Process and apparatus for electroplating substrates

Abstract

An apparatus for electroplating one or more surfaces ( 2,3 ) on one or more substrates ( 1 ), especially solar cells ( 1 a ), is described. The apparatus includes an electrochemical coating bath ( 13 ), which has a coating tank ( 12 ) filled with an electrochemical coating liquid ( 14 ). The apparatus also includes a conveying device ( 15 ) for transporting the substrate through the coating bath ( 13 ), a light source circuit ( 60 ) with light sources ( 64 ) for irradiating the substrate ( 1 ) and an electrolytic cell rectifier circuit ( 50 ) for the substrate with anodes ( 54 ). The apparatus is characterized by a device for generating synchronous current pulses and light pulses, so that during a time interval between the current pulses the irradiating of the substrate or substrates is interrupted. A process for electrochemical plating of the surface of the substrate or substrates is also described.

1 . An apparatus for electroplating at least one surface ( 2 , 3 ) of at least one substrate ( 1 ), said apparatus comprising
 an electrochemical coating bath ( 13 ), which has a coating tank ( 12 ) filled with an electrochemical coating liquid ( 14 );   a conveying device ( 15 ) for transporting the at least one substrate through the coating bath;   a light source circuit ( 60 ) with at least one light source ( 64 ) for irradiating the at least one substrate ( 1 );   an electrolytic cell rectifier circuit ( 50 ) for the at least one substrate with anodes ( 54 ); and   means for producing synchronous current pulses and light pulses, so that during a time interval between said current pulses the irradiating with the at least one light source is interrupted.   
     
     
         2 . The apparatus as defined in  claim 1 , wherein the means for producing synchronous current pulses and light pulses comprises at least one pulse generator ( 53 ) in the electrolytic cell rectifier circuit ( 50 ) and/or in the light source circuit ( 60 ). 
     
     
         3 . The apparatus as defined in  claim 2 , wherein said electrolytic cell rectifier circuit ( 50 ) and said light source circuit ( 60 ) are electrically connected to said at least one pulse generator ( 53 ). 
     
     
         4 . The apparatus as defined in  claim 1 , wherein the light source circuit ( 60 ) is coupled with the electrolytic cell rectifier circuit ( 50 ) by an optical coupler ( 56 ). 
     
     
         5 . The apparatus as defined in  claim 1 , wherein the light source circuit ( 60 ) and/or the electrolytic cell rectifier circuit ( 50 ) has at least one control device ( 59 ,  66 ), which controls a light intensity of the at least one light source ( 64 ) and/or amplitudes of the current pulses in accordance with respective widths of the current pulses. 
     
     
         6 . The apparatus as defined in  claim 1 , further comprising means for producing a flow of the electrochemical coating liquid ( 14 ). 
     
     
         7 . The apparatus as defined in  claim 6 , wherein said means for producing the flow of the electrochemical coating liquid ( 14 ) comprises at least one nozzle for conducting the electrochemical coating liquid ( 14 ). 
     
     
         8 . The apparatus as defined in  claim 7 , wherein the at least one nozzle is arranged in the coating bath ( 13 ) opposite to the at least one surface ( 2 , 3 ) of the at least one substrate ( 1 ) to be coated. 
     
     
         9 . The apparatus as defined in  claim 7 , wherein the at least one nozzle in the coating bath ( 13 ) is oriented in a direction perpendicular to the at least one surface ( 2 , 3 ) of the at least one substrate ( 1 ) to be coated. 
     
     
         10 . The apparatus as defined in  claim 7 , wherein the at least one nozzle is arranged between the anodes ( 54 ) of the electrolytic cell rectifier circuit ( 50 ). 
     
     
         11 . The apparatus as defined in  claim 7 , wherein the at least one nozzle is at least one Venturi nozzle ( 46 ). 
     
     
         12 . The apparatus as defined in  claim 6 , wherein said means for producing the flow of the electrochemical bath liquid ( 14 ) comprises a circulating device ( 30 ). 
     
     
         13 . The apparatus as defined in  claim 12 , wherein said circulating device ( 30 ) is a countercurrent flow device. 
     
     
         14 . A process for electroplating at least one surface of at least one substrate, said process comprising the steps of:
 a) moving the at least one substrate through an electrolytic coating liquid;   b) during the moving of the at least one substrate irradiating the at least one substrate with light;   c) during the irradiating applying an electric current to the at least one substrate by means of an electrolytic cell rectifier circuit; and   d) pulsing the electrical current and the light synchronously, so that during a time interval between current pulses the irradiating is interrupted.   
     
     
         15 . The process as defined in  claim 14 , wherein pulse widths of light pulses produced by the pulsing of the light and of the current pulse are each from 0.1 ms to 10,000 ms. 
     
     
         16 . The process as defined in  claim 14 , wherein said time interval between the current pulses is equal to a pulse width of said current pulses. 
     
     
         17 . The process as defined in  claim 15 , wherein the current pulses and the light pulses are rectangular-shaped pulses. 
     
     
         18 . The process as defined in  claim 15 , wherein the light pulses and the current pulses have respective pulse widths and/or respective amplitudes and said respective pulse widths and/or said respective amplitudes are varied during the process. 
     
     
         19 . The process as defined in  claim 15 , wherein the more the amplitudes of the light pulses are reduced, the greater are the pulse widths of the light pulses. 
     
     
         20 . The process as defined in  claim 14 , further comprising applying a direct current (I 1 ) to the at least one substrate during said time interval between the current pulses that is less than or equal to one half of a current (I 2 ) applied during the current pulses. 
     
     
         21 . The process as defined in  claim 14 , wherein the electrochemical bath liquid flows in a direction that is opposite to a conveying direction ( 5 ) of the at least one substrate at least in the vicinity of the at least one surface of the at least one substrate to be coated. 
     
     
         22 . The process as defined in  claim 21 , further comprising a turbulent flow of the electrochemical bath liquid at least in the vicinity of the at least one surface of the at least one substrate to be coated.