MXPA04002772A

MXPA04002772A - Precious metal recovery.

Info

Publication number: MXPA04002772A
Application number: MXPA04002772A
Authority: MX
Inventors: Hahndorf Ina
Original assignee: Atotech Deutschland Gmbh
Priority date: 2001-09-26
Filing date: 2002-08-15
Publication date: 2004-06-29
Also published as: US20040237717A1; CA2460015A1; WO2003029518A2; DE60223934D1; BR0212823A; ES2297045T3; EP1430163A2; MY147747A; TWI293999B; EP1430163B1; DE60223934T2; JP2005504178A; WO2003029518A3; KR20040043168A; CN1633521A; DE10148632C1; ATE380264T1; AU2002333428A1

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

RECOVERY OF PRECIOUS METALS The invention relates to a method and a device for the veneering of workpieces with a fluid containing precious metals. The invention is especially applicable in processes for producing electric circuit carriers. For electroplating workpieces, the surfaces thereof must be treated, first in such a way that they become electrically conductive if the surfaces of the workpieces are not conductive. For this purpose, the workpieces are immersed in a solution containing ionic, ionogenic or colloidal palladium. More particularly, the ionic palladium may be present in the form of a salt, such as for example palladium chloride, which is generally dissolved in a hydrochloric acid solution. Ilogenic palladium is present as a complex, for example an aminopyridine complex. The colloidal palladium may contain various protective colloids, for example, a protective colloid formed from tin (II) chloride or consisting of an organic polymer. The palladium cores that adsorb therein on the surfaces of the workpieces serve, for example, as activators to initiate a metal deposit without electrodes which causes an electrically conductive layer to form on the surfaces so that the surfaces then They are ready to be coated with any metal. This method is used to produce printed circuit boards, and other circuit carriers, as well as metal-coated parts in the sanitary, automotive and furniture industry, by way of example, and more specifically, for plastic parts coated with chrome The palladium-containing solution can also be used to form an electrically conductive layer. In this direct electroplating method, additional metal is deposited electrolytically after the palladium treatment without a metal layer being previously formed with a metal coating method without electrodes. In the treatment of workpieces that have electrically non-conductive surfaces, part of the palladium-containing solution still adheres to the workpieces when previously submerged workpieces emerge from the solution. The adherent solution is usually rinsed with water. With the known activation methods using colloidal palladium, for example, a solution containing usually 50-400 mg / 1 of palladium is used. In the treatment of plastic parts with a geometric surface of one square meter, typically 5-10 mg of palladium are adsorbed. This amount is necessary to activate the surface of the plastic. When the work pieces to be treated leave the corresponding processing station, approximately 0.2 1 of activation solution per square meter is carried from the bath and is still left on the surfaces. Therefore, about 10 to 50 mg of palladium is lost in the bath because the tackifier solution is drawn out of the processing bath, then rinsed and transferred to the waste water treatment. In the direct electroplating of electrically nonconductive surfaces without the electrode, solutions containing palladium of metallic coating are also used. In this case, a higher concentration of palladium is needed, for example 400 mg / 1 in the solution. By carrying out the known methods of direct metal coating, the palladium entrained from the processing solution accounts for approximately 50 mg / m2.When taking appropriate measures such as pre-adsorption of polyelectrolyte compounds to the non-conductive surfaces, the adsorption of the palladium particles from a relatively low value to about 50 mg / m2 on the surface of the workpieces can be increased, although approximately 60-70% of the palladium used in the solution is lost when being dragged, only 40-30% can actually be used for the metallic coating of the surfaces of the workpieces. For example, the recovery of palladium from the processing solutions has been known. For example, in U.S. Patent No. 4,078,918, it describes a recovery process for recovering, for example, palladium from various materials containing dissolved or undissolved palladium. The materials are first treated with an oxidizing agent to destroy possible organic components and then treated with ammonium hydroxide to form amine complexes. The palladium complexes obtained in this way are then reduced with ascorbic acid so that the palladium is deposited from the processing solution as a metal and can be filtered. Furthermore, in "Reclamation of palladium from colloidal seeder solutions" in Chemical Abstracts, 1990: 462908 HCAPLUS a method is described for recovering palladium from solutions of colloidal Pd / SnCl2 as "a pre-treatment before the electroless metal coating in which gasifies the solution with air for 24 hours, so that the palladium is floated.The deposit is separated, dried and further processed.In "Recovery of palladium and tin dichloride from waste solutions of colloidal palladium in tin dichloride" in Chemical Abstracts, 1985: 580341 HCAPLUS describes a method for precipitating palladium by the addition of metallic tin at 90 ° C. U.S. Patent No. 4,435,258 describes another method for recovering palladium from depleted baths that are used to activate surfaces electrically non-conductive for the subsequent metal coating process without electrodes, the activation solutions are re-processed by making The colloidal palladium is oxidized in the solution by adding an oxidizing agent such as, for example, hydrogen peroxide, by subsequently heating the solution to destroy the residual hydrogen peroxide and subsequently by electrolytically depositing the palladium of these solutions at a cathode. In "Recovery of the colloxdal palladium content of exhausted activ-ating solutions used for the current-free metal coating of resin surfaces" in Chemical Abstracts, 1976: 481575 HCAPLUS finally a method for obtaining palladium of Pd / SnCl2 is described in which Palladium is precipitated by the addition of concentrated nitric acid, and filtered. DE 100 24 239 Cl describes a method for electroplating workpieces with a palladium colloidal solution by contacting the workpieces with the colloidal solution according to which palladium is recovered after the colloidal solution was used, by separating the palladium colloidal particles from the colloidal solution by means of a membrane filter. For example, materials made from ceramic products can be used for filtration. The pore exclusion size of the membranes accounts for 200 to 10,000 Daltons. It is stated therein that the palladium particles pass through the membrane filter when the pore exclusion size used is in excess of 10,000 Daltons. The prior art methods for electroplating workpieces with a colloidal palladium solution are complicated and expensive. The basic problem facing the present invention is to avoid the disadvantages of known methods and to find a method for coating workpieces with a fluid containing at least one precious metal that can be carried out at low cost. Small amounts of additional chemicals should only be necessary to carry out the method. In addition, the method must include a small expenditure of energy and time and must require more specifically little maintenance. This problem is overcome by the method according to claim 1 and by the device according to claim 15. Preferred embodiments of the invention are indicated in the dependent claims.

The method according to the invention serves to platen workpieces with a fluid, this fluid contains at least one precious metal, the method comprises contacting the workpieces with the fluid. For the purpose of recovering the precious metal from the fluid, the fluid is filtered after the plating of the work pieces through at least one ceramic membrane filter to separate the precious metal from the fluid, the ceramic membrane filter having a size pore exclusion in excess of 10,000 Daltones. Due to filtration, the precious metal is separated from the fluid. By plating, it means any treatment with fluids that is directed to alter the surface of the work pieces, the fluid that has to contain precious metals. Not included in it are the methods of coating workpieces with polymeric coatings, more specifically methods with varnishing. The workpieces to be veneered include metal workpieces, non-metallic workpieces and workpieces consisting of both metallic and non-metallic materials. Workpieces can have all conceivable shapes and that are proposed for all conceivable uses. Preferred parts are semi-finished products for producing circuit carriers, more specifically for producing printed circuit boards and hybrid circuit carriers such as multi-circuit modules, by way of example. The precious metals that can be separated from the corresponding fluids are all the elements of Group I and VIII of the Periodic Table of the Elements, that is, more specifically Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag and Au. The invention relates preferably to a method for treating workpieces when plating with a fluid containing palladium. More specifically, the fluid can be a solution. This is more specifically the case when the precious metal is present in ionic or ionogenic form. By ionic form of the precious metal, it is meant more specifically salts of the precious metal dissolved in water or in another solvent that promotes the dissociation of the salts. By ionogenic form of the precious metal, it is meant complexes of precious metals, more specifically complexes of the precious metal ions with complex organic ligands. The complexes may be unchanged or present in the ion form. The fluid may be present in the form of a colloid, more specifically a colloid of the elemental precious metal. The fluid containing the precious metal can be either a processing fluid for treating the work pieces or a rinsing fluid. By "processing fluid" is meant a fluid which serves to alter the surface properties of the workpieces, for example, a coating fluid, which includes an activating fluid, a cleaning fluid, an acid etching fluid or the like. . In contrast, a rinsing fluid only serves, after treatment of a workpiece with the processing fluid, to rinse the processing fluid that is still adhered to the surface of the workpiece. After the use of the fluid for coating the workpieces, the precious metal is filtered on at least one ceramic membrane filter. This means that the fluid is used for the first time for the plating and is only filtered afterwards in the membrane filter for the purpose of recovering the precious metal it contains. The fluid for example can be contacted with a work piece by spraying, injecting, flooding or cleaning, the fluid that submerges the collected workpiece and the collected fluid that is driven by the membrane filter immediately thereafter. The collected fluid can also be retained first in a tank where it is distributed back to the work piece. In this case, the fluid can either be conducted to the membrane filter after it has been collected for a predetermined period of time (intermittent method), or part of the fluid can be continually derived from the reservoir and transferred to the membrane filter (continuous method). To achieve a stationary fill condition in the tank in this case, new processing fluid is permanently introduced into the tank in an amount per unit of time which is equal to the amount of fluid permeating the membrane filter per unit of time. The workpieces can also be brought into contact with the processing fluid contained in the treatment tank by immersing them therein. In this case, the processing fluid after use is either conducted to the membrane filter after it has been collected for a predetermined period of time (intermittent method), or part of the fluid in the tank can be continuously derived from The treatment vessel is transferred to the membrane filter (continuous method). The method of the invention makes it possible to achieve, in a simple and low-cost manner of chemicals, energy and time, as well as little maintenance, a long-sought separation of the precious metal from depleted processing solutions under continuous operation. More specifically, it allows regenerating the depleted processing solutions after the fraction containing the palladium has been separated so that the entire palladium can be re-circulated into the process. With respect to the method described in Chemical Abstracts, 1990: 462908 HCAPLUS for recovering palladium from colloidal Pd / SnCl2, the present method has the advantage that the fractions are completely separated whereas with the precipitation method described in Chemical Abstracts a part not oxidized is oxidized. negligible of palladium to form the bivalent soluble stage thereof so that it can not be completely separated from the solution by filtration. Therefore, this part of the palladium can not be recovered and will be lost. Another advantage of the method of the invention with respect to the method described in Chemical -Abstracts, 1985: 580341 HCAPLUS is that there is no need for a considerable expenditure of additional chemical products such as metallic tin, neither of energy nor of time, as is required for the known method for the purpose of heating the colloidal solution. The method according to the present invention also has substantial advantages over the method described in U.S. Patent No. 4,435,258. specifically because palladium can be recovered almost completely from the solutions, whereas, by the method according to U.S. Patent No. 4,435,258, only extremely low actual efficiency can be achieved, especially when the concentration is low of palladium, which occurs after a long period of electrolysis .. Therefore, either it is very complicated or it is not possible to completely recover completely the palladium with this method of the prior art. In contrast to the method described in Chemical Abstracts, 1976: 481575 HCAPLUS, the method and device according to the present invention are more especially suitable for continuous operation. In addition, the method presented in this publication necessarily requires additional chemical products. Surprisingly, and as contrasted with the properties of membrane filters that have a pore exclusion size clearly in excess of 10,000 Daltons as indicated in DE 100 24 239 Cl and according to which the palladium particles of Colloidal palladium solutions permeate the filter, the separation properties of ceramic filters having a pore exclusion size of for example 20,000 Daltones proved to be excellent with respect to colloidal palladium. In this regard, reference is made to tests No. 1 and 2 in Example 1. The method and device according to the present invention has the following advantages with respect to known methods and devices: a. You can recover precious metal, more specifically palladium, of ionic, ionogenic and colloidal solutions with a device. It is not necessary to use several coupled devices. As a result of the same, the solutions can be mixed and collected before they are regenerated. The same also applies to processing and rinsing fluids: processing fluids with a high concentration of precious metal can be mixed with rinsing fluids containing precious metal in very low concentration and then processed together. b. Ceramic membrane filters that are mostly resistant to chemicals and to the effects of temperature, can be used since the separation of the precious metal with larger gold from the ceramic membrane filters is also successful. The maintenance is little as a result of the same since the filters do not need a very frequent cleaning. The ceramic membrane filters also have an extended life. In addition, the precious metal is not adsorbed to the membrane material. c. The fluid to be treated can be re-processed with a very simple method. For example, it is not necessary to work in a protective atmosphere to prevent the colloidal particles from dissolving in the fluid.

The palladium-based colloidal activators comprise palladium particles that are surrounded by a protective coating (protective colloid). The tests using high resolution transmission electron microscopy (HTEM) and atomic force microscopy (AFM) showed that the palladium particles have a diameter of at least 2.5 nm. The average particle diameter accounts for approximately 4 nm, which corresponds to the Gaussian distribution of particles. In the test a rinse fluid that was obtained after the treatment of the workpieces with the colloidal activator, a broad particle size distribution was determined which showed particles with a maximum size of about 18 nm as well as small particles (of 2 at 18 nm). In practical use, the colloidal solutions are acidic, often with a high concentration of hydrochloric acid, and contain chloride ions as well as possibly tin in the oxidation stages (II) and (IV) or organic polymeric stabilizers such as gelatin or polyvinylpyrrolidone and reducing agents. Except for polymers, which are used in small amounts, all other substances contained in the same are ionic. It is presumed that these ionic constituents are much smaller than the palladium particles.

Surprisingly, palladium particles can be removed very selectively and completely from these colloidal solutions by means of appropriate membrane filters comprising different porosities, although, in the case of colloidal solutions containing tin, tin, which it is simultaneously present, is contained in a high concentration (usually more than 70 times the concentration of palladium) and although tin compounds are known to form colloidal solutions they are difficult to filter. For ultrafiltration, various types of membranes made of various materials have to be tested. The . Tests showed that with respect to the selection of the membrane filter it is more specific that it is sufficiently stable to the fluid containing the precious metal and containing 15 weight percent of eg hydrochloric acid. To separate the palladium colloidal particles, ceramic membrane filters having an exclusion pore size of about 15,000 Daltones to about 25,000 Daltones can be used, more specifically an exclusion pore size of about 17,500 Daltones to about 22,500 Daltones. and more preferably about 20,000 Daltones. A preferred ceramic membrane filter is made of a ceramic material containing aluminum oxide, more specifically -Al203 / titanium dioxide and possibly zirconium dioxide. In principle, other filter materials can also be used. As a rule, the filter material is deposited in a highly porous support body which provides the filter with the required mechanical stability. This support body may consist of -? 1203, or SIC (silicon carbide), by way of example. The filter can be configured in the form of a disk or as a tube. In the first case, a flow is directed in the disk, approximately normal to the surface thereof, this flow that deviates in the radial direction. A pressure difference builds up between the two surfaces of the disk so that the permeate can diffuse into the disk. If the filter has the shape of a tube, the fluid is transported through the tube in the axial direction, a pressure difference that accumulates between the interior space and the outer space of the tube. As a result of the same, the permeate can diffuse into the wall of the tube, for example, from the inner volume of the tube to the outer space of the tube. This second method is called dynamic filtration. In this case, the precious metals are retained within the interior space of the tube, while the fluid, which has been mostly released from the precious metal, permeates through the wall of the tube from the inner volume of the tube to the outer space of the tube. Some fluids can be filtered directly without any additional pretreatment. In this case, very good results are obtained with the ceramic membrane filters. In some cases, the fluids that are to be re-processed are chemically pre-treated first. After they have been used for the plating and before they are filtered through the membrane filter, the fluid is mixed for this purpose with chemicals that are suitable for altering the precious metal in such a way that it is almost completely retained. during the filtration. It is presumed that, by adding these chemical substances, the particle size of the precious metal is altered in such a way that the particles containing the precious metal can not pass through the pores of the membrane filter. For this purpose, the average particle size should be sufficiently adjusted to a value in excess of 10 nm when the particle size is adjusted to. the Gaussian distribution. In this case, a membrane filter with an exclusion pore size in excess of 10,000 Dalton will retain almost the entire amount of precious metal in the concentrate. Therefore, larger particles can be adjusted by adding these chemicals when membrane filters with a larger exclusion pore size are used. If the palladium is present in the solution in ionic and / or ionogenic form, the fluid can be mixed with chemicals selected from the group comprising reducing agents, sulfur compounds, selenium compounds and tellurium compounds. Precursor chemicals are most preferably selected from the group consisting of boron hydrides, amine boranes, hypophosphites, inorganic sulphides and organic thio compounds, more specifically the alkali metal salts of dimethyl dithiocarbamate, disulfides. , of boron hydrides such as for example tetrahydroboranarate, and of hypophosphites. The organic-organic compounds considered are more specifically organic compounds in which the sulfur is bonded to one or two carbon atoms to form an individual or double bond with it. same, ie, thiols, sulfides, disulfides and polysulfides, for example thioamides and thioaldehydes. If palladium is present in the fluid in the colloidal form, pH adjusting agents are used as chemicals. The fluid is mixed with the pH adjusting agents in such a way that the pH of the solution varies from 3 to 12. In both cases, a solution is obtained which is very suitable for separating the precious metal, in this case to separate palladium. The following advantages derive from the improvement of the present invention. to. the pre-treatment is very simple. It is sufficient to mix the fluids containing the precious metal with the required substances or with the pH adjusting agent respectively. b. it is very low the expense of additional chemical products. To process 200 liters of rinse water from the treatment with an aqueous solution of an organic palladium complex (7 mg / 1 Pd), only 7.5 ml of a solution containing 467 g / 1 of sodium dimethyl-dithiocarbamate is needed. . If rinsing waters originating from the treatment are to be processed with a palladium colloid (organic protective colloid, 25 mg / 1 Pd), only 0.5 1 of an aqueous solution of 432 g / 1 of NaOH will suffice. It can be inferred from the observations and tests leading to the present invention that it is possible to recover precious metals from rinsing fluids and / or processing fluids by means of membrane filters. For this purpose. to. the workpieces are brought into contact with a processing fluid containing palladium, b. then, the processing fluid that is still adhered to the surfaces of the workpiece is removed with rinsing fluid, and c. the processing fluid and / or the rinsing fluid are passed (preferably under pressure) through at least one ceramic membrane filter for the filtration thereof, the fluid which is passed through at least one filter of membrane which is a permeate fluid and the fluid that has not passed through at least one membrane filter is a concentrated fluid. After treatment with a fluid containing palladium, the workpieces that are preferably made of an electrically non-conductive material are rinsed in a suitable device with a rinsing fluid when immersed therein, by flood or preferably by spraying the rinsing fluid from the work pieces in order to keep the volume of the rinsing solution as low as possible. The rinsing fluid is then led through the ceramic membrane filter by means of a pressure pump, the filter that retains the palladium particles and allows the rinsing water to permeate. Then the permeate can be transferred to the waste water treatment. Before being conducted through the membrane filter, the processing fluid and / or rinsing fluid can be mixed with the chemicals such as for example reducing agents, sulfur compounds, selenium compounds, tellurium compounds and the pH adjusting agents. In a particularly preferred embodiment of the invention, only the rinsing fluid, or a rinsing fluid preferably containing up to 5 volume percent of the processing fluid, is conducted through the membrane filter (preferably under pressure ). The workpieces are brought into contact with fresh rinse solution, a predetermined amount of fresh rinse solution per unit of time being permanently available. The amount of the permeate fluid, formed per unit of time, can be adjusted more specifically to be approximately equal to the amount of the rinsing fluid which is brought into contact with the work pieces per unit of time. As a result of the same, a stationary condition is achieved in the processing plant; Since the amount of fresh rinse fluid distributed to the work pieces is exactly the same as the amount of permeate fluid drained from the plant, the result obtained is a constant flow of substances. Of course, this only applies if the amount of additional chemical substances is imperceptible and if there are no additional variables that influence, in the process. In practice, by evaporating the rinsing fluid most of it can be carried out. The fluid retained, which is present. as a concentrate in the form of a homogeneous dispersion of metal or a metal compound, for example, in the form of a PdS dispersion, it can be recycled. The palladium retained can for example be dissolved, converted to palladium chloride and used to synthesize a new processing fluid containing palladium or for any other application. The concentrated solution containing palladium can also be concentrated to near dryness in a filter press. For this purpose, the concentrated fluid coming from the membrane filter is directed to a container in which the thick suspension containing palladium that has formed during the concentration is deposited, the slurry being routed to the filter press. The filter cake containing palladium obtained by means of the filter press can be used as a base substance to produce pure palladium, and palladium compounds. The device according to the invention for plating workpieces with a fluid containing at least one precious metal is typically provided with a means for contacting the workpieces with the fluid as well as with a retention means for the workpiece parts. job . The means for contacting the fluid with the workpieces are for example nozzles by means of which the processing or rinsing fluid is sprayed, injected, flooded or discharged onto the surfaces of the workpieces. This arrangement is adjusted, for example, when the fluid will reach the surface at a high flow rate or when the amount of fluid needed will be minimized. In another embodiment of the invention, the contacting means are treatment vessels in which the processing fluid is deposited and in which the work pieces are submerged. The retensioning means for the workpieces can also be incorporated in many different forms: for example, the workpieces can be retained in a conventional manner by means of staples, clamps, pliers or screws. In addition, the workpieces can also simply be held, transported and driven in a horizontal position on rollers, wheels or cylinders or be clamped therefrom. In addition to the mentioned features, the device also comprises an installation for separating the precious metal from the fluid. This installation comprises at least one ceramic membrane having an exclusion pore size of more than 10,000 Daltons. In addition, the installation comprises at least one pump for distributing the fluid to at least one membrane and the fluid conduits for conducting the fluid from the medium to contact the workpieces with the fluid to at least one ceramic membrane. By a pump, it is also meant any pump that is not operated by motor or simply the distribution of the fluid by gravity. According to the explanations given hereinabove, the installation for separating the precious metals from the fluid is further provided with a mixing facility. In the mixing plant, the fluid that comes from the medium of the contacting of the work pieces with the fluid can be mixed with chemical substances. For this purpose, any conventional mixing plant known in the art of chemical reactions can be used, such as, for example, stirring facilities and mixing zones in flow reactors. further, the installation for separating the precious metals from the fluid can also be provided with a multi-phase separation unit in which the slurry can be deposited, which occurs during the separation of the fluid and which comes from the installation to separate the metal precious fluid. A multi-phase separation unit of this type is formed by a settling tank, for example, in which no convection of fluids is taking place. This thick slurry can then be directed to a filter press in order to purify for the most part and to dry the slurry, which contains mainly precious metal. The invention will be better understood in reading the description of the Figures. More specifically, Figure 1 is a schematic perspective view of a ceramic membrane filter; Figure 2 is a schematic representation of a device for plating workpieces according to the invention. Figure 1 illustrates a ceramic membrane filter in the form of a tube 1. The tube is made of a highly porous ceramic material that serves as support 3, and which is, in the present case, aluminum oxide. The support 3 is provided, on its inner side, with another ceramic layer of an oxide that serves as a membrane filter layer 2. This membrane filter layer 2 consists in turn of two layers (not shown specifically), that is, a first microfiltration layer made of -Al203, and a second layer of elaborated ultrafiltration of Zr02 and Ti02, Ti02. which has a finer pore size so that filtration with an exclusion pore size of eg 20,000 Daltons is also possible. The membrane filter layer 2 has an exclusion pore size of approximately 20,000 Daltons. Accordingly, the average pore size accounts for approximately 20 nm. The tube has an inner diameter of approximately 6 mm. The tube is approximately 1,000 mm long. The flow passes through it under pressure in the flow direction referred to by the reference number 4. The pressure difference between the inlet and outlet of the tube varies from 1.5 to 3 bar. In order to collect the permeate that passes through the inner wall of the tube, the ceramic tube is placed concentrically inside another tube. Figure 2 comprises two of the filter tubes 1 shown in Figure 1, in the lower part of the Figure, the filter tubes 1 which are part of the ceramic tubes with several holes of the type shown in Figure 1. For this purpose, for example 19 axial holes are drilled in a ceramic tube consisting of a highly porous ceramic material, the axial holes being parallel. In the upper part of Figure 2, the processing stations of a processing plant for printed circuit boards are partially shown. The printed circuit boards are transported successively through the different processing stations in the processing direction R. It is described, inter alia, in WO 93/17153 to a typical example of this method. After the pre-treatment steps have already been carried out, the printed circuit boards (not shown here) are dipped in the activation station A-Pd, in an activation bath containing palladium in the form colloidal For this purpose, the fluid is contained in an immersion bath tank. Then, the printed circuit boards are transported through three successive stations S1 (S2 and S3 rinsing.) Here, the activation fluid that adheres to the surfaces of the printed circuit boards is rinsed in succession. Si, S2 and S3 rinse, are provided with spray nozzles to serve for this purpose, the rinse stations Si, S2 and S3í are configured as open containers that are provided with nozzles arranged in the walls of the long sides of the same In order to rinse the adherent activation fluid, the rinse fluid is sprayed onto the surfaces of the printed circuit boards as the printed circuit boards are lowered into and / or lifted from the Si, S2 and S3 stations. rinse is collected at the bottom of the container in the respective rinse station Si, S2 and S3 Fresh rinse fluid is distributed to the rinse station S3 at a rate of the average flow rate of 200 1 / h, from here is conducted in an opposite direction to the processing R address of the printed circuit boards to the rinse station S2 arranged upstream thereof from where it is placed in the station rinse rate Yes, the flow rate remains the same. Each rinsing station Si, S2 and S3 is also assigned to a collection tank (not shown) in which the respective rinsing fluid is collected. The collected rinse fluid is drained at a flow rate of 200 1 / h. from the collection tank of the rinse station Si to the additional processing. After the surfaces of the printed circuit boards of the adherent activation fluid have been released by rinsing, undergo post-treatment. These processing fluids are, for example, solutions of sulfinic acids. In the after-treatment station B, the printed circuit boards are submerged for treatment in these solutions which are contained in the treatment vessels. Then, the adherent post-treatment solution is rinsed again in the additional rinse stations S4, S5 and S6. Again, the rinsing fluid is sprayed from arranged nozzles at stations S4, Ss, and Ss on the surfaces of the printed circuit boards. The collected rinsing fluid is directed to the collection tanks (not shown) from where it is driven successively back, in a direction opposite to the processing direction of the printed circuit boards R, to the rinse stations S5 and S which they are arranged upstream of it. The rinsing fluid is drained from the S station to the subsequent wastewater treatment. The printed circuit boards are then immersed in an acid etching solution contained in a container at the C-Pd acid etching station. Here, the palladium adsorbed on the copper surfaces of the activation is removed by acid etching the copper surfaces. In this case too, the printed circuit boards are immersed in the etching solution. After this, the adherent processing fluid is again rinsed from the surfaces of the printed circuit boards. For this purpose, the printed circuit boards are transported to the 'rinse stations S7, S8 and S9. The etching solution adheres to the surface of the printed circuit boards, is removed by means of rinsing fluid that is sprayed from the nozzles on the surfaces. For this purpose, fresh rinse fluid is conducted to the S3 rinse station at a flow rate of 200. 1 / h and the rinse fluid collected in this rinse station is collected in the collection tanks (not shown) . Again, the collected rinse fluid is conducted in a direction opposite to the processing direction of the printed circuit boards R, from the rinse station S9 to the rinse station S8 and thence to the rinse station S7. From the rinse station S7, the rinse fluid enriched with palladium is conducted to a regeneration array at a flow rate of 200 1 / h. The aforementioned manner of treatment of printed circuit boards is a possible alternative. Printed circuit boards can also be processed in a horizontal floor call. The cards are thus guided through the various stations in a horizontal transport direction and in a horizontal or vertical orientation. In the various stations, the fluids can be distributed to the surfaces by nozzles. The rinse fluid originating from the S4 rinse station contains virtually no precious metal and can be distributed to the conventional waste water processing system. In contrast, the rinsing fluid originating from the Si and S7 rinse stations contains palladium and is regenerated in the inventive manner: First, the various rinse waters are collected in storage tanks 11.1 and 11.2, respectively. The flushing fluid drained from storage tanks 11.1 and 11.2 at a flow rate of 200 1 / hr is then conducted to ducts 13.1 and 13.2, respectively, by means of pumps 12.1 and 12.2, respectively, and distributed to a common conduit 13.3. To use the pH, the combined rinsing fluids are mixed, if necessary, with a pH adjusting agent, in the present case with NaOH. For this purpose, the NaOH solution is added from a reservoir 14 to the combined rinse fluids. An electrical control circuit (not shown) serves to control the dose of the NaOH solution. The control circuit comprises a pH probe 15, a pH measuring electrode, for example, for controlling a dosing pump (not shown) for the NaOH solution. In the case where the pH of the rinse solution is almost 7, the pH does not need to be adjusted to the precise value of 7. If an ionic or palladium ionogenic solution is used instead of a palladium colloidal fluid, They add solutions of other chemicals appropriate to the flow of the fluid instead of a pH adjusting agent to ensure that the fluid containing palladium is filterable.

The rinse fluid, the pH of which is now adjusted to a value of 7, is then directed by means of another pump 12.3 through a conduit 13.4 to a collection tank 16. A sensor is provided in the collection tank 16 lower 17.1 fill level and a higher level 17.2 fill level sensor. If the fluid level is higher than the upper fill level sensor 17.2, the fluid is directed through the conduit 13.5 from the container 16 to the pump 18. If in contrast, the fill level of the collection tank 16 is by below the lower level 17.1 level sensor, the rinsing fluid is not pumped-out of the collection tank 16. By means of the pump 18, the fluid is conducted, under a pressure varying from 15 to 3 bar, through two membrane filter tubes 1 connected in series. The permeate fluid that diffuses through the walls of the tube is drained to the additional treatment A of waste water. The concentrated fluid remaining in the filter tube is recirculated via closed circular conduit 13.6 so that the fluid is permanently and increasingly concentrated relative to the palladium. Via branch 13.7, part of the concentrated rinse fluid is circulated permanently back to the collection tank 16 from where it is directed to the membrane filters by means of the pump 18 so that the palladium gradually enriches the fluid. In the collection tank 16, the thick suspension containing palladium, resulting from the concentration, is deposited in a multi-phase separation zone. This thick slurry can be drained to another container 19. The fluid coming directly from the activation station A-Pd can also be discharged directly for regeneration and directed towards ultrafiltration. For this purpose, this fluid can either be transferred by hand to a collection tank 20 using the route referred to by the reference number M or small amounts thereof can be conducted to the storage tank 11.1 by means of a pump 12.4. The fluid that has been removed and transferred by hand to the collection tank 20 can then be distributed to the collection tank 16 by means of, for example, another pump 12.5. The slurry contained within the container 16 in the multi-phase separation unit is directed to a filter press 21 for further separation of palladium. The filter press 21 is shown in dashed lines in Figure 2. It contains filter material having a pore size of approximately 50 μp ?. The pressure in the press accounts for approximately 4 bar. The excess fluid can be recirculated either back to the collection tank 16 via the additional conduit 22 or distributed to waste water treatment A. The following examples will serve to explain the invention.

Example 1: To conduct a test, printed circuit boards were treated with an activating colloidal acid fluid that contained 400 m / 1 of colloidal palladium, a protective colloid in the form of a polymer and a reducing agent in the form of hypophosphite of sodium. The average particle diameter of the palladium colloidal particles was approximately 4 nm. After rinsing, the printed circuit boards were treated with a post-treatment solution containing organic sulfinic acid, then rinsed again and finally treated in an etching solution containing 30 g / 1 of sodium persulfate. The quantities of palladium thus removed from the copper surfaces were distributed to the acid etching solution and via the acid etching solution that adheres to the surface of the printed circuit boards, to the subsequent rinsing fluid. The rinse fluids obtained in the rinse stations Si to S3 and S7 to S9 (see Figure 2) under the conditions mentioned above were distributed to the regeneration arrangement described at a flow rate of 200 1 / h, respectively. The fluids were separated on a filter membrane made of ceramic material (a-Al203, as a support material with two ultrafiltration layers of Zr02 and Ti02, applied thereon, Ti02 which is provided with the finest pore size). and which performs a filtration with a pore exclusion size of approximately 20,000 Daltons, the Ti02 layer was applied by colloidal solution method). The concentration of palladium in the rinsing fluids as well as the pH of the fluids is indicated in Table 1 (tests No 1 and 2). The pH of the fluids originating from the rinsing stations Sx to S3 and S7 to S9 was not adjusted with pH adjusting agents. During ultrafiltration, the concentrated fluid was conducted through the ceramic membrane filter at a flow rate of 2,800 l / h. The flow velocity of the obtained permeate was 40 to 45 1 / h. After ultrafiltration, a permeate fluid and a concentrated fluid were obtained. The concentrations of palladium in the permeate and in the concentrate according to tests No 1 and 2 are also indicated in Table 1.

Example 2: In another test, a mixture of flushing fluids of colloidal activation fluid and acid etching solution was prepared at a volume ratio of 1: 1 (test No 3). The same ceramic membrane filter was used as in Example 1. The initial concentration of palladium in the combined rinse fluids and the pH of the mixture are indicated in Table 1. To adjust the pH of the combined rinse fluids to 7 , a solution of NaOH was added to the rinsing fluid. The permeate solution obtained after the ultrafiltration was carried out had a palladium concentration of < 0.5 mg / 1. The concentration of palladium in the concentrate was > 1 g / 1 (see Table 1).

Example 3: In another test No 4, the same membrane ceramic filter was used as in Example 1. Activation colloidal fluid was added at a volume ratio of 1: 100 to the mixture of rinsing fluids obtained according to Example 2. The concentration of palladium in this fluid was equal to 15.0 mg / 1. The pH of this fluid was adjusted to 7 by means of NaOH solution. The concentrations of palladium in the permeate fluid and in the concentrate after the ultrafiltration was performed are indicated in Table 1.

Example 4: In another test No 5, the same membrane ceramic filter was used as in Example 1. In this test, the solution of an ionogenic activator was used in place of a colloidal activation solution. The activator contained an organic palladium complex (Neoganth "Activator, Atotech Deutschland GmbH, Germany), the concentration of palladium in this solution was 250 mg / L. The printed circuit boards activated with this solution were re-treated in a cascade of Rinse three rinse stations Yes, S2 and S3, the flow direction of the rinse water corresponding to that shown in Figure 2. The concentration of palladium in the rinse water originating from the rinse station Si was approximately 1.5 mg / l. To adjust the ultrafiltrability of the rinse water, an aqueous solution of 467 g / l of sodium dimethyl-dithiocarbamate was added to the rinse water. The palladium concentrations obtained in the permeate and in the concentrate as a result of the ultrafiltration of this solution are indicated in Table 1 (Test No 5).

Example 5: In another test No 6, the same membrane ceramic filter was used as in Example 1. In this test, the rinse water obtained according to Example 4 was mixed at a volume ratio of 100: 1 with the activation bath solution. An aqueous solution of 10 g / 1 of sodium sulfide was added to the mixture. The initial concentration of palladium was 8.0 mg / 1. The concentrations of palladium in the filtrate and in the concentrate after ultrafiltration are indicated in Table 1. The tests described herein above produced concentrated fluids having a considerable amount of slurry. After the slurry had settled, the concentrate was distributed to a filter press. The concentration of palladium in the enriched concentrate accounted for 2 to 5 g / 1. The filter cake obtained during compression had a concentration of palladium of. 2 to 15 weight percent.

Example 6: In another test No 7, the same membrane ceramic filter was used as in Example 1. A mixture according to Example 5 was added at a volume ratio of 2: 1 to the rinsing fluid mixture obtained from according to Example 2. The concentration of palladium in this fluid was 4.2 mg / 1. The pH was adjusted to 7 by means of NaOH solution.

In addition, an aqueous solution of 467 g / 1 of sodium dimethyl dithiocarbamate was added to the fluid. The concentrations of palladium in the permeate and in the concentrate after the ultrafiltration has been performed are shown in Table 1. It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications and changes in the view thereof as well as combinations of the features described in this application will be suggested to the person skilled in the art and will be included within the spirit and scope of the described invention and within the scope of the appended claims. All of the publications, patents and patent applications cited herein are hereby incorporated by reference.

Table 1 : 25 List of reference numbers: 1 ceramic filter membrane 2 'ceramic filter layer 3 highly porous ceramic support tube 4 flow direction 10 processing plant for printed circuit boards 11.1, 11.2 storage tanks 12.1 - 12.5 pumps 13.1 - 137 ducts 14 reservoir 15 pH probe 16 collection tank 17.1 lower fill level sensor 17.2 upper fill level sensor 18 pump 19 container 20 collection tank 21 filter press 22 duct A-Pd activation station B post station treatment Si -9 rinse stations C-Pd acid etching station M hand removal

Claims

CLAIMS 1. A method for coating work pieces with a fluid, the fluid containing at least one precious metal, the method comprising contacting the work pieces with the fluid, filtering the fluid after the plating of the work pieces through at least one ceramic membrane filter to separate the at least one precious metal from the fluid, wherein the membrane ceramic filter has an exclusion pore size of more than 10,000 Daltons. The method according to claim 1, wherein the at least one membrane ceramic filter has an exclusion pore size ranging from about 15,000 Daltons to about 25,000 Daltons. The method according to claim 2, wherein the at least one membrane ceramic filter has a pore size excluding approximately 20,000 Daltones. The method according to any of the preceding claims, wherein the at least one membrane ceramic filter is made of an aluminum oxide material / titanium dioxide / ceramic zirconium dioxide. 5. The method according to any of the preceding claims, wherein the work pieces are suitable for the manufacture of electric circuit carriers. 6. The method according to any of the preceding claims, wherein the precious metal is palladium. The method according to claim 6, wherein, after the plating of the work pieces and before filtering the fluid through at least one ceramic membrane filter, the fluid is mixed with suitable chemical substances to alter the at least one precious metal in such a way that the precious metal is retained substantially completely during filtration. The method according to claim 7, wherein the palladium is present in ionic and / or ionogenic form and wherein the fluid is mixed with chemicals selected from the group comprising reducing agents, sulfur compounds, selenium compounds and compounds of tellurium. The method according to claim 8, wherein the chemical substances are selected from the group comprised of boron hydrides, amine boranes, hypophosphites, inorganic sulphides and thio-organic compounds. The method according to claim 9, wherein the palladium is present in colloidal form and wherein the chemicals are pH adjusting agents that are mixed with the fluid in such a way that the pH of the solution varies from 3 to 12. The method according to any of claims 7 to 10, comprising the following method steps: a. the workpieces are brought into contact with a processing fluid containing palladium, b. then, the processing fluid that is still adhered to the surface of the work pieces is removed with rinsing fluid, and c. the processing fluid and / or the rinsing fluid are passed through at least one ceramic membrane filter for filtering them, the fluid which is passed through at least one ceramic membrane filter which is a permeate fluid and fluid that has not passed through at least one ceramic membrane filter, which is a concentrated fluid. The method according to claim 11, wherein the processing fluid and / or rinsing fluid are mixed with the chemicals before they are conducted through at least one ceramic membrane filter. The method according to any of claims 11 and 12, wherein a rinse fluid containing a maximum of 5 volume percent of the processing fluid is conducted through at least one ceramic membrane filter. The method according to claim 13, wherein the workpieces are brought into contact per unit of time with a predetermined amount of fresh rinse fluid and wherein the amount of permeate fluid formed per unit time is approximately equal to the amount of rinsing fluid put in contact with the work pieces per unit of time. 15. A device for plating workpieces with at least one fluid containing precious metal, the device comprising a means for contacting the workpieces with the fluid as well as a retention means for the workpieces, the fluid also comprising an installation for separating at least one precious metal from the fluid, the installation that comprises at least one ceramic membrane, at least one pump for distributing the fluid to at least one ceramic membrane as well as fluid conduits for conducting the fluid from the medium for contacting the workpieces with the fluid to at least one ceramic membrane , wherein at least one ceramic membrane has an exclusion pore size of more than 10,000 Daltons. The device according to claim 15, wherein at least one ceramic membrane has an exclusion pore size ranging from 15,000 Daltones to about 25,000 Daltones. The device according to any of claims 15 and 16, wherein at least one ceramic membrane has an exclusion pore size of approximately 20,000 Daltones. The device according to any of claims 15 to 17, wherein the installation for separating at least one precious metal from the fluid is further provided with a mixing facility by means of which the fluid coming from the means for contacting the Work pieces with the fluid can be mixed with chemicals. 19. The device according to any of claims 15 to 18, wherein a multiple phase separation unit is provided in which the slurry produced is produced. during the separation and coming from the installation to separate at least one precious metal from the fluid, it can be deposited in the fluid. 20. The device according to any of claims 15 to 19, wherein at least one ceramic membrane is made of a ceramic material of aluminum oxide / titanium dioxide / zirconium dioxide.