Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2001-08-28
2003-07-08
Cuneo, Kamand (Department: 2829)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C250S551000
Reexamination Certificate
active
06590232
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical coupling semiconductor apparatus having a light-emitting device and a light-receiving device which are sealed by plastic molding, and to a method for manufacturing the same.
2. Description of the Related Art
Among prior art semiconductor apparatus of this type, there is known a semiconductor apparatus with a double-layer molding seal as shown in
FIG. 12
, for example. As shown in
FIG. 12
, light-emitting device
103
and light-receiving device
104
are mounted on headers
101
a
and
102
a,
respectively, of previously bent lead frames
101
and
102
of a metal material, such as Cu alloy or Fe alloy, by connecting them to respective headers with an electrically conductive paste, such as Ag paste, (called “die bonding”). These devices
103
and
104
are connected to the corresponding lead frames by means of wires (called “wire bonding”).
The light-emitting device
103
is coated with a silicone resin (called “precoat”) to relieve stress, and the light-emitting device
103
and light-receiving device
104
are positioned to face each other by spot welding of the lead frames
101
and
102
or using a loading frame set. Further, an inner package
105
serving as an optical path between the light-emitting device
103
and the light-receiving device
104
is formed by primary transfer molding using a light-transmissive epoxy resin, followed by removal of resin burr resulting from leakage of excess resin.
Subsequently, an outer package
106
is formed by secondary transfer molding using a lightproof epoxy resin to prevent penetration of external disturbing light and leakage of internal light to the outside. Then, the lead frames
101
and
102
are plated for lead finishing. Further, an auxiliary lead portion, which plays two roles, i.e., tying and supporting of the lead frames
101
and
102
and prevention of resin leakage during transfer molding, is cut away (called “tie bar cutting”), and exposed lead portions of the lead frames extending from the outer package
106
are formed into external terminals (called “forming”).
In such a prior art apparatus, light emitted from the light-emitting device
103
advances straight to the light-receiving device
104
.
A reflection-type photocoupler disclosed in, for example, Japanese Unexamined Patent Publication JP-A 11-17212 (1999) is constructed as shown in FIG.
13
. Specifically, this photocoupler is constructed by: mounting light-emitting device
203
and light-receiving device
204
on lead frames
201
and
202
, respectively; covering the light-emitting device
203
and light-receiving device
204
with a silicone resin
205
to define an optical path between the light-emitting device
203
and the light-receiving device
204
(called “docking”); forming an outer package
206
by transfer molding using a lightproof epoxy resin; and performing finish-plating of the lead frames
201
and
202
, tie bar cutting, forming and the like.
In such a prior art photocoupler, as shown in
FIG. 14
, light emitted from the light-emitting device
203
is reflected by the interface defined between the silicone resin
205
and the outer package
206
and then reaches the light-receiving device
204
.
With respect to the prior art apparatus shown in
FIG. 12
, however, the headers
101
a
and
102
a
necessarily face each other because the light-emitting device
103
and the light-receiving device
104
are disposed facing each other. When the headers
101
a
and
102
a
in this state are sealed with the epoxy resin that will serve as the inner package
105
, a floating capacity (electrostatic capacity) results between the headers
101
a
and
102
a
. In this case, when the potential between the light-emitting device
103
and the light-receiving device
104
varies steeply, displacement current flows through the light-receiving device
104
and, hence, the output of the light-receiving device
104
is apparently changed, which causes a malfunction to occur.
With respect to the prior art photocoupler shown in
FIG. 13
, on the other hand, the light-emitting device
203
and the light-receiving device
204
do not face each other and, hence, the lead frames
201
and
202
do not face each other either. Accordingly, a very low floating capacity results. However, since light emitted from the light-emitting device
203
is dispersed within the silicone resin
205
and repeatedly reflected by the interface between the silicone resin
205
and the outer package
206
, the proportion of light absorbed by the interface or the like before light reaches the light-receiving device
204
is high, which raises a problem that a decrease or fluctuations in the efficiency of light transmission from the light-emitting device
203
to the light-receiving device
204
occur. In addition, since the silicone resin
205
is large in volume, possible thermal expansion thereof is likely to cause the outer package
206
to crack, thus resulting in an inconvenience such as penetration or leakage of light.
SUMMARY OF THE INVENTION
The invention has been made in view of the foregoing problems involved in the prior art, and accordingly, it is an object of the invention to provide an optical coupling semiconductor apparatus which is capable of raising and stabilizing the efficiency of light transmission from the light-emitting device to the light-receiving device and to provide a method for manufacturing the same.
According to the invention, there is provided an optical coupling semiconductor apparatus comprising:
a light-emitting device;
a light-receiving device;
lead frames carrying the light-emitting device and the light-receiving device, respectively, at locations spaced apart from each other; and
a light-transmissive resin projection having a longitudinally extending tapered vertex portion, the projection functioning as an optical path extending between the light-emitting device and the light-receiving device, having a nearly constant height, reflecting light emitted from the light-emitting device to gather the light to the vertex portion, and guiding the light thus gathered to the light-receiving device.
According to the invention, the light-transimissive resin projection having a constant height functions as an optical path extending between the light-emitting device and the light-receiving device, reflects light emitted from the light-emitting device to gather the light to the vertex portion thereof, and guides the light to the light-receiving device. Accordingly, light from the light-emitting device is guided to the light-receiving device without being dispersed. For this reason, the efficiency of light transmission from the light-emitting device to the light-receiving device is high and is stabilized.
In the invention, it is preferable that the light-emitting device and the light-receiving device have a light-emitting face and a light-receiving face, respectively, which are located on substantially the same reference plane.
According to the invention, it is possible to ensure a higher light transmission efficiency and minimize the floating capacity between the lead frames carrying the light-emitting device and the light-receiving device, respectively.
In the invention, it is preferable that the light-transmissive resin projection has a sectional configuration with the vertex portion and two sides defining the vertex portion.
According to the invention, the light-transmissive resin projection of such a sectional configuration is capable of reflecting light emitted from the light-emitting device at two inner wall surfaces facing each other to gather the light to the vertex portion, and guiding the light thus gathered.
In the invention, it is preferable that the light-transmissive resin projection is formed of an epoxy resin which is capable of setting through cationic polymerization.
According to the invention, this epoxy resin is preferred in terms of humidity resistance.
Further, in the invention, it is preferable that the light-transmissive resin projection is dome-
Cuneo Kamand
Sarkar Asok Kumar
Sharp Kabushiki Kaisha
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