Bryan:

     A few rules to guide you down the path:

     1) Gluing components is no problem. However, you don't need solder
     paste for the bottom side, since the wave soldering operation makes
     the electrical connection.
     2) Nitrogen is NOT required.
     3) Do NOT use components larger than SO28 in wave solder.
     4) Do NOT use ICs with lead pitch < 0.050" pitch. If so, bridging is
     almost guaranteed in the wave.
     5) Components need to be mounted with leads parallel to the wave. That
     way, the body of the IC will not create shadow voids or solder skips
     on the trailing side of the IC.  The same rule applies for passives;
     parallel to the wave prevents shadowing.
     6) IC and passive component land patterns may need to be extended
     slightly to guarantee wetting by the wave.  Rule of Thumb:  The pad
     should extend outward from the component >= to the height of that
     component.
     7) Do NOT mount tall components on the bottom side of the board.  Not
     only is there a land pattern consideration but also a clearance to the
     edge of the solder pot. I would limit the height of bottom-side
     components to the thickness of the SO-28 (~0.070" MAX)
     8) Do NOT use PLCC or QFP packages on the wave solder side of the
     board. See #3, #4 & #5.
     9) Solder thieves are helpful on the leading and trailing leads of the
     IC.  That way, if the board in placed in the wave solder BACKWARDS, it
     will still do OK.
     10) If the board is to be ICT tested, I STRONGLY recommend water wash vs.
     no-clean.  The flux acts as an insulator, it creates "false fails" or
     "flase opens" in ICT and also gums up the test points of the ICT fixture.

     Now that you know "where the rocks are", you can APPEAR to "walk on water"!
      Good Luck!

     Bill Fabry
     Plantronics, Inc.
     345 Encinal St.
     Santa Cruz, Ca. 95061
     (408) 458-7555
     e-mail:  [log in to unmask]

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Subject: [TN] Wave soldering SMD actives
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