ULTRASONIC INTERFERENCE SPECTROSCOPY FOR PLASTIC IC PACKAGES
Narayan R. Joshi Department of Civil Engineering, Prairie View A & M University PO Box 397, Prairie View, Texas 77446, USA
Keywords: NDT, Ultrasonic interference spectroscopy, Void, Cracks, IC packages
ABSTRACT
Plastic IC packages are routinely inspected for delaminations, voids, cracks and corrosion using the C-mode acoustic microscopy. Plastic IC packages are hygroscopic and can absorb moisture subjected to environmental cycling depending on the quality of the plastic mold compound used to encapsulate the IC chip. The advanced ultrasonic interference spectroscopy (UIS) technique used by the author elsewhere to detect presence of moisture in adhesively bonded joints is tried in this research work on plastic DSP (Digital Signal Processor) IC packages for the same purpose. Initially the UIS technique was tried on two simulated IC packages (Lexan-Silicon wafer and Plexiglass-Silicon wafer) with thin water film trapped between the layers. The technique successfully detected the presence of an extra water layer and estimated its thickness accurately bonded assembly of materials widely different in acoustic properties. The UIS technique using 75 MHz broad band focused transducer when tried on DSP packages, it responded according to its internal mechanical structure predicted by the theory.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 2, pages 775 - 780 Publisher:Ashgate Publishing Company
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