Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-09-11
2003-04-22
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C174S016300, C257S722000, C165S080300, C165S185000, C361S710000
Reexamination Certificate
active
06552906
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a radiator for electronic parts, an electronic device, an electric circuit device, and a computer, more particularly to a radiator for electronic parts, an electronic device, an electric circuit device, and a computer in which generation of air bubbles is prevented in a heat conductive semifluid material.
FIG.
7
(A), FIG.
7
(B) and FIG.
7
(C) collectively show how an air bubble
75
is generated in thermal grease
74
in a bending process of a wired board
72
employed in a conventional electronic device. A CPU chip
71
is mounted at a predetermined position on the wired board
72
and a heat sink
73
is mounted above the CPU chip
71
. The heat sink
73
is larger in area than the CPU chip
71
. The bottom of the heat sink
73
comes in contact with the top surface of the CPU chip
71
. Even when the CPU chip
71
and the heat sink
73
are put in contact with each other directly, the actual contact area between the CPU chip
71
and the heat sink
73
is small. This is because the both items have the fine unevenness on their contact surfaces, and the CPU chip
71
is not so strong in structure, so that the heat sink
73
cannot be fixed onto the CPU chip
71
SO strongly by bolts (not illustrated) that fix the heat sink
73
to the wired board
72
. The heat resistance thus becomes high in the heat conduction path from the CPU chip
71
to the heat sink
73
. In addition, the heat density on the contact portion between the CPU chip
71
and the heat sink
73
becomes the highest in the heat conduction path between the CPU chip
71
and the heat sink
73
for the reasons of the thermal design. In order to solve this problem, therefore, the thermal grease
74
is provided between the top surface of the CPU chip
71
and the bottom surface of the heat sink
73
,
50
that the air is purged from between both surfaces. The air, when it is left there, causes the heat resistance to be increased.
Recently, however, it has come to be known that a problem referred to as “pump out” occurs in such electronic devices. Concretely, because both ends of the heat sink
73
are fixed to predetermined portions of the wired board
72
via bolts and there appears a difference in the thermal expansibility between the wired board
72
and the heat sink
73
, the bending degree of the wired board
72
is increased/decreased due to changes of the temperature of the subject electronic device, thereby the size of the space between the CPU chip
71
and the heat sink
73
is increased/decreased. FIGS.
7
(A), (B), and (C) show how the state of the thermal grease
74
is changed according to the space size (standard, smaller than standard, and larger than standard) between the CPU chip
71
and the heat sink
73
in the center of the thermal grease
74
. In FIG.
7
(A), the thermal grease
74
is just fit in the top area of the CPU chip
71
. In FIG.
7
(B), the thermal grease
74
overflows the top area, because the space becomes thinner. In FIG.
7
(C), a part of the thermal grease
74
that has overflowed in FIG.
7
(B) does not return to the top area of the CPU chip
71
or delays to return, thereby an air bubble
75
is generated in the thermal grease
74
. And, because the air bubble
75
causes a large heat resistance, generation of such an air bubble
75
in the thermal grease
74
must be prevented.
Published Unexamined Patent Application No.9-102567 discloses a technique for avoiding such air bubbles to be left between the surface of a base and solder when in soldering a heat sink to the base. According to the technique, a groove is formed on the surface of the base so as to purge the residual air smoothly and the groove surface is formed as a metallic one so as to embed the solder therein properly. However, the gazette does not describe any technique for suppressing generation of air bubbles in such a heat conductive semifluid material as thermal grease and the groove disclosed in the gazette cannot suppress generation of air bubbles in such the heat conductive semifluid material.
Under such circumstances, it is an object of the present invention to provide a radiator for electronic parts enabled to prevent air bubbles from being generated in a heat conductive semifluid material, which is caused by such the “pump out” problem, as well as an electronic device including such the radiator for electronic parts, an electric circuit device including such the electronic device, and a computer including such the electronic circuit device.
SUMMARY OF THE INVENTION
A first aspect of the present invention is a radiator for electronic parts, which includes a heat receiving surface for receiving a heat from a heating element, a heat radiating element for radiating a heat transferred from the heat receiving surface, and one or a plurality of through-holes opened to the heat receiving surface at one end and opened to a region other than the heat receiving surface at the other end respectively so that a heat conductive semifluid material being inserted from the one end is driven up and down therein.
The through-hole in the first aspect of the present invention is not limited only to those extended straight. For example, in case the radiator for electronic parts has a column member and the through-hole is formed at the column member, the through-hole may be extended in the direction of the center line of the column member from one end and bent towards the periphery of the column member at a middle point so that the other end is opened to the periphery of the column member. The number of through-holes and the diameter of each through-hole are set to a value that can assure the tip of the heat conductive semifluid material to be stayed in the through-hole regardless of the increase/decrease of the size of the space between the electronic part and the radiator for electronic parts in the electronic device including the radiator for electronic parts. In a typical example, the radiator for electronic parts is made of metal, for example, aluminum, and the thermal conductivity of the radiator is about 200 times that of the heat conductive semifluid material. A region corresponding to a through-hole in the layer of the heat conductive semifluid material increases the heat resistance of the heat transfer path from the heating element to the radiator. Consequently, the less the number of through-holes is and the smaller the diameter of the through-hole is, more effectively the through-hole can suppress the increase of the heat resistance. The radiator for electronic parts is, for example, a heat sink. The heat conductive semifluid material is, for example, thermal grease.
In case there is no through-hole, the heat conductive semifluid material is expanded/shrunk towards/from the periphery according to changes of the layer thickness. The present invention forms one or a plurality of through-holes, so that the amount of the heat conductive semifluid material to be inserted into the through-holes is changed according to changes of the layer thickness, thereby the material is suppressed from expansion/shrinkage towards/from the periphery. Consequently, invasion of air bubbles into the heat conductive semifluid material can be prevented even when the material is expanded/shrunk in the radiation direction.
The conventional radiator for electronic parts might generate air bubbles in the layer of the heat conductive semifluid material when it is manufactured. However, such the generation of air bubbles in the manufacturing process can be prevented by selecting a proper amount of the heat conductive semifluid material to be filled between the heat receiving surface of the radiator for electronic parts and the heating element. At this time, the amount is decided with reference to the timing at which the heat conductive semifluid material goes up in the through-holes of the radiator.
A second aspect of the present invention is a radiator for electronic parts obtained by adding the following to the radiator of the first aspect of the present invention: a plate memb
LandOfFree
Radiator for electronic parts, electronic device, electric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiator for electronic parts, electronic device, electric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiator for electronic parts, electronic device, electric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3003967