Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Bump leads
Reexamination Certificate
2002-02-19
2003-12-23
Nguyen, Cuong (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Bump leads
C257S684000, C257S777000
Reexamination Certificate
active
06667550
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an installation technique for optical parts and electric parts. More particularly, this invention relates to an installation structure and an installation method for optical modules that are used in the optical communication field.
BACKGROUND ART
Conventionally, the positioning of an optical waveguide and an optical element has prevented cost reduction in the process of manufacturing an optical module. Particularly, accurate positioning in the order of micrometers (&mgr;m) has been required to achieve an optical coupling between an optical waveguide and a laser diode (LD) as an optical element. As an installation method for easily carrying out this positioning, there is a self-alignment installation method for the positioning by utilizing the surface tension of solder.
According to this installation method, a plurality of metal pads that become the basis of positioning are formed on a substrate, and solder bumps are prepared on these metal pads. On the optical part that is to be mounted on the substrate, metal pads that become the basis for the positioning are also provided corresponding to these metal pads on the substrate. Next, the optical part is provisionally mounted on the substrate based on rough positioning such that the metal pads are brought into contact with the solder bumps on the substrate. Last, the solder bumps are fused by heating the substrate, and the centers of the metal pads on the optical part side are attracted to the centers of the metal pads on the substrate side, based on the surface tension of the solder. As a result, the substrate and the optical part are positioned together with high precision.
According to this installation method, in order to carry out the positioning of an optical part and a substrate to be mounted with this optical part in higher precision, it is effective to reduce the diameter of each metal pad (Shingaku Giho, OQE
93-145, 1993
, pp. 61-66, (literature 1)). In the mean time, from the viewpoint of achieving compactness and integration, it has also been demanded to reduce the diameters of metal pads on the electronic part to which a similar self-alignment installation technique is applied. However, when the metal pads are made smaller, the permissible positioning error for the provisional mounting becomes smaller. This has had a problem of increasing the installation cost.
Further, as a modification of the above self-alignment installation method, Japanese Examined Patent Publication No.
6-26227
and Japanese Unexamined Patent Publication No.
9-181208
disclose an electric part installation method that permits a large permissible positioning error for the provisional mounting, by increasing the sizes of pads at the four corners.
FIG. 1
shows one example of this conventional part installation structure.
Referring to
FIG. 1
, a substrate
10
on which a square optical chip part
20
is to be mounted has four large pads
11
-
1
for rough positioning corresponding to four corners of this optical chip part
20
. On the periphery and center of this substrate
10
, a large number of small pads
11
-
2
are provided for fine positioning. Solder bumps are provided on these pads
11
-
1
and
11
-
2
respectively. In the meantime, the optical chip part
20
is also provided with large pads
21
-
1
and small pads
21
-
2
corresponding to the pads on the substrate. In this example, the optical chip part
20
is placed on the substrate
10
, with an angular deviation of &thgr; from a normal mounting position of the optical chip part
20
on the substrate.
According to this installation method, when the large pads
11
-
1
and the corresponding large pads
21
-
1
are in contact with each other via the solder bumps to provisionally mount the optical chip part
20
, the optical chip part
20
moves to a position where the small pads
21
-
1
of the optical chip part
20
are brought into contact with the corresponding solder bumps of the substrate based on the surface tension of the bumps of the large pads of the optical chip part
20
. All the pads are accurately positioned finally based on the surface tension of all the bumps.
However, when the optical chip part
20
is disposed on the substrate
10
, with an angular deviation of &thgr; from the normal mounting position on the substrate as shown in this example, the above positioning is not achieved. In order to provide larger tolerance for this angular deviation, it is necessary to further increase the sizes of the large pads
11
-
1
and
21
-
1
. In this case, the disposition area of the small pads
11
-
2
and
21
-
2
becomes smaller, and the number of these pads that can be disposed becomes smaller. Therefore, this method has had a problem in that the positional precision in the final positioning becomes lower.
DISCLOSURE OF INVENTION
In the light of the above problems, it is, therefore, an object of the present invention to provide a part installation structure that can permit larger tolerance of angular deviation in the provisional mounting as compared with that of the conventional technique, and that can realize the positioning with high precision.
According to a part installation structure of the present invention, it is possible to guarantee large tolerance of angular deviation for the part mounting, even when the conventional sizes of large pads are made smaller and/or the number of these pads is decreased. Therefore, it becomes possible to dispose small pads, in an increased number, in the increased area for disposing pads other than the large pads. As a result, it becomes easy to realize fine positioning in the order of &mgr;m that is necessary for the installation of an optical part. Further, according to the part installation structure of the present invention, there is provided an effective radiation structure for an optical part via a large metal pad that is disposed in the vicinity of the center of the optical part that has the large generation of heat of a laser diode or the like.
According to one aspect of the present invention, there is provided a part installation structure comprising: a substrate on which a plurality of first metal pads are formed; a part to be mounted having second metal pads corresponding to the positions of the first metal pads; and solder bumps for connecting between the first and second metal pads to match the installation positions of these metal pads based on the surface tension of the solder bumps when the solder bumps are fused, wherein the substrate and/or the mounted part has at least two metal pads having larger areas than those of other metal pads, in the vicinity of the center of the substrate and/or the mounted part.
According to another aspect of the present invention, there is provided a part installation structure comprising: a substrate on which a plurality of first metal pads are formed; a laser diode optical part having second metal pads corresponding to the positions of the first metal pads; and solder bumps for connecting between the first and second metal pads to match the installation positions of these metal pads based on the surface tension of the solder bumps when the solder bumps are fused, wherein the laser diode optical part has at least two metal pads having larger areas than those of other metal pads, in the vicinity of the center of the laser diode optical part, with the metal pads having large areas disposed immediately below an active layer of the laser diode optical part.
According to still another aspect of the present invention, there is provided a part installation method comprising the steps of: patterning a plurality of metal pads on a substrate and a part to be mounted respectively at corresponding positions, and preparing at least two metal pads having larger areas than those of other metal pads, in the vicinity of the center of the substrate and/or the mounted part; preparing solder bumps on the metal pads of the substrate or the mounted part; carrying out rough positioning such that the large metal pads are brought into contact with the facing solder
Nguyen Cuong
Staas & Halsey , LLP
LandOfFree
Installation structure and method for optical parts and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Installation structure and method for optical parts and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Installation structure and method for optical parts and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3135518