Acoustic microimaging

Adams T. Using acoustic microimaging to inspect multichip modules. Electron Engineer Apr. 1996. 

Figure 6.6. Acoustic micrograph of delamination. (Source Using acoustic microimaging to inspect muitichip moduies, Sonoscan Brochure.)...

There are three indirect, nondestructive measurement techniques to determine thermal resistance acoustic microimaging, x-ray, and thermal test chips. The acoustic microimaging and x-ray methods can be used in both development and production, but the thermal test chip is restricted to development. The first two indirect thermal techniques find the amount of voiding in the thermal path and, through the use of thermal modeling, calculate the thermal resistance. The thermal test chip can only find the thermal resistance capability of the physical design. 

In acoustic microimaging, high-frequency ultrasoxmd in the 10 to 100 MHz range is used to nondestructively create images of internal features of microelectronic components. Acoustic transducers alternately pulse ultrasound... 

For the failure analysis of the test samples after the harsh environmental tests, various analysis tools are employed, e.g., scanning electron microscopy (SEM) with a cross-sectional analyzing technique, x-ray microscopy, A-, B-, and C-mode scanning acoustic microscopy (A-SAM, B-SAM, and C-SAM, respectively), and tomographic acoustic microimaging (TAMI), to analyze the failure samples. The continuous measurement of the electrical resistance should consequently be conducted during all of the environmental tests mentioned above. 

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