Investigation on the Thermal Failure of Micro-USB Connectors in Mobile Phones

The application of micro-USB (universal series bus) is highly expanded by the development of many terminal electronic products, such as smartphones, pads, and e-book readers. However, in recent years, it has been reported that the micro-USB connectors used for recharger or data transmission in mobile phones are frequently burned around voltage bus (VBUS) during service. In this paper, the thermal failure mechanism of the burned micro-USB in mobile phones was analyzed from both insulation leakage and contact degradation. First, the failed micro-USB samples were detected to show the failure characters, and the possible failure mechanism was proposed preliminarily. Then, the dielectric performance of insulation material in micro-USB was measured and assessed. The chemical reaction happened between two electrodes (VBUS and ground) in the micro-USB under moisture and contaminated condition was discussed by electrochemical theory and was verified by an accelerated test, involving in the moisture, electric stress, and contamination. After that the finite-element analysis was used to simulate and calculate the thermal failure condition of the micro-USB. The contribution of current leakage and electric contact resistance on the thermal failure was discussed quantitatively. Finally, based on the accelerated corrosion test, burning failure of the degraded micro-USB was repeated experimentally to verify the validity of thermal analysis.