| Chip tantalum capacitors with oxide manganese cathode are widely used inelectronic equipment for its high volumetric efficiency, low DCL, good temperature andfrequency characteristics, high reliability and life operating performance. However, asthe using of the capacitors in high-speed, low-impedance circuits increased，a certainfailure mode of surge current failure for dioxide manganese tantalum capacitors isbecoming an problem for both manufacturers and users.Until now, there are still no monographic studies on surge current failure of Tacapacitors found in domestic technique papers and reports. Research on the problem isstill on its initial stage. Bunch of research in surge current failure performed by forgeignexperts devided into about four hypotheses including scintillation theory introducted byKEMET, voltage oscillation theory by NASA, local thermal breakdown theory AVX andmechanical stress theory by KEMET.In this work, a set of comparison tests and a systematic analysis were carried outfrom different sides include degign, manufacuturing and applications, based on the fourtheories. Root cuases of surge current failure were investigated and an attempt to findout ways to improve manufacturing and screening method was also made from bothmacro and micro scale. Study shows that surge current failure is electric field-induced,not thermal-induced. The major internal factors for surge current are the strength oftantalum pellet and its structure stability and the main outside factors for the failuremechanism are the electric strength applied and thermal stress from soldering process.In this work, a set of measurements for design and screening were also recommended,including widthways-pressing method, multicircle reflow conditioning and1.2timesrated voltage for surge current screeting test.It is meaningful for improving the field reliability of chip Ta capacitors inlow-impedance, high-inrush current applications. It is also important for the company toescalate its technology. |
PDF Full Text Request