1116 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



the completed conductor. In the course of the complete travel thru the 

 machine the wire receives thirty-two separate treatments in nine differ- 

 ent chemical solutions. 



The first solution that the wire enters is the alkali cleaner which re- 

 moves oil, drawing compound and dirt. The heated bath contains an 

 alkaline solution with a small quantity of a wetting agent. This section 

 of the machine contains eight stainless steel cells alternated with seven 

 stainless steel contact rolls mounted in a stainless steel trough. The wire 

 is anodic with the body of the cells acting as the cathode. A current 

 density of 100 amps./sq. ft. is applied to the wires causing a heavy 

 ebullition of gas which materially helps the cleaning operation. The 

 alkali cleaner section is followed by a steam wiper. 



Next the wire passes into a sulfuric acid pickle section where scale, 

 rust and occlusions are removed and a slight etch is imparted to the 

 surface of the steel to promote adhesion with the subsequent copper 

 deposit. A small quantity of an inhibitor is added to prevent the dis- 

 solving of an excess amount of iron which would result in a heavy carbon 

 smut on the surface of the conductur. There are six cells and three monel 

 metal contact rolls. Following the pickle is an air wiper, a water wash 

 cell and a steam wiper. This completes the cleaning and preparation of 

 the wire surface prior to the first plating operation. The tank and cells 

 in the sulfuric acid are constructed of Koroseal lined mild steel. 



The initial coating is a thin layer of copper from a copper cyanide 

 solution termed a "cyanide flash" and is designed to give a smooth 

 deposit. There are five plating cells and four contact rolls of low carbon 

 steel and the machine trough is likewise of low carbon steel. The wire is 

 cathodic and the copper is deposited at a relatively low current density. 



Following the copper cyanide flash the wire passes directly to the 

 copper cyanide plate solution where a copper coating of not less than 

 0.0001" thickness is applied in a bath designed to operate at a high cur- 

 rent density and, therefore, at a higher rate of deposition than is ob- 

 tained in the flash bath. Seventeen plating cells alternated with sixteen 

 contact rolls are needed to deposit the required thickness at the operat- 

 ing current density. Cells, rolls and troughs are made of low carbon 

 steel, and copper shot resting directly on the steel cell bottoms forms the 

 anode surface. The cyanide plate section is followed by a dragout recov- 

 ery unit, a water wash cell and a steam wiper. This completes the prepa- 

 ration leg of the machine. 



When the wire leaves the preparation leg, it passes through a turning 

 section (Fig. 6) which reverses the direction of travel prior to entering 

 the acid copper plate leg where the bulk of the copper is deposited. 



