Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/06—Suspending or supporting devices for articles to be coated
  • C25D17/08—Supporting racks, i.e. not for suspending
• • 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
  • C23C18/1619—Apparatus for electroless plating
  • C23C18/1628—Specific elements or parts of the apparatus
  • C23C18/163—Supporting devices for articles to be coated

Definitions

• the present invention relates generally to a method of treating electroplating racks used for supporting non-conductive substrates during a metallization step.
• the process involves the steps of: 1) Etching the plastic in a suitable etching solution such that the surface of the plastic becomes roughened and wetted so that the subsequently applied deposit has good adhesion;
• ABS ABS
• ABS/PC ABS blended with polycarbonate
• ABS comprises a relatively hard matrix of acrylonitrile/styrene copolymer and the butadiene polymerizes to form a separate phase. It is this softer phase of polybutadiene (which contains double bonds in the polymer backbone) which may be readily etched using various techniques. Traditionally, the etching has been earned out using a mixture of chromic and sulfuric acids operated at elevated temperature.
• the chromic acid is capable of dissolving the polybutadiene phase of the ABS by oxidation of the double bonds in the backbone of the polybutadiene polymer, which has proven to be reliable and effective over a wide range of ABS and ABS/PC plastics.
• the use of chromic acid has become increasingly regulated because of its toxicity and carcinogenic nature. For this reason, there has been considerable research into other means of etching ABS plastics and a number of approaches have been suggested to achieve this.
• acidic permanganate is capable of oxidizing the double bonds in the polybutadiene. Chain scission can then be achieved by further oxidation with periodate ions.
• Ozone is also capable of oxidizing polybutadiene. However, ozone is extremely dangerous to use and highly toxic.
• sulfur trioxide can be used to etch ABS, but this has not been successfully achieved on a typical plating line.
• Other examples of techniques for etching ABS plastics are described in U.S. Pat. Pub. No. 2005/0199587 to Bengston, U.S. Pat. Pub. No. 2009/0092757to Sakou et al., and U.S. Pat. No. 5,160,600 to Gordhanbai et al., the subject matter of each of which is herein incorporated by reference in its entirety.
• ABS and ABS/PC plastic can be etched in a solution containing manganese(III) ions in strong sulfuric acid as described in U.S. Pat. Pub. No. 2013/0186774 to Pearson et al., the subject matter of which is herein incorporated by reference in its entirety.
• the racks are typically at least partially coated with a non-conductive material to prevent the rack from being entirely covered with metal during the electroplating process, and the most common rack coating is a PVC plastisol.
• the use of chromic acid in the etching stage prior to activation is effective in modifying the surface of the plastisol coating so that it is resistant to metallization after being coated with a palladium activator (usually a colloid of palladium and tin).
• the present invention relates generally to an electroplating rack for supporting non-conductive substrates during an electrodeposition process, wherein the electroplating rack is at least partially coated with a non-conductive material;
• electroplating rack is treated with a non-aqueous solution comprising a metallization inhibitor.
• the present invention relates generally to a method of treating an electroplating rack used for supporting non-conductive substrates during an electrodeposition process, wherein the electroplating rack is at least partially coated with a non-conductive material, the method comprising: contacting the electroplating rack with a non-aqueous solution comprising a metallization inhibitor.
• the present invention allows for the treatment of electroplating racks used for the purpose of supporting non-conductive substrates during a metallization step.
• the method described herein allows for the effective activation of plastics that have been etched without the use of chromic acid while avoiding the common problem of rack "plate up" which occurs when chromic acid free etchants are used for the initial roughening of the plastic.
• the present invention relates generally to the catalysis and subsequent metallization of plastics such as ABS and ABS/PC plastics that have been etched in process solutions that do not contain chromic acid and without problems of "plate up" on at least partially coated racks.
• the method generally comprises the steps of:
• the present invention relates generally to an electroplating rack for supporting non-conductive substrates during an electrodeposition process, wherein the electroplating rack is at least partially coated with a non-conductive material; and wherein the electroplating rack is treated with a non-aqueous solution comprising a metallization inhibitor.
• the electroplating rack is typically coated with a PVC plastisol, or another non-conductive material.
• the non-aqueous solution generally comprises about 5 g/L to about 40 g/L of the metallization inhibitor, more preferably about 15 g/L to about 25 g/L of the metallization inhibitor, and most preferably about 10 g/L to about 20 g/L of the metallization inhibitor.
• the non-aqueous solution is preferably maintained at a temperature of between about
• the electroplating rack is immersed in the non-aqueous solution for a period of time sufficient to treat the PVC plastisol coated rack to avoid rack plate on. That is the electroplating rack is preferably immersed in the non-aqueous solution for between about 1 minute and about 60 minutes, more preferably for between about 2 minute and about 30 minutes.
• the inventors of the present invention have found that metallization inhibitors that are substantially soluble in aqueous media are unsuitable for the process described herein because they tend to slowly leach into subsequent process solutions and prevent metallization of the parts.
• the metallization inhibitor is at least essentially insoluble in aqueous media.
• the solution containing the metallization inhibitor is a non-aqueous solution.
• Suitable water insoluble metallization inhibitors are generally organic compounds comprising sulfur in a -2 valency and include, but are not limited to, transition metal salts of di- substituted dithiocarbamates and tetra-substituted thiuram sulfides.
• Suitable dithiocarbamates include, for example, zinc dimethyl-dithiocarbamate (ZDMC), zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), zinc ethylphenyldithiocarbamate (ZEPC), zinc dibenzyldithiocarbamate (ZBEC), zinc pentamethylenedithiocarbamate (Z5MC), tellurium diethyldithiocarbamate, nickel dibutyl dithiocarbamate, nickel dimethyldithiocarbamate, and zinc diisononyldithiocarbamate.
• ZDMC zinc dimethyl-dithiocarbamate
• ZDEC zinc diethyldithiocarbamate
• ZDBC zinc dibutyldithiocarbamate
• ZBEC zinc ethylphenyldithiocarbamate
• ZBEC zinc pentamethylenedi
• Preferred tetra-substituted thiuram sulfides include, for example, tetrabenzylthiuram disulfide, mercaptobenzothiazoles, mercaptothiazolines, mercaptobenzimidazoles, mercaptoimidazoles, mercaptobenzoxazoles, mercaptothiazole, mercaptotriazole, dithiocyanuric acid, and trithiocyanuric acid.
• the metallization inhibitor comprises nickel dibutyl dithiocarbamate or tetrabenzylthiuram disulfide.
• Suitable non-aqueous solvents include, but are not limited to butylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, propyl lactate, gamma-butyrolactone, ethyl 3-ethoxypropionate and diethyleneglycol monomethyl ether acetate, ethyleneglycol monomethyl ether acetate, ethyleneglycol monoethyl ether acetate, diethyleneglycol monoethyl ether acetate, diethyleneglycol mono-n-butyl ether acetate, propyleneglycol monomethyl ether acetate, propyleneglycol monoethyl ether acetate, propyleneglycol monopropyl ether acetate, propyleneglycol monobutyl ether acetate, dipropyleneglycol monomethyl ether acetate, dipropyleneglycol monoethyl ether a
• the solvent mixture must be capable of dissolving an effective amount of the metallization inhibitor, be readily rinsed off treated racks, and be preferably non-volatile and safe to handle with regards to its toxicology and flammability. In addition, the solvent mixture should cause no damage to the rack coating. It has been found that solvents that are very readily water-soluble can have difficulty in dissolving water-insoluble metallization inhibitors and thus do not give an effective inhibition of metallization. However, substantially water insoluble solvents that readily dissolve the inhibitors and provide a better degree of inhibition can cause a greater degree of attack on the rack coating and are also more problematic to rinse off the rack after treatment. The degree of attack on the rack coating is related to the degree of diffusion of the metallization inhibitor into the surface of the rack coating, and the choice of solvents is therefore critical to the success of the process.
• the metallization inhibitor described herein can be readily applied to racks during the normal treatment cycle to remove unwanted metallic deposits from the tips of the contact points.
• test pieces Subject the test pieces to a reducing stage comprising an aqueous solution of hydroxylamine hydrochloride and hydrochloric acid;
• An ABS test panel and a new PVC plastisol coated test piece were processed through a pretreatment sequence comprising the following stages: 1) Immerse the test pieces in a solvent predip comprising 100 mL/L of propylene carbonate and 50 mL/L of gamma-butyrolactone for 2 minutes at 35°C;
• test pieces Subject the test pieces to a reducing stage comprising an aqueous solution of ascorbic acid
• test pieces were examined.
• the ABS test panel was fully covered in electroless nickel with no apparent voids.
• Subsequent electroplating of this test panel gave full coverage and good adhesion.
• the PVC plastisol coated test piece showed full coverage of the electroless nickel over the entire surface of the plastisol test piece. This would be totally unacceptable in commercial practice.
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The PVC plastisol coated test piece showed significant coverage of the electroless nickel which was observed to cover between 10% and 50% of the surface area. There was no apparent difference observed between the PVC plastisol coated test piece that had been treated in a solvent versus a PVC plastisol coated test piece that had not been treated in a solvent.
• test pieces Subject the test pieces to a reducing stage comprising an aqueous solution of ascorbic acid
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. In addition, the PVC plastisol coated test piece showed no coverage of the electroless nickel.
• An ABS test panel and the treated PVC plastisol coated test piece were processed through stages 1-6 as described in Example 1. Following this treatment, the test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The treated PVC plastisol coated test piece showed no coverage of the electroless nickel.
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The treated PVC plastisol coated test piece showed no coverage of the electroless nickel.
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The treated PVC plastisol coated test piece showed no coverage of the electroless nickel.
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The treated PVC plastisol coated test piece showed no coverage of the electroless nickel despite being a very well used and aged coating with a cracked and roughened surface.
• a new PVC plastisol coated test piece was treated as follows: A. Immerse the plastisol coated test piece in a solution of n-propyl lactate and ethyl 3-ethoxypropionate containing 10 g/L of tetrabenzylthiuram disulfide for 2 minutes at 40°C;
• test pieces were examined. It was found that the ABS test panel was fully covered in electroless nickel with no apparent voids. Subsequent electroplating of this test panel gave full coverage and good adhesion. The treated PVC plastisol coated test piece showed no coverage of the electroless nickel.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemically Coating (AREA)
• Electroplating Methods And Accessories (AREA)

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• 2014
  • 2014-02-19 US US14/184,011 patent/US20150233011A1/en not_active Abandoned
• 2015
  • 2015-01-15 TW TW104101271A patent/TWI623653B/zh active
  • 2015-01-16 CA CA2939316A patent/CA2939316A1/en not_active Abandoned
  • 2015-01-16 EP EP15752252.5A patent/EP3108039A4/de not_active Withdrawn
  • 2015-01-16 WO PCT/US2015/011704 patent/WO2015126544A1/en active Application Filing
  • 2015-01-16 MX MX2016010851A patent/MX2016010851A/es unknown
  • 2015-01-16 JP JP2016552978A patent/JP2017511843A/ja active Pending
  • 2015-01-16 CN CN201580008986.XA patent/CN106103811A/zh active Pending

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