I have heard reports from a lab technician indicating that he has seen 
     "rubber" solder joints on some boards we had built.  The boards had an 
     organic coating before soldering.  I saw the condition myself, but 
     have to admit that I am not accustomed to poking at solder joints; I 
     usually just observe them.  In six years of surface mount experience, 
     I have never seen this condition, nor have I heard of it.
     
     The condition is explained as follows:
     
     Using a relatively blunt object (e.g. not a probe or pick), the 
     component lead can be moved within the solder joint without visible 
     fracture to that joint, and without the joint moving off the pad.  The 
     force used is undetermined, but I would consider it relatively gentle, 
     less than the magnitude of force used when trying to pull a lead out 
     of a joint.
     
     In some rare cases, the lead slides completely off the pad with the 
     joint still perfectly attached.  I think this indicates a problem with 
     the surface finish.
     
     In addition, some joints are very malleable; by using a blunt object, 
     it is easy to dent a joint without visible fracture.
     
     My questions are:
     
     * Has anyone else ever seen this phenomenon?
     
     * Does anyone venture to guess the root cause, or if this might be an 
     illusion?
     
     Doreen Fisher
     Dell Computer Corp.
     [log in to unmask]

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