Pan Pacific Symposium Conference Proceedings


Author: Janet E. Semmens
Company: Sonoscan, Inc.
Date Published: 1/26/2010   Conference: Pan Pacific Symposium

Abstract: Acoustic Micro Imaging (AMI) has been used over the past years to successfully evaluate the quality of flip chip underfill and interconnect bonds. Acoustic micro imaging uses high frequency ultrasound (5 to 500 MHz) to image the internal features of samples. Ultrasound is sensitive to variations in the elastic properties of materials and is particularly sensitive to locating air gaps (delaminations, cracks and voids).

Flip chip technology is constantly progressing toward smaller devices and higher IO count which leads to thinner chips, and smaller bumps and bonds which in turn requires higher resolution in the acoustic images. This is driving AMI technology to develop higher frequency transducers to increase the available resolution in both the spatial (x,y) and axial (z) dimensions. Low-k and extra low-k dielectrics are being used in flip chips and these materials present additional challenges for acoustic analysis due to their material properties. However acoustic signal analysis and imaging techniques are available to compensate. As a result of advancements in AMI technology and the refinement of analysis methods more can be determined concerning the nature of the failure mode. For example the failure may be laminar cracking of the passivation or low-k dielectric layers, or failures of the solder bump interconnect. This paper will present a catalogue of flip chip failure modes encountered to date and describe the analysis methods used to detect and define the failure modes.

Key words: Acoustic Micro Imaging (AMI), Acoustic Microscopy, Flip Chip

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