US 4,809,308 A · Method and apparatus for performing automated circuit board solder quality inspections

Abstract

A method and apparatus for measuring structural characteristics of a manufactured circuit board containing solder joints by automated real-time digital X-ray radiographic inspection techniques. A circuit board under examination is automatically positioned by a digitally controlled multi-axis positioning system between an electronic X-ray source and an electronic X-ray imaging system. X-rays, in a beam of X-rays from the X-ray source, are directed towards the circuit board. The X-rays are absorbed, scattered and transmitted through the circuit board. The X-rays transmitted through the circuit board are directed upon the X-ray imaging system. The X-ray imaging system converts the transmitted X-rays into digital images which represent the radiographic density of the portion of the circuit board under examination. The digital images are stored within a digital image processor. A computer, under program control, performs calculational measurements on the digital images so as to measure the structural characteristics of the solder joints and components on the circuit board. The calculational measurements are compared to predetermined standards corresponding to acceptable quality standards programmed into the computer. In response to the comparison, the computer provides an accept/reject decision on the circuit board in addition to providing manufacturing process control information for correction of found defects.

Claims21

Dependent claims

An apparatus for measuring structural characteristics of selected portions of a circuit board having components disposed upon and electrically connected thereto at solder joints, comprising:

X-ray means for providing a beam of X-rays;
multi-axis positioning means for receiving and for selectively positioning a circuit board, said circuit board having components coupled thereto at solder joints, within said beam of X-rays;
imaging means for detecting X-rays from said beam of X-rays transmitted through said circuit board and providing an electronic image thereof;
processing means for converting said electronic image into a gray scale coded image;
and
computational means for storing a library of measurement algorithms and predetermined measurement parameters corresponding thereto, for receiving said gray scale coded image, for analyzing said gray scale coded image by selecting measurement algorithms from said library of measurement algorithms with the selected measurement algorithms corresponding to certain structural characteristics of said circuit board, performing predetermined computational analysis on said gray scale coded image based upon each selected measurement algorithm, and providing a resultant analysis value corresponding to each computational analysis,
for comparing each resultant analysis value with each corresponding measurement parameter, and for providing an output corresponding to the variation of each resultant analysis value from each corresponding predetermined measurement parameter.

4 more elements

A method of determining the structural characteristics of a circuit board having components disposed thereupon and connected thereto at solder joints, comprising the steps of:

supporting a circuit board having certain structural characteristics by a multi-axis positioning means adjustable for optimum exposure of said circuit board to a source beam of X-rays;
exposing said circuit board to a beam of X-rays having sufficient energy to penetrate said circuit board;
detecting X-rays transmitted through said circuit board and providing an electronic image thereof;
coverting said electronic image into a gray scale coded image;
providing a library of measurement algorithms;
providing predetermined measurement parameters corresponding to said measurement algorithms;
selecting at least one measurement algorithm with each selected measurement algorithm corresponding to a respective one of said certain structural characteristics;
performing predetermined computational analysis on said gray scale coded image using each selected measurement algorithm;
providing a resultant analysis value corresponding to each computational analysis;
comparing each resultant analysis value with each corresponding predetermined measurement parameter;
and
providing an output indicative of the variation of each resultant analysis value from each corresponding predetermined measurement parameter.

9 more elements

Dependencies are inferred from the claim text.

Method and apparatus for performing automated circuit board solder quality inspections

Life of this patent

Method and apparatus for performing automated circuit board solder quality inspections

Life of this patent

Abstract

Claims21