Chris: If you search the TechNet archives you'll find quite a bit of information on ionic extraction testing, purpose, application, theory, etc. This should provide you an informational background to draw on. To address your question more specifically, if both types of finishes are done as SMOBC for the ENIG vs. HASL boards: 1. I would expect the ionic contamination levels to be the same prior to soldermask application. 2. I would expect the ionic contamination levels to be the same after soldermask application. However after soldermask is not where you want to do your second check. You want to check after soldermask, the final finish application and cleaning. 3. Based on our experience, after the final finish application and cleaning I would expect the HASL board to be higher in ionics due to the chemistries and thermal exposures involved. Please remember low measurements of the average ionic contamination level of a board does not guarantee it's electrical performance. It is basically an indicator of the process. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Ball Sent: Tuesday, September 12, 2006 12:45 PM To: [log in to unmask] Subject: Re: [TN] bareboard cleanliness related to surface finish The requirement being questioned reads: BARE BOARD CLEANLINESS MUST BE VERIFIED BEFORE AND AFTER APPLICATION OF SOLDER MASK USING AN OMEGA METER 600 SMD OR EQUIVALENT HEATED IONOGRAPH. MAXIMUM CONTAMINATION SHALL NOT EXCEED 0.47ug/cm2 NaCl. Would you expect ENIG to be at 0.6 while HASL was at 0.8, for example? I thought there would be a final cleaning that would cause the end result to be pretty much the same, regardless. As is obvious, I don't really know squat about this sort of thing, and am relying on the kindness of strangers.... (hello Dewy) Thanks, -Chris [log in to unmask] Sent by: TechNet To: [log in to unmask] <[log in to unmask]> cc: Subject: Re: [TN] bareboard cleanliness related to 09/12/2006 02:36 PM surface finish Please respond to TechNet E-Mail Forum; Please respond to Wgkenyon2 You might wish to compare ionics, which might not be much different. However, if you compared non-ionics using TMs 2.3.38 or 2.3.39, you might find quite a difference. 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