| 摘要 |
Apparatus and methods for spray coating selected areas of a circuit board with a liquid coating material without coating regions of the circuit board to be left uncoated. In one mode of operation, a bead of liquid coating material dispensed from an elongated nozzle tip is atomized by directing jets of air pressurized against the bead to form a conical, swirling spray pattern which is sprayed on selected areas of a circuit board. In a second mode of operation, the non-atomized bead of liquid coating material dispensed through the elongated nozzle tip is applied on selected areas of the circuit board. In a third mode of operation, jets of pressurized air are directed against the bead of liquid coating material to create a soft swirl pattern, without atomizing the bead of coating materia. In a second embodiment of the invention, the bead of liquid coating material is dispensed from a nozzle without the elongated nozzle tip. In another embodiment of the invention, the nozzle is located closely adjacent a valve seat at the end of a liquid delivery passageway to minimize a residual volume of coating material in a volume between the valve seat and the nozzle so as to minimize drip and dribble upon startup. In another embodiment of the invention, pressurized air is diverted to an exhaust port when operating in a non-pressure-assisted mode so as to minimize pressure spikes and consequent splatter when initiating a pressure-assisted mode of operation. In another embodiment of the invention, pressurized air is supplied through a fluid damping system so as to minimize pressure spikes and consequent splatter when initiating a pressure-assisted mode of operation.
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