US 5,592,562 AGranted

Inspection system for cross-sectional imaging

AssigneeInternational Business Machines Corporation

InventorStephen M. Rooks

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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.

Claims22

Dependent claims

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 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.

15 more elements

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:

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.

14 more elements

Dependencies are inferred from the claim text.