From: NAME: WILLIAM G KENYON FUNC: Chemicals/Electronics TEL: 302-652-4272 <KENYONWG AT A1 AT ESVAX> To: NAME: [log in to unmask] <"[log in to unmask]"@ESDS01@MRGATE@ESVAX> Many of us would be interested to know how you made your ionic contamination measurements; what instrument, what test solution, what test time etc. Northern Telecom had determined that the low ionic results often obtained with water washing of water soluble fluxes were in fact due to the slow "release rate" of such residues from the PWA surfaces. They determined that 90+% of rosin flux residue was released into the 75/25 (v/v) test solution within 15 minutes, but that it took almost 120 minutes to achieve the same level of extraction of flux residues from water solubles. Thus the PWA's soldered with water soluble flux "appeared" to be cleaner than the traditional rosin flux--- when a 15 minute test time was used. You might wish to run a follow-up experiment to determine the release rate of your water soluble fluxes and pastes vs. ionic test time to check this point out and assure yourself that the low ionic readings are indicative of clean PWAs. W. G. Kenyon