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Solder Joint Inspection System Using Fuzzy Theory

IP.com Disclosure Number: IPCOM000119922D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Fujita, T: AUTHOR [+2]

Abstract

This article describes an algorithm for easily and reliably locating defective solder joints between surface mount type components and a printed circuit board with the utilizaton of fuzzy theory.

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Solder Joint Inspection System Using Fuzzy Theory

      This article describes an algorithm for easily and
reliably locating defective solder joints between surface mount type
components and a printed circuit board with the utilizaton of fuzzy
theory.

      The solder joint to be inspected is viewed from multiple
directions using a plurality of cameras.  For example, the solder
joint is viewed from four directions with four cameras which are
preferably disposed above the printed circuit board to look down the
joint at a selected angle with respect to the board.  The images shot
by the cameras are analyzed by applying fuzzy reasoning to the rules
which represent defective patterns.  The defective pattern rules are
represented by the following expression.

      IF X1 is (or is not) S1 and X2 is (or is not) S2
... , THEN, Dk where X1: feature value of each image
       Si: one of elements of the following fuzzy set
           (Very Dark, Dark, Medium, Bright, Very Bright)
       Dk: one of defect types
           Examples: no solder joint, poor solder joint, lead
floating
       Example:
       "IF the feature value of the image from camera 1 is Dark and
the feature value of the image from camera 3 is not Bright,
       THEN, poor solder joint"
      Fuzzy reasoning of one rule is performed by the following
procedure:
(1) Calculate membership grade of each feature value. Membership
grade (gi) of "Xi is Si"...