Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/48—Coating with alloys
  • C23C18/50—Coating with alloys with alloys based on iron, cobalt or nickel

Definitions

• the invention relates to a method for the external currentless deposition of ternary alloys containing the elements nickel and phosphorus.
• electrochemical metal deposition which is in principle a method based on redox processes in the solution, can be used in electroless plating , an external power source and corresponding electrodes are completely dispensed with.
• a metal layer which can consist of a metal, semiconductor or also non-metal, is immersed in a suitable electrolyte after appropriate cleaning of the surface. If certain conditions are adhered to (composition of the electrolyte, pH value, temperature etc.), a metal deposit is deposited on the surface of the immersed object. This usually contains not only the metal deposited from the solution, but also other electrolyte components that can strongly influence the properties of the deposited layer.
• the electrons required to reduce the solvated metal ions are supplied by suitable reducing agents, which in turn are oxidized.
• suitable reducing agents which in turn are oxidized.
• the desired redox process must not take place in the entire volume of the electrolyte, but must be limited to the surface of the objects to be coated.
• a limitation is achieved by adding stabilizers and accelerators to the electrolyte on the one hand and by activating the surface to be coated before immersion on the other hand.
• Stabilizers or accelerators for the solution are necessary components of the baths for the electroless deposition of metals on metallic or non-metallic objects. With their help, the process can be controlled in a suitable manner ("Ullmann's Encyclopedia of Industrial Chemistry" Volume 12, pages 156 ff, Verlag Chemie, Weinheim (1976)).
• the object of the present invention was therefore to provide a practical method for the external currentless separation of ternary systems from aqueous solutions.
• a method should be found to deposit ternary alloys from aqueous solutions on metallic or appropriately pretreated non-metallic base materials which, in addition to nickel and phosphorus, contain cobalt or tungsten as the third element.
• the invention relates to a process for electrolessly, chemically reductive deposition of ternary alloys containing nickel and phosphorus from aqueous solutions containing nickel ions and sodium hypophosphite or other reducing agents in the presence organic compounds as complexing agents, stabilizers, accelerators, wetting agents and brighteners, which is characterized in that metallic or non-metallic materials after appropriate pretreatment for the deposition of ternary Ni-WP alloys at a pH in the range from 4.5 to 9, 5 immersed in an aqueous solution containing 2.0 to 6.0 g / l of Ni2+ ions, 6.5 to 17.5 g / l of WO42 ⁇ ions, 15.0 to 40.0 g / l of sodium hypophosphite or a corresponding amount of other reducing agents and optionally 30.0 to 60.0 g / l H3BO3 or 60.0 to 65.0 g / l (NH4) 2SO4 or 40.0 to 60.0 g / l NH4C
• All metallic or non-metallic materials are suitable as substrates onto which ternary alloys containing nickel and phosphorus can be deposited according to the method according to the invention, onto which binary, nickel and phosphorus are also deposited according to the prior art method for electroless plating Alloys can be deposited.
• Suitable metallic materials are, for example, materials made of brass, copper or also of aluminum, iron and other, comparatively base metals.
• non-metallic objects are coated with metal layers. As such, for example, glass, quartz in various modifications, plastics, in particular for printed circuit boards, etc. come into question.
• the corresponding surfaces are pretreated according to methods known per se before using the method according to the invention.
• Such pretreatment processes can consist of degreasing corresponding to the corresponding metallic or non-metallic material.
• all methods known from the prior art can be used for the respective material without restriction.
• ternary alloys which are said to contain tungsten and phosphorus according to the invention
• the corresponding materials to be coated with an alloy layer are immersed in an aqueous solution containing 2.0 to 6.0 g / l of Ni 2 - Contains ions, 6.5 to 17.5 g / l WO42 ⁇ ions and 15.0 to 40.0 g / l of a reducing agent.
• the preferred reducing agent is sodium hypophosphite, so that according to a preferred embodiment of the process according to the invention the aqueous solution contains 15.0 to 40.0 g / l sodium hypophosphite.
• the objects are preferably immersed in aqueous solutions, the nickel ions in quantities of 4.7 to 5.1 g / l, tungsten ions in quantities of 9.5 to 11.1 g / l and sodium hypophosphite in quantities of 25.0 to 40, 0 g / l included.
• the quantity ranges of the respective ions can be varied independently of one another as long as the molar ratio of the nickel ions to the tungsten ions is in the range from 1: 1.5 to 1: 3.25, preferably in the range of 1: 2 to 1: 2.2 remains.
• the pH of such aqueous solutions which enable the deposition of homogeneous, closed layers of a ternary Ni-WP alloy, are in a range from 4.5 to 9.5, with a range of 4 for deposition in acidic electrolyte baths. 5 to 5.0 and a range from 8.0 to 9.0 is preferred for the deposition in alkaline electrolyte baths.
• Deposition in the acidic pH range can bring values as good as a deposition in the alkaline pH range.
• aqueous solutions which can be used according to the invention for the deposition of ternary Ni-W-P alloys can additionally be used for purposes which are already known from the prior art and, inter alia, the buffering and pH adjustment of the solutions include, if desired, additional boric acid (H3BO3) in amounts of 30 to 60 g / l or ammonium sulfate in amounts of 60 to 65 g / l or ammonium chloride in amounts of 40 to 60 g / l contain.
• H3BO3 additional boric acid
• the metallic or non-metallic materials are immersed in an aqueous solution containing 2.5 to 8.0 g / l of Ni2+ ions, 2.5, after appropriate pretreatment contains up to 8.0 g / l CO2+ ions and 15.0 to 40.0 g / l of a reducing agent.
• the preferred reducing agent is sodium hypophosphite, so that, according to a preferred embodiment of the process according to the invention, the aqueous solution 15.0 to Contains 40.0 g / l sodium hypophosphite.
• solutions can be used for the deposition of ternary Ni-Co-P alloys, the nickel ions in amounts of 3.5 to 5.0 g / l, cobalt ions in amounts of 3.5 to 5.0 g / l and sodium hypophosphite in amounts of 25.0 to 40.0 g / l.
• the amounts of the individual solution components can be varied independently of one another as long as the molar ratio of the nickel ions to the cobalt ions remains in the range from 1: 0.5 to 1: 2, with a molar ratio of the nickel ions to the cobalt ions in the range from 1: 1 to 1 : 1.7 is preferred.
• the pH values of such solutions suitable for the deposition of ternary Ni-Co-P alloys are in the range from 4.5 to 9.5.
• a pH of 4.5 to 4.8 is used for the deposition of such ternary alloys in the less used acidic pH range, and a pH of 8.5 to 9 for the deposition of such alloys in the alkaline pH range , 0 preferred.
• Deposition in the acidic pH range can produce just as good results as deposition in the alkaline pH range.
• aqueous solutions for the deposition of ternary Ni-Co-P alloys can, for purposes known from the prior art, for example for buffering or pH adjustment, optionally additionally boric acid (H3BO3) in amounts of 30.0 to 60.0 Contain g / l or ammonium sulfate in amounts of 60 to 65 g / l or ammonium chloride in amounts of 40 to 60 g / l.
• H3BO3 boric acid
• the process of reducing the metal ions to be deposited does not take place spontaneously in the entire electrolyte volume, but must remain restricted to the surface of the materials to be coated.
• the concentration of dissolved and freely available metal ions in the aqueous solution must not exceed a certain value. This is achieved by adding stabilizers, accelerators and complexing agents to the aqueous solutions on the one hand and by activating the substrates on the other.
• one or more organic carboxylic acids of the general formulas (I) are additionally added to the electrolyte baths which are suitable for the process according to the invention for the electroless deposition of alloys containing ternary alloys containing nickel, phosphorus and cobalt or tungsten. , (II) and / or (III) and / or their alkali metal salts added.
• the substituents R1 for H, OH, Cl, CH3, COOH and C (OH) (COOH) CH2COOH, the substituents R2 and R3 independently of one another for H, OH, and CH2COOH and x for one are an integer in the range from 0 to 5.
• Compounds of general form mel (I) which are added in the process according to the invention in aqueous solutions can be, for example, acetic acid, chloroacetic acid, glycolic acid, propionic acid, lactic acid, tartaric acid, citric acid, succinic acid or adipic acid.
• their alkali metal salts can also be used.
• the sodium salts are primarily considered as such.
• the amounts of the compounds of the general formula (I) and / or their alkali metal salts in the process according to the invention are in the range from 0.01 to 1.0 mol / l, these amounts being calculated per individual substance.
• the substituent R4 can be hydrogen or a carboxyl group.
• suitable aliphatic unsaturated carboxylic acids of the general formula (II) are acrylic acid or maleic or fumaric acid.
• their alkali metal salts can also be used. Of these, the sodium salts are preferred.
• the amounts of the compounds of the general formula (II) and / or their alkali metal salts are in the range from 10 to 100 mmol / l, these amounts being calculated per individual substance.
• the substituent R5 can be hydrogen, a hydroxyl group or a carboxyl group.
• the position of the substituent R5 is possible both in the ortho and in the meta as well as in the para position to the carboxyl group.
• aromatic carboxylic acids of the general Formula (III) thus includes, for example, benzoic acid, salicylic acid, m-hydroxy-benzoic acid, p-hydroxy-benzoic acid, phthalic acid, isophthalic acid and terephthalic acid.
• their alkali metal salts can also be used. Of these, the sodium salts are preferred.
• the amounts of the compound of the general formula (III) and / or its alkali metal salts are in the range from 20 to 60 mmol / l, these amounts being calculated per individual substance.
• sulfonic acids of the general formula (IV) R6SO3H (IV) or their alkali metal salts in question are also possible.
• their alkali metal salts can also be used.
• the sodium salts are particularly advantageous to use.
• the amounts of use of the compounds of the general formula (IV) and / or their alkali metal salts are in the range from 0.4 to 1.0 mmol / l, where these quantities used are also calculated as quantities per individual substance.
• ternary alloy layers containing nickel, phosphorus and cobalt or tungsten are to be deposited in the alkaline pH range, it is possible in one embodiment of the method according to the invention, which can be advantageous for the deposition of well-formed alloy layers to adjust the pH by adding gaseous ammonia or ammonia solutions.
• an alkaline pH is adjusted to the desired size using aqueous alkali metal hydroxide solutions, particularly preferably using aqueous sodium hydroxide solution.
• this offers the advantage that automatic metering via liquid dosimeters is possible and, furthermore, there is no odor nuisance, as is unavoidable when using ammonia.
• the optionally filtered solutions are subsequently brought to the temperature desired for the deposition of the ternary nickel-phosphorus-cobalt or nickel-phosphorus-tungsten layers.
• This is in the range from 75 to 95.degree. C., preferably in the range from 80 to 90.degree. C. and is conveniently advantageously set to a value of 85.degree.
• the process temperature is usually regulated by thermostatting, since the workpieces are immersed in the aqueous solutions in the cold state and this results in permanent heat dissipation.
• the pretreated metallic or non-metallic workpieces are immersed after the pretreatment in the aqueous solutions adjusted to a fixed temperature or a desired pH, whereby they should be moved vertically or horizontally in the solution ("movement of goods"). This can - depending on the desired layer thickness of the ternary alloy layer to be deposited - in a period of 30 to 240 min. happen. In the case of solutions which have the composition described in more detail above, layer thicknesses of the alloy layers of 10 to 50 ⁇ m are obtained.
• the lead out of the aqueous solutions after the treatment time Workpieces coated with ternary alloy layers are then rinsed off with cold water, preferably with deionized water.
• a subsequent process step - as is known from the prior art - it is possible to subject the workpieces to heat treatment in order to obtain harder and more abrasion-resistant layers.
• the heat treatment is advantageously carried out on metallic workpieces and is carried out under a protective gas. Nitrogen is usually used as the protective gas.
• Different treatment conditions can be maintained: For example, it is possible to anneal the workpieces at 400 ° C for 1 hour, thereby significantly increasing their hardness and abrasion resistance. However, it is also possible to anneal the metallic workpieces coated with a ternary alloy layer at 300 ° C. for 2.5 to 5 hours. Here too, layers of good hardness and abrasion resistance are obtained.
• the respective treatment conditions depend on the material of the workpiece and the alloy layer applied.
• annealing conditions in detail are known to the person skilled in the art or can be easily determined experimentally by means of a few preliminary tests.
• the inventive method A method is made available which makes it possible to deposit ternary alloy layers without external current, which in addition to nickel and phosphorus also contain cobalt or tungsten in the coating layers.
• the metal layers mentioned, deposited by the process according to the invention are fine-grained and closed and have the advantage over previously known binary layers containing only nickel and phosphorus that they simultaneously meet high demands on the abrasion resistance and the hardness of the layer even in the state of deposition and are also very corrosion-resistant are. Methods known from the prior art, in particular methods for the deposition of binary layers containing nickel and phosphorus, could not achieve a high standard of all three parameters.
• the metallic workpieces coated with a ternary alloy layer were heat-treated for 1 hour at 400 ° C. or 5 hours at 300 ° C. under N2 as protective gas.
• the hardness of the deposited layer was determined according to Vickers.
• the abrasion resistance of the deposited ternary alloy layers was also determined. This was done with an Erichsen tester.
• the wear removal values obtained with increasing number of double strokes can also be found in Table 2 below. The wear removal values meet the requirements of the draft DIN standard 5966, page 7.

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Citations (5)

• 1987
  • 1987-04-24 DE DE19873713734 patent/DE3713734A1/de not_active Withdrawn
• 1988
  • 1988-04-16 EP EP88106083A patent/EP0289838A3/fr not_active Withdrawn
  • 1988-04-25 JP JP10375288A patent/JPS63286582A/ja active Pending

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