Hello again .. Good morning, **Hi Doug Pauls (thank you very much for your answers) Below you could find one more question that is really important. "Do you please check if the following process can be sufficient to eliminate all the risks which is coming from the use of H type flux; After completing the soldering process; 1. "well done" cleaning with water, 2. visual inspection for detecting the flux residues and checking corrosion and dendritic formation, 3. performing the ionic contamination testing, 4. conformal coating application 5. visual inspection for checking corrosion, dendritic formation and mealing of conformal coating, 6. burn-in testing, 7. vibration testing (at least in the two axises)" Thanks in advance. Tugmen. From: [log in to unmask] [mailto:[log in to unmask]] Sent: Wednesday, August 10, 2005 4:09 PM To: [log in to unmask]; TUGMEN UNSAL (MIKES INTERNET) Subject: Re: [TN] Requirements for soldering fluxes Hello all, **Good morning Could you please assist me to find answer of the questions listed below.? **I'll give it a shot. 1. Why the use of H type flux in the solder paste is not prefered for Class III equipment production? **Because its dangerous, very dangerous. Type H flux is very very active and can go from oxide stripper to corrode the trace open very quickly if you don't know what you are doing. If you have areas where your cleaning process is marginal, you can have corrosive residues which can destroy the assembly. If you are making garage door openers, no big deal. Pacemakers are another issue. 2. Any negative impact recorded at IPC since the use of solder paste with H type flux and so that corrective action taken? **Depends on what you mean by "recorded at IPC". One of the more enjoyable parts of IPC meetings is the "swapping of the war stories" in which us old farts trade horror stories about manufacturing. There are people who have used type H fluxes in Class 3 manufacturing, but the process is very well controlled, tested to the nth degree, and very well monitored. 3. What kind of solder paste is acceptable for DoD requirements and other Class III equipment production? **One that works. One that does not leave harmful residues. Neither DoD nor IPC mandate what kind of flux or paste you can or cannot use on electronic hardware. What they do mandate is that the more aggressive your flux is, the more data you better be able to provide to convince your customer that you know how to control the process, that all of your chosen materials for manufacturing are compatible with each other, that your cleaning processes are very robust, and that any residue left behind will not result in electrochemical failures (dendrites, leakage, corrosion). Class III hardware is classified as such because the consequences of failure are usually catastrophic. If you were making Class III hardware for me, and you were using a low activity flux, I would expect a certain amount of data. If you were making hardware for me using a medium activity flux, I would expect a lot more. If you wanted to use a type H flux, you would have to have a mountain of data and me on site being a pest (shut up Dewey) before I would allow it. 4. What type of water soluable solder paste prefferable for Class III applications? **Same argument as above. 4. Do IPC suggest any specific method to measure the thickness of the solder paste on the PWB before beginning the process? **I have to pass on this one. I can't find anything in J-STD-001 or the handbook on it. I know we use a laser device here to measure paste height. Doug Pauls Rockwell Collins --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------