KR930006103B1 - Printed circuit for electrolysis copper foil & method - Google Patents

Abstract

The electric copper foil for the printed circuit of the precision control circuit is prepared by (a) roughening for binding copper foil with an insulating substrate, (b) coating the surface of copper foil with Cu-Zn-(Sn,Co,Ni,As) alloy, (c) electroplating with alkali stannate solution containing sodium hydroxide, copper sulfate, sodium stannate, zinc oxide and one compound of cobalt sulfate, nickel sulfate and arsenous acid as an electrolyte and 10-20 amp/dm2 of the direct current density at 35 deg.C, and (d) cleaning with ion exchange water and chromate rust-proofing.

Description

Electrolytic copper foil for printed circuit and manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic copper foil for a printed circuit and a method of manufacturing the same, in particular, copper, zinc, tin, and cobalt on a surface bonded to an insulating substrate by using an electrolytic copper foil for a printed circuit which has been roughened to improve adhesion to an insulating substrate. And nickel arsenic, such as ternary alloy layer is plated to reduce the deterioration of adhesion even under the condition of chemicals and heat treatment.

Generally, printed circuits are widely used in precision control circuits of various electric and electronic devices such as radios, televisions, telephone exchanges, and computers. In particular, in recent years, the high quality of the printed circuit board is required, the circuit of the substrate has been miniaturized and highly integrated. The high-precision insulating board is mainly impregnated with epoxy resin in glass fiber. At this time, the resin bonded to the copper foil reacts with copper to make yellow stain on the insulating board, which not only deteriorates the appearance but also the electrical insulating property of the insulating board. Worsens. This reaction occurs by diffusing into the resin layer of copper ions. In addition, in recent years in the printed circuit board manufacturing plant, the high temperature treatment process is increasing, which causes a decrease in adhesive strength between the copper foil and the resin layer due to thermal deterioration, which is a practical problem. Looking at the conventional methods for overcoming this problem, US Patent No. 3,585,010 proposes a method of coating brass and zinc on the surface of the copper foil to be bonded to the insulating substrate. However, when coating brass, only the method of plating using cyanide compound has been put to practical use. By the way, this cyanide compound has its own high toxicity and working temperature, so there is difficulty in working, and pollution problem is also greatly raised, such as waste water treatment. In the case of coating zinc, there is an etching process during the circuit fabrication process. When the etching solution is acidic, zinc is easily dissolved in acid, so that a decrease in adhesive force occurs, and the bonding surface between the copper foil of the circuit portion and the substrate below it is formed. There is a drawback that the undercut phenomenon in which the etching liquid penetrates occurs.

In addition, Korean Patent Publication No. 84-1643 discloses a method of coating a nickel layer containing phosphorus on a cut surface with an insulating substrate. However, this method is disadvantageous because the working temperature is higher than 50 ° C. and the metal nickel is coated, which is uneconomical and difficult to control the phosphorus content.

In addition, Korean Patent Publication No. 83-2611 discloses a method of coating an alloy layer of zinc and vanadium on a surface of tin or tin on a joint surface of an insulating substrate, and tin is a type of etching solution used in an etching process during a circuit fabrication process. The ammonium sulfate solution has a drawback that is difficult to etch.

An object of the present invention is to minimize the difficulty of work and wastewater treatment problems, and to produce a copper foil having good adhesion after heat treatment at room temperature or after chemical treatment. Moreover, it is in order to make the copper foil which has favorable etching property in any etching liquid, prevents the undercut phenomenon of a circuit, and the diffusion of copper ions is suppressed. In order to achieve the above object, the present invention uses a direct current to the surface of the copper foil to be bonded to the insulating substrate and then chromate rust even after coating the ternary alloy layer of copper, zinc, tin, cobalt, nickel, or arsenic by electrolytic method. The treatment was performed by electrolytic method.

Hereinafter, the electrolytic copper foil for a printed circuit of the present invention and a manufacturing method thereof will be described in detail. In general, the manufacturing process of the electrolytic copper foil for printed circuits is made of copper foil having a desired thickness by using a continuous electrolytic method of the basic copper foil, as shown in the Korean Patent Publication No. 84-1463, followed by United States Patent Nos. 3,220,897 or 3,293,109 The roughness treatment for the improvement of adhesion is given by the method given in. The surface of the copper foil which has been finished is coated with ternary alloys such as copper and zinc and tin, copper and zinc and cobalt, copper and zinc and mikkel, and copper and zinc and arsenic, and then subjected to chromate rust treatment.

The method of forming the alloy layer after the rough treatment will be described in more detail. The composition of the plating solution for obtaining an alloy layer made of copper, zinc, tin, cobalt, nickel, and arsenic such as a third element is as follows. Copper sulfate 24-50 g / l, tartaric acid soda 40-60g / l, zinc oxide 2.4-5.0g / l, caustic soda 40-60g / l and third element tin, cobalt, nickel, arsenic Etc. at any one of 0.3-3.0 g / L, the current density is 7 = 30 amp / dm ² with the liquid temperature at 20 ° C-35 ° C, and the current density with the liquid temperature at 20 ° C-35 ° C. Is 7-30 amp / dm ² , and the processing time is 5-15 sec. If the sulfur phase copper is less than 20g / ℓ, the gas generation during processing is difficult and the concentration is difficult to maintain. Higher than 50g / ℓ consumes a lot of drugs. If the sodium stannate is less than 40 g / l, copper ions are precipitated by forming hydroxides in the alkaline solution. More than 60g / ℓ does not have a big difference, but also consumes a lot of drugs. The amount of zinc is controlled so that the ratio of copper is 4: 1, and if it is largely deviated from this ratio, the chemical resistance and heat resistance deteriorate and the effect of the alloy is reduced. Caustic soda is added enough to dissolve the zinc oxide so that copper and stannate are bound by a limited complex ion. In addition, the electrical conductivity of the solution is improved.

If the third element, tin, cobalt, nickel, or arsenic, is less than 0.3 g / l, the effect of the alloy is not exhibited, and chemical resistance and heat resistance are lowered. When the content is more than 3.0 g / l, the alloy has an overall composition ratio, and the electrodeposition properties deteriorate, making it difficult to obtain uniform plating. When the temperature is low, the electrodeposition characteristics are poor, and when the temperature is 40 ° C. or higher, the copper component in the alloy increases, resulting in poor heat resistance. This is not a current density of 5 amp/dm ² below alloy deposition, if the 30apm / dm ² or more varies is the gas generating composition of the liquid is too good the alloy powder is formed not in close contact with the copper foil. These third elements, tin, cobalt, nickel and arsenic, have the effect of suppressing the diffusion of copper and preventing zinc from dissolving quickly in acid. These elements may be added in the form of alkali-dissolved salts. When this alloy layer is formed, an rustproof chromate treatment is used as an electrolytic method. The anti-corrosive chromate treatment is performed for about 5 seconds so that the liquid composition is 5 g / l of sodium dichromate and gas is generated at a potential of about 30 V at room temperature. Gas generation prevents oxidation on the surface of the copper foil.

Taking the examples and comparative examples of the alloy and the antirust treatment of the present invention as described above, the experimental results of the adhesion at the time of heat treatment and chemical treatment are described in the table as follows.

Example 1

An alkaline tartarate solution containing 48 g of copper sulfate (5 oxalate), 60 g of sodium stannate, 4.1 g of zinc oxide, and 60 g of caustic soda was used as an electrolyte solution at 35 ° C. Using a 35μ thick copper foil as the cathode, the DC current density was treated for 10 sec at 10, 15, and 20 amp / dm ² , respectively, followed by washing with ion-exchanged water. The solution containing 5 g of sodium dichromate per liter is then chromated at 25 ° C. for 30 sec at a potential of 30 V.

Example 2

The same conditions as in Example 1 were carried out using a solution containing 0.5 g of cobalt sulfate (7-hydroxylate) as the third element in the electrolyte solution composition of Example 1.

Example 3

The same conditions as in Example 1 were carried out using a solution containing 0.5 g of nickel sulfate (hexahydrate) as the third element in the electrolyte composition of Example 1.

Example 4

Using the solution containing 0.5 g of arsenic acid as the third element in the composition of the electrolyte solution of Example 1, the same conditions as in Example 1 were performed.

[Comparative Example]

A solution of 10 g of zinc sulfate and PH 5 per 1 L was treated at 30 ° C. for 5 sec with a current density of 5 amp / dm ² , washed with ion-exchanged water, and subjected to rust-prevention chromate treatment under the same conditions as in the above example.

The coating strengths of the above Examples and Comparative Examples were laminated with a glass fiber-epoxy insulating substrate and then heat-treated with hot air at 630 minutes at room temperature and 210 ° C., and after 1 hour immersion in 5N Hcl solution.

[table]

Claims (3)

In electrolytic copper foil for printed circuits used in precision control circuits of various electrical and electronic equipment, tin, cobalt, nickel, arsenic in copper, zinc and third elements on the surface of roughened copper foil bonded to an insulating substrate An electrolytic copper foil for printed circuits, which has been subjected to chromate rust treatment after coating a ternary alloy to which one is added. In electroplating the coating layer on the rough-treated copper foil surface to be bonded to the insulating substrate, 24-50 g / l copper sulfate (5-hydrate), 40-60 g / l sodium tin oxide, 2.4-5.0 g / l zinc oxide, Caustic Soda 40-60 g / l Alkaline Tartrate solution containing 0.3-3.0 g / l as a third element solution at 35 ° C as electrolyte and 35μ thick copper foil as cathode A method of manufacturing an electrolytic copper foil for a printed circuit, characterized in that 10-20 amp / dm ² is treated for 10 sec, followed by washing with ion-exchanged water to perform an anti-rust chromate treatment by an electrolytic method. 3. The third element according to claim 2, wherein the third element is sodium carbonate and cobalt sulfate (7 oxalate). A method for producing an electrolytic copper foil for a printed circuit, comprising selecting and adding either nickel sulfate (hexahydrate) or arsenic acid.