Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2000-12-29
2003-09-23
Fourson, George (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S680000, C257S099000
Reexamination Certificate
active
06624491
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of optoelectronic components and more particularly to an improved housing design for a radiation sending and/or receiving device. Such device may comprise one or more optoelectronic chips, which are generally mounted on a chip supporting part of an electrical lead frame running through a base body. Common applications for such chips may include light emitting diodes (LED).
2. Description of Related Art
Housings for radiation sending and/or receiving devices are generally well known in the art. An example of prior art housings is set out in an article “Siemens-SMT-TOP-LED-LED's for Surface Mounting”, Siemens Components XXVI (1991), Nos. 4-5, pages 147 to 149. This article is herein incorporated by reference. The article discusses the state of the art, as of 1991, of surface mounted TOP LED's. A side by side comparison of TOP and radial LEDs is set out in
FIG. 4
of the article. A perspective view of a TOP LED is shown in
FIG. 1
of the article. The figure depicts a rounded portion at the top of the LED along with a side protruding conductor strip or electrode.
FIG. 2
, of the article, sets or depicts a cross section of the LED suggested in FIG.
1
. Herein, a punched conductor strip
1
is encased in a thermoplastic package
2
. The package
2
includes a top and bottom portion, the bottom portion being surrounded by the protruding conductor strip ends. The top portion of the package includes slanted, reflective and opposing sidewalls
3
. The sidewalls form a circular opening in the top portion of the package within which is mounted semiconductor chip
4
. The chip is consecutively mounted on a first portion of the punched conductor strip and further electronically connected (via a bonding wire) with the second portion of the punched conductor strip. The circular opening created by the sidewalls
3
is filled with a transparent epoxy resin. The resin is chosen such that the resin and package material are carefully balanced such that peak thermal stress will not cause mechanical damage. No such consideration is given to the selection of conductor strip
1
material. In operation, where, for example, the chip emits radiation, such radiation is reflected by the side walls
3
and emitted upwards through the window. Returning to
FIG. 4
of the article, the SMT LED is mounted within a case and optically coupled to a light guide to the front panel of the case. Application of LED technology includes visual displays both in harsh environments, such as engine compartments, and non-harsh environments, such as home displays.
An embodiment resembling the TOP LED is set out in the instant FIG.
4
. Herein, a housing
109
is depicted being generally made of a synthetic reflective material, such as a highly diffusive thermoplastic material as known to one skilled in the art. In the housing
109
, a radiation emitting semiconductor chip
101
is mounted on a flat chip carrier portion
102
of a flat surface area of a punched metallic conductor
103
. The conductor
103
is punched into two opposing, electrically isolated first and second portions,
103
a
and
103
b,
respectively, with chip
101
being mounted on the first portion
103
a.
The first portion further ends in an external connector
104
. Portion
104
facilitates transmission of electrical signals with chip
101
, from an external apparatus (not shown), via first portion
103
a
and carrier portion
102
. Chip
101
, via bonded wire
111
, is electrically connected to second portion
103
b
of the metal carrier frame. In particular, wire
111
is bonded at area
107
of the second portion
103
b.
The second portion further ends in external connector
105
which facilitates communication of electrical signals with chip
101
, from an external apparatus (not shown) via area
107
of second portion
103
b
and the connecting wire. Housing
109
further accommodates a transparent window
110
located above and around semiconductor chip
101
. The window may be made of any appropriate synthetic material known to one skilled in the art. A top portion of the window
110
is coplanar with a top surface of housing
109
. The side and bottom surfaces of
110
window
110
are defined by cooperation of side wall
120
surfaces
112
and carrier frame
103
. Sidewall surfaces
112
are angled with respect to frame
103
. Side wall surfaces
112
and portions of carrier frame
103
that directly abut window
110
may have reflective properties for select or all radiation present within window
110
. Semiconductor
101
may be radiation emissive and/or receptive.
A drawback with the above discussed arrangements, as briefly alluded to in the prior art reference, stems from the delamination of the window
110
carrier frame
103
. Such delaminating may result from temperature variations in the housing's operating environment, such as proximate to an automobile engine or manufacturing (e.g. soldering) requirements. The temperature variations effect the thermal coefficients of the window, side walls and carrier frame causing dimensional changes in each at possibly differing rates. By way of example, frame
103
may be metal and window
110
may be a transparent epoxy resin. Hence, as a result of temperature fluctuations, the window
110
often separates from frame
103
. Such gaps result in radiation absorption and/or internal reflections thereby diminishing the amount of radiation being emitted from or incident to chip
101
. Hence the operating efficiency of the entire housing is effected. Furthermore, the gap can continue between carrier frame and window to sidewalls
120
starting from the gap between carrier frame
103
and window
110
thereby opening the housing up to moisture penetration which will damage the chip and accelerate delimitation.
U.S. Pat. No. 5,985,696 sets out application of a semiconductor chip in a rounded LED. The reference discloses a method for producing optoelectric semiconductor components wherein the chip carrier is supported by a plastic base and electrodes run through the base. A lens is further mounted above the chip. A cap is form fitted to a holder and attached with the base. The plastic base is one of many arranged successively in a chip carrier strip. The base is injection molded and the component is separated from the chip carrier strip only after the base is produced, the chip is attached and bonded to the electrodes.
U.S. Pat. No. 6,066,861 sets out an arrangement for a white light emitted diode. The arrangement includes an inorganic luminous substance pigment powder with luminous substance pigments dispersed in a transparent epoxy casting resin. The material is spaced proximate to a semiconductor radiation source such that the material luminesces, thereby converting the source radiation into a second wavelength.
FIG. 3
sets out an embodiment whereby angled sidewalls and a base cooperate to form a bound area for the luminescing material.
German patent DE 19536454 discloses a semiconductor chip mounted on a lead frame and housed in a recess of a component base. A reflective layer is coated on the lead frame so as to reflect radiation emitting from the chip. Angled sidewalls further cooperate with a planar base to form the boundaries of the window.
BRIEF SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an improved housing arrangement for a radiation emitting and/or receiving semiconductor chip to use in TOP LEDs, rounded LEDs and the like. It is a further object to provide a component, which can be implemented so as to enable mass production at reasonable engineering effort and expense and with maximally replicable component characteristics. It is still a further object of the present invention to prolong the life of the component via improved delamination resistance as well as improved radiation reception and emission characteristics. In still a further object of the present invention to increase radiation input/output efficiency with the semiconductor chi
Brunner Herbert
Waitl Gunther
Cohen & Pontani, Lieberman & Pavane
Estrada Michelle
Fourson George
Osram Opto Semiconductors GmbH & Co.
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