Green synthesis of novel in-situ micro/submicron-Cu paste for semiconductor interconnection

A green method for the synthesis of in-situ Cu paste is developed. Cu particles are prepared through chemical reduction by selecting a special copper source, reducing agent, and solvent. Then the reaction solution is directly concentrated to obtain an in-situ Cu paste. The synthesis of Cu particles and the preparation of Cu paste are conducted simultaneously, and the process of separation, purification, drying, storage, and re-dispersion of powder are reduced. Particles are not directly exposed to air, thus the oxidation of micro/nano-Cu is effectively prevented, and the agglomeration of particles caused by drying and dispersion operations is simultaneously reduced. Furthermore, the proposed method has a certain universality, and different types of Cu sources can be used to prepare in-situ paste with different sizes and morphologies. The entire preparation process is simple, efficient, green, and the yield can reach 99.99%, which breaks through the bottleneck of the application of traditional micro/nano-Cu materials. Copper acetate based in-situ paste is sintered for 30 min at 260 °C and 2 MPa in a reducing atmosphere. The shear strength, resistivity, and thermal conductivity reach 55.26 MPa, 4.01 × 10-8 Ω·m, and 92.75 W/(m·K), respectively, which could meet the interconnection application of power semiconductor devices.

Reliability Analysis and Fault-Tolerant Operation in a Multilevel Inverter for Industrial Application

The extensive employment of power semiconductor devices in multilevel inverters (MLIs) has the consequence of increased failure probabilities. With numerous applications demanding highly reliable inverters, several fault-tolerant schemes have been devised to address switch open-circuit faults. This paper analyzes a multilevel inverter topology for IGBT modules undergoing open-circuit faults, a major impediment to reliable operation within a power converter. Reconfiguration of modulation is performed post-fault. A modulation scheme is implemented across failure modes as a hybrid of nearest level control and selective harmonic elimination. Reliability assessment of the topology is performed, including a comparison with previous literature in terms of component requirements and reliability. Simulation results validate the proposed solutions.

Influence of the Metal–Semiconductor Interface Model on Power Conservation Principle in a Simulation of Bipolar Devices

The purpose of the study is to present a proper approach that ensures the energy conservation principle during electrothermal simulations of bipolar devices. The simulations are done using Sentaurus TCAD software from Synopsys. We focus on the drift-diffusion model that is still widely used for power device simulations. We show that without a properly designed contact(metal)–semiconductor interface, the energy conservation is not obeyed when bipolar devices are considered. This should not be accepted for power semiconductor structures, where thermal design issues are the most important. The correct model of the interface is achieved by proper doping and mesh of the contact-semiconductor region or by applying a dedicated model. The discussion is illustrated by simulation results obtained for the GaN p–n structure; additionally, Si and SiC structures are also presented. The results are also supported by a theoretical analysis of interface physics.

Online Monitoring of Power Converter Degradation Using Deep Neural Network

Power semiconductor devices in the power converters used for motor drives are susceptible to wear-out and failure, especially when operated in harsh environments. Therefore, detection of degradation of power devices is crucial for ensuring the reliable performance of power converters. In this paper, a deep learning approach for online classification of the health states of the snubber resistors in the Insulated Gate Bipolar Transistors (IGBTs) in a three-phase Brushless DC (BLDC) motor drive is proposed. The method can locate one out of the six IGBTs experiencing a snubber resistor degradation problem by measuring the voltage waveforms of the three shunt resistors using voltage sensors. The range of the degradation of the snubber resistors for successful classification is also investigated. The off-the-shelf deep Convolutional Neural Network (CNN) architecture ResNet50 is used for transfer learning to determine which snubber resistor has degraded. The dataset for evaluating the above classification scheme of IGBT degradation is obtained by measuring the shunt voltage waveforms with varying snubber resistance and reference current. Then, the three-phase voltage waveforms are converted into greyscale images and RGB spectrogram images, which are later fed into the deep CNN. Experiments are carried out on the greyscale image dataset and the spectrogram image dataset using four-fold cross-validation. The results show that the proposed scheme can classify seven classes (one class for normal condition and six classes for abnormal condition in one of the six IGBTs in a three-phase BLDC drive) with over 95% average accuracy within a specific range of snubber resistance. Using grayscale images and using spectrogram-based RGB images yields similar accuracy.

Analysing Efficiency and Reliability of High Speed Drive Inverters using Wide Band Gap Power Devices

Within the project ‘ARIEL’ an electrical turbo compressor unit for fuel cell applications is deeply investigated. The necessary drive inverter is especially designed for high fundamental frequency and high switching frequency to cope with the requirements of the implemented electrical machine. This paper presents investigations on the inverter’s efficiency and its prospective lifetime at different stages of the development. In the design process different wide band gap power semiconductor devices in discrete packages are evaluated in terms of the achievable power density and efficiency, both by simulations and measurements. Finally, an optimised design using surface mount silicon carbide MOSFETs is developed. Compared to a former inverter design using silicon devices in a three-level topology, the power density of the inverter is significantly increased. The lifetime of power electronic systems is often limited by the lifetime of the power semiconductor devices. Based on loss calculations and the resulting temperature swing of the virtual junction the lifetime of the inverter is estimated for the most frequent operating points and for different mission profiles.

Energy efficiency of power electronics converters in traction power supply networks at voltage increase

The main features of the procedure for predicting electrical losses in power semiconductor converters of AC-DC and DC-AC systems of high voltage DC traction are presented. The procedure is based on simulation of multi-cycle switching of IGBT modules in combination with simulation of static and dynamic switching losses in traction converter circuits. The models take into account the switching frequency, physical processes in the formation of voltage and current diagrams at transition processes and in the static state of the switch elements. The model of loss assessment using particular types of IGBT modules is the basis for calculating the energy efficiency characteristics of traction converters for advanced high-voltage direct current traction systems.

Improvement of lithium-ion rechargeable battery (LIRB) for Electric Ships

The rapid improvement of lithium-ion rechargeable battery (LIRB) has given a powerful impetus to the development of environmentally friendly, powerful and universal for use on ships and underwater vehicles. The practice of building electric ships for many years has confirmed the effectiveness of electric propulsion for many types of vessels. Organically, electric propulsion fits into icebreakers and those vessels whose operation is associated with increased maneuvering modes and variable loads on propellers. LIRB has been actively used on ferries operating in a wide range of outdoor temperatures. On diesel-electric submarines (DES), the use of rechargeable batteries is traditional and is the main source of electricity. The subsequent development of new sources of electricity, the improvement of power semiconductor devices and microelectronics has led to the successful implementation of ideas for the construction of fully electric offshore facilities.