many copper or alloy layers remain on the substrate after etching.

As shown in Table 1, in the case of the examples of the present invention, the chemical strength such as adhesive strength, heat resistance (heat resistant adhesive strength), hydrochloric acid resistance, potassium cyanide resistance, boiling resistance and alkali etching property are uniformly excellent. I understand that.
On the other hand, in the case of a comparative example in which one or more of the essential constituent requirements of the roughening treatment layer according to the production method of the present invention have been omitted, one or more of the above characteristics are inferior to the examples of the present invention. The cage. For example, in the adhesive strength and heat-resistant adhesive strength, the examples of the present invention are generally improved by 9.6% or more and 21.9% or more, respectively, as compared with the comparative example.

Claims (4)

A copper foil is placed on the cathode in an electrolytic plating bath containing Co, Ni, ammonium salt and citric acid, and a Co-Ni alloy roughening layer is formed 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 roughening layer, forming an electrolytic chromate layer on the coating layer, and a silane cup on the electrolytic chromate layer A method for producing a surface-treated copper foil for a fine circuit board, comprising the step of forming a ring agent-treated layer. The electrolytic plating bath includes Co: 1 to 40 g / l, Ni: 0.1 to 40 g / l, ammonium salt: 5 to 50 g / l, and citric acid: 5 to 100 g / l. Item 2. A method for producing a surface-treated copper foil for a fine circuit board according to Item 1. The electrolytic plating bath further includes at least one component selected from the group consisting of Fe, Zn, Cr, Mo, W, V, Mn, Ti, and Sn, and the roughening treatment layer includes Co and Ni. 3 or 3 and further comprising at least one component selected from the group consisting of Fe, Zn, Cr, Mo, W, V, Mn, Ti and Sn. Method for producing a surface-treated copper foil for a fine circuit board. The surface-treated copper foil for fine circuit boards manufactured by the manufacturing method as described in any one of Claims 1-3.