OPTOELECTRONIC SEMICONDUCTOR DEVICE AND METHOD FOR PRODUCING AN OPTOELECTRONIC SEMICONDUCTOR DEVICE

Abstract

An optoelectronic semiconductor device includes a substrate with a first main side and a second main side. A plurality of light-emitting semiconductor chips is distributed over the first main side and over the second main side. A molding compound encloses the light-emitting semiconductor chips in a lateral direction. The molding compound levels with the light-emitting semiconductor chips in a direction away from the substrate. The molding compound has a top side facing away from the substrate. A plurality of planar electrical interconnects run on the top side and electrically connects the light-emitting semiconductor chips on their radiation exit sides facing away from the substrate.

Claims

1. An optoelectronic semiconductor device comprising a substrate with a first main side and a second main side, a plurality of light-emitting semiconductor chips which are distributed over the first main side and over the second main side, at least one molding compound that encloses the light-emitting semiconductor chips in a lateral direction and that levels with the light-emitting semiconductor chips in a direction away from the substrate, the at least one molding compound has at least one top side facing away from the substrate, and a plurality of planar electrical interconnects that run at least partly on the at least one top side and that electrically connect the light-emitting semiconductor chips on their radiation exit sides facing away from the substrate.

2. The optoelectronic semiconductor device according to claim 1, which is fashioned as a filament so that a length of the optoelectronic semiconductor device exceeds a width thereof by at least a factor of five, wherein electrical terminal connection surfaces to externally contact the optoelectronic semiconductor device are located solely at one end or at two opposing ends of the substrate.

3. The optoelectronic semiconductor device according to claim 2, wherein at least one of the electrical terminal connection surfaces is arranged on the first main side and at least one of the electrical terminal connection surfaces is arranged on the second main side.

4. The optoelectronic semiconductor device according claim 1, wherein the substrate comprises electrical connection areas on the first main side and on the second main side and comprises internal electrical conductor tracks that run to the connection areas, wherein the light-emitting semiconductor chips are mounted on the connection areas.

5. The optoelectronic semiconductor device according to claim 4, further comprising electrical through connections that run through the at least one molding compound, wherein the electrical through connections are placed on the connection areas and electrically connect the connection areas with the corresponding planar electrical interconnects.

6. The optoelectronic semiconductor device according to claim 5, wherein the electrical through connections are formed by via chips or by metallizations.

7. The optoelectronic semiconductor device according to claim 1, wherein at least some of the light-emitting semiconductor chips are electrically connected in parallel.

8. The optoelectronic semiconductor device according to claim 7, wherein all light-emitting semiconductor chips on the first main side are electrically connected in a first electrical parallel connection and all light-emitting semiconductor chips on the second main side are electrically connected in a second electrical parallel connection, wherein the first and the second parallel connection can be electrically connected independently of one another.

9. The optoelectronic semiconductor device according to claim 1, comprising two molding compounds, each molding compound is limited to one of the main sides of the substrate, wherein each molding compound encloses all of the light-emitting semiconductor chips on the respective main side of the substrate.

10. The optoelectronic semiconductor device according to claim 1, comprising exactly one molding compound which continuously extends to the first and to the second main side of the substrate, all of the light-emitting semiconductor chips are enclosed in the molding compound.

11. The optoelectronic semiconductor device according to claim 1, further comprising at least one potting compound which covers the light-emitting semiconductor chips and the at least one molding compound.

12. The optoelectronic semiconductor device according to claim 11, wherein the at least one potting compound comprises at least one phosphor, wherein the light-emitting semiconductor chips together with the phosphor are configured to produce white light.

13. The optoelectronic semiconductor device according to claim 1, wherein the substrate has a thermal conductivity of at least 25 W/(m.Math.K), wherein a mean thickness of the substrate is between 0.2 mm and 2 mm inclusive.

14. The optoelectronic semiconductor device according to claim 1, which is mechanically flexible so that the optoelectronic semiconductor device can reversibly be bent with a radius of curvature of 2 cm or less.

15. A method for producing an optoelectronic semiconductor device according to claim 1, comprising the following steps in the stated order: providing the substrate, attaching the respective light-emitting semiconductor chips at the first main side, attaching the respective light-emitting semiconductor chips at the second main side, molding the molding compound, and applying the planar electrical interconnects.

16. The method according to claim 15, wherein the molding compound (4) is formed by foil-assisted molding, wherein between the steps of attaching the respective light-emitting semiconductor chips to the first main side and to the second main side, in a snap curing step the light-emitting semiconductor chips at the first main side are preliminarily connected to the first main side.

17. An optoelectronic semiconductor device comprising a substrate with a first main side and a second main side, a plurality of light-emitting semiconductor chips which are distributed over the first main side and over the second main side, at least one molding compound that encloses the light-emitting semiconductor chips in a lateral direction and that levels with the light-emitting semiconductor chips in a direction away from the substrate, the at least one molding compound has at least one top side facing away from the substrate, and a plurality of planar electrical interconnects that run at least partly on the at least one top side and that electrically connect the light-emitting semiconductor chips on their radiation exit sides facing away from the substrate, wherein the substrate comprises electrical connection areas on the first main side and on the second main side and comprises internal electrical conductor tracks that run to the connection areas, the light-emitting semiconductor chips are mounted on the connection areas, and the internal electrical conductor tracks are not accessible from an exterior of the semiconductor device so that the light-emitting semiconductor chips on one of the main sides can be supplied with current independently of the light-emitting semiconductor chips on the other main side.

Description

[0045] An optoelectronic semiconductor device and a method described herein are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the figures are indicated by the same reference signs. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.

[0046] In the figures:

[0047] FIGS. 1 to 2 show sectional representations along a longitudinal direction of exemplary embodiments of optoelectronic semiconductor devices described here;

[0048] FIGS. 3 to 5 show top views of exemplary embodiments of optoelectronic semiconductor devices described here;

[0049] FIG. 6 shows a sectional representation of an exemplary embodiment of an optoelectronic semiconductor device described here, and

[0050] FIGS. 7 to 10 show sectional representations in a cross direction of exemplary embodiments of optoelectronic semiconductor devices described here.

[0051] FIG. 1 shows an exemplary embodiment of an optoelectronic semiconductor device 1. The semiconductor device 1 comprises a substrate 2. The substrate 2 has a first main side 21 and a second main side 22. Within the substrate 2, there are first internal electrical conductor tracks 23a and second internal electrical conductor tracks 23b. Both conductor tracks 23a, 23b run towards electrical contact areas 24 and also to electrical terminal connections surfaces 6a, 6b. The terminal connection surfaces 6a, 6b are to externally electrically contact the optoelectronic semiconductor device 1, for example by soldering or clamping.

[0052] In particular, there are two terminal connection surfaces 6a for an anode contact, one on each one of the main sides 21, 22. The same is true for the terminal connection surfaces 6b which can be fashioned as cathode contacts. As an option, the respective terminal connection surfaces 6a, 6b of the same type and located on the first main side 21 and on the second main side 22 can be electrically connected directly to one another by means of the internal conductor tracks 23a, 23b. Thus, the respective terminal connection surfaces 6a, 6b of the same type can be electrically short-circuited.

[0053] Moreover, the optoelectronic semiconductor device 1 comprises a plurality of light-emitting semiconductor chips 3. Preferably, the light-emitting semiconductor chips 3 are LED chips. For example, the light-emitting semiconductor chips 3 are blue-emitting LED chips. Otherwise, there can be different kinds of light-emitting semiconductor chips 3 that produce, for example, red light as well as green light and blue light and, as an option, also yellow light. The light-emitting semiconductor chips 3 are mounted on the electrical connection areas 24.

[0054] Further, there is a molding compound 4. The molding compound 4 laterally encloses the light-emitting diode chips 3 all around. In a direction away from the substrate 2, the molding compound 4 terminates flush with the light-emitting semiconductor chips 3. Thus, a top side 40 of the molding compound 4 can lie in the same plane as radiation exit sides 30 of the light-emitting diode chips 3. The light exit sides 30 are remote from the substrate 2.

[0055] For example, the molding compound 4 is of a reflective, white material. In particular, the molding compound 4 is made of a silicone that is filled with reflective particles which can be made of titanium dioxide, for example. Otherwise, the molding compound 4 can also be of an absorbing material like a resin filled with carbon black. However, preferably the molding compound 4 is highly reflective to the light generated in the light-emitting semiconductor chips 3 during operation of the semiconductor device 1.

[0056] Moreover, there is a plurality of electrical through connections 7. The through connections 7 run through the molding compound 4 and end at the substrate 2 at the connection areas 24. The through connections 7 are made of dummy chips or of metallizations, for example. Preferably, a height of the through connections 7 is equal or similar to the height of the light-emitting semiconductor chips 3.

[0057] An electrical connection to the light exit sides 30 of the light-emitting semiconductor chips 3 is made by means of planar electrical interconnects 5. The planar interconnects 5 run from the respective through connections 7 to the assigned light-emitting semiconductor chip 3. There can be a one-to-one assignment between the connections 7, the interconnects 5 and the respective semiconductor chips 3. Preferably, the through connections 7 are made of one or a plurality of metallic layers.

[0058] As the light-emitting semiconductor chips 3 are located on both main sides 21, 22, the semiconductor device 1 can efficiently emit light on both main sides 21, 22. The substrate 2 is by far longer than broad so that the semiconductor device 1 can be an LED filament. The overall semiconductor device 1 might be of mechanical flexible fashion because of the possibly flexible substrate 2 and the molding compound 4.

[0059] Other than shown in FIG. 1 it is also possible that there is a single electrical through connection for a plurality of light-emitting semiconductor chips 3. From such a through connection, the planar interconnects may run in a star-like fashion, for example. As an option, the optoelectronic semiconductor device 1 can also comprise further semiconductor chips like protection devices against damage because of electrostatic discharge, called ESD. Moreover, there can be memory devices or integrated circuits to address the light-emitting diode chips 3. Such optional further components are not shown in the exemplary embodiments to simplify the drawings.

[0060] According to FIG. 1, there are just three light-emitting semiconductor chips 3 on each main side 21, 22 of the substrate 2. Preferably, there is a much larger number of semiconductor chips on the respective main side 21, 22, for example at least 10 or at least 20 or at least 30 and/or at most 120 or at most 80 of the light-emitting semiconductor chips 3. This applies for all other exemplary embodiments, too.

[0061] As an option, there is a potting compound 8. The potting compound 8 can be of a transparent or also of a light-diffusing material. In particular, the potting compound 8 is of a silicone that could comprise particles to adjust the optical and/or mechanical properties thereof. The potting compound 8 can completely encase the light-emitting semiconductor chips 3, the molding compound 4 and the through connections 7. Further, the planar interconnects 5 can completely be covered by the optional potting compound 8.

[0062] The exemplary embodiment of FIG. 2 essentially corresponds to the exemplary embodiment of FIG. 1. However, the potting compound 8 comprises a phosphor 81. For example, the phosphor 81 comprises YAG:Ce to produce yellow light from blue light. Hence, the semiconductor device 1 can emit white light, composed of blue light from the light-emitting semiconductor chips 3 and of yellow light from the phosphor 81.

[0063] As a further option, the conductor tracks 23a, 23b of the same type at the two main sides 21, 22 can be electrically separated from one another. Thus, it might be possible to supply the light-emitting semiconductor chips 3 on one of the main sides 21, 22 independently of the light-emitting semiconductor chips 3 on the other main side 22, 21. To achieve this, it might be sufficient to have the conductor tracks 23a not directly connected to each other, but there could be an electrical short between the electrical termination connection surfaces 6b on the cathode side, for example.

[0064] According to the top view shown in FIG. 3, the light-emitting semiconductor chips 3 could be arranged along a straight line. However, an arrangement of the light-emitting semiconductor chips 3 in more than one line could also be realized, compare FIG. 4.

[0065] Moreover, in FIG. 4 it is illustrated that the terminal connection surfaces 6 could be located at just one end of the substrate 2. However, preferably the terminal connection surfaces 6 are located on both ends of the substrate as illustrated in FIG. 3.

[0066] According to the exemplary embodiment as shown in FIG. 5, the terminal connection surfaces 6 may not be centrally located at the ends of the substrate 2 but could be located in corner regions. Moreover, it is possible that the light-emitting semiconductor chips are electrically connected in a zigzag-like manner.

[0067] As a further option, in FIG. 5 it is illustrated that there can be first light-emitting semiconductor chips 3a and second light-emitting semiconductor chips 3b. For example, by means of the first light-emitting semiconductor chips 3a, blue light is produced. By means of the second light-emitting semiconductor chips, for example red light can be produced. By such an arrangement, an increased color rendering index can be achieved when a phosphor to produce yellow light is used. For example, there are fewer second light-emitting semiconductor chips 3b than first light-emitting semiconductor chips 3a.

[0068] In FIGS. 1 and 2, the light-emitting semiconductor chips 3 are electrically connected in parallel. Contrary to that, the light-emitting semiconductor chips 3 are electrically connected in series according to the exemplary embodiment of FIG. 6. Thus, the light-emitting semiconductor chips 3 are located on the electrical connection areas 24 which might be expanded. The through connections 7 could also be located on the connection areas 24 for the light-emitting semiconductor chips 3. Thus, the electrical contact of the radiation exit side 30 of a preceding light-emitting semiconductor chip 3 is connected by means of the planar electrical interconnect 5 and by means of the assigned electrical through connection 7 to the following electrical connection area 24 for the next light-emitting semiconductor chip 3 along the series connection.

[0069] Contrary to what is shown in FIG. 6, there could be just one series connection that extends from the first main side 21 to the second main side 22. This can be realized, for example, by an electrical through connection through the substrate 2, not shown.

[0070] As is possible in all other exemplary embodiments, the electrical contacts of the light-emitting semiconductor chips 3 need not be on different main sides of the light-emitting semiconductor chips 3. In particular, both electrical contacts could be located at the light exit side 30 facing away from the substrate 2. Thus, there could be two planar interconnects 5 for each one of the light-emitting semiconductor chips 3 in this case.

[0071] In FIGS. 7 to 10, further cross-sectional views are illustrated. The cross-sections in FIGS. 1, 2 and 6 are along a longitudinal direction, the cross-sections in FIGS. 7 to 10 are along a cross direction, that is along a plane perpendicular to the projection planes of FIGS. 1, 2 and 6.

[0072] FIG. 7 shows that there are two molding compounds 4 which are limited in each case to the respective main side 21, 22. The optional potting compound 8 can completely encase the other components of the semiconductor device 1, when seen in cross-section. Thus, in cross-section the semiconductor device 1 can be approximately of rectangular or square shape.

[0073] In FIG. 8 it is illustrated that there is only one molding compound 4 that extends in one piece over the first and the second main sides 21, 22 of the substrate 2. There could be two potting compounds 8 that might include the phosphor 81. Each of the potting compounds 8 is located over the respective main side 21, 22 of the substrate 2. The potting compound 8 could have a constant or a nearly constant layer thickness.

[0074] According to FIG. 7, the planar interconnect 5 is located centrally at the light-emitting semiconductor chips 3. This is not necessary as shown in FIG. 8 wherein the planar interconnects 5 could be located at an edge of the semiconductor chips 3, that is, seen in top view onto the main sides 21, 22, in a corner region of the light-emitting semiconductor chips 3.

[0075] In FIG. 9 it is illustrated that the light-emitting semiconductor chips 3 might be mounted on the substrate 2 eccentrically. However, the light-emitting semiconductor chips 3 can be mounted point symmetrically when seen in the cross-section of FIG. 9.

[0076] As an option, the potting compound 8 could be limited, or essentially limited, to the light exit sides 30 of the light-emitting semiconductor chips 3. The potting compound 8 might thus have a lens-like shape. Other than shown in FIG. 9, the potting compounds 8 can also have a constant or nearly constant layer thickness.

[0077] In FIG. 10 it is illustrated that both the molding compound 4 as well as the potting compound 8 can be of one piece. The planar interconnects 5 can be located eccentrically on the light-emitting semiconductor chips 3 in a mirror symmetric manner with respect to the substrate 2, contrary to what is illustrated in FIG. 8.

[0078] To produce the dual-sided LED emitter filaments 1 as illustrated in connection with FIGS. 1 to 10, the following method steps may be used:

[0079] a) die attach to attach the LED chips 3 and the via chips 7 to the substrate 2 with circuitry on one side,

[0080] b) snap cure to ensure that the chips 3, 7 are attached to the substrate 2,

[0081] c) flip over to attach the LED chips and via chips 3, 7 on the other side of the substrate 2 with circuitry,

[0082] d) die attach curing,

[0083] e) molding the molding compound 4 to create a surface for the planar interconnects 5,

[0084] f) lithography,

[0085] g) dielectric layer build-up, for example including resist deposition and resist exposure,

[0086] h) metallization build-up to form the planar interconnects 5,

[0087] i) apply solder resist, and

[0088] j) apply the potting compound which could be of clear fashion or could contain the at least one phosphor.

[0089] The components shown in the figures follow, unless indicated otherwise, preferably in the specified sequence directly one on top of the other. Layers which are not in contact in the figures are preferably spaced apart from one another. If lines are drawn parallel to one another, the corresponding surfaces are preferably oriented parallel to one another. Likewise, unless indicated otherwise, the positions of the drawn components relative to one another are correctly reproduced in the figures.

[0090] The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

LIST OF REFERENCE SIGNS

[0091] 1 optoelectronic semiconductor device [0092] 2 substrate [0093] 21 first main side of the substrate [0094] 22 second main side of the substrate [0095] 23 internal electrical conductor track [0096] 24 electrical connection area [0097] 3 light-emitting semiconductor chip [0098] 30 light exit side [0099] 4 molding compound [0100] 40 top side of the molding compound [0101] 5 planar electrical interconnect [0102] 6 electrical terminal connection surface [0103] 7 electrical through connection [0104] 8 potting compound [0105] 81 phosphor