BHF mixed with most acids, especially strong acids (meaning that they fully dissociate into H+ and the anion), will form some HF (that is, the compound [responsible for etching], not dissociated into H+ and F-). As noted in one of the papers, "the Trilogy etch" forms HF from the ammonium fluoride and nitric acid. Use the appropriate safety precautions for HF. --Kirt Williams -----Original Message----- From: mems-talk-bounces+kirt_williams=sbcglobal.net@memsnet.org [mailto:mems-talk-bounces+kirt_williams=sbcglobal.net@memsnet.org] On Behalf Of Dave Sent: Tuesday, September 24, 2013 9:41 AM To: mems-talk@memsnet.org Subject: Re: [mems-talk] Are there any 'safe' (non-hf) isotropic etches? Are you sure on the NH4F safety? My understanding is that this simply dissociates into HF once it is combined with water. Whenever I use etchants with NH4F or ammonium biflouride I treat them like HF. Dave _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk