AUDIOTACTILE INSPECTION DEVICE: A COST EFFECTIVE MEANS AND METHOD OF PERFORMING SURFACE QUALITY VERIFICATION
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-May-31
Surface quality inspection for visual/mechanical defects (e.g., molded package voids, pits, and cracks) is expensive and slows the production throughput rate. This invention/technique provides a rapid, low-cost means of performing surface quality verification. The principle of the AudioTactile invention is as follows: In the same manner in which a small, nearly invisible surface defect in a vinyl phonograph record produces a loud click or pop in the audio system when encountered by the phono cartridge's needle, a "bristle brush" feeler assembly substituted for the "needle" would trans- mit a similar audio vibration signal to the phono cartridge in the AudioTactile Inspection Device upon encountering a surface defect in the molded body of an electronic component. Different size surface defects would produce corresponding amplitude noise spikes to the input of the adjustable threshold comparator, which in turn would switch its output high and trigger the one-shot pulse gener- ator to output a reject signal to the test handler equipment. (See block diagram below.) accurately converting very tiny mechanical movements into acoustical frequency electrical signals. By replacing the cartridge's needle with a plug-in assembly carrying a small bristle brush-like array of feelers, a transducer is created which can "feel" a broader surface in one pass than could the needle. The width of the feeler array could be made to correspond to the width of a semiconductor device package. By either passing the surface of the device package under the array, or moving the feeler array over the surface of the package, an electrical signal is created with an acoustical signature corresponding to the surface smoothness. Any irregularities (e.g., pits, voids, cracks) would produce a significant amplitude variation in the output signal. Such amplitude "spikes" could be detected by either a simple op amp voltage comparator circuit, or more sophisticated A/D units followed by a microprocessor and software set up to detect particular defect signatures.