KR840001643B1 - Copper foil for a printed circuit - Google Patents

Abstract

Copper for a print circuit has a nickel layer with a phosphorus or a copper layer. Metals having layers of thin copper, nickel, tin cobalt and Cu-Zn alloy cannot be easily etched by the hyper-sulfuric ammonium solution that is typically used. To solve this problem, thin copper for a print circuit has a nickel layer containing formed phosphorous on the attached copper layer. The manufactureing method uses plating through a nickel plate bath, then the metal is washed and dried.

Description

Copper foil for printed circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copper foil for printed circuits, and more particularly, to copper foil for printed circuits having a nickel layer containing phosphorus on a copper layer (material copper foil).

Printed circuits are widely used as circuits of various electric devices such as radios, televisions, computers, telephone exchangers, and the like, and as the technical field is remarkably developed in recent years, the quality required for printed circuit boards is gradually increasing.

In the copper clad sheet currently widely used, brown spots often occur on the bonding surface of the copper foil and the substrate resin layer (the surface in contact with the resin layer is referred to as the "bonded surface of copper foil"), and this may ruin the appearance of the circuit. At the same time, it adversely affects the dielectric properties of the resin.

In addition, in the recent manufacturing process of the printed circuit board, the high temperature treatment process is gradually increasing, and the adhesive strength between the copper foil and the resin layer is lowered due to the weakening, which is a great problem in practical use. The main reason that brown spots occur or the adhesion between the copper foil and the resin layer is lowered is due to the chemical reaction between the copper foil and the resin layer. It seems, but the explanation of the cause is not complete.

As a method of overcoming the above-mentioned drawbacks, the following method has been proposed.

Japanese Patent Publication No. 53-43555 corresponding to the specification of British Patent No. 1,211,494 and Japanese Patent Publication No. 53-43555 corresponded to 0.2 to 1.0 g / m of nickel, cobalt, chromium or stainless steel on the surface to be bonded of copper foil for printed circuits. A method of plating with ² is described. Further, Japanese Unexamined Patent Publication No. 51-35711 describes a method for electrodepositing indium, zinc, tin, nickel, cobalt, copper-zinc alloy or copper-tin alloy to a thickness of 10.16 × 10 ^-6 cm or more on a copper foil surface. It is. Further, Japanese Unexamined Patent Publication No. 53-39376 describes a method of plating zinc, brass, nickel, chromium, cadmium, tin or bronze on a copper foil surface. Japanese Unexamined Patent Publication No. 49-168632 also discloses a metal that is less expensive than copper, such as aluminum, chromium, manganese, iron, cobalt, nickel, zinc, cadmium, tin, lead, indium, or copper with copper on the surface of the copper foil. Alloys or other alloys, such as copper-zinc, copper-cadmium, copper-tin or tin-zinc, are described for forming a layer.

Among the metals constituting the layer on copper foil, nickel, tin, cobalt and copper-tin alloys have the drawback that they are not etched or difficult to etch by ammonium persulfate solution, which is one of the etching solutions commonly used in printed circuit technology.

On the other hand, in the method of plating zinc, erosion and saw undercut phenomenon occur between copper foil and resin constituting the circuit during etching with ammonium persulfate solution or cupric chloride solution, or contain hydrochloric acid used in printed circuit technology. The same drawback is the erosion between the copper foil and the resin that make up the circuit during the treatment with the solution. Again, there is no practical method in the method of plating brass except for the use of a clarification bath, and the clarification bath has a great problem not only in the work environment but also in the pollution problem.

In the above-described method of plating nickel, there are also attempts to improve the nickel layer so that it can be etched by an ammonium persulfate solution. GB 2010910A discloses that copper and nickel layers can be etched equally by containing 0.05 to 10.0% of sulfur in the nickel layer.

However, the nickel-plated copper foil did not improve the etching property by the ammonium persulfate solution as a result of estimating the example in the specification of the British Patent Publication, and the etching property by the cupric chloride solution is rather impaired. There is a problem.

An object of the present invention is to provide a printed circuit copper foil which solves the above-mentioned various problems existing on the surface to be bonded of the copper foil for printed circuits.

The copper foil for a printed circuit of the present invention is easily and completely etched not only by ammonium persulfate solution but also by cupric chloride solution, and a clean substrate resin surface is formed, and undercut phenomenon does not appear and is treated with a solution containing hydrochloric acid. During the process, the hydrochloric acid-containing solution does not penetrate between the copper foil and the substrate resin, and stains do not occur, and strong adhesion is maintained before and after heating.

That is, the copper foil for printed circuits of this invention is characterized by having the copper layer (material copper foil) and the nickel layer containing phosphorus formed on the to-be-joined surface of the said copper layer.

EMBODIMENT OF THE INVENTION Hereinafter, the copper foil for printed circuits of this invention is demonstrated in detail.

As copper foil for a basic copper layer, what is normally used as long as it is used as copper foil for printed circuits, for example, an electrolytic copper foil, a rolled copper foil etc. are mentioned. In order to improve the adhesion of the surface of the copper layer, it is preferable to perform a roughening treatment, for example, etching by pickling, or roughening treatment by electrodeposition described in the specification of US Patent Nos. 3,220,897 or 3,292,910.

As described above, the nickel layer formed on the surface to be bonded of the copper foil prevents the occurrence of stains on the surface of the bond and brings about heat-resistant adhesion between the laminated substrate resin and the copper foil, and undercut phenomenon during circuit formation by etching. This solution is prevented from invading the substrate resin and the copper foil in a process using a hydrochloric acid-containing solution, and this property is achieved by coating the surface to be joined of the copper foil with nickel plating, and the preferred coating thickness is 0.002 to 0.8. μ more suitably 0.02 to 0.002 μ. If it is less than 0.02μ, the above-mentioned effect is difficult to expect, and if it exceeds 0.8μ, not only the purity of copper for copper foil is lowered, but also the electrical property of copper foil is deteriorated, and the roughening state of the copper foil surface becomes difficult, and the processing speed And in view of the plating material cost, it is disadvantageous and uneconomical.

The nickel layer formed on the copper foil surface of this invention needs to contain phosphorus uniformly in the state disperse | distributed, The content is 0.02-15 weight% normally with respect to nickel, Preferably it is 0.05-10 weight%. If the phosphorus content is less than 0.02% by weight, the effect of preventing etching residues generated by the presence of nickel during circuit forming is insufficient. On the other hand, if the content of the phosphorus content is more than 15% by weight, the current efficiency of electrodeposition of the nickel layer is significantly reduced. In addition, undesirable undercut phenomena appear in circuit forming.

Next, the copper foil manufacturing method of this invention is outlined.

As the method for forming the nickel layer on the copper layer, any method such as an electroplating method or a chemical plating method may be used, but an electroplating method may be used practically.

Hereinafter, it demonstrates in the case by the electroplating method.

As the nickel plating bath, a bath in which a soluble phosphorus compound is dissolved in a nickel plating solution is used, and a nickel layer is formed on the copper layer according to a conventional method.

Phosphorus compounds usable in the present invention as soluble in nickel plating solutions include, for example, sodium hypophosphite, disodium phosphite, sodium phosphotungstate, sodium metaphosphate, sodium phosphate, nickel phosphate and nickel phosphite.

When the present invention is carried out using the electroplating method, the composition, bath temperature, current density, and the like of the nickel plating bath can be used in the same manner except for adding a phosphorus compound, and no specific method is required. As the electroplating bath, there may be used a bath mainly composed of nickel sulfate widely used in the industry, chloride bath, sulfic acid bath and the like.

The copper foil having the phosphorus-containing nickel layer according to the present invention on the surface to be bonded can be obtained as follows when used as a conductive element of the copper clad layer for printed circuits.

That is, brown stain does not occur between the copper foil after laminating the copper foil on the glass-epoxy resin substrate and the substrate resin layer, and the peel strength is sufficient after lamination, and the value is almost even after heating at 300 ° C. for 3 minutes or at 180 ° C. for 5 hours. Does not fall Etching may be used as an etchant, either a ferric chloride solution, a cupric chloride solution, or an ammonium persulfate solution, and the portion to be etched of the copper foil can be easily and completely removed. Moreover, the undercut phenomenon due to the intrusion of the etching solution does not appear at the copper foil-substrate resin interface, and even in the hydrochloric acid test assuming a treatment step with a hydrochloric acid-containing solution, no solution invades the copper foil-substrate resin interface.

Looking at the case where the copper foil is laminated on the polyimide substrate, the greenish brown stain appearing on the surface of the substrate after treatment using the copper foil according to the prior art does not occur when the copper foil treated according to the present invention is used. In addition, when the copper foil is laminated on the phenyl resin substrate by using an adhesive, the peel strength is increased. In particular, when the copper foil is laminated on the phenyl resin based flame resistant substrate, the peel strength is significantly increased.

As is apparent from the above description, the copper foil of the present invention is largely effective in terms of quality and economy by overcoming the drawbacks of the conventional nickel-coated copper foil, the etching process being simple and reliable, the quality is improved, and the defect rate is reduced.

In the production method of the present invention, the material copper foil is continuously plated by passing through a nickel plating bath, washed with water and dried, and industrially produced.

Hereinafter, the present invention will be described through the following examples, which are not intended to limit the present invention.

Example 1

A solution containing 240 g of nickel sulfate (hexahydrate), 45 g of nickel chloride (hexahydrate), 30 g of boric acid, and 5 g of sodium hypophosphite was used as an electrolyte at 50 ° C. on a rough surface (bonded surface) of 35 μm thick electrolytic copper foil. Plating was carried out for 30 seconds at a current density of 2.2 A / dm ² . Electrodeposited nickel per rough surface area was 0.2μ, and the surface was matt nickel. After washing and drying copper foil, the phosphorus content of the nickel plating layer was measured in accordance with a conventional method. The copper foil was laminated on a glass-epoxy substrate to form a laminate, and various performances were measured and listed in the table as in the measurement results.

Example 2

The same treatment as in Example 1 was carried out on the rough surface of the electrolytic copper foil, except that a solution containing 100 g of nickel sulfate (hexahydrate), 15 g of sodium citrate, and 10 g of sodium hypophosphite was used as the electrolyte solution at 1C. Then, the same process as Example 1 was performed to the rough surface of the electrolytic copper foil. Then, the performance was measured in the same manner as in Example 1 and the results are shown in the table.

Example 3

The same treatment as in Example 1 was carried out except that a solution containing 80 g of nickel sulfate (hexahydrate), 8 g of boric acid, 6 g of succinate sodium, 6 g of ammonium chloride, and 24 g of sodium hypophosphite was used as an electrolyte at 50 ° C. We carried out to the rough surface of copper foil. Then, the performance was measured in the same manner as in Example 1 and the results are shown in the table.

Example 4

A solution of PH0.8 containing 175 g of nickel sulfate (hexahydrate), 50 g of nickel chloride (hexahydrate), 50 g of phosphoric acid, 1.3 g of phosphorous acid, and 15 g of nickel carbonate was used at 80 ° C. at a current density of 7 A / dm ² . The same treatment as in Example 1 was performed on the rough surface of the electrolytic copper foil, except that the plating was carried out for 10 seconds and the nickel electrodeposition amount per apparent area of the rough surface was 0.15 µ. Then, the performance was measured in the same manner as in Example 1 and listed in the table.

[Comparative Examples 1 to 3]

Except for using the solution from which the sodium hypophosphite was removed from each of the electrolyte solutions as the electrolyte solution, the same treatment as in Examples 1, 2, and 3 was carried out on the rough surface of the electrolytic copper foil, and the performance was measured in the same manner as in Example 1, and Comparative Examples 1, 2 and 3 respectively.

[table]

Etching condition: Etching at 45 ° C. for 15 minutes using an etching solution containing CuCl ₂ · 2H ₂ O 200g / l and HCl150g / l.

Etching conditions: Etching at 45 ° C. for 15 minutes using an etching solution containing (NH ₄ ) ₂ S ₂ O ₈ 250 g / l, H ₃ PO ₄ 50 g / l.

* Peel strength test: according to JIS C6481-1976, 5-7.

Claims (1)

The copper foil for printed circuits which has a copper layer and the phosphorus containing nickel layer formed on both surfaces or one surface of the said copper layer.