SAE TECHNICAL PAPER SERIES 400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org2002-01-1889 Direct-Soldered Mounting Inverter Modules for Traction Motor Drives Jih-Sheng (Jason) Lai Virginia Polytechnic Institute and State Univ. Junhyung Kim Elgar Electronics Corp. Charles E. (Bud) Konrad VPT, Inc. 2002 Future Car Congress Arlington, Virginia June 3-5, 2002Reprinted From: Pr oceedings of t he 2002 Future Car Congress on CD-ROM (FCC2002CD)Downloaded from SAE International by Univ of California Berkeley, Tuesday, July 31, 2018Quantity reprint rates can be obtained from the Customer Sales and Satisfaction Department. To request permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the aut hor(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by whic h discussions will be printed with the paper if it is p ublished in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be c onsidered for presentation or publication thr ough SAE should send the manuscript or a 3 00 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USAAll SAE papers, standards, and selected books are abstracted and indexed in theGlobal Mobility DatabaseDownloaded from SAE International by Univ of California Berkeley, Tuesday, July 31, 20182002-01-1889 Direct-Soldered Mounting Inverter Modules for Traction Motor Drives†* Jih-Sheng (Jason) Lai Virginia Polytechnic Institute and State Univ. Junhyung Kim Elgar Electronics Corp. Charles E. (Bud) Konrad VPT, Inc. † The project was funded under Department of Energy CARAT program. * This work made use of ERC Shared Facilities supported by the National Science Foundation under Award Number EEC-9731677.ABSTRACT Mounting power module by directly soldering them onto the heatsink can significantly reduce the thermal impedance between power module and heatsink as compared to the conventional bolted method that requires thermal grease or other interface materials in between. However, the problem of this mounting technique is the voids existing in the thermal interface. In this paper, void reduction techniques are studied through solder paste selection, heating procedure, and temperature profile. In order to study the effect of void rate, a 15-MHz Scanning Acoustic Microscope (SAM) is used as an inspection tool. To measure the thermal interface impedance, a constant current source injection into power diode along with curve tracer measurement was adopted. Experimental results indicate that the reduction of void rate also significantly reduces the thermal interface. INTRODUCTION The power modules that are popularly used in today’s power devices such as power diodes and Insulated Gate Bipolar Transistor (IGBT) are becoming the industry standard for high-power electronics applications because of its ease of mounting and integration. To mount power modules onto heatsinks, solder or thermally conductive epoxy can be used to eliminate the air gaps from the thermal interface between the module and the heat spreader by conforming to surface irregularities. Recently, the direct-soldered technique was introduced to the integrated inverter-motor propulsion drives for hybrid electric vehicle applications [1]. The problem found in direct-soldered method is the existence of voids in between the interface layers, which introduce anomalous thermal spreading. The voids can increase thermal impedance, heat losses, cracks, and delaminating at the joint between the module and heat sink. It is difficult to reduce the void rate because of large surface area involved. Typically ther