A new 3A/600V transfer mold IPM with RC(Reverse Conducting) -IGBT

Transcription

1 A new 3A/600V transfer mold IPM with RC(Reverse Conducting) -IGBT

2 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 2 CONTENT A new 3A/600V transfer mold IPM with RC(Reverse Conducting) -IGBT Introduction RC-IGBT chip technology (1) RC-IGBT chip design (2) RC-IGBT chip characteristics DIP-IPM design (1) Electrical circuit configuration and components (2) Package design (3) Thermal simulation Characteristics of new 3A DIP-IPM (1) Electrical Characteristics (2) Inverter loss simulation and motor drive operation Conclusions References

3 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 3 A new 3A/600V transfer mold IPM with RC(Reverse Conducting) -IGBT K. Satoh*, T. Iwagami*, H. Kawafuji*, S. Shirakawa*, M. Honsberg**, E. Thal** * Power Device Works, Mitsubishi Electric Corporation, Japan **, Germany Abstract: A super mini Dual In-line Package Intelligent Power Module (DIP-IPM Ver.4) with ratings of 3A/600V has been developed by using a new power chip technology. As this new technology which integrates FWD (Free Wheeling Diode) chip to IGBT chip in inverse parallel reduces a half of the power chip number in power module, this IPM makes reliability higher and handling power capability larger at same package size. This paper presents this new technology, the design and the characteristics of the 3A DIP-IPM Ver Introduction Inverters are increasingly used in motor control systems of white gods such as washing machine, refrigerator and air-conditioner, in order to improve efficiency and controllability of systems. Recently, as IPM composed of power chips and control ICs has self-protection function and comes into use in inverter systems of white goods to make reliability higher and to make system configuration simpler. The conventional IPM with rated current of 3A was designed in a SIP (Single In-line Package) structure in order to reduce the area of control printed board (PCB). However, that IPM has the following demerits. a) Short creapage distance and short clearance b) Short length between terminals c) High thermal impedance A new 3A/600V IPM has been developed in order to overcome these demerits. Furthermore, this IPM makes higher reliability and higher performance. In this IPM, the following methods are adapted. 1) DIP-IPM structure to solve a) and b) 2) New heat dissipation structure with insulating resin sheet and much thinner power chips to solve c) 3) Fine patterning HVIC (High Voltage IC) process with 1.3 µm design rule to reduce HVIC chip area 4) CSTBT TM (Empowered Trench IGBT) by thin wafer process to reduce power loss 5) Newly developed integration of FWD to CSTBT TM by optimized collector-short structure to decrease power chip number A comparison of this new DIP-IPM with the conventional SIP-IPM is shown in table 1. As this IPM only consists of a half semiconductor chips of conventional one, this brings reliability higher. In this IPM, inserted CSTBT TM chip has reverse conducting performance by integration of FWD in inverse parallel to IGBT as shown in Fig.1. This CSTBT TM is named RC-IGBT. This paper introduces RC-IGBT chip technology, the design and the characteristics of a new 3A DIP- IPM Ver RC-IGBT chip technology A conventional IGBT with an optimized trade-off relationship between on-state voltage drop [V CE (sat)] and turn-off energy loss [Eoff] required a two-epitaxial layer to make punch though collector side, so the wafer processing of the collector side was very difficult. Therefore, one-chip IGBT with built-in FWD was impossible. Recently, RC-IGBT has been developed by using thin wafer process technology which was possible to handle wafers with less than 100µm thickness and to make patterning at collector side surface. RC-IGBT technology brings one-chip IGBT with built-in FWD in inverse parallel. This new chip is called a reverse conducting IGBT (RC-IGBT). Table 1 Comparison of SIP-IPM and new DIP-IPM 3

4 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 4 (1) RC-IGBT chip design The RC-IGBT has a collector-shorted (CS) device structure, where an N and P Zebra-striped pattern is formed on backside of wafer, instead of the conventional uniform plane two-layered N-buffer and P-collector structure. The combination of optimized impurity concentration of P-collector layer and N-CS layer, optimized lifetime control technique and this new Zebra-striped pattern make a good agreement for four direction trade-off relationship among IGBT s V CE (sat), IGBT s turn-off capability, FWD s forward voltage drop(v F ) and FWD s reverse recovery loss(erec). Fig.1 Shows the RC-IGBT device structure. A CSTBT TM structure is the basic structure and the Fig.3 Pphotograph of 3A RC-IGBT chip 2) RC-IGBT chip characteristics Fig.4 shows that RC-IGBT operates as both IGBT in the first quadrant and FWD in the third quadrant, because RC-IGBT can conduct backward current in the reverse direction by applying a negative bias to the collector side. V CE (sat) of this RC-IGBT is 1.6V at 3A and 125degC in the first quadrant operation and reverse voltage drop of RC-IGBT(forward voltage drop(v F ) of integrated FWD) is 1.5V at 3A and 125degC in the third quadrant operation. Fig.1 3 dimensional view of the RC-IGBT emitter side structure is similar to that of commercial CSTBT TM chips. The chip thickness is less than 100µm. Both the backside P-region and N-region widths were optimized. Fig.2 shows P-region and N- region formed at backside. Fig.4 RC-IGBTs forward and reverse output I-V characteristics Fig.2 Cross sectional SCM photograph of wafer backside structure Fig.3 shows the chip photograph of 3A RC-IGBT chip with the size of 2.5mm x 3.0mm. As the size of IGBT chip and FWD in conventional 3A SIP-IPM are 2.0mm x 2.1mm and 1.65mm x 1.85mm respectively, RC-IGBT chip area is 2/3 of the total area of IGBT and FWD. Fig.5 shows the turn-off waveforms in switching an inductive load at 125degC. As this RC-IGBT chip can turn-off 12A under the condition of 600V, RC- IGBT has very wide RB-SOA. Furthermore, RC- IGBT turns-off with smaller tail current. The reverse recovery characteristics of FWD builtin RC-IGBT is evaluated as shown in Fig.6. Heliumirradiation process as lifetime control technique reduces the reverse recovery current to about 2/3 of rated current at Vcc=300V, I F =3A, di F /dt=100a/µs and Tj=125degC. In addition, this new chip has wide SCSOA with more than 7µs at Vcc=400V, Tj=125degC and inductive load. 4

5 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 5 Fig.5 inductive load turn-off waveform The internal circuitry of the new 3A IPM (as shown in Fig.8) is composed of RC-IGBTs in a three-phase inverter structure together with control ICs. Control ICs are designed with minimum necessary functions such as IGBT drive, built-in control power supply under-voltage (UV) lockout and short circuit (SC) protection, over temperature protection. It is possible to drive the IPM directly without using optocoupler isolation, by applying HVIC where high voltage signal level shift circuits are integrated for high side drive. The optimized design, such as offer filtering function, has been carried out to obtain enhanced noise immunity against noise transmitted from signal lines. Fig.9 shows turn-off waveform of the new 3A IPM under the condition of Vcc=300V, V D =V DB =15V, Tj=125degC and Ic=3A. Fig.6 Reverse recovery waveform 3. DIP-IPM design (1) Electrical circuit configuration and components The RC-IGBT technology brings some merits. One is making assembling process simpler with a half power-chip-dice-bonding and without Al wire-bonding from IGBT to FWD. The other is making current capability larger because of smaller RC-IGBT area at same current capability than that of conventional one. Fig.7 shows the outline of 3A new IPM. Fig.7 Outline view of 3A/600V DIP-IPM Fig.8 Internal block diagram of new 3A DIP-IPM 5

6 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 6 Fig.10 shows turn-off waveform of the new 3A IPM under the condition of Vcc=300V, V D =V DB =15V, Tj=125degC, Ic=3A. make about double area for power dice pad, compared with conventional one, this IPM are possible to make current capability larger. Furthermore, both a half number of wire bonding points and a half power chip number make the reliability much higher. Fig.11 shows the cross-sectional drawing of this 3A DIP-IPM. Fig.11 Cross-sectional drawing of 3A DIP-IPM Fig.9 Turn on waveform of 3A DIP-IPM Fig.10 Turn off waveform of 3A DIP-IPM-IPM (2) Package design This new 3A IPM changes package from SIP structure to DIP structure. DIP structure does not give complicated and long inner lead (wiring by Cu frame in package), and this IPM has only one HVIC with higher integration as against three conventional HVICs in SIP-IPM. Furthermore, the direct wire bonding technique, by which power chips and ICs have been directly connected by Au wires, is used in this IPM in order to delete the dummy-pin (lead frame as the intermediary frame from IC via Au wiring form intermediary frame and to intermediary frame via Al wiring to power chip). As for the package design, highly integrated HVIC and direct wire bonding technique in this IPM (3) Thermal simulation As the RC-IGBT chip has both IGBT operation loss (switching loss and conducting loss) and FWD operation loss (recovery loss and conducting loss) at actual inverter operation, it is important to design the thermal dissipation. So, a thermal simulation is carried out by CAE. As the result estimating power loss in this 3A RC-IGBT, 3.22W of loss was given to all six RC-IGBT chips. Under the condition of Vcc=300V, V D =15V, Tj=125degC, fc=15khz and power factor=0.8, IGBT operation loss is 2.87W and FWD operation loss is 0.35W at Io(peak)=3A. The similar loss were given to 6 IGBT chips and 6 FWD chips in conventional one, respectively. Fig.12 shows simulating model of 3A DIP-IPM with six RC-IGBT chips. Fig.13 shows the thermal simulating result of the new 3A IPM. The RC-IGBT chip, which is closest to neighbour RC-IGBT chip and sets between RC- IGBT chips, has highest Tj (junction temperature). However, even the highest Tj is only 111degC, which is much lower than that of conventional one(125degc). This reason is that RC-IGBT s loss density (per chip area) is 0.43W/mm 2 and the conventional IGBT loss density is 0.68W/mm 2. 6

7 Mitsubishi_1_8 Seiten_neu.qxd :41 Uhr Seite 7 Fig.12 Thermal simulating model of 3A DIP-IPM Fig.14 Output current waveform Fig.13 Thermal simulating result 5. Conclusions A new 3A DIP-IPM with higher reliability has been developed by applying RC-IGBT chip technology that will bring handling current larger (about 10A in this DIP-IPM) and assembling cost lower. This IPM with its features such as compact-ness, cost-effective performance and so on are expected to make inverterization of low power motor control systems expand in home appliance applications. 4. Characteristics of new 3A DIP-IPM (1) Electrical Characteristics The typical electrical characteristics of the 3A DIP- IPM with RC-IGBT are indicated in Table 2. Fig.15 Inverter loss simulation result Table 2 Electrical characteristics of 3A DIP-IPM (2)Inverter loss simulation and motor drive operation Fig.14 shows the output current waveform at motor drive operation. Fig.15 shows inverter loss simulation result imitated three phase modulation sinusoidal waveform under the condition of Vcc=300V, V D =15V, Tj=125degC, fc=15khz and power factor=0.8. RC- IGBT power loss at Io(peak)=3A is3.22w. This value is equivalent to conventional total loss of IGBT loss and FWD loss. References [1] H. Iwamoto, E. Motto, J. Achhammer, M. Iwasaki, M. Seo, T. Iwagami, "New Intelligent Power Module for Appliance Motor Control", 2000 PCIM Europe, [2] M. Iwasaki, T. Iwagami, M. Fukunaga, X. Kong, H. kawafuji, G. Majumdar, "A New Version Intelligent Power Module for High Performance Motor Control", 2004 PCIM China, [3] T. Sasaki, H. Takao, T. Shikano, S. Fujita, D. Nakajima, T. Shinohara, "Development of High Current Transfer-mold type Power Module with High Heatcycle Durability", 2004 ISPSD Kitakyushu, [4] H. Takahashi, A. Yamamoto, S. Aono, T. Minato, 1200V Reverse Conducting IGBT, 2004 ISPSD Kitakyushu, 7

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