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Browse Prior Art Database

NOVEL HEAT SINKING TECHNIQUES

IP.com Disclosure Number: IPCOM000009075D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-06
Document File: 4 page(s) / 197K

Publishing Venue

Motorola

Related People

Philip Burrus: AUTHOR [+2]

Abstract

As technology continues to advance, modern semiconductor devices continue to get smaller in size. For small signal devices, this is highly advanta- geous, as electronic devices are able to compress more features into smaller packages. In power elec- tronics however, the reduction in size is a double- edged sword. While the reduction in size enables designers to develop smaller products, these new products are still required to supply the same amounts of power as their larger predecessors. Further, the losses associated with power electronics tend to generate heat, and with the smaller compo- nents produce higher heat densities.

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MOTOROLA Technical Developments

NOVEL HEAT SINKING TECHNIQUES

by Philip Burrus and Holley Renfro

  As technology continues to advance, modern semiconductor devices continue to get smaller in size. For small signal devices, this is highly advanta- geous, as electronic devices are able to compress more features into smaller packages. In power elec- tronics however, the reduction in size is a double- edged sword. While the reduction in size enables designers to develop smaller products, these new products are still required to supply the same amounts of power as their larger predecessors. Further, the losses associated with power electronics tend to generate heat, and with the smaller compo- nents produce higher heat densities.

  In switching power supplies in particular, it is well known that the three fundamentaI components, switch, inductor, and diode tend to dissipate energy and therefore get hot. While all three parts get hot, the switch and diode tend to get the hottest. Advanced semiconductor technology has greatly reduced the size of diodes and switches and, as a result, the heat density of semiconductors has great- ly increased. These increasing power densities have generated a need for innovative methods of heat sinking.

  In addition to the reductions in the size of com- ponents, the manufacturing process associated with electronic products is also changing. In the past, electronic manufacturers manufactured printed cir- cuit boards (PCB) with leaded parts (radial, axial, etc.). These leaded parts were soldered to printed wiring boards (PWB) via plated holes that went through the board. This "through hole" technology is rapidly giving way to "surface mount technolo- gy", whereby parts are soldered to pads on the PWB. Surface mount technology offers several advantages, including higher manufacturing quality, more compact designs, and faster production cycles.

Surface mount designs, however, can be a nuisance to power electronics designers who attempt to remove heat from small surface mount components. While numerous "off-the shelf' heat sinks am avail- able for thermal management of through hole com- ponents, there are very few heat sinks commercially available for surface mount components.

  The need has, therefore, arisen for new and innovative heat sinking methods to remove heat from surface mount semiconductors. This article describes two heat sinking methods which have been used to effectively cool surface mount semi- conductors in TO-263 and D-Pak packages. The methodologies are by no means limited to these package types, however. The designs are generic and may be easily modified to accommodate numer- ous package styles.

   The first heat sinking technique describes a method that is applicable! when the heat source and heat sink are electrically connected. The second method describes a heat sinking method that is applicable when the heat source and heat sink are electrically isolated.

TO-263

  These heat sinking methods arose fro...