1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for dispensing a viscous material on a substrate, such as a printed circuit board, and more particularly to a system and related methods for accurately dispensing material on a circuit board based on detecting an edge of the circuit board.
2. Discussion of Related Art
There are several types of prior art dispensing systems used for dispensing precise amounts of liquid or paste for a variety of applications. One such application is the assembly of integrated circuit chips and other electronic components onto circuit board substrates. In this application, automated dispensing systems are used for dispensing very small amounts, or dots, of viscous material onto a circuit board. The viscous material may include liquid epoxy or solder paste, or some other related material. Prior to performing a dispensing operation, the circuit board must be aligned or otherwise registered with a dispenser of the dispensing system. In one known method, this may be achieved by employing a vision system of the dispensing system to verify the location of landmarks, otherwise known as fiducials, on the circuit board. Specifically, to align the circuit board with the dispensing unit of the dispensing system, images of at least two fiducials are taken by a camera of the vision system. If the circuit board is out of position, a gantry capable of moving the dispenser may be manipulated to account for the actual position of the circuit board. In another embodiment, a support surface upon which the circuit board rests may be manipulated to accurately position the circuit board prior to performing a dispense operation.
One issue associated with the use of identifying fiducials to align the circuit board with the dispensing unit is when the area requiring dispensing is not well defined with reference to the fiducials. For example, if the area to dispense is not referenced with respect to the fiducials, the resulting dispense operation may be very inaccurate, and under many instances, may not meet the processing requirements.