DE60223934T2 - PRECIOUS METAL RECOVERY - Google Patents

Abstract

Various methods have been proposed to separate precious metal from a fluid utilized for plating. The known methods and devices are complicated and expensive. To overcome this problem, a method and a device for plating work pieces with a fluid containing at least one precious metal are provided. According to the invention the work pieces are contacted with the fluid and the fluid is filtered, after use, through at least one ceramic membrane filter in order to separate the at least one precious metal from the fluid. According to the invention a ceramic membrane filter having an exclusion pore size in excess of 10,000 Dalton is utilized.

Description

The The invention relates to a coating method and apparatus of workpieces using a palladium-containing liquid. The invention is especially applicable in processes for the production of electrical circuit carriers.

To the Electroplating of workpieces have to their surfaces first be treated so that they become electrically conductive, if the workpieces non-conductive surfaces exhibit. For this purpose, the workpieces are immersed in a solution, which contains palladium in ionic, ionogenic or colloidal form. palladium may be present in ionic form, in particular as a salt, for example as palladium chloride, which is generally dissolved in a hydrochloric acid solution. In ionic form, palladium is present as a complex, for example as Aminopyridinkomplex. Colloidal palladium can be different Containing protective colloids, for example, a tin (II) chloride formed or consisting of an organic polymer protective colloid. The on the surfaces the workpieces then adsorbed palladium nuclei serve, for example, as Activators for starting an electroless metal deposit, through which are on the surfaces an electrically conductive Layer forms so that the surfaces subsequently with can be metallized any metals. This procedure will For example, for the production of printed circuit boards and other circuit boards as well of metallized parts for the plumbing, Automotive and furniture industry used, in particular for the chrome plating of plastic parts.

The Palladium-containing solution may also be used to form an electrically conductive layer. In this Direktgalvanisierungsverfahren further metal is after the palladium treatment applied electrolytically, without previously a metal layer formed with an electroless metallization process becomes.

at the treatment of the workpieces with electrically non-conductive surfaces remains part of the palladium containing solution on the workpieces stick when the first dipped workpieces from this solution be dug. The adherent solution is usually rinsed with water.

For example in known activation processes with colloidal palladium a solution usually used contains about 50 to 400 mg / l of palladium. In the treatment of Plastic parts with a geometric surface of one square meter typically about 5 to 10 mg of palladium are adsorbed. These Quantity is going for the activation of the plastic surface needed. Leaving the ones to be treated workpieces the corresponding treatment station, remain about 0.2 l activation solution per square meter on the surfaces back and are taken out of the bath. Therefore, go about 10 to 50 mg of palladium from the bath is lost by removing the adhering solution The treatment bath towed out, then rinsed and transferred to wastewater treatment.

Also in the direct galvanization of electrically non-conductive surfaces without electroless metallization become palladium-containing solutions used. In this case, there is a higher concentration of palladium of, for example, 400 mg / L in the solution.

The carryover of palladium from the treatment solution when carrying out the known direct metallization process is about 50 mg / m ² . By suitable measures, for example by prior adsorption of polyelectrolyte compounds on the non-conductor surfaces, the adsorption of the palladium particles can be increased from a relatively low value to about 50 mg / m ² workpiece surface. Nevertheless, about 60 to 70% of the palladium used is lost in the solution due to carryover. Only 40 to 30% are actually available for the metallization of the workpiece surfaces.

For example, it is known to recover palladium from process solutions. For example in U.S. Patent No. 4,078,918 For example, a process for recovering, for example, palladium from various materials is described in which palladium is in dissolved or undissolved form. The materials are first treated with an oxidizing agent to destroy possible organic constituents and then with ammonium hydroxide to form amine complexes. The resulting palladium complexes are then reduced with ascorbic acid, so that palladium precipitates as metal from the process solution and can be filtered off.

Further, "Reclamation of palladium from colloidal seed solutions" in Chemical Abstracts, 1990: 462908 HCAPLUS describes a process for recovering palladium from solutions of colloidal Pd / SnCl ₂ as a pretreatment prior to electroless plating, where the solution is for 24 hours fumigated with air so that palladium is flocculated. The precipitate is separated, dried and processed.

In "Recovery of palladium and tin dichloride from waste solutions of colloidal palladium in tin dichloride "in Chemical Abstracts, 1985: 580341 HCAPLUS is a method of precipitation of Palladium described by addition of metallic tin at 90 ° C.

In U.S. Patent No. 4,435,258 discloses another process for recovering palladium from spent baths used to activate electrically non-conductive surfaces for subsequent electroless metallization. The activation solutions are worked up by oxidizing the colloidal palladium into the solution by adding an oxidizing agent, for example hydrogen peroxide, then heating the solution to destroy the residual hydrogen peroxide and then palladiumizing these solutions electrolytically on a cathode.

Finally, a process for the recovery of palladium from Pd / SnCl ₂ solutions is described in "Recovery of the colloidal palladium content of exhausted activating solutions used for the current-free metal coating of resin surfaces" in Chemical Abstracts, 1976: 481575 HCAPLUS the palladium is precipitated by the addition of concentrated nitric acid and filtered off.

In DE 100 24 239 C1 For example, a process is described for electrolytically plating workpieces with a palladium colloid solution by contacting the workpieces with the colloid solution, wherein palladium is recovered after use of the colloid solution by separating palladium colloid particles from the colloid solution with a membrane filter. For example, ceramic materials can be used for filtration. The pore size of these membranes is 200 to 10,000 daltons. It is stated that the palladium particles pass through the membrane filter using a pore cutoff greater than 10,000 daltons.

The known methods for the electrolytic metallization of workpieces with a palladium colloid solution are expensive and expensive.

The The main problem of the present invention is the disadvantages to avoid the known method and a method for galvanotechnischen Treatment of workpieces to find with a palladium-containing liquid that is inexpensive to carry out. During execution The process should require only small amounts of additional chemicals be. Furthermore should the process with little energy and time feasible and especially low maintenance.

Is solved this problem by the method of claim 1. Preferred embodiments of Invention are in the subclaims specified.

The inventive method used for metallization of workpieces with a palladium-containing Liquid, the workpieces with the liquid be brought into contact. For the recovery of the precious metal from the liquid is this with chemical substances selected from the group comprising pH adjusting agents, reducing agents, sulfur compounds, selenium compounds and tellurium compounds mixed so that the palladium is changed so that during it The filtration is essentially completely retained and it becomes then filtered through at least one ceramic membrane filter to the palladium from the liquid to separate, wherein the ceramic membrane filter an exclusion pore size of more than 10,000 daltons. The filtration causes the palladium to precipitate out the liquid separated.

When Electroplating treatment is every on a surface modification the workpieces directed treatment with liquids understood, as far as in the liquid Palladium is included. Exceptions are, however, methods for coating the workpieces with polymer coatings, in particular methods of painting.

The to be treated workpieces shut down metallic workpieces, non-metallic workpieces and both metallic and non-metallic materials existing workpieces one. The workpieces can occur in all conceivable forms and for all conceivable uses be provided. Preferred parts are semi-finished products for production of circuit boards, in particular for the production of printed circuit boards and of hybrid circuit carriers, for example of multichip modules.

The liquid especially a solution be. This is especially the case when the palladium in ionic or ionogenic form. As an ionic form of palladium are dissolved in particular Salts of palladium in water or in another the dissociation favoring the salts solvent Understood. Among the ionic form of palladium are palladium complexes understood, in particular complexes of the ions of palladium with organic Complex ligands. The complexes can be uncharged be present or as ions. The liquid can also act as a colloid present, in particular as a colloid of elemental palladium.

The Palladium-containing liquid can both a treatment liquid for the Be workpieces as well as a rinsing liquid. Under a treatment liquid becomes a liquid understood that to change the surface properties the workpieces serves, for example, a coating liquid, including a Activation liquid, a cleaning liquid, an etching liquid o. Ä. Im In contrast, a rinsing liquid is used exclusively in addition, after the treatment of a workpiece with the treatment liquid still adhering to the workpiece surface treatment liquid rinse.

The Palladium becomes electroplating after use of the liquid Treatment of workpieces over the filtered at least one ceramic membrane filter. It means that the liquid first used for galvanic treatment and only then for reclamation the palladium contained therein is filtered through the membrane filter becomes. For example, the liquid by spraying, spraying, Bulging or blasting brought into contact with a workpiece, the from the workpiece outflowing liquid collected and the collected liquid immediately thereafter guided to the membrane filter become. The collected liquid can also be held back in a collection container and from there again to the workpiece promoted become. The liquid can in this case either after a predetermined period of use collected led to the membrane filter be (discontinuous process), or a part of the liquid can be continuously diverted from the sump and the membrane filter guided be (continuous process). In this case, a stationary filling state in the collection container Achieving becomes ongoing new treatment fluid tracked in an amount per unit of time in the sump, the is just as big as the amount of per unit time passing the membrane filter Liquid. The workpieces can also by immersion with itself in a treatment container befindender treatment liquid be brought into contact. In this case, the treatment liquid after use either after a predetermined period of use collected led to the membrane filter (discontinuous process), or a part of the liquid in the treatment tank can be continuously diverted from the treatment tank and the membrane filter guided be (continuous process).

With the method according to the invention Is it possible, in a simple way with low use of chemicals, energy and time as well as maintenance in continuous operation a substantial Separation of palladium from the spent process solutions too to reach. In particular, there is the possibility of the consumed process solutions work up again after separation of the fraction containing the palladium, so that the palladium can be completely recycled back into the process can.

Compared to the method for recovering palladium from colloidal Pd / SnCl ₂ described in Chemical Abstracts, 1990: 462908 HCAPLUS, the present method has the advantage that the separation of the fractions is complete, while in the precipitation method described in Chemical Abstracts a non-negligible part of the Palladium is oxidized to its divalent, soluble stage, so that it can not be completely separated by filtration from the solution. Therefore, this part of the palladium can not be recovered, so it is lost.

One Another advantage of the method according to the invention over the in Chemical Abstracts, 1985: 580341 HCAPLUS is that it does not require a considerable effort to use additional Chemicals, such as metallic tin, as well as for this known methods of required energy and time for heating the colloid solution to operate.

The inventive method also has opposite to in U.S. Patent No. 4,435,258 described method, on the fact that palladium can be removed from the solutions practically completely, while in the method according to U.S. Patent No. 4,435,258 especially at low palladium concentration, which sets after a long electrolysis time, only an extremely low current efficiency can be achieved. A complete removal of the palladium is therefore either very expensive or not possible in this known method either.

in the In contrast to that described in Chemical Abstracts, 1976: 481575 HCAPLUS The method is the method and the device according to the present invention Invention especially for suitable for continuous operation. The in this document illustrated method comes as well not without additional Chemicals off.

Surprisingly, contrary to in DE 100 24 239 C1 given properties of membrane filters having a pore size of significantly more than 10,000 daltons, after which the palladium particles of colloidal palladium colloid pass through the filter, found that the separation properties of ceramic filters with a pore size exclusion of, for example, 20,000 daltons are excellent in terms of colloidal palladium. For this purpose, reference is made, by way of example, to experiments Nos. 1 and 2 in Example 1.

• a. Die Rückgewinnung von Palladium aus ionischen, ionogenen und kolloidalen Lösungen ist mit einer einzigen Vorrichtung möglich. Mehrere angepasste Vorrichtungen sind nicht erforderlich. Daher können die Lösungen vermischt und gesammelt aufgearbeitet werden. Dies gilt in gleicher Weise auch für die Behandlungs- und Spülflüssigkeiten: Behandlungsflüssigkeiten mit Palladium in hoher Konzentration können mit Spülflüssigkeiten mit Palladium in sehr niedriger Konzentration gemischt und dann gemeinsam verarbeitet werden.
• b. Gegen Chemikalien und Temperatureinflüsse weitgehend unempfindliche Keramikmembranfilter können eingesetzt werden, da eine Abtrennung von Palladium auch mit den bei Keramikmembranfiltern größeren Poren gelingt. Daher besteht ein geringer Wartungsaufwand, da die Filter keine häufige Reinigung erfordern. Keramikmembranfilter haben auch eine hohe Lebensdauer. Palladium adsorbiert nicht auf dem Membranmaterial.
• c. Die zu behandelnde Flüssigkeit kann in einem sehr einfachen Verfahren aufgearbeitet werden. Beispielsweise ist es zur Vermeidung der Auflösung von kolloidalen Teilchen in der Flüssigkeit nicht erforderlich, unter Schutzgasatmosphäre zu arbeiten.

The method and apparatus according to the present invention have the following advantages over known methods and apparatuses:

• a. The recovery of palladium from ionic, ionic and colloidal solutions is possible with a single device. Multiple custom devices are not required. Therefore, the solutions can be mixed and worked up in a batch. This applies equally to the treatment and rinsing liquids: treatment liquids with palladium in high concentration can be mixed with rinsing liquids with palladium in very low concentration and then processed together.
• b. Ceramic membrane filters which are largely insensitive to chemicals and temperature influences can be used, since separation of palladium is also possible with larger pores in ceramic membrane filters. Therefore, there is little maintenance because the filters do not require frequent cleaning. Ceramic membrane filters also have a long service life. Palladium does not adsorb on the membrane material.
• c. The liquid to be treated can be worked up in a very simple process. For example, to avoid the dissolution of colloidal particles in the liquid, it is not necessary to operate under a protective gas atmosphere.

colloidal Palladium-based activators contain palladium particles, that of a protective Shell surrounded are (protective colloid). Investigations with high-resolution electron microscopy (HTEM) and atomic force microscopy (AFM) have shown that the palladium particles have a diameter of at least 2.5 nm. The mean particle diameter is about 4 nm, the particle size distribution the Gaussian curve follows. In studies on a rinsing liquid, which after treatment of workpieces was obtained with the colloidal activator, was a broad particle size distribution determined, the particles with a maximum size of about 18 nm and smaller Particles (2 to 18 nm) had.

Practically used colloid solutions are acidic, often strongly salted, and contain chloride ions as well optionally tin in the oxidation states (II) and (IV) or organic, polymeric stabilizers, such as gelatin or polyvinylpyrrolidone, and reducing agents. With the exception of the polymers, which in minor Quantities are used, are all other substances contained therein Ionic. It is believed that these ionic constituents are essential smaller than the palladium particles.

It is surprising that with suitable membrane filters with different porosity palladium particles from these colloid solutions very selective and complete can be removed although in the case of tin-containing colloidal solutions simultaneously existing tin in high concentration (usually in more than 70 times the palladium concentration) and though the tin compounds for it are known to form colloidal and difficult to filter solutions.

to Ultrafiltration are different types of membranes made of different ones Materials have been studied. It turned out that it was at the selection of the membrane filter in particular to a sufficient stability the membrane filter opposite the palladium-containing liquid arrives, for example 15% by weight of hydrochloric acid may contain.

to Separation of the palladium colloid particles becomes ceramic membrane filters used that has an exclusion pore size of about 15,000 daltons about 25,000 daltons, in particular an exclusion pore size of about 17,500 daltons to about 22,500 daltons, and most preferably from about 20,000 daltons.

A preferably used ceramic membrane filter is made of an alumina, in particular α-Al ₂ O _3, titania and optionally zirconia-containing ceramic material. Basically you can Other filter materials are used. In general, the filter material is applied to a highly porous support body, which gives the filter the required mechanical stability. This support body may for example consist of α-Al ₂ O ₃ or of SiC (silicon carbide).

Of the Filter may be in the form of a disk or as a tube. In the former case, the disk is about perpendicular to its surface flows, wherein the flow is deflected in the radial direction. Between the two disc surfaces becomes built up a pressure difference, allowing permeate through the disc can pass through. If the filter is in the form of a tube is, the liquid becomes conveyed in the axial direction through the tube, wherein a pressure difference built between the interior and the exterior of the tube becomes. This allows permeate to pass through the pipe wall, for example, from the interior of the pipe to the room outside of the pipe. The second method is called dynamic filtration designated. In this case, the palladium in the interior of the Pipe held back while the largely freed of palladium liquid through the pipe wall from the interior of the tube to the space outside the tube passes.

Some liquids can be filtered directly without further pretreatment. In this case Very good results are obtained with the ceramic membrane filters.

The to be processed liquids be first chemically pretreated. For this, the liquid is after their use for galvanic treatment and before filtration through the Membrane filter mixed with chemical substances suitable are to change the palladium so that it is filtered practically complete retained becomes. It is believed that the particle size of palladium by adding of these chemicals is changed so that the palladium containing particles do not pass through the pores of the membrane filter can. It should be sufficient, the average particle size to one Adjust value above about 10 nm when the particle size follows the Gaussian distribution. In that case, would already a membrane filter with an exclusion pore size of more as 10,000 daltons practically the entire amount of palladium in the concentrate hold back. In a similar way can larger particles be adjusted by adding these chemicals, though Membrane filter used with a larger exclusion pore size become.

If Palladium in the solution is present in ionic and / or ionic form, the liquid mixed with chemical substances that are selected from the group comprising reducing agents, sulfur, selenium and Tellurium compounds. As chemical substances for pretreatment particularly preferred substances selected from the group comprising borohydrides, Amine boranes, hypophosphites, inorganic sulfides and organic thio compounds, in particular the alkali metal and ammonium salts of dimethyldithiocarbamate, sulphides, borohydrides, for example tetrahydroboranate, and hypophosphites. In particular, as organic thio compounds Considered organic compounds in which sulfur is simple or is doubly bound to one or two carbon atoms, with one Single or double bond is formed, so for example thiols, Sulfides, disulfides and polysulfides, thioamides and thioaldehydes.

If Palladium in the liquid in colloidal form, pH adjusting agents are used as chemical substances used. The liquid is mixed with the pH adjusting agents such that the pH the solution ranging from 3 to 12.

In both traps will be a solution obtained, which is ideal for the separation of palladium.

• a. Die Vorbehandlung ist äußerst einfach. Es genügt, die das Palladium enthaltenden Flüssigkeiten mit den erforderlichen Substanzen bzw. mit dem pH-Einstellmittel zu vermischen.
• b. Der Aufwand an zusätzlichen Chemikalien ist äußerst gering. Für die Behandlung von 200 l Spülwasser aus der Behandlung mit einer wässrigen Lösung eines organischen Palla diumkomplexes (7 mg/l Pd) werden lediglich 7,5 ml einer 467 g/l Natriumdimethyldithiocarbamat enthaltenden Lösung benötigt. Falls Spülwasser aus der Behandlung mit einem Palladiumkolloid (organisches Schutzkolloid, 25 mg/l Pd) zu verarbeiten sind, sind bereits 0,5 l einer wässrigen Lösung von 432 g/l NaOH ausreichend.

With this development of the present invention, the following advantages result:

• a. The pretreatment is extremely simple. It is sufficient to mix the palladium-containing liquids with the required substances or with the pH adjusting agent.
• b. The cost of additional chemicals is extremely low. For the treatment of 200 l of rinse water from the treatment with an aqueous solution of an organic Palla diumkomplexes (7 mg / l Pd) only 7.5 ml of a solution containing 467 g / l Natriumdimethyldithiocarbamat required. If rinse water from the treatment with a palladium colloid (organic protective colloid, 25 mg / l Pd) are to be processed, already 0.5 l of an aqueous solution of 432 g / l NaOH are sufficient.

• a. werden die Werkstücke mit einer Palladium enthaltenden Behandlungsflüssigkeit in Kontakt gebracht,
• b. wird die an den Oberflächen der Werkstücke anhaftende Behandlungsflüssigkeit danach mit Spülflüssigkeit entfernt, und
• c. werden die Behandlungsflüssigkeit und/oder die Spülflüssigkeit zu deren Filtration (vorzugsweise unter Druck) durch den mindestens einen Keramikmembranfilter geleitet, wobei die durch den mindestens einen Membranfilter hindurchgeleitete Flüssigkeit eine Permeatflüssigkeit und die nicht durch den mindestens einen Membranfilter hindurchgeleitete Flüssigkeit eine Konzentratflüssigkeit ist.

From the observations and investigations that led to the present invention, it was possible to deduce that it is possible to recover palladium with membrane filters from rinsing liquids and / or treatment liquids. For this

• a. the workpieces are brought into contact with a treatment liquid containing palladium,
• b. the adhering to the surfaces of the workpieces treatment liquid is then removed with rinsing liquid, and
• c. the treatment liquid and / or the rinsing liquid are passed through the at least one ceramic membrane filter for filtration thereof (preferably under pressure), wherein the liquid passed through the at least one membrane filter is a permeate liquid and the liquid not passed through the at least one membrane filter is a concentrate liquid.

The Workpieces, preferably made of electrically non-conductive material are, after treatment with a palladium-containing liquid rinsed in a suitable device with a rinsing liquid by they are immersed in it, by swelling or preferably spray the rinsing liquid on the workpieces, around the volume of the rinse solution so low as possible to keep. Subsequently becomes the rinsing fluid passed through a ceramic membrane filter with a pressure pump, which restrains the palladium particles and ensures that that the rinse water is allowed through. This permeate can then be transferred to wastewater treatment.

In front passing the treatment liquid and / or the rinsing liquid over the Membrane filter can / can these are mixed with the chemical substances, for example with the reducing agents, sulfur, selenium, tellurium compounds or pH adjusting agents.

In a particularly preferred embodiment the invention is exclusive the rinsing liquid or a preferably up to 5 vol .-% treatment liquid containing rinse liquid (preferably under pressure) passed through the membrane filter. The workpieces be with fresh rinse solution in Brought in contact, being constantly a predetermined amount of fresh rinse solution per unit time is available. The amount of permeate liquid formed per unit time In particular, it can be set to about the same size as the Amount of per unit time with the workpieces brought into contact Rinsing liquid. This will be a stationary Condition achieved in the treatment plant: By just as much fresh rinse to the workpieces promoted like permeate liquid discharged from the plant is, results in the balance a constant material flow. This of course applies only if the amount of added chemical substances negligible and if other influencing factors do not In the Practice could namely the evaporation / evaporation of rinsing liquid an essential role play.

restrained Palladium, in the form of a homogeneous dispersion of metal or a metal compound, for example in the form of a PdS dispersion, is present as a concentrate, can be reprocessed. The restrained For example, palladium may be dissolved, converted to palladium chloride and for the re-synthesis of a treatment liquid containing palladium used or otherwise used. The palladium-containing concentrate solution can also be largely concentrated to dryness in a filter press become. For this, the concentrate liquid originating from the membrane filter is used in a container in which, in the concentration formed, palladium containing sludge settles, and the sludge suspension to the filter press is directed. The obtained with the filter press, containing palladium Filter cake can be used as starting material for the production of pure Palladium and palladium compounds are used.

The Device for galvanic treatment of workpieces with a palladium-containing liquid typically has means for contacting the liquid with the workpieces as well as holding means for the workpieces on.

The Means for contacting the liquid with the workpieces are for example, nozzles, from which treatment or rinsing fluid sprayed on the workpiece surfaces, sprayed, is swelled or blasted. This arrangement will be, for example then used when the liquid with high flow velocity to the surface should arrive or if the amount of liquid needed to be minimized. In another embodiment The invention relates to the means for contacting around treatment container, in which the treatment liquid located and in which the workpieces be immersed.

The Holding means for the workpieces can also occur in very different embodiments: For example can the workpieces in conventional Way with clamps, clamps, pliers or screw fasteners being held. Furthermore, can the workpieces also simply held in a horizontal position on wheels, wheels or rollers, transported and guided or be clamped between them.

The Device further comprises in addition to the features mentioned a Device for separating the palladium from the liquid. This device is equipped with at least one ceramic membrane with a Exclusion pore size of more equipped as 10,000 daltons. Furthermore the device has at least one pump for delivery the liquid to the at least one membrane and liquid guides to promote the liquid from the means for contacting the liquid with the workpieces the at least one ceramic membrane. Under a pump is too any non-motorized pump or just one by gravity driven fluid delivery to understand.

According to the before specified versions has the means for separating the palladium from the liquid furthermore a mixing device. With this mixing device may be from the means for bringing the liquid into contact with the workpieces coming liquid mixed with chemical substances. All can do this usual Mixing devices are used, which consist of chemical reaction technology are known, for example, stirring and mixing zones in flow reactors.

Further may be the means for separating the palladium from the liquid also have a multi-phase separation unit in which sludge can settle, which has formed during the separation from the liquid and that of the device for separating the palladium from the liquid comes. Such a multi-phase separator is, for example through a settling tank formed in which virtually no liquid convection takes place. The sludge suspension can then be sent to a filter press, around the predominantly Palladium-containing sludge largely pure and dry.

to Further illustration of the invention serve the following described figures. They show in detail:

1 a perspective, schematic representation of a ceramic membrane filter;

2 : A schematic representation of a device according to the invention for electroplating treatment of workpieces.

In 1 is a ceramic membrane filter in the form of a tube 1 played. The tube is made of a highly porous ceramic material as a carrier 3 , in the present case alumina. The carrier 3 is on the inside with another ceramic layer of an oxide as a membrane filter layer 2 Mistake. This membrane filter layer 2 in turn consists of two layers (not shown), namely a first microfiltration layer of α-Al ₂ O ₃ and a second ultrafiltration layer of ZrO ₂ and TiO ₂ , wherein TiO _{2 has} the finest pore size, so that a filtration with an exclusion pore size, for example 20,000 daltons is possible. The membrane filter layer 2 has an exclusion pore size of about 20,000 daltons. Thus, the mean pore size is about 20 nm.

The tube has an inner diameter of about 6 mm. The length of the tube is about 1000 mm. The flow gets there under pressure in the reference numeral 4 designated flow direction therethrough. The pressure difference between the pipe inlet and the pipe outlet is in the range of 1.5 to 3 bar.

Around to capture the permeate passing through the inner tube wall, the ceramic tube is concentrically mounted in another tube.

In the lower part of the 2 are two of the most in 1 illustrated filter tubes 1 reproduced, the filter tubes 1 Part of ceramic tubes with several holes of in 1 shown type are. In a ceramic tube, consisting of a highly porous ceramic material for this purpose, for example 19 axial bores are introduced, which are arranged parallel to each other.

In the upper area of 2 the treatment stations of a printed circuit board treatment plant are partially shown. The circuit boards are successively performed in the treatment Rich tion R through the individual treatment stations. A typical example of such a method is ia in WO 93/17153 A1 described.

After this the pretreatment steps have already been carried out, the (not shown here) printed circuit boards in a palladium in colloidal Form-containing activation bath in the activation station A-Pd dipped. The liquid is this in a dip tank contain.

Subsequently, the circuit boards by three successive rinsing stations S ₁ , S ₂ and S _3rd transported. There, the adhering to the surfaces of the circuit boards activation liquid is rinsed successively. For this purpose, spray nozzles are provided in the individual rinsing stations S ₁ , S ₂ and S ₃ . The rinsing stations S ₁ , S ₂ and S ₃ are formed as upwardly open container, are arranged at the longitudinal side walls of nozzles. When sinking into and / or when lifting out the circuit boards from the stations S ₁ , S ₂ and S ₃ , rinsing liquid is sprayed onto the circuit board surfaces in order to rinse off the adhering activating liquid. The rinsing liquid is collected in the respective rinsing stations S ₁ , S ₂ and S ₃ at the bottom of a container. Fresh rinsing liquid is conducted at a mean flow rate of 200 l / h into the rinsing station S ₃ and at the same flow rate from there counter to the treatment direction R for the printed circuit boards in the previously arranged rinsing station S ₂ and from there into the rinsing station S ₁ . Each individual rinsing station S ₁ , S ₂ , S ₃ is also associated with a collecting container (not shown), in which the respective rinsing liquid is collected. From the collecting container of the rinsing station S ₁ , the collected rinsing liquid flows at a flow rate of 200 l / h for further processing.

After this the surfaces the circuit boards by rinsing freed of adhering activating liquid they are post-treated. Such treatment liquids are solutions, for example of sulfinic acids. At post-treatment station B, the printed circuit boards are treated in these in treatment containers contained solutions immersed.

Subsequently, adhering after-treatment solution is rinsed off again in the further rinsing stations S ₄ , S ₅ and S ₆ . Again, the rinsing liquid is sprayed from the arranged in the stations S ₄ , S ₅ and S ₆ nozzles to the circuit board surfaces. The collected rinsing liquid is passed into collection container (not shown) and from there again against the direction of treatment for the printed circuit boards R successively in the previously arranged flushing stations S ₅ and S _{4 passed} . From the rinsing station S ₄ , the rinsing liquid drains off for further wastewater treatment.

After that The printed circuit boards are immersed in an etching solution, which in a container in the etching station C-Pd is included. There is adsorbed on copper surfaces palladium removed from the activation by the copper surfaces easily etched become. Also in this case, the circuit boards are immersed in the etching solution.

Thereafter, adhering treatment liquid is rinsed off the circuit board surfaces again. For this purpose, the circuit boards are transported into the rinsing stations S ₇ , S ₈ and S ₉ . Etching solution adhering to the circuit board surfaces is removed by means of nozzles sprayed against the surfaces from nozzles. For this purpose, fresh rinsing liquid is passed into the rinsing station S ₉ at a flow rate of 200 l / h and the rinsing liquid obtained in this rinsing station is collected in collecting containers (not shown). The collected rinsing liquid is again directed counter to the treatment direction for the circuit boards R of the rinsing station S ₉ in the rinsing station S ₈ and from there into the rinsing station S ₇ . From the rinsing station S ₇ , the rinsing liquid enriched with palladium reaches a reprocessing arrangement at a flow rate of 200 l / h.

The provides the above-mentioned treatment method for the printed circuit boards only one possible Alternative dar. The circuit boards can also be in a so-called Horizontal plant to be treated. Here are the plates in horizontal transport direction and in horizontal or vertical Alignment guided by the individual stations. In the individual stations can the liquids via nozzles to the Be promoted surfaces.

The rinsing liquid originating from the rinsing station S ₄ contains practically no noble metal and can be supplied to the conventional wastewater treatment. By contrast, rinsing liquid originating from the rinsing stations S ₁ and S ₇ contains palladium and is therefore worked up in the manner according to the invention:
First, the individual rinse waters are in buffer tanks 11.1 respectively. 11.2 collected. From the buffer tanks 11.1 and 11.2 at a flow rate of 200 l / h effluent flushing liquid is then pumped 12.1 respectively. 12.2 into the pipes 13.1 respectively. 13.2 promoted and arrived in a common pipeline 13.3 , For pH adjustment, the combined rinsing liquids - if necessary - with a pH adjusting agent, in this case NaOH, mixed. For this purpose, the combined rinsing liquids NaOH solution from a reservoir 14 added. To control the dosage of NaOH solution is an (not shown) electrical control circuit. This includes a pH probe 15 , For example, a pH measuring electrode, for controlling a metering pump (not shown) for the NaOH solution. If the pH of the rinse liquid is near 7, the pH need not be set exactly to 7.

If an ionic or ionic palladium solution is used instead of a palladium colloid liquid, solutions of other suitable chemical substances are used instead of a pH adjuster Liquid flow metered to ensure that the palladium-containing solution is filterable.

The rinsing liquid, whose pH is now set to a value of about 7, is then by means of another pump 12.3 over a pipeline 13.4 in a collection container 16 directed.

In the collection container 16 are a lower level sensor 17.1 and an upper level sensor 17.2 intended. If the level exceeds the upper level sensor 17.2 , liquid gets out of the container 16 over the pipeline 13.5 to the pump 18 directed. Is the level of the collecting container 16 however, below the lower level sensor 17.1 , the rinsing liquid from the collecting container 16 not pumped out.

By means of the pump 18 the liquid is pressurized in the range of 1.5 to 3 bar via two membrane filter tubes connected in series 1 directed. The passing through the pipe walls permeate liquid is withdrawn for further wastewater treatment A. The remaining in the filter tube concentrate liquid is through the loop 13.6 circulated so that the liquid is continuously concentrated with respect to palladium. About the junction 13.7 Part of the concentrated rinsing liquid is constantly to the collection container 16 returned and from there again via the pump 18 to the membrane filters, so that palladium gradually accumulates in this liquid.

In the collection container 16 Palladium-containing sludge settles in a multi-phase separation zone which results from concentration. This sludge suspension can in another container 19 subtracted from.

Directly derived from the activation station A-Pd liquid can also be removed directly for processing and fed to the ultrafiltration. For this purpose, this liquid either manually via the path designated by reference M in a collecting container 20 transferred or small amounts of it by means of a pump 12.4 to the buffer tank 11.1 be directed. Manually removed and into the collection container 20 transferred liquid can then, for example via another pump 12.5 to the collection container 16 be encouraged.

The in the multi-phase separation unit within the container 16 contained sludge suspension is used for further separation of palladium to a filter press 21 directed. The filter press 21 is in 2 indicated by dashed lines. It contains filter material with a pore size of about 50 μm. The pressure in the press is about 4 bar. Excess liquid can either pass through the further pipeline 22 in the collection container 16 returned or the wastewater treatment A are supplied.

following Examples are given to illustrate the invention:

Example 1:

to execution of an experiment were printed circuit boards with a colloidal, acidic activator liquid treated, the 400 mg / l palladium as a colloid, a polymer as a protective colloid and sodium hypophosphite as a reducing agent. The middle one Particle diameter of the palladium colloid particles was about 4 nm.

The Circuit boards were after rinsing with a post-treatment solution, containing an organic sulfinic acid, treated, then again rinsed and finally treated in a 300 g / l sodium persulfate containing etching solution. The case of the copper surfaces removed amounts of palladium arrived in the etching solution and on the adhering to the circuit board surfaces etching solution in the following rinsing liquid.

The rinsing liquids obtained under the aforementioned conditions from the rinsing stations S ₁ to S ₃ and S ₇ to S ₉ (see 2 ) were conducted at a flow rate of 200 l / h in the described Regenerieranordnung. The fluids were separated at a filter membrane consisting of a ceramic (α-Al ₂ O ₃ as a carrier material with two applied thereto ultrafiltration layers of ZrO ₂ and TiO _2, wherein TiO ₂ having the finest pore size and a filtration with a pore exclusion size of approximately 20,000 Dalton effected the TiO ₂ layer was applied by a sol-gel method). The concentration of palladium in the rinsing liquids as well as the pH of these liquids are given in Table 1 (Experiments Nos. 1 and 2).

The pH values of the fluids originating from the rinsing stations S ₁ to S ₃ and S ₇ to S ₉ were not adjusted with pH adjusting agents.

at Ultrafiltration became the concentrate fluid at a flow rate of 2,800 l / h passed the ceramic membrane filter. There was a permeate flow rate from 40 to 45 l / h.

To The ultrafiltration was a permeate and a concentrate liquid receive. The palladium concentrations according to experiments Nos. 1 and 2 in the permeate and in the concentrate are also given in Table 1.

Example 2:

In Another attempt was a mixture of rinsing liquids from the colloidal activator fluid and the etching solution in volume ratio 1: 1 prepared (experiment no. 3). It became the same ceramic membrane filter as used in Example 1. The initial palladium concentration in the combined rinsing liquids as well as the pH of the mixture are given in Table 1. To adjust the pH of the combined rinsing liquids to 7 was a NaOH solution to the rinsing liquid added.

The after execution The permeate solution obtained by ultrafiltration had a palladium concentration of <0.5 mg / l. The The concentration of palladium in the concentrate was> 1 g / l (see table 1).

Example 3:

Also for one Further experiment # 4 was the same ceramic membrane filter as in Example 1 used. The according to example 2 obtained mixture of rinsing liquids became colloidal activator liquid in volume ratio of 1: 100 added. The palladium concentration in this liquid was 15.0 mg / l. The pH of this liquid was raised by NaOH solution 7 set. The palladium concentrations in the permeate and in the concentrate after execution of the ultrafiltration are shown in Table 1.

Example 4:

Also for a further experiment No. 5, the same ceramic membrane filter as in Example 1 was used. Instead of a colloidal activator solution, the solution of an ionic activator was used in this experiment. The activator contained an organic palladium complex (Neoganth Activator ^®, Atotech Deutschland GmbH, Germany), the palladium concentration was 250 mg / l in this solution.

The circuit boards activated with this solution were again treated in a rinsing cascade of three rinsing stations S ₁ , S ₂ and S ₃ , the rinse water flow direction being that of 2 corresponded. The palladium concentration in the coming from the rinsing station _S1 rinse water was about 1.5 mg / l. To adjust the ultrafiltrability of the rinse water, an aqueous solution of 467 g / l of sodium dimethyldithiocarbamate was added to the rinse water. The palladium concentrations in the permeate and in the concentrate determined as a result of the ultrafiltration of this solution are reproduced in Table 1 (Experiment No. 5).

Example 5:

Also for one Further experiment No. 6 was the same ceramic membrane filter as in Example 1 used. In this experiment, this was done according to example 4 received rinse water in a volume ratio of 100: 1 with the activator bath solution mixed. The mixture was an aqueous solution of 10 g / l sodium sulfide added. The initial one Palladium concentration was 8.0 mg / l. The palladium concentrations in the filtrate and in the concentrate after ultrafiltration are shown in Table 1 indicated.

The The experiments described above gave concentrate liquids, which had a considerable amount of sludge. After discontinuation of Sludge, the concentrate was fed to a filter press. The Palladium concentration in the enriched concentrate was 2 to 5 g / l. During the compression, a filter cake with a palladium concentration from 2 to 15% by weight.

Example 6:

For one Further experiment # 7 was the same ceramic membrane filter as in Example 1 used. The according to example 2 obtained mixture of rinsing liquids became a mixture according to example 5 in volume ratio 2: 1 added.

The Palladium concentration in this liquid was 4.2 mg / l. Of the pH was determined by NaOH solution set to 7. Furthermore, an aqueous solution of 467 g / l Natriumdimethyldithiocarbamat to the liquid added. The palladium concentrations in the permeate and in the concentrate after execution of the ultrafiltration were carried out as shown in Table 1.

It is understood that the examples and embodiments shown here are merely illustrative and that various modifications and changes and combinations thereof described in this application Characteristics for being near a professional and within the spirit and scope The present invention and the appended claims are. All publications cited here, Patents and patent applications are hereby incorporated by reference added.

1

Ceramic membrane filter

2

Ceramic filter layer

3

highly porous ceramic carrier tube

4

Flow direction

10

PCB treatment plant

11.1,11.2

buffer tanks

12.1-12.5

pump

13.1-13.7

piping

14

reservoir

15

pH probe

16

receptacle

17.1

lower level sensor

17.2

upper level sensor

18

pump

19

container

20

receptacle

21

filter Press

22

pipeline

A-Pd

activation station

B

post-treatment station

S ₁ -S ₉

rinsing stations

C-Pd

etching station

M

manual withdrawal

A

wastewater treatment

R

treatment direction for the PCBs

Claims (12)

Process for galvanic treatment of workpieces with a palladium-containing liquid, comprising the process steps: Contacting the workpieces with the liquid, then mix the liquid with chemical substances selected from the group comprising pH adjusting agents, reducing agents, sulfur compounds, selenium compounds and tellurium compounds, and then filtering the liquid through at least one ceramic membrane filter to remove the palladium from the liquid too separating, wherein the ceramic membrane filter an exclusion pore size of more than 10,000 daltons and where the chemical substances are selected that palladium particles are formed whose particle size is so large that the particles are the pores of the at least one ceramic membrane filter can not happen. The method of claim 1, wherein the at least one Ceramic membrane filter has an exclusion pore size in the range of about 15,000 Dalton to about 25,000 daltons. The method of claim 2, wherein the at least one Ceramic membrane filter has an exclusion pore size of about 20,000 daltons. Method according to one of the preceding claims, wherein the at least one ceramic membrane filter of an alumina / titania / zirconia ceramic material is made. Method according to one of the preceding claims, wherein the workpieces are suitable for the production of electrical circuit carriers. Method according to one of the preceding claims, wherein Palladium is present in ionic and / or ionic form and wherein the liquid with the chemical substances selected from the group comprising Reducing agents, sulfur compounds, selenium compounds and tellurium compounds, is mixed. The method of claim 6, wherein the chemical substances selected are from the group comprising borohydrides, amine boranes, hypophosphites, inorganic sulfides and organic thio compounds. The method of claim 7, wherein palladium in colloidal Form is present and wherein the chemical substances pH adjusting agent are with the liquid be mixed in a way that the pH of the liquid ranging from 3 to 12. The method of any of claims 6-8, comprising the following Steps: a. the workpieces are covered with a palladium containing treatment liquid brought in contact, b. then the on the surfaces of the workpieces adhering treatment liquid with a rinsing liquid removed, and c. the treatment liquid and / or the rinsing liquid be through the at least one ceramic membrane filter to the Filtration passed, with the liquid containing the at least passed through a ceramic membrane filter, a permeate liquid is, and the liquid, that did not pass the at least one ceramic membrane filter, a concentrate liquid is. The method of claim 9, wherein the treatment liquid and / or the rinsing liquid mixed with the chemical substances before passing through the at least one ceramic membrane filter are passed. Method according to one of claims 9 and 10, wherein a rinsing liquid, the maximum 5% by volume of the treatment liquid contains is passed through the at least one ceramic membrane filter. The method of claim 11, wherein the workpieces per Time unit with a predetermined amount of fresh rinse liquid be contacted and where the amount of per unit time formed permeate about the same size like the amount of rinsing liquid, which is brought into contact with the workpieces per unit of time.