Appliance Design - January 2009 - (Page 42)

MotorS Fig. 1. CIPOS package outline. Fig. 2. Comparison of thermal resistance junction to case. double-layer PCB offers one extra degree of freedom for the layout; so that the circuit parasitic inductances can be minimized. The internal printed circuit board offers an inexpensive, but reliable solution for a high degree of integration and can be designed with common computer-aided layout-tools. The result is extremely short design cycles. It is very easy to design for a higher degree of integration, such as including microcontrollers or other components. All the power electronic chips are mounted on the DCB which is integrated in the module. Very high thermal conductivity (approximately 25 W/mK) of the DCB leads to a low thermal impedance between the chips and heatsink. The DCB has a thickness of only 325 µm and is plated with copper on the backside. The DCB dimensions are 30.2 mm x 50.4 mm. In production, the PCB and DCB are assembled individually and then wire bonded and transfer-molded to produce the final device, taking advantage of high-volume assembly methods for each part while still providing a high degree of flexibility in the individual design. It is possible to combine the same DCB with various PCB’s, and consideration could be given to combining the same PCB with various DCB’s, which might be done to achieve a scaling of current ratings. The improved thermal performance of the DCB, which carries the IGBT and Free-Wheeling Diodes, is compared to other common solutions such as the fully isolated TO-220 packages or Insulated Metal Substrate (IMS) modules in Fig. 2. The thin DCB of CIPOS lowers the thermal resistance by more than 35 percent compared to the standard IMS solutions. IMS modules and the TO-220 full-pack both have a backside coated with plastic molding compound that creates a large thermal barrier that reduces the heat transfer into the heat sink. The lower thermal resistance of CIPOS results in an increased current rating. Differences in the thermal resistance are especially noticeable in applications that require a short-term overload capabil- ity, such as clothes washers or air conditioners. Appliances with this overload requirement can increase the overload withstand time with CIPOS, because of the reduced thermal impedance between the silicon die and the heatsink, thereby reducing the self heating of the device. [1], [2]. The key requirements for small power drives, especially for applications with long lifetimes, are: 4Availability in high volume. 4Low maintenance. 4High reliability. Based on these requirements, Infineon offers four new designs of CIPOS, which are all in the same module outline as the original A-series and exactly match the requirements. These new designs include: 4B-series with open emitter for IC = 12A, 17A, and 22A. 4B2-series with open emitter for IC = 8A, 12A, and 17A. 4Closed-emitter-series with integrated shunt for IC = 12A. 4Design for switched reluctance motors. Fig. 3 shows the internal schematic of the B2-series. All series include the bootstrap circuit (diodes, current limiter, and capacitors), the NTC, and a blocking capacitor for the gate drive IC power supply. The A-series and the B-series are designed for applications that use external pull-up resistors in order to correctly interface the module with the microconwww.applianceDESIGN.com 42 applianceDESIGN AD01094Sole.indd 1 January 2009 12/11/08 3:27:58 PM http://www.soler-palauinc.com http://www.soler-palauinc.com http://www.appliancedesign.com

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Appliance Design - January 2009 Contents Editorial Shipments/Forecasts News Watch Supplier Spotlights Commercial Appliances Plastics & Parts Electronics Motors Design Marts Association Report: NAFEM Advertiser’s Index

Appliance Design - January 2009

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