Bipolar Transistor Power Research Articles

Splitter plate application on the circular and square pin fin heat sinks

The main aim of this work is devoted to present a numerical analysis for studying effect of splitter on the hydro-thermal behavior of a pin fin heat sink. The concept of application of pins in the heat sinks arises from increasing the heat transfer area to reach maximum rate of heat losses in a limited space. On the other hand, flow separation behind the pin will enhance the pressure drop. To avoid or weaken the flow separation and reduce the pressure drop through the heat sink, a thin plate is located on the back of the pin. Two common pin fin heat sinks with circular and square pin shapes are compared together with and without splitters. Results showed that the use of splitter improves the hydro-thermal performance of both circular and square pins, so that the maximum improvement will be occurred for the case of Q=10W and V=4.5m/s. Results indicates that for circular pin fin heat sink with splitter pressure drop reduces by 13.4%, thermal resistance decreases by 36.8% and profit factor grows by 20%. Also for square pins the same results of 8.5% reduction for pressure drop, 23.8% reduction for thermal resistance and 14% increase in profit factor are observed. Also reliability analysis showed that for low-frequency and bipolar power transistor, the number of failure is reduced for circular and square splitter pin fin heat sinks.

The state and prospects of further development of theory of power bipolar transistors

The state and prospects of further development of theory of power bipolar transistors

DC characteristics and parameters of silicon carbide high-voltage power BJTs

The paper shows the static characteristics and operating parameters of the bipolar power transistors made of silicon carbide and for comparison their equivalents made of classical silicon technology. The characteristics and values of selected operating parameters with special emphasis on the effect of temperature and operating point of considered devices are discussed. Quantitative as well as qualitative differences between the characteristics of the transistor made of silicon and silicon carbide are indicated as well.

Study on Oscillations During Short Circuit of MW-Scale IGBT Power Modules by Means of a 6-kA/1.1-kV Nondestructive Testing System

This paper uses a 6-kA/1.1-kV nondestructive testing system for the analysis of the short-circuit behavior of insulated-gate bipolar transistor (IGBT) power modules. A field-programmable gate array enables the definition of control signals to an accuracy of 10 ns. Multiple 1.7-kV/1-kA IGBT power modules displayed severe divergent oscillations, which were subsequently characterized. Experimental tests indicate that nonnegligible circuit stray inductance plays an important role in the divergent oscillations. In addition, the temperature dependence of the transconductance is proposed as an important element in triggering for the oscillations.

Development of a PSPICE Model for 1200 V/800 A SiC Bipolar Junction Transistor Power Module

The characteristics of a 1200 V and 800 A bipolar junction transistor (BJT) power module has been measured, simulated and verified for the first time in the PSPICE platform. The simulation model is based on a silicon carbide (SiC) Gummel-Poon model for high power applications. The implemented model has been extended with temperature dependent equations in order to extend the BJT operating temperature range. PSPICE simulations are performed to extract technology dependent modeling parameters coupled with static and dynamic characteristics of BJTs at different temperatures and validated against the measured data. The performance of the SiC BJT model is fairly accurate and correlates well with the measured results over a wide temperature range.

Multiobjective Design Optimization of IGBT Power Modules Considering Power Cycling and Thermal Cycling

Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field.

A Low Standby Power Primary-Side Regulated Flyback Controller with Fast Dynamic Response

Primary-side regulated (PSR) flyback controller has been widely used in low power charger applications for its simple structure, low cost, good electrical isolation and compact volume. However, limited by traditional primary-side sensing technology, PSR flyback controller suffers from poor dynamic response. A low standby power PSR flyback controller with fast dynamic response has been presented, and novel feedback comparison and sampler combo controlling circuit has been presented in the paper. An offline PSR controller containing the proposed speedup circuit and driving directly power bipolar junction transistor (BJT) was fabricated in Episil 1.0 μm 40 V/5 V EPI-HVCMOS process. Measured result shows that, in the entire universal input-voltage range (90 Vac–264 Vac) and 5 V 1.0 A output power, the proposed PSR controller achieves standby power less than 22 mW and average efficiency line end with 20 AWG 1.5 m up to 78%. The output voltage of the proposed PSR controller becomes stable within 3.3 ms when load current changes abruptly from 0 to 1 A and from 1 A to 0.

Simulation of the electric field strength in the vicinity of metallization edges on dielectric substrates

High electric field strengths at the edge of the metallization of insulated gate bipolar transistor (IGBT) power modules are, besides defects in the substrate or the potting gel, the main reason for partial discharge. These critical electric field strengths occur at the energized contact where it is bordered by the insulating ceramic and the cover (mostly silicone gel). The reduction of high electric field strengths for increasing the threshold voltage for partial discharge has been studied in several publications based on experiments as well as on simulations. Simulations allow the localization of the critical spots and the quantification of the maximum electric field strength. However, a systematic study of the singularities of the electric field strength at the sharp edges is lacking. Such singularities are investigated in this article. The calculation of an absolute electric field strength value is only possible for finite edge radii. For sharp edges, however, the maximum electric field strength returned by simulation depends on the grid size: Through the finite grid size a virtual edge radius is induced that suppresses the singularity at the edge. To get around this problem, a mesh-independent evaluation procedure is introduced. With this procedure it is possible to quantitatively evaluate the electric field strength in the vicinity of the sharp edge. As an example, the influence of the offset between the top and bottom metallization layer on the maximum electric field strength is studied. Moreover, the influence of the thickness of the involved layers and of the shape of the electrodes is discussed. Also, the impact of the material properties of the involved dielectrics is examined. In addition to electrostatic simulations we have carried out electric transient simulations, which show that the ratio of the conductivities of the involved dielectric materials plays a major role for determining the maximum electric field strength.

Improved Thermal Performance of SOI Using a Compound Buried Layer

The buried oxide (BOX) layer in silicon on insulator (SOI) was replaced by a compound buried layer (CBL) containing layers of ${\rm SiO}_{2}$ , polycrystalline silicon (polysilicon), and ${\rm SiO}_{2}$ . The undoped polysilicon in the CBL acted as a dielectric with a higher thermal conductivity than ${\rm SiO}_{2}$ . CBL provides a reduced thermal resistance with the same equivalent oxide thickness as a standard ${\rm SiO}_{2}$ buried layer. Thermal resistance was further reduced by lateral heat flow through the polysilicon. Reduction in thermal resistance by up to 68% was observed, dependent on polysilicon thickness. CBL SOI substrates were designed and manufactured to achieve a 40% reduction in thermal resistance compared with an 1.0- $\mu{\rm m}~{\rm SiO}_{2}$ BOX. Power bipolar transistors with an active silicon layer thickness of 13.5 $\mu{\rm m}$ manufactured on CBL SOI substrates showed a 5%–17% reduction in thermal resistance compared with the standard SOI. This reduction was dependent on transistor layout geometry. Between 65% and 90% of the heat flow from these power transistors is laterally through the thick active silicon layer. Analysis confirmed that CBL SOI provided a 40% reduction in the vertical path thermal resistance. Devices employing thinner active silicon layers will achieve the greater benefit from reduction in vertical path thermal resistance offered by CBL SOI.

Study of Bonding Wire Failure Effects on External Measurable Signals of IGBT Module

The relationship between bonding wire liftoff and terminal voltage in insulated gate bipolar transistor (IGBT) power module is studied. Bonding wire liftoff failure is one of the most dominant limiting factors to the reliability behavior of IGBT power module. In this paper, in order to monitor this type of fault, the effects of the typical degradations are considered. The parasitic inductance and gate equivalent capacitance of IGBT module change due to bonding wire liftoff, which have different impacts on the external characteristics. So, two aspects of IGBT module terminal characteristics are investigated to identify any measurable signature used for monitoring bond wire liftoff failures: 1) gate-emitter voltage during turn-on process and 2) collector-emitter voltage during turn-off process. This paper aims to provide useful information for further development in monitoring the health of IGBT module.

Boron Ion Interaction with pnp Bipolar Power Transistor and Displacement Damage Effects on its Electrical Characteristics

Bipolar junction transistors used in switching and amplification applications is examined for their electrical performance after irradiation with 60 MeV boron ions of different fluence. Unirradiated device base current is 5.97×10-5 A while it is 9.03×10-4 A after irradiation with a fluence of 1×1012 ions/cm2. For unirradiated device collector current is 1.22×10-3 A and is 7.31×10-4 A after irradiation to a fluence of 1×1012 ions/cm2. Base current increases whereas collector current decreases after irradiation with a fluence of 1×1012 ions/cm2. The magnitude of decrease in collector current is approximately same as that of the increase in base current, showing the leakage of the collector current due to irradiation. The output collector gain of the unirradiated transistor is 20.5 after irradiation to a fluence of 1×1012 ions/cm2 it has reduced to 0.81. The capacitance measurements for base-emitter junction show that for the unirradiated and irradiated samples, linearity of the curves indicate uniformity of shallow doping concentration. The built in potential (Vbi) for unirradiated device is 2.69V and after irradiation it is 2.52V. The device is also studied for activation energy, trap concentration and capture cross-section of deep levels are studied using deep-level transient spectroscopy (DLTS) technique. Majority carrier trap level is observed with energy Ev+0.784eV.

In Situ Diagnostics and Prognostics of Wire Bonding Faults in IGBT Modules for Electric Vehicle Drives

This paper presents a diagnostic and prognostic condition monitoring method for insulated-gate bipolar transistor (IGBT) power modules for use primarily in electric vehicle applications. The wire-bond-related failure, one of the most commonly observed packaging failures, is investigated by analytical and experimental methods using the on-state voltage drop as a failure indicator. A sophisticated test bench is developed to generate and apply the required current/power pulses to the device under test. The proposed method is capable of detecting small changes in the failure indicators of the IGBTs and freewheeling diodes and its effectiveness is validated experimentally. The novelty of the work lies in the accurate online testing capacity for diagnostics and prognostics of the power module with a focus on the wire bonding faults, by injecting external currents into the power unit during the idle time. Test results show that the IGBT may sustain a loss of half the bond wires before the impending fault becomes catastrophic. The measurement circuitry can be embedded in the IGBT drive circuits and the measurements can be performed in situ when the electric vehicle stops in stop-and-go, red light traffic conditions, or during routine servicing.

Bipolar-power-transistor-based limiter for high frequency ultrasound imaging systems

High performance limiters are described in this paper for applications in high frequency ultrasound imaging systems. Limiters protect the ultrasound receiver from the high voltage (HV) spikes produced by the transmitter. We present a new bipolar power transistor (BPT) configuration and compare its design and performance to a diode limiter used in traditional ultrasound research and one commercially available limiter. Limiter performance depends greatly on the insertion loss (IL), total harmonic distortion (THD) and response time (RT), each of which will be evaluated in all the limiters. The results indicated that, compared with commercial limiter, BPT-based limiter had less IL (−7.7dB), THD (−74.6dB) and lower RT (43ns) at 100MHz. To evaluate the capability of these limiters, they were connected to a 100MHz single element transducer and a two-way pulse-echo test was performed. It was found that the −6dB bandwidth and sensitivity of the transducer using BPT-based limiter were better than those of the commercial limiter by 22% and 140%, respectively. Compared to the commercial limiter, BPT-based limiter is shown to be capable of minimizing signal attenuation, RT and THD at high frequencies and is thus suited for high frequency ultrasound applications.

Implementation of a High Reliability IGBT Power Device

The insulating-gate bipolar transistor, IGBT, is a power component which is developed in the medium power and medium frequency. It inherently integrates the structures of a power bipolar transistor and a power MOSFET, and then it has better performance in many applications. Advantages of this device are the high current density, the outstanding breakdown voltage, as well as the excellent operating frequency and so on. And, it might make up the shortcoming of MOSFETs or BJTs utilized separately. In this paper, a smart IGBT device is developed by using the semiconductor process and device simulation tools. Therefore, a relationship between the depth of drift region, doping concentration, and breakdown voltage in an IGBT will be investigated in this work. Eventually, this device will be with the 200V breakdown voltage and 20A on-state driving current capability. Meanwhile, the ESD and latch-up (LU) protection structures will be accomplished in this study.

Nickel–Tin Transient Liquid Phase Bonding Toward High-Temperature Operational Power Electronics in Electrified Vehicles

This paper presents the concept, fabrication, and evaluation for quality and reliability of nickel-tin transient liquid phase (Ni-Sn TLP) bonding that provides high reliability for high-temperature operational power electronics in electrified vehicles. The need for automotive power electronics to operate at high-temperature presents significant challenges in terms of packaging and bonding technology used. TLP bonding is one attachment approach that addresses these challenges and facilitates high remelting temperatures while allowing processing to occur at relatively low temperatures and pressures. In particular, the Ni-Sn TLP bonding process exhibits a number of desirable characteristics for power electronics, including popularity in conventional power electronics, low cost, and uniform and homogeneous alloy formation. The work herein presents Ni-Sn TLP bonding (ready for high-temperature operation) as applied to silicon power devices of relatively large size (12 mm × 9 mm). The quality and reliability of the developed bonding process was characterized using material, optical, and electrical analysis. Analysis indicates that the resulting bondline is uniformly composed of Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> alloy throughout the bond area. This bonding approach has exhibited excellent reliability for bonded devices after thermal cycling from -40°C to 200°C. Electrical properties of the bonded insulated gate bipolar transistor power devices demonstrated that Ni-Sn TLP bonding exhibits electrical performance comparable with conventional solder and is reliable at high-temperature operation.

Hybrid Solid- and Liquid-Cooling Solution for Isothermalization of Insulated Gate Bipolar Transistor Power Electronic Devices

Rapid increases in the power ratings and continuing miniaturization of power electronic devices have pushed chip heat fluxes well beyond the range of conventional thermal management techniques. The heat flux of power electronic devices for hybrid electric vehicles is currently at the level of 100-200 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and is projected to increase to 500 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in next generation vehicles. Such high heat fluxes lead to higher and less uniform insulated gate bipolar transistor (IGBT) chip temperature and significantly degrade the device performance and system reliability. Maintaining the maximum temperature below a specified limit, while isothermalizing the surface temperature of the chip, has become a critical issue for thermal management of power electronics. In this paper, a hybrid solid- and liquid-cooling system design, which combines cold plate liquid cooling and TE solid-state cooling, is proposed for thermal management of a 10 × 10 mm IGBT chip. The liquid-cooling cold plate is used for global cooling of the entire IGBT module while the embedded thin-film TE cooler (TEC) is employed for isothermalization of the individual IGBT chip. A detailed package-level 3-D thermal model is developed to explore the potential application of this cooling concept, with the primary attention focused on isothermalization and temperature reduction of IGBT chip associated with variations in TEC sizes, TE materials, applied current on TEC, cooling system designs, working fluid temperature, cold plate cooling capacity, and IGBT chip heat flux. The results demonstrate that the hybrid solid and liquid cooling is a very promising thermal management solution that can eliminate more than 90% of the temperature nonuniformity on the IGBT chip.

Enhanced Thermal Performance of InGaP/GaAs Collector-Up HBTs With a Miniaturized Backside Heat-Dissipation Structure

A miniaturized heat-dissipation structure is developed to reduce the operating temperature of power bipolar transistors to favorable levels, while maintaining a configuration size that is compact enough for high-efficiency operation. By placing the thermal-removal packaging at the backside of the collector-up heterojunction bipolar transistor and through the appropriate finger-pitch arrangement of the packaging design, which displays noticeable enhancement in terms of thermal management, significant reduction in the surface temperature rise is demonstrated on devices composed of the InGaP/GaAs material system. A factor of over 20 shrinkages of the consumed chip area and a 10-fold reduction in mutual heating is observed. At levels of power density up to 1.2 mW/μm2, a power-added efficiency greater than 50% is attained for the wireless cellular power amplifier application.

An Integrated Electrothermal Design Primer Using an SiGe HBT PA [Application Notes

The integrated design flow that links simulation, layout, and electromagnetic (EM) analysis is the foundation for modern RF/microwave integrated circuit (IC) design. The inclusion of thermal simulation in this flow is now possible with modern thermal solvers linked into RF/microwave integrated design tools. Silicon germanium (SiGe) heterojunction bipolar transistor (HBT) power amplifier (PA) design is used as an example where such a flow is most beneficial due to numerous issues such as array sizing and thermal runaway. An electrothermal flow is discussed relative to some overall metrics for design flows and that incorporates the availability of an integrated thermal solver into the earliest parts of, and potentially throughout, the entire design flow. The result is a flow that potentially reduces iterations during the design process and boosts design performance by freeing up margin.

Incident particle range dependence of radiation damage in a power bipolar junction transistor

The characteristic degradations in silicon NPN bipolar junction transistors (BJTs) of type 3DD155 are examined under the irradiations of 25-MeV carbon (C), 40-MeV silicon (Si), and 40-MeV chlorine (Cl) ions respectively. Different electrical parameters are measured in-situ during the exposure of heavy ions. The experimental data shows that the changes in the reciprocal of the gain variation (Δ(1/β)) of 3DD155 transistors irradiated respectively by 25-MeV C, 40-MeV Si, and 40-MeV Cl ions each present a nonlinear behaviour at a low fluence and a linear response at a high fluence. The Δ(1/β) of 3DD155 BJT irradiated by 25-MeV C ions is greatest at a given fluence, a little smaller when the device is irradiated by 40-MeV Si ions, and smallest in the case of the 40-MeV Cl ions irradiation. The measured and calculated results clearly show that the range of heavy ions in the base region of BJT affects the level of radiation damage.

The Performance and Analysis of an Efficient Model of DC to DC Converter for on Chip Circuitry using a Less Number of Power Devices

This paper presents an efficient DC to DC converter for on chip circuitry which gives high-energy conversion quality using CMOS Driver-Receiver Pair for Low-Swing Signaling. The efficiency has increased due to the use of power FETs, which are able to switch at high frequency more efficiently than power bipolar transistors, which incur more switching losses and require a more complicated drive circuit. The proposed schemes perform better than the other schemes in terms of power consumption, delay, and energy delay product. Moreover, the proposed scheme requires no reference voltages, and multiple threshold voltage processes. In addition the other key advantages of the proposed signaling schemes is that they require only one power supply and threshold voltage, hence significantly reducing the design complexity. This proposed work also takes care of the relative reliability benefits of the proposed signaling techniques through a signal-to-noise ratio (SNR) analysis.