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Time-averaged speckle-interferometry for investigation and optimizing for electronic bond tools



Gorecki, C. ; Centre National de la Recherche Scientifique -CNRS-, Paris; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical inspection and micromeasurements : 10 - 14 June 1996, Besançon, France
Bellingham, Wash.: SPIE, 1996 (Europto series)
ISBN: 0-8194-2168-5
International Symposium on Laser, Optics and Vision for Productivity in Manufacturing <1, 1996, Besancon>
Conference "Optical Inspection and Micromeasurements" <1996, Besancon>
Fraunhofer IOF ()

For the purpose of investigation and optimizing of micro- mechanical and harmonic vibrating devices a measuring setup was developed. The goal was to determine vibrational mode structures as well as the magnitude of the amplitudes in dependence on the surface position at the observed object. Frequencies up to 100 kHz cause typical low amplitudes in the order of microns. To prevent any influence of the measurement on the vibration an interferometric system with a rough, speckled object wave seemed to be appropriate. A number of phase-shifted and -modulated speckle- interferograms are detected with a CCD-camera, digitized and transferred to a computer. A suitable algorithm compensates phase fluctuations partially occurring between the image snaps and calculates the amplitudes. To assess the errors investigations of the setup and algorithm used were carried out. It was found that a part from speckle noise mainly the low dynamics and noise of the CCD-camera limit the accurac y to about 0.5 percent of peak-amplitude. The setup was used to analyze the electronic ultrasonic bonding. The measured amplitude distributions of the bond-tool showed a high sensitivity in the clamp-in-conditions and were the base for a statement of an optimized clamp-in-length and a new developed tool.