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
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1646—Characteristics of the product obtained
  • C23C18/165—Multilayered product
  • C23C18/1651—Two or more layers only obtained by electroless plating
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2046—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by chemical pretreatment
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30
  • C23C18/2046—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30 by chemical pretreatment
  • C23C18/2073—Multistep pretreatment
  • C23C18/2086—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/22—Roughening, e.g. by etching
  • C23C18/24—Roughening, e.g. by etching using acid aqueous solutions
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/28—Sensitising or activating
  • C23C18/285—Sensitising or activating with tin based compound or composition
• • 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
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/28—Sensitising or activating
  • C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
• • 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
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
• • 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
  • C23C18/31—Coating with metals
  • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
  • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
  • C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites
• • 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
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
• • 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
  • C23C18/31—Coating with metals
  • C23C18/38—Coating with copper
  • C23C18/40—Coating with copper using reducing agents
  • C23C18/405—Formaldehyde

Definitions

• the invention regards the pretreatment of nonconductive plastic surfaces prior to their metallization and may be applied in various industries where decorative or functional metal coating of plastic parts is required.
• the pretreatment is performed in a solution of free of hexavalent chromium.
• a conventional method of pretreatment of nonconductive plastic surfaces prior to their electroless metallization mostly electroless nickel-plating or copper-plating, consists of etching the surface in hexavalent chromium containing solution, followed by the activation in a ionic or colloidal solution of palladium compounds and either the reduction in the sodium hypophosphite solution (in most cases) or the acceleration in an acid solution (usually hydrochloric acid) of the palladium ions or colloidal palladium particles, respectively, adsorbed on the plastic surface.
• Etching during of the pretreatment step of the nonconductive substrate surface is required for hydrophylisation purposes so that the surface becomes hydrophilic in other phases of the process in water solutions, with sufficient quantities of palladium salts adsorbed, and for ensuring proper binding of the metal coating to the nonconductive plastic surface.
• the activation with the subsequent reduction or acceleration is performed in order to initiate the electroless deposition of the metal on the plastic.
• electroless plating with metal in the metallization solution takes place through auto-catalytic reaction where the metal deposited on the surface acts as a catalyst for further depositing.
• the metals nickel and copper are mostly used for this electroless plating.
• electrolytic or galvanic plating can be performed on the first metal layer.
• Various metals can be applied, for example chromium, nickel, copper and brass or other alloys of the foregoing metals.
• the main shortcomings of the conventional method are related to the cancerogenicity of the chromic acid in the etching solution. Furthermore the metal deposited during the electroless deposition step, for example a nickel, also covers parts of rack insulated with plastisol, which results in the metal losses in the solutions of subsequent metal plating electrochemically and therefore is undesired.
• US Patent Application No. 2005/0199587 A1 discloses a method of etching of nonconductive plastic surfaces in an acidic solution containing 20-70 g/l of potassium permanganate.
• Optimal KMnO 4 concentration in above mentioned solution is close to 50 g/l.
• concentration is below 20 g/l, the solution is ineffective, with the upper concentration limit determined by the solubility of potassium permanganate.
• the etching is followed by the activation in a palladium salt solution containing amine and by further reducing treatment, e.g. in a borohydride, hypophosphite or hydrazine solution.
• etching in the permanganate solutions activates the surface of the rack's plastisol insulation as it is coated with the product of the etching reaction, i.e. manganese dioxide.
• the latter stimulates adsorption of palladium compounds on plastisol, which tends to metallize in the solutions of electroless metal deposition.
• Formation of manganese dioxide on surfaces is characteristic of the permanganate etching solutions of any composition. Therefore, a very important objective of the present invention is to avoid rack metallization and resulting metal losses in the subsequent metallisation stage.
• Lithuanian patent application number LT 2008-082 also concerns the pretreatment of nonconductive plastic surfaces prior to metallisation.
• a pretreatment composition for etching e.g. polyimide for 1-2 minutes with a temperature of 10-80° C., 0.005-0.2M oxidizing solution in sulfuric acid in a concentration of between 13 mol/L (about 75 vol. %) and 17 mol/L (about 90 vol. %), wherein the oxidizers can be KMnO 4 , HClO 4 , V 2 O 5 , KClO 3 .
• the present invention is therefore based on the problem that it has not been possible to date to achieve metallization of articles made from electrically nonconductive plastic in an environmentally safe manner with sufficient process reliability and adhesion strength of the metal layers applied subsequently.
• etching preferably is performed at room temperature (15-28° C., preferred 20-25° C.), but can also be at higher temperatures of up to 40° C. or 50° C. provided the stability of the solution is controlled.
• the pretreatment solution can optionally contain up to 20 g/l of another oxidizer, with the standard oxidising potential exceeding that of the chlorate.
• the etching time varies with the substrate material and its shape and can be determined by routine experiments. Generally, it varies between 1 and 20 minutes, preferred not longer than 10 minutes.
• the source of chlorate ions can be any water soluble salt. Most commonly used are sodium and potassium chlorate.
• the concentration of the chlorate ions in the etching solution ranges between 0.0016 mol/l and up to 0.12 mol/l, or preferably up to 0.03 mol/l or even more preferred up to 0.04 mol/l. Preferred ranges vary between 0.003 mol/l and 0.08 mol/l or between 0.01 mol/l and 0.06 mol/l or 0.004 mol/l and 0.04 mol/l.
• the concentration of the sulfuric acid ranges between 50 and 80 vol. %, preferably between 55 and 70 vol. % and even more preferred between 60 and 65 vol. %.
• phosphoric acid as an additional acid can be comprised in the etching solution.
• concentration of the phosphoric acid typically ranges from 10 to 40 vol. %, preferably between 15 and 25 or 30 vol. %.
• the adhesion of the plated metal layer can surprisingly additionally be increased.
• a mixture of between 60 and 65 vol. %. sulphuric acid and 20 and 30 vol. % phosphoric acid is particularly preferred.
• the method of pretreatment of the plastics surface prior to their electroless metallization comprising of the etching of the plastic in an inorganic acid solution with an added oxidizer, the activation in the palladium salt solution, and the treatment in either reducing or accelerating solution, characterised in the etching of the plastic surface by the solution of 0.02-15.0 g/l soluble chlorate (e.g. 0.5-5 g/l soluble chlorate) in 50-80% v/v sulphuric acid at room temperature and in additional treatment, prior to the activation by means of the palladium compound solution and the treatment with a reducing/accelerating solution, in the alkali metal hydroxide solution.
• 0.02-15.0 g/l soluble chlorate e.g. 0.5-5 g/l soluble chlorate
• the etching solution can optionally contain 2 to 20 g/l of additional oxidizer, with the standard oxidising potential exceeding that of the chlorate ions.
• the alkali metal chlorate and sulfuric acid form a yellow compound, the normal oxidising potential of which in the H 2 SO 4 solution medium is sufficient for the reaction with the plastic surface at room temperature. Due to this reaction, the plastic surface becomes hydrophilic and adsorbs the palladium compounds with sufficient strength.
• the yellow colour product of the reaction between chlorate and the sulfuric acid is a poison for palladium catalyst. During etching, it penetrates the surface layers of the rack's plastisol insulation and prevents electroless metal deposition on plastisol in the electroless metallisation solutions; the metallization process taking place on the nonconductive plastic surface is not affected.
• etching properties are retained, at room temperature, for several days and the solution may be used without adjustments. In case if only sodium/potassium chlorate is contained in the solution, the etching properties remain for a much shorter period (up to 24 hours).
• a second strong oxidizer e.g., NaBiO 3
• the etching solution can be prepared as follows:
• the water content of the solution preferably should not exceed 50% by volume.
• the etching process takes longer than 15 min., therefore, such concentration is not acceptable.
• Articles in the context of this invention are understood to mean articles which have been manufactured from at least one electrically nonconductive plastic or which have been covered with at least one layer of at least one electrically nonconductive plastic.
• the articles thus have surfaces of at least one electrically nonconductive plastic.
• Plastic surfaces are understood in the context of this invention to mean these said surfaces of the articles.
• process steps of the present invention are performed in the sequence specified, but not necessarily in immediate succession. It is possible for further process steps and additionally rinse steps in each case, preferably with water, to be performed between the steps.
• the plastic surfaces have been manufactured from at least one electrically nonconductive plastic.
• the at least one electrically nonconductive plastic is selected from the group comprising an acrylonitrile-butadiene-styrene copolymer (ABS copolymer), a polyamide (PA), a polycarbonate (PC) and a mixture of an ABS copolymer with at least one further polymer.
• the electrically nonconductive plastic is an ABS copolymer or a mixture of an ABS copolymer with at least one further polymer.
• the at least one further polymer is more preferably polycarbonate (PC), which means that particular preference is given to ABS/PC mixtures.
• the inventive etching solution preferably does not contain any chromium or chromium compounds; the etching solution contains neither chromium(III) ions nor chromium(VI) ions.
• the inventive etching solution is thus free of chromium or chromium compounds; the etching solution is free of chromium(III) ions and chromium(VI) ions.
• the further process step A i) is also referred to as neutralizing treatment.
• Any source of alkalinity can be used, an aqueous solution of sodium hydroxide is a preferred.
• the further process step A i) is also referred to as reduction treatment.
• This reduction treatment reduces chlorate ions and optionally a second oxidizing agent adhering to the plastic surfaces and facilitates removal of such ions.
• the reducing agent is for example selected from the group comprising hydroxylammonium sulphate, hydroxylammonium chloride and hydrogen peroxide.
• the process of the present invention further comprises process step B), in which a plastic surface is treated with a solution of a metal colloid or of a compound of a metal.
• the metal of the metal colloid or of the metal compound is selected from the group comprising the metals of transition group I of the Periodic Table of the Elements (PTE) and transition group VIII of the PTE.
• the metal of transition group VIII of the PTE is selected from the group comprising palladium, platinum, iridium, rhodium and a mixture of two or more of these metals.
• the metal of transition group I of the PTE is selected from the group comprising gold, silver and a mixture of these metals.
• a preferred metal in the metal colloid is palladium.
• the metal colloid is stabilized with the protective colloid.
• the protective colloid is selected from the group comprising metallic protective colloids, organic protective colloids and other protective colloids.
• metallic protective colloid preference is given to tin ions.
• the organic protective colloid is selected from the group comprising polyvinyl alcohol, polyvinylpyrrolidone and gelatine, preferably polyvinyl alcohol.
• the solution of the metal colloid in process step B) is an activator solution with a palladium/tin colloid.
• This colloid solution is obtained from a palladium salt, a tin(II) salt and an inorganic acid.
• a preferred palladium salt is palladium chloride.
• a preferred tin(II) salt is tin(II) chloride.
• the inorganic acid may consist in hydrochloric acid or sulfuric acid, preferably hydrochloric acid.
• the colloid solution forms through reduction of the palladium chloride to palladium with the aid of the tin(II) chloride.
• the conversion of the palladium chloride to the colloid is complete; therefore, the colloid solution no longer contains any palladium chloride.
• the concentration of palladium is 5 mg/l-100 mg/l, preferably 20 mg/l-50 mg/l and more preferably 30 mg/l-45 mg/l, based on Pd 2+ .
• the concentration of tin(II) chloride is 0.5 g/l-10 g/l, preferably 1 g/l-5 g/l and more preferably 2 g/l-4 g/l, based on Sn 2+ .
• the concentration of hydrochloric acid is 100 ml/l-300 ml/l (37% by weight of HCl).
• a palladium/tin colloid solution additionally comprises tin(IV) ions which form through oxidation of the tin(II) ions.
• the temperature of the colloid solution during process step B) is 20° C.-50° C. and preferably 35° C.-45° C.
• the treatment time with the activator solution is 0.5 min-10 min, preferably 2 min-5 min and more preferably 3 min-5 min.
• the solution of a compound of a metal is used in place of the metal colloid.
• the solution of a metal compound used is a solution comprising an acid and a metal salt.
• the metal in the metal salt consists in one or more of the above-listed metals of transition groups I and VIII of the PTE.
• the metal salt may be a palladium salt, preferably palladium chloride, palladium sulphate or palladium acetate, or a silver salt, preferably silver acetate.
• the acid is preferably hydrochloric acid.
• it is also possible to use a metal complex for example a palladium complex salt, such as a salt of a palladium-aminopyridine complex.
• the metal compound in process step B) is present in a concentration of 40 mg/l to 80 mg/l, based on the metal.
• the solution of the metal compound can be employed at a temperature of 25° C. to 70° C., preferably at 25° C.
• the treatment time with the solution of a metal compound is 0.5 min-10 min, preferably 2 min-6 min and more preferably 3 min-5 min.
• process step A ii) is more preferably performed between the protection of the racks and process step B).
• the treatment of the plastic surfaces in process step A ii) is also referred to as preceding dipping, and the aqueous acidic solution used as a preceding dipping solution.
• the preceding dipping solution has the same composition as the colloid solution in process step B), without the presence of the metal in the colloid and the protective colloid thereof.
• the preceding dipping solution in the case of use of a palladium/tin colloid solution in process step B), comprises exclusively hydrochloric acid if the colloid solution likewise comprises hydrochloric acid.
• brief immersion into the preceding dipping solution at ambient temperature is sufficient. Without rinsing the plastic surfaces, they are treated further directly with the colloid solution of process step B) after the treatment in the preceding dipping solution.
• Process step A ii) is preferably performed when process step B) involves the treatment of a plastic surface with a solution of a metal colloid.
• Process step A ii) can also be performed when process step B) involves the treatment of a plastic surface with a solution of a compound of a metal.
• the embodiment is shown schematically in Table 1.
• the plastic surfaces are treated in process step B i) with an accelerator solution in order to remove constituents of the colloid in the colloid solution, for example a protective colloid, from the plastic surfaces.
• the accelerator solution used is preferably an aqueous solution of an acid.
• the acid is selected, for example, from the group comprising sulfuric acid, hydrochloric acid, citric acid and tetrafluoroboric acid.
• the accelerator solution helps to remove the tin compounds which served as the protective colloid.
• a reductor treatment is performed when, in process step B), a solution of a metal compound has been used in place of a metal colloid for the activation.
• the reductor solution used for this purpose then comprises, if the solution of the metal compound was a hydrochloric acid solution of palladium chloride or an acidic solution of a silver salt, hydrochloric acid and tin(II) chloride.
• the reductor solution may also comprise another reducing agent, such as NaH 2 PO 2 or else a borane or borohydride, such as an alkali metal borane or alkaline earth metal borane or dimethylaminoborane. Preference is given to using NaH 2 PO 2 in the reductor solution.
• the plastic surfaces can first be rinsed.
• Process step B i) and optionally one or more rinse steps are followed by process step B ii) in which the plastic surfaces are metallized electrolessly.
• Electroless nickel-plating is accomplished, for example, using a conventional nickel bath which comprises, inter alia, nickel sulphate, a hypophosphite, for example sodium hypophosphite, as a reducing agent, and also organic complexing agents and pH adjusters (for example a buffer).
• the reducing agent used may likewise be dimethylaminoborane or a mixture of hypophosphite and dimethylaminoborane.
• an electroless copper bath for electroless copper-plating typically comprising a copper salt, for example copper sulphate or copper hypophosphite, and also a reducing agent, such as formaldehyde or a hypophosphite salt, for example an alkali metal or ammonium salt, or hypophosphorous acid, and additionally one or more complexing agents such as tartaric acid, and also a pH adjuster such as sodium hydroxide.
• a copper salt for example copper sulphate or copper hypophosphite
• a reducing agent such as formaldehyde or a hypophosphite salt, for example an alkali metal or ammonium salt, or hypophosphorous acid
• complexing agents such as tartaric acid
• a pH adjuster such as sodium hydroxide
• the surface thus rendered conductive can subsequently be electrolytically further metallized in order to obtain a functional or decorative surface.
• Step C) of the process according to the invention is the metallization of the plastic surface with a metallization solution.
• the metallization in process step C) can be effected electrolytically.
• electrolytic metallization it is possible to use any desired metal deposition baths, for example for deposition of nickel, copper, silver, gold, tin, zinc, iron, lead or alloys thereof.
• deposition baths are familiar to those skilled in the art.
• a Watts nickel bath is typically used as a bright nickel bath, this comprising nickel sulphate, nickel chloride and boric acid, and also saccharine as an additive.
• composition used as a bright copper bath is one comprising copper sulphate, sulfuric acid, sodium chloride and organic sulphur compounds in which the sulphur is in a low oxidation state, for example organic sulphides or disulphides, as additives.
• the effect of the metallization of the plastic surface in process step C) is that the plastic surface is coated with metal, the metal being selected from the above-listed metals for the deposition baths.
• the adhesion strength between metal and plastic substrate increases in the first period after the application of the metal layer. At room temperature, this process is complete after about three days. This can be accelerated considerably by storage at elevated temperature. The process is complete after about one hour at 80° C. It is assumed that the initially low adhesion strength is caused by a thin water layer which lies at the boundary between metal and nonconductive substrate and hinders the formation of electrostatic forces.
• the process according to the invention thus enables, with good process reliability and excellent adhesion strength of the subsequently applied metal layers, achievement of metallization of electrically nonconductive plastic surfaces of articles.
• the adhesion strengths achieved are also well above those obtainable according to the prior art after etching of plastic surfaces with chromosulfuric acid (see Examples 2 and 3).
• adhesion values of more than 0.8 N/mm are required for industrial applications and non-complex shaped objects are to be plated.
• planar plastic surfaces are metallized with high adhesion strength by the process according to the invention; instead, inhomogeneously shaped plastic surfaces, for example shower heads, are also provided with a homogeneous and strongly adhered metal coating.
• the treatment of the plastic surfaces by the process according to the invention is preferably performed in a conventional dipping process, by dipping the articles successively into solutions in vessels, in which the respective treatment takes place.
• the articles may be dipped into the solutions either fastened to racks or accommodated in drums. Fastening to racks is preferred.
• the articles can also be treated in what are called conveyor plants, by lying, for example, on trays and being conveyed continuously through the plants in horizontal direction.
• ABS acrylonitrile-butadiene-styrene copolymer
• PC/ABS a mixture of 45% of polycarbonate and 55% of acrylonitrile butadiene styrene copolymer
• ABS acrylonitrile-butadiene-styrene copolymer
• PC/ABS a mixture of 45% of polycarbonate and 55% of acrylonitrile butadiene styrene copolymer
• the plastics Upon etching, the plastics are immersed for 1 to 2 min. in a neutralizing solution of room temperature containing 10 g/l NaOH, followed by the activation in the real (5 min. at 20° C.) or colloidal (2 min. at 35° C.) solution of palladium compounds (colloidal solution is proprietary solution of The DOW Chemical Company (“DOW”)).
• the PdCl 2 concentration in the real solution is 0.1 g/l
• the solution pH is 2.7.
• the plastics Upon activation in the real Pd solution the plastics are held during 5 min. in a solution containing 20 g/l of sodium hypophosphite, pH 9, at 60° C.
• the proprietary colloidal solution the plastics are treated, during 2 min.
• the plastics are nickel-plated using DOW's Niposit-PM nickel-plating process.
• the coating quality is evaluated based on factors such as the plastic surface plated completely/non-completely, the plastisol insulated rack plated or not plated and the adhesion strength of electroless nickel with plastic.
• the Ni plating is thickened in a galvanic copper bath and the strength necessary to peel a 1 cm wide strip off the plastic is measured (kg/cm).
• the etching time in the permanganate solution was 5 min., for the PC/ABS test pieces 15 min.
• the time of etching in the chlorate solution was 5 min. for all the pieces.
• the conditions of the plastics pretreatment for the metallization and the results of the metallization are presented in the Table 2 below.
• Test Pieces 1 to 4 show that, in the case of permanganate-based etching, the rack's plastisol insulation is partially coated with electroless nickel, whereas in the case of chlorate-based etching the insulation remains clean. Furthermore, the values of adhesion between the Ni coating and ABS are considerably higher in the case of the chlorate etching for both ionic and colloidal activating solutions.
• the plastic is either not coated by electroless nickel at all or is coated incompletely (Test Piece 13).
• the H 2 SO 4 concentration is higher than 80% v/v (Test Piece 14)
• over-etching of the plastic occurs and the adhesion between the chemical nickel coating and the plastic is insufficient.
• a disc of ABS plastic (Novodur P2MC, from Ineos) round shape substrate having a diameter of 7 cm was fastened to a stainless steel wire.
• the substrate was then dipped in various pretreatment etching solutions according to the invention as specified in the Table 4 for 4 minutes at a temperature of 22° C. (process sequence is shown in Table 3). Subsequently, the substrate was rinsed under running water for about one minute.
• process step A ii After subsequent rinsing, neutraliazion (process step A i)) and brief dipping into a solution of 300 ml/l 36% hydrochloric acid (process step A ii)), the substrate was activated in a colloidal activator based on a palladium colloid (Adhemax Aktivator NA from Atotech, 100 ppm of palladium) at 40° C. for three minutes (process step B)).
• Adhemax Aktivator NA from Atotech, 100 ppm of palladium
• the protective shells of the palladium particles were removed at 40° C. for three minutes (Adhemax ACC1 accelerator from Atotech, process step B i)).
• the substrate was subsequently nickel-plated at 45° C. without external current for ten minutes (Adhemax LFS, from Atotech, process step B ii)), rinsed and copper-plated at 3.5 A/dm 2 at room temperature for 70 minutes (Cupracid HT, from Atotech, process step C)).
• the panel was stored at 70° C. for 60 minutes (process step C i)).

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