One Step Reflow With Vapor Phase Immersed Wave Solder

One Step Reflow With Vapor Phase Immersed Wave Solder

      Disclosed is a tool/process for single-pass reflowing a mixed
PIH/SMT card design.  This tool combines the high mass reflow and
preheat capability of a vapor phase reflow tool with the PIH
attachment capability of a wave solder into a single reflow unit.

      The disclosed tool/process, see figure below, consists of an IR
preheat, vapor chamber eutectic solder bath and pump/wave.  As a
panel travels via an edge clip conveyor system, it will first pass
through a foam fluxing section followed by an IR preheat section
prior to entry into the vapor/wave section.  The vapor/wave section
contains a eutectic Sn/Pb solder bath which is heated by electric
heating elements.

      As the solder is heated to reflow temperature it will, in turn,
heat the vapor phase fluid (non-CFC material) to its boiling point.
The vapor will be precluded from escaping the unit by cooling coils
located at the entry/exit points of the machine which will condense
the vapor onto the solder bath to be reheated.

      The vapor will reflow the SMT components on the card and also
preheat the card prior to reaching the wave.  With the entire card at
a uniform temperature, as a result of vapor phase heating, localized
distortion typically seen with wave soldering will be minimized.

      An existing problem with secondary reflow of topside SMT solder
joints, combined with localized distortion that may also occur, can
produ...