Evaluation of Molded Underfill Packages Using Acoustic Micro ImagingAuthor: Janet E. Semmens
Company: Sonoscan, Inc.
Date Published: 2/14/2012 Conference: Pan Pacific Symposium
The encapsulation requires lower frequencies than what is ideal for flip chip inspection. The molding compound introduces interference with imaging not only due to absorption (and resulting attenuation) of the high frequency signal but scattering due to a high concentration of filler particles and in many cases the presence of heavy voiding above the interfaces of interest. This presents a challenge to find a suitable frequency for analysis. Spectral analysis of the ultrasound echo at the interface shows the frequency content of the received echoes in response to the encapsulant. In molded underfill packages the downshift in frequency can be significant and certain transducers may not have sufficient frequency content in the range required to reach the interface. The frequency domain analysis provides a useful method of determining the appropriate frequency transducer to evaluate the devices. In addition reconstructing images from the frequency domain content at specified sequential single frequencies illustrates what frequency or range of frequencies will provide the best detection of the internal features or flaws.
This paper provides a brief background describing molded underfill packages and discusses the technical issues involved with acoustic microscopy evaluation of molded underfill packages including Fourier domain frequency analysis and imaging to determine the most suitable transducer and method for evaluation of the devices.
Acoustic Micro Imaging (AMI), Flip Chip, Molded Underfill (MUF)
Members download articles for free:
Not a member yet?
What else do you get when you join SMTA? Read about all of the benefits that go along with membership.
Notice: Sharing of articles is restricted to just your immediate work group. Downloaded papers should not be stored on an external network or shared on the internet.