Heat transfer interface

Details Heat transfer interface Heat transfer interface

2000-08-15

2001-11-27

Tolin, Gerald (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C165S185000, C174S016300

Reexamination Certificate

active

06324060

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a heat transfer interface and especially to a structure for reducing the contact resistance between the heat dissipating substrate and the heat source.
BACKGROUND OF THE INVENTION
Many different structures are used to the heat dissipation of electronic elements. The primary structure used currently is a heat dissipating structure formed by folding aluminum pieces namely, forming, radiating fines directly from folding aluminum. The surface thereof is according to the required electronic element such a CPU. As shown in
FIG. 1
, a radiating plate
10
with a size approximately equal to the top surface of an electronic heat emitting element is arranged. The bottom of the radiating plate
10
has a heat conductive panel
12
the opposite side of which is extended with a plurality of parallel fins
11
arranged as a matrix for guiding heat from the electronic heat emitting element
5
by the surface of the heat conductive panel
12
then the heat is guided out through the fins
11
. That is the fins having an area being several times of the surface area of the electronic heat emitting element serve to dissipate heat of the electronic heat emitting element. This is an economic and efficient heat dissipating way and is widely used. Since it is made of aluminum, it is light and no damage occurs on the surface of the electronic heat emitting element. However, with the improvement of the electronic heat emitting elements (for example, a CPU), the heat to be dissipated is increased, therefore, heat dissipation must be performed quickly. Namely, a lower thermal resistance is required for dissipating the heat from the chip of the electronic heat emitting element
5
for maintaining a normal operation of the electronic heat emitting element
5
. However, it is known that the prior art design can not serve for this requirement.
This is because in the prior art design, in order to reduce contact thermal resistance of a heat transfer interface in the prior art heat sink or CPU cooler, the two contact surfaces are machined to be as smooth as possible, and meanwhile, a soft filling material, such as a thermal grease
3
or a thermal pad
4
is filled into the gaps on the surface due to the machining. However, the aforesaid way still generates a high thermal resistance in a high heat flux, since no proper way and structure to resolve this problem, thus, it is still used widely. Moreover, since in general, copper or aluminum is used in the heat dissipating substrate, it can be acquired easily and is cheap, and has a rich amount in the nature. While, since it is hard to smooth the copper and aluminum (viewed from a microscope). Moreover, an oxide film is easily formed after machined so as to increase thermal resistance.
Besides, in the prior art, oxide metal powders or nonmetal powders are used as the soft filling material, which has a bad heat conductivity. In general, it is worse than the heat dissipating substrate. Only the soft filling material is used to fill the gaps between the contact surface for reducing heat resistance, a micro view thereof is shown in FIG.
2
. It is shown that in the prior art, a soft filling material, for example, thermal grease
3
or thermal pad
4
, is used to fill in the heat conductive plate
12
of the radiating plate
10
of the radiator
1
to be in contact with the smooth surface of the electronic element
5
. Further, as shown in
FIG. 3
, the connection of the radiator
10
and another radiator
10
is illustrated, wherein a layer of thermal grease
3
is clamped therebetween. Since thermal grease is beneficial in heat transfer, it is used generally. Because the roughness of the surface of the radiator
10
machined is large, i.e., the contact thermal resistance is large, thermal grease is necessary to reduced thermal resistance. However, the contact resistance remains large in this connecting way. Therefore, it is known the that defects of the prior art is a large thermal resistance.
SUMMARY OF THE INVENTION
Accordingly, the primary object of the present invention is to provide a heat transfer interface suitable in the connection of an electronic heat emitting element with a heat dissipating structure or a heat transfer interface between an electronic heat emitting element and a heat emitting element. A second heat transfer layer is added to a heat dissipating substrate of a heat dissipating structure. Therefore, the roughness of the surface of the heat dissipating substrate becomes smaller and the smoothness of the surface is increased.
In order to achieve the aforesaid object, the present invention provides a heat transfer interface. The surface of the heat dissipating panel of a radiator formed by a heat dissipating substrate is machined, and then a second heat transfer layer is added thereon. The heat transfer layer is connected to the heat dissipating substrate through plating physical vapor deposition, hot forging, or soldering. The second heat dissipating layer is a thin layer, in general, having a thickness of 0.001~0.030 mm, for enhancing the lightness of the contact surface of the heat dissipating substrate, reducing the hole gap on the surface of the heat dissipating substrate, reducing the amount of the soft filling material, reducing the filling thickness of the soft filling material, increasing the heat spreading and thus reducing contact resistance. Therefore, the filling amount of a soft filling material and the thickness thereof is increased. The bad contact due to partial unevenness is compensated. If a material of high anti-oxygen (such as diamond like coating) is used, then an oxide layer is hard to be generated after machining, and thus, the contact thermal resistance may be reduced.
In order to achieve the aforesaid object, the present invention provides a heat transfer interface. The surface of the heat dissipating panel of a radiator formed by a heat dissipating substrate is machined, and then a second heat transfer layer is added thereon. The heat transfer layer is connected to the heat dissipating substrate through plating, physical vapor deposition, hot forging, or soldering. The second heat dissipating layer is a thin layer for enhancing the lightness of the contact surface of the heat dissipating substrate, reducing the hole gap on the surface of the heat dissipating substrate, reducing the amount of the soft filling material, reducing the filling thickness of the soft filling material, increasing the heat spreading, and thus reducing contact resistance.


REFERENCES:
patent: 5440172 (1995-08-01), Sutrina
patent: 5729052 (1998-03-01), Tonti et al.
patent: 5926371 (1999-07-01), Dolbear
patent: 5930893 (1999-08-01), Eaton
patent: 5999407 (1999-12-01), Meschter et al.
patent: 6054198 (2000-04-01), Bunyan et al.
patent: 6084775 (2000-07-01), Bartley et al.
patent: 6165612 (2000-12-01), Misra
IBM Tech Discl Bull vol. 21 No. 10 Mar. 1979, “Thermal—Pad”, Hwang, pp. 4028.

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