JPH04318997A - Copper foil for printed circuit and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a copper foil for a printed circuit and its manufacture which carries out a chromate process after a ternary alloy layer constituting of one element among tin, cobalt, nickel, and arsenic, copper, and zinc is electrodeposited on a junction surface between a basic copper foil and a resin- made insulating substrate, so as to improve the jointing strength with respect to the resin-made insulating substrate. CONSTITUTION: The present invention of copper foil for a printed circuit is obtained by roughening the surface of copper foil by an ordinary method for the basic copper layer. Then the copper foil is coated with a ternary alloy layer by performing electrodeposition in a plating liquid of 25 to 35 deg.C in temperature which has copper sulfate of 24 to 50g/l concentration, sodium tartrate of 40 to 60g/l concentration, zinc oxide of 2.5 to 5.0g/l, caustic soda of 40 to 60g/l concentration, and one element of 0.3 to 3.0g/l from among tin, cobalt, nickel, and arsenic as a 3rd element with a DC current of 7 to 30A/dm2 in current density. After that, the foil is manufactured by conducting chromate processing.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a copper foil for printed circuits that has improved bonding characteristics to resin-made insulating substrates, and more specifically, to improve bonding characteristics to insulating substrates.
After a ternary alloy layer composed of one element among tin, cobalt, nickel, and arsenic, copper, and zinc is electrodeposited on the bonding surface of the basic copper foil with the insulating substrate, This invention relates to a chromate-treated copper foil for printed circuits and a method for manufacturing the same.

0002

2. Description of the Related Art Printed circuits are widely used in the circuits of various electronic devices such as radios, televisions, telephone exchanges, and computers. In particular, recently, in response to the demand for smaller, more highly integrated printed circuits, printed circuit boards in which copper foil is bonded to resin insulating substrates have been proposed, but copper ions diffuse into the resin layer. brown spots often appear on the bonding surface between the copper foil and the substrate resin layer.
ng) occurs, which not only deteriorates the appearance of the circuit but also weakens the electrical insulation of the insulating substrate, which is a problem.

[0003] Also, in the recent manufacturing process of printed circuit boards,
High temperature processing processes are becoming more and more popular. For this reason, the bonding strength between the copper foil and the resin layer decreases due to thermal deterioration, which poses a serious problem in practice. The following methods have been proposed to solve these problems.

US Pat. No. 3,585,010 discloses that indium, zinc, tin, nickel, cobalt, brass (copper-zinc alloy) or bronze (copper-zinc alloy) is used on the surface of the copper foil to be bonded to the insulating substrate. tin alloy), 4 x 10-6 inch
A method of electrodepositing to a thickness greater than or equal to the above is described.

However, there is no practical method for plating brass other than using a cyanide bath, and cyanide baths pose not only problems in the working environment but also pollution problems. are doing. Furthermore, when zinc plating is etched with an acidic etching solution, the etching solution corrodes the space between the copper foil and the resin layer, causing a so-called undercut phenomenon.

[0006] Korean Patent Publication No. 84-1643 describes a method of coating a copper foil surface to be bonded to an insulating substrate with nickel or the like containing 0.02 to 15% by weight of phosphorus.

[0007] However, this method is uneconomical because it uses an electrolytic solution at a temperature of 50°C or higher to coat the nickel, and also has the disadvantage that it is very difficult to control the phosphorus content within the above range. be.

[0008] Republic of Korea Patent Publication No. 83-2611 describes a method of coating a tin layer on both or one side of a copper foil and then coating a zinc-vanadium alloy layer on the tin layer. There is.

However, tin has the disadvantage that it is almost impossible to etch with ammonium persulfate solution, a type of etchant commonly used in printed circuit technology.

0010

[Problems to be Solved by the Invention] The object of the present invention is to maintain good adhesion even after high-temperature heat treatment or chemical treatment, and to maintain good adhesion with any etching solution without causing circuit undercut phenomenon. An object of the present invention is to provide a copper foil that has etching properties and suppresses diffusion of copper ions into an insulating resin layer.

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the copper foil for printed circuits of the present invention has a surface roughened on the side to be bonded to an insulating substrate, and the surface is made of copper and zinc. It was coated with a ternary alloy layer to which one of the three elements tin, cobalt, nickel, and arsenic was added, and the ternary alloy layer was chromate-treated.

[0012] In addition, in the method for manufacturing copper foil for printed circuits of the present invention, when forming a coating layer by electroplating on the roughened surface of the copper foil on the side to be bonded to the insulating substrate, sulfuric acid is used. Copper (pentahydrate) 24-50 g/l (liter), sodium tartrate 40-60 g/l, zinc oxide 2.4-5.
In a plating solution containing 0 g/l, 40 to 60 g/l of caustic soda, and 0.3 to 3.0 g/l of one of the third elements tin, cobalt, nickel, and arsenic, Using the roughened copper foil as a cathode, plating solution temperature is 35°C and DC current density is 10 to 20 A/dm2.
After treatment for 0 seconds, it was washed with deionized water, and chromate treatment was performed by electrolytic method.

[0013] In the above method for manufacturing copper foil for printed circuits, the third element is selected from sodium stannate, cobalt sulfate (heptahydrate), nickel sulfate (hexahydrate), and arsenite. It can be added by selecting one of them.

[0014]

[Function] The surface of the copper foil for printed circuits that is bonded to the insulating substrate is roughened, and the surface is made of copper, zinc, and the third elements tin, cobalt, nickel, and arsenic. By coating with a ternary alloy layer containing one certain element, heat resistance and chemical resistance are improved. This maintains good adhesion with the insulating resin layer, prevents undercut phenomena, and furthermore prevents copper ions from diffusing into the insulating resin layer. Further, by subjecting the ternary alloy layer to chromate treatment, rust is prevented.

[0015]

EXAMPLES Examples of the present invention will be described in detail below. The copper foil for printed circuits of the present invention, which is provided to achieve the above-mentioned object, has copper-zinc-tin, copper-zinc-cobalt, copper, etc. −
It is manufactured by electrodepositing a ternary alloy layer such as zinc-nickel or copper-zinc-arsenic, and then subjecting it to chromate treatment using an electrolytic method.

More specifically, the copper foil for printed circuits of the present invention is obtained by roughening a copper foil (hereinafter referred to as "basic copper foil") for a basic copper layer using a conventional method. , copper sulfate concentration 24~50g/l, sodium tartrate concentration 40~
60 g/l, zinc oxide concentration 2.5-5.0 g/l, caustic soda concentration 40-60 g/l, and 0 concentration of one of the third elements tin, cobalt, nickel or arsenic. In a plating solution having .3 to 3.0 g/l, the plating solution temperature is 25 to 35 °C, and the current density is 7 to 30 °C.
It is produced by electrodepositing with a direct current of A/dm2 for 5 to 15 seconds to coat a ternary alloy layer, and then subjecting it to chromate treatment.

As the basic copper foil, any copper foil commonly used for printed circuits can be used, but electrolytic copper foil or rolled copper foil is preferable.

In order to improve the bonding strength of the alloy layer to the basic copper foil surface, the surface roughening treatment is etching by pickling, which is described in US Pat. No. 3,220,897 or 3
, 293,910 is suitable.

If the copper sulfate concentration is lower than 20 g/l, a large amount of gas will be generated during treatment, making it difficult to maintain the concentration. If it is high (more than 50g/l), a lot of chemicals will be consumed. Sodium tartrate is 4
Below 0 g/l, copper ions form hydroxides in alkaline solutions and are precipitated. At 60 g/l or more, there is not a big difference, but the consumption of chemicals is still large.

The amount of zinc is adjusted so that the ratio with copper is 4:1, and if the ratio is significantly out of this range, the chemical resistance and heat resistance will deteriorate and the effectiveness of the alloy will decrease. Add enough caustic soda to dissolve the zinc oxide and allow the copper and tartrate to bond with a stable complex ion. It also improves the electrical conductivity of the solution.

[0021] And the third element tin, cobalt,
If nickel, arsenic, etc. are reduced to less than 0.3g/l,
The effect of the alloy will not be apparent, and the chemical resistance and heat resistance will decrease. If it exceeds 3.0 g/l, the overall composition ratio of the alloy changes, electrodepositability deteriorates, and it becomes difficult to obtain uniform plating, which is uneconomical.

In addition, if the temperature is low, the electrodeposition characteristics are poor, and 40
If the temperature exceeds °C, copper components remain in the alloy, resulting in poor heat resistance.

[0023] If the current density is less than 5 A/dm2, alloy electrodeposition will not occur. If it exceeds 30 A/dm2, gas generation will be severe, the composition of the liquid will change, alloy powder will be formed, and it will not adhere to the copper foil.

The third element, tin, cobalt, nickel, arsenic, etc., has the effect of suppressing copper diffusion and preventing zinc from being quickly dissolved by acid. These elements may be added in the form of salts that are soluble in an alkaline solution. Once this alloy layer is formed, an electrolytic method is used for chromate treatment. Here, in the chromate treatment method, the composition of the solution is 5 g/l of sodium dichromate, the potential is about 30 V at room temperature,
Run for about 5 seconds to allow gas to evolve. Gas generation prevents the surface of the copper foil from being oxidized. Specific embodiments and comparative examples of the present invention are shown below, but the present invention is not limited to the following embodiments and can be freely modified within the scope of the invention.

(Embodiment Example 1) Copper sulfate (pentahydrate) 48
g/l, sodium tartrate 60g/l, zinc oxide 4.1
g/l, caustic soda 60g/l and sodium stannate 0
．． A solution composed of 5 g/l was used as the electrolyte, and 3
A 5 μm thick copper foil was used as the cathode. Set the liquid temperature to 35°C,
After plating for 10 seconds at DC current densities of 10, 15, and 20 A/dm2, the plated copper foil was washed with deionized water. Next, in a solution of 5 g/l of sodium dichromate, the solution temperature was 25°C and the potential was 30°C.
Chromate treatment was performed with V for 5 seconds.

(Embodiment Example 2) Embodiment Example 1 except that the electrolytic solution of Embodiment Example 1 contains 0.5 g/l of cobalt sulfate (heptahydrate) instead of sodium stannate. The surface of the copper foil was treated in the same manner as above.

(Embodiment Example 3) Embodiment Example 1 except that the electrolytic solution of Embodiment Example 1 contains 0.5 g/l of nickel sulfate (hexahydrate) instead of sodium stannate. The copper foil surface was treated in the same manner as above.

(Embodiment Example 4) As the composition of the electrolytic solution of Embodiment Example 1, 0.5 arsenite was added instead of sodium stannate.
The surface of the copper foil was treated in the same manner as in Embodiment Example 1, except for containing g.

(Comparative example) Zinc sulfate concentration 10 g/l, pH
5 was used as the electrolyte, a 35 μ thick copper foil was used as the cathode, the solution temperature was 30°C, and the current density was 5 A/dm2.
After being treated for 20 seconds, the sample is washed with deionized water and chromate treated under the same conditions as in Embodiment 1 above.

The coatings of the embodiment examples and comparative examples described above were laminated and molded on a glass fiber-epoxy resin insulating substrate, and the adhesive strength thereof was measured. Furthermore, the adhesive strength was measured after heat treatment with hot air at a temperature of 210°C for 630 minutes. Further 5N-
After being immersed in HCI solution for 1 hour, the adhesive strength reduction rate (%
) was measured. The measurement results are shown in FIG.

[0031]

Effects of the Invention As described above, according to the copper foil for printed circuits and the manufacturing method thereof of the present invention, the surface to be bonded to the insulating substrate is roughened, and the surface is roughened with copper, zinc, and copper foil. Since it is coated with a ternary alloy layer containing one of the three elements tin, cobalt, nickel, and arsenic, heat resistance and chemical resistance are improved. Therefore, the adhesion between the insulating resin layer and the insulating resin layer is maintained well, the undercut phenomenon is prevented, and furthermore, the diffusion of copper ions into the insulating resin layer is prevented. Furthermore, by subjecting the ternary alloy layer to the chromate treatment, rust is prevented from forming on the surface of the copper foil for printed circuits.

[Brief explanation of drawings]

[Figure 1] Diagram comparing adhesive strength between embodiment examples and comparative examples

Claims (3)

[Claims] Claim 1: The surface to be bonded to the insulating substrate is roughened, and the surface contains copper, zinc, and one of the third elements tin, cobalt, nickel, and arsenic. A copper foil for printed circuits, characterized in that it is coated with an added ternary alloy layer, and the ternary alloy layer is chromate-treated. 2. When forming a coating layer by electroplating on the roughened surface of the copper foil to be bonded to the insulating substrate, 24 to 50 g/l of copper sulfate (pentahydrate), Sodium tartrate 40-60g/l, zinc oxide 2.4-5.0
g/l, 40 to 60 g/l of caustic soda, and 0.3 to 3.0 g/l of one of the third elements tin, cobalt, nickel, and arsenic, in a plating solution. Using the roughened copper foil as a cathode, plating solution temperature is 35°C and DC current density is 10 to 20 A/dm2.
1. A method for manufacturing a copper foil for printed circuits, which comprises treating the copper foil for 20 seconds, washing with deionized water, and performing a chromate treatment using an electrolytic method. Claim 3: The third element is sodium stannate, cobalt sulfate (heptahydrate), nickel sulfate (hexahydrate),
3. The method for producing a copper foil for printed circuits according to claim 2, wherein one selected from arsenite is added.