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edfas.org 25 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 22 NO. 4 fractures (denotedby red arrows) developdue to the rapid escape of moisture caused by excessive heating. LESSONS LEARNED Listed below are some lessons learned that can be used to enhance the CSAM operation and effectiveness. 1. The plastic encapsulated microelectronic package material is hydrophilic. Absorbed moisture can negatively impact the quality of the CSAM image. Consequently, it can be beneficial to dry out the part by baking it for 24 hours at 90°C, prior to CSAM analysis. 2. When imaging at frequencies above 100 MHz, it is important to increase the water temperature in the tank from normal room temperature to 45-50°C. The elevated water temperature reduces the high fre- quency attenuation compared to room temperature, but temperatures above 60°C can result in damage to the transducers. 3. The F # (F number) is a key parameter in most optic equations. Transducers with a higher F # exhibit better feature detection near edges. (Eq 4) 4. If the interface being examined is out of focus, the associated waveform can resemble a delamination resulting in “false positives.” Examination of the A-scan, while adjusting the focus, can be helpful in differentiating the false positives from real defects. 5. Knowledge about the part construction is key for accurately interpreting CSAM results. CT imaging and other analytical tools can help gain insight into the part construction. Maintaining known good samples for comparison with the test sample can help over- come knowledge deficiencies of the package. REFERENCES 1. Materials Properties Table, NDT Resource Center, https:// www.nde-ed.org/GeneralResources/MaterialProperties/UT/ut_ matlprop_index.htm. 2. K.-J. Langenberg, R. Marklein, and K. Mayer: “Ultrasonic Nondestructive Testing of Materials Theoretical Foundations,” Boca Raton, FL, USA, 2012. 3. D.P. Bossev, A.R. Duncan, M.J. Gadlage, A.H. Roach, M.J. Kay, T.J. Berger, D.A. York, A. Williams, and J.D. Ingalls: “Investigation of Radiation-Induced Response in Advanced Microprocessor,” International Symposium for Testing and Failure Analysis, 2016. 4. Nordson Sonoscan, “Acoustic Micro Imaging Advanced Topics,” Advanced User’s Workshop, Elk Grove, IL, USA, 2016, p. 1-27. 5. The American Society for Nondestructive Testing, “Basic Principles of Acoustics,” Ultrasonic Testing Classroom Training Book 2nd ed., Columbus, OH. USA, 2015, p. 20-27. ABOUT THE AUTHOR Eric Whitney graduated with a B.S. in electrical engineering from the University of Evansville. He is nowa failure analyst, counterfeit parts investigator, and SAMSME for NSWC Crane. He has analyzed electronic components for multiple agencies including Navy, MDA, DCIS, DHS, JFAC, Army, and Air Force and has assisted DCIS and DHS on several counterfeit raids that have led to the identifying of counterfeit parts. For his work on identifying counterfeit parts, he was awarded the United States Attorney Law Enforcement Award in 2019 by the United States Attorney’s Office Central District of California. Matching job seekers to employers just got easier with ASM International’s new CareerHub. After logging on to the ASM website, job seekers can upload a resume and do searches on hiring companies for free. Advanced searching allows filtering based on various aspects of electronics, e.g., R&D, manufacturing, or materials. Employers and suppliers can easily post jobs and set up pre-screen criteria to gain access to highly qualified, professional job seekers around the globe. For more information, visit careercenter.asminternational.org. VISIT THE CAREER HUB