Method for inspecting a BGA joint
View Patent ↗An inspection method utilizing vertical slice imaging. A number of horizontal slice images, extending through an object of interest, are acquired. A vertical region of interest is defined from the data representing the horizontal slice images. A vertical slice image is constructed based upon the horizontal slice image data falling within the vertical region of interest. The vertical slice image data may be analyzed to detect defects. In addition, a method is provided to detect defects in a BGA joint. The method includes locating a center of the joint. The method may further include measuring a number of diameters through the center of the joint and applying a rule to compare the measured diameters to an expected diameter.
1. A method for inspecting a Ball-Grid-Array joint comprising the steps of:
finding a location of the BGA joint;
improving the location using a fine locator;
measuring, in a slice image, a plurality of diameters through the BGA joint at predetermined angles; and
applying a rule to compare the measured diameters to an expected diameter wherein the rule comprises calculating a sum in the form of:
∑
i
=
1
N
(
D
-
d
[
i
]
)
2
where D is the expected diameter and d[i] are the measured diameters.
2. A method for inspecting a BGA joint as claimed in claim 1 , wherein the rule further comprises comparing the sum to a threshold.
3. A method for inspecting a Ball-Grid-Array (BGA) joint comprising the steps of:
finding a location of the BGA joint;
applying a plurality of locator windows over the BGA joint along the X-axis and a plurality of locator windows over the BGA joint along the Y-Axis;
locating BGA joint edges within the plurality of locator windows over the BGA joint along the X-axis and the plurality of locator windows over the BGA joint along the Y-axis;
determining a located center of the BGA joint based on the location of the BGA joint edges;
measuring, in a slice image, a plurality of diameters through the BGA joint at predetermined angles; and
calculating a deviation using the measured diameters and an expected diameter.
4. A method for inspecting a BGA joint as claimed in claim 3 , further comprising the step of comparing the deviation to a threshold.
5. A method for inspecting a BGA joint as claimed in claim 3 , wherein the plurality of diameters are measured at the located center of the BGA joint.
6. A method for inspecting a BGA joint as claimed in claim 3 , wherein the step of finding the location of the BGA joint comprises applying a centroid-based rough locator to the slice image.
7. A method for inspecting a BGA joint as claimed in claim 3 , wherein locating BGA joint edges within the plurality of locator windows over the BGA joint along the X-axis and the plurality of locator windows over the BGA joint along the Y-axis comprises applying a derivative edge finder on either side of the BGA joint.
8. A method for inspecting a BGA joint as claimed in claim 3 , wherein the deviation comprises a sum of the differences between the measured diameters and the expected diameter.
9. A method for inspecting a BGA joint as claimed in claim 8 , wherein the deviation comprises a sum in the form of:
∑
i
=
1
N
(
D
-
d
[
i
]
)
2
where D is an expected diameter and d[i] are the measured diameters.
10. A method for inspecting a BGA joint as claimed in claim 3 , wherein the slice image is a synthesized slice image.
11. A method for inspecting a BGA joint as claimed in claim 3 , wherein the slice image is an actual slice image.