EP1264010B1 - Method and device for the regulation of the concentration of metal ions in an electrolyte and use thereof - Google Patents

Abstract

In order to regulate the metal ion concentration in an electrolyte fluid serving to electrolytically deposit metal and additionally containing substances of an electrochemically reversible redox system, it has been known in the art to conduct at least one portion of the electrolyte fluid through one auxiliary cell provided with one insoluble auxiliary anode and at least one auxiliary cathode, a current being conducted between them by applying a voltage. Accordingly, excess quantities of the oxidized substances of the redox system are reduced at the auxiliary cathode, the formation of ions of the metal to be deposited being reduced as a result thereof. Starting from this prior art, the present invention relates to using pieces of the metal to be deposited as an auxiliary cathode.

Description

The invention relates to a method and a device for regulating the Concentration of metal ions in an electrolyte fluid. The procedure and the device is particularly applicable for regulating the concentration of copper ions in one for the electrolytic deposition of copper serving and additionally containing Fe (II) and Fe (III) compounds Kupferabscheidelösung.

When galvanizing using insoluble anodes must be ensured be that the concentration of the ions of the metal to be deposited in the electrolyte liquid is kept as constant as possible. This can be, for example be achieved by a loss of the metal ions in the electrolyte liquid, caused by the electrolytic metal deposition is compensated by adding appropriate metal compounds. The However, these are the supply and disposal costs to be expended very large. Another well-known method of supplementing the metal ions in The electrolyte fluid is the direct dissolution of metal in the fluid with an oxidizing agent, for example oxygen. For copper electroplating can metallic copper in an electrolyte fluid containing oxygen enriched from the air, to be dissolved. Ballast salts, i.a. at Compounding with metal salts arise in the electrolyte fluid not in this case. However, galvanizing occurs in both Oxygen at the insoluble anodes of the electrolysis cell. This oxygen attacks the organic additives in the electrolyte, usually for controlling the physical properties of the deposited Metal layer are added to the electrolyte liquid. The oxygen additionally leads to corrosive destruction of the anode material.

To avoid the formation of harmful gases on the insoluble anodes, for example of oxygen and using typical sulfuric copper Verkupferungsbädem which additionally contain chloride ions, including chlorine, DD 215 589 B5 a method for electrolytic metal deposition with insoluble anodes is proposed in which be added to the electrolytic liquid substances of an electrochemically reversible redox system as additives, for example, Fe (NH ₄ ) ₂ (SO ₄ ) ₂ , which transported by intensive forced convection with the electrolyte to the anodes, there electrochemically converted by the electrolysis, according to their turnover by means of intensive forced convection led from the anodes into a metal ion generator, in this at him located regeneration metal with simultaneous external power dissolution of the regeneration metal in its initial state electrochemically reset and medium again in this initial state s intensive forced convection be supplied to the separation vessel. The metal ions formed in the dissolution of metal pieces in the metal ion generator are guided with the electrolyte liquid in the galvanizing.

With this method, the formation of harmful by-products can be linked to the insoluble anodes are avoided. In addition, the electrolytic Metal deposition consumed metal ions by reaction of corresponding metal pieces with the substance of the electrochemically reversible Redox system replenished by placing the pieces of metal with the oxidized substances be oxidized and form the metal ions.

DD 261 613 A1 describes a process using substances of an electrochemically reversible redox system, such as Fe (NH ₄ ) ₂ (SO ₄ ) ₂ , for electrolytic copper deposition, wherein it is stated that organic additives commonly used in the deposition liquid for deposition smooth and high gloss copper layers are not oxidized when performing the process on the insoluble anodes.

DE 43 44 387 A1 likewise discloses a process for electrolytic deposition using copper with predetermined physical properties insoluble anodes and arranged outside the galvanizing cell Copper ion generator as well as of substances of an electrochemical reversible redox system described in the deposition liquid, wherein the Copper ion generator serves as a regeneration space for the metal ions and copper pieces contains. It is stated that when carrying out the in DD 215 589 B5 and DD 261 613 A1 described a decomposition the organic additive was observed in the Abscheideflüssigkeit and that Therefore, during prolonged service life of a deposition bath decomposition products these additives would accumulate in the bath. To solve this problem it is proposed that the substances of the electrochemically reversible redox system to use in a concentration that is just to maintain of the electroplating total copper content in the galvanizing plant leads, and the electrolyte liquid inside and outside the galvanizing cell lead such that the life of the anodes of the electrolytic Cell oxidatively formed ions of the reversibly convertible substance in the entire Galvanoanlage time is limited so that a destruction the additives are avoided or drastically reduced by these ions becomes.

The problem with the mentioned methods and devices is that the metal content in the electrolyte liquid does not readily keep constant leaves. This causes the deposition conditions to change and thus no reproducible conditions can be achieved in the electrolytic deposition are. The change of the metal content in the electrolyte liquid is et al due to the fact that the metal pieces in the metal ion generator not only through the action of the substances of the electrochemically reversible redox system are formed, but in the case of a Kupferabscheidebades using Fe (II) / Fe (III) compounds as substances of the electrochemical reversible redox system also contained in the electrolyte fluid Oxygen from the air.

It has also been found that the oxidized substances of the electrochemical reversible redox system not only in the metal ion generator but also at the cathode in the separator can be reduced, so that the cathodic Current efficiency is only about 90%.

For the above reasons, a stationary state between the Formation of metal ions in the metal ion generator and the consumption of metal ions not by electrolytic metal deposition. Especially when used a higher temperature, this effect is enhanced. The salary the metal ions to be deposited in the electrolyte liquid therefore increases continuously to. However, the content of the metal ions must be within narrow limits be kept sufficiently good physical properties of the deposited To be able to comply with metal layers.

In WO 9910564 A2 this is u.a. indicated that it was not possible, the Concentration of the metal ions in the electrolyte liquid in an additional lower electrolytic secondary cell using an insoluble anode, Just as it is used by conventional electroplating plants with soluble the insoluble anodes used here are known. That is The problem is that the substances of the electrochemically reversible Redox system are oxidized at the anode of the side cell, so that the Increase the content of the oxidized species of these substances in the liquid. In the As a consequence, the content of the metal ions in the electrolyte fluid also continues to increase so that the ultimate goal of lowering the metal ion concentration missed.

In the document mentioned is still additionally as a solution for indicated the problem of permanently diluting the electrolyte fluid. There but this constantly discards large amounts of liquid and disposed of would have to, this is also known as "feed and bleed" procedure known procedure unsatisfactory.

To solve the problem, the document proposes a method and a device for regulating the concentration of metal ions. Thereafter, at least a portion of the electrolyte liquid contained in the electroplating plant is passed through one or more at least one insoluble anode and at least one cathode having auxiliary electrolytic cells and set between the anodes and the cathodes of the auxiliary cells such a high electrical current flow that the current density at the anode surface at least 6 A / dm ² and the current density at the cathode surface is at most 3 A / dm ² . The ratio of the surface of the anodes to the surface of the cathodes is set to at least 1: 4.

With this arrangement, the metal ion content in the electrolyte liquid be kept constant over a longer period of time by a part the oxidized species of the electrochemical contained in the electrolyte liquid reversible redox system is reduced at the cathode of the auxiliary cell. By the ratio of the current densities at the anode and at the cathode in the auxiliary cell, for example, by a suitable choice of the ratio of the surfaces the anode and the cathode are adjusted, the reduced Species of the electrochemically reversible redox system at the anode of the Not auxiliary cell or oxidized only to a minor extent, so that the Concentration of the oxidized species of the electrochemically reversible redox system regulates and thereby directly influences the rate of formation of metal ions can be taken.

However, it has been found that the described in WO 9910564 A2 Device is relatively expensive, since several side cells to the separation vessel must be provided. These are the ones mentioned Auxiliary cell and the metal ion generator. If necessary, in production facilities a plurality of auxiliary cells and metal ion generators are provided become. In addition, at the cathode in the auxiliary cell is constantly metal deposited, so that the efficiency of reduction of the oxidized species of the electrochemically reversible redox system at the cathode is constantly decreasing and thus an increased electrical power is required. As for this used rectifier for powering the auxiliary cell with an elevated Rated power must be interpreted, are again increased system costs required. In addition, the life of this device is through limited a corrosive attack on the anode material.

In addition, the deposited on the cathode of the auxiliary cell copper of Time to time electrochemically removed, so that again additional Energy is consumed and the device during this period not available. Therefore, for continuous production several such auxiliary cells are provided, some of which are for regulation The metal ion concentration can be used while in others parallel auxiliary cells removed the copper from the cathode again becomes. A particular disadvantage here is that the commonly used cathode material is damaged by the Abtösevorgang. This will be the one reduces the efficiency of the reduction. On the other hand, the cathode must be replaced by a new one after a few detachments.

In the event that instead of the insoluble anodes in the electrolytic cell soluble Anodes are used in Patent Abstracts of Japan Vol. 016, no. 512 (C-0998) - JP 04 191394 also an electrolytic auxiliary cell for stabilizing the Quality of copper deposition proposed on a steel wire. In the Electrolytic cell of the device copper is deposited on the steel wire and then transfer the solution to the electrolytic auxiliary cell. There are insoluble Anodes and copper cathodes provided. Copper can in this case from the Solution can be removed by electrolytic deposition, so that the copper content can be set to a predetermined value.

The present invention is therefore based on the problem, the disadvantages avoid the known methods and devices and in particular to find a device and a method with which an economical Operation of the electrolytic deposition method is made possible. Especially should in the deposition insoluble anodes and in the Electrolyte fluid contained substances of an electrochemically reversible redox system be used. The procedure should last for a very long time be carried out under constant conditions. It should in particular the concentration of metal ions in the electrolyte fluid within this Period are kept constant within narrow limits. It's supposed to be be possible, the concentration of metal ions with simple means keeping constant, with only low energy consumption and low equipment costs are to spend.

This problem is solved by the method according to claim 1, the device according to claim 11, the application of the method according to claim 22 and the use of the device according to claim 23. Preferred embodiments The invention are specified in the subclaims.

a. zumindest ein Teil der Elektrolytflüssigkeit durch mindestens eine jeweils mindestens eine unlösliche Hilfsanode und mindestens eine Hilfskathode aufweisende Hilfszelle geleitet wird,

b. zwischen den Hilfskathoden und den Hilfsanoden der Hilfszelle ein Stromfluß durch Anlegen einer Spannung erzeugt wird und

c. Stücke des abzuscheidenden Metalls als Hilfskathoden eingesetzt werden.

The method according to the invention serves to regulate the concentration of metal ions in an electrolyte liquid used for the electrolytic deposition of metal and additionally substances of an electrochemically reversible redox system in an oxidized and a reduced form. It is that

a. at least a part of the electrolyte liquid is passed through at least one auxiliary cell each having at least one insoluble auxiliary anode and at least one auxiliary cathode,

b. a current flow is generated by applying a voltage between the auxiliary cathodes and the auxiliary anodes of the auxiliary cell and

c. Pieces of the metal to be deposited can be used as auxiliary cathodes.

The electrolyte liquid is continuously through the system, in the metal is deposited electrolytically, and the auxiliary cells passed, such that the liquid the plant and the cells at least temporarily at the same time or optionally also flows through one after the other. At the same time the liquid becomes repeatedly returned to the system after flowing through the auxiliary cells.

For electrolytic metal deposition, the metal is made using at least one insoluble, preferably dimensionally stable main anode separated from the electrolyte liquid on the material to be treated. For this a flow of current between the material to be treated and the main anode is generated. The metal ions become in at least one of the electrolyte liquid at least partially flowed through by the metal ion generator as auxiliary cell Substances of the redox system in the oxidized form by dissolution of metal pieces educated. The substances in the oxidized form are under formation corresponding substances, for example metal ions, in the reduced form transformed. The resulting substances in the reduced form become the main anode forming the corresponding substances in the oxidized Form oxidized again.

a. in den Stücke des abzuscheidenden Metalls einfüllbar sind und

b. der mindestens eine unlösliche Hitfsanode und mindestens eine Stromversorgung, vorzugsweise eine Gleichstromquelle, zur Erzeugung eines Stromflusses zwischen der Hilfsanode und den einfüllbaren Metallstücken aufweist,

c. wobei die Metallstücke als Hilfskathoden einsetzbar sind.

The device according to the invention therefore serves for the electrolytic deposition of metal with a metal ion and additionally substances of an electrochemically reversible redox system in an oxidized and a reduced form containing electrolyte liquid and comprises a galvanizing plant with at least one insoluble main anode and at least one standing in liquid connection with the galvanizing metal ion generator, the serves as an electrolytic auxiliary cell,

a. in the pieces of the metal to be deposited are fillable and

b. the at least one insoluble Hitfsanode and at least one power supply, preferably a DC power source, for generating a current flow between the auxiliary anode and the fillable metal pieces,

c. wherein the metal pieces can be used as auxiliary cathodes.

Preferably, anode spaces surrounding the auxiliary anodes and cathode spaces, which surround the metal pieces, by at least partially ion permeable Means separated from each other If necessary, the at least partially ion-permeable means between the anode compartments and the cathode compartments but also omitted. In this case, the auxiliary cathodes are in one liquid quiescent section of the metal ion generator housed, to a mixing of the electrolyte contained in the cathode compartment with the electrolyte liquid in the anode compartment at least largely avoided. For example, the two spaces constructively so from each other be separated that the mixing is largely omitted The metal pieces are preferably in a very well-flowed compartment of the metal ion generator accommodated.

With the method according to the invention and the device, in particular for regulating the concentration of copper ions in an electrolytic one Deposition of copper-serving and additionally Pe (II) and Fe (III) compounds serving copper deposition solution, the metal ion content kept constant within narrow limits in a metal plating solution be so that reproducible deposition conditions are met can. The metal plating solution is continuously from the Gatvanisieranlage, for example, a separation vessel in the inventive Metal ion generator and from there back to the galvanizing transferred. The substances formed on the main anode in the galvanizing plant of the Redox systems in the oxidized form become attached to the metal pieces in the metal ion generator reduced again to form metal ions. By the education rate the substances of the redox system in the reduced form in the metal ion generator by cathodic polarization of the metal pieces opposite An auxiliary anode can be changed, the rate of formation of the metal ions be regulated in the metal ion generator. A renewed oxidation of the reduced Substances of the redox system to the oxidized substances at the auxiliary anode is thereby largely prevents the anode space surrounding the auxiliary anode from which the metal pieces surrounding cathode space is separated. A Mixing of the liquids in the anode and in the cathode compartment becomes extensive avoided, so that the reduced substances of the redox system only in reach the auxiliary anode very small extent, since these substances can only get to the auxiliary anode by diffusion and the concentration of these substances in the anode compartment by the local electrochemical reaction impoverished.

By adjusting the current flow in the metal ion generator, the production rate becomes the substances of the redox system in the reduced form and thus below the rate of formation of the metal ions in the metal ion generator on a Value set so large that the amount produced per unit time Metal ions by oxidation with the redox compounds, plus the amount by the dissolution of the metal by the registered in the electrolyte liquid Atmospheric oxygen is created, exactly the same as the amount of at the Cathode in the electroplating plant consumed metal ions. Thus, the remains Total ion content of the metal to be deposited in the electrolyte liquid constant. When applying the method according to the invention turns so the desired steady state between metal ion formation and their Consumption.

The method according to the invention and the device have opposite to in WO 99/10564 A2 described the further advantage that only one or more secondary cells provided in addition to the electroplating plant and not one or more auxiliary cells and one or more additional metal ion generators. As a result, the expenses for the Plant engineering significantly lower. In addition, the separation solution comes not with an inert auxiliary cathode as described in WO 9910564 A2 Plant in contact, so that a possible deposition of metal on the auxiliary cathode can not lead to the problems discussed above. Therefore the process according to the invention also occurs over a very long period of time without major maintenance, for example, without one in the known device required intermediate detachment of the deposited Metal from the auxiliary cathode. The resulting problem, namely a reduction in the efficiency of the conversion of the oxidized substances of the redox system in the reduced substances by a formed metal coating on the auxiliary cathode, arises using the present invention not a.

Lowering of content of substances of redox system in the oxidized Form in the electrolyte has an additional benefit: The material to be treated in The electroplating plant is located in an electrolyte fluid, which when carried out the inventive method, a reduced concentration of Contains substances of the redox system in the oxidized form. One accordingly smaller amount of the substances of the redox system is from the galvanizing the treated material surface is reduced. The result is an improvement the cathodic current yield in the electroplating plant. The associated Profit in production capacity is up to 10%.

Another advantage of the invention is that of galvanizing Anode sludge known with soluble anodes is eliminated. Nevertheless, can In some cases, a "feed and bleed" operation of the plant may be useful. This is especially true then, if organic and / or inorganic additives in the electrolyte liquid to be exchanged in the long term. As a result of the partial Discarding the electrolyte fluid also becomes the content of the oxidized metal ions proportionately reduced the redox system. To this portion can the Capacity of Metaltionengenerators be reduced. The metal ion content can thus be kept constant by that substances of the redox system be reduced in the oxidized form in the metal ion generator and at the same time removes a part of the electrolyte liquid from the electroplating plant and is replaced by fresh electrolyte fluid.

Preference is given to using precious metals and / or mixed oxides in particular inert metal activated inert metal electrodes as insoluble auxiliary anodes used. This material is opposite the plating solution and the used substances of the redox system chemically and electrochemically stable. For example, titanium or tantalum is used as the base material. Of the Base material is preferably used as a perforated electrode material, for example, in the form of expanded metal or nets to low Space to offer a large surface. As with electrochemical reactions a considerable polarization overvoltage is applied to these metals, are the base materials with a precious metal, preferably platinum, Iridium, ruthenium or their oxides or mixed oxides coated. Furthermore The base material is thus also against electrolytic removal protected. Titanium anodes with an iridium oxide coating that is spherical Bodies are irradiated and thus compressed without pore, are sufficient durable and therefore have a long life among the applied Conditions.

Preferably, metal pieces are used in the form of balls. copper does not need to contain phosphorus like using soluble copper anodes. This reduces the formation of anode sludge. metal balls have the advantage that a reduction in volume of the ball bed in Metal ion generator in the dissolution of the metal pieces not readily to Bridges forming cavities leads, so that the refilling of new pieces of metal is relieved. By using bullets with a suitable Diameter, the bulk volume can be optimized in the metal ion generator. As a result, in turn, the flow resistance or at a given Pump capacity of the volume flow of the deposition solution through the formed Metal ball bed set. But the metal pieces can also essentially be cylindrical or cuboid. It's on a sufficient Ensure flow through the cathode compartment.

Furthermore, in order further to reduce oxidation of substances in the redox system in the reduced form reaching the anode compartment, the ratio of the surface area of the metal pieces to the surface of the at least one auxiliary anode is set to a value of at least 4: 1. As a result, the current density is increased at the auxiliary anode, so that preferably the water of the deposition solution is oxidized to form oxygen and oxidized only to a minor extent, the substances of the redox system in the reduced form. Particular preference is given to a surface ratio of at least 6: 1 and in particular of at least 10: 1. Particular preference is given to ratios of at least 40: 1 and above all of at least 100: 1. Such a high surface ratio can be achieved, for example, by the choice of small metal pieces, in particular metal spheres with a small diameter, can be adjusted. Typically, a cathodic current density of 0.1 A / dm ² to 0.5 A / dm ² and an anodic current density of 20 A / dm ² to 60 A / dm ² sets. Under these conditions, practically only oxygen is formed at the anode. Any substances of the redox system in the reduced form which are present in the anode compartment are practically not oxidized under these conditions.

The metal ion generator may preferably be tubular. A advantageous embodiment in this case is that the auxiliary anode is arranged above the ingestible space of the metal pieces. As a result, the at the auxiliary anode by the anodic water decomposition escape formed oxygen from the deposition solution in the metal ion generator, without being in contact with the metal pieces and without him with the solution in intensive contact with the result that he is in appreciable Dissolves quantities in the solution and in this way to the metal pieces arrives. With this arrangement, therefore, prevents the metal pieces Dissolve at elevated rate by the action of oxygen.

In an alternative, advantageous embodiment, the metal ion generator by vertical division also in two compartments (anode compartment and cathode compartment) be divided, wherein in the one compartment the metal pieces and in the other, the at least one auxiliary anode are arranged. Also in this Trap occurs at the auxiliary anode resulting oxygen without further contact with the pieces of metal from the deposition solution.

The bed of metal pieces preferably rests on a sieve-shaped Electrode, which consists of an inert material, such as titanium. About this electrode, the current can be supplied to the metal pieces. By this electrode is formed Siebförmig, the Abscheidelösung through the sieve to the metal bed and conveyed through it become. Thus, reproducible flow conditions in the Metal fill set. The deposition solution entering the cathode compartment can after passage of the metal fill in the upper region of the cathode space brought out by overflow from the cathode compartment again become. By setting a high flow rate through the bed can, the efficiency of the reduction of the substances of the redox system be increased in the oxidized form on the metal pieces, since the concentration overvoltage for these substances is reduced in the pieces.

The auxiliary anode is made of an anode compartment and the metal pieces of one Surrounded cathode compartment, in which the deposition solution is located. The two Rooms are separated from each other by at least partially ion-permeable means separated. As ion-permeable means may preferably liquid-permeable, non-conductive fabrics are used, such as a polypropylene fabric. This material hinders convection between the electrolyte spaces.

In an alternative embodiment, ion exchange membranes can also be used. These have the further advantage that not only the convection between electrolyte spaces but also the migration can be selectively hindered. If, for example, an anion exchange membrane is used, anions can pass from the cathode space into the anode space, but not cations from the anode space into the cathode space. In the event that a Kupferabscheidelösung with Fe ²⁺ - and Fe ³⁺ ions is used, the Fe ³⁺ ions formed in the anode compartment by oxidation are not transferred into the cathode compartment, so that the efficiency of the erfindüngsgemäßen device is not affected. Upon transfer of these ions into the cathode space, the Fe ³⁺ ions would be reduced to Fe ²⁺ ions in a competing reaction for Cu ²⁺ reduction. Therefore, ion exchange membranes as at least partially ion-permeable agents from a technical point of view are particularly advantageous. However, these materials are also more expensive and mechanically more sensitive than the liquid permeable fabrics.

The metal ion concentration in the deposition solution can be, for example by adjusting the current flow between the auxiliary anode and the metal pieces be regulated. For this purpose, the current is controlled by the power supply. For an automatic control of the metal ion content may additionally a sensor can be provided with which the metal ion concentration in the solution is measured continuously. For this example, the extinction the deposition solution in a separate flowed through by the solution Measuring cell determined photometrically and the output of the measuring cell a Comparator are supplied. The resulting control variable can then in a control variable for adjusting the current to the power supply implemented become. About this stream is primarily the content of the substances of the redox system in the electrolyte fluid. This content in turn influences the dissolution rate at the metal pieces.

The electrolyte liquid is removed from the galvanizing plant, in which the inert Main anodes and the material to be coated are in a forced circulation promoted in the metal ion generator and from this back into the Electroplating. For this purpose, pumps are used, which transfer the liquid promote suitable piping in the forced circulation. If necessary, will Also, a reservoir used between the galvanizing and the metal ion generator is arranged. This reservoir serves for example in addition, the electrolyte liquid for several parallel operated separation vessel to stockpile in a galvanizing plant. Two can do this Liquid circuits are formed, one of which between the Abscheidebehältem and the reservoir, and a second between the reservoir and the metal ion generator is formed. Besides, too Filter media are inserted into the circulation to remove contaminants from the electrolyte fluid to remove. In principle, the metal ion generator be placed in the separation vessel itself, as short as possible To achieve flow paths.

The invention is preferably suitable for the regulation of the concentration of copper ion content in copper baths using dimensionally stable, inert anodes in the separation vessel in which Fe ²⁺ and Fe ³⁺ salts, preferably FeSO ₄ / Fe, are used to maintain the concentration of the copper ions ₂ (SO ₄ ) ₃ or Fe (NH ₄ ) ₂ (SO ₄ ) ₂ , or other salts are included. In principle, the invention can also be used for regulating the metal ion concentration in baths for the electrolytic deposition of other metals, for example zinc, nickel, chromium, tin, lead and their alloys with one another and with other elements, for example with phosphorus and / or boron Case, if appropriate, to use other substances of an electrochemically reversible redox system, wherein the redox system is selected depending on the respective deposition potential. For example, compounds of the elements titanium, cerium, vanadium, manganese, chromium can be used. Usable compounds are, for example, titanylsulfuric acid, cerium (IV) sulfate, alkali metal vanadate, manganese (II) sulfate and alkali chromate or dichromate.

The inventive method and apparatus are particularly applicable suitable for electroplating in horizontal flow systems in which plate-shaped material to be treated, preferably printed circuit boards, in horizontal or vertical position and horizontal direction linearly and thereby moving be brought into contact with the electrolyte liquid. The procedure can of course, also for the galvanization of material to be treated in conventional Diving facilities are used, in which the material to be treated mostly in vertical Orientation is immersed.

Fig. 1:

eine schematische Darstellung einer Anordnung zum Galvanisieren;

Fig. 2:

eine Darstellung des Metallionengenerators in einer ersten Ausführungsform im Querschnitt;

Fig. 3:

eine Darstellung des oberen Bereiches des Metallionengenerators in einer ersten Ausführungsform im Querschnitt;

Fig. 4:

eine Darstellung des Metallionengenerators in einer zweiten Ausführungsform im Querschnitt.

The invention will be explained in more detail with reference to the figures. Show it:

Fig. 1:

a schematic representation of an arrangement for galvanizing;

Fig. 2:

a representation of the metal ion generator in a first embodiment in cross section;

3:

a representation of the upper portion of the metal ion generator in a first embodiment in cross section;

4:

a representation of the metal ion generator in a second embodiment in cross section.

In Fig. 1 , an arrangement for electroplating is shown schematically, which has a separating vessel 1, a metal ion generator 2 and a reservoir 3 . The separation vessel 1 may be formed, for example, as a continuous system for the treatment of printed circuit boards, wherein preferably a sump is provided, is taken from the electrolyte liquid for swelling, spraying on or otherwise in contact Bring with the circuit boards and after contact with the circuit boards again flowing back. The container 1 shown in Fig. 1, the bottoms in this case.

The individual containers are filled with the electrolyte liquid. As electrolyte fluid For example, a sulphurous copper bath can be used, the copper sulfate, sulfuric acid and sodium chloride as well as organic and inorganic additives for controlling the physical properties of the contains deposited metal.

The metal ion generator 2 includes an auxiliary anode 20 and metal pieces 30 . The metal pieces 30 (only partially shown) rest as a bed on a sieve bottom 31 , which is made of titanium. The sieve bottom 31 and the auxiliary anode 20 are connected via electrical supply lines 40,41 with a DC power supply 50 . The sieve bottom 31 is poled cathodically and for this purpose connected to the negative pole of the power supply 50 . The Hitfsanode 20 is poled anodically and connected to the positive pole of the power supply 50 . Via the electrical contact of the metal pieces 30 with the sieve bottom 31 , the metal pieces 30 are also cathodically polarized, so that a current flow between the metal pieces 30 and the auxiliary anode 20 is produced. Between the auxiliary anode 20 surrounding anode space 25 and the cathode space 35, in which the metal pieces 30 are located, an ion-permeable polypropylene fabric 21 is clamped to prevent convective fluid exchange between the spaces 25 and 35 .

The separation vessel 1 is connected to the reservoir 3 in a first fluid circuit: electrolyte liquid is withdrawn in the upper region of the separation vessel 1 via the pipe 4 and transferred to the reservoir 3 . For example, the liquid can be withdrawn from the separation tank 1 via an overflow compartment. The liquid contained in the reservoir 3 is withdrawn in the lower region of the container via a pipe 5 with a pump 6 and passed through a filter unit 7, for example, wound filter cartridges. The filtered solution is returned via the pipe 8 in the separation vessel 1 .

The reservoir 3 is further connected to the metal ion generator 2 via a second fluid circuit: liquid is discharged at the bottom of the reservoir 3 via the pipe 9 and introduced in the lower region below the sieve bottom 31 in the metal ion container 2 . The liquid is withdrawn via an overflow in the upper region of the cathode chamber 35 from the metal ion generator 2 again and returned via the pipe 10 into the reservoir 3 .

2 , a first embodiment of the metal ion generator 2 is shown in cross section. The metal ion generator 2 consists of a tube housing 15, which consists for example of polypropylene and which has a bottom 16 , also made of polypropylene, for example. The tubular housing 15 has an opening 17 on the upper end side. In the lower region of the tubular housing 15 , a liquid inlet 18 is provided for the electrolyte liquid. In the upper region, a liquid outlet 19 is arranged in a corresponding manner. The cross section of the tubular housing 15 is preferably rectangular, square or round.

In the metal ion generator 2 there are an anode chamber 25 and a cathode compartment 35. The anode compartment 25 and the cathode compartment 35 are separated from each other by a wall 24 and an ion-permeable fabric 21 fixed to the lower edge of the wall 24 , in this case a polypropylene fabric. This is shown in detail in Fig. 3 . As a result, the convective fluid exchange between the two chambers 25 and 35 is largely prevented. The wall 24 forms an upper opening and is fixed to the upper end edge of the tubular housing 15 (not shown).

In the anode compartment 25 , the auxiliary anode 20 is housed. In the cathode compartment 35 , the metal pieces 30 are included, in this case no phosphorus-containing copper balls, for example with a diameter of about 30 mm. The copper balls 30 form a bed which rests on a titanium sieve 31 in the lower region of the tubular housing 15 . The auxiliary anode 20 is connected to the positive pole and the sieve bottom 31 to the negative pole of a DC power supply. The Verschraubungsstelle 38 for the anodic current supply from the DC voltage source to the auxiliary anode 20 and the cathodic Verschräubungsstelle 39 for the power line to the sieve bottom 31 are shown schematically in Fig. 3 . In this case, the electrical feeds for the sieve bottom 31 are led out of the top of the metal ion generator 2 isolated.

The tube 9 leads via the liquid inlet 18 into the metal ion generator 2. The liquid inlet 18 is provided below the sieve 31 . The sieve prevents metal pieces or sludge from clogging the tube 9 . The metal ion generator 2 is further connected to the tube 10 at the liquid outlet 19 . The liquid outlet 19 is arranged in the upper region of the metal ion generator 2 . In order to ensure that the metal ion generator 2 is always filled up to the liquid level 22 , the liquid outlet 19 is formed as out of the pipe housing 15 leading pipe 10 having an outlet opening 11 in the upper region of the cathode space 35 . The electrolyte liquid can exit through the outlet opening 11 from the cathode chamber 35 into the pipe 10 . This exit opening 11 is located above the level of the auxiliary anode 20 to ensure that the auxiliary anode 20 is always within the liquid.

Coming from the reservoir 3 or directly from the separation vessel 1 electrolyte liquid containing in addition to copper ions also formed on the main anode Fe ³⁺ ions and optionally additionally contains Fe ²⁺ ions is pumped through the liquid inlet 18 into the metal ion generator 2 . The liquid then enters in the direction of the arrow 23 through the sieve bottom 31 into the cathode space 35 , in which the copper balls 30 are located. By reaction of the Fe ³⁺ ions with the copper, Cu ²⁺ ions are formed, at the same time Fe ²⁺ ions are formed. The rate of formation of the copper ions can be regulated by cathodic polarization of the copper balls 30 via the sieve bottom 31 : By increasing the cathodic potential on the copper balls 30 , the rate of formation of the Cu ²⁺ ions is suppressed. The enriched with Cu ²⁺ ions solution occurs in the upper region of the cathode chamber 35 through the opening 11 via the liquid outlet 19 from the metal ion generator 2 again. By applying a cathodic potential to the sieve bottom 31 and thus to the copper balls 30 and an anodic potential to the auxiliary anode 20 in the anode compartment 25 , the electrochemical reaction is made possible. The water of the electrolyte liquid contained in the anode chamber 25 is anodically oxidized to oxygen, which exits from the upper portion of the metal ion generator 2 through the opening 17 . Optionally, Fe ²⁺ ions contained in the anode space 25 are also oxidized on the auxiliary anode 20 . Since the fluid communication between the cathode chamber 35 and anode chamber 25 is greatly hindered by the separation 21,24 which deplete Fe ²⁺ ions in the anode compartment 25 so that their concentration in the steady-state operation is close to zero.

FIG. 4 shows a second embodiment of the metal ion generator 2 according to the invention. The metal ion generator 2 in this case is a container with side walls 15 which form a rectangular, square or round outline of the metal ion generator 2 . The container also has a bottom 16 . The walls 15 and the bottom 16 are made of polypropylene. At the top, the metal ion generator 2 forms an opening 17.

The metal ion generator 2 in turn has a cathode space 35 and an anode space 25 . The spaces 25 and 35 are further separated by an ion-permeable wall 21, in this case an ion exchange membrane, preferably an anion exchange membrane, which is arranged vertically. Further, a perforated wall 26 is provided, which gives the membrane the necessary stability.

In the cathode compartment 35 , a sieve bottom 31 is arranged in the lower region, which is formed by a titanium mesh. On the sieve bottom 31 rests a bed of metal pieces 30 (only partially shown), here copper balls with a diameter of about 30 mm. An auxiliary anode 20 is accommodated in the anode compartment. The auxiliary anode 20 is connected to the positive pole and the sieve bottom 31 to the negative pole of a DC power supply (not shown).

The electrolyte liquid may enter the metal ion generator 2 through the lower liquid inlet 18 . The liquid inlet 18 is arranged below the sieve bottom 31 . Liquid can exit via an upper liquid outlet 19 from the metal ion generator 2 again. The outlet 19 is arranged in the upper region of the cathode space 35 .

The operation of the metal ion generator 2 in this embodiment is the same as that of the first embodiment in Figs. 2 and 3. In this regard, reference is made to the above explanations.

List of reference numerals:

1

separating vessel

2

Metal ion generator

3

reservoir

4,5,8,9,10

piping

6

pump

7

filter unit

11

outlet opening

15

Tube housing of the metal ion generator 2

16

Bottom of the metal ion generator 2

17

front-side upper opening of the metal ion generator second

18

Liquid inlet into the metal ion generator 2

19

Liquid outlet from the metal ion generator 2

20

auxiliary anode

21

ion-permeable agent (tissue)

22

liquid level

23

Flow direction of the electrolyte liquid

24

Wall for separating the anode compartment 25 from the cathode compartment 35

25

anode chamber

26

perforated partition

30

Pieces of metal, copper balls

31

Sieve bottom, titanium net

35

cathode space

38

electrical contact to the power supply to the auxiliary anode 20th

39

electrical contact to the power supply to the sieve bottom 31st

40

electrical supply to the auxiliary anode 20th

41

electrical supply to the sieve bottom 31

50

Power supply, DC source

Claims (23)

1. Method for regulating the concentration of metal ions in an electrolyte fluid used for the electrolytic deposition of metal and additionally containing substances of an electrochemically reversible redox system in an oxidised and in a reduced form, in which at least a portion of the electrolyte fluid is led through at least one auxiliary cell, each having at least one insoluble auxiliary anode and at least one auxiliary cathode between which a flow of current is generated by the application of a voltage,
   characterised in that
   pieces of the metal (30) to be deposited are used as at least one auxiliary cathode.
2. Method according to claim 1, characterised in that anode spaces (25), which surround the auxiliary anodes (20), and cathode spaces (35), which surround the metal pieces (30), are separated from one another by means (21) which are at least partially permeable by ions.
3. Method according to one of the preceding claims, characterised in that inert metal electrodes which have been activated with precious metals and/or mixed oxides are used as insoluble auxiliary anodes (20).
4. Method according to one of the preceding claims, characterised in that the metal pieces (30) are used in the form of balls.
5. Method according to one of the preceding claims, characterised in that the ratio of the surface of the metal pieces (30) to the surface of the at least one auxiliary anode (20) is set to a value of at least 4:1.
6. Method according to one of the preceding claims, characterised in that the auxiliary cell (2) is in the form of a tubular metal ion generator and in that the at least one auxiliary anode (20) is arranged above the metal pieces (30).
7. Method according to one of claims 1 to 5, characterised in that the auxiliary cell (2) is in the form of a metal ion generator and is vertically divided into an anode space (25) and a cathode space (35), the metal pieces (30) being arranged in the cathode space (35) and the at least one auxiliary anode (20) being arranged in the anode space (25).
8. Method according to one of the preceding claims, characterised in that current is supplied to the metal pieces (30) via a sieve-shaped electrode (31).
9. Method according to one of the preceding claims, characterised in that the at least partially ion-permeable means (21) is in the form of a woven cloth which is permeable by liquid.
10. Method according to one of claims 1 to 8, characterised in that an ion exchange membrane is used as the ion-permeable means (21).
11. Apparatus for the electrolytic deposition of metal which has an electrolyte fluid containing metal ions and additionally substances of an electrochemically reversible redox system in an oxidised and a reduced form, comprising

    I. an electroplating system having at least one main anode and

    II. at least one auxiliary cell which is in fluid connection with the electroplating system and comprises respectively

    a. at least one insoluble auxiliary anode,

    b. at least one auxiliary cathode comprising pieces of the metal (30)which is to be deposited, as well as

    c. at least one power supply for generating a flow of current between the at least one auxiliary anode and the at least one auxiliary cathode,

       characterised in that the main anode is insoluble.
12. Apparatus according to claim 11, characterised in that at least partially ion-permeable means (21) are provided which separate from each other anode spaces (25), which surround the auxiliary anodes (20), and cathode spaces (35) which may be filled with the metal pieces (30).
13. Apparatus according to one of claims 11 and 12, characterised in that the insoluble auxiliary anodes (20) are inert metal electrodes which have been activated with precious metals and/or mixed oxides.
14. Apparatus according to one of claims 11 to 13, characterised in that the metal pieces (30) are metal balls.
15. Apparatus according to one of claims 11 to 14, characterised in that the ratio of the surface of the metal pieces (30) to the surface of the at least one auxiliary anode (20) is at least 4:1.
16. Apparatus according to one of claims 11 to 15, characterised in that the apparatus (2) is in the form of a tubular metal ion generator and in that the at least one auxiliary anode (20) is arranged above a space containing the metal pieces (30).
17. Apparatus according to one of claims 11 to 15, characterised in that the apparatus (2) is vertically divided into the anode space (25) and the cathode space (35), the metal pieces (30) being able to be filled into the cathode space (35) and the at least one auxiliary anode (20) being arranged in the anode space (25).
18. Apparatus according to one of claims 11 to 17, characterised in that a sieve-shaped electrode (31) is arranged in the cathode space (25) in such a way that current can be supplied to the metal pieces (30) via this electrode (31).
19. Apparatus according to claim 18, characterised in that the sieve-shaped electrode (31) is arranged in the lower portion of the cathode space (35) in such a way that the metal pieces (30) can rest on it.
20. Apparatus according to one of claims 11 to 19, characterised in that the at least partially ion-permeable means (21) is in the form of a woven cloth which is permeable by liquid.
21. Apparatus according to one of claims 11 to 19, characterised in that the at least partially ion-permeable means (21) is an ion exchange membrane.
22. Application of the method according to one of claims 1 to 10 for regulating the concentration of copper ions in a copper deposition solution used for the electrolytic deposition of copper and additionally containing Fe(II) and Fe(III) compounds.
23. Use of the apparatus according to one of claims 11 to 21 for regulating the concentration of copper ions in a copper deposition solution used for the electrolytic deposition of copper and additionally containing Fe(II) and Fe(III) compounds.

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