Inspection system for cross-sectional imaging
First Claim
1. A method of inspecting a solder joint of a ball-grid array comprising the steps of:
- using cross-sectional images of said joint generated in planes intersecting said joint at ball, pad and package slices;
locating the centroid of the solder ball of said joint in said cross-sectional image taken at said ball slice; and
performing the steps ofa) measuring said joint at said pad slice;
locating the centroid of said pad;
determining the ball pad offset;
measuring image background gray level and average solder thickness in the region of said pad;
measuring solder thickness on said pad in a plurality of annular rings positioned relative to said ball and pad centroids;
measuring the extent of solder on said pad relative to the centroid of said pad;
b) measuring said joint at said package slice;
locating the centroid of said joint at said package slice;
determining the ball joint offset at said package slice;
measuring image background gray level and average solder thickness at said joint on said package;
measuring solder thickness on said package in a plurality of annular rings positioned relative to said ball and package centroids;
measuring the extent of solder at said package relative to the centroid of the joint at said package slice; and
c) comparing selected measurements to predetermined threshold valuations to identify a defective or acceptable joint.
1 Assignment
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Accused Products
Abstract
A method and apparatus for inspecting a bonded joint between components. A cross-sectional image of the joint is analyzed by determining the location of a first characteristic of the joint, the centroid of the joint in the cross-sectional image; and then measuring a second characteristic of the joint in reference to the location of the centroid. This measurement may be used by comparing it with a predetermined specification expected for the measurement for the purpose of determining the quality of the joint. The invention is particularly advantageous for studying cross-sectional X-ray images of solder joints between electronic components and substrata upon which they are mounted and can be implemented for analyzing the images produced in cross-sectional X-ray inspection machines such as scanned beam X-ray laminography systems or digital tomosynthesis systems.
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Citations
22 Claims
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1. A method of inspecting a solder joint of a ball-grid array comprising the steps of:
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using cross-sectional images of said joint generated in planes intersecting said joint at ball, pad and package slices; locating the centroid of the solder ball of said joint in said cross-sectional image taken at said ball slice; and performing the steps of a) measuring said joint at said pad slice; locating the centroid of said pad; determining the ball pad offset; measuring image background gray level and average solder thickness in the region of said pad; measuring solder thickness on said pad in a plurality of annular rings positioned relative to said ball and pad centroids; measuring the extent of solder on said pad relative to the centroid of said pad; b) measuring said joint at said package slice; locating the centroid of said joint at said package slice; determining the ball joint offset at said package slice; measuring image background gray level and average solder thickness at said joint on said package; measuring solder thickness on said package in a plurality of annular rings positioned relative to said ball and package centroids; measuring the extent of solder at said package relative to the centroid of the joint at said package slice; and c) comparing selected measurements to predetermined threshold valuations to identify a defective or acceptable joint. - View Dependent Claims (2, 3, 4)
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5. A method of inspecting a soldered joint of a ball-grid array comprising joining a package and a substrate, having one or more connection pads, comprising:
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a) locating the centroid of the solder ball of said joint in a cross-sectional image of said joint across said ball; locating the centroid of the pad of said joint in a cross-sectional image of said joint across said pad; calculating the offset of said pad and ball as determined by comparing said locations between said images; b) measuring the local background gray levels of cross-sectional images of said joint at pad and package slices; c) measuring characteristics of said joint in said cross-sectional images at pad and package slices by measuring the average solder thickness in circumjacent rings centered with respect to the offset between the centroids of said ball and pad; d) determining the extent of said solder at said pad and package slices by determining the edge contour of said solder joint; and comparing information obtained thereby with predetermined threshold valuations. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. Apparatus for inspecting a solder joint of a ball-grid array, using cross-sectional images of said joint generated in planes intersecting said joint at ball, pad, and package slices, comprising:
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means for locating the centroid of the solder ball of said joint in said cross-sectional image taken at said ball slice; a) means for inspecting said joint intersected at said pad slice, comprising; means for measuring said joint at said pad slice; means for locating the centroid of said pad; means for determining the ball pad offset; means for measuring image background gray level and average solder thickness on said pad; means for measuring solder thickness on said pad in a plurality of annular rings positioned relative to said ball and pad centroids; means for measuring the extent of solder on said pad relative to the centroid of said pad; b) means for inspecting said joint intersected at said package slice, comprising; means for measuring said joint at said package slice; means for locating the centroid of joint at said package slice; means for determining the ball package offset; means for measuring image background gray level and average solder thickness at said package slice; means for measuring solder thickness at said package slice in a plurality of annular rings positioned relative to said ball and package centroids; means for measuring the extent of solder at said package slice relative to the centroid of said joint at said package slice; and c) means for comparing selected measurements to predetermined threshold valuations to identify a defective or acceptable joint. - View Dependent Claims (13, 14, 15)
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16. Apparatus for inspecting a soldered joint of a ball-grid array joining a package and a substrate, having one or more connection pads, comprising:
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a) means for locating the centroid of the solder ball of said joint in a cross-sectional image of said joint across said ball; means for locating the centroid of the pad of said joint in a cross-sectional image of said joint across said pad; means for calculating the offset of said pad and ball as determined by means for comparing said locations between said images; b) means for measuring the local background gray levels of cross-sectional images of said joint at pad and package slices; c) means for measuring characteristics of said joint in said cross-sectional images at pad and package slices by measuring the average solder thickness in circumjacent rings centered with respect to the offset between the centroids of said ball and pad; d) means for determining the extent of said solder at said pad and package slices by determining the edge contour of said solder joint; and means for comparing information obtained thereby with predetermined threshold valuations. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification