Unpowered opens test with X-ray laminography

• Published in: Proceedings - International Test Conference p. 276
• Main Author: Oresjo, S.
• Format: Conference Proceeding Journal Article
• Language: English
• Published: IEEE 1997
• Subjects: Calibration; Image processing; Lead; Length measurement; Mechanical variables measurement; Soldering; Testing; X-ray detection; X-ray detectors; X-ray imaging
• DOI: 10.1109/TEST.1997.639625
• ISBN: 0780342097; 9780780342095
• ISSN: 1089-3539

It is shown how X-ray laminography can be used to detect solder opens. With this method X-ray images are taken of the device under test (DUT). The lead content in solder makes the solder joints appear clearly in the image. Using image processing algorithms and also calibration information, the captured image of the solder joint is automatically translated into key mechanical measurements of the solder joint, such as heel height, center height, toe height, average height, fillet length and width at the toe and the heel. An important feature of this method is that these mechanical characteristics of the solder joint are used by the image processor to automatically determine an open solder joint from a good solder joint. All pins, including VCC and grounds, almost all component types, including bypass capacitors, can be inspected for opens as well as marginal opens. Typically over 98% of all solder joints on a PCB can be inspected.