November_EDFA_Digital

edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 22 NO. 4 24 bulk silicon. CSAM identified a ROI located near the die edge. This region was later determined to be a power-to- ground short and was the location of the failure. COUNTERFEIT CASE STUDIES SAM is a primary technique for identifying possible counterfeit components. Many counterfeit issues are not easily detectablewithother analytical systems. Traditional computed tomography (CT) x-ray analysis is not capable of discriminating the slight changes in material proper- ties which are characteristically found on many counter- feit parts. CASE #1: F 0 = 30 MHz The parts in Fig. 9 are one-time programmable (OTP) UV EPROMs. These parts passed incoming receiving inspection, high-magnification inspection, and CT x-ray inspection prior to being analyzed on the CSAM. CSAM images clearly show the presence of an abnormality located in the center of the component package. This discrepancy was not visible from the package exterior. Destructivephysical analysis showed that thepackages had been etched enabling erasure of the OTP program memory. After erasure the hole was filled with a similar epoxy material and the part was relabeled so it could be soldas newstock. CSAMwas the only technology available to identify the material property changes between the OEM plastic encapsulant and the fill material. CASE #2: F 0 = 50 MHz A common counterfeiting technique involves removing the surface coating of a used commercial-grade package so that the part can be relabeled. As an example, the CSAM image of a re-marked part (Fig. 10) clearly shows the traces of both the initial and final part markings. Visual examination of the part shows no evidence of the preexisting markings and no other methodswere available to ensure the initial label is uncov- ered without any destructive procedures. CASE #3: F 0 = 30 MHz To remove used components from circuit card assem- bly (CCA) boards, one common techniqueusedby counter- feit operations is to heat the board over a fire while using a hammer to vibrate the parts off. The CSAM image in Fig. 11 depicts a component that has been removed via the technique described in the above paragraph. The CSAM examination clearly shows fractures within the part concentrated around high stress regions. During the removal of the part, “popcorn” Fig. 11 CSAM image of popcorn fractures, indicated by red arrows. Fig. 9 CSAM images of EPROMs showing material dis- continuity in the center of the package on all five samples. Fig. 10 CSAM image showing initial and relabeledmarkings.