Four Pi Systems Corporation

Hewlett-packard Company

Phase Metrics, Inc.

Edward W Ross

John Andrew Adams

Bruce D Baker

Robert L Corey

Christopher A Lacey

Christopher S Sexton

Gerald S Russell

Kerry L Brown

Paul A Roder

David C Reynolds

Brian L Ganz

A method and apparatus which incorporate self learning techniques for the detection of solder defects and for statistical process control of solding operations on printed circuit board assemblies (PCBA) are disclosed. The invention includes learning techniques which are used during the inspection of cross-sectional X-ray images of solder joints. These learning techniques improve measurement accuracy by accounting for localized shading effects, which can occur when inspecting double-sided printed circuit board assemblies. Two specific examples are discussed. The first is a method for detection of solder short defects. The second method utilizes learning to improve the accuracy of statistical process control (SPC) measurements.

Learning method and apparatus for detecting and controlling solder

Method and apparatus for inspecting electrical connections

The apparatus and method for measuring a small spacing down to contact uses an interferometric fringe intensity calibration to calibrate maximum and minimum intensity of two or more monochromatic or quasi-monochromatic interference patterns caused by a spacing between two articles, one of which is transparent. The intensity calibration is done by measuring maximum and minimum fringe intensity of each color while altering the spacing by at least 1/4 of the wavelength of the light or other electromagnetic radiation being used. The calibration by changing spacing allows the fringe order to be calculated for each wavelength of the radiation being used. This calibration procedure allows the maximum and minimum intensity of the radiation to be known, as well as the fringe order of the interference patterns to be calculated. With the maximum and minimum intensities and the fringe orders known, the spacing is readily calculated from interferometric theory.

Method and apparatus to calibrate intensity and determine fringe order

A method and apparatus for the detection of excess or insufficient solder conditions at electrical connections on printed circuit boards are disclosed. The invention analyzes a cross-sectional image of an electrical connection to obtain the average solder thickness of the connection. This average solder thickness is then compared to an upper threshold value to determine if the connection is an excess solder defect, and a lower threshold value to determine if the connection is an insufficient solder defect. In one embodiment, the present invention compensates for variations in image intensity due to the background by employing a first and second correction factor in the calibration technique. The first correction factor is the measured background gray scale value local to the connection, while the second correction factor is determined to have a substantially linear relationship to the background image intensity local to each solder connection. The present invention further includes a process control feedback system which detects and compensates for trends in the solder application process. This helps to insure that defective solder joints are avoided before they are produced. In one embodiment, the process control feedback system is fully automated.

Method and apparatus for detecting excess/insufficient solder defects

A high resolution laminography system for the inspection of integrated circuits wherein a beam of highly focused electrons is traced in a circular pattern on a flat target within a vacuum chamber. The target converts the electron beam into X-rays, so that a source of X-rays is produced which rotates in synchronization with a rotating detector assembly. An object is placed within the vacuum chamber, between the X-ray source and the detector so that an X-ray cross sectional image of a cutting plane of the object is produced. A computer and feedback system controls image acquisition and an automated positioning system. The computer system can also operate under program control to automatically analyze data, measure characteristics of the object under inspection, and make decisions regarding the acceptability of the object's quality. The invention also employs a channeltron imager to directly image the target so that the condition of the target may be monitored, and electron drift within the system can be compensated for.

Method and apparatus for high resolution inspection of electronic items

A tomographic inspection system wherein the electron beam of a microfocus X-ray tube is deflected in a circular scan pattern onto the tube anode in synchronization with a rotating detector that converts the X-ray shadowgraph into an optical image and derotates the image so as to be viewed and integrated in a stationary video camera. A computer system controls an automated positioning system that supports the item under inspection and moves successive areas of interest into view. In order to maintain high image quality, a computer system also controls the synchronization of the electron beam deflection and rotating optical system, making adjustments for inaccuracies of the mechanics of the system. The computer system can also operate under program control to automatically analyze data, measure characteristics of the item under inspection and make decisions regarding the acceptability of the item's quality. The invention produces high resolution images in rapid succession so as to be suitable for use in conjunction with manufacturing production lines and capable of inspecting electronic devices, solder connections, printed wiring boards and other assemblies.

Automated laminography system for inspection of electronics

Growing community of inventors

Escondido, CA, United States of America

Edward W Ross