Failure analysis of automotive ultrasonic parking sensors by X ray computed Tomography

Automotive ultrasonic parking sensors were analyzed using X- ray computed tomography (XCT or micro tomography), to determine if there were internal failures generated on the soldering process between copper wires and piezoelectric ceramic on these sensors. This paper reports the use of X-ray Radiography, and computer image processing for the study of internal defects, by using X-ray tomography, internal defects like pores, cracks, holes, and solder bridging may be identified [1-2]. If coupled with a real time radiographic detector and image processor, X-ray technology allows instantaneous radiographic imaging and semi-automatic or full automatic inspection. Thefailure Analysis was conducted on six produced test samples, showing that the application of XCT as a method of quality control of specimens, produced by electronic packaging, offers a wide range of possibilities to detect defects within materials. There were determined that five sensors contain internal defects on the soldered joints, between thecopper wire, and the piezo electric ceramic covered with silver paint, as shown on the computed tomography.Accuracy of XCT method strongly depends on the size of the samples analyzed, but the possibility of obtaining information in 3D nondestructively shows considerable advantages of XCT method over traditional metallographic cross-sectional analysis, that show only images on 2D on one determined cutting plane. The thickness of the silver layer was increased, so that there was a better union between the copper wire and the ceramic wafer coated with silver paint.

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