Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With housing or contact structure
Reexamination Certificate
1999-10-22
2001-01-30
Tran, Minh Loan (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With housing or contact structure
C257S100000, C257S787000
Reexamination Certificate
active
06180962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to chip type semiconductor light emitting devices and, more particularly, to a chip type semiconductor light emitting device having a semiconductor light emitting chip connected to an electrode and molded together with part of the electrode by a resin, such as epoxy.
2. Description of the Prior Art
There is known a structure shown in
FIG. 7
as a chip type semiconductor light emitting device of this kind.
FIG. 7
is a perspective view showing, by partly seeing through, a chip type semiconductor light emitting device
1
. In
FIG. 7
, a pair of electrodes
3
,
4
are formed, and the electrode
4
is formed with a pad
4
b
. Reference characters
3
a
,
4
a
respectively represent terminal portions of the pair of electrodes
3
,
4
.
A semiconductor light emitting chip (hereinafter abbreviated as “LED chip”)
5
has, on its top surface, an electrode
5
a
electrically connected by wire-bonding to the electrode
3
through using a metal wire
6
. Also, the LED chip
5
is bonded on the pad
4
b
of the electrode
4
through a conductive paste. The LED chip
5
at its backside electrode is electrically connected to the electrode
4
. The LED
5
and the metal wire
6
are encapsulated together by a mold
7
using a translucent synthetic resin. Meanwhile, each electrode
3
,
4
has a terminal portion
3
a
,
4
a
extending outside the mold
7
to a backside of the substrate through a side surface thereof.
In this manner, in the example of
FIG. 7
the LED chip
5
and the metal wire
6
are encapsulated in a state that the mold
7
at its end faces is partly jointed to the terminal portions
3
a
,
4
a
of the electrodes
3
,
4
. The chip type semiconductor light emitting device
1
is mounted with an backside of the substrate
2
positioned down on a surface of a circuit board, and subjected to a reflow process so that the terminal portions
3
a
,
4
a
of the electrodes
3
,
4
are brought into electrical connection through solder onto a circuit pattern of the circuit board.
FIG. 8
is a sectional view showing, by magnification, a structure of the electrode and terminal portion formed on the substrate
2
. On the substrate
2
, a copper (Cu) layer is first formed and then a nickel (Ni) layer and gold (Au) layer are formed on the copper layer by electroplating. Thus, Cu, Ni and Au three conductive layers are formed on the substrate
2
.
The Au layer thus formed on the surfaces of the pair of electrodes and terminal portions makes it easy to deposit solder on the terminal portions. Furthermore, where a gold wire is used as a wire-bonding metal wire, preferred electrical connection is provided between the metal wire and the electrode, thus improving the quality of the semiconductor light emitting device
1
.
In the case where the semiconductor light emitting device
1
mounted on a circuit board experiences repetition of a reflow process, if the amount of a solder melt is comparatively much, the solder melt may flow along an Au layer on a terminal portion
3
a
,
4
a
and intrude at a mold
7
end face toward an electrode
3
,
4
.
FIG. 9
is a perspective view depicting a state that a solder melt
8
flows, as shown by an arrow X, from one terminal portion
3
a
through a mold
7
end face and intrudes to the electrode
3
.
If the solder
8
flows along the Au layer on the surface of the terminal portion
3
a
,
4
a
and intrudes through the mold
7
end face to the electrode
3
,
4
as shown in
FIG. 8
, there is a possibility that the metal wire
6
that is wire-bonded to the electrode
3
be broken due to an impact caused by the solder melt
8
or the LED chip
5
be stripped off the pad
4
b
of the electrode
4
. If the metal wire
6
or the semiconductor light emitting chip
5
is damaged due to intrusion of solder
8
, a problem results that the semiconductor light emitting device
1
would not operate normally.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-stated problems, and it is an object to provide a semiconductor light emitting device having parts prevented from being damaged by solder even where solder intrude toward an electrode formed inside a mold during a reflow process.
A semiconductor light emitting device according to the present invention, comprises: a substrate; a pair of electrodes formed on said substrate; a semiconductor light emitting chip electrically connected to said pair of electrodes; a mold formed of a translucent synthetic resin and encapsulating said semiconductor light emitting chip and respective portions of said pair of electrodes; and solder preventive portion formed over an entire width of said electrode at an inside of said mold.
Even if solder flows along an electrode surface from an outside of the mold and intrudes into an inside of the mold, the solder entering is prevented from further advancing by the solder preventive portion. Accordingly, with this invention there is less possibility that the semiconductor light emitting chip or the like be damaged by solder upon conducting solder reflow.
In one embodiment, the above object of the invention is achieved by providing, in a semiconductor light emitting device having a substrate, a pair of electrodes, a semiconductor light emitting chip electrically connected to the pair of electrodes, and a mold formed of a translucent synthetic resin and encapsulating the semiconductor light emitting chip, wherein the pair of electrodes are provided extending from an inside to an outside of the mold to have a surface formed by a gold layer, a disconnection in part of the electrode inside the mold.
In this embodiment, because the disconnection is partly provided in the electrode inside the mold, even if solder flows along the gold layer formed in the surface of the terminal portion and intrudes to the electrode at an inside of the mold during a reflow process, the flow of solder will be stopped by the disconnection of the metal layer. Accordingly, it is possible to prevent the parts of the semiconductor light emitting device from being damaged by solder and hence provide normal operation for the semiconductor light emitting device.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5612512 (1997-03-01), Wakamatsu et al.
patent: 5962917 (1999-10-01), Moriyama
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patent: 02281648 (1990-11-01), None
patent: 08250841 (1996-09-01), None
patent: 8-330637 (1996-12-01), None
patent: 10075041 (1998-03-01), None
patent: 10-275875 (1998-10-01), None
Kristufek, et al.,8229 Siemens Components, entitled “Large-area displays with SMT-TOP-LED”, 29 (1994) Mar./Apr., No. 2, Berlin, DE, pp. 30-32.
Hoffman & Baron LLP
Rohm & Co., Ltd.
Tran Minh Loan
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