Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

A HEAT TRANSFER ENHANCEMENT METHOD FOR FORCED CONVECTION BONDED-FIN HEATSINKS

IP.com Disclosure Number: IPCOM000008503D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-18
Document File: 3 page(s) / 114K

Publishing Venue

Motorola

Related People

John M. Waldvogel: AUTHOR

Abstract

Various types of heatsinks can be used in elec- tronic packaging to keep circuit elements cool by effectively transporting dissipated heat to a cooling fluid; e.g., the ambient air. A bonded-fin heatsink is comprised of a die-cast, extruded or machined backplane which includes long, parallel grooves into which plate fins are inserted and bonded using an adhesive. The convective heat loss from the exposed surfaces of a heatsink to the cooling fluid is quantified according to q" = h-AT (1) where q" is the heat flux from the surfaces, h is the convective heat transfer coefficient and AT is the temperature difference between the surfaces and the fluid. It is apparent in Equation 1 that for a given heat flux (thermal load), AT will be reduced if h is increased. By reducing the temperature difference between the heatsink and the cooling fluid, the electronic components will operate at a lower temperature, resulting in a more reliable product overall. The basic problem to be addressed with this invention is the maximization of the con- vective heat loss from heat sink surfaces by modifi- cation of tin geometry to provide greater convective heat transfer coefficient values.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 3

MOTOROLA Technical Developments

A HEAT TRANSFER ENHANCEMENT METHOD FOR FORCED CONVECTION BONDED-FIN HEATSINKS

by John M. Waldvogel

BACKGROUND

  Various types of heatsinks can be used in elec- tronic packaging to keep circuit elements cool by effectively transporting dissipated heat to a cooling fluid; e.g., the ambient air. A bonded-fin heatsink is comprised of a die-cast, extruded or machined backplane which includes long, parallel grooves into which plate fins are inserted and bonded using an adhesive. The convective heat loss from the exposed surfaces of a heatsink to the cooling fluid is quantified according to

q" = h-AT (1)

  where q" is the heat flux from the surfaces, h is the convective heat transfer coefficient and AT is the temperature difference between the surfaces and the fluid. It is apparent in Equation 1 that for a given heat flux (thermal load), AT will be reduced if h is increased. By reducing the temperature difference between the heatsink and the cooling fluid, the electronic components will operate at a lower temperature, resulting in a more reliable product overall. The basic problem to be addressed with this invention is the maximization of the con- vective heat loss from heat sink surfaces by modifi- cation of tin geometry to provide greater convective heat transfer coefficient values.

SOLUTION

  For a bonded-fin heatsink with a cooling fluid passing over the fin surfaces, the fluid flow is char- acterized as a duct flow of rectangular cross-section. Each finned channel represents a rectangular duct. The variation of the convective heat transfer coeffl- cient with flow distance (measured from where the cooling fluid enters the fin core of the heatsink) for a duct flow can be presented in dimensionless form in terms of Nusselt number, Nu, and dimensionless duct length, x*, where

Nu = hD/k (2)

x* = x/(D*Re*Pr) (3)

Re = ~DI(v*A) (4)

  In these equations, k, Pr and v are the fluid ther- mal conductivi...