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A hybrid battery thermal management system (BTMS) with phase change material (PCM) coupled cooling plate arrayed in the manner of honeycomb is proposed for the cylindrical lithium battery pack in this paper. Paraffin wax and glycol are used as PCM and cooling liquid, respectively. 3D numerical simulations are carried out to analyze temperature characteristics of the system, coupling characteristics of PCM and cooling plate, mass flow rate of cooling liquid and channel number of cooling plate on the heat dissipation of battery pack. Results show that the temperature distribution of the battery pack has good uniformity, which is the most prominent advantage of the proposed system. The coupling of PCM and cooling plate greatly improve heat dissipation effect. Increasing mass flow rate of cooling liquid can significantly improve heat dissipation efficiency, but the maximum temperature difference (Δ T max ) of battery cell also increases. However, the influence of channel number of cooling plate on heat dissipation efficiency is lower than that of mass flow rate. Adding one channel can reduce the battery temperature by 2 K, but it has little effect on Δ T max . This study may provide effective guidance for the design of the PCM coupled liquid cooling BTMS.

In this paper, a case in which Bi migration leads to the failure of the chip resistor was analyzed, the source of Bi has been studied, and the analysis process of failure mode and failure mechanism were summarized. Migration of reduced isolation constituents (MRIC) model was described briefly. The preventive measures of the corresponding failure modes were also suggested in this paper.

Electrochemical migration (ECM) of metal has been studied for decades, including Ag, Ni, Sn, Pb, Cu and Au. These metal materials are commonly used in microelectronics devices, both in package and die. According to the failure mechanisms, some of the root causes are easy to find out except Au, since contaminant element is hard to be detected, and electrolyte is various besides water. In a real failure analysis case, we developed a method to analysis contaminant and alcohol induced ECM of Au bond by combining ion chromatography and TOF-SIMS characterization, and IVA analysis. Based on the coupled analysis, the origin of Au ECM is related to chlorine ions and dominant electrolyte formed in low temperature (-45°C) is alcohol. These results indicate alcohol control in microcircuit plays an important role in sealed package.

The chip solder layer of power semiconductor devices carries the mechanical, thermal and electrical loads in the working state of devices. With the increase of packaging density and power density, the reliability requirement of solder layer is increased. Because the solder layer area of power module is much larger than that of traditional solder, its failure mode and mechanism have certain uniqueness, and it is urgent to study deeply. Through the failure analysis case study, this paper expounds the mechanism and the influence factors for the formation of the voids. The detection and verification test methods of voids defect is also introduced.

Graphene layers have been produced from multi-walled carbon nanotube (MWCNT) bulk materials by friction when polished on ground-glass, offering a novel and effective method to produce graphene layers, which, more importantly, could be transferred to other substrates by rubbing. Field emission scanning electron microscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy and selected area electron diffraction confirmed the formation of graphene layers. They were thought to be peeled away from the MWCNT walls due to friction. The reflection spectra showed that absorption of as-produced graphene layers decreased with wavelength in the range of 250–400 nm, compared to the MWCNT bulk material having strong absorption at 350 nm. Nanoscratch test was used to determine the mechanical properties of graphene films, suggesting the tolerance of as-produced graphene film to flaws introduced by scratch.

Graphene/carbon composite films were prepared by electrospraying a graphene/polyacrylonitrile composite solution on SiO2-coated silicon substrates and subsequent heat treatment. The as-produced graphene/carbon composite films had a porous structure comprising graphene layers. With a magnetic field applied perpendicularly to the sample, an unexpectedly significant positive magnetoresistance attributed to e–e interaction and weak localization has been observed, which constantly increases with the magnetic field in the temperature range of 300–50 K from 0 to 80 kOe.