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Posted on 01 June 2019

Transfer Mold IPMs

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50A and 75A/600V devices with heat dissipating insulation sheet

This article presents a large-scale Dual In-line Package Intelligent Power Module (DIP-IPM Ver.4 series) with ratings of 50A and 75A/600V developed by Mitsubishi Electric for home appliances and package air conditioner. 75A/600V large-scale DIP-IPM Ver.4 has been achieved by development of 5th generation full gate CSTBTTM, shrink process ICs and novel heat dissipating insulation sheet, etc.

By Ming Shang, Kazuhiro Kuriaki, Toru Iwagami, Hisashi Kawafuji, Toshiya Nakano Power Device Works, Mitsubishi Electric Corporation, Japan Robert Wiatr, Mitsubishi Electric Europe, Germany

 

In recent years, inverters of the motor driver system aiming at energy saving and high performance are progressing broadly from the large current domain usage of hundreds ampere classes to the low current domain usage of several ampere classes. Mitsubishi Electric Corporation manufactured the intelligent power semiconductor module DIPIPM of transfer mold structure ahead of the industry from 1997, and DIP-IPM is adopted as the inverter drive of white home appliances or industrial motors.

"Large-scale DIP-IPM Ver.3 series (20~50A)" which achieved the miniaturization and the thermal resistance decrease of the module after 2003 is commercialized, and it has corresponded to large current needs of inverter board, such as a package air-conditioner and industrial motor etc. As a new product for the package air conditioner market, "large-scale DIP-IPM Ver.4 series" to expand the amperage rating up to 75A by the size equal with conventional Ver.3 was developed. Large-scale DIP-IPM Ver.4 series contributes to the miniaturization and the cost reduction of the inverter board.

Outline view of PS21A7A (75-600V)

Technology adopted in 75A DIP-IPM Ver. 4

Power chip

PS21A7A adopted the latest CSTBT chip with full gate, in order to improve the trade-off relationship of on-state voltage and turn-off loss. This new CSTBT makes power loss reduction about 10% compared with a conventional CSTBT (plugged cell merged CSTBT).

In an IGBT, the resistance of the n- drift layer has to be kept high in order to withstand the blocking voltage at off-state. As the hole injection from collector to n- drift layer at on-state, the resistance of the n- drift layer is reduced, and power loss is reduced. However, the resistance of the n- drift layer near emitter side is difficult to reduce because the hole density here becomes low due to the far away distance to the collector. Hence, it is difficult to achieve a very low onstate voltage. CSTBT reaches a much lower on-state voltage by the virtue of optimization of the hole density in the whole n- drift layer. A special n barrier called as carrier stored layer is designed under the P base layer to hinder the holes injected from the collector from penetrating to the emitter. This makes the further reduction of the onstate voltage possible because hole density is increased in the n- drift layer even near the emitter side. Since CSTBT is developed to be with high current carrying capability, sometimes it is designed in a structure called plugged cell merged CSTBT so as to ensure a certain withstanding capability against short circuit failure. This structure is illustrated in Figure 3. With this structure the cell pitch is adjusted by ''plugging'' some portion of the cells in a conventional high cell density device. The polysilicon in the ''plugging'' cell is connected to the emitter electrode. This connection provides additional drain to source capacitance that helps to stabilize the drain potential under short-circuit conditions. The result is stable oscillation free short-circuit operation even under high speed switching condition.

Structure of full gate CSTBTTM

Structure of plugged cell merged CSTBT

However, in the case of 75A/600V DIP-IPM Ver. 4, the built-in CSTBT chip showed Figure 2 has been designed with full gate specification by optimizing the inside drive IC to ensure the short circuit withstand capability. Therefore, much reduction of power loss has been able to be realized. Figure 4 shows the improvement of the trade-off between on-state voltage and turn-off loss. [3] This full gate CSTBT technology brings 75A of rated current with similar package to 50A large-scale DIP-IPM.

Trade-off characteristic

The HVIC shrink process technology

The HVIC (High Voltage IC) integrated in PS21A7A provides optimized drive for the full gate specification CSTBT and realizes high function by the virtue of the advanced shrink process technology. The shrink has been achieved by developing a circular shape MOSFET which replaces the traditional oval shape MOSFET used for high voltage level shift in the HVIC. Also, the traditional offset structured transistor has been finely processed in the lateral direction by combining shallow junction technology which increased the output capability without enlarging the chip size. Figure 5 shows the output capability versus chip size. Although the full gate specification CSTBT needs larger drive capability than a plugging cell structured CSTBT, the above fine process technology realizes an IC with high drive capability without sacrificing chip size.

Output capability versus chip size

Electrical circuit configuration and components

The internal circuitry of PS21A7A is composed of IGBTs and FWDs (Free Wheel Diode) in a three-phase inverter structure together with control ICs, which is same as the previous version DIP-IPM. In addition, the open-emitter type products that have three divided emitter terminals of low-side IGBTs to sense the inverter phase current by using external shunt resistors are getting ready. Figure 6 shows internal block diagram of PS21A7A.

Internal block diagram of PS21A7A

Control ICs are designed with minimum necessary functions such as IGBT drive, built-in control power supply, under-voltage (UV) lockout circuit and short circuit (SC) protection. It is possible to drive the DIPIPM directly without using of an optocoupler, by applying HVIC where high voltage signal level shift circuits are integrated for high-side. Optimized design, such as logic filtering function, has been carried out to obtain enhanced noise immunity against noise transmitted from signal lines. In addition, the soft switching effect has been obtained by optimizing the drive capability, which helps to suppress the switching noise.

Package (Reduction of thermal resistance)

Expand amperage rating up to 75A and the package size is same to the conventional 50A product (large-scale Ver. 3 series), the calorific value would increase and the improvement of the heat dissipation characteristic was a task. By having adopted the insulation sheet which changed to the insulated method by conventional resin, and was excellent in thermal conductivity, the thermal resistance between module case and the power device was reduced about 30% from conventional product, and the rise in heat was suppressed. This structure applies the technology adopted by the Super Mini DIP-IPM package already mass-produced.

Structure of large-scale DIPIPM Ver.3 series

Structure of large-scale DIPIPM Ver.4 series

Comparison of thermal resistance

VOT (Analog output voltage of temperature)

The module temperature protection needed to attach to the external heat dissipation fin the thermistor which detects temperature conventionally, and needed to prepare the extra peripheral circuit. The function which outputs internal temperature information from the LVIC (Low Voltage IC) in the module was built-in newly.

Since an external thermistor is made unnecessary and the number of peripheral circuit parts can also be reduced by this, it contributes to cost reduction of inverter board.

In addition, even though contact of the module and fin which were not able to be detected by the conventional system, there is also a merit which can detect abnormalities.

Moreover, since DIP-IPM itself does not operate protecting function to the over temperature of the module, control of inverter output current by the system side is possible.

VOT output

Short Current protection by Current Sense method

Short circuit protection of the power device needed the shunt resistance whose rated power is tens of Watts conventionally, because of the system which sends the collector current of the power device through external shunt resistance, detects a short circuit by sensing the voltage of both terminals of shunt resistance. This time, by means of applying multi-emmiter IGBTs, the current of 1/thousands of collector current was taken out from the power device, that current passed to shunt resistance, and in this way, the method which detect and protect the short-circuit was adopted. It contributes to the miniaturization and cost reduction of the inverter board because resistance with small rated apparent power can be used for the shunt resistance.

Inverter loss simulation

Figure 11 shows inverter loss simulation result imitated three phases modulation sinusoidal waveform.

Inverter loss simulation result (IGBT 1chip)

PS21A7A makes a contribution to miniaturization of external heat radiation fin and conservation of energy by having achieved low power loss by full gate CSTBT and its optimized drive IC. Moreover, PS21A7A decreases the mounting area to the air conditioner control board, etc. by having achieved power loss shown in Figure 8 by large package size shown in Figure 12.

Package outline of PS21A7A, Package size 2449mm2 (31mm•79mm)

Electrical characteristics

Main electrical characteristics (inverter part and control part) of PS21A7A (75A/600V) are indicated in Table 1.

Main Electrical Characteristics of PS21A7A (Tj=25°C, unless otherwise noted)

View in the future

In order to realize the amperage rating more than 75A, it is necessary to develop further heat dissipation. From now on, by further improvement of thermal resistance and power device loss and commercialization of the larger amperage rating capacity is the next target.

Moreover, product development of rated voltage 1200V amperage rating 5A~35A is developed in the same package as largescale DIP-IPM Ver. 4 series. Main electrical characteristics (inverter part and control part) of PS22A78-E (35A/1200V) are indicated in Table 2.

Main Electrical Characteristics of PS22A78-E (Tj=25°C, unless otherwise noted)

As for 1200V products, there is an active converter usage etc. other than inverter usage, there are needs of more than 35A for further large capacity, and the loss improvement of the power chip in addition to the improvement of heat dissipation is necessary.

We're now developing next generation devices, the further low loss IGBT and FWD, and using them, commercialization of larger amperage rating capacity is the next target.

Conclusions

A new 75A/600V DIP-IPM Ver. 4 PS21A7A in a large-scale package has been developed by applying full gate CSTBT and its optimized drive IC, together with the high heat dissipating insulation sheet.

This development is sure to make much contribution to the extension of the applications and miniaturization of inverter systems as well. It is also a fruit of Mitsubishi low loss product development conception. Its application is expected to cover both home appliance use and general motor drives. We will continuously make efforts to develop much excellent devices to realize power loss reduction and save natural resources.

 

References:

1) G. Majumdar, et al.," A New Generation High Performance intelligent Power Module", 1992 PCIM Europe.
2) H. Iwamoto, E. Motto, J. Achhammer, M. Iwasaki, M. Seo, T. Iwagami, "New Intelligent Power Module for Appliance Motor Control", 2000 PCIM Europe.
3) Y. Tomomats u, K. Satoh, S.Kusunoki, J. Yamada, Y.Yu, J.Donlon, H. Iwamoto, E. Motto ''Characteristics of a 1200V CSTBTTM Optimized for Industrial Applications'' 2001 IAS.
4) S. Shirakawa, T. Iwagami, H. Kawafuji, M. Seo, K. Satoh ''A New Version Transfer Mold-Type IPMs with Compact Package'' 2005 PCIM China.
5) Toru Iwagami, Kats umi Satoh, Kou s homei, Hisas hi Kawafuji, Shinya Shirakawa, Tomofumi T anaka ''A Development of 30A/600V Super mini DIP-IPM'' 2006 ipemc.

Paper presented at PCIM China 2008.

 

 

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