George,
     
     You should be able to help this guy....


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Subject: soldering gold pcb,s
Author:  [log in to unmask] at Internet
Date:    10/6/95 10:46 AM


     
     We are having some problems soldering to an electroless gold over 
     nickel card.  specifics are:
     
     5-10 microinches electroless gold over 20 microinches electroless 
     nickel.  .020 thick double sided smt card being soldered in a nitrogen 
     covection reflow oven. components range from 0603-1206 passives, sot 
     23 devices, and a 25 mil ssop. 
     
     Soldering is being done using Alpha 609 water soluble 63/37 paste with 
     a fairly standard profile.
     
     Results thus far are that the joints are granular, cold appearing, 
     with marginal wetting to both card and components.  There are also 
     numerous occurrances of voids/pinholes eminating from the lead pad 
     interface.
     
     Any insights would be helpful in the areas of:
     
                Profiles
                Pastes
                Methods for checking incoming solderability of the cards. 
                Any thoughts on optimal gold/nickel characteristics
     
     Thanks for the help.
     
     Steve Ethier
     Mgr. New Product Engineering
     Lockheed Martin Commercial Electronics 
     Tel: 603-885-8432