Patent ID: 8545931

Claim:
A method of dispensing a discrete line of conformal coating material onto a predetermined area of a substrate with an applicator operatively coupled to a programmable control and a positioner, the applicator including a needle valve coupled to an actuator for opening and closing the needle valve based on signals from a timing device to dispense a supply of the conformal coating material pressurized by air from a pressure regulator, the applicator also including a capillary tube located downstream from the needle valve and a dispensing needle located downstream from the capillary tube and having a needle tip, the method comprising: selecting a size of the dispensing needle to set a desired droplet size for the conformal coating material that will release from the needle tip of the dispensing needle; selecting an air pressure delivered by the pressure regulator to set a desired fluid pressure of the conformal coating material at the needle valve; selecting a stroke length of the needle valve to set a desired flow rate of the conformal coating material through the needle valve; selecting an On time and a Cycle time for the timing device to set a desired pulse rate of the needle valve, the On time defining a duration of each pulse applied by the timing device and the Cycle time defining a duration between the beginning of consecutive pulses applied by the timing device; selecting a speed of the positioner to set a desired movement velocity of the applicator; and actuating the positioner and the timing device with the programmable control such that the applicator moves at the desired movement velocity while the timing device applies a string of electrical pulses at the desired pulse rate to the actuator, which opens and closes the needle valve for each electrical pulse, thereby ejecting droplets of conformal coating material through the capillary tube and the dispensing needle, wherein the desired droplet size, the desired flow rate, the desired fluid pressure, the desired pulse rate, and the desired movement velocity collectively cause the ejected droplets to coalesce into the discrete line located accurately within the predetermined area of the substrate.