I would add that we've seen similar effects from even from just DI water (that deionized not distilled). High resistivity (>~7 Megohm) water is actually pretty corrosive all by itself. The addition of cleaning solvents acts to further accelerate this problem. We have some photos / SEMs of this that we've presented at IPC and Nepcon. =============================== Jim Maguire Senior Principal Engineer Boeing Defense & Space Group (206)657-9063 fax 657-8903 Email: [log in to unmask] ================================ >---------- >From: ddhillma[SMTP:[log in to unmask]] >Sent: Thursday, March 20, 1997 5:34 AM >To: [log in to unmask] >Cc: [log in to unmask] >Subject: Re: PCB: Solder Joint issue > > Hi Dwight - > > I suggest you investigate your aqueous cleaning solution > concentration. I have seen several cases where Alpha 2110 > saponifier/water solution was not correctly balanced per the product > use instructions. The Alpha 2110 saponifier is very basic (a pH of > 10-11) and it will literally "etch" the solder joints if > saponifier/water solution is not balanced. I have seen several > instances of "blue" solder joints that are really oxidized due to the > cleaning solution etching action. Good Luck. > > Dave Hillman > Rockwell Collins > [log in to unmask] > > >______________________________ Reply Separator >_________________________________ >Subject: PCB: Solder Joint issue >Author: [log in to unmask] at ccmgw1 >Date: 3/20/97 7:08 AM > > > =20 > TechNet: > =20 > During our process of cleaning boards with our aqueous cleaner,=20 > the boards are coming out of the aqueous with a "light bluish" colored= >=20 > tint to the solder joint. This bluish tint can be cleaned off of the=20 > solder joint with alcohol and a brush but returns when aqueous=20 > cleaned. We tried to consider all of the items which might be causing= >=20 > this to occur such as water temperature breaking down the dyes in the=20 > saponifier, varied conveyor speeds on the aqueous, RO water quality,=20 > water pressure, redirection of aqueous nozzles, changing saponifier,=20 > flux solids, etc. =20 > =20 > When this condition was noticed we took several actions to try to= >=20 > pinpoint what was causing this condition. Following are those actions= >=20 > we have performed: > =20 > 1. Draining of the Aqueous machine. > 2. Thorough cleaning of the machine. > 3. Refill of machine with Alpha 2110 saponifier. > 4. New membranes for the RO water system. > 5. Varied conveyor speeds. > 6. Varied water pressure. > 7. Lowered water temperature from 180 to 160. > 8. Redirection of water nozzles. > 9. Changing of solids in our flux from 25% to 15% > 10. Changing to a dyless saponifier by Interflux (Vichem 600A). > 11. Added de-ionizer. > =20 > The solder we use is Sn63Pb37, made by Alpha Metals. It is=20 > tested for impurities every 30 operating days. Solder temperature is=20 > 500 Deg F. The flux we use is Alpha 615-15 for wave soldering and=20 > 615-25 for hand soldering and pretinning. Saponifier is either Alpha=20 > 2110 or Vichem 600A by Interflux. Solution concentrate is 5%. Wash=20 > temperature is 160 Deg. F. Rinse temperature is 180 Deg. F. Length=20 > of wash is 12" and conveyor speeds are from 1 ft/min to almost 3.0=20 > ft/min. final rinse is Reverse Osmosis and de-ionized. > =20 > The initial results of the actions above are that the solder=20 > joints look very shiny compared to using the Alpha 2110 saponifier,=20 > but the light bluish tint still remains. We are now considering that=20 > the blue tint may simply be oxidation of the solder joint caused by=20 > the saponifier and the heat since saponifiers are strong oxidizers. > =20 > Does anyone have any ideas or previous experience with this=20 > condition? Thanks for your time. > =20 > Dwight Nolen > Manufacturing Quality Engineer/QA Supervisor > Frontier Engineering > 405-624-5329 =20 > >*************************************************************************** >* TechNet mail list is provided as a service by IPC using SmartList v3.05 * >*************************************************************************** >* To subscribe/unsubscribe send a message <to: [log in to unmask]> * >* with <subject: subscribe/unsubscribe> and no text in the body. * >*************************************************************************** >* If you are having a problem with the IPC TechNet forum please contact * >* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * >*************************************************************************** > > >*************************************************************************** >* TechNet mail list is provided as a service by IPC using SmartList v3.05 * >*************************************************************************** >* To subscribe/unsubscribe send a message <to: [log in to unmask]> * >* with <subject: subscribe/unsubscribe> and no text in the body. * >*************************************************************************** >* If you are having a problem with the IPC TechNet forum please contact * >* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * >*************************************************************************** > > *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************