Hi all,

     We've been working at getting an automated line up and running.  We're
     making one sided ceramic substrates.  The substrates are both low
     temperature cofired ceramic and thick film copper.  Both have a 63/37
     solder coating on the tracks.  The substrates have passed
     solderability testing with ease.  The pads have been designed
     appropriately to minimize tombstoning.  Our components are solderable.
     We stencil print solder paste onto the substrates.  A robot places the
     components.  Reflow soldering happens in a Nitrogen convection oven.
     We are using RMA solder paste (still!)

     Now for the question.  Why do we get unsoldered connections?  Most are
     chip components where one end solders beautifully, the other end is
     sitting on a rounded mound of solder.  The distribution across the
     substrate and from one substrate to the next appears to be random.

     To detect unsoldered connections, we are doing the old brute force
     method of having manufacturing personnel looking for them after
     reflow.

     What are other folks out there doing to:
     1.  Solve the unsoldered connection problem
     2.  Detect the unsoldered connections

     Thank you,

     Kathie Lambert
     Process Engineer
     Northrop Grumman
     Baltimore, MD
     [log in to unmask]

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