In a message dated 99-06-04 18:09:12 EDT, [log in to unmask] writes: << I do not know why the Macdermid 9241 acid copper plating bath needs carbon treatment after a certain amp-hrs. of plating? >> 1. The brightners and grain refiners in acid coppers are organic molecules. There is a continuous breakdown of these additives as electrical current passes through them - more than the drag out of copper plating solution can remove with today's pollution controls. So, the "Total Organic Carbon" builds in the plating bath. At some point, the organics start to interfer with the copper grain structure in the deposits. The tensile and elongation properties fall off and you will get corner cracks in solder shock. Carbon treatment removes (hopefully) all these organics, so that you can start over with a new brightner add, just like on original make-up. 2. The plating resist you are using and the cleaner solution at the start of the pattern plate line are both organics. These are other sources of organic molecules, besides the breakdown products from the plating bath brightner. They also are removed (hopefully) in carbon treatment. You can control an acid copper plating bath by running Hull cells to determine brightner effectiveness -or the effect of the organic impurites, run a total organic carbon frequently to see how much organic is building up, run some sort of chromatograph (ionic, liquid, etc) to see what compound is building up, and run frequent physical property samples of your copper plate. OR, you can use the guidelines we have established based on shop experience around the world, and carbon treat after a specified number of amp hours per gallon of plating bath solution to be safe. Unless you have access to a lot of analytical equipment, better use the amp hour recommendation. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################