Browse Prior Art Database

COMPACT HEATSINK

IP.com Disclosure Number: IPCOM000006175D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-11
Document File: 5 page(s) / 163K

Publishing Venue

Motorola

Related People

Ravi Bhatla: AUTHOR

Abstract

The miniaturization trend has put greater pressure on the reduction of heatsink size in electronic pack- ages. A generic design of a Compacr Heatsink and its thermal superiority over the conventional heatsink has been experimentally confirmed. 2' Factorial experiments were done to further ascertain the thermal reliability of one Compact Healsink design for low power Land Mobile products.

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MOTOROLA INC. Technical Developments Volume 13 July 1991

COMPACT HEATSINK

by Ravi Bhatla

ABSTRACT

  The miniaturization trend has put greater pressure on the reduction of heatsink size in electronic pack- ages. A generic design of a Compacr Heatsink and its thermal superiority over the conventional heatsink has been experimentally confirmed. 2' Factorial experiments were done to further ascertain the thermal reliability of one Compact Healsink design for low power Land Mobile products.

INTRODUCTION

   The Compact Heatsink is based on the principle of having the shortest unobstructed thermal path for the heat flux. The Compacr Heotsink depicted in Figure 1 is more efficient than the conventional heatsink because the Compacr Heatsink geometry adheres more closely to the direction of the heat flux flow than that of the conventional heatsink. This information was experimentally verified in Figure 2. In case 1, the

power device (heat source) was attached to surface A of the heatsink and a temperature rise of the lid of the power device as a function of time was recorded. In cast 2, the same power device was attached to surface B (edge) of the same heatsink. Temperature rise in the latter case was lower, depicting a more efficient heatsinking capability.

ACTUAL DESIGN

  Figure 3 depicts how one can utilize the afore- mentioned property of the matter in an actual design of a Land Mobile product. This design greatly reduces the size of the heatsink normally used for this application. ,The question remains: Is this reduced size heatsink thermally reliable? Thermal reliability of this design was verified by 2' factorial experiments, both for 1-4 modified EIA duty cycle as well as for the 5 minute continuous duty cycle. The experimental results are noted in Figure 4 and Figure 5. This data confirms the thermal adequacy of this heatsink design.

HEAT SOURCE

COMPACT HEAT SINK

\

n - INEFFICIENT USE OF MASS

ONVENTlONAL

HEATSINK q - GOOD USE OF MASS

"HEAT FLUX

CONE

FIG. I

0 Motorola. Inc. ,991 31

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MOTOROLA INC. Technical Developments Volume 13 July 1991

THERMAL PATH IMPROUEMENT ILLUSTRRTION

CASE - 1 HEAT SOURCE ON PLANE "A"

CASE - 2 HEAT SOURCE ON PLANE "B"

HEAT

Ei - HEAT SOURCE MOUNTlNG PLANE "A"

n - HEAT SOURCE MOUNTlNG PLANE "B"

-50 0 50 100 150200250300350

TIME - SECONDS

FIG. 2

32 0 Motorola. 1°C. 19%

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MOTOROLA INC. Technical Developments Volume 13 July 1991

PACKAGING SCHEME

POR 1OW PACKAGE MATERIAL-COPPER

DIAMETER - 1.875" THICKNESS - .375"

HOLE FOR THE HERTSINK

THERMRL UIA'S~

Fig. 3

0 Motorola. 1°C. ,991 33

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