Electrical connection test device for printed circuit board; obtains multiple delta-Z X-ray images by varying Z-axis distances and compares the variance of gradients of the images

摘要

The device has an X-ray source and detector to produce computerized X-ray tomographical images of the cross-section with respect to a focal plane. The distance along the Z-axis between the focal plane of the image and the reference plane is varied for various delta Z values, and corresponding delta Z images are obtained. The gradients and variances of the delta Z images are determined and compared. The device consists of an X-ray tube (200) and X-ray detector system (240) to obtain X-ray images of the major portions of the printed circuit (210), to check the electrical connections (214). The X-ray detector has a remote output for producing the cross-sectional images using a computer (270), with respect to a focal plane. A memory combines the detector data to produce a database, and generate a sectional image of a sectional plane of the electrical connections in the imaging plane. The Z-axis spacing ( delta Z), i.e. the distance between Z-axis direction between the focal plane and reference Z-axis position, is varied and multiple Z diagrams of the electrical connections are obtained. The gradients for the delta Z diagrams are calculated along with their variance. The variances of the gradients are compared for the delta Z diagrams. The Z-axis positions are preferably measured using a laser distance meter. Independent claims are also included for the following: (a) a method of determining the Z-axis positions; (b) a method of testing electrical connections in a printed circuit board