DK151196B - PROCEDURE FOR PREPARING A SENSIBILIZATION OF SURFACES WITH REGARD TO THE MARKETING OF METAL FROM AN AIRLESS WORKING METAL DISPOSAL - Google Patents

Description

151196 i

The invention relates to a process for preparing sensitization solutions containing stabilized noble metal compounds, as further specified in the preamble of claim 1.

Solutions of this kind are used to make a substrate surface catalytic for powerless metal deposition on the surfaces.

Powerless deposition of a metal on a metallic or non-metallic substrate usually requires a preprocessing of the substrate to make this catalytic for metal reception easy. Various methods have been developed based on the use of different sensitizers.

In one of the oldest methods, several baths are used, the substrate being first dipped in a stannous chloride solution and then 15 in an acidic palladium chloride solution. Later, a one-step treatment using a colloidal dispersion of precious metal particles, e.g. palladium particles, and a Group IV polyvalent metal, e.g. tin, cf. U.S. Patent No. 3,001,920. Significant improvement was achieved in the development of optically clear, true solutions of Group IV precious metal and metals. Eg. are described in U.S. Patent No. 3,672,938 reaction products of palladium dichloride and tin dichloride, and their sensitizers. These are available both in the form 25 of concentrated solutions, cf. U.S. Pat.

3,682,671, or in the form of dry powder which can be dissolved to form a sensitization solution, cf. U.S. Patent No. 3,672,923. Details of components used, conditions, methods of use, etc. can be found in the aforementioned patents.

The multi-bathing process provides good sensitization, but has the disadvantage of forming a thin precious metal coating on metal substrates. This deposition of precious metal from the sensitization bath causes the stability of the precious metal salt solution to deteriorate and its concentration to change.

In order to maintain the catalytic activity it is necessary to constantly add more precious metal salt solution 5 to the bath, which of course makes the process of several baths more costly. Furthermore, a thin coating of precious metal usually results in a low degree of adhesion, which significantly impairs the later powerless deposited metal coating's adhesion strength and resistance to peeling.

The disadvantage of depositing a thin coating is generally avoided using the colloidal baths process of U.S. Patent No. 3,001,920, but this instead causes the disadvantage of a reduced reactivity, requiring a higher concentration of precious metal, and the bath requires a longer time for sensitization. In addition, double metal colloids are needed to improve stability.

Since the precious metal is in colloidal form, it is not possible to prepare and store or transport 20 dilute dispersions with high colloidal concentrations, as the colloidal dispersion is destroyed by flocculation.

As explained in the aforementioned U.S. Pat.

Nos. 3,682,671 and 3,672,923, one-bath concentrated or dry sensitizers are very valuable, as transport and storage costs are low and easier to maintain working solutions. A major disadvantage of such solutions is that they tend to become unstable, especially when exposed to the influence of air. After a few weeks under such conditions, precious metal is separated from the solution as a metal film on the surface of the solution and sometimes as a grainy precipitate.

If the solution in this state is used to sensitize surfaces for powerless plating by dipping the surfaces into the solution, the surface 35 is coated with a precious metal layer which cannot be easily removed by rinsing.

If the powerless plating is performed without removing the precious metal coating, the deposited metal will adhere poorly to the underlying surface.

GB Patent No. 1,174,851 discloses one-bath type sensitization solutions of improved stability obtained by adding a water-soluble hydroxyl group-containing organic compound, e.g. an alcohol, glycerol or a sugar substance. According to this patent, aromatic hydroxyl compounds such as resorcinol, pyrocatechol and guinol are the best stabilizers since they can be used at somewhat lower concentrations than alcohols, sugars and the like. It is sufficient to add these water-soluble aromatic hydroxyl compounds to the sensitizing solution after its preparation to make it stable for at least five months. There is no suggestion in this patent that the ingredients should be brought together in any particular way and no mention is made of the appearance, especially the color, of the stabilized sensitization solutions.

While the above-mentioned GB Patent No. 1,174,851 has admittedly shown a stable active sensitization solution, but if the hydroxyl-containing compound is only added to the sensitizer solution at the indicated concentrations, the solutions become rather slow, normally requiring treatment times of 15-20 minutes. However, after 25 prolonged storage, there is still a certain tendency to precipitate precious metal from the solution with the disadvantages mentioned above as a result.

It has now been found that if a hydroxyl group-containing aromatic compound of the kind disclosed in the aforementioned GB Patent No. 30,174,851 is added in a particular manner and at a suitable time during the preparation of a soluble metal complex sensitizer of the kind specified in the aforementioned U.S. Patent Nos. 3,672,923, 3,672,938 and 3,682,671, a reaction product is formed which apparently contains the hydroxyl group-containing aromatic compound. Such solutions have surprisingly been found to exhibit a substantially increased rate of sensitization, in some cases operating twice as fast as the best known solutions. Furthermore, a considerable improvement in stability and a substantially improved final product is obtained, especially compared to the stabilized sensitizer according to the above-mentioned GB patent specification 1,174,851. As will be seen from the 10 differences in color mentioned below, another product is formed which is probably due to the presence of a complex of the noble metal and the hydroxyl group-containing aromatic compound. For example, using palladium and resorcinol, a red complex is formed and this color has not previously been observed with these components.

As to what is stated in the aforementioned GB Patent Specification No. 1,174,851, it is surprising that not all hydroxyl-containing compounds work. For example, 20 isopropanol disclosed in the patent as preferred stabilizer does not form the reaction products of the invention.

It is thus the object of the invention to provide a method for producing a high-sensitivity and stable sensitizer. Such sensitizers must also be capable of being produced in the form of concentrates and diluent solid compositions, as is generally described in the aforementioned U.S. Patent Nos. 3,672,923 and 3,682,671. The process should also be capable of producing stabilized compositions which have a greater activity as sensitizers and are very resistant to the influence of contaminants and which provide more stable sensitizers with less material consumption.

Said object is achieved by a method of the type mentioned in the invention, which according to the invention is peculiar to the process steps specified in claim 1.

The sensitizer solution thus obtained consists of a liquid medium in which the reaction products are dissolved. The liquid 5 may vary, but should be inactive against the ingredients. Preferably, the liquid consists of water or a liquid organic oxygen compound. Examples include alcohols, e.g. methanol, ketones, e.g. cyclohexanone, and ethers, e.g. dibutyl ether.

10 Precious metals that can be used as component A are those included in the fifth and sixth periods of groups IB and VIII of the periodic table. In particular, mention may be made of palladium, platinum, gold, rhodium, osmium and iridium. The preferred metal of Group IV is tin, especially in stannous form.

If the liquid medium is water, it is convenient to maintain the pH of the solution below ca. 1. If anhydrous media is used where pH measurements are not reliable, it is in all cases most appropriate to have a high acidity.

20 in preferred compositions, the noble metal ions are included as a reaction product with the constituents G, D and E, of which the latter two have a stoichiometric excess. The preferred compositions contain a soluble reaction product of noble metal ion, Group IV metal, a hydroxyl group-containing aromatic compound and a suitable anion, and the solution additionally contains a stoichiometric excess of stannous ion and a hydrogen halide, e.g. HCl or HBr in a sufficient amount to give an excess of the anion.

It will be obvious that both the ordinary and the particular parts of the present disclosure explain the invention on the basis of examples. Thus, the deposition of copper is further described, but the invention can also be used in the deposition of other metals such as nickel, palladium, cobalt, silver and gold.

The stabilized compositions obtained by the process 5 according to the invention enable sensitizing conductive and non-conductive materials at the same time in such a way that an even adhesive metal layer can be easily deposited by a powerless path. In this way, e.g. It is possible to copper plate the sidewalls in holes in plastic material, at the same time as there is a currentless deposition of copper on pre-formed copper surfaces on the substrate. Thus, coatings of uniform thickness can be deposited on articles of iron, nickel, cobalt, silver, gold and alloys, e.g. stainless steel, brass and sterling silver.

The sensitization solutions consist of solutions in a liquid of a reaction product of a noble metal, a group IV metal, an anion and the aromatic hydroxyl compound in the form of e.g. non-colloidal, optically clear solutions.

As mentioned above, the precious metals are palladium, platinum, gold, rhodium, osmium, iridium or a mixture thereof. Salts with organic and inorganic acids of these metals and the metals of Group IV, e.g. chlorides, bromides, fluorides, fluoborates, iodides, nitrates, sulfates and acetates of divalent tin, titanium and germanium can be used to form constituents A, D and E. Other salts and compounds of the noble metals and metals of group IV can be readily selected by professionals in the field. The salts and compounds are suitably soluble in water or in aqueous solutions of organic or inorganic acids.

As the anion E, the chloride ion is preferred, both for the noble metal compound and the compound of the group IV metal. The preferred precious metals are palladium and platinum, and the preferred metal in group IV is tin, especially in stannous form.

In the sensitization bath, the concentration of precious metal ion ranges from 0.0003 g / l to 10 g / l, preferably in the range of 0.01 to 5 g / l. In the upper part of this area, sensitization can be completed in a very short time, e.g. 10 s, but usually the bottom 5 of the area is more economical. The bath may be prepared directly or by dilution of a concentrate, e.g. with a content of noble metal ion of 4-8 g / l or more. Of course, dry concentrates can also be dissolved and diluted to the normally used concentrations.

It can be proceeded with by diluting the concentrates or dissolving the solid compositions with water, an appropriate organic liquid, e.g. methanol or cyclohexanone, or an aqueous solution of a suitable acid. The composition is prepared by reacting the noble metals with a group 15 metal in the form of salts in a liquid medium, e.g. an aqueous solution of a suitable acid as mentioned below. Among the acids that can be used are hydrochloric acid, hydrogen fluoride, fluoroboric acid, hydrogen iodide, sulfuric acid and acetic acid. Preferably, the anion of the inorganic acid 20 corresponds to the anion in the noble metal salt or the anion in the salt of the metal of Group IV. If the anions in the noble metal salt and the salt of the metal in Group IV are the same, the anion in the acid in the sensitization solution should preferably correspond to the common anion of the salts. If the anion in the precious metal salt differs from the anion of the second salt, the anion of the acid used, if any, should preferably correspond to the anion of the precious metal salt. Obviously, it is also possible to use an acid whose anion differs both from the anion of the precious metal salt and from the anion in the salt of the metal of Group IV.

In any case, the preferred anions are the chloride ion (Cl ”) and the trichloro ion (SnClg), as well as mixtures thereof.

In acidic preparations, the acid content of the sensitization solutions and in the concentrates depends on the strength of the acid used. For best results, use a solution that is at least 0.001 N. for acid, on the other hand, the solution may be 15 N with respect to the acid, especially when it is a concentrate. When strong acids are used, the acid concentration in the sensitization solution approaches the upper limit indicated. The acid concentration in the sensitization solution should, of course, be sufficient to make the salts of the noble metal and of the Group IV metal soluble, and sufficient to make the solution suitable as a sensitizer for the material to be treated. When choosing the acid concentration, care must be taken that the treated item is not attacked or corroded by the treatment solution.

The concentration of the ion of the metal in Group IV may be varied within wide limits, but it must be kept above the stoichiometric amount with respect to the amount of noble metal ion in the sensitization solution. Although usually a large surplus of e.g. stannous chloride to enable air oxidation of the stannous ion, such large excesses are not needed when the noble metal is complexed with an aromatic hydroxyl compound. Concentrations as high as 60 g / l or more of the group IV metal ion are not detrimental to the sensitization activity of the diluted solutions.

The use of aromatic hydroxyl compounds as constituents in sensitization solutions of the invention gives these solutions a remarkable stability and ability for rapid sensitization without formation of noble metal deposits on surfaces, e.g. metal surfaces exposed to these solutions. The chemical properties of the aromatic hydroxyl compound 30 are not essential. The compound may be simple or complex, but at least one hydroxyl group should be attached to the aromatic ring. Other groups, e.g. sulfonate, nitrate, alkyl or halogenide groups may also be present. It is easy to establish the effective stabilization in comparison with control baths, i.e. baths without aromatic hydroxyl compound. These are marketed in approx. a week a membrane or a precipitate of precious metal. Baths containing the described complex A.D.E.G, on the other hand, remain clear and stable and can be stored for extended periods of time.

The component G is preferably a benzene or naphthalene derivative containing one or more nucleus substituting hydroxyl groups. Such suitable compounds are e.g. resorcinol, pyrocatechol, hydroquinone, floroglucinol, phenol, pyrogallol, anthraquinone and sulfonated phenols. Preferably, resorcinol is used.

In preparing sensitization solutions by the process of the invention, it is necessary to combine the components and react with one another in a specific order so that the components of the solutions do not react to form a colloidal dispersion, colloidal agglomerates or mixed complexes instead of the reaction product of four constituents.

In the process of the invention, the compositions are generally prepared by mixing a solution of the noble metal salt with the organic hydroxyl compound, thereby forming a soluble reaction product or a soluble complex, cf. Chemical and Engineering News, April 21, 1969, pages 48-52. The solution is mixed with a solution of the cation of the metal in group IV. One solution or preferably both solutions contains the anion E. In general, a solution of A, E and G is mixed with a solution of D and E and given the opportunity to react to form complex A.D.E.G. It is most convenient to accelerate the formation of the complex A.D.E.G. by. heating, and the evolution of the reaction can be followed by e.g. to monitor the course of the color changes. These are described below.

Heating to a temperature between approx. 65 ° C, preferably about 111196 or approx. 85 ° and the boiling point of the solution has been found to support formation of the complex at an appropriate rate. Usually the heating takes place for a period of 20 minutes. to 6 hours. Heating for 2 - 3 hours at the boiling point is generally 5 sufficient.

A solution suitable for direct use contains the following ingredients (calculated on an unreacted basis): 0.001 - 5 g / l A, preferably 0.2 - 2 g / l A, 15 - 60 g / l D, 5 -20 g / l E and 1 - 25 g / l G. A suitable dilute concentrate contains (calculated in the same way) 4-10 g / l A, e.g. palladium or platinum ion, 400 - 600 g / l D, e.g. stannous ion, 150-400 g / l E, e.g. chloride ion, and 25 g / l until saturation G, e.g. resorcinol, pyrocatechol, hydroquinone, anthraquinone, phenol or floroglucinol. Typical upper limits are 200 g / l, 175 g / l and 75 g / l in water, methanol and cyclohexanone. The concentrate can be evaporated to dryness in vacuo to give a brittle, dry solid, as described in U.S. Patent No. 3,672,923. Both the concentrate and the solid can be diluted with water, an aqueous solution of an acid or anhydrous medium immediately before use, as described in the above-mentioned patents.

Since the cleaning of the substrate and the powerless deposition of metal thereon are well known to those skilled in the art, reference is made to the above-mentioned patents for details. The sensitization of a clean substrate is described in more detail below.

In a preferred embodiment, a wetting agent is usually used in the sensitizer composition.

For this purpose, fluorinated surfactants such as perfluorodecanoic acid and such commercial products as the product designated "FC-95" by The 3M Company are preferred. Small amounts of the order of 0.25 - 2.5 g / l are used.

151196 11

The process according to the invention will be further elucidated in the following examples.

Example 1.

A first solution is prepared by dissolving 160 g of resorcinol in 170 ml of distilled water. This solution is pale yellow. As the reaction is endothermic, the dissolution process will be accelerated by gentle heating. Another solution is prepared by dissolving 8 g of palladium dichloride (PdCl 2) in 80 ml of 37% hydrochloric acid for sufficient time to dissolve all 10 palladium chloride. The solution is brown. The first solution is then added to the second solution and the mixture is allowed to stand for 0.5-1 hours. This solution is dark brown. A third solution is prepared by mixing 65 ml of deionized water with 441 ml of 37% hydrochloric acid and dissolving therein 560 g of anhydrous stannous chloride. A small amount of precipitate and residues are removed by filtration. To 720 ml of the third solution slowly add 360 ml of the mixture of the first and second solution. The mixture thus obtained first turns temporarily dark blue, changes color to teal and then to green. The mixture is then heated to ca. 100 ° C and then kept between 100 and 110 ° C for a total of 2-3 hours. The concentrated reaction product is given the opportunity to cool to room temperature where it has a violet brown color and is examined for palladium and stannous ions. When diluted with 4 N hydrochloric acid, the color turns reddish brown. Adjustment of excess ions is carried out by addition of hydrochloric acid, water and stannous chloride. This process gives a composition containing 8 g / L PdCl 2, 500-560 g / L SnCl The product is stable for several months and, after dilution to working concentration, sensitizes all the usual substrates very quickly and efficiently.

151196 12

Example 2.

A solution is prepared by dissolving 160 g of resorcinol in 140 ml of water. Another solution is prepared by dissolving 8 g of palladium chloride in 80 ml of 37% hydrochloric acid. Dilute 150 ml of the first solution with 26 ml of water and add this mixture to the second solution. A third solution is prepared by dissolving 560 g of tin dichloride in 475 ml of water. The rest, i.e. 130 ml of the first solution are added to the third solution. This results in a light yellow solution. Finally, the mixture of the diluted portion of the first solution and the second solution is added slowly to the mixture of the third solution and the non-diluted portion of the first solution, and this mixture is given the opportunity to react in the same manner as in Example 1. .

15 The color changes are essentially the same, and a stable, high-efficiency sensitization concentrate appears.

Example 3

Dilute 63 ml of the concentrate of Example 1 with a mixture of 620 ml of water and 320 ml of 37% reagent grade hydrochloric acid to a concentration of palladium chloride equal to 0.5 g / l. A clean plate is immersed in the sensitization bath for a suitable period of time, e.g. from 3-15 min.

The surface of the plate, including any side walls of holes in the plate, is then rinsed thoroughly with water to completely remove the sensitization solution. The plate is then placed in a bath of dilute fluoroboric acid on e.g. 10% and kept immersed for from 10 - 30 seconds and then rinsed with water. The sensitized plate can then be immersed in a generally streamless metal deposition bath in the form of an aqueous solution of a salt of the metal to be deposited, a reducing agent for the salt, and various additions to improve the stability of the solutions. The powerless metal deposition can be followed by electrolytic plating 35 with copper or other metals to a metal thickness of 0.05 to 0.25 mm or more.

Example 4

The procedure of Example 1 is repeated using 4.35 g of platinum chloride (PtC 2) instead of palladium chloride. A stabilized platinum ion-containing sensitization solution appears.

Example 5

The procedure of Example 1 is repeated with 8 g of osmium chloride instead of 8 g of palladium chloride. A stabilized osmium ion-containing sensitization solution is obtained.

Example 6

A solution is prepared by dissolving 64 g of pyrocatechol in 200 ml of water. Another solution is prepared by dissolving 8 g of palladium chloride in 80 ml of 37% hydrochloric acid under moderate heating and for a sufficient period of time to dissolve all palladium chloride. The first solution is added to the second solution and the mixture is allowed to stand for 30 - 60 minutes. A third solution is prepared by mixing 65 ml of deionized water with 441 ml of 37% hydrochloric acid and dissolving therein 550 g of anhydrous stannous chloride. A small amount of precipitate and residues are filtered out. To 720 ml of the third solution slowly add 360 ml of the mixture of the first two solutions. The mixture thus obtained is heated to ca. 100 ° C and then allowed to stand 25 at 100 - 110 ° C for a total of 2-3 hours. The concentrated reaction product is allowed to cool to room temperature and adjusted to the desired concentration with 4N hydrochloric acid. A stable active sensitization solution appears.

Example 7.

The procedure of Example 6 is repeated with a solution of 68 g of pyrogallol in 200 ml of water as the first solution.

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A stable active sensitization solution appears.

Example 8.

The procedure of Example 1 is repeated with a solution of 24 g of hydroquinone in 200 ml of water as the first solution.

5 A stable active sensitization solution appears.

Claims (7)

151196 A process for preparing a surface sensitizing solution for depositing metal from a powerless metal deposition bath / solution containing (a) a precious metal component A in the form of a noble metal in period 5 or 6 of Group VIII or IB in the periodic table, b) an element D in the form of a group IV metal in the periodic table, c) an anion component E in the form of an anion capable of forming stable, water-soluble complex compounds with both of the aforementioned and d) a component G in the form of an aromatic compound carrying at least one hydroxyl group, L characterized in that: 1. the component A in aqueous solution is reacted with the component G at elevated temperature, and the reaction product thus obtained is mixed with the other components to form a complex according to the formula AGDE Process according to claim 1, characterized in that the reaction product A.G is mixed with a stoichiometric excess of components D and E. Process according to claim 1, characterized in that the component G is used in stoichiometric excess during the reaction with the component A. Process according to claim 2, characterized in that component A is used at a concentration of 0.2-2 g / 1 and component G at a concentration of 1-25 g / 1 and that components D and E are mixed in concentrations. of 15 - 60 g / l and 5-20 g / l respectively. 151196 Process according to claim 1, characterized in that palladium is used as component A, that resorcinol is used as component G, that stannone ion is used as component D and that chloride ion is used as component E. Process according to claim 1, characterized in that, as component G, pyrocatechol, hydroquinone, anthraquinone, phenol or floroglucinol or a mixture thereof are used. Process according to claim 1, characterized in that the components are used at the following concentrations: component A 4 - 10 g / 1 / component G 25 g / 1 up to saturation, component D 400 - 600 g / 1 and component E 150 - 400 g / l and that after the reaction a concentrate of the sensitizing solution is formed.