Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
1998-01-13
2001-08-14
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S099000, C257S100000, C257S789000, C257S795000
Reexamination Certificate
active
06274890
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor light emitting device used in indicators, message boards, or other visual display devices, which is improved in adherability of a resin encapsulating element and a resin stem, and also relates to a method for manufacturing same.
2. Description of the Prior Art
In conventional semiconductor light emitting devices, after a semiconductor light emitting element is mounted and bonded to a printed board with a printed wiring, a light-transmissive resin is injected into a cavity defined by a case mold capped onto the printed board to form an encapsulating element having a lens function.
These semiconductor light emitting devices are expensive, and the injected resin often leaks. Moreover, chips, unfilled portions or bubbles are liable to be made in the encapsulating element, resulting that the devices are not satisfactory in their appearances. Additionally, the use of an expensive printed board and a slow injection speed cause a high manufacturing cost.
On the other hand, a surface-packaged semiconductor light emitting device having no lens is as shown in
FIG. 22. A
resin stem
10
has formed a recess
7
, and a semiconductor light emitting element
1
is put on the bottom of the recess
7
. The sloped side walls
8
of the recess
7
functions as light reflective surfaces. Leads
21
and
22
are embedded in the resin stem
10
. The leads
21
,
22
are incorporated by molding a lead frame in form of a thin Fe- or Cu-based metal plate. The resin stem
10
is made by injection-molding a thermoplastic resin such as polycarbonate (PC) containing a filler agent such as silica (SiO
2
) together with the lead frame. End portions of the leads
21
,
22
for contact with the semiconductor light emitting element lie on the bottom surface of the recess
7
of the resin stem
10
. The semiconductor light element
1
is mounted on the lead
21
by conductive paste
3
, or the like, containing silver (Ag), for example. A first electrode of the semiconductor light emitting element
1
is connected to the lead
21
, and a second electrode is electrically connected to the lead
22
. The second electrode and the lead
22
are connected by a bonding wire
4
of gold (Au), for example. A light-transmissive resin encapsulating element
5
of a thermosetting resin is applied onto the resin stem
10
so as to cover these end portions of the leads
21
,
22
, semiconductor light emitting element
1
and bonding wire
4
.
However, the surface-packaged semiconductor light emitting device shown in
FIG. 22
has no lens, and is unreliable in adherability between the resin encapsulating element of a thermosetting resin and a resin stem of a thermoplastic resin.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an inexpensive semiconductor light emitting device and its manufacturing method, which permits a lens to be made easily, and is improved in adherability and humidity resistance between the resin encapsulating element and the resin stem, and also improved in reflecting efficiency and light take-out efficiency.
According to the invention, there is provided a semiconductor light emitting device comprising: a semiconductor light emitting element made by using GaP, GaAlAs, GaAsP, InGaAlP, GaN, ZnSe, SiC, BN, for example; a resin stem having a first lead, a second lead and a resin portion partly covering the first and second leads, one end of the first lead and one end of the second lead being externally extended from the resin portion, and the resin stem having a recess containing the semiconductor light emitting element, the other end of the first lead electrically connected to a first electrode of the semiconductor light emitting element, and the other end of the second lead electrically connected to a second electrode of the semiconductor light emitting element; a light-transmissive resin filling the recess of the resin stem; and a projection made of a light-transmissive resin to cover the entire upper surface of the resin stem, the projection extended down onto side surfaces of said resin stem to a predetermined level from the upper surface to continuously cover the upper part of the side surfaces all around.
The resin stem may have at least one through hole in the bottom of the recess or at least one through hole extending from the upper surface to the lower surface. The projection may form a lens having a vertical axis aligned with a vertical axis of the resin stem, and these center axes may be aligned with a vertical axis of the semiconductor light emitting element. The semiconductor light emitting device may include a fluorescent element for converting light emanating from the semiconductor light emitting element into different wavelength light. The fluorescent element may be contained in the resin portion of the resin stem, may be applied onto inner wall surfaces of the recess of the resin stem, or may be contained in a mounting adhesive applied onto the bottom surface of the semiconductor light emitting element, in the light-transmissive resin filling the recess, or in the light-transmissive resin forming said projection.
The recess of the resin stem may be longer in a first horizontal direction in which the first and second leads extends than in a second horizontal direction normal to the first direction. The first electrode of the semiconductor light emitting element may be connected to the first lead by a bonding wire, and the second electrode of the semiconductor light emitting element may be connected to the second lead by another bonding wire. The center of a horizontal cross-sectional configuration of the recess of the resin stem may be offset from the center of a horizontal cross-sectional configuration of the resin stem. The second electrode of the semiconductor light emitting element may be connected to the second lead by a bonding wire, and the center of a horizontal cross-sectional configuration of the recess of the resin stem may be offset from the center of a horizontal cross-sectional configuration of the resin stem toward the externally extending direction of the second lead. Inner side surfaces of the recess may serve as reflective surfaces.
The resin portion of the resin stem is made from a thermoplastic resin not less than 65 weight % and a filler agent not more than 35 weight %, the filler agent being a high reflective material containing titanium oxide, silicon oxide, and/or aluminum oxide, and titanium oxide occupying 10 to 15 weight %.
There is also provided a method for manufacturing a semiconductor light emitting device comprising the steps of:
forming a resin stem by integrally molding a lead frame having first and second leads and a resin portion such that the first and second leads be positioned in an end-to-end alignment in a recess formed in the upper surface of the resin portion; mounting a semiconductor light emitting element having first and second electrodes in the recess, and electrically connecting the first lead to the first electrode and the second lead to the second electrode; injecting a fluid-state thermosetting resin into an encapsulating case mold; dipping the upper surface of the resin stem and upper parts of side surfaces continuous from the upper surface into the fluid-state resin in the encapsulating case mold; and hardening the fluid-state resin to form a projection of a light-transmissive resin on the resin stem, in which the projection covering the entire upper surface of the resin stem, and extended down onto side surfaces of the resin stem to a predetermined level from the upper surface to continuously cover the upper part of the side surfaces all around.
According to the invention, there is provided an alternative method for manufacturing a semiconductor light emitting device comprising the steps of: forming a resin stem by integrally molding a lead frame having first and second leads and a resin portion such that the first and second leads are positioned in an end-to-end alignment in a recess formed in the upper surface
Komoto Satoshi
Matsumoto Iwao
Nagasawa Hiroshi
Oshio Hiroaki
Uchino Tsuguo
Hogan & Hartson LLP
Jackson, Jr. Jerome
Kabushiki Kaisha Toshiba
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