Hi folks - I agree with George's assessment. The critical parameter is not letting the IMC oxidize. Once the original solder is removed as George detailed, then re-tinning with the 95/5 alloy right away is key process step. Dave Hillman Rockwell Collins [log in to unmask] On Tue, Jul 12, 2016 at 8:50 AM, George Wenger <[log in to unmask]> wrote: > Hi Mary Grace, > > If your Sn95/Ag5 solder wets the wiring and components after SN63/Pb37 > removal I wouldn't be concerned about the integrity of the solder joint. > > However, the concern I would have is the ability for the Sn95/Ag5 solder > after wicking away the standard solder. I'm not a real fan of using solder > wick. When you solder to a component that has copper terminations the > "glue" that keeps the solder attached to the copper is copper-tin > intermetallic compound (IMC) that forms between the copper and solder. > Solder wick is a very good means of removing all of the molten solder from > a copper termination and it leaves behind the copper-tin IMC that doesn't > melt at soldering temperature. So if the reason you are removing the > SN63/Pb37 solder and re-soldering with Sn95/Ag5 solder is to make the > solder joint Pb-Free then solder wick is the method you would want to use. > The other method to remove the old solder would be to use a "solder > sucker". This method sucks away a lot of the molten solder (i.e., takes off > most of but not all of the molten solder) and leaves a small amount of old > solder on top of the copper-tin IMC. When you re-solder the Sn95/Ag5 should > wet the component termination very well. If you removed the Sn63/Pb37 > solder with a solder wick the copper-tin IMC is then on the outside surface > of the component termination and is exposed to the environment and it can > readily oxidize. The problem with oxidized copper-tin IMC is that the > oxidized IMC can't be reduced with standard soldering fluxes and the > surface will not wet well with solder. It may be that you can wick off the > old solder and re-solder immediately with the new solder and get good > wetting because the IMC hasn't had time to oxidize. If you do soder wicking > at one station and then at some later time do re-soldering at another > station you will probably find solderability issues. > > > Regards, > > George Michael Wenger > > George M. Wenger > Failure Signature & Characterization Lab LLC > 609 Cokesbury Road, High Bridge, NJ 08829 > (908) 638-8771 (Home) (732)-309-8964 (Cell) > [log in to unmask] > > ----- Original Message ----- > > From: "Mary Grace Keenan" <[log in to unmask]> > To: [log in to unmask] > Sent: Tuesday, July 12, 2016 8:15:08 AM > Subject: [TN] Using high temp solder after removing standard solder > > I have a question regarding using the high temp solder after removing > standard solder Sn63/Pb37. After wicking away the standard solder, we need > to re-solder the wiring and components using the high temp solder > (Sn95/Ag5). We are concerned that the integrity of the solder joint and the > temperature rating may be negatively affected. Is this a legitimate > concern? Any suggestions? > > > Regards, > Mary Grace Keenan, Quality Assurance Manager > Taber Industries > 455 Bryant St. > North Tonawanda, N.Y. 14120 > [log in to unmask] > Phone (716) 694-4000 Ext.134 > Fax (716) 694-1450 > > > *********************** DISCLAIMER *********************** > This email message contains information from Taber Industries for the > sole use of the intended recipient(s) and may contain confidential and > privileged information. Any unauthorized review, use, disclosure is > prohibited. If you are not the intended recipient, please contact the > sender by reply email and destroy all copies of the original message. > > Any data attached may contain information subject to the ITAR or EAR. > > This information may not be exported, released, or disclosed to foreign > nationals without first complying with the export license requirements of > the ITAR and EAR. > > While precautions are taken against computer viruses, it is your > responsibility to scan for their presence and we accept no liability or > responsibility therefore. > > > Thank you. > *********************** DISCLAIMER *********************** >