SKiM® - Technical Explanations ® SKiM 63/93 IGBT Modules Technical Explanations Version 1.51 / October 2013 Stefan Häuser 1 © by SEMIKRON SKiM® - Technical Explanations Content 1 Introduction ...................................................................................................................................... 3 1.1 Features ................................................................................................................................... 3 1.2 Advantages and Benefits ......................................................................................................... 3 2 Technical Details of SKiM ................................................................................................................ 5 2.1 Mechanical Design .................................................................................................................. 5 2.2 Electrical Behaviour ................................................................................................................. 6 2.3 Sinter Process ......................................................................................................................... 8 2.4 Protected Springs .................................................................................................................... 9 2.5 Creepage and Clearance Distances ....................................................................................... 9 2.6 Isolation Measurement .......................................................................................................... 10 2.7 Chip Positions ........................................................................................................................ 11 2.8 Thermal Material Data ........................................................................................................... 12 2.9 Pressure Force on the Heat Sink .......................................................................................... 13 3 Chip Technologies and Product Ranges ....................................................................................... 14 3.1 IGBT Chip Technologies and Product Range ....................................................................... 14 3.2 Safe Operating Area for IGBTs ............................................................................................. 16 3.3 Surge Current Characteristics of CAL Diodes ....................................................................... 17 3.4 Selection Guide ..................................................................................................................... 17 4 Thermal Resistances ..................................................................................................................... 18 4.1 Measuring Thermal Resistance Rth(j-s) ................................................................................... 18 4.2 Transient Thermal Impedance ............................................................................................... 18 5 Integrated Temperature Sensor Specifications ............................................................................. 20 5.1 Electrical Characteristic ......................................................................................................... 20 5.2 Electrical Isolation .................................................................................................................. 22 6 Spring Contact System Specifications........................................................................................... 23 6.1 Spring and Contact Specifications......................................................................................... 23 6.2 PCB Specifications (Landing Pads for Springs) .................................................................... 23 6.3 Storage Conditions ................................................................................................................ 23 6.4 Stray Inductance of Contact Springs ..................................................................................... 24 7 Reliability ....................................................................................................................................... 26 7.1 Standard Tests for the Qualification of SKiM Modules .......................................................... 26 7.2 Reliability of Spring Contacts................................................................................................. 27 7.3 Reliability of SKiNTER Layer ................................................................................................. 28 8 Design Recommendations for SKiM ............................................................................................. 30 8.1 Printed Circuit Board Design ................................................................................................. 30 8.2 Paralleling SKiM IGBT Modules ............................................................................................ 33 8.3 DC Link Bus Bars, Snubber Capacitors ................................................................................ 35 9 Marking .......................................................................................................................................... 36 9.1 “Passed” marking on housing ................................................................................................ 36 9.2 Laser Marking for Modules .................................................................................................... 36 9.3 Data Matrix Code ................................................................................................................... 37 10 Bill of Materials .......................................................................................................................... 38 11 Packing Specifications ............................................................................................................... 39 11.1 ESD COVER.......................................................................................................................... 39 11.2 Packing Boxes ....................................................................................................................... 40 11.3 Marking of Packing Boxes ..................................................................................................... 40 12 Type Designation System .......................................................................................................... 42 13 Figure Captions in the Datasheets ............................................................................................ 43 14 Disclaimer .................................................................................................................................. 43 2 © by SEMIKRON SKiM® - Technical Explanations 1 Introduction SKiM was introduced at PCIM Europe 2007 as SEMIKRON’s new product line for highly reliable IGBT modules made specifically for automotive applications. SKiM is available in two package sizes: SKiM 63 (cf. Fig. 1-1) and SKiM 93 (Fig. 1-2). 1.1 Features Fig. 1-1 SKiM 63 (Foot print = 120 x 160 mm²) Fig. 1-2 SKiM 93 (Foot print = 150 x 160 mm²) SKiM modules feature a pressure-contact low-profile housing that boasts the following advantages: 100 % solder-free module, Pb-free Solder-free driver assembly with no additional wiring or connectors Spring contacts for auxiliary contacts Separate AC, DC terminals and control unit 17 mm main terminal height 1.2 Advantages and Benefits The chips inside SKiM modules are sintered not soldered, thereby achieving a very high power cycling capability. Fig. 1-3 shows the comparison between a SKiM and a standard soldered module. The sinter joint is a thin silver layer whose thermal resistance is superior to that of a soldered joint. Due to the high melting point of silver (960 °C), no joining fatigue occurs, resulting in an increased service life. Cycles to failure SKiM: No base plate Solder-free pressure contacts 10 000 1000 Standard module: With base plate Solder contacts 100 100 Δ Temperatutre [K] Fig. 1-3 Comparison between SKiM and standard soldered module with base plate 3 © by SEMIKRON SKiM® - Technical Explanations The above-mentioned features allow for a compact, flat and low-inductance inverter design. Direct driver assembly provides optimum IGBT controllability and eliminates noise on gate wires or loose connectors. For further information on SKiM please refer to: P. Beckedahl, T. Grasshoff und M. Lederer; A new power module concept for automotive applications; PCIM Nuremberg; May 2007 C. Daucher; 100% solder-free IGBT Module; PCIM Nuremberg; May 2007 4 © by SEMIKRON SKiM® - Technical Explanations 2 Technical Details of SKiM The SKiM module is designed as a highly reliable module that meets the demands of automotive applications in terms of shock and vibration stability, as well as high temperature capability and service life. Today, state-of-the-art IGBT modules are based on a solder construction: the chips are soldered to a substrate and this substrate is soldered to a base plate. Investigations have shown, however, that these solder layers constitute the weakness of any module since they demonstrate fatigue when exposed to active and passive temperature cycling. In a consequence, SEMIKRON eliminates solder joints. A strategy that has been pursued by SEMIKRON since 1992 when SKiiP technology was first introduced: the first pressure-contact IGBT power module with pressure-contact main terminals and no base plate. SKiM modules from SEMIKRON are the first ever 100% solder-free IGBT modules. 2.1 Mechanical Design SKiM (Fig. 2-1) is based on the well-established SKiiP technology. This means the Al2O3 DBC (direct bonded copper) substrate is pressed directly onto the heat sink without the use of a base plate. Pressure Part Chip No base plate Terminal Springs to driver Sintered Direct contact to heat sink Pressure contact Pressure contact Fig. 2-1 Cross-sectional picture of SKiM 63 The pressure is induced by a pressure part on top, which is screwed to the heat sink. This pressure is transferred to the three main terminals (plus, minus and AC), as shown in Fig. 2-2. These main terminals constitute a low-inductance sandwich construction and transfer the pressure to the abovementioned DBC substrate. The pressure is applied across several contact points (cf. Fig. 2-3) beside every single chip. As a result, a very low thermal and ohmic resistance RCC’+EE’ is achieved. 5 © by SEMIKRON SKiM® - Technical Explanations = Pressure points of main terminals Fig. 2-2 “Sandwich” of main terminals (SKiM 63) Fig. 2-3 DBC substrate with pressure points (SKiM 63) The chips themselves are sintered, not soldered. The sintering is based on pulverised silver which forms a material connection when pressure and temperature is applied. (cf. section 2.3) Contact springs are used for all of the auxiliary contacts (gate, auxiliary emitter and temperature sensor). These spring contacts allow for solder-free connection of the driver PCB. 2.2 Electrical Behaviour In a high-power module with paralleled chips, the switching behaviour and the resulting derating is important. Current Distribution The current distribution between silicon chips is affected mainly by the parasitic stray inductances and the difference in these inductances between the chips Two design features influence these parasitic stray inductances: first the layout of the chips on the substrate and hence the commutation behaviour between IGBT and diode; second the internal design of the main terminals. Influence of the chip distribution on the DBC If the DBC layout is not symmetric (e.g. as shown in Fig. 2-4) the commutation paths of the different currents have different parasitic inductances, leading to different currents, losses and, ultimately, temperatures in the different chips (cf. Fig. 2-5). To prevent individual chips from overheating, derating is necessary. 300.0 IC [A] 250.0 200.0 150.0 100.0 50.0 0 Eswitch(T2) = 105 % Eswitch(T1) 4.500u 5.000u 5.500u 6.000u 6.500u 7.000u t [s] Fig. 2-4 Schematic of non-symmetric chip distribution on DBC substrate 6 Fig. 2-5 Simulated current overshoots during commutation as caused by non-symmetric layout © by SEMIKRON SKiM® - Technical Explanations The SKiM DBC layout (Fig. 2-3) is largely symmetric and has symmetric inductances in the current paths (Fig. 2-6). The commutation behaviour across all chips is therefore very even (Fig. 2-7) and derating is not necessary. 300.0 IC [A] 250.0 200.0 150.0 100.0 50.0 0 Eswitch(T2) = Eswitch(T1) 4.500u 5.000u 5.500u 6.000u 6.500u 7.000ut [s] Fig. 2-6 Schematic of symmetric chip distribution on SKiM DBC substrate Fig. 2-7 Simulated current overshoots during commutation Influence of the internal main terminal design The bus bar system in SKiM modules, as shown in Fig. 2-2, has a very low stray inductance (LCE < 10 nH). Every single chip is connected symmetrically (cf. Fig. 2-3). This leads to similar stray inductances for the individual chips, resulting in a homogeneous current distribution. Measurements (Fig. 2-8) have verified a homogenous internal current distribution. The voltage drop across a single chip is an indicator for the current through this chip. In Fig. 2-8, it can be seen that the voltage drops at three different chip positions on the substrate, as well as at the position of the auxiliary emitter are nearly identical, indicating a very homogenous current distribution. There is a difference between the internal voltages and the current at the outer +/- terminals, resulting from the voltage drop between the chips positions and the main terminals. VCE IC 150 V/Div; 80 A/Div Fig. 2-8 Switch-off behaviour of SKiM 93 module, measured at different points directly on the DBC substrate Comparison: Top versus Bottom IGBT 7 © by SEMIKRON SKiM® - Technical Explanations Besides even current distribution between paralleled chips, the symmetry in switching between top and bottom IGBT in a half bridge configuration is also important in terms of derating. This means if the two IGBTs switch differently, the IGBT with higher losses will limit the module as a whole. Thanks to the symmetric DBC layout in SKiM modules (cf. Fig. 2-3, Fig. 2-9 and Fig. 2-11), the switching behaviour of the bottom and the top IGBT is virtually identical, as shown in Fig. 2-10 and Fig. 2-12. Derating is therefore not necessary. IC VCE VGE Fig. 2-9 Schematic of bottom IGBT on SKiM DBC Fig. 2-10 Measured turn-off of bottom IGBT IC - VCE Fig. 2-11 Schematic of top IGBT on SKiM DBC Fig. 2-12 Measured turn-off of top IGBT For further information on optimisations in SKiM processes, please refer to: A.Wintrich, P. Beckedahl, T.Wurm ; “Electrical and thermal optimization of an automotive power module family”; Proceedings Automotive Power Electronics; Paris; October 2007 2.3 Sinter Process For the SKiM product line SEMIKRON improved the sinter process for silver powder to enable it to be used in series production. This “SKiNTER” process replaces chip soldering and results in very high degree of joint reliability. The SKiNTER process works as follows: the silver powder is printed to the DBC substrate. Then the chips are placed onto this silver layer. The joint is created by applying heat (< 250°C) and pressure. Though the SKiNTER process temperature is far below the melting point of silver (960 °C), the final joint is stable up to this temperature. 8 © by SEMIKRON SKiM® - Technical Explanations The following table Tab. 2-1 shows a comparison between the SKiNTER process and soldering. Joining temperature Layer thickness Formation of voids Connection layer Melting temperature Thermal conductivity Electrical conductivity Coefficient of thermal expansion Tensile strength SKiNTER process < 250°C 15 – 20 µm no homogeneous 960 °C 240 W/(m·K) 41 m/(Ω·mm²) -6 19 10 m/K 55 MPa Soldering 200 – 380°C typical 70 – 150 µm possible inhomogeneous < 380 °C 70 W/(m·K) 8 m/(Ω·mm²) -6 28 10 m/K 30 MPa Tab. 2-1 Comparison between sintering and soldering For further information on the SKiNTER process, please refer to: C. Göbl, P. Beckedahl, H. Braml ; “Low temperature sinter technology Die attachment for automotive power electronic applications”; Automotive Power Electronics; June 2006 2.4 Protected Springs When the SKiM is not mounted to the heat sink and the pressure part is not pressed down, the springs for the auxiliary contacts are protected inside the module (Fig. 2-13). Fig. 2-14 shows a SKiM module after mounting. The pressure part is pressed down and the spring heads appear at the surface. Fig. 2-13 SKiM 93: before mounting the auxiliary springs are invisible Fig. 2-14 SKiM: the springs appear after mounting. 2.5 Creepage and Clearance Distances All SKiM IGBT modules comply with the mandatory creepage and clearance distances in accordance with EN 50178 for Grid voltage = 690 V, line to line, grounded delta Nominal voltage = 1700 V (DC link voltage = 1250 V) Basic isolation Pollution degree 2 Comparative Tracking Index “CTI” value of the case < 400 9 © by SEMIKRON SKiM® - Technical Explanations The following values are complied with: Creepage distance from main terminal to main terminal ≥ 14 mm Clearance distance from main terminal to main terminal ≥ 5,8 mm Creepage distance from any terminal to heat sink potential ≥ 8,3 mm Clearance distance from any terminal to heat sink potential ≥ 8.0 mm Creepage distance on the PCB from landing pad to landing pad ≥ 6.3 mm Tab. 2-2 Creepage and clearance distances for SKiM “From terminal to terminal” means for main and auxiliary terminals between high-voltage potentials, not between terminals with small differences in voltage potential, e.g. gate and emitter contacts (± 20 V) or between the contacts for the temperature sensor. In the case of “1700 V applications” SEMIKRON recommends the use of “low profile screws” with a maximum screw head height of 2.8 mm. For 1200 V all of the distances are met with standard screws (4 mm head height) as given in the mounting instructions. The following sketches (Fig. 2-15 and Fig. 2-16) show the distances without screws. Inside the housing, the DBC substrate is coated with a silicone gel for electrical isolation. The gel has an isolation capability > 20 kV/mm. Spring contacts Mounting dome PCB Pressure part Clearance = 12 mm without screw Fig. 2-15 Clearance from main terminals to heat sink potential Clearance = 11.3 mm without screw Fig. 2-16 Clearance from PCB to heat sink potential 2.6 Isolation Measurement The specified isolation voltage is given in the data sheets. In the course of production, this isolation voltage is verified with a 100% test according to the DIN EN 50178 standard (VDE 0160). The isolation measurement is performed in two steps: During the first measurement all main and auxiliary terminals (including main, auxiliary emitter, gate and temperature sensor contacts) are short circuited and measured against the base plate. In the second measurement stage the main and auxiliary terminals (including main, auxiliary emitter, gate contacts) are short circuited, as are the base plate and the temperature sensor contacts. The voltage Vmeasurement is then applied between these two circuits. 10 © by SEMIKRON SKiM® - Technical Explanations 2.7 Chip Positions For detailed temperature measurements the exact positions of the chips have to be known. Inside SKiM modules, the chips are always located in the same positions, regardless of the chip size. The drawings Fig. 2-20 and Fig. 2-21 show the chip positions measured from the centre of the bottom left screw hole. Fig. 2-17 IGBT Chips Fig. 2-18 Diode Chip Fig. 2-19 Temperature Sensor Fig. 2-20 Chip positions in SKiM 63 11 © by SEMIKRON SKiM® - Technical Explanations Fig. 2-21 Chip positions in SKiM 93 2.8 Thermal Material Data For thermal simulations it is necessary to have the thermal material parameter, as well as the typical thickness of the different layers in the package. This data is given in Tab. 2-3. For better understanding, the sketch in Fig. 2-22 shows the different layers in the package. Chip (IGBT, diode) SKiNTER layer DBC copper DBC ceramic DBC copper Thermal paste Heat sink Fig. 2-22 Sketch of SKiM package, cross-sectional view 12 © by SEMIKRON SKiM® - Technical Explanations Layer Material Layer thickness Spec. thermal conductivity Spec. thermal capacity Density [mm] [W/m/K] [J/kg/K] [kg/m ] 3 IGBT chip (“066”) Si 0.07 124 750 2330 IGBT chip (“E4”) Si 0.14 124 750 2330 IGBT chip (“17”) Si 0.19 124 750 2330 Diode chip Si 0.24 124 750 2330 Chip joint Ag-sinter layer ~ 0.02 250 230 7350 DBC copper Cu 0.30 390 390 8960 DBC ceramic Al2O3 0.38 24 830 3780 DBC copper Cu 0.30 390 390 8960 Thermal paste Customer-specific 0.25 Heat sink Customer-specific Tab. 2-3 Material data for thermal simulations 2.9 Pressure Force on the Heat Sink For the heat sink design it may be necessary to know what force is applied by the SKiM module. This information is given in Tab. 2-4. The sketch in Fig. 2-23 shows how the values in Tab. 2-4 are to be understood. Pressure stress per half bridge [N/mm²] SKiM 63 1.06 SKiM 93 1.27 Tab. 2-4 Pressure forces produced by SKiM modules Given data applies to one half bridge = 1/3 of a SKiM Fig. 2-23 Sketch of SKiM 63, bottom view 13 © by SEMIKRON SKiM® - Technical Explanations 3 Chip Technologies and Product Ranges 3.1 IGBT Chip Technologies and Product Range SKiM IGBT modules are available with 600 V, 1200 V and 1700 V IGBTs. Design Principles IGBT chips are based on two different main design principles. The first is related to the gate structure: trench or planar gate, while the second relates to the IGBT technology used: punch through (“PT”) or non-punch through (“NPT”). The planar gate is a cost-effective structure based on doping processes and produces a horizontal gate structure (Fig. 3-3). The sophisticated trench gate, in comparison, is based on a combination of doping, etching and filling processes. The trench process leads to a very efficient, vertical gate structure and allows for small chip sizes (Fig. 3-4), which in turn allow for compact module design. Despite this, the smaller chip sizes lead to higher thermal resistance at the same time. The term “Punch-Through” describes the shape of the electric field inside the IGBT during blocking + state. As shown in Fig. 3-1, the electric field punches through the n layer into the n layer. Inside the + n layer the field is steeper than in the n layer. Thanks to this, the PT-IGBT can be thinner than an NPT-IGBT (Fig. 3-2) and the overall losses are lower. In the past, PT-IGBTs were made of “epitaxial” material and had a negative temperature coefficient for the forward voltage drop VCE(sat), making paralleling very difficult. State-of-the-art “Soft-Punch Through” and “Field Stop” PT-IGBTs, however, have a positive temperature coefficient and allow for parallel use. G at e Em itte r Gate Emitter E E n n p p n- n- n+ p+ C o lle ct o r p+ x x Collector Fig. 3-1 Punch-Through IGBT (with planar gate) Fig. 3-2 Non-Punch Through IGBT (with planar gate) Trench IGBT rd SEMIKRON type designation: “066” for 600 V, “126” for 1200 V, “176” for 1700 V 3 th “IGBT3”, “12T4”, “12E4”, for the 1200 V 4 generation “IGBT4”. generation + The “Trench IGBT” chip design is based on a trench-gate structure combined with a “Field Stop” n th buffer layer for punch through feature, as shown in Fig. 3-4. With the introduction of the 4 generation, this general design was not changed, but the trade-off between the on-state losses VCE(sat) and the switching losses Eon+Eoff was optimised for operation with switching frequencies above 4 kHz. Furthermore, the “IGBT4” is able to operate with a maximum junction temperature T j,max = 175 °C. The increased Tj,max offers more flexibility in overload conditions or for applications with few temperature cycles (e.g. pumps or fans) where the junction temperature might now exceed the former limits. 14 © by SEMIKRON SKiM® - Technical Explanations Gate Emitter n p Gate n+ p n- n- n+ p+ n+ p+ Collector Fig. 3-3 IGBT with planar gate and “Soft Punch Through” technology Emitter Collector Fig. 3-4 IGBT with trench gate and “Field Stop” technology For further information on “IGBT4”, please refer to: R. Annacker, R. Herzer, IGBT4 Technology Improves Application Performance, Bodo´s Power Systems, Issue June 2007 A. Wintrich, IGBT4 and Freewheeling Diode CAL4 in IGBT Modules, SEMIKRON Application Note, AN- 7005, Nuremberg, 2008 Inverse and Freewheeling Diodes The free-wheeling diodes used in SKiM IGBT modules are specially optimized CAL (Controlled Axial Lifetime) diodes, or HD CAL (High Density CAL) diodes. These fast, "super soft" planar diodes are characterised by the optimal axial profile of the charge carrier life-time. This leads to: Low peak reverse current lowering the inrush current load on the IGBTs in bridge circuits. A "Soft" decrease in the reverse current across the entire operating temperature range, which minimizes switching surges and interference. A robust performance even when switching at high di/dt. Very good paralleling capability thanks to the negligible negative temperature coefficient and the small forward voltage VF spread. Compared with CAL diodes, HD CAL diodes display reduced forward voltages at negligible higher switching losses and an almost invariant forward voltage temperature coefficient. SEMIKRON’s newly developed “CAL4” diode is designed specifically for use with the “IGBT4” generation. This new device boasts low thermal losses and outstanding soft switching behaviour even at extreme commutation speeds. Further, the newly developed junction termination ensures safe operation up to 175 °C. For further information on CAL4, please refer to: V. Demuth et al., CAL 4: The Next-Generation 1200V Freewheeling Diode, Proceedings PCIM China, 2007 15 © by SEMIKRON SKiM® - Technical Explanations 3.2 Safe Operating Area for IGBTs Safe Operating Areas are not included in the datasheets. They are given as standardized figures. These figures apply to 600 V, 1200 V and 1700 V. Safe Operating Area IGBT modules must not be used in linear mode. 10 IC/ICRM SOA-SEMiX.xls Tc ≤ 25 °C Tj ≤ 150 °C single pulse tpulse = 0,1 ms 1,0 ms 10 ms 1 1/1 DC 0,1 1/10 0,01 1/100 0,001 0,001 0,01 1/100 0,1 1/10 VCE/V 10 CES 1 1/1 Fig. 3-5 Safe Operating Area (SOA) Reverse Bias Safe Operating Area The maximum VCES value must never be exceeded. Due to the internal stray inductance of the module, a small voltage will be induced during switching. The maximum voltage at the terminals VCE max, T must therefore be smaller than VCE max (see dotted line in Fig. 3-6). This value can be calculated using the formula (3-1) given below. The value for tf(IC) can be taken from figure 7 of the data sheets. I 0.8 VCEmax,T VCES LCE C t f IC (3-1) SOA-SEMiX.xls 1,2/ IC,pulse ICRM 1 Tc ≤ 25 °C Tj ≤ 150 °C tpulse ≤ 1 ms 0,8 0,6 0,4 0,2 0 0 0,2 0,4 0,6 0,8 1 VCE/VCES 1,2 1,4 Fig. 3-6 Reverse Bias Safe Operating Area (RBSOA) 16 © by SEMIKRON SKiM® - Technical Explanations Short Circuit Safe Operating Area The number of short circuits must not exceed 1000. The time between short circuits must be > 1 s. The duration time of the short circuit pulse tpsc is limited. Please refer to the maximum values for tpsc given in the data sheet. IC,sc 12/ IC,nom SOA-SEMiX.xls 10 Tj ≤ 150 °C VGE = ± 15 V di/dt ≤ 2500 A/µs 8 6 4 2 0 0 0,2 0,4 0,6 0,8 VCE/VCES 1,2 1,4 1 Fig. 3-7 Short Circuit Safe Operating Area (SCSOA) 3.3 Surge Current Characteristics of CAL Diodes When the CAL diode operates as a rectifier diode in an “IV-Q” application, it is necessary to know the ratio of the permissible overload on-state current IF(OV) to the surge on-state current IFSM as a function of the load period t and the ratio of VR / VRRM. VR denotes the reverse voltage applied between the sinusoidal half waves. VRRM is the peak reverse voltage. IFSM-CAL-Diode.xls 2 IF(OV) 1,8 IFSM 1,6 Applicable to sinusodial pulses (50 Hz) 1,4 0VRRM 0,5VRRM 1VRRM 1,2 1 IF IF(OV) 0,8 0,6 0,4 1 t 10 100 ms 1000 10 20 30 40 t [ms] Fig. 3-8 Surge overload current vs. time 3.4 Selection Guide The correct choice of the IGBT module depends very much on the application itself. A lot of different parameters and conditions have to be taken into account: Vin, Iin, Vout, Iout, fswitch, fout, overload, load cycles, cooling conditions, etc. Due to this variety of parameters a simplified selection guide is not seriously feasible. For this reason SEMIKRON offers the selection, calculation and simulation tool “SEMISEL” under http://semisel.semikron.com/. Almost all design parameters can be edited for various input or output conditions. Different cooling conditions can be chosen and specific design needs can be effectively determined. © by SEMIKRON 17 SKiM® - Technical Explanations 4 Thermal Resistances 4.1 Measuring Thermal Resistance Rth(j-s) The thermal resistance is defined as given in the following equation (4-1) Rth1 2 ΔT T1 T2 PV PV (4-1) The data sheet values for the thermal resistances are based on measured values. As can be seen in equation (4-1), the temperature difference ΔT has a major influence on the Rth value. As a result, the reference point and the measurement method have a major influence, too. Since SKiM modules have no base plate, the typical case temperature (T c) and hence the Rth(j-c) value cannot be given. Instead, SEMIKRON gives the thermal resistance between the junction and the heat sink Rth(j-s). This value depends largely on the thermal paste. Thus, the value is given as a “typical” value in the data sheets. SEMIKRON measures the Rth(j-s) of SKiM modules on the basis of the reference points given in Fig. 4-1. The reference points are as follows: Tj - The junction of the chip Ts – The heat sink temperature is measured in a drill hole, 2 mm beneath the module, directly under the chip. The 2 mm is derived from our experience, which has shown that at this distance from the DBC ceramic, parasitic effects resulting from heat sink parameters (size, thermal conductivity etc.) are at a minimum and the disturbance induced by the thermocouple itself is negligible. Reference point Tj (junction), silicon chip, hot spot DBC substrate No copper baseplate! Thermal grease 2 mm Heatsink Reference point Ts (heat sink) Fig. 4-1 Location of reference points for Rth measurement as used for SKiM For further information on the measurement of thermal resistances, please refer to: M. Freyberg, U. Scheuermann, “Measuring Thermal Resistance of Power Modules “; PCIM Europe, May, 2003 4.2 Transient Thermal Impedance When switching on a “cold” module, the thermal resistance R th appears smaller than the static value as given in the data sheets. This phenomenon occurs due to the internal thermal capacities of the package (cf. Fig. 2-22). These thermal capacities are “uncharged” and will be charged with the heating energy resulting from the losses during operation. In the course of this charging process the R th value seems to increase. During this time it is therefore called transient thermal impedance Z th. When all 18 © by SEMIKRON SKiM® - Technical Explanations thermal capacities are charged and the heating energy has to be emitted to the ambience, the transient thermal resistance Zth will have reached the static data sheet value Rth. The advantage of this behaviour is the short-term overload capability of the power module. 10 Zth(j-c)/Rth(j-s) 1 0,1 0,01 0,001 0,0001 0,00001 0,0001 0,001 0,01 0,1 tP [s] 1 Fig. 4-2 Transient Thermal Impedance The transient thermal behaviour is measured during SEMIKRON’s module approval process. On the basis of this measurement a mathematical model is derived, resulting in the following equation (4-2): t t t τ3 τ1 τ2 Zth t R1 1 e R2 1 e R3 1 e (4-2) For SKiM modules, the coefficients R1, τ1, and R2, τ2 can be determined using the data sheet values as given in Tab. 4-1. Parameter Unit IGBT, CAL diode R1 [K/W] 0.11 x Rth(j-s) R2 [K/W] 0.77 x Rth(j-s) R3 [K/W] 0.12 x Rth(j-s) τ1 [sec] 1.0 τ2 [sec] 0.13 τ3 [sec] 0.002 Tab. 4-1 Parameters for Zth(j-s) calculation using equation (4-2) 19 © by SEMIKRON SKiM® - Technical Explanations 5 Integrated Temperature Sensor Specifications All SKiM IGBT modules feature a temperature-dependent resistor for temperature measurement. The resistor is sintered onto the same DBC ceramic substrate near the IGBT and diode chips and reflects the actual case temperature. Every single half bridge has its own temperature sensor. For the exact locations of these sensors, please refer to Fig. 2-20 and Fig. 2-21. Since the cooling conditions have a significant influence on the temperature distribution inside SKiM modules, it is necessary to evaluate the dependency between the temperatures of interest (e.g. chip temperature) and the signal from the integrated temperature sensor. 5.1 Electrical Characteristic The temperature sensor has a nominal resistance of 5 kΩ at 25 °C. The measuring current should be 1 mA; the maximum value is 3 mA. The built-in temperature sensor in SKiM is a resistor with a negative temperature coefficient (NTC). Its characteristic is given in Fig. 5-1 A mathematical approximation (in the range from 80 °C to 150 °C) for the sensor resistance as a function of temperature R(T) is given by: R(T) = R100 x exp[B100/125 x (1/T - 1/T100)] With R100 = 339 Ω B100/125 = 4096 K T100 = 100 °C = 373.15 K R(T) = 339 Ω x exp[4096 x (1/T - 1/373.15 K)] 140 Resistance Value [kOhm] 120 100 80 60 40 20 0 -50 -25 0 25 50 75 100 125 150 Temperature [°C] Fig. 5-1 Typical characteristic of the NTC temperature sensor (included in every SKiM half bridge) 20 © by SEMIKRON SKiM® - Technical Explanations 1,00 0,90 Resistance Value [kOhm] 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00 80 90 100 110 120 130 140 150 Temperature [°C] Fig. 5-2 Characteristic of the NTC temperature sensor with tolerances Temperature [°C] -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Resistance Value minimum [kΩ] 147.237 78.766 43.908 25.394 15.180 9.335 5.910 3.813 2.504 1.682 1.153 0.807 0.576 0.418 0.308 0.232 0.176 0.136 0.106 0.084 standard [kΩ] 168.105 88.454 48.555 27.681 16.326 9.947 6.245 4.029 2.664 1.802 1.243 0.875 0.628 0.458 0.339 0.255 0.195 0.151 0.118 0.093 maximum [kΩ] 188.972 98.141 53.202 29.967 17.471 10.559 6.581 4.245 2.824 1.921 1.333 0.943 0.679 0.497 0.370 0.279 0.213 0.165 0.129 0.102 Tolerance maximum deviation [%] 12.4 11.0 9.6 8.3 7.0 6.2 5.4 5.4 6.0 6.6 7.2 7.8 8.3 8.7 9.1 9.2 9.4 9.6 9.8 10.0 Tab. 5-1 Resistance values and tolerance 21 © by SEMIKRON SKiM® - Technical Explanations 5.2 Electrical Isolation Inside SKiM modules the temperature sensors are mounted close to the IGBT and diode dice onto the same substrate. The minimum distance between the copper conductors is = 0.80 ± 0.2 mm. (Fig. 5-3) = 0.80 ± 0.2 mm Fig. 5-3 Detail: Temperature sensor inside SKiM According to EN 50178 (VDE 0160), this design does not provide "Safe Electrical Insulation", because the temperature sensor inside the SKiM module might be exposed to high voltages during semiconductor short-circuit failure mode. After electrical overstress the bond wires could melt off, producing an arc with high-energy plasma in the process (as shown in Fig. 5-4). In this case the direction of plasma expansion is unpredictable and the temperature sensor might come into contact with the plasma. The safety grade "Safe Electrical Insulation" in accordance with EN 50178 can be achieved by different additional means, which are described in this standard in more detail. Fig. 5-4 Sketch of high energy plasma caused by bond wire melting Please note: To ensure that electrical isolation Visol as stated in the data sheets is provided, suitable measurements are performed during the production process. These are described in section 2.6. 22 © by SEMIKRON SKiM® - Technical Explanations 6 Spring Contact System Specifications 6.1 Spring and Contact Specifications Rating / Specification Material Copper: DIN 2076-CuSn6 With silver surface: Abrasiveness 75 to 95 HV, tarnish protection < 0.1 µm Contact force 3 to 5 N Maximum contact resistance including ageing - 200 mΩ (current ≤ 1A) - 25 mΩ (current > 1A) Comment For one spring tested according to IEC 600068-2-43 (10 days, 10 ppm H2S, 75 % RH, 25°C) Tab. 6-1 Specifications for SKiM contact springs 6.2 PCB Specifications (Landing Pads for Springs) Rating / Specification Comment Chem. Sn (Chemical deposition) no min. thickness Intermetallic phases may be contacted HAL Sn (Hot Air Levelling) no min. thickness Intermetallic phases may be contacted NiAu Ni ≥ 3µm, Au ≥ 20nm (Electro less nickel, immersion gold) Tight Ni diffusion barrier required SnPb no min. thickness Intermetallic phases may be contacted Tab. 6-2 Specifications for the surface metallization of landing pads for SKiM contact springs 6.3 Storage Conditions Unassembled Rating / Specification Comment 28 month / 60 °C 95% RH After extreme humidity the reverse current limits may be exceeded but do not degrade the performance of the SKiM (max. storage time of module is 18 month and limited by pre-applied thermal paste) Assembled 28 month / 60 °C 95% RH Tab. 6-3 Storage conditions for SKiM modules with silver-plated contact springs 23 © by SEMIKRON SKiM® - Technical Explanations 6.4 Stray Inductance of Contact Springs The spiral springs look like the coils of an inductor. This would seem to contradict one of the main requirements in power electronics: “low inductance”. In measurements, however, these springs have not been shown to have any influence on switching behaviour. The following calculations verify the results obtained in practice. In this respect, the SKiM module, which features springs and PCB tracks between the driver and the springs, is comparable with a SEMITRANS module, which has internal wiring and wiring between driver and module. 6.4.1 Self-Inductance of the Spring Connection Fig. 6-1 Principle of springs and PCB conductors Inductance spiral spring LSp (with l = 5…10 D) µ π D2 L Sp μ n 2 l D 4 l2 D2 n L SP 77nH Fig. 6-2 SKiM with directly mounted driver = µ0 = 1,26 µH/m = 11.5 mm (length, spring under pressure) = 1.5 mm (inner diameter) = 20 (number of coils) Inductance PCB tracks LPCB l 2 μ a ln1 π db 31nH L PCB L PCB µ l a d b = µ0 = 1.26 µH/m = 100 mm (length spring pad to driver output stage) = 0.5 mm (distance between conductors on PCB) = 50 µm (thickness of copper layer) = 1 mm width of the copper track Total: LSp+PCB = 108 nH 6.4.2 Self-Inductance of a SEMITRANS Module Fig. 6-3 Open SEMITRANS 3 module. Yellow and red wires are gate and emitter wires, respectively 24 Fig. 6-4 SEMITRANS 3 module: wire connections to driver © by SEMIKRON SKiM® - Technical Explanations Inductance inside of the module LW1 l1 μ 2 a ln π d 50nH L W1 L W1 µ l1 a d = µ0 = 1.26 µH/m = 50 mm (wire length inside the module) = 3 mm (distance between wires) = 0.5 mm (wire diameter) µ l2 a d = µ0 = 1.26 µH/m = 100 mm (wire length outside the module) = 3 mm (distance between wires) = 0.5 mm (wire diameter) Inductance outside of the module LW2 l2 μ 2 a ln π d 100nH L W1 L W1 Total: LW1+W2 = 150 nH This inductance is in the same range as that of the solution with spring contacts and a PCB track. 6.4.3 Conclusion and Discussion Since the values for the parasitic inductances of SKiM and SEMITRANS modules are in the same range, a comparison would not prove particularly useful. Instead, the influence of the stray inductance on the gate voltage is generally looked at for comparison. Fig. 6-5 shows that self-inductance in wires has virtually no effect on the switching behaviour of the power semiconductor (neither in theory nor in the measurements performed). L 20 15 VGE [V] 10 V RG 5 L = 10 nH L = 150 nH L = 300 nH V_GE(th) 0 -5 Cies VGE -10 0 0,1 0,2 0,3 0,4 0,5 0,6 t [µs] Fig. 6-5 Influence of stray inductance on the gate voltage (model: voltage rise V GE at a capacitor CG for different circuit inductances L) (Cies ≈ QG / VG = 1 µC / 23 V = 43 nF, RG = 4 , dVGE = 23 V) A voltage across the gate wire inductance is induced only at the beginning when the gate voltage is applied. This voltage is far below the threshold voltage VGE(th). When the voltages rise to within the range of the threshold voltage where the switching event starts, the voltages are similar for all inductances. A small effect on the delay time during switching can be seen; in the example given in Fig. 6-5 this delay is around 20 ns for the highest assumed value of 300 nH. For higher gate resistor values this small difference disappears entirely. 25 © by SEMIKRON SKiM® - Technical Explanations 7 Reliability 7.1 Standard Tests for the Qualification of SKiM Modules The objectives of the test program (refer to Tab. 7-1) are: 1. Assure the general product quality and reliability. 2. Evaluate design limits by stressing under a variety of testing conditions. 3. Ensure the consistency and predictability of the production processes. 4. Appraise process and design changes regarding their effect on reliability. Reliability Test High Temperature Reverse Bias (HTRB) IEC 60747 High Temperature Gate Bias (HTGB) IEC 60747 High Humidity High Temperature Reverse Bias (THB) IEC 60068-2-67 High Temperature Storage (HTS) IEC 60068-2-2 Low Temperature Storage (LTS) IEC 60068-2-1 Thermal Cycling (TC) IEC 60068-2-14 Test Na Power Cycling (PC) IEC 60749-34 Vibration IEC 60068-2-6 Test Fc Mechanical Shock IEC 60068-2-27 Test Ea Standard Test Conditions for SKiM IGBT Modules 1000 h, VCE = 95 % VCEmax, Tc = 160 °C 1000 h, VGEmax, T = 175 °C 1000 h, 85 °C, 85 % RH, VCE = 80 % VCEmax, VCEmax, max. 80 V, VGE = 0 V 1000 h, + 135 °C 1000 h, - 40 °C 500 cycles, - 40 °C to + 125 °C 25.000 load cycles, ΔTj = 110 K Sinusoidal sweep, 10g, 2 h per axis (x, y, z) Half sine pulse, 100g, 3 times each direction (x, y, z) Tab. 7-1 SEMIKRON standard qualification tests 26 © by SEMIKRON SKiM® - Technical Explanations 7.2 Reliability of Spring Contacts The SKiM spring contact for the auxiliaries is a solder-free contact. It can therefore be compared with other solder-free contacts such as screw terminals or plug connectors. In Fig. 7-1 these “connections” are compiled for comparison. Screwed main terminals Plug connectors Spring contacts Pressure force typ. 50 N/mm² Pressure force typ. 10 N/mm² Pressure force typ. 20 - 100 N/mm² Fig. 7-1 Comparison of not soldered electrical connections The surface materials for the spring contacts as given in Tab. 6-1and Tab. 6-2 (silver-plated spring and, for example, tin surface for PCB landing pads) are based on “state-of-the-art” knowledge as gained from long-term experience with plug connectors and SEMIKRON’s long-term experience with spring connections. Compared to a plug connector, the spring contact has a far greater pressure and contact force, which accounts for the superior reliability of this connection. To verify this reliability, several harsh tests were performed on the spring contacts: temperature cycling, temperature shock tests, fretting corrosion (= micro vibration), electromigration, and a corrosive atmosphere test in accordance with IEC 60068-2-43: Atmosphere: 10 ppm H2S Temperature: Relative humidity: 75 % Volume flow: > volume x 3 per hour Duration: 10 days 25 °C No current load during storage All of these tests were passed successfully and demonstrated the outstanding reliability of SEMIKRON’s spring contacts. It goes without saying that SKiM modules passed all SEMIKRON standard reliability tests as given in Tab. 7-1 For further information on the reliability of spring contacts, please refer to: F. Lang, Dr. U. Scheuermann, “Reliability of spring pressure contacts under environmental stress”, Proc. Microelectronics Reliability Volume 47, Issues 9-11, September-November 2007, (18th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis) 27 © by SEMIKRON SKiM® - Technical Explanations 7.3 Reliability of SKiNTER Layer In power semiconductor modules different materials with different coefficients of thermal expansion are soldered together. Owing to this material bond, the layers cannot expand and release freely when temperature changes occurs, the result being thermally induced mechanical stress. The longer the joint, the more stress is induced and the more fatigue occurs. The illustrations in Fig. 7-2 and Fig. 7-3 show the package of different materials. Based on the materials shown in Tab. 7-2, temperature differences T-Tsink are given as resulting under similar operating conditions in these packages. With the coefficient of thermal expansion the elongation ratio L/L0 induced by the thermal expansion inside the package is calculated by equation L L0 L T TSink L0 L0 The materials cannot, of course, expand freely. Thus the difference of the figures for the theoretical expansion is an indicator for the resulting thermally induced stress in the bonding layer between these materials. L0 L0 Silicon Silicon Substrate Substrate Base plate Fig. 7-2 Material layers of a standard IGBT module Silicon Substrate Base plate T-Tsink in K 69.0 54.4 36.9 Fig. 7-3 Material layers of a SKiM module Standard IGBT module ΔL/L0 -6 in 10 1/K 4.1 0.28 8.3 0.45 17.5 0.50 T-Tsink in K 69.3 55.3 SKiM module -6 in 10 1/K 4.1 8.3 ΔL/L0 0.28 0.46 Tab. 7-2 Temperatures and thermal expansion for packages as shown in Fig. 7-2 and Fig. 7-3 The fatigue in the joint layers can be seen in the increase in thermal resistance. The increase in thermal resistance causes the chip temperature to increase too, because the output power remains unchanged. The increase in chip temperature in turn leads to an increase of T-Tsink, leading to even more stress in the layers and accelerating the fatigue. Solder layers, in particular, demonstrate aging as described above. This is due to the fact that the operation temperature of the module (125 °C to 150 °C) is very close to the melting temperature of the solder (220 °C to 250 °C), making the solder layer weak. With the SKiNTER layer the operation temperature is far below the melting point of silver (960 °C). In turn, the SKiNTER technology does not display this accelerated fatigue. Practical investigations have verified the theoretical considerations. Fig. 7-4 shows the results of power cycling tests with soldered and sintered IGBT modules. The solder layer fatigue and the accelerated aging process lead to an increase in thermal resistance and module failure after 40 000 cycles. The thermal resistance of the sintered layer does not increase. Modules in SKiNTER technology boast a >30% longer service life and improved reliability. 28 © by SEMIKRON SKiM® - Technical Explanations Thermal Resistance in Power Cycling Test T c,min=40°C, T j,max =128°C 0,400 Thermal Resistance R thjc [K/W] solder 0,350 0,300 0,250 0,200 0,150 0 10 20 30 40 50 60 70 Power Cycles [in thousands] soldered chip (1) soldered chip (2) diffusion sintered (1) diffusion sintered (2) Fig. 7-4 Change in thermal resistance during active power cycle tests For further information on the reliability of solder-free IGBT modules, please refer to: Dr. U. Scheuermann, P.Beckedahl, “The Road to the Next Generation Power Module - 100% Solder Free Design”, Proc. CIPS 2008, ETG-Fachbericht 111, 111-120, Nuremberg, 2008. 29 © by SEMIKRON SKiM® - Technical Explanations 8 Design Recommendations for SKiM The following recommendations are tips only and do not constitute a complete set of design rules. The responsibility for proper design remains with the user of the SKiM modules. 8.1 Printed Circuit Board Design 8.1.1 PCB Specification Recommendations for the printed circuit board: “FR 4” material can be used as a material for the printed circuit board. The thickness of copper layers should comply with IEC 326-3. The landing pads must not contain plated-through holes (“VIAs”) to prevent contact deterioration. In the remaining area VIAs can be used as desired. The landing pads for the auxiliary contacts must have a diameter of Ø = 3.5 mm ± 0.2 mm. As stated in section “PCB Specifications (Landing Pads for Springs)”, pure tin (Sn) is an approved interface for use with SKiM spring contacts. Sufficient plating thickness must be guaranteed in accordance with the PCB manufacturing process. The tin surface is normally applied to the PCB chemically or in a hot-air levelling process. A second approved surface for the landing pads is electro-less nickel with a final immersion gold layer (Ni + Au). Not recommended for use are boards with “organic solder ability preservative” (OSP) passivation, because OSP is not suitable for guaranteeing long-term corrosion-free contact. The OSP passivation disappears during soldering or after approximately 6 months of storage. During the solder processes the landing pads for SKiM spring contacts need to be covered and protected from contamination. This is particularly crucial for wave soldering. No residue of the cover material must be left on the landing pads as this could lead to deterioration of the electrical contact in the long term. 8.1.2 PCB Alignment Support SKiM offers a special alignment support for the printed circuit board and makes the assembly “poka yoke proof”. (For PCB mounting please refer to the mounting instructions) As shown in Fig. 8-1 SKiM has three guide pins. Thanks to these pins, the PCB can be easily placed on the module. There is no pin in the fourth corner. Only one method of assembly is possible if the PCB is shaped with three notches as shown in Fig. 8-2 and Fig. 8-3. The SKiM also has two alignment rings, which are used to put the PCB in position irrespective of the guiding pins. For detailed case drawings please refer to the data sheet. Fig. 8-1 SKiM with 3 x guiding pins and 2 x alignment rings, pressure part in pressed down position. 30 © by SEMIKRON SKiM® - Technical Explanations 8.1.3 PCB Outline, Location of Landing Pads The following drawings show the outline of a PCB for SKIM 63 (Fig. 8-2) and for SKiM 93 (Fig. 8-3). The drawings show: The outer dimensions of the PCB itself The location and dimensions of the drill holes The location and dimensions of the landing pads Please note: the layout of the landing pads for SKiM 63 and SKiM 93 is the same. Only the width of the PCB and the location of the drill holes for mounting is different. Fig. 8-2 Landing pads layout for SKiM 63 (bottom view) 31 © by SEMIKRON SKiM® - Technical Explanations Fig. 8-3 Landing pads layout for SKiM 93 (bottom view) 8.1.4 General Design Rules The following general design rules should be taken into account when developing an IGBT driver circuit: To suppress interference in the gate signals, magnetic coupling of any kind between the main current and the gate circuits has to be avoided. This can be achieved, for example, by using short gate and emitter connections, whose tracks should be led parallel and very close to each other, i.e. “no open loops”. Furthermore, the tracks should be in line with the main magnetic field = 90° to the main current flow IC. IGBT modules need to be turned off by a negative gate voltage V GEoff. Otherwise unwanted switchon via Miller capacitance Cres may occur. For short-circuit switch-off, a soft-switch-off circuit in the gate drive circuit (e.g. increased R Goff) is ® recommended to decrease the voltage overshoots in this particular case. SEMIKRON’s SKYPER PRO offers this feature. 8.1.5 Gate Clamping To ensure that the gate voltage VGE does not exceed the maximum value stated in the data sheet, the use of an appropriate gate clamping circuit (e.g. two anti-serial Z-diodes DGE, VZ = 16 V, as shown in Fig. 8-4) is recommended. This circuit has to be placed as close to the auxiliary contacts as possible. It is necessary to ensure that the IGBT is always in a defined state, especially in cases where the driver is not able to deliver a defined gate voltage VGE. A suitable solution to this problem is to use a resistor between gate and emitter RGE (≈ 20 kΩ). 32 © by SEMIKRON SKiM® - Technical Explanations This circuit is meant as an addition to the circuit shown in Fig. 8-8 RGE DGE Fig. 8-4 Gate clamping circuit 8.1.6 Connection of Unused Springs for GAL and GAR Types SKiM modules are always equipped with all auxiliary springs (as shown in Fig. 8-5) regardless of which circuit is inside. This means landing pads as given in Fig. 8-2 and Fig. 8-3 are necessary in any case. For GAL and GAR types the unused springs (marked red in Fig. 8-6 and Fig. 8-7) must be put on a defined voltage potential - normally 0 V. Otherwise displacement currents might lead to disturbance. Fig. 8-5 Pinout of “GD type” (sixpack) Fig. 8-6 Pinout of “GAL type” Fig. 8-7 Pinout of “GAR type” 8.2 Paralleling SKiM IGBT Modules When paralleling SKiM IGBT modules it is necessary to provide gate signal decoupling as well as homogeneous and low-inductance AC and DC connections. 8.2.1 Paralleling of Gate and Emitter Connections For optimum and smooth switching behaviour for all paralleled IGBTs it is necessary to ensure decoupling of the gate signals. For this reason every single gate needs its own gate resistor R G,x (≥ 2 Ω), as shown in Fig. 8-8. Paralleled IGBT modules and half bridges must be controlled by one driver. When using single drivers, there is no way of ensuring that all IGBTs switch simultaneously, meaning that the current distribution between these modules will not be even. 33 © by SEMIKRON SKiM® - Technical Explanations Furthermore, in Fig. 8-8 resistors RE,x (≥ 0.5 Ω) can be seen at every emitter contact. These resistors are also necessary to ensure homogeneous switching of the paralleled IGBTs. Additionally, these resistors dampen cross currents in the network resulting from main and auxiliary emitter paralleling. The additional Shottky diode (100 V, 1 A) parallel to RE,x ensures the safe turn-off of high currents (e.g. if a short-circuit occurs). To achieve similar parasitic inductances and homogeneous switching behaviour, the conductor lengths from the supply point to the individual gate and emitter connections should have the same length for all paralleled IGBTs. C RG,1 RG,2 RG,n RE,1 RE,2 RE,n DE,1 DE,2 DE,n IGBT Driver Gon Goff RGon,main RGoff,main E E Fig. 8-8 Circuit with RG,x and RE,x introduced for signal decoupling 8.2.2 Main Terminal Paralleling For optimum current distribution it is necessary for all parasitic stray inductances to be the same for every module. The same loop length for all connections is a good indicator for the same inductance. Fig. 8-9 shows an optimised AC connection: the length from all module terminals to the output is the same and all terminals are shorted very close to the module, keeping them on the same voltage potential. (Note: an additional mechanical support is recommended to prevent excessive mechanical forces at the terminals – refer also to the mounting instructions) The same rules apply to the DC connection. Here, the point of supply from the rectifier should also be central and not from one side. This ensures very similar stray inductances at the DC terminals, too. Support poles Fig. 8-9 Paralleled SKiM with low inductance DC link and symmetric AC link for optimised current distribution 34 © by SEMIKRON SKiM® - Technical Explanations 8.3 DC Link Bus Bars, Snubber Capacitors Due to stray inductances in the DC link, voltage overshoots as shown in Fig. 8-10 occur during IGBT switch-off (caused by the energy which is stored in the stray inductances). These voltage overshoots may destroy the IGBT module because they are added to the DC link voltage and may lead to VCE > VCES. First of all, the stray inductances have to be reduced to the lowest possible limit. This includes the low-inductance DC link design, as well as the use of low-inductance DC link capacitors. The use of snubber capacitors with a very low stray inductance, a low “ESR” Equivalent Series Resistance and a high “IR” Ripple Current Capability is recommended. IGBT-switch-off.xls VCE ∆V1 ΔV22 ∆V2 VCC ΔV1 Lstray snubber diC /dt Lstray DC bus iC2 Csnubber iC diC/dt = Operating current = During switch-off VCC = DC link voltage 0 0 t Fig. 8-10 Voltage overshoots as caused by parasitic inductances Furthermore, a pulse capacitor as snubber (see Fig. 8-11 and Fig. 8-12) should be placed between the +/- DC terminals of the SKiM. This snubber works as a low-pass filter and “takes over” the voltage overshoot. Typical values for these capacitors are from 0.1 µF to 1.0 µF. Proper measurements should be performed to ensure that the right snubber is selected. Fig. 8-11 Recommended snubber capacitor type. Fig. 8-12 Non-recommended snubber (too high a stray inductance). For further information on snubber capacitors, please refer to: J. Lamp, IGBT Peak Voltage Measurement and Snubber Capacitor Specification, Semikron Application Note, AN-7006, Nuremberg, 2008. 35 © by SEMIKRON SKiM® - Technical Explanations 9 Marking 9.1 “Passed” marking on housing Pre-assembled housings are 100% in-line tested. Black test dot A “passed” test result will be marked with a black dot. 9.2 Laser Marking for Modules All SKiM modules are laser marked. The marking contains the following items (see Fig. 9-1): 1 2 3 4 5 Fig. 9-1 Typical laser marking of SKiM module 1 2 3 4 5 SEMIKRON logo, with product line designation “SKiM®” Data Matrix Code (refer also to section “Data Matrix Code”) Type designation, for details refer to section ”Type Designation System” SEMIKRON order code Date code – 5 digits: YYMML (L = Lot of same type per week) The date code might be followed by “R” if the module is in accordance with the RoHS directive 36 “E” for engineering samples © by SEMIKRON SKiM® - Technical Explanations 9.3 Data Matrix Code The Data Matrix Code is described as follows: Type: ECC 200 Standard: ISO / IEC 16022 Cell size: Field size: 26 x 26 Dimension: 8 x 8 mm plus a guard zone of 1 mm (circulating) The following data is coded: 0.3 mm 1 2 SKiM909GD066HD 1 2 3 4 5 6 16 1 10 12 1 1 digits digit digits digits digit digit 3 4 23930790 0DE050091001 Type designation Blank Part number Production tracking number Blank Measurement number 5 7 8 9 10 11 1 1 4 1 5 6 7 1 5 digit digit digits digit digits 8 6 10 0006 11 10100 Line identifier (production) Blank Continuous number Blank Date code Total: 53 digits maximum 37 © by SEMIKRON SKiM® - Technical Explanations 10 Bill of Materials The SKiM modules “SKiM 63” and “SKiM 93” are both made from materials listed in Tab. 10-1. ESD Cover Pressure part Spring rubber plate Bus bar isolation foils Contact springs Bus bars Injection-moulded inserts (nuts) Injection-moulded bushes Housing Power hybrid Fig. 10-1 Sketch of SKiM 63 to illustrate the parts used Pressure part Spring rubber plate Bus bar isolation foils Bus bars Contact springs Injection-moulded inserts (nuts) Injection-moulded bushes Housing Polyamide 66 + 35% glass fibre, UL-V0 (does not contain free halogens) with injection-moulded steel plate (zinc plated) Cellular silicone Polyethylene terephthalate PET Copper, with silver surface and tarnish protection Copper alloy CuSn6 (DIN ISO 2076) with silver surface and tarnish protection Brass Steel zinc plated Polybutylene terephthalate PBT + 30 % glass fibre (does not contain free halogens) Power hybrids Substrate Wire bonds Copper, Aluminium Oxide (Al2O3), Copper. Nickel metallization and gold finish is applied to the copper surface. Aluminium alloy Chips and T-Sensor Silicon (Si) with aluminium metallization on the upper and silver metallization on the underside Chip sinter layer Silver (Ag) Coating Silicone Gel Tab. 10-1 SKiM – Bill of materials 38 © by SEMIKRON SKiM® - Technical Explanations Note: SEMIKRON products are not subject to the electrical and electronic equipment law (ElektroG)> ® Nevertheless, SEMIKRON still produces the product family SKiM in accordance with §5 of the ElektroG (prohibited substances) as well as article 4 of the directive 2002/95/EC of the European parliament (RoHS) on the restriction of the use of certain hazardous substances in electrical and electronic equipment. The ElektroG is the German legal equivalent of the European directive. 11 Packing Specifications 11.1 ESD COVER Against electrostatic discharge (ESD) while transport, the SKiM is protected by an ESD cover. The ESD Cover is shown in Fig. 12-1. ESD COVER Fig. 11-1 SKiM with ESD Cover 39 © by SEMIKRON SKiM® - Technical Explanations 11.2 Packing Boxes Standard packing boxes for SKiM modules: Fig. 11-2 Cardboard box with SKiM in transparent ESD tray, dimensions: 580 x 360 x 110 mm³ (l x w x h) Quantities per package SKiM 63 SKiM 93 Weight per package ≤ 14 kg Bill of materials Boxes: Trays: 16 pcs 8 pcs Paper (card board) ASK-PET/56 (not electrically chargeable) 11.3 Marking of Packing Boxes All SKiM packing boxes contain a sticker label. This label is placed on the packing box as shown in Fig. 11-2: Fig. 11-2: Location of label on SKiM packing boxes 40 © by SEMIKRON SKiM® - Technical Explanations The label contains the following items (see Fig. 11-3) 1 SKiM 306GD12T4 2 4 5 23630020 3 6 7 Fig. 11-3 Label of SKiM packing boxes 1 2 SEMIKRON Logo “Dat. Cd:” 3 4 5 6 7 “Menge:” SKiM Type Designation “Au.-Nr :” “Id.-Nr:” ESD sign Date code – 5 digits: YYMML (L=Lot of same type per week) Suffix “R” stands for “RoHS conform” Quantity of SKiM modules inside the box – also as bar code Order confirmation number / Item number on order confirmation SEMIKRON part number – also as bar code SKiM IGBT modules are sensitive to electrostatic discharges. Always ensure the environment is ESD proof before removing the ESD packaging and handling the modules. Bar code according to Standard: ECC 200 Format: 19/9 41 © by SEMIKRON SKiM® - Technical Explanations 12 Type Designation System 1 2 3 4 5 6 7 SKiM 40 6 GD 06 6 HD 1SKiM: Product name 2Nominal chip current IC,nom /10 3 Housing size 6 9 = = SKiM 63 SKiM 93 4 Circuit specifications (examples) GB GAL GAR GD = = = = IGBT half bridge IGBT low side chopper IGBT high side chopper 3 ~ IGBT inverter, “six pack” 5 Voltage class 06 12 17 = = = 600 V 1200 V 1700 V 6 IGBT chip technology 6 T4 E4 = = = Trench IGBT 3 (600 V and 1200 V) Trench IGBT 4 (1200 V) Low Loss Trench IGBT 4 (1200 V) Medium Power 7 Appendix (optional) HD = v1, v2,… = 42 CAL HD Diode Exclusive, customised special version © by SEMIKRON SKiM® - Technical Explanations 13 Figure Captions in the Datasheets Fig. 1 Collector current IC as a function of the collector- emitter voltage VCE (typical output characteristics) for Tj = 25 °C and Tj = 125 °C, Parameter: Gate-emitter voltage VGE; Values at terminal level, inclusive RCC´ + EE´ Fig. 2 Maximum rated continuous DC collector current IC as a function of the case temperature Tcase, terminal current Icmax = 600 A @ TTerminal = 100 °C Fig. 3 Typical turn-on and turn-off energy dissipation Eon and Eoff of an IGBT element and turn-off energy dissipation Err of a freewheeling diode as a function of the continuous collector current IC for inductive load Fig. 4 Typical turn-on and turn-off energy dissipation Eon and Eoff of an IGBT element and turn-off energy dissipation Err of a freewheeling diode as a function of the gate series resistance RG for inductive load Fig. 5 Typical transfer characteristic: continuous collector current IC as a function of the gateemitter voltage VGE; Values at terminal level, inclusive RCC´ + EE´ Fig. 6 Typical gate charge characteristic: gate-emitter voltage VGE as a function of the gate charge QG Fig. 7 Typical IGBT switching times tdon, tr , tdoff and tf as a function of the continuous collector current IC for inductive load and fixed gate series resistance RG for Tj = 125 °C Fig. 8 Typical IGBT switching times tdon, tr , tdoff and tf as a function of the gate series resistance RG for inductive load and fixed collector current IC for Tj = 125 °C Fig. 9 Transient thermal impedance Zth(j-c) of the IGBT element and the diode element as single pulse expired following an abrupt change in power dissipation Fig. 10 Typical forward characteristics of the inverse diode (typical and maximum values) for T j = 25 °C and Tj = 125 °C Fig. 11 Typical peak reverse recovery current IRRM of the inverse diode as a function of the fall rate diF/dt of the forward current with corresponding gate series resistance RG of the IGBT during turn-on Fig. 12 Typical recovery charge Qrr of the inverse diode as a function of the fall rate diF/dt of the forward current (Parameters: forward current IF and gate series resistance RG of the IGBT during turn-on) 14 Disclaimer SEMIKRON reserves the right to make changes herein without further notice to improve reliability, function or design. Information furnished in this document is believed to be accurate and reliable. However, no representation or warranty is given and no liability is assumed with respect to the accuracy or use of such information. SEMIKRON does not assume any liability arising out of the application or use of any product or circuit described herein. Furthermore, this technical information may not be considered as an assurance of component characteristics. No warranty or guarantee expressed or implied is made regarding delivery, performance or suitability. This document supersedes and replaces all information previously supplied and may be superseded by updates without further notice. SEMIKRON products are not authorized for use in life support appliances and systems without express written approval by SEMIKRON. 43 © by SEMIKRON