The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 14, 1991
Filed:
Oct. 04, 1989
Mineo Nomoto, Yokohama, JP;
Takanori Ninomiya, Hiratsuka, JP;
Hiroya Koshishiba, Yokohama, JP;
Toshimitsu Hamada, Yokohama, JP;
Yasuo Nakagawa, Chigasaki, JP;
Hitachi, Ltd., Tokyo, JP;
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.