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90 PCB007 MAGAZINE I MARCH 2020 The copper balls in the anode baskets will continue to recede as they are dissolved in the electrolyte, which will require replenishment of copper balls on top of each anode basket. This activity is unsafe and usually requires additional dummy plating to film the newly replenished balls. Dummy plating is also re- quired after prolonged inactivity to release any organic additives that get tied up in the anode. Dummy plating is a non-productive activity that is wasteful. With continuous plating, the anode balls will eventually be reduced in size, particularly at the bottom of the basket. These very small balls would be surrounded by anode sludge, causing the bottom 3–4 inches of the anode basket to become inactive, which has the ef- fect of shortening the total length of the anode. This will have a direct effect on the thickness distribution of the plated copper. The correc- tive action taken is referred to as "anode main- tenance." Anode maintenance, depending on the size of the plating line, could take two or three in- dividuals 3–8 hours. The anodes are removed from the electrolyte, the bag is removed and discarded, and the contents of the basket are poured out. The basket is refilled with new balls as well as some of the larger dumped-out balls. This will leave the smaller balls, which are usually sold as scrap. New balls are bought at a premium. Once the anodes are refilled, they are bagged with new bags. The entire anode maintenance activity is extremely wasteful in labor, scrap copper, and the cost of new bags. The use of insoluble anodes with eductor sparging will eliminate waste in labor and material and will afford a cleaner ambient air environment in the plating area. Insoluble anodes are made of a titanium mesh that is coated with MMO. MMO is a pro- prietary, mixed-metal oxide layer. This anode does not require any maintenance and will perform without any dimensional variation day in and day out for months on end. The in- soluble anodes must be sized and properly lo- cated in the plating tank to give optimum cop- per thickness uniformity. The anodes should be placed evenly across the anode bar. They should also be 3-4" shorter than the panel and must be tucked 3–4 inches inside the cathode plating window. Insoluble anodes require the continuous addition of copper to the electro- lyte; this is accomplished by the controlled ad- dition of copper oxide based on ampere-hours of plating. The use of bottom eductors to replace air sparging will eliminate all acid mist and the need to exhaust the air above the plating tank. Eductor size and location must be designed to ensure adequate and uniform solution replen- ishment at the plating site. With insoluble anodes and eductor sparging, waste in acid copper plating is eliminated as follows: • No variability in anode dimensions • No copper waste; every gram of copper added will be plated on the parts • No anode maintenance or the labor and hazard associated with the activity • No dummy plating required • No polluted air requiring exhaust • No bag replacement This system with insoluble anodes and educ- tor sparging is maintenance-free and non-pol- luting and is presently in use in vertical dip tanks in a couple of large U.S. shops. It is also used extensively in conveyorized acid copper plating equipment. PCB007 George Milad is the national accounts manager for technology at Uyemura. To read past columns or contact Milad, click here. Dummy plating is a non-productive activity that is wasteful.