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86 SMT Magazine • April 2016 consisTEnT conTrol ovEr ThE sElEcTivE soldErinG ProducTion ProcEss offset. For a multi wave dip process, a fiducial recognition or a mechanical pin-hole device (between nozzle plate and pallet/board) are able to correct the offset. Also, in machines where the board remains in the conveyor the clamping of the assembly may not be that con- sistent and a fiducial recognition sys- tem can be implemented to correct the offset. In a multi-wave dip process, board warpage is corrected by stand-off pins in the solder point and the z-position is fixed. For select wave soldering the warpage of the board can be critical. If the board bends too much the pin connector may touch the nozzle or the solder may not touch the board when warped in the opposite direction. Figure 11: Camera image at end of preheat. With software it is possible to analyze the temperatures of various spots on the assembly. Figure 12: Dot-plot of the different measurements, robot only versus fiducials of one board and multiple boards.