Treatment for Electroplating Racks to Avoid Rack Metallization

Abstract

An electroplating rack for supporting non-conductive substrates during an electrodeposition process is described. The electroplating rack is coated with a non-conductive material, such as a PVC plastisol. The electroplating rack is treated with a non-aqueous solution comprising a metallization inhibitor prior to the electrodeposition process to inhibit rack plate up when using etchants that do not contain chromic acid.

What is claimed is: 
     
         1 . An electroplating rack for supporting non-conductive substrates during a plating 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.   
     
     
         2 . The electroplating rack according to  claim 1 , wherein the electroplating rack is at least partially coated with a PVC plastisol. 
     
     
         3 . The electroplating rack according to  claim 1 , wherein the metallization inhibitor is at least substantially insoluble in aqueous media. 
     
     
         4 . The electroplating rack according to  claim 3 , wherein the metallization inhibitor is an organic compound comprising sulfur in a −2 valency. 
     
     
         5 . The electroplating rack according to  claim 3 , wherein the metallization inhibitor comprises a transition metal salt of a di-substituted dithiocarbamate or a tetra-substituted thiuram sulfide. 
     
     
         6 . The electroplating rack according to  claim 5 , wherein the metallization inhibitor is selected from the group consisting of zinc dimethyl-dithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc pentamethylenedithiocarbamate, tellurium diethyldithiocarbamate, nickel dibutyl dithiocarbamate, nickel dimethyldithiocarbamate, zinc diisononyldithiocarbamate, tetrabenzylthiuram disulfide, mercaptobenzothiazole, mercaptothiazo line, mercaptobenzimidazole, mercaptoimidazole, mercaptobenzoxazole, mercaptothiazole, mercaptotriazole, dithiocyanuric acid, trithiocyanuric acid, and combinations of one or more of the foregoing. 
     
     
         7 . The electroplating rack according to  claim 6 , wherein the metallization inhibitor comprises nickel dibutyl dithiocarbamate or tetrabenzylthiuram disulfide. 
     
     
         8 . The electroplating rack according to  claim 1 , wherein the non-aqueous solution comprises a non-aqueous solvent, wherein the non-aqueous solvent is non-volatile and is capable of dissolving an effective amount of the metallization inhibitor. 
     
     
         9 . The electroplating rack according to  claim 8 , wherein the non-aqueous solvent is selected from the group consisting of butylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, propyl lactate, gammabutyrolactone, 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, is propyleneglycol monopropyl ether acetate, propyleneglycol monobutyl ether acetate, dipropyleneglycol monomethyl ether acetate, dipropyleneglycol monoethyl ether acetate, glycol diacetate, and combinations of one or more of the foregoing. 
     
     
         10 . The electroplating rack according to  claim 9 , wherein the non-aqueous solvent comprises ethyl 3-ethoxypropionate, n-propyl lactate, gamma-butyrolactone, or combinations of one or more of the foregoing. 
     
     
         11 . A method of treating an electroplating rack used for supporting non-conductive substrates during a plating process, wherein the electroplating rack is at least partially coated with with PVC plastisol, the method comprising:
 a) contacting the electroplating rack with a non-aqueous solution comprising a metallization inhibitor;   b) mounting non-conductive substrates to the electroplating rack that has been contacted with the non-aqueous solution comprising a metallizaton inhibitor; and   c) etching the non-conductive substrates supported on the electroplating rack with an etchant that does not contain chromic acid.   
     
     
         12 . (canceled) 
     
     
         13 . The method according to  claim 11 , wherein the electroplating rack is contacted with the non-aqueous solution by immersing the electroplating rack in the non-aqueous solution. 
     
     
         14 . The method according to  claim 11 , wherein the metallization inhibitor is at least substantially insoluble in aqueous media. 
     
     
         15 . The method according to  claim 14 , wherein the metallization inhibitor is an organic compound comprising sulfur in a −2 valency. 
     
     
         16 . The method according to  claim 14 , wherein the metallization inhibitor comprises a transition metal salt of a di-substituted dithiocarbamate or a tetra-substituted thiuram sulfide. 
     
     
         17 . The method according to  claim 16 , wherein the metallization inhibitor is selected from the group consisting of zinc dimethyl-dithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc pentamethylenedithiocarbamate, tellurium diethyldithiocarbamate, nickel dibutyl dithiocarbamate, nickel dimethyldithiocarbamate, zinc diisononyldithiocarbamate, tetrabenzylthiuram disulfide, mercaptobenzothiazole, mercaptothiazoline, mercaptobenzimidazole, mercaptoimidazole, mercaptobenzoxazole, mercaptothiazole, mercaptotriazole, dithiocyanuric acid, trithiocyanuric acid, and combinations of one or more of the foregoing. 
     
     
         18 . The method according to  claim 17 , wherein the metallization inhibitor comprises nickel dibutyl dithiocarbamate or tetrabenzylthiuram disulfide. 
     
     
         19 . The method according to  claim 11 , wherein the non-aqueous solution comprises a non-aqueous solvent, wherein the non-aqueous solvent is non-volatile and is capable of dissolving an effective amount of the metallization inhibitor. 
     
     
         20 . The method according to  claim 19 , wherein the non-aqueous solvent is selected from the group consisting of 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 acetate, glycol diacetate, and combinations of one or more of the foregoing. 
     
     
         21 . The method according to  claim 20 , wherein the non-aqueous solvent comprises ethyl 3-ethoxypropionate, n-propyl lactate, gamma-butyrolactone, or combinations of one or more of the foregoing. 
     
     
         22 . The method according to  claim 11 , wherein the non-aqueous solution comprises about 5 g/L to about 40 g/L of the metallization inhibitor. 
     
     
         23 . The method according to  claim 22 , wherein the non-aqueous solution comprises about 10 g/L to about 25 g/L of the metallization inhibitor. 
     
     
         24 . The method according to  claim 23 , wherein the non-aqueous solution comprises about 15 g/L to about 20 g/L of the metallization inhibitor. 
     
     
         25 . The method according to  claim 13 , wherein the non-aqueous solution is maintained at a temperature of between about 25° C. and about 75° C. during the time that the electroplating rack is immersed in the non-aqueous solution. 
     
     
         26 . The method according to  claim 25 , wherein the non-aqueous solution is maintained at a temperature of between about 35° C. and about 65° C. during the time that the electroplating rack is immersed in the non-aqueous solution. 
     
     
         27 . The method according to  claim 13 , wherein the electroplating rack is immersed in the non-aqueous solution for between about 1 minute and about 60 minutes. 
     
     
         28 . The method according to  claim 27 , wherein the electroplating rack is immersed in the non-aqueous solution for between about 2 minute and about 30 minutes. 
     
     
         29 . (canceled) 
     
     
         30 . The method according to  claim 11 , further comprising the steps of:
 a) activating the surface of the non-conductive substrates by immersing the electroplating rack with the non-conductive substrates mounted thereon into a solution comprising colloidal palladium/tin or ionic palladium;   b) immersing the electroplating rack containing the etched and activated non-conductive substrates mounted thereon in an electroless metallization bath to electrolessly deposit metal thereon; and   c) electroplating the non-conductive substrates to plate metal thereon,   
       wherein the treated coated portion of electroplating rack remains free of the electrolessly deposited metal.