Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-04-23
2001-05-15
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S263000, C165S185000
Reexamination Certificate
active
06232558
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electronic component mounting base board, and more particularly to a structure of an electronic component mounting base board for preventing the occurrence of warping in the base board during the sealing with a resin after the mounting of the electronic component.
2. Description of Related Art
As the electronic component mounting base board, there was a base board formed by adhering and fixing a heat sink to a surface of an insulating substrate in the past. In this case, the positioning of the insulating substrate and the heat sink was carried out by using a positioning guide.
The inventors have already proposed an electronic component mounting base board of a structure capable of facilitating the positioning between the substrate and the heat sink (Japanese Patent Application No. 9-67408). That is, as shown in the comparative example of
FIGS. 15 and 16
, a projection portion
913
extending from a side face of a heat slug
91
is inserted into a positioning hole
96
formed in an insulating substrate
95
and joined and fixed to the substrate through a solder
94
. Thus, the positioning between the heat slug
91
and the insulating substrate
95
is carried out by inserting the projection portion
913
into the positioning hole
96
.
An insulating resin adhesive layer
92
is interposed between the heat slug
91
and the insulating substrate
95
.
And also, a conductor circuit
93
is formed on the insulating substrate
95
, while the surface of the insulating substrate
95
is covered with a solder resist
97
.
In substantially a central portion of the insulating substrate
95
is formed a concave mount portion
951
for mounting an electronic component. As shown in
FIG. 16
, an electronic component
952
is adhered onto the mount portion
951
through an adhesive
953
and thereafter a sealing resin
954
is filled in the mount portion
951
.
In the sealing of the mount portion
951
with the sealing resin
954
, however, the sealing resin is filled into the mount portion
951
at a molten state and then cured. As a result, the sealing resin
954
shrinks as shown in
FIG. 16
, but the heat slug
91
does not shrink. For this end, a side of the insulating substrate
95
opposite to the heat slug
91
is shrunk by the shrinkage of the sealing resin
954
to cause warping of the insulating substrate
95
. In case of causing such a warping, the connection reliability of the electronic component mounting base board to a surface mount device lowers.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the above problems of the conventional technique and to provide an electronic component mounting base board capable of preventing the occurrence of warping in the insulating substrate when the mount portion for the electronic component is sealed with the resin.
According to the invention, there is the provision of an electronic component mounting base board comprising an insulating substrate provided with a conductor circuit and a mount portion for an electronic component, and a heat slug adhered to the insulating substrate, wherein said heat slug is comprised of a flat main body arranged face to the insulating substrate and a projection portion extending vertically from a side face of the main body, and the main body is adhered to the insulating substrate through a resin adhesive layer, and the projection portion is inserted into a positioning hole and joined to the insulating substrate through a solder, and the heat slug is provided with a deforming portion absorbing deformation of the insulating substrate between a resin-adhered region of the main body and a solder-joined region of the projection portion.
DESCRIPTION OF PREFERRED EMBODIMENTS
According to the invention, it has been noticed that the warping of the insulating substrate in the resin-sealing of the mount portion of the electronic component is caused by the heat slug being harder than the insulating substrate. In the invention, therefore, the deforming portion is formed in the heat slug from a material harder than the insulating substrate to absorb the deformation of the insulating substrate.
In the electronic component mounting base board according to the invention, the deforming portion capable of absorbing the deformation of the insulating substrate is formed between the resin-adhered region of the main body and the solder-joined region of the projection portion in the heat slug. This deforming portion deforms with the deformation of the insulating substrate. As a result, when the mount portion for the electronic component is sealed with the resin, the insulating substrate deforms and also the deforming portion of the heat slug deforms accompanied with the deformation of the insulating substrate, whereby the occurrence of warping in the insulating substrate can be prevented.
And also, the resin adhesive layer made from a soft material is interposed between the main body of the heat slug and the insulating substrate. Therefore, the resin adhesive layer can absorb the deformation of the insulating substrate, so that the warping of the insulating substrate can more effectively be controlled.
On the other hand, the projection portion of the heat slug is inserted into the positioning hole and joined thereto through the solder. That is, the solder filled in the positioning hole strongly joins the projection portion therein to ensure the connection of the heat slug to the insulating substrate.
As previously mentioned, the deforming portion is formed between the resin-adhered region of the main body and the solder-joined region of the projection portion in the heat slug and deforms accompanied with the deformation of the insulating substrate, so that the influence of the deformation of the insulating substrate upon the solder-joined region can be prevented. As a result, the strong solder-joining strength can be maintained between the projection portion and the positioning hole of the insulating substrate.
According to the invention, therefore, the occurrence of the warping in the insulating substrate can be prevented when the mount portion for the electronic component is sealed with the resin.
The word “between the resin-adhered region of the main body and the solderjoined region of the projection portion” used herein means a zone between a part of the main body adhered with the resin adhesive layer and a part of the projection portion joined with the solder.
In a preferable embodiment of the invention, the deforming portion is formed in a periphery of a part of the main body extending the projection portion in the heat slug. In another preferable embodiment of the invention, the deforming portion is formed in a part of the projection portion adjacent to the main body. Thus, the warping of the insulating substrate can effectively be prevented.
In the other preferable embodiment of the invention, the deforming portion is a slit, which can effectively prevent the warping of the insulating substrate.
In a still further embodiment of the invention, an end portion of the slit is opened and the other end portion is closed by a connection portion connecting the resin-adhered region to the solderjoined region. In this case, the slit is more deformable and easily follows the deformation of the insulating substrate. Therefore, the warping of the insulating substrate can be more controlled.
In another preferable embodiment of the invention, both end portions of the slit are closed by a joint portion connecting the resin-adhered region to the solder-joined region. Thus, the connection strength between the main body and the projection portion in the heat slug can be enhanced. In this case, the end portion of the slit closed by the joint portion is favorable to be a curved form. Thus, the occurrence of cracks in the end portion of the slit can be prevented when the slit deforms accompanied with the deformation of the insulating substrate.
In the other preferable embodiment of the invention, the deforming portion is a thin port
Asano Koji
Ishida Naoto
Minoura Hisashi
Nakao Morio
Tsukada Kiyotaka
Cuneo Kamand
Gaffin Jeffrey
Ibiden Co. Ltd.
Oliff & Berridg,e PLC
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