Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-11-10
2001-10-02
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S702000, C361S714000, C257S706000, C257S708000, C165S080300
Reexamination Certificate
active
06297959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation structure for radiating heat generated by an electronic part.
2. Description of the Related Art
Conventionally, many electronic parts including an IC (integrated circuit) are mounted on a printed circuit board for an electronic device. Some of these electronic parts generate heat upon operation. Thus, it is required to effectively radiate heat generated from these electronic parts which generate heat (hereinafter called heating elements).
To this end, in the prior art, as shown in
FIG. 3
, a through hole
7
is formed at a portion of a printed circuit board
3
on which a heating element
1
is mounted. A radiator
4
is provided with a projection portion
5
having an outer diameter slightly smaller than the diameter of the through hole
7
and having substantially same thickness as that of the printed circuit board
3
. Heat radiated from the heating element
1
is radiated through the radiator
4
. To be more concrete, the projection portion
5
of the radiator
4
is inserted into the through hole
7
provided at the printed circuit board
3
. In this case, silicon grease
2
serving as gelled cementing material is coated on the surface of the heating element
1
facing to the printed circuit board
3
or the upper surface of the projection portion
5
of the radiator so as to homogenize the contacting state of the contacting and opposing surfaces of the heating element
1
and the projection portion
5
. The radiator
4
is attached to the printed circuit board
3
through a silicon grease layer
20
which is formed by coating the silicon grease
2
thereby to join the tip end of the projection portion
5
of the radiator
4
to the heating element
1
.
According to such a configuration, heat generated from the heating element
1
is radiated in a manner that the heat is transferred to the projection portion
5
of the radiator
4
through the silicon grease layer
20
and further diffused to the entire portion of the radiator.
However, according to the configuration of
FIG. 3
, at the time of inserting the projection portion
5
of the radiator
4
into the through hole
7
of the printed circuit board
3
, it is required to finely adjust an amount of the silicon grease
2
coated on the surface of the heating element
1
facing to the printed circuit board
3
and the upper surface of the projection portion
5
of the radiator
4
. Thus, there arises a problem that the attaching procedure is complicated. To be more concrete, if an amount of the silicon grease to be coated is too small, predetermined radiation effect can not be obtained. In contrast, if the amount of the silicon grease to be coated is too much, excessive silicon grease
2
leaks or escapes out of the radiator through the space formed between the printed circuit board
3
and the radiator
4
, whereby the leaked grease adheres to a hand of a worker or the parts on the printed circuit board
3
or the like thereby to degrade the workability. Accordingly, it is required to adjust an amount of the silicon grease by taking both the radiation effect and the workability of the attaching procedure into consideration.
SUMMARY OF THE INVENTION
The present invention is attained so as to obviate the aforesaid conventional problem, and an object of the present invention is to provide a radiation structure for a heating element which can prevent the leakage of silicon grease and improve the workability of attaching procedure without degrading radiation effect.
In order to attain the aforesaid object, according to a first aspect of the invention, there is provided a radiation structure for a heating element in which in a radiation structure for a heating element including a base and a projection portion provided at the base, wherein a heating element is placed on a through hole provided at a printed circuit board, and the projection portion is inserted into the through hole from a surface side of the printed circuit board opposing to a surface on which the heating element is placed and contacts with said heating element through gelled cementing material, whereby heat generated by the heating element is radiated outward through the projection portion, characterized in that
the base includes a first surface contacting to the printed circuit board on a surface facing to the printed circuit board and at least one step surface provided at a position away from the printed circuit board than the first surface.
According to a second aspect of the invention, there is provided a radiation structure for a heating element according to the first aspect the invention in which the step surface is formed by the first surface contacting to the printed circuit board and a second step surface provided on a side of the first surface opposing to the projection portion.
According to a third aspect of the invention, there is provided a radiation structure for a heating element according to the first or second aspect of the invention, in which the step surface is formed by the first surface contacting to the printed circuit board and a third step surface provided on a projection portion side of the first surface.
According to the aforesaid configuration of the present invention, the heating element is placed on the through hole provided at the printed circuit board and soldered to the surface of the printed circuit board. The radiator is formed by the projection portion fitly inserted into the through hole provided at the printed circuit board and the base for integrally holding the projection portion. The base is provided with a step surface on its surface facing to the printed circuit board. Silicon grease is coated on the surface of the heating element facing to the printed circuit board or the upper surface of the projection portion of the radiator, and then the projection portion is fitted into the through hole provided at the printed circuit board, whereby the base is brought into contact with the printed circuit board at its first surface provided at the portion most close to the printed circuit board. As a consequence, the silicon grease layer is formed between the heating element and the projection portion of the radiator and the printed circuit board and the projection portion of the radiator.
Heat generated from the heating element is transferred to the projection portion of the radiator through the silicon grease layer and further transferred to the entirety of the radiator. Excessive silicon grease leaks or escapes out of the radiator through the space formed between the peripheral surface of the through hole formed at the printed circuit board and the outer peripheral surface of the projection portion of the radiator. However, since the excessive silicon grease is stayed or collected at the space formed by the printed circuit board and the step surface provided at the radiator, the excessive silicon grease is prevented from leaking on the printed circuit board.
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Japanese Abstract No. 07335793 dated Dec. 22, 1995.
Ueno Hitoshi
Yoshida Shigeru
Datskovsky Michael
Picard Leo P.
Pioneer Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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