Issue link: https://iconnect007.uberflip.com/i/1522641
70 PCB007 MAGAZINE I JUNE 2024 bells and whistles, so to speak, only to visit that plant a year later and find most of them weren't being fully used because they found they didn't need as tight a control as they initially thought. So, just how much expensive control equip- ment do you really need? We will initially focus on the etchers using cupric chloride and alkaline etchants. e etcher is the critical point in the produc- tion process where small changes in chemis- try or equipment parameters can have a sig- nificant effect on line-width specifications and where tighter controls can be of the most ben- efit. e chemistry parameters that need to be monitored (not necessarily in order of impor- tance) are temperature, specific gravity, oxida- tion reduction potential (ORP), free acid for As line and space requirements and speci- fications get increasingly tighter, it is obvious that at some point you must consider tighten- ing the controls on the chemical and equip- ment parameters (temperature, specific grav- ity, conveyor speed, etc.) of your production lines to meet those requirements. For the pur- poses of this discussion, let's consider line and space requirements of 75 µm (0.003") or less with tolerances of ±5% as the tipping point for serious consideration of tighter chemistry and equipment control. ere are optional controls (at extra cost, of course) available from most equipment sup- pliers to tighten up these parameters. On the other hand, I've seen equipment ordered with every conceivable control imaginable, all the Chemical and Equipment Control of High-density Circuits The Chemical Connection Feature Column by Don Ball, CHEMCUT