John, Gosh, where did you get this info from? Plasma desmear processing uses small amounts of about 3 different, very pure gases (O2, N2 and a fluorocarbon, usually). No other chemicals that I am aware of. The only waste is the small amount of gases that are discharged. The plasma desmear is done under vacuum, hence the small amount of gases used/discharged. It is considered more expensive because there is a larger capital equipment cost, I believe. In the past, uniformity of desmear and etch was a problem. That is no longer much of an issue with the much improved equipment now available. APS in Florida has done much in the development of their equipment (reverse gas flow and circulation, better electrode and panel placement, etc.) to eliminate variability. The process is essentially a batch one and is longer than the other methods (permanganate, sulfuric). On the other hand, it is clean, with minimal waste, and it will work on all material types, even PTFE (different gas required) and flex. Permanganate is great if you have the right set-up: three process tanks and 3 double rinses. There are 3 process steps: solvent clean/swell/sensitize; permanganate (runs hot, needs SS or better tank); neutralizer; each needs a good rinse. The permanganate bath needs to be regenerated, either electrically or chemically, or it will soon fall apart (precipitates MnO2). Works on epoxy and polyimide substrates, but not flex. There are many suppliers of good processes, ask any board manufacturer. Sulfuric acid process requires hot, concentrated sulfuric acid. It is dangerous and messy and works only on standard difunctional epoxy materials. Often produces a substandard desmear (esp. when sulfuric concentration drops slightly). Because of the viscosity of the acid, small, high aspect ratio holes cannot be reliably processed. Not Recommended! Way back when, I worked with plasma in a board shop and it was a bear, but that was 15 years ago with first generation equipment. Those that have the new generation equipment think it is the greatest thing since, well you know. Talk to Advanced Plasma Systems in FL - they know and understand a lot about the process. Ask for customers to talk to, if you need more info. I swore by permanganate for many years (esp. when I was on the supply side) but nowadays, if I were setting things up, I would take a real good look at plasma, the only dry desmear/etchback process for multilayer holes and vias. Patty ---------- From: John_Gulley To: Hound; technet Subject: Re: Plasma Date: Friday, January 24, 1997 6:49PM Gaylor, Not sure where you are hearing that Plasma is good, but past fab shop I've worked for or surveyed from the customer end, have moved away from using plasma. I could be wrong and someone in the forum may correct me, but this has been the underlying trend. Several reasons are: 1. Cost, the dry-chemicals are very expensive. 2. You typically have non-uniform smear removal of the hole wall. 3. Check your local city and state ordinance on chemicals. 4. Expensive equipment. 5. Proper air ventilation in-place If you have low volumes, use sulfuric acid, but have safe and preventive measures in place. For higher volumes, I would highly recommend using Permanganate for smear removal. The advantages outweigh the disadvantages of using this make-up. Once you have your two chemistries mixed, just add DI or replace evaporated water. Regards, John Gulley - QA Inet Inc. Plano, TX 75075-7270 ______________________________ Reply Separator _________________________________ Subject: Plasma Author: [log in to unmask] (Timothy Gaylor) at Internet Date: 1/23/97 11:25 PM I am interested in the Plasma desmear process. I have been reading alot about this type of desmear technique and dont quite understand the variables involved. >From what I understand there is a combination of three gasses that combine to create the "plasma" state ( the most common oxygen, nitrogen and tetraflouromethane). How are these gasses controlled and what effects do the ratio of the gasses effect the etchrate? T.A. Gaylor *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************