Noel Shammas

Present problems of power module packaging technology

Abstract An overview of the problems encountered concerning power module performance and reliability is given and the main failure mechanisms are discussed. Experimental and simulation methods for the transient thermal characterisation of semiconductor packages are presented. An identification procedure that allows establishing the physical correspondence between the RC cells of the thermal model and the layers that constitute the electronic package is proposed. The results of tests on a number of commercial Smartpack ® modules provide useful information about the influence of materials properties and geometry on the step response. These could be used for package quality control and reliability investigations.

Series connection of insulated gate bipolar transistors (IGBTs)

In power electronics applications, high voltage switches are realised by connecting existing devices in series. The main problem of unequal sharing of voltage across the series connected devices can be minimised by using active gate control techniques, snubber circuits and clamping circuits. The aim of this paper is to investigate the available voltage balancing techniques in series connection of insulated gate bipolar transistors (IGBTs) and to describe a hybrid voltage balancing method which is used to equalise the voltage sharing in series connected IGBTs during both switching transients and steady state. This technique consists of both active gate control circuit and small passive snubber. The active gate control circuit is very simple and passive snubber is optimised to have low power losses. Passive snubber was optimised for different operating voltages and currents. The proposed technique was simulated for two 1 kV/50 A IGBTs in series and the results show good voltage balancing

A simple method for evaluating the transient thermal response of semiconductor devices

Abstract In this paper, a simple experimental method for the transient thermal characterisation of semiconductor packages is presented. The method is based upon the assumption that in many cases, device temperature evolution can be accurately described by a few exponential terms, as will be shown to be the case when transient thermal response has widely separated time constants. The proposed method, begins with the experimental determination of transient thermal response followed by numerical extraction of the time constants and amplitudes for the significant exponential terms, and is applied to a number of commercial Smartpack ® modules in order to obtain a dynamic model that can be used in circuit and numerical simulators, in order to predict the dynamic thermal behaviour of the device under any working condition.

A comprehensive review of thermoelectric technology, micro-electrical and power generation properties

Thermoelectric technology may provide an alternative to traditional methods of power generation, heating and cooling. A small amount of electrical power can be generated by a thermoelectric module if a temperature difference is maintained between two terminals, or can operate as a heat pump, providing heating or cooling of an object connected to one side of the module.

Novel voltage balancing technique for series connection of IGBTs

For high power electronics applications, high voltage switches are realised by connecting existing devices in series. The main problem of unequal sharing of voltage across the series connected devices can be minimised by using active gate control techniques, snubber circuits and active clamping circuits. The aim of this paper is to present a novel hybrid voltage balancing technique which can achieve good voltage balancing with minimum number of components and minimum total losses (i.e. IGBT losses and balancing circuit losses). This technique minimises the disadvantages in present voltage balancing techniques and it consists of both an active voltage clamp circuit and an optimised passive snubber. The passive snubber capacitance is optimised to have low power losses. The proposed technique was validated by both simulation and experimental work. In simulation, two lkV/50A IGBTs were connected in series and the results showed good voltage balancing with minimum losses. The experimental work was carried out on three 3.3kV71200A IGBTs connected in series. Experimental results showed good voltage balancing across the devices and the possibility of finding an optimum capacitance. Determining of the optimum snubber capacitance is critical in the hybrid voltage balancing technique and the dependence of the optimum capacitance on load is discussed.

Static and dynamic finite element modelling of thermal fatigue effects in insulated gate bipolar transistor modules

Abstract The aim of this paper is to demonstrate the use of finite element techniques for modelling thermal fatigue effects in solder layers of insulated gate bipolar transistor (IGBT) – modules used in traction applications. The three-dimensional models presented predict how progressive solder fatigue, affects the static and dynamic thermal performance of such devices. Specifically, in this paper, the analysis of an 800 A–1800 V IGBT module is performed. In the first part, the static analysis is realised. The parameters assessed are thermal resistance, maximum junction temperature and heat flux distribution through the different layers comprising the module construction. In the second part of the paper, transient analyses are performed in order to study the dynamic thermal behaviour of the module. The constructed thermal impedance curves allow for calculation of the device temperature variations with time. Stress parameters, such as temperature excursion and maximal temperature at chip and solder interfaces, are determined. Calibration of all simulation models is achieved by comparison with alternative theoretical calculations and manufacturers’ measured values provided in the data sheet book.

Igbt Parameter Extraction for the Hefner IGBT Model

The insulated gate bipolar transistor (IGBT) is now widely used in many power electronics circuits. An accurate IGBT model is very important and useful to simulate these power electronics circuits to foresee the circuit behaviour and device behaviour before its implementation. Hefner IGBT model is one of the very good IGBT analytical models available for circuit simulation. This model requires IGBT parameters and those can be extracted experimentally. Two experiment set ups are needed and few different tests have to be carried out to extract IGBT parameters required for the Hefner model. In this paper, work carried out to extract eleven different parameters of 3.3 kV/1200 A IGBT is explained for the Hefner model

Finite element simulation of thermal fatigue in multilayer structures: thermal and mechanical approach

Abstract The large difference in thermal expansion between dissimilar materials present in any electronic package is the source of a major problem to be solved in order to achieve improved reliability. In this paper, simplified thermal and mechanical finite element models are presented for the analysis of thermal stress derived problems. The problems investigated here include, thermal stresses in adhesive backbonds in surface mounted structures and effects of thermal fatigue in soft solder interfaces in conventional power modules such as insulated gate bipolar transistors modules. Full multi-dimensional mechanical and thermal analysis is made by using the commercial engineering computer package ansys . Validation of the thermal simulation is achieved by comparison between simulation and experimental test results, whereas a simple analytical model based upon the lap joint theory is used to verify the structural simulation.

A Review of Thermoelectric MEMS Devices for Micro-power Generation, Heating and Cooling Applications

Thermoelectric technology can be used to generate a small amount of electrical power, typically in the µW or mW range, if a temperature difference is maintained between two terminals of a thermoelectric module. Alternatively, a thermoelectric module can operate as a heat pump, providing heating or cooling of an object connected to one side of a thermoelectric module if a DC current is applied to the module’s input terminals. This chapter reviews the development of microelectromechanical systems (MEMS) based thermoelectric devices suitable for micro-power generation, heating and cooling applications. The chapter begins with a brief overview of thermoelectric technology, macro-thermoelectric module construction and operation. Micro-thermoelectric modules are introduced, and a review of recent developments in research, commercial development, and typical application of MEMS based micro-thermoelectric devices is made. The chapter draws conclusions on the development and potential application of MEMS based thermoelectric devices suitable for thermoelectric cooling, heating and micro-power generation.

Forward and reverse recovery behaviour of diodes in power converter applications

In this paper we report the characteristics, design considerations and the interaction of fast recovery diodes with the main power semiconductor switch such as thyristors, GTOs, and IGBTs for high power conversion applications. We briefly explain the switching phenomena in diodes and how these are characterised and optimised by using different structures for specific applications in conjunction with main switching devices.