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22 The PCB Magazine • August 2017 added fume recycling and rinse recycling to the system, and made it a totally closed loop; there's no connection to the scrubber or anything. Holden: Is that etchant made of basic chemicals or is it proprietary? Stepinski: No, we mix it. It came with propri- etary chemicals, and we now use our own for- mulation. We run 75 grams per liter copper and two grams per liter ammonium phosphate, with a pH around 8.6. The galvanic process lib- erates ammonium and oxygen, which we then reintroduce into the system with the V enturi to regenerate it. One of the keys to the system is the etching goes through a cascade mechanism and gets the Venturi action, and it sits through that, it goes through this cascade for about four minutes. In that time, we're able to regenerate all the copper one (Cu + ) to copper two (Cu ++ ), and then return it to the etchant, to the spray bars. We never spray with any copper one; it's al- ways regenerated. The etch rate is much more consistent in this case. We're not doing any re- action in the chamber itself. It's in a hermetical- ly sealed offline tank, and we do not reintroduce the etchant until all the copper one is gone, be- cause the copper one is a poison and changes the etch rate. Our etch rate is always the same. Goldman: You basically have the same bath in there that you've had from the very beginning. But you must have some dragout? Stepinski: No, the dragout is all returned to the etcher. Holden: If you do a mass balance, and you're in- troducing copper from copper foil, you have to take copper out somewhere. Goldman: I was thinking of just a solution dra- gout at the end, but with the rinsing… Stepinski: One of the differences with our system is that with a typical ammonium etch system they run a much higher copper content. This causes other problems; now the solution is at the satura - tion limit. When you introduce a little bit of wa- ter in there, you cause a lot of problems, you start making sludge. The fun thing about our process is we run at a little less than half the normal concen- tration. We've adjusted the other components to balance that. Etch factors are good; we're 5:1 plus for etch factors. Because the salt content is so low—we man- age the total salt content—we say the maximum total salt content is 200 grams/liter. That's every- thing, anions, cations, everything—we can take a water hose and just put it right into the etcher. Our rinses cascade back into the etcher. Holden: Your first rinse is probably the replen- isher, isn't it? Stepinski: No, we just have a cascade rinse. In fact, it doesn't go back into the etcher direct- ly; the rinse cascade goes into a little holding tank, which gets metered into the galvanic cell where we have a very high ammonia content, and that's able to absorb it all. That's how we balance. The air fumes are balanced, the negative pressure that we generate from the Venturi above the solution level, we connected the front of the entry to that. So, we're able to locally remove the fumes from the atmosphere right around the machine. Y ou don't smell any ammonia fumes even though we walked by the etcher and it was fully on, everything was on. You don't really smell any- thing. There's enough suction there just from the Venturi, which isn't even connected, nothing's connected to a fume scrubber. It's just local WHELEN ENGINEERING, TWO YEARS LATER Figure 6: One of seven Whelen-made sirens used to alert employees that a process needs manual attention.