Optoelectronic device

0001The invention relates to an optoelectronic component, in which an optoelectronic chip by means of a good heat conducting connection means on a chip carrier part of a lead frame (lead frame) is secured, the lead frame one is arranged in a distance from the chip carrier part, electrically conductively connected to an electrical contact of the chip connection part , and wherein the chip and at least one partial region of the chip carrier part and the connecting part are surrounded by a sheath, such that specific for a circuit board assembly, protrude provided in the lead frame external terminals of the chip carrier part and of the connection part of the wrapping or completely outside of the envelope lie. It relates more particularly to an optoelectronic component having an optoelectronic semiconductor chip, in particular a driven at high power light-emitting diode chip (LED).

0002Such a component is, for example from the European patent application <patcit id="pcit0001" dnum="EP400176A"><text>EP 400 176</text></patcit> known. Herein, a so-called TOPLEDs is described in which a semiconductor light emitting chip (LED chip) is mounted on a planar chip carrier part of a lead frame. The leadframe is made up of the chip carrier part and one at a distance from this, therefore electrically insulated from this arranged connector with one external port. The chip carrier part to the semiconductor chip, the connecting portion and portions of the external terminals are surrounded by an envelope which consists of a radiation-opaque base body with a recess and a recess fills these radiation-transmissive window part. The chip carrier part and the connecting part are so surrounded by the base body or embedded in this, that portions of the upper sides of the chip carrier part and the connecting part are flush with the remaining bottom surface of the recess. The semiconductor chip is completely enclosed except for its bottom, with which it rests on the chip carrier part of the radiation-transmissive window part. The recess and the inner surfaces thereof are shaped and arranged such that it forms a substantially truncated cone-shaped reflector for the radiation emitted by the semiconductor chip radiation.

0003In the <patcit id="pcit0002" dnum="DE19536454A1"><text>DE 19536454A1</text></patcit> is described an optoelectronic device, wherein the two external terminals of the chip carrier part of the lead frame with respect to the external terminals of the connecting part are widened in order to improve the heat dissipation from the semiconductor chip.

0004In the document <patcit id="pcit0003" dnum="US5146310A"><text>US 5146310</text></patcit> two wide connections of the chip carrier part of a lead frame for heat dissipation at widely separated points of contact are described.

0005In the above described known optoelectronic devices occurs in operation of the semiconductor chips at high currents and thus at high power, as is the case for example in so-called power LEDs, due to insufficient heat dissipation from the semiconductor chip to its intense heating. This heating often leads to interference with the functioning of the semiconductor chip, such. As accelerated aging, cancel the semiconductor chip from the lead frame, cancel the bond wires or destruction of the chip. The known widened external terminals of the chip carrier part promote delamination of the plastic from the lead frame, the z. B. the penetration of moisture can cause the semiconductor chip.

0006The invention is therefore based on the object, the optoelectronic component of the aforementioned type such that an improved heat dissipation is ensured by the chip, without at the same time significantly changing the housing dimensions and without increasing the risk of delamination much.

0007This object is achieved by a device having the features of claim 1.

0008Advantageous developments of the components of the invention are subject of the claims.

0009In the device according to the invention it is provided that the chip carrier part comprising three separate, thermally conductively to the chip carrier part connected external terminals, which protrude at different, said spaced apart locations of the cladding therefrom and which are shaped such that it in on one of the mounting of the component provided PCB mounted state of the device, all rest on the same terminal or PCB. The generated during operation of the device in the chip heat is consequently fed at three different points in the circuit board and a large area distributed on this. Thereby, a clearly improved heat dissipation from the optoelectronic chip is achieved.

0010In this embodiment of the device according to the invention the external terminals of the chip carrier part in plan view of the lead frame extend seen, proceeding from the chip carrier part separated from one another essentially in a star shape towards the outside. The heat dissipation points from the component to the PCB out thereby exhibit relatively large distances from each other, creating a very large-scale distribution of the derived from the chip during operation of the device via the chip carrier part and its external connections thermal energy is achieved in the circuit board.

0011Advantageously, the external terminals in the area in which they extend in a star shape to the outside, the longitudinal central axes of which each include two mutually adjacent at an angle of about 90 °. In this arrangement, the plastic area between terminals is maximum, whereby the risk of delamination z. B. is reduced in temperature.

0012Is a device provided with at least a first and a second optoelectronic chip and comprises the chip carrier part at least two external connectors that protrude at different said spaced apart locations of the sheath therefrom, so the device does not belong to the invention, but merely serves to their Explanation.

0013The lead frame here comprises at least two connecting parts, each with an external terminal, which also protrude from the casing side. Preference is also given here, the external terminals of the chip carrier part and the connecting parts in plan view of the lead frame are seen disposed in a star shape, in essence, whereby a maximum distance of the external terminals of the chip carrier part is ensured from each other. The operating of the device via the chip carrier part and its external connections from the chip derived thermal energy is thereby fed at relatively spaced points in the circuit board, so that a very good heat distribution on the circuit board is also achieved here.

0014In the latter device, the external terminals of the chip carrier part can be seen in plan view of the lead frame with respect to the chip carrier part to be diagonally offset from one another. then they protrude on opposite side surfaces of a preferably substantially parallelepipedic casing of this. The connection parts are in this case arranged on different sides of the chip carrier part and whose external terminals also project out on opposite side faces of the sheath therefrom. In plan view of the lead frame they are with respect to the chip carrier part to the external terminals of the chip carrier part opposite to each other arranged diagonally offset.

0015In order, if necessary, to further improve the heat dissipation from the chip, the chip carrier part can also have more than two external connections, which in turn protrude at different spaced locations from each other having the envelope therefrom. The number of external terminals can be increased depending on the permissible size of the device further as required.

0016serving for one of the explanation, no component of the invention that can be mounted on a circuit board, that during the operation thereof is radiated, the light emitted from the chip radiation substantially parallel to the printed circuit board (laterally emitting device) comprises the chip carrier part at least two external connections and the connecting part at least one external port on which each other protrude separated at one and the same side surface of the sheath of this. The external connection of the connection part is in this case preferably arranged between the two external terminals of the chip carrier portion.

0017In a particularly preferred development of the latter component of the external connection of the connection part is narrower than the two external terminals of the chip carrier part. Of course, optional in the other abovementioned inventive devices, the external terminals of the chip carrier part may be wider than the external terminals of the connector parts.

0018In a further development of the above-mentioned side-emitting component of the chip carrier part is additionally connected in a thermally conductive with at least one cooling fin that protrudes on another side surface of the enclosure as the terminal parts of these. This cooling vane alone or to this cooling vane thermally connected further cooling device ensures a further improved heat dissipation from the chip.

0019Further advantages and preferred embodiments will be apparent from the below in connection with the <figref idrefs="f0001 f0002">Figures 1 to 3b</figref> explained in more detail examples. Show it:<ul><li><figref idrefs="f0001">figure 1a</figref> a schematic representation of a plan view of an embodiment of a device according to the invention with a single opto-electronic chip,</li><li><figref idrefs="f0001">figure 1b</figref> a schematic representation of a section through the embodiment of <figref idrefs="f0001">figure 1</figref> taken along the line AA,</li><li><figref idrefs="f0002">figure 2</figref> a schematic representation of a plan view of an illustrative example of a device with at least two optoelectronic chips,</li><li><figref idrefs="f0002">3a</figref> a schematic representation of a side view of an illustrative example of a laterally-emitting component and</li><li><figref idrefs="f0002">3b</figref> a schematic representation of a section through the illustrative example of <figref idrefs="f0002">figure 3</figref> along in <figref idrefs="f0002">figure 3</figref> drawn line AA.</li></ul>

0020In the figures, identical and functionally identical components of the various examples are always provided with the same reference numerals.

0021In the device according <figref idrefs="f0001">figure 1</figref> If it is a light-emitting component, in which on a chip carrier part 2 of a lead frame (lead frame) 7, a light-emitting semiconductor chip 1 (LED chip) by means of a highly thermally conductive bonding agent, for. example, is fastened by means of a metallic solder. Three separate external terminals 4, 5, 6 extend from the chip carrier part 2 in three different directions to the outside. In a distance from the chip carrier part 2 to the external terminals 4, 5, 6, a connecting part 8 is arranged with an external terminal 9 which is connected by a bonding wire 16 to an electrical contact of the LED chip 1, z. B. with the Anodenkontaktierung , A second contact metallization (cathode contacting) of the LED chip 1 is, for example, at the chip carrier part 2 facing bottom and is electrically connected to the chip carrier part 2 by means of which in this case also electrically conductive connecting means. The chip carrier part 2 to the external terminals 4, 5, 6 serves, consequently, in this case both as a cathode terminal and as a thermal connection for heat dissipation from the LED chip.

0022The cathode contact is not arranged as in the above case, at the bottom of the chip 1, but, for. Example, at the top thereof, it can be electrically connected by a bonding wire with the chip carrier part 2.

0023The chip carrier portion 2, the connecting part 8 and portions of the external terminals 4, 5, 6, 9 are enclosed by a substantially cuboid base body 10 of a casing 3, which has a recess eleventh The recess 11 has substantially the shape of a truncated cone and extends from a plane parallel to the lead frame 7 major surface 17 of the base body 10 to the lead frame 7, wherein increasing the cross-section of the recess 11 from the lead frame 7 to the main surface 17 of the base 10 toward. The LED chip 1 is located in the recess 11, which is preferably provided with a radiation-transmissive window part 22 with a transparent plastic cast. This window member 22 forms together with the base body 10 has a casing 3 of the device. The external terminals 4, 5, 6, 9 protrude on opposite side surfaces 18,19 of the base 10 from this. They run within the main body 10 from the chip carrier part 2 initially substantially star-shaped apart and bend from the further course, so as to 18,19 penetrate the side faces perpendicular.

0024The chip carrier part 2 is preferably entirely within the bottom surface of the recess eleventh

0025The external terminals 4,5,6,9 have in the area in which they extend in a star shape outward longitudinal central axes 23,24,25, of which two mutually adjacent an angle of about 90 °.

0026The external terminals 4, 5, 6, 9 are outside of the main body 10 of the first to the first major surface 17 opposite the second major surface 20 of the body 10 back and bent in the course below the main body 10 toward the center thereof. They can also, as in<figref idrefs="f0001">figure 1b</figref> indicated by dashed lines, be bent to swing shaped connection stubs. This also constitutes a customary per se in the surface mount technology form the external electrical connections. These types of external terminals for surface-mount devices (SMD) are known per se and are not described in detail therefore at this point.

0027The external connections are therefore formed so that they all lie on the same terminal or circuit board mounted on a provided for the mounting of the component PCB state of the component.

0028The inner surfaces of the recess 11 form a reflector for the radiation emitted from the LED chip 1 in the operation of the component radiation. They are optionally coated with a reflection-enhancing material. Alternatively, the base body may consist of a reflection-enhancing material.

0029In the illustrative example of <figref idrefs="f0002">figure 2</figref> are in contrast to the embodiment of <figref idrefs="f0001">Figures 1a and 1b</figref> 7 two different colors luminous LED chips 1, 13 mounted on a chip carrier part 2 of a lead frame by means of a thermally and electrically conductive connecting means. On opposite sides of the chip carrier part 2 are arranged at a distance to this, a first 8 and a second connection portion 12, each of which has an external connection 9.14. These external connections 9,14 are parallel offset to each other, extend, seen from the chip carrier part 2, in mutually opposite directions and protrude on opposite side surfaces 18,19 of the base 10 from this. They are 1.13 electrically connected by bonding wires 16 to the anode contacts of the LED chips.

0030The chip carrier part 2 has two external terminals 4.5, starting from the chip carrier part 2 likewise substantially offset parallel to each other in opposite directions parallel to the external terminals 9,14 of the connecting parts 8,12 extending and opposing side surfaces 18,19 the main body 10 protrude therefrom.

0031As in the embodiment of <figref idrefs="f0001">Figures 1a and 1b</figref>, Has the radiopaque base body 10 on a frustoconical recess 11 which is provided with a transparent window portion 22nd The LED chips are 1.13 in this recess 11th

0032The external terminals 4,5,9,14 protrude on opposite side surfaces 18,19 of the base 10 from this. They are outside of the base 10 similar to the embodiment according to<figref idrefs="f0001">Figures 1a and 1b</figref> shaped.

0033In the examples described above, each of the casing 3 and the external terminals 4,5,6,9,14 are formed such that in operation of the device by the or by the LED chip / s emitted radiation substantially perpendicular to the mounting surface of a provided for the mounting of the component circuit board is radiated.

0034In the illustrative example, the <figref idrefs="f0002">Figure 3a and 3b</figref> If it is a so-called side-emitting LED device. This type of device is explained in the general part of the description. The casing 3 and the external terminals 4,5 and 9 of the chip carrier element 2 or the connecting member 8 are formed so that it can be mounted back on this with a side surface 20 of the body 10 to the mounting surface of a circuit board in this component.

0035For this purpose, a lead frame 7, a chip carrier part 2, which has at least two external connectors 4.5. These external terminals extend 4.5 initially, starting from the chip carrier part 2 on which an LED chip 1 is fixed by means of a thermally and electrically conductive connecting means, in essentially opposite directions outward. In the further course they bend from the same direction, so that they then parallel to each other in the same direction. Between the two external terminals 4,5 of the chip carrier part 2, a connecting part 8 is arranged with an external terminal 9 extending parallel to the two external terminals of the chip carrier part 4.5 in the same direction as this.

0036The chip carrier part 2, the external terminals 4.5, the connection part 8 and the external terminal 9 are enclosed in analogy to the two examples described above, with a radio-opaque base body 10 having a frustoconical recess 11 in which the LED chip 1 is disposed , The recess 11 is also here provided with a radiation-transmissive window part 22, which preferably consists of a radiation-transmissive plastic. The external terminals 4,5,9 stand out on one and the same side face 18 of the base 10 of this, are bent toward the rear of the base 10 outside the body 10 downward and to the further course along the back 21 of the base 10 the center thereof bent. The facing away from the side surface 18 of the base body 10 external surfaces of the external terminals 4,5,9 form a bearing surface of the component to its mounting on a circuit board.

0037For additional cooling of the LED chip 1, the chip carrier part 2 with a cooling fin 15 having (in the <figref idrefs="f0002">Figures 3a and 3b</figref> dashed lines). This extends on one of the side surface 18, protruding from the external terminals 4,5,9, opposite side face 19 of the base 10 out of this and is bent outside the body 10 to its rear face 21 toward, so that it on the side surface 19 rests. At this cooling vane 15 optional additional cooling devices can be thermally connected.

0038In all the examples described above, the external terminals of the chip carrier part 2 are wider than the external ports or connectors 8.12. This can be achieved from the LED chip 1 at substantially unchanged Housing dimensions a further improved heat dissipation. However, the external terminals 4,5,6,9,12 can also have all the same width.

0039In order to achieve a further improvement of the heat transported away from the LED chip, particularly large solder pads are provided on a provided for the mounting of the component board. These are also arranged in a star shape and can thus distribute the heat dissipated from the LED chip heat over a large area on the circuit board. The leadframe of the components of the invention result in the heat in a star shape from the LED chip to the outside of the enclosure. Thus, the heat is fed to far apart points in the board. On the board are preferably each solder pad large, made for example of copper metallization, to spread the heat on the circuit board. The heat resistance of the casing according to the invention is compared with the heat resistance of conventional LED package is significantly reduced.

0040In the above described housings for LED chips is known in the semiconductor art housing for optoelectronic devices. The special shapes, materials used for this purpose and manufacturing process are not described in greater detail therefore at this point.

0041The description of the invention notes the embodiment is of course not intended to limit the invention to this example.