DIRECTIONALITY TEST METHOD FOR THERMAL INK JET DIE ASSEMBLIES
Original Publication Date: 1999-Jun-30
Included in the Prior Art Database: 2004-Apr-09
Xerox Disclosure Journal
Disclosed is a method to test for mechanically induced directionality defects in Thermal Ink Jet (TLT) die assemblies using pressurized water, collimated light, and a pattern recognition system. The current method of defect detection involves the actual printing of images and automated optical inspection of those images. This involves precision electrical micro probes and fluid interfaces, marking substances such as ink, a coated paper printing medium, and sophisticated motion and electronic controls. The disclosed method to directionality testing relies on creation of an image pattern generated by pressurized jet streams of water simultaneously emitted from all ink jet channels. Water streams, edge lit by an extremely narrow beam of collimated light, create a light pattern that is captured and evaluated by an automated optical inspection system. Predetermined acceptance criteria is used to either accept or reject parts for further assembly processing. Since only pressurized de-ionized water, possibly having additives simulating ink to make a pattern visible is used, no electrical connection, ink, or paper is required. Moreover, die cleaning after test is not required making the test time as little as 15 to 20 seconds in duration.