Hi Jim! Yes, metallurgical questions are always fun! (especially since we TechNetters are get to throw all sorts of different possibilities to you without exactly knowing the perfect answer). Silver diffuses into solder quite fast so your component would have to have a reasonably thick silver plate or very little solder paste available. If you did get a copper/silver intermetallic it would be very hard to "melt". The silver/copper eutectic point is nearly 800 C. I suggest you put a cross section of one of the solder joints (cut it out of the board) into the Scanning Electron Microscope and do a elemental mapping analysis. If you see silver migration into or at the copper pad interface then silver diffusion is the cause. If not, then look at component/soldermask interactions. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: ASSY: DE-SOLDERING PROBLEM Author: [log in to unmask] at ccmgw1 Date: 4/28/97 1:30 PM Hello Technetters: (Put on your metallurgical hats for a moment.) I ran into an unusual circumstance the other day that has me baffled. We soldered down a surface mount glass diode using conventional processes (Sn63 water soluble solder paste, convection reflow). The components were mis-oriented therefore had to be removed. To our dismay, the components wouldn't separate from the board (polyimide multilayer). Even though the solder was molten, the components wouldn't budge. Finally, the pads lifted off the board so I tried to remove the pads from the component, to no avail. It turns out that the component's base metal is pure silver which is then solder coated. The cross section looks like the silver dissolved with the solder, with the resultant alloy in contact with the copper pad (which was originally solder coated). Could the soldering process have created a metallurgical bond between the silver and the copper? Thanks for your assistance, Jim Marsico (516) 595-5879 [log in to unmask] ******************************** * ______ _ _ _____ * * / ___ | | | | | _____ * * / /___| | | | | | _____ * * __/ ____ | | | | |______ * * |____/ |_| |_| |________| * * * * SYSTEMS, INC. * ******************************** *************************************************************************** * 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] * ***************************************************************************