Selective Solder Nozzle Geometry and Thermal Preheat Window Boundaries
Optimal selective soldering requires balancing nozzle orifice dimensions with precise top-side preheat windows to achieve Class 3 vertical barrel fill.
Drag Soldering Speed
Operational Rate
Linear velocity at which a selective soldering nozzle travels across the underside of a printed circuit board defines the contact time for point-to-point connections. Programmed drag soldering speed modulates the duration that the molten alloy interacts with the copper pads and component leads. This rate dictates the heat transfer efficiency during the soldering cycle.
Heat Transfer
Heat transfer into the barrel and onto the top-side lands depends on the dwell time created by the movement of the mini-wave. If the drag soldering speed is too high, the joint might suffer from insufficient wetting or cold solder defects because the copper fails to reach the required wetting temperature. Conversely, excessively slow movement allows heat to build up to a point where board delamination or damage to heat-sensitive components becomes a risk.
Correct calibration ensures that the solder stays fluid long enough to bridge the gap without creating shorts. This setting is the primary control for throughput in automated selective systems.
Machine Parameter
Machine parameters typically restrict these speeds based on the thermal mass of the assembly and the flux activation profile. A heavy copper backplane might require a travel rate as low as one millimeter per second to achieve full vertical fill. Standard consumer electronics often permit faster movement.
Total cycle time depends on the path optimization relative to this velocity.