Optics: measuring and testing – By configuration comparison – With comparison to master – desired shape – or reference voltage
Patent
1989-10-04
1991-05-14
Evans, F. L.
Optics: measuring and testing
By configuration comparison
With comparison to master, desired shape, or reference voltage
356237, 382 8, G01B 1100, G01N 2100, G06K 900
Patent
active
050150979
ABSTRACT:
A method for inspecting the filled state of a plurality of via-holes which pass through a non-conductive circuit board and are filled with a conductive substance and an apparatus for carrying out the method are disclosed.
The surface of the circuit board is illuminated in two directions to generate shadows depending on the concave or convex state of the fillers in a plurality of via-holes. An optical image of the illuminated surface of the circuit board is detected. Each edge of the two shadow areas, which exist in the detected optical image and are generated in one via-hole by light irradiation in two directions, is detected. Whether the filler in this one via-hole is in the concave state or convex state is identified according to the mutual position relationship of the detected edges. The length of each shadow area is detected, and whether the concave state or convex state of the filler is within a predetermined allowance is decided according to the detection results. The area of the image of the filler is detected according to differences between the brightness of the board surface or of the via-hole wall and the brightness of the filler in the via-hole in the detected optical image, and whether the filler is lacking or not is decided according to the detection result.
REFERENCES:
W. E. Blanz, J. L. C. Stanz, E. B. Hinkle, "Image Analysis Methods for Solder Ball Inspection in Integrated Circuit Manufacturing", Proc. IEEE Int. Conf. on Robotics & Automation, pp. 509-514, 1987.
John R. Kender, Earl M. Smith, "Shape from Darkness: Deriving Surface Information from Dynamic Shadows", Proc. of 1st Int. Conf. Compt. Vision, pp. 539-546, 1987.
Singo Sekiguchi, Mitsutaka Ito, Shinichi Uno, "Apparatus for Inspecting Devices Mounted on Circuit Board (Chip Checker)", Papers of 2nd Symposium of Image-Sensing Technics in Industry, pp. 291-294, Jul. 1987.
Hamada Toshimitsu
Koshishiba Hiroya
Nakagawa Yasuo
Ninomiya Takanori
Nomoto Mineo
Evans F. L.
Hantis K. P.
Hitachi , Ltd.
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