APPARATUS FOR SOLDER REMOVAL

摘要

A solder leveling system for use in vapor phase soldering of printed wiring boards. A transport system operating in a near-horizontal mode moves the board to be solder coated through a vapor zone in a chamber having a solder pot which has a throat in line with the plane of the transport system. The near-horizontal movement through the vapor and into and out of the solder pot prevents solder sag and permits control of the thickness of solder deposited on the opposing board surfaces. Leveling nozzles are positioned in a vapor-filled chamber astride the transport system between the solder pot and the chamber throat. Perpendicular nozzle offset distance from the board and nozzle angle are adjustable. Preferably one nozzle projects a stream normal to the board, with the other nozzle projecting a grazing stream for clearing through holes. A nozzle flow rate corresponding to a predetermined energy threshold provides reliable hole clearing. Preferably the chamber throat is cooled for vapor containment, forming one of three cooling zones for vapor containment, vapor leveling, and condensation. In the preferred solder pot, as the board enters the sloping throat, solders spills over a weir into a reservoir from whence it is pumped into a standpipe which charges the sloping throat. Preferably solder is added to the pot through a drop tube having a lower end immersed in the solder to provide a unique vapor seal and means for determining the level of solder. A preferred transport system utilizes a spring loaded carrier providing easy loading and unloading of the boards.