High thermal conductivity polymeric packages for semiconductor devices (05-Oct-2009)

ABBABB

Date: October 5, 2009 Page: 1/4

High thermal conductivity polymeric packages for

semiconductor devices

Inventor: Matteo Fabbri

Abstract

This invention aims at using high thermal conductivity polymers to make packages for semiconductor devices. The packages that can be easily obtained by injection molding or casting can have extended surfaces to reduce the convective resistance. In this way the need for an external heat sinking body is eliminated. This also eliminates the need for any sort of interface material and it simplifies the assembly of the electronic circuit.

Background

Semiconductor devices are usually soldered on a substrate which is in turn encased in plastic. Alternatively the silicon die is sandwiched in between two conductive parts. In both cases the heat generated in the silicon die flows through the contacting parts to the outside of the package into a heat sink or other means apt to transfer the heat into the surrounding environment.

Low power devices are packaged in standard formats, like TO220 (See Fig. 1), TO247, etc.

Figure 1. Typical TO 220 packages: front and back sides.

Those packages are then attached with the help of some clamping means to a heat dissipating surface or element (see Fig. 2) as the amount of heat that can otherwise be dissipated through the rest of the package is limited as the plastic used in the package has very low thermal conductivity and the heat transfer surface is not large enough.

Figure 2. Examples of heat sinks for TO 220.

© Copyright 2009 ABB Research Ltd, Affolternstrasse 44, CH-8050 Zurich, Switzerland. All rights reserved.

ABBABB

Date: October 5, 2009 Page: 2/4

Invention

The invention is centered on using high thermal conductivity polymers to fabricate the encasing package of semiconductor devices. Partially or fully enclosed semiconductor packages made out of polymers can easily be molded around silicon devices. The degree of electrical insulation varies depending on the type of polymers used. The heat dissipation from the package depends on the conductive resistance within the package and on the convective resistance outside the package.

The use of polymers with thermal conductivity larger than 10 W/mK reduce the internal thermal resistance through the plastic package to a level low enough to be useful in helping cooling the device. As the conductive resistance is reduced by the use o...