JP2739507B2 - Copper foil electrolytic treatment method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for electrolytically treating copper foil, and more particularly, to a method of using an electrolytic solution containing copper and zinc ions on at least a surface of a copper foil to be bonded to a resin. In the method of forming a coating layer consisting of, and laminating and bonding a copper foil on which the brass coating layer is formed to a resin, printing a required circuit on the copper foil, and forming a printed circuit by etching, a so-called circuit generated at the time of etching The present invention relates to a copper foil electrolytic treatment method capable of preventing the erosion (circuit erosion) phenomenon of an end portion.

[Prior Art] A copper foil for a printed circuit is generally laminated and adhered to a base material such as a synthetic resin under a high temperature and a high pressure, and thereafter, after printing a circuit necessary for forming a desired circuit, etching for removing an unnecessary portion is performed. Processing is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices.

Quality requirements for copper foil for printed wiring boards differ between an adhesive surface (so-called roughened surface) bonded to a resin substrate and a non-adhesive surface (so-called glossy surface), and it is important to satisfy both at the same time. .

The requirements for the roughened surface are mainly that there is no oxidative discoloration during storage, that the peel strength with the substrate is sufficient even after high-temperature heating, wet processing, soldering, chemical treatment, etc., lamination with the substrate And the absence of so-called layered spots occurring after etching.

On the other hand, the glossy surface must have good appearance, no oxidative discoloration during storage, good solder wettability, no oxidative discoloration when heated at high temperatures, and good adhesion to the resist. Etc. are required.

In order to respond to such demands, many processing methods have been proposed for copper foil for printed wiring boards.

Although the processing method differs between the rolled copper foil and the electrolytic copper foil, there is a method described below as an example of the processing method of the electrolytic copper foil.

That is, first, in order to increase the adhesive force (peel strength) between copper and resin, fine particles made of copper and copper oxide are applied to the surface of the copper foil (roughening treatment), and then brass or zinc or the like is applied to impart heat resistance. A heat-resistant coating layer (barrier layer) is formed. Finally, in order to prevent surface oxidation etc. during transportation or storage, immersion or electrolytic chromate treatment or electrolytic chromium
The product is made by performing rust prevention treatment such as zinc treatment.

Among them, the treatment method for forming the heat-resistant coating layer is particularly important for determining the surface properties of the copper foil. For this reason, many examples of metals or alloys forming the heat-resistant coating layer, such as Zn, Cu-Ni, Cu-Co, and Cu-Zn, have been put to practical use.

Among them, the copper foil with a heat-resistant coating layer made of Cu-Zn (brass) has no resin layer stain when laminated on a printed circuit board made of epoxy resin, etc., and has a peel strength after high temperature heating. It is widely used industrially because of its excellent properties such as little degradation of

The method of forming the heat-resistant coating layer made of brass is described in detail in JP-B-51-35711 and JP-B-54-6701.

[Problem to be Solved by the Invention] The copper foil on which the heat-resistant coating layer made of brass is formed,
It is then etched to form a printed circuit.
Recently, hydrochloric acid-based etchants have been increasingly used for forming printed circuits.

However, a printed circuit board using a copper foil on which a heat-resistant coating layer made of brass is formed is subjected to a hydrochloric acid-based etchant (eg,
When etching is performed with CuCl ₂ , FeCl _3, etc., there is a problem that so-called erosion of the circuit edge (circuit erosion) occurs on both sides of the circuit pattern, and the peel strength from the resin base material is deteriorated. .

The circuit erosion phenomenon is that the adhesive boundary layer between the copper foil and the resin substrate of the circuit formed by the above-mentioned etching treatment, that is, the brass coating layer is eroded from the exposed etching side surface by the hydrochloric acid-based etchant, and furthermore. In addition, it is a phenomenon in which both sides, which usually exhibit yellow (because of brass), are eroded due to insufficient washing with water and then exhibit red, and the peel strength of the portion is significantly deteriorated.

If this phenomenon occurs on the entire surface of the circuit pattern, the circuit pattern peels off from the substrate, which is a serious problem.

An object of the present invention is to develop a method for electrolytically treating a copper foil for forming a brass coating layer that avoids such circuit erosion without deteriorating other characteristics.

More specifically, an object of the present invention is to hardly cause a resin layer to stain when laminated on a resin substrate, to reduce properties such as little deterioration in peel strength after high-temperature heating, and to use a hydrochloric acid-based etching solution. An object of the present invention is to establish a copper foil electrolytic treatment technique that can completely prevent circuit erosion even when used.

[Means for solving the problem] The cause of this phenomenon is that when a hydrochloric acid-based etchant is used, cuprous chloride (CuCl) having low solubility is generated in the reaction process, and this is caused by the surface of the base material. It is thought that the main cause is the so-called dezincification of brass, which reacts with zinc in brass when deposited on the surface and elutes as zinc chloride. The estimated reaction formula is as follows.

2CuCl + Zn (zinc in brass) → ZnCl ₂ + 2Cu ゜ (copper in dezinced brass) In order to solve the above problems, the present inventors have conducted intensive studies on the conditions for forming the brass coating layer, and found that zinc A content of 15 to 30% by weight and a coating layer made of brass with an electrical quantity of 30 to 60 A · s / dm ² completely prevent circuit erosion without lowering other required characteristics. I found what I could do.

Based on this finding, the present invention provides a copper foil formed by forming a coating layer made of brass using an electrolytic solution containing copper and zinc ions on at least a bonding surface of the copper foil with a resin, and forming the brass coating layer. In a method of printing a required circuit on a copper foil and forming a printed circuit by etching, wherein a method of electrolytically treating a copper foil to prevent circuit erosion during etching, Reduce the zinc content of the coating layer to 15
-30% by weight, and the brass coating layer has an electric quantity of 30-60 A · s
The present invention provides a method for electrolytically treating a copper foil, wherein the copper foil is formed at / dm ² .

In particular, it is customary to form the brass coating layer after performing a roughening treatment on an adhesive surface of the copper foil with the resin. As an example, the brass coating layer uses a cyan electrolyte containing copper ions 42.5 to 85 g / and zinc ions 0.6 to 5.6 g /,
It is formed by plating at a current density of 1 to 10 A / dm ² for 1 to 10 seconds.

[Specific Description of the Invention] Next, the present invention will be described specifically and in detail to facilitate understanding of the present invention.

The copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil.

Usually, for the purpose of improving the peel strength of the copper foil after lamination on at least one surface of the copper foil, the surface of the degreased copper foil is subjected to a roughening process of performing, for example, copper-like bumpy electrodeposition. . Such a bumpy electrodeposition of copper is easily provided by so-called burnt electrodeposition. Normal copper plating may be performed as pretreatment before roughening and normal copper plating as finishing treatment after roughening. Roughening treatment by other known methods can also be performed.

An example of an electrolytic solution and electrolytic conditions for performing the above-described roughening treatment will be described below for reference.

Cu plating (roughening _{treatment) Cu: 10~50g / H 2 SO} 4: 50~150g / Temperature: 20 to 40 ° C. Current density: 10 to 100 A / dm between ^2:00: 1-5 seconds then the present invention The characteristic brass plating is performed on at least one surface of the copper foil. When the above-mentioned roughening treatment is performed, the brass layer needs to substantially uniformly cover the galvanized electrodeposited surface made of copper and copper oxide formed by the roughening treatment.

In order to completely prevent the circuit erosion phenomenon without deteriorating characteristics such as little stain of the resin layer when laminated on a resin base material and little deterioration of peel strength after high temperature heating, it is necessary to include zinc. It is important to form a coating layer made of brass with an amount of 15 to 30% by weight at an electric quantity of 30 to 60 A · s / dm ² . According to the invention, it has now been found for the first time that the zinc content and the quantity of electricity are closely related to the avoidance of the circuit erosion phenomenon. That is, even if the amount of electricity is 30 A · s / dm ² or more, the circuit erosion phenomenon cannot be avoided when the zinc content exceeds 30%, and when the amount of electricity is less than 30 A · s / dm ² , Regardless, circuit erosion cannot be completely prevented. That is, the circuit erosion cannot be completely prevented unless both the conditions of the electric quantity of 30 A · s / dm ² or more and the zinc content of 30% or less are not satisfied.

When the quantity of electricity is 30 A · s / dm ² or more, the zinc content is 15% or more when comprehensively determined taking into account other characteristics (for example, heat resistance, etc.) other than circuit erosion prevention. Preferably, it is 20% or more.

On the other hand, when the zinc content is less than 30%, the amount of electricity is 60 A · s / dm ² or less, preferably taking account of cost.
It is desirably 50 A · s / dm ² or less, more preferably about 40 A · s / dm ² .

By the way, the quantity of electricity (A · s / dm ² ) is the current density (A / d
m ² ) and the plating time in seconds (s). To obtain a predetermined amount of electricity, it is necessary to select an appropriate plating time according to the current density.

However, the current density cannot be uniquely determined because the optimal value is selected according to the copper foil production equipment and conditions, such as the plating tank solution flow rate and the plating solution composition,
Usually, it is 1 to 10 A / dm ² , preferably 4 to 8 A / dm ² . From the optimal value in this range, the plating time is selected so as to obtain a required amount of electricity.

In addition, the zinc content can be changed by adjusting the ratio of copper to zinc in the plating solution, so that it is necessary to appropriately select the zinc content according to the target zinc content.

The electrolytic solution and the electrolytic conditions of the above-mentioned brass plating are summarized below for the cyan-based electrolytic solution.

Brass (Cu-Zn) plating NaCN: 10 to 30 g / NaOH: 40 to 100 g / CuCN: 60 to 120 g / (copper ion 42.5 to 85 g /) Zn (CN) ₂ : 1 to 10 g / (zinc ion 0.6 to 5.6 g /) PH: 10 to 13 Temperature: 60 to 80 ° C Current density: 1 to 10 A / dm ² hours: 1 to 10 seconds Thereafter, to prevent oxidation of the copper foil on which the coating layer was formed, the copper foil was used. A rust-proof layer is formed on at least one surface of the substrate.

As the method for forming the rust preventive layer, all known methods can be applied to the present invention, but preferably, chromium oxide by immersion or electrolytic chromate treatment, or chromium oxide and zinc by electrolytic chromium-zinc treatment A rust prevention layer made of a mixture with zinc oxide is formed.

An example of electrolytic conditions and the like for forming the rustproof layer is described below for reference.

(A) Immersion chromate treatment K ₂ Cr ₂ O ₇ : 1 to 5 g / pH: 2.5 to 4.5 Temperature: 40 to 60 ° C Time: 3 to 8 seconds (b) Electrolytic chromate treatment K ₂ Cr ₂ O ₇ : 0.2 ~ 20g / acid: phosphoric acid, sulfuric acid, organic acid pH: 1.0 ~ 3.5 Temperature: 20 ~ 40 ℃ Current density: 0.1 ~ 5A / dm ² hours: 0.5 ~ 8 seconds (c) Electrolytic chromium / zinc treatment (alkaline bath _{) K 2 Cr 2 O 7 (} Na 2 Cr 2 O 7 or CrO _3): 2~10g / NaOH or KOH: 10~50g / ZnOH or _{ZnSO 4 · 7H 2 O: 0.05~10g} / pH: 7~13 bath Temperature: 20 to 80 ° C Current density: 0.05 to 5 A / dm ² hours: 5 to 30 seconds (d) Electrolytic chromium / zinc treatment (acid bath) K ₂ Cr ₂ O ₇ : _{2 to} 10 g / Zn: 0.2 to 0.5 g / Na ₂ SO ₄ : 5 ~ 20g / pH: 3.5 ~ 5.0 Bath temperature: 20 ~ 40 ° C Current density: 0.1 ~ 3.0A / dm ² hour: 1 ~ 30 seconds Next, examples and comparative examples will be described. .

[Examples and Comparative Examples] Using an electrolytic copper foil having a thickness of 35 μm prepared in advance,
First, a roughening treatment is performed on the roughened surface (M surface) of the copper foil to give fine particles composed of copper and copper oxide under the following electrolytic solution and electrolysis conditions. Using a liquid, by performing electrolysis by changing the amount of electricity, a heat-resistant coating layer made of brass having a different zinc content is formed on the roughened surface, and then electrolytic chromium / zinc treatment is performed to form the heat-resistant coating layer. It was applied to both sides of the formed copper foil to form a rustproof layer. (Note that the electrolytic solution and the electrolytic conditions were all the same, regardless of the change in the zinc content in the brass.) Cu plating (roughening treatment) Cu: 10 to 50 g / H ₂ SO ₄ : 50 to 150 g / Temperature: 20 to 40 ° C Current density: 10 to 100 A / dm ² hours: 1 to 5 seconds Brass (Cu-Zn) plating NaCN: 10 to 30 g / NaOH: 40 to 100 g / CuCN: 60 to 120 g / Zn (CN) ₂ : 1 to 10 g / pH: 10 to 13 Temperature: 60 to 80 ° C Current density: 1 to 10 A / dm ² hours: 1 to 10 seconds Electrolytic chromium / zinc treatment (acid bath _{) K 2 Cr 2 O 7:} 2~10g / Zn: 0.2~0.5g / Na 2 SO 4: 5~20g / pH: 3.5~5.0 bath temperature: 20 to 40 ° C. current density: 0.1~3.0A / dm ² Time: 1 to 3 seconds The thus prepared copper foil was laminated and bonded to a glass cloth base epoxy resin plate, and the following items were measured or analyzed.

(1) Peeling Strength The peeling strength of the copper foil in a normal state (room temperature) and after heat treatment at 180 ° C. for 48 hours was measured with a circuit having a width of 10 mm.

(2) Circuit erosion A stock solution of an etching solution containing 200 g / cupric chloride (dihydrate) and 150 g / hydrochloric acid and a 1/50 and 1/100 dilution thereof (temperature 24
C), immerse a 0.2 mm wide copper foil circuit for 1 minute, leave it in a constant temperature and humidity chamber at a temperature of 26 ° C and a humidity of 60% for 24 hours without washing, and let the circuit erode from the circuit end to the inside. (Μm) was measured. (Average value of 10 pieces) (3) Laminated black spots Copper foil was etched with hydrochloric acid-based etchant,
After the heat treatment at 0 ° C. for 1 hour, stains or stains on the etched copper foil surface were observed.

(4) Zinc content in brass (% by weight) The zinc content was calculated from the measured value of the weight increase due to the brass barrier layer and the result of chemical analysis.

 The results are summarized in Table 1.

[Effect of the Invention] As described above, the zinc content of the present invention is 15 to 30% by weight.
The copper foil formed with heat resistant coating layer made of brass electrical quantity 30~60A · s / dm ^2, it hardly stains the resin layer when laminated on the resin base material, the peel strength after high-temperature heating New characteristics such that circuit erosion can be completely prevented without deteriorating the characteristics of the conventional heat-resistant coating layer made of brass, such as little deterioration, etc. It can be suitably used as a copper foil for printed circuits.

Claims (3)

(57) [Claims] 1. A coating layer made of brass is formed on at least a bonding surface of a copper foil with a resin using an electrolytic solution containing copper and zinc ions, and the copper foil having the brass coating layer formed thereon is laminated and bonded to a resin. Then, printing a required circuit on the copper foil, in a method of forming a printed circuit by etching, an electrolytic treatment method of copper foil to prevent circuit erosion during etching,
A method for electrolytically treating a copper foil, wherein the brass coating layer has a zinc content of 15 to 30% by weight and the brass coating layer has an electric quantity of 30 to 60 A · s / dm ² . 2. The method for electrolytically treating copper foil according to claim 1, wherein said brass coating layer is formed after roughening the surface of the copper foil to be bonded to the resin. 3. The brass coating layer is plated at a current density of 1 to 10 A / dm ² for 1 to 10 seconds using a cyan electrolyte containing 42.5 to 85 g / copper ions and 0.6 to 5.6 g / zinc ions. The method for electrolytically treating a copper foil according to claim 1, wherein the copper foil is formed by: