Analysis of Direct-Soldered Power Module / Heat Sink Thermal Interface for Electric Vehicle Applications

Reducing the thermal impedance between power module and heat sink is important for high-power density, low-cost inverter applications. Mounting a power module by directly soldering it onto a heat sink can significantly reduce the thermal impedance at the module / heat sink interface, as compared to the conventional method of bolting the two together with a thermal grease or some other interface materials in between. However, a soldered interface typically contains a large number of voids, which results in local hot spots. This thesis describes approaches taken to reduce voids in the solder layer through surface treatment, solder paste selection, and adjustment in solder-reflow conditions. A 15MHz scanning acoustic microscope (SAM), a non-destructive inspection tool, was used to determine the void content at the module / heat sink interface. The experimental results show that a significant reduction in thermal resistance can be achieved by reducing the void content at the soldered module / heat sink interface. Moreover, a comparison of the thermal resistances in cases using the worst soldering, which contains the largest voided area, ThermstrateTM and thermal grease are presented. Thermal performances of the modules are studied by simulation with Flotherm.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2001

Author dc:creator

• Kim, Junhyung

Chair dc:contributor.committeechair

• Lai, Jih-Sheng

Committee members dc:contributor.committeemember

• Chen, Dan Y.
• Boroyevich, Dushan

• inverter and electric vehicle
• soldering
• thermal resistance
• void reduction

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-05012001-165030

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/32071