Good input! From an historical perspective, Ionograph testing was intended to support rosin base fluxes closely controlled by flux qualification specifications which is certainly not the case today. Given the consistent contamination resource as well as cleaning chemistries the correlation to cleanliness to performance was a valid consideration. Good application for the time and common processes allowed. Today we must rely more heavily upon SIR/MIR types of testing however IC testing resources can add a degree of confidence as it can identify and quantify the contamination type. Unfortunately these tests are not inline process tests as were the quick and simple Ionic tests when life was simpler. Mel Parrish Director, Training Materials Resources Soldering Technology International 102 Tribble Drive Madison, AL 35758 256 705 5530 256 705 5538 Fax [log in to unmask] www.solderingtech.com -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Tegehall Per-Erik Sent: Tuesday, October 01, 2002 1:56 AM To: [log in to unmask] Subject: Re: [TN] Ionograph measurements Even if you could find a method to scientifically measure cleanliness of an assembly (which I doubt will ever happen since flux residues are absorbed into the epoxy resin) you would also need to be able to tell how the concentration of the various contaminants varies over the surface of the assembly in order to assess the impact on reliability. This means that you also must be able to transform contamination levels into reliability figures. You must then know which of the contaminants that are hygroscopic and which are hydrophobic, which are ionic and which are non-ionic, but also which contaminants that cause synergistic effects when mixed. Therefore, I think, a scintific approach for verifying quality ought to focus on methods for assessing the impact on reliability instead of methods for measuring the cleanliness. Surface Insulation Resistance (SIR) measurements is such a method (described in Appendix B in J-STD-001C) but, as it is used today, its scintific base including acceptance criterion is not what it ought to be. Per-Erik -----Ursprungligt meddelande----- Från: [log in to unmask] [mailto:[log in to unmask]] Skickat: den 1 oktober 2002 01:50 Till: TechNet E-Mail Forum.; Tegehall Per-Erik Kopia: [log in to unmask] Ämne: Re: [TN] Ionograph measurements How does one, scientifically, measure cleanliness of an assembly? It's always struck me that if your cleanliness measuring equipment can extract enough salts, etc., to measure something, then your cleaning equipment isn't good enough, and maybe you should be cleaning with your measuring equipment instead. And how to tell that you're not extracting some vital ingredient of the board material and not just surface contaminaton, short of using some SEM and checking out the molecules? Just a thought (or not) (where have I heard that before?) Peter Tegehall Per-Erik <[log in to unmask]> 30/09/2002 10:04 PM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to Tegehall Per-Erik To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: Re: [TN] Ionograph measurements Daan, In a note to section 8.3.6 in I-STD-001C, it is written that "In comparing the sensitivity between methods, the solvent used to extract the residue, the method used to present the solvent to the assembly and the method of detecting the residue should all be considered. " I interpret that as you are allowed to and should do the correction. But if you use correction values, the figures given in the MIL standard are only valid for the models of cleanliness equipment that were used at that time. I guess Alpha Ionograph 500M is a later model, which means that it should have a different correction figure (probably higher since it likely has better cleaning efficiency). However, the use of equivalence factors has no scientific base. But on the other hand, neither has the method for cleanliness measurement. It shouldn´t be used as proof of the cleanliness of an assembly since it is no proof of assembly reliability. It is a good tool for process control, i.e. to control that the cleanliness of assemblies manufactured in certain line does not change with time. In my opinion, its use should be limited to that. Regards Per-Erik ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------