CZ20004244A3 - Substrate copper plating process - Google Patents

Abstract

A method for galvanizing copper substrates using of insoluble anodes in acidic copper baths with separate replenishing the consumed copper ions at which the main amount of copper ions is directly introduced in the mold copper carbonate and / or basic carbonate copper, without the use of membranes and auxiliary electrolytes, into a special tank that is connected in bypass to work electrolyte, wherein the released CO2 gas is released in the electrolyte special tank.

Description

Method of galvanic copper plating of substrates

Technical field

It is an object of the present invention to provide a process for electroplating copper substrates using insoluble anodes in acidic copper baths with separate replenishment of spent copper ions.

BACKGROUND OF THE INVENTION

The use of insoluble anodes for plating printed circuit boards, especially in horizontally flow devices, requires continuous replenishment of copper ions in the working solution from the outside, as there is no need to dissolve the copper anodes in the working electrolyte. At the same time, the organic additives to the electrolyte, which are necessary to achieve the physical properties of the deposited copper layer as well as its distribution over the material, must be added.

According to DE-A 44 05 741 this is done by dissolving the metal in a separate regenerative cell. Redox systems are added to speed up this process. On the one hand, it is difficult to dissolve the required amounts of copper ions into the solution, and on the other hand, due to the presence of the redox system, the uncontrolled change of the organic additives by the decomposition processes taking place on the anode largely takes place. This makes it difficult to achieve a reproducible quality of excretion after prolonged operation, since organic additive systems, consisting of multiple different organic compounds, can easily be out of balance and out of control. By means of redox processes, by-products are formed which further change the characteristics of the bath or the bath. secretion. In addition, oxidative degradation makes it necessary to add larger amounts to the working electrolyte

-2.organic additives. This again greatly increases production costs and, if necessary, must be corrected by appropriate cleaning measures, for example by filtration through activated carbon. All this is wasteful and counterproductive.

DE 195 39 865 discloses a method which avoids the need for an additional redox system. At the same time, the addition of metal ions by means of a soluble anode is possible in a separate regeneration space. At the same time, an auxiliary cathode is used which is kept free of metal by the selection of a suitable agent. Another embodiment of this solution assumes that the insoluble anodes of the electrolytic cell are located in an auxiliary anolyte which is separated from the electrolyte by an anion-impermeable membrane. A disadvantage here is that the amounts of metal ions required for the aging of the production are difficult to dissolve in a sufficient amount or in a sufficient amount. large volumes of regeneration space with a large number of anodes are required. Here, too, double decomposition of organic matter in the process cannot be avoided.

In principle, it has proven not very economical and ecological to work with insoluble anodes, but to add metal ions to the process by dissolving metal anodes in the bypass.

EP 667 923 discloses a method of electrolytically coating e.g. copper steel from an electrolyte comprising copper bisphosphate, using insoluble anodes coated e.g. with platinum or iridium oxide. Necessary replenishment of copper ions is accomplished by the addition of copper hydroxide. Care should be taken to ensure that the diphosphate electrolyte is operated in an alkaline pH range, whereas, for example, for the plating of printed circuit boards, an electrolyte with sulfuric acid is preferred.

SUMMARY OF THE INVENTION

The object of the invention was to provide a copper electrolyte, preferably

- J. • · ·

Sulfuric acid-based, suitable for the use of insoluble anodes, especially in flow-through devices, for direct current plating and / or pulse reversal plating, without having a strong adverse effect on the organic additives or the like. to increased degradation of these organic substances or. increased production of by-products. Further, the metal ion replenishment should be carried out so as to avoid further disturbing changes in the organic matter in the process. The operation of the entire electrolysis system, including the regeneration of organic substances in the process and the recovery of cuprous ions, must be cost-effective, cost-effective and environmentally-friendly without any quality disadvantages. It should be possible to dispense with membranes and auxiliary electrolytes.

This object is achieved according to the invention solved in that without the use of diaphragms and auxiliary electrolytes, the main quantity of copper ions supplied in the form of copper carbonate and / or basic copper carbonate in a separate tank connected in bypass to the working electrolyte, the released gaseous C0 ₂ in a separate container .

Copper baths are preferably used which contain polymers as organic constituents which are produced by polymerizing bifunctional propane derivatives with one or more unsaturated alcohols having 3 to 10 carbon atoms and one or more double and / or triple bonds.

These baths are described, for example, in EP-A 137 397. These electrolytes generally contain only components which during the electrolysis process do not form any decomposition products and do not adversely affect the quality of the precipitate or precipitate formed. system balance. These additives have been shown to be suitable for use in flow-through devices and inert anodes.

The problem of replenishment of the electroplated copper ions · ·

According to the invention, it is solved by the addition of copper salts. However, the addition of copper (II) sulphate or pure copper (II) hydroxide is ruled out, since the first case would not avoid excessive enrichment of the electrolyte with sulfate ions, and in the second case the neutralization processes would adversely affect efficiency.

It has been shown that the addition of copper carbonate and / or basic copper carbonate, optionally in conjunction with small amounts of other copper salts, such as copper sulfate, to the electrolysis system results in good results for the purpose of the invention.

Because when dissolving copper carbonate CO is formed? and there is a noticeable evolution of gas and turbidity of the solution, measures are taken to prevent a strong influence of gas evolution on the electrolytic deposition of copper.

Therefore, the dissolution of copper salts is carried out in a separate tank, which in the bypass is connected to the working electrolyte.

For this purpose, the tank is equipped with a stirrer and heating system to accelerate and thus economize the dissolution process. The very good temperature stability of the additives according to EP 137 397 makes virtually no reduction in electrochemical activity during the dissolution process at elevated temperature.

Virtually no special additive additives are required which impair the process efficiency, as is generally observed in the case of multi-component electrolytes. The electrolyte is preferably supplied by means of a pump system with a filter unit. Thus, disturbance of the electrolysis process can be completely avoided.

In another preferred embodiment of the invention, the use of copper etching solutions is ecologically recycled and converted into carbonate by addition of e.g. sodium carbonate

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copper. Such copper etching solutions generally contain copper ions and mineral acids such as hydrochloric acid, sulfuric acid and the like, and optionally an oxidizing agent and stabilizers. These etching solutions can now be collected. Furthermore, by inhalation of air, anode residues or circuit board residues present in solution may be dissolved. The solutions may be transferred to a second tank, for example, through an activated carbon filter. Subsequently, this solution is adjusted to a pH below the pH of Cu (OH) 2 deposition by means of eg caustic soda or another suitable alkaline solution. This neutralization avoids the release of excess CO 2 in the reaction of the acid with the carbonate. The suction device can be reduced and may have less power so that it can operate more economically. With the addition of e.g. Na 2 CO 3 with vigorous stirring, CuCO 3 is formed which falls out of solution. The remaining solution became clear. After a sufficient reaction time, the remaining clear solution is carefully filtered. CuCO. overlap with water, mix and repeat the process. The remaining copper carbonate is dried and can be used to replenish the copper ions according to the invention.

The operating parameters for the copper sulphate electrolyte are as follows:

• ·

-6.-

with benefit Cu ²⁺ 15 to 40 g / l 20 to 30 h ₂ Sat ₄ 150 to 300 g / l 200 to 250 Cl 30 to 100 mg / L 60 to 80 additives * 4 to 10 ml / l 4 to 10 operating temperature 20-50 ° C 25 to 35

* Cuprostar LP-1 (one-component additive according to EP 137 397)

The above parameters are mainly related to horizontal flow operation. Any of the prior art plating devices may be used.

The copper deposited by the process of the invention is finely crystalline, has a silky luster, is almost free of internal stresses, ductile, and exhibits high tensile strength. It is glossy, without coarseness or pores. It complies with the usual quality tests in the industry (eg according to MIL SPEC 55 110). The electrolyte has an excellent uniform distribution of metal over the surface and a very good spreading ability, for example, in the holes of the printed circuit boards.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the invention is illustrated by the following example.

electrolyte composition:

H ₂ SO ₄ 192.5 g / i Cu ²⁺ 20.0 g / 1 Cl 62 mg / l additive (LP-1) 6 ml / l

temperature ± 1 ° C

- 7. Mechanical anode bath mixing: Pt-expanded current density 2 A / dm ²

After a galvanizing period of 150 minutes, 8.9 g / l of copper was deposited.

Content H ₂ SO ₄ 204 g / l

Addition 15.5 g / l CuCO ₃ * Cu (OH) ₂ (= 809 g / l Cu ²⁺ )

H ₂ SO ₄ content after addition of 189.7 g / l

Second Galvanizing Period:

Excluded copper: 9.1 g / l H ₂ SO content ₄ 202 g / l

Addition of 15.8 g / l CuCO ₃ xCu (OH) ₂

Content H ₂ SO ₄ 189 g / l

In all cases, the quality of electrolyte depletion complied with the technical requirements.

Continued use of this electrolyte did not cause problems even after 20 electroplating periods.

Claims (1)

PATENT CLAIMS A method of galvanizing copper substrates using insoluble anodes in acidic copper baths with separate copper ions consumed, characterized in that the major amount of copper ions is directly fed in the form of copper carbonate and / or basic copper carbonate, without the use of membranes and auxiliary electrolytes , into a separate tank which is connected in bypass to the working electrolyte, whereby the released CO ₂ gas is released in a separate tank. Process according to claim 1, characterized in that the copper baths contain, as organic components, polymers produced by polymerizing bifunctional propane derivatives with one or more unsaturated alcohols having from 3 to 10 carbon atoms and one or more double and / or triple bonds. 3. Method according to claim 1 or 2, characterized in that copper carbonate with manufactured excretion from copper solutions salts with carbonate sodium • 4. Method by claim 3, characterized by by taking a solution The copper salts are neutralized to a pH below the pH of the copper (II) hydroxide excretion prior to excretion with caustic soda.