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Y. Li and D. Goyal
Fig. 18.7 EOTPR spectra from a failed unit, a golden unit, a bare SIP substrate, and a SIP package
without FPGA die (Adapted from Ref. [1])
As demonstrated in Fig. 18.8, the ε eff can be estimated based on the MLI and FLI
locations in the EOTPR time domain spectra and the actual distance between them,
which is around 1.6 mm measured from the design file. Using the estimated ε eff , the
distance between the failure location and the FLI can be calculated as about 100 μm.
By employing the same concept of adding more reference spectra to define the
locations of multiple levels of interconnects, and comparing to the spectra obtained
from the failing unit, both TDR and EOTPR could be applied to isolate open failures
in 3D microelectronic packages with die stacking configuration [8]. For 3D packages
with about 6 memory dice stacking on one another, reference units are created for
TDR to define the locations of multiple levels of micro bumps between the stacked
dice [8]. The result demonstrates that locations of micro bumps between the six
Fig. 18.8 The failure location can be estimated using known package structure locations in EOTPR
spectra (Adapted from Ref. [1])