That make sense for military high reliability requirements. Funny N. Au Group Electronics, http://www.AuElectronics.com http://www.AuElectronics.com/products http://augroups.blogspot.com/ ________________________________ From: MCH To: Microcontroller discussion list - Public. Sent: Sun, February 7, 2010 1:04:56 PM Subject: Re: [TECH]Ultrasonic Cleaning for circuit boards. Maybe it's due to "Stress" on the leads of components? (on the line of: if you bend a lead too often it will break) Maybe the ultrasonics weaken the leads. Joe M. Funny NYPD wrote: >> but I do know that untrasonic cleaning can cause microscopic > pitting on surfaces. > > My understanding is: it only affects and cleans the outside surface (dirts, flux residual, etc.) on circuit board cleaning process, will the wire-bone inside the chip be pill-off too without liquid bubble contact? That's what really confused me. > > Funny N. > Au Group Electronics, http://www.AuElectronics.com > http://www.AuElectronics.com/products > http://augroups.blogspot.com/ > > > > > ________________________________ > From: sergio masci > To: Microcontroller discussion list - Public. > Sent: Sun, February 7, 2010 8:51:51 AM > Subject: Re: [TECH]Ultrasonic Cleaning for circuit boards. > > > > On Sat, 6 Feb 2010, Jonathan Hallameyer wrote: > >> I took a nasa soldering class, same thing 63/37 only, and no ultrasonic >> cleaning for stuffed boards. As far as 63/37 only, the other stuff may be >> alright, but none of it has been used for 100+ years like lead solder. There >> may be finally be coming good alternatives, but for a while, lead free meant >> higher temperatures for soldering. > > It's not so much about temperature as the formation of tin wiskers. It's > easy to make low temp solders without using lead. True they are much more > expensive than standard tin / lead solder. One of the actions of lead in > standard Sn/Pb solder is to inhibit the growth of tin wiskers. These are > tiny little fillaments that grow from the surface of tin. They can cause > trouble in circuits as they are conductive. Look up tin wiskers. > >> I'd say lead free was pushed before good >> alternatives were available, but if it werent pushed, who says they would >> have been developed... So catch .22 there >> >> And you nailed it on the reasoning for the no ultrasonic cleaning. Our >> instructor kept it simple. Some dies are wirebonded using ultrasounds, so >> no ultrasonic cleaning to be extra sure... Though I guess you could say >> some were bonded with just heat, so no heating the leads ;p >> > > I don't know why ultrasonic cleaning is banned from military or NASA > circuits but I do know that untrasonic cleaning can cause microscopic > pitting on surfaces. Maybe there is the risk of pitting of the surface of > the chip buried inside the plastic package. > > Regards > Sergio > > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.733 / Virus Database: 271.1.1/2673 - Release Date: 02/07/10 02:22:00 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist