Reflow Oven Horizontal ConvectionTM Defined

Leading up to the development of lead-free soldering alloys, Horizontal Convection* was developed for the reflow process.  Getting the correct reflow temperature profile, with the narrow process window in lead-free applications, is now more important than ever.  In each chamber or zone, air is circulated toward one side of the reflow oven above the PCB and toward the opposite side of the reflow oven below the printed circuit board (PCB), forming a cyclone around the PCB.  The forced air circulation results in a uniform temperature profile along the entire circuit board assembly.  This technology is ideal for the precise reflow profiles for lead-free soldering.

*Patent # 6,936,793

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Reflow Oven Horizontal Convection Process

 Horizontal Convection Defined

 1.  The main difference between Horizontal Convection
     and traditional reflow oven technololgy.

      In traditional reflow ovens, air currents introduced are          
      vertically from above and below the PCB.  In Horizonal                                        Cross-section of a GF-120 reflow oven with
      Convection, air is circulated horizontally in one direction                                     Horizontal Convection.  Air is recirculated
      across the top of the board and in the opposite direction                                    within the confines of each chamber.
      beneath the board.  This is key.  This prevents hot spots
      and this parallel "angle of attack" enhances the ability of 
      the air stream to infiltrate the spaces underneath component
      bodies such as BGAs and J-leaded devices.

 2.  Lower overall equipment cost and operation cost.

      Because the Horizontal Convection system requires neither
      plenum now air reintroduction apparatuses, it is (due to its
      simplicity) more reliable and less costly.  There is no need
      for costly flux management systems, as there is no sticky                 
      flux residue in the oven, greatly reducing the need for constant                         Reflow profile taken in a GF-120HC, 3 zone
      cleaning, maintenance, and servicing.                                                                    reflow oven.  Actual board temperatures
                                                                                                                                               recorded with 6 thermocouples evenly
3.   Eliminates hot spots across the board.                                                                positioned across the board.

      Temperature uniformity is ensured by controlling the air flow
      around the PCB and by having consistent temperature, air
      pressure, air velocity, volume, and direction across the board.
      The top and bottom of the board receive the air from the outsides
      toward the center, which acts to counter the center hot spot/cool-outside
      condition.  This minimizes thermal stress to PCB materials and components.

4.  No flux management system needed.

     There is no flux residue because the air is recirculated within the confines of
     each reflow chamber.  Chambers each contain all the elements needed to be
     self-sufficient:  heating elements, fan blades, inert gas suffusers and exhaust
     ports.  The air never comes in contact with cooler surfaces and thus does not
     condense anywhere in the reflow oven.

5.  Uses less nitrogen in inert atmosphere applications.

     An advantageous side effect of the Horizontal Convection system is an ability to
     produce low oxygen ppm (parts per million) levels when purging the inert gas,
     because the volume of space affected includes only the confines of each reflow
     chamber.  By contrast, in traditional reflow oven design the chamber, as well as the
     upper and lower plenums must be purged.

6.  The best profiles...Period!

     There are multple reasons for this claim.  Heated air within each reflow zone is
     completely controllable and precise.  Temperatures across the PCB are uniform
     with no hot spots because air is circulated horizontally in a circular or "cyclone" motion
     around the PCB.  Temperatures across the entire PCB, front to back, are virtually identical. 
     DDM Novastar is willing to compare its superior profiles to any other profiles in the industry.






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