Systems and methods for applying a liquid coating material to a substrate

Abstract

Systems and methods for applying liquid coating materials to a substrate, such as an electronic component or circuit board. A control system (18, 24, 26) of a coating system (10) controls an applicator (16) and a robot (14) moving the applicator (16) to apply the liquid coating material to the substrate (12) in accordance with the information contained in a coating program. The control system (18, 24, 26) determines a volume of liquid coating material actually dispensed onto the substrate (12) during the coating program, and compares the dispensed volume to a desired dispensed volume of liquid coating material to produce an error signal representing the difference between the calculated and desired volume values. The control system (18, 24, 26) uses the error signal to change the dispensed volume of liquid coating material on a subsequent substrate by a future coating program.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001]This application claims the benefit of U.S. Provisional Application No. 60 / 806,024, filed Jun. 28, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.FIELD OF THE INVENTION [0002]The present invention relates generally to dispensing liquid coating materials and, more particularly, to a system and method for applying liquid coating material, such as a conformal coating material, to a substrate, such as a circuit board.BACKGROUND OF THE INVENTION [0003]Many industrial applications require the use of discrete, well-defined and uniform coatings applied to predetermined areas. Such coatings are very useful in varied processes, such as conformal coatings on non-uniform or irregular substrates like electronic circuit boards. In the production of discrete coatings for application to discrete substrate areas, for example, it is desirable to obtain broad, uniform coatings in a non-contact application process w...

AI Technical Summary

Benefits of technology

The patent describes a system and method for applying liquid coating material to a substrate based on a coating program. The system includes an applicator, regulator, and meter to control the flow of the coating material. A robot moves the applicator relative to the substrate, and the control system controls the robot and applicator to apply the coating material in accordance with the program. The control system uses volume signals from the meter to determine the dispensed volume of the coating material applied to the substrate. An error signal is produced if there is a difference between the dispensed volume and the desired dispensed volume, and the control system adjusts the dispensed volume to reduce the difference in subsequent substrates. The technical effect of this patent is to provide a more precise and accurate method for applying liquid coating material to a substrate.

Problems solved by technology

Conventional coating material dispensing systems may be inaccurate if used for applying conformal coating selectively to components or areas of a circuit board because the dispensing valve will only be opened for a very short time interval, perhaps as short as a few milliseconds.

Either the time interval, the number of encoder counts, or both, may be characterized by significant inaccuracies, which will result in an inaccurate calculation of flow rate.

The system then compares the inaccurate calculated flow rate to the set point to produce an “error.”f Because of the inaccuracy, the error from the comparison may result in a correction of the wrong magnitude or even a correction in the wrong direction.

Either result may cause an improper amount of coating material to be dispensed the next time the dispensing valve is opened.

The result could easily be that the system produces so much inaccuracy it is of little practical value to the user.

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