Patent Grant
7183632
The invention relates to a surface-mountable light-emitting diode (SMD) structural element in which an optoelectronic chip is attached to a chip carrier part of a lead frame via a heat-conducting connection. The lead frame has a connecting part disposed at a distance from the chip carrier part which is connected with an electrically conducting electrical contact of the optoelectronic chip. The optoelectronic chip and a part of the lead frame are encased by a casing forming a foundation, whereby the foundation has a first main surface and a second main surface opposite the first main surface. The external connections of the chip carrier part and the connection part provided in the lead frame project outside the casing, whereby the external connections are either bent outside the foundation at first to the second main surface of the foundation opposite the first main surface and in the further course either below the foundation to its center or are bent away to form rocker-shaped connection stumps. It particularly relates to an optoelectronic structural element with an optoelectronic semiconductor chip, especially with a light-diode chip (LED) operated at a high output.
Such a structural element is known, for example from Published, European Patent Application EP 0 400 176 A. A so-called TOPLED is described here, in which a light-emitting semiconductor chip (LED chip) is attached to a flat chip carrier part of a lead frame. The lead frame consists of a chip carrier part with external connections and a connection part disposed at a distance from the latter, thus electrically insulated from it. The chip carrier part with the semiconductor chip, the connection part, and partial areas of the external connections are encased by a casing consisting of an emission-impermeable foundation with a recess and an emission-permeable window part filling this recess. The chip carrier part and the connection part are encased by the foundation or are embedded in it so that partial areas of upper sides of the chip carrier part and the connection part with the remaining floor surface tightly close the recess. The semiconductor chip is completely encased by the emission-permeable window part except for its lower side, with which it lies on the chip carrier part. The recess and its inner surfaces are formed and disposed so that they form an essentially truncated cone-shaped reflector for the radiation emitted by the semiconductor chip.
An optoelectronic structural element is described in Published, Non-Prosecuted German Patent Application DE 195 36 454 A1 in which, to improve the heat conduction of the semiconductor chip, two external connections of the chip carrier part of the lead frame are widened opposite the external connections of the connection part.
In the case of the known optoelectronic structural elements described above, the semiconductor chip operates at high currents and thereby high output, as for example is the case with so-called power-LEDs, leading to high heating because of insufficient heat conduction from the semiconductor chip. This heating frequently leads to impairments of the functional ability of the semiconductor chip, such as accelerated aging, breaking off of the semiconductor chip from the lead frame, breakage of the semiconductor chip away from the lead frame, breaking away of bond wires, or destruction of the chip. The known widened external connections of the chip carrier part favor delamination of plastic from the lead frame that, for example, can cause penetration of moisture to the semiconductor chip.
It is accordingly an object of the invention to provide a surface-mountable light-emitting diode structural element that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which improved heat conduction from the chip is assured, without at the same time substantially altering the housing dimensions and without at the same time substantially increasing delamination danger.
With the foregoing and other objects in view there is provided, in accordance with the invention, a surface-mountable, light-emitting diode (SMD) structural element that is formed of a lead frame having a chip carrier part, three separate external connections, and a connection part disposed at a distance from the chip carrier part. The three separate external connections extend outward in three different directions, starting from the chip carrier part. A light-emitting semiconductor chip is heat-conductively connected to the chip carrier part of the lead frame. The light-emitting semiconductor chip has an electrical contact electrically conductively connected to the connection part. A casing is provided and has a foundation encasing the chip carrier part, the connection part and partial areas of the three separate external connections. The foundation has a first main surface, a recess formed therein, and an outward facing second main surface disposed opposite the first main surface. The three separate external connections and the connection part project outside of the casing. The three separate external connections and the connection part are bent outside of the foundation toward the outward-facing second main surface of the foundation and in a further course are further bent below the foundation toward a center of the outward-facing second main surface or away from the foundation for forming rocker-shaped connection stumps. The three separate external connections project from the casing on at least two sides of the casing at different places at a distance from each other. The heat-conducting connections as seen in a top view of the lead frame project from the casing on at least two sides and starting from the chip carrier part run toward the outside in a stellate form within the casing and separately from each other. The light-emitting semiconductor chip is disposed in the recess.
In the structural element according to the invention, it is provided for the chip carrier part to have at least three separate thermally conducting external connections connected with the chip carrier part which project from the casing at different places at a distance from each other and are configured so that they all simultaneously lie on the connection or lead plate in the assembled state of the structural element provided for mounting the structural element. The heat resulting in the chip in the operation of the structural elements is consequently fed into the lead plate at three different points and is distributed on a broad surface of the latter. A distinctly improved heat conduction from the optoelectronic chip is thereby obtained.
In a particularly preferred form of the structural element according to the invention, the external connections of the chip carrier part, in a top view of the lead frame, run separately from each other in an essentially stellate form, starting from the chip carrier part. The heat conduction points from the structural element to the lead plate thereby present large distances from each other, whereby a very large-surface distribution of the thermal energy derived from the chip in the operation of the structural element is conducted away by way of the chip carrier part and its external connections.
The external connections in the area in which they run outward in a star shape advantageously present longitudinal central axes, wherein two adjacent connections always present an angle of about 90° to each other. In this configuration, the plastic area between the connections is maximum, whereby the delamination danger is reduced, for example in the case of temperature fluctuations.
If the structural element is provided with at least a first and a second optoelectronic chip, the chip carrier part according to the invention presents at least two external connections which project from the casing at various places on it with a distance between them. The lead frame here presents at least two connection parts with an external connection in each case, which also project sideways from the casing. It is also preferable here for the external connections of the chip carrier part and the connection parts, viewed from the top of the lead frame, to essentially be disposed in the stellate form, whereby a maximum interval of the external connections of the chip carrier part from each other is assured. The thermal energy conducted from the chip in the operation of the structural element by way of the chip carrier part and its external connection is thereby fed into the lead plate at points located relatively far from each other, so that here, too, a very good heat distribution on the lead plate is obtained.
In the case of the last-mentioned structural element, it is especially advantageous for the external connections of the chip carrier part, viewed from a top view of the lead frame, to be disposed displaced diagonally to each other. They project from the chip carrier part on side surfaces opposite each other of the casing having a preferably essentially square shape. The connection parts are thereby disposed on different sides of the chip carrier part, and their external connections likewise project on side surfaces of the casing opposite each other. From a view of the lead frame, concerning the chip carrier part, they are disposed displaced diagonally to each other in relation to the external connections of the chip carrier part.
In order to further improve heat conduction from the chips, if necessary, the chip carrier part can present more than two external connections, which again project from the casing at various places at a distance from each other. The number of the external connections can be increased further as required according to the permissible structure size of the structural element.
In the case of the structural element in accordance with the invention which can be attached to the lead plate so that, in its operation, the radiation emitted by the chip is radiated essentially parallel to the lead plate (laterally emitting structural element), the chip carrier part exhibits at least two external connections and the connection part at least one external connection which project separately from each other at one and the same side surface of the casing. The external connection of the connection part is thereby preferably disposed between the two external connections of the chip carrier part.
In an especially preferred further development of the last-mentioned structural element, the external connection of the connection part is narrower than the two external connections of the chip carrier part. Of course, the external connections of the chip carrier part can optionally also be wider than the external connections of the connection parts.
In a further development of the above mentioned side-emitting structural element, the chip carrier part is additionally provided with greater heat conduction via at least one heat-conducting cooling fin, which projects from a side surface of the casing other than from where the connection parts project. The cooling fin alone or a further cooling device thermally attached to the cooling fin assures a still further improved heat conduction from the chip.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a surface-mountable light-emitting diode structural element, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
a is a diagrammatic, top plan view of a first embodiment of a structural element with a single optoelectronic chip according to the invention;
b is a schematic representation of a section through the structural element of
a is a side-elevational view of a third embodiment of the structural element with emission to a side; and
b is a section view through the structural element of
In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. Referring now to the figures of the drawing in detail and first, particularly, to
If the cathode contact is not disposed on a lower side of the chip 1, as in the above mentioned case, but instead on its upper side, for example, it can be connected electrically conductively with the chip carrier part 2 by a bond wire.
The chip carrier part 2, the connection part 8, and partial areas of the external connections 4, 5, 6, 9 are encased by an essentially square foundation 10 of a casing 3, which has a recess 11 (
Starting from the chip carrier part 2, the external connections 4, 5, 6 run apart within the foundation 10 first in a stellate form and then break in their further course, so that they penetrate the side surfaces 18, 19 perpendicularly.
The chip carrier part 2 preferably lies completely within a floor surface of the recess 11.
The external connections 4, 5, 6 have longitudinal center axes 23, 24, 25 in an area in which they run outwards in the stellate form, two adjacent units of which always form an angle of about 90°.
The external connections 4, 5, 6, 9 are bent outside of the foundation 10 first to a second main surface 20 of the foundation 10 opposite the first main surface 17 and in their further course below the foundation 10 to its center. However, as is indicated by the dotted line in
The external connections 4, 5, 6, 9 are consequently formed so that they all lie simultaneously on the connection or lead plate in the assembled state of the structural element in the lead plate provided for assembling the structural element.
Inner surfaces of the recess 11 form a reflector for the emission radiated by the LED chip 1 in the operation of the structural element. They are optionally coated with a reflection-enhancing material. The foundation 10 can alternatively consist of a reflection-enhancing material.
In the execution example of
The chip carrier part 2 exhibits the two external connections 4, 5 which, starting from the chip carrier part 2, likewise extend displaced parallel to each other in opposite directions parallel to the external connections 9, 14 of the connection parts 8, 12 and project out on the opposite side surfaces 18, 19 of the foundation 10.
As in the case of the first embodiment of
The external connections 4, 5, 9, 14 project out of the foundation 10 on the opposite side surfaces 18, 19. They are formed outside the foundation 10 analogously to the first embodiment according to
In the case of the first and second embodiments of
The execution example of
Moreover, the lead frame 7 has the chip carrier part 2, which has at least two of the external connections 4, 5. Starting first from the chip carrier part 2, to which the LED chip 1 is attached by a thermally and electrically conducting material, the external connections 4, 5 extend in essentially opposite directions to the outside. In their further course, they break in the same direction, so that they then run parallel to each other in the same direction. The connection part 8 with the external connection 9, which runs parallel to the two external connections 4, 5 of the chip carrier part 2 in the same direction that they run, is disposed between the two external connections 4, 5 of the chip carrier part 2.
The chip carrier part 2, whose external connections 4, 5, and the connection part 8 with the external connection 9 are enclosed by the radiation-impermeable foundation 10 analogously to the first and second embodiments described above, which has the truncated cone recess 11, is disposed in the LED chip 1. Here, too, the recess 11 is provided with the emission-permeable window part 22, which preferably consists of an emission-permeable plastic. The external connections 4, 5, 9, which project from it on one and the same side surface 18 of the foundation 10, are bent downward outside the foundation 10 in the direction of the back side of the foundation 10 and are bent in their further course along a back side 21 of the foundation 10 to its center. The outer surfaces of the external connections 4, 5, 9 turned away from the side surface 18 of the foundation 10 form a support surface of the structural element for its mounting on the lead plate.
For additional cooling of the LED chip 1, the chip carrier part 2 has cooling fin 15 (indicated by dotted line in
In all the embodiments described above, it is preferable for the external connections of the chip carrier part 2 to be wider than the external connections of the connection part or parts 8, 12. A further improved heat transfer from the LED chip 1 can thereby be attained with substantially unchanged housing dimensions. However, the external connections 4, 5, 6, 9, 14 can all have the same width.
Especially large soldering pads are provided on the lead plate provided for the assembly of the structural element in order to attain a further improvement in heat transfer from the LED chip 1. They are also disposed in the stellate form and can thus distribute the heat conducted from the LED chip 1 over a large surface. The lead frames 7 of the structural elements according to the invention conduct the heat from the LED chip 1 in the stellate form to the outside of the casing 3. The heat is thereby fed to points in the plate lying far from each other.
Large metal linings consisting of copper are preferably located on the plate around each soldering pad, which distribute the heat on the lead plate. The heat resistance of the casing (housing) 3 according to the invention is distinctly reduced in comparison with the heat resistance of commercial housings.
The housing 3 for the LED chips 1 described above relates to a housing for optoelectronic structural elements known in semiconductor technology. The separate forms and the materials and manufacturing processes used therefore will not be explained further.
To be sure, the description of the invention on the basis of the disclosed embodiments is not to be understood to be a limitation of the invention to these examples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 197 32 646 | Jul 1997 | DE | national |
This application is a continuation application of U.S. application Ser. No. 10/882,518, filed Jul. 1, 2004, now U.S. Pat No. 7,102,215 which is a continuation of U.S. application Ser. No. 10/407,734, filed Apr. 4, 2003, now U.S. Pat. No. 6,759,733, which was a divisional application of U.S. application Ser. No. 10/259,556, filed Sep. 27, 2002, now U.S. Pat. No. 6,573,580, which was a divisional application of U.S. application Ser. No. 10/072,836, filed Feb. 5, 2002, now U.S. Pat. No. 6,469,321 B2, which was a divisional application of U.S. application Ser. No. 09/494,771, filed Jan. 31, 2000, now U.S. Pat. No. 6,376,902 B1, which was a continuation of PCT/DE98/02125, filed Jul. 27, 1998 which designated the United States, which claimed priority to German application no. 197 32 646.3, filed Jul. 29, 1997. The contents of the prior applications are incorporated herein by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3529200 | Potter et al. | Sep 1970 | A |
| 3573568 | Siegel | Apr 1971 | A |
| 3742833 | Sewell et al. | Jul 1973 | A |
| 3774086 | Vincent, Jr. | Nov 1973 | A |
| 3976877 | Thillays | Aug 1976 | A |
| 4203792 | Thompson | May 1980 | A |
| 4307297 | Groff et al. | Dec 1981 | A |
| 4727457 | Thillays | Feb 1988 | A |
| 4780795 | Mainel | Oct 1988 | A |
| 4843280 | Lumbard et al. | Jun 1989 | A |
| 4851695 | Stein | Jul 1989 | A |
| 4875750 | Spaeth et al. | Oct 1989 | A |
| 4935856 | Dragoon | Jun 1990 | A |
| 4955820 | Yamada et al. | Sep 1990 | A |
| 5014418 | Wright | May 1991 | A |
| 5035483 | Waitl et al. | Jul 1991 | A |
| 5093713 | Sawaya | Mar 1992 | A |
| 5146310 | Bayan et al. | Sep 1992 | A |
| RE34254 | Dragoon | May 1993 | E |
| 5273460 | Arai | Dec 1993 | A |
| 5289344 | Gagnon et al. | Feb 1994 | A |
| 5294897 | Notani et al. | Mar 1994 | A |
| 5367124 | Hoffman et al. | Nov 1994 | A |
| 5479050 | Pritchard et al. | Dec 1995 | A |
| 5543657 | Diffenderfer et al. | Aug 1996 | A |
| 5608553 | Kim | Mar 1997 | A |
| 5659950 | Adams et al. | Aug 1997 | A |
| 5677245 | Brown et al. | Oct 1997 | A |
| 5685071 | Gates, Jr. et al. | Nov 1997 | A |
| 5706177 | Nather et al. | Jan 1998 | A |
| 5844305 | Shin et al. | Dec 1998 | A |
| 5863810 | Kaldenberg | Jan 1999 | A |
| 5907151 | Gramann et al. | May 1999 | A |
| 6066861 | Hohn et al. | May 2000 | A |
| 6376902 | Arndt | Apr 2002 | B1 |
| 6469321 | Arndt et al. | Oct 2002 | B2 |
| 6573580 | Arndt | Jun 2003 | B2 |
| 6759733 | Arndt | Jul 2004 | B2 |
| Number | Date | Country |
|---|---|---|
| 1915290 | Oct 1969 | DE |
| 7128442 | Dec 1971 | DE |
| 2347289 | Apr 1974 | DE |
| 2829260 | Jan 1980 | DE |
| 3227645 | Jan 1984 | DE |
| 4446566 | Jun 1996 | DE |
| 19536454 | Apr 1997 | DE |
| 0373003 | Jun 1990 | EP |
| 0 400 176 | Dec 1990 | EP |
| 0532974 | Mar 1993 | EP |
| 646971 | Apr 1995 | EP |
| 2004989 | Dec 1969 | FR |
| 51145288 | Dec 1976 | JP |
| 5368992 | Jun 1978 | JP |
| 58-194382 | Nov 1983 | JP |
| 61-248839 | Nov 1986 | JP |
| 60090680 | Nov 1986 | JP |
| 62263663 | Nov 1987 | JP |
| 62263667 | Nov 1987 | JP |
| 63052455 | Mar 1988 | JP |
| 01117227 | May 1989 | JP |
| 2156558 | Jun 1990 | JP |
| 03171682 | Jul 1991 | JP |
| 3250657 | Nov 1991 | JP |
| 03287690 | Dec 1991 | JP |
| 4062942 | Feb 1992 | JP |
| 4067462 | Mar 1992 | JP |
| 4128811 | Apr 1992 | JP |
| 4139732 | May 1992 | JP |
| 05315652 | Nov 1993 | JP |
| 05315653 | Nov 1993 | JP |
| 06053554 | Feb 1994 | JP |
| 6163083 | Jun 1994 | JP |
| 06204570 | Jul 1994 | JP |
| 6204604 | Jul 1994 | JP |
| 7176794 | Jul 1995 | JP |
| 07335980 | Dec 1995 | JP |
| 8007614 | Jan 1996 | JP |
| 09303981 | Nov 1997 | JP |
| WO 9820718 | May 1998 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20060197103 A1 | Sep 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10259556 | Sep 2002 | US |
| Child | 10407734 | US | |
| Parent | 10072836 | Feb 2002 | US |
| Child | 10259556 | US | |
| Parent | 09494771 | Jan 2000 | US |
| Child | 10072836 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10882518 | Jul 2004 | US |
| Child | 11397914 | US | |
| Parent | 10407734 | Apr 2003 | US |
| Child | 10882518 | US | |
| Parent | PCT/DE98/02125 | Jul 1998 | US |
| Child | 09494771 | US |
