The recently introduced 650V XPT IGBT has been designed using planar technology with improved methods to reduce inherent parasitic resistance. The resulting devices offer performance similar to modern trench field-stop devices without the negative effects of trench devices, such as high input capacitance and resulting high turn-on and turn-off gate currents.
The absence of a lifetime control process ensures a positive temperature coefficient at the conduction voltage to facilitate parallel connection. With an optimized emitter design, these 650V XPT IGBTs meet the demands of fast switching performance.
Figure 1 shows a Vce(sat) - Eoff compensation curve for a 650V XPT IGBT in medium- and high-speed versions.
XPT Characteristics:
The XPT IGBT was designed to provide low switching losses while maintaining a low on-state voltage. This was achieved by improving SOA and short-circuit robustness ratios. The output characteristics at different temperatures are shown in Figure 2 for average speed.
The XPT IGBT has a typical low Vce(sat) of1.6V@Inom, 25°C and1.85V@Inom, 150°C. The positive temperature coefficient of the XPT IGBT provides negative feedback, making it suitable for parallel assembly of modules or circuits. In addition to the low Vce(sat), the XPT IGBT also has low cutoff current leakage at 150°C (<100mA@650V), where the maximum junction temperature is specified at 175°C.
The switching characteristics of a 650V XPT IGBT at 150°C, 100 A, medium speed are shown in Figures 3 and 4.
As can be seen in Figure 3, the current waveform (in blue) exhibits smooth switching behavior, reducing EMI and with low overvoltage transients. The linear voltage rise and short current tail during shutdown result in small losses (Eoff = 3.6mJ @ 150°C, 300 V, 100 A).
The XPT IGBT has a low gate load (Qg = 140nC@0/15 V), which requires less gate control power consumption, compared to trench IGBTs.
XPT and SONIC - the perfect combination
The optimal combination for reducing ignition losses is achieved when the XPT IGBT is paired with the IXYS SONIC diode, which also has low power conduction with excellent temperature behavior.
The SONIC diode has smooth recovery characteristics, allowing the XPT IGBT to remain on at very high di/dt values, even under low current and temperature conditions where diode popping would typically occur.
The SONIC diode maintains smooth switching behavior during turn-off at unsuitable currents, reducing EMI issues.
SONIC diodes combine a low reverse recovery current with a short reverse recovery time, as shown in Figure 4, to minimize the turn-on energy of the XPT IGBT (Eon IGBT=1.2mJ@150°C300V, 100A@1600A/ms ). The Vf of the Sonic diode is less sensitive to temperature, resulting in better suitability for parallel operation of the diodes and minimizing switching losses.
XPT Robustness Features
The behavior of IGBTs under short-circuit conditions is a critical issue for motor control applications, and the IXYS XPT IGBT has demonstrated exceptionally robust performance during short-circuit testing. The chip design has been optimized to provide a short-circuit current approximately four times the rated current, ensuring robust short-circuit behavior.
Figure 5 shows the XPT 50A, 650V, medium-speed IGBT during a short circuit with a gate voltage of +/-15V at 150°C for 10ms at a 400V bus voltage.
Characterization of the XPT IGBT technology demonstrated extreme robustness during device short-circuiting under high voltages and temperatures for 10 ms, without compromising the IGBT's characteristics. The IXYS XPT IGBT has an RBSOA at 650V up to twice the nominal current at a junction temperature of 150°C.
XPT Roadmap
: The XPT 650V IGBT is planned with current ratings of 10, 15, 20, 30, 50, 75, 100, and 200A as a medium-speed type for motor control applications and as a fast-switching version for fast-switching applications such as solar inverters and welding machines. The 50A and 100A chip versions are being launched first and are already available as samples. (A combination with SiC is also offered for special applications and customer requirements.)
Encapsulation options, new Isoplus-SMPD™
These XPT™ IGBT chips are available in standard discrete module packages and the new Isoplus-SMPD™ (surface-mount power device). The goal was to develop a small package with high flexibility for forming different circuits based on IXYS ISOPLUS™ technology. Application requirements and design details were discussed and analyzed in conjunction with the development team at SEW Eurodrive GmbH & Co.KG to arrive at a product that is better suited for more effective use.
The ISOPLUS™ family is based on the use of a DCB substrate, providing insulation to the back. This reduces assembly effort, as a separate insulation layer is not required. The transfer molding technique creates a robust device body and allows the use of a thin 0.38 mm DCB, further reducing thermal resistance.
In standard discrete components, the dies are soldered directly onto a copper base with different coefficients of thermal expansion, especially between the copper base and the chip. Large temperature variations, whether caused by temperature or power stress, can introduce defects such as cracks in the chips.
This stress is significantly reduced by the benefits of the Isoplus-SMPD™ package, from improved compatibility between the silicon chip and the DCB (Digital Circuit Board) where the chip is mounted. Furthermore, the low thermal impedance of the DCBs leads to minimal temperature rise under varying loads, allowing them to withstand stress at low temperatures, which is characteristic of a highly reliable device. The use of a DCB also enables the implementation of various low-inductance circuit configurations within the package. Standard configurations such as phase-legs, chopper circuits, and rectifier bridges with single and three input phases are already available, among others, using 1200V XPT IGBTs (Figure 6). Other configurations will be developed based on customer requirements. Building upon these sub-functions, it is possible to create more complex power circuits tailored to specific application needs. And, of course, these devices can be connected in parallel for higher currents. For the 650V XPT IGBT, a 75A phase-leg configuration and a 200A single copack are feasible in Isoplus-SMPD™.
The new package is small and lightweight, with two rows of pins, resembling an integrated circuit (IC) but with less copper content and improved leakage distance. It allows for board mounting on standard SMD pick-and-place equipment, alongside other standard SMD components. Isoplus-SMPD™ devices are available in either tape and reel or blister tray packaging.
The entire board, including the power components, can be assembled using a standard SMD soldering process. As always, a layer of thermal interface material must be applied to the back of the power devices (or alternatively, to the heatsink surface) for these devices as well. The devices can then be mounted to the heatsink along with the PCB.
Dividing the functions of an integrated module solution into smaller units also offers advantages in terms of heat dissipation. While heat dissipation in a module solution is concentrated in a relatively small area, the heat sources are separated and therefore much better distributed across the heatsink(s) using ISOPLUSSMPD™ devices.
These power devices must be pressed against the heatsink to ensure low thermal resistances. Pressure can be applied in various ways, for example, with a mounting clip, or by applying pressure through the board directly onto the power device. Measurements have shown that high pressures reduce the thermal resistance (RthJH), and also show that it remains almost the same if the mounting force is reduced after a short period of time with higher pressure (Figure 7). However, even with lower mounting forces, the Rth improves over time. It takes about 30 minutes for the paste to be thoroughly distributed and settled, and for any excess paste to be expelled.
Conclusion:
Good static and dynamic characteristics combined with robustness under short-circuit and avalanche conditions, along with the 3 kV insulation characteristics and SMD process capability of the ISOPLUSSMPD™ package, provide the engineer with a suitable and more flexible device for advanced system power designs with excellent performance, reliability, and cost reduction.
Author: Iain Imrie, Elmar Wisotzki, Olaf Zschieschang and Andreas Laschek-Enders. IXYS.
