DD277093A1 - METHOD AND DEVICE FOR REPRODUCING AMMONIA CALF COPPER SULFATE SOLUTIONS - Google Patents

Abstract

The invention relates to a method and a device for the treatment of ammoniacal Kupferfersulfataetzloesungen incurred in the etching or leaching of copper-containing material. The process according to the invention consists in adding sulfuric acid to the ammoniacal solution of copper sulphate and subsequently carrying out a copper-producing electrolysis in the acidic range with continuous or periodic addition of further etching solution. Illustration

Description

For this 1 page drawing

Field of application of the invention

The invention finds application in the processing of ammoniacal Kupversulfatlösungen incurred in the etching of copper-coated circuit boards or in the etching or leaching of other t'.upferhaltigen material.

Characteristic of the known state of the art

For the etching of printed circuit boards, numerous etching systems are known. For duru-contact multilayer printed circuit boards, ammoniacal copper chloride solutions are frequently used in addition to ammoniacal copper sulphate solutions. In both cases, the copper tetrammine complex serves as an oxidizing agent. The resulting copper-l-diamminkoinplex is oxidized by atmospheric oxygen back to the divalent copper compound.

If the copper content in the etching solution has risen to a certain value, then the solution must be regenerated or a part removed from the Ätzprczeß and the remaining solution by addition of ammonium salt, ammonia and water are brought back to the initial copper concentration.

For the electrolytic work-up of ammoniacal copper sulfate solutions, the following processes are known:

The Mecer process, which is also applicable to ammoniacal chloride solutions, includes as main stages the copper separation from the etching solution by liquid-liquid extraction and the subsequent sulfuric acid copper extraction electrolysis. A disadvantage is the expense for the stage of liquid-liquid extraction, in particular the need and dealing with dissolved in kerosene copper-specific extractions HeI.

Hoffmann, H., Galvanotechnik 73 (1982) 3, pp.311-315

Direct electrolysis of ammoniacal copper sulfate solutions can be carried out by the ELO-CHEM method in special cells with bipolar electrodes. The disadvantage is that the deposited from ammoniacal solutions cathodic copper precipitates tend to dendrite formation and therefore have to be deducted after reaching about 0.5mm thickness and thus very often.

ELO-CHEM-RECYLING

Company d. ELO-CHEM Ätztechnik GmbH

Drosteweg 21, D 7758 Meorsburg;

Galvanotechnik 75 (1984) 4, p 539

In a complex electrolysis cell containing oxy-ion exchange membrane, copper is deposited in the form of powder according to British FSL-Systom.

Firmonschrift dor Fa. Sigma Enginooring AB, Sweden

Object of the invention

The Ziol dor invention is to work up with low technical and economic effort ammoniacal copper sulfate solution.

Explanation of the essence of the invention

The invention has for its object to provide a method and apparatus for processing of ammoniacal Kupferulfatulfatätzlösungen.

According to the invention, this object is achieved in that about 50% of the etching solution to be worked up is adjusted with stirring with sulfuric acid to a pH of 3 to 6 and from this solution by means of gueolektrolyse the copper copper is deposited cathodically. During the electrolysis of CuSO ₄ - (NH ₄ I ₂ SO ₄ LOSUrIg after the reaction

CuSO ₂ + H ₂ O- * Cu + H ₂ SO ₄ + 1 / 2O ₂

resulting sulfuric acid is bound by continuous or periodic addition of spent Ätzlcsung. The electrolysis process is continued until the solution is almost copper-free.

At the end lies cathodically deposited copper and concentrated ammonium sulfates! About 50% of the new batch of fresh etching solution is used and about 50% can be used for other purposes.

The chemical reactions of the process are as follows, starting from copper tetrammine sulfate as the main constituent of the spent etching solution.

Reaction of sulfuric acid:

[Cu (NH ₃ I ₄ ISO ₄ + 2H ₂ SO ₄ - ^ CuSO ₄ + 2 (NH ₄ ) ₂ SO ₄ Electrolysis and Etch Solution Addition:

CuSO ₄ + 2 (NH ₄ I ₂ SO ₄ + [Cu (NH ₃ I ₄ ) SO ₄ + 2H ₂ O -> 2 Cu + 4 (NH ₄ I ₂ SO ₄ + O ₂ Summenreaktion the workup:

2 [Cu (NH ₃ I ₄ I SO ₄ + 2H ₂ SO ₄ + 2H ₂ O -> 2Cu + 4 (NH ₄ I ₂ SO ₄ + O ₂

Combining the sum reactions of the etching and the Ätzlösungsaufarbeitung, we obtain: Etching:

2CU + O ₂ + 4NH ₃ + 2 (NH ₄ I ₂ SO ₄ -> 2 [Cu (NH ₃ I ₄ I SO ₄ + 2H ₂ O Workup:

2 [Cu (NH ₃ I ₄ I SO ₄ + 2H ₂ SO ₄ + 2H ₂ O -> 2Cu + 4 (NH ₄ I ₂ SO ₄ + O ₂ For 2 moles of Cu:

4NH ₃ + 2H ₂ SO ₄ - * 2 (NH ₄ I ₂ SO ₄

Stoichiometrically results in the recovery of 11 Katode copper an excess of 2.08KNH ₄ I ₂ SO ₄ from 0.54 t NH ₃ and 1.54t H ₂ SO ₄ is formed. Since the spent etching solution in addition to copper tetraamine containing a small quantity of free ammonia, ¹ Ct Jie actually obtained (NH _{4) 2} SO ₄ quantity slightly larger.

If the spent etching solution contains part of the copper in monovalent form, preferably as a diammine complex, copper powder precipitates during the first neutralization and then during the portionwise or continuous etch addition by disproportionation. As a result, the resulting excess of ammonium sulfate is reduced compared to solutions with exclusively divalent copper. It is therefore advantageous to supply copper-containing etching solutions directly, ie without prior oxidation, to the etching solution work-up. The electrolysis can also be started with an aqueous solution of the double salt CuSO ₄ (NH ₄ I ₂ SO ₄ 6H ₂ O. During the recovery electrolysis of a charge, the copper content of the solution steadily decreases decreasing copper concentration can be reduced.

The inventive method is advantageously carried out in the electrolysis tank according to the invention with a closable bottom outlet. In the container are a stirrer, an electric heater, a temperature and oino pH measuring device.

Dnr RnhAjter is filled to about 40% of its capacity with spent timmuri-caustic copper sulfate solution. Untor Rühron is added to 70% igo sulfuric acid until the pH is reached from 3 to 6. After the onset of sooikrocht angoordnoton plate electrodes, Kupferfernka'.oden and lead anodes, is electrolyzed at about 50 ⁰ C and under moderate agitation with a current density of 100A / m ² , bozogon on dioxid initially effective Katoden'läche. Continuously or periodically, so much etching solution is replenished that the sulfuric acid free-changing by copper precipitation becomes gundundone.

Gogon Endo dor Entkupforung has fallen in line with the level increase and thereby bedding increase the effective Katodcnflächeo boi konstantor amperage the katodischo current density on about 50 A / m ² . Is an extensive Kupforontfornung on z. B. 0.2 g / l Cu orfordorlich, so in the laston phase of Entkupferung oino katodischo current density of 10A / m ² angowandt.

The advantageous effects of the solution according to the invention consist in that

- The copper acid solution is deposited in a metallic form

- The remaining ammonium sulfate solution can be used proportionally to the new batch of etching solution

- The residual ammonium sulfate can be used in a known manner

- The process can be performed in a simple design device.

embodiment

The invention will be explained in more detail below with reference to two examples and a drawing

example 1

The electrolytic tank from which the electrodes have been removed is filled to about 40% of its capacity with spent ammonia copper sulfate etch solution. While stirring, about 70% sulfuric acid is added until the pH range of 3 to 6 is reached. After inserting the electrodes is electrolysed at about 50 ° C and with moderate stirring at a current density of 100 A / m ² , based on the initially effective cathode surface. Continuously allowed to flow so much etching solution that the released by the copper deposition of sulfuric acid immediately neutralized and thus the genann pH range is maintained. Tanning At the end of the decoppering, the cathodic current density has fallen to about 50A / m ² due to the increase in level and the increase in effective cathode area. To substantially reduce the final copper content to, for example, 0.2 g / l of Cu, a current density of 10 A / m ² is used in the last phase of decoppering.

Example 2

The electrolysis tank 1 has a rectangular cross section in the horizontal plane. At the bottom of a bottom outlet valve 2 is attached. In the container 1 are the stirrer 3, the recoverable cathode plates 5 and the insoluble anode plates and a temperature sensor 9 and a pH sensor 10. In addition, a heating device 8 is arranged in the container 1. About the feed 6 and 7, the dosage of the sulfuric acid or the spent ammoniacal Kupferulfatulfatätzlösung takes place.

Claims (4)

1. A process for working up ammoniacal copper sulphate etching solution, characterized in that the ammoniacal Kupferfersuifatätzlösung is adjusted with sulfuric acid to a pH of 3 to 6 and then in the acidic region a copper extraction electrolysis is carried out with continuous or periodic addition of further Etziösung. 2. The method according to claim 1, characterized in that the resulting during the etching process copper 3i l-containing spent etching solution is fed directly to the workup while avoiding subsequent oxidation. 3. The method according to claim 1, characterized in that instead of the starting solution prepared from the etching solution and sulfuric acid, an aqueous solution of the salt copper ammonium sulfate is used. 4. An apparatus for processing ammoniacal Kupferulfatulfatätzlösungen, characterized d & by that it consists of a container (1) in a horizontal plane rectangular cross-section which has a closable by a valve (2) bottom outlet, that in the container, a stirrer (3), with Control valves closable inlet pipes from Ätzlösungsbehälter (7) and the sulfuric acid container (6) and temperature (9) and pH sensor (10) and an electric heater (8) are located, and that in the container (1) liftable cathode (5) and insoluble anode sheets (4) are arranged.