US 5,097,492 AGranted

Automated laminography system for inspection of electronics

AssigneeFour PI Systems Corporation

InventorsBruce D. Baker, Robert L. Corey, John A. Adams, Edward W. Ross

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Abstract

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.

Claims44

Dependent claims

A solder connection inspection device comprising:

an X-ray source comprising:
an electron source for producing a beam of electrons;
an anode having a surface upon which said electron beam impinges;
and
an electrical steering device for deflecting said electron beam to different locations on said anode surface, said steering device capable of causing said electron beam to rotate about an axis and to trace a path upon said anode surface thus causing said X-ray source to move in a first pattern, said first pattern defining a first plane;
an X-ray detector for producing an X-ray cross-sectional laminographic image of a cutting plane of said solder connection, said detector positioned to receive X-rays produced by said X-ray source which have penetrated said solder connection, said X-ray detector comprising:
a converter screen for producing an optical image corresponding to an X-ray image formed by said penetrating X-rays;
means for moving said converter screen such that it rotates about said axis and travels along a path defining a second pattern, said second pattern defining a second plane which is substantially parallel to said first plane;
an optical derotation device for transmitting said optical image from said rotating converter screen to a stationary optical image plane;
and
a camera located at said stationary optical image plane for detecting said optical image, said camera having an electronic output which corresponds to said optical image;
a control system for synchronizing the motions of said X-ray source and converter screen, such that said optical image representations of said X-ray cross-sectional laminographic images are formed at said stationary image plane, said control system comprising:
a sensor which monitors the position of said converter screen along said second pattern and transmits coordinates corresponding to the screen position;
and
a look up table which receives said coordinates from said sensor and transmits corresponding signals to said steering device thus causing said motion of said X-ray source to be synchronized with said motion of said converter screen;
and
a digital image processing system for analyzing said cross-sectional images and deriving from said cross-sectional images information which is indicative of features of said solder connection, said image processing system comprising:
an image digitizer for receiving said electronic image signal from said camera and forming a digital representation of said image which corresponds to said X-ray cross-sectional image of said solder connection;
and
a programmably-controlled computational section programmed to access predetermined regions of said digital image and to analyze said regions in accordance with a predetermined set of instructions for specific features indicative of particular types of solder defects.

17 more elements

An electrical connection inspection device comprising:

an X-ray source comprising:
an electron source for producing a beam of electrons;
an anode having a surface upon which said electron beam impinges;
and
an electrical steering device for deflecting said electron beam to different locations on said anode surface;
an X-ray detector for producing X-ray cross-sectional laminographic images of a cutting plane of an electrical connection, wherein said detector is positioned to receive X-rays produced by said X-ray source which have penetrated said electrical connection, said X-ray detector comprising:
a converter screen having a variable position image forming region for producing an optical image corresponding to an X-ray image formed by said penetrating X-rays;
an optical transformation device for transmitting said optical image from said variable position image forming region to a stationary optical image plane;
and
a camera for detecting said stationary optical image, said camera having an electronic output which corresponds to said optical image;
a control system for synchronizing the motions of said X-ray source and variable position image forming region such that said optical image representations of said X-ray cross-sectional laminographic images are formed at said stationary image plane, said control system comprising:
a sensor which monitors the position of said variable position image forming region and transmits coordinates corresponding to said image forming region position;
and
a look up table which receives said coordinates from said sensor and transmits corresponding signals to said steering device thus causing said motion of said X-ray source to be synchronized with said motion of said variable position image forming region;
and
a digital image processing system for analyzing said cross-sectional images of said electrical connection, said image processing system comprising:
an image digitizer for receiving said electronic image signal from said camera and forming a digital representation of said image which corresponds to said X-ray cross-sectional image of said electrical connection;
and
a programmably-controlled computational section programed to access predetermined regions of said digital image and to analyze said regions in accordance with a predetermined set of instructions for specific features of said electrical connection.

16 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/479,092Filed 12 Feb 1990 · continuation
Priority: 30 Oct 1987
Granted: 17 Mar 1992
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G01R 31/311
Using non-ionising electromagnetic radiation, e.g. optical radiation: of integrated circuits
G01N 23/043
And forming images of the material: using fluoroscopic examination, with visual observation or video transmission of fluoroscopic images
G01N 23/044
And forming images of the material: using laminography or tomosynthesis
G01R 31/302
Testing of electronic circuits, e.g. by signal tracer: contactless testing