The Failure Mechanism of Common-Mode Chip Inductors

The failure behavior of common-mode chip inductors (CMCIs) on printed circuit boards was investigated to reveal the failure mechanism of low-temperature co-fired ceramic (LTCC) devices. A specific model of CMCIs ( 0806-type ) with an insulation resistance greater than 10 9 Ω was used in this research. In the highly accelerated life test (HALT), the insulation resistance of the CMCI was rapidly reduced to less than 10 3 Ω, which was determined to be invalid. A variety of analytical techniques were used to determine the failure mechanism of the CMCIs, including computed tomography (CT), optical microscopy, scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). The results show that silver migration and Na enrichment are the direct reasons for the failure of the CMCIs. The Na + - β / β ″-Al 2 O 3 formed in the sintering provides pathways for the migration of Ag + and Na + in the LTCC under an electric field. With the further reaction, Na is enriched in the LTCC near the low potential while Ag + is reduced to Ag and deposited in the LTCC near the high potential, which causes the gradual failure of the insulation resistance of the CMCIs until a short circuit occurs.