Yea, I'm not sure if different pastes use different alcohols. I've done a little experimenting though and found that non-water-soluble flux is best dissolved in reagent grade 2-propanol (sorry I said 3 before). It seems lower grades of isopropanol make it clump, probably due to maybe water in it or some denaturing agent. I tried acetone and methanol because they were available more than isopropanol but kept getting the clumping action, or separation between alcohol and flux. Matt On Jun 12, 2008, at 1:20 PM, wrote: > I have wondered about using chemicals to restore older paste to > usefulness. When I commented about using the ultrasonic to extend > the shelf life of solder paste...I should have stated that I stored > the paste in an airtight container in the refrigerator. When I > opened the container each time, I could smell the strong odor of > alcohol, I thought it was isopropanol but was never sure and never > checked the MSDS. > > Perhaps the sealed container prevented or minimized the loss of some > of the chemicals in the flux. > > I've also heard ultrasonics can damage or weaken the bonding wires > in ic's and transistors. But, I've never had a failure in anything > I've built-as far as I can tell, there is no damage to the bonding > wires. I built a keyer for the shack years ago, it was one of the > first projects I used the ultrasonic for cleaning flux with. I have > ultrasonic'd that board for 10 hours (intentionally) just as a test, > and it has worked fine (for years)-in fact, I use the keyer almost > daily and take it to contests too. > > Enjoy. > > Art > > > >> From: Matthew Bajor >> Date: 2008/06/12 Thu AM 11:52:51 CDT >> To: "Microcontroller discussion list - Public." >> Subject: Re: Re: [BUY] Solder paste in a syringe > >> I worked a few summers ago at an aerospace contractor doing alot of >> SMT >> work. If I needed to touch something up, I used 3-Propanol to thin >> out the >> flux and sometimes the paste. For really fine work, I would thin >> the flux >> with the propanol, but mix it in with a little solder paste. The >> heating >> action is imparted better on the solder balls of the paste, almost >> negating >> what would be a sort of surface tension. I've never heard of the >> ultra-sonic >> method but I'm guessing it could work in the short term. >> >> Matt Bajor >> >> On Thu, Jun 12, 2008 at 4:11 AM, Alan B. Pearce >> wrote: >> >>>> I throw my completed and tested new boards straight into the >>>> ultrasonic bath, with plain water. I usually leave then there for >>>> 30 >>>> seconds. >>>> >>>> It removes any and all flux, even the flux left residue >>>> underneath the >>>> chips (on smt packages). It works great to remove the flus, even if >>>> the flux is not the water soluble type. >>>> >>>> It sure beats the heck out of drowning the board with toxic and >>>> expensive flux remover::> >>> >>> However ultrasonic baths are also a known destroyer of chips. What >>> appears >>> to happen is that the ultrasonic vibration seems to shake bond >>> wires off >>> chips. >>> >>> I know that ultrasonic cleaning is banned for anything we fly in >>> space >>> because of known problems induced by ultrasonic cleaning. >>> >>> -- >>> 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 > > -- > 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