Optoelectronic component and method for producing an optoelectronic component

Abstract

An optoelectronic component and a method for producing an optoelectronic component are disclosed. In an embodiment an optoelectronic component includes an optical element including silicone as a polymer material, the silicone having repeating units of cyclic siloxane and of linear siloxane which are arranged in alternation, wherein the optoelectronic component is configured to emit radiation.

Claims

1. An optoelectronic component comprising: an optical element comprising silicone as a polymer material, wherein the silicone has repeating units of cyclic siloxane and of linear siloxane which are arranged in alternation, wherein the silicone has the following structural formula: ##STR00009## wherein R.sub.1 to R.sub.18 are independently selected from the group consisting of H, alkyl, alkylene, alkylarylene, cycloalkyl and aryl, n is selected between 1 and 1000 inclusive, m is selected between 1 and 3 inclusive, and r is selected between 1 and 100 inclusive, and wherein the optoelectronic component is configured to emit radiation.

2. The optoelectronic component according to claim 1, wherein R.sub.1 comprises a vinyl group and R.sub.18 is H.

3. The optoelectronic component according to claim 1, wherein m is equal to 2.

4. The optoelectronic component according to claim 1, wherein m=2, R.sub.1 is a vinyl-containing radical and R.sub.12 to R.sub.14 are each H.

5. The optoelectronic component according to claim 1, wherein the cyclic siloxane and the linear siloxane are linked by hydrosilylation.

6. The optoelectronic component according to claim 1, wherein the cyclic siloxane and the linear siloxane are mixed in a ratio of 1:1 to 1:10.

7. The optoelectronic component according to claim 1, wherein the optical element is formed as a potting surrounding a semiconductor chip.

8. The optoelectronic component according to claim 1, further comprising converter materials embedded in the optical element.

9. The optoelectronic component according to claim 1, wherein the optical element is formed as a lens or a reflector.

10. A method for producing an optoelectronic component, the method comprising: forming an optical element by: providing a first material comprising a cyclic siloxane; providing a second material comprising a linear siloxane, wherein one of the two siloxanes is a silane and the other one has at least one double bond; adding a catalyst; and crosslinking the cyclic siloxane and the linear siloxane by hydrosilylation thereby producing silicone as a polymer material wherein the silicone has the following structural formula: ##STR00010## wherein R.sub.1 to R.sub.18 are independently selected from the group consisting of H, alkyl, alkylene, alkylarylene, cycloalkyl and aryl, n is selected between 1 and 1000 inclusive, m is selected between 1 and 3 inclusive, and r is selected between 1 and 100 inclusive.

11. The method according to claim 10, wherein crosslinking comprises crosslinking at 100 C. to 150 C.

12. The method according to claim 10, wherein the catalyst is a platinum catalyst.

13. An optoelectronic component: an optical element comprising silicone as a polymer material, the silicone having repeating units of cyclic siloxane and of linear siloxane which are arranged in alternation, wherein the linear siloxane has the following structural unit: ##STR00011## wherein R.sub.2 to R.sub.7 are independently selected from the group consisting of H, alkyl, alkylene, alkylarylene, cycloalkyl and aryl, and n is selected between 1 and 1000 inclusive, wherein the cyclic siloxane has the following structural unit: ##STR00012## wherein R.sub.12 to R.sub.15 are independently selected from the group consisting of H, alkyl, alkylene, alkylarylene, cycloalkyl and aryl, and m is selected between 1 and 3 inclusive, wherein the optical element is formed as a potting surrounding a semiconductor chip, and/or wherein the optical element is formed as a lens or a reflector, and wherein the optoelectronic component is configured to emit radiation.

14. The optoelectronic component according to claim 13, wherein m is equal to 2.

15. The optoelectronic component according to claim 13, wherein m=2, R.sub.1 is a vinyl-containing radical and R.sub.12 to R.sub.14 are each H.

16. The optoelectronic component according to claim 13, wherein the cyclic siloxane and the linear siloxane are mixed in a ratio of 1:1 to 1:10.

17. The optoelectronic component according to claim 13, wherein the optical element is formed as a lens or a reflector.

18. The optoelectronic component according to claim 13, further comprising converter materials embedded in the optical element.

19. The optoelectronic component according to claim 13, wherein the silicone has the following structural formula: ##STR00013## wherein R.sub.2 to R.sub.17 are independently selected from the group consisting of H, alkyl, alkylene, alkylarylene, cycloalkyl, siloxane and aryl, and wherein n is selected between 1 and 1000 inclusive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, advantageous embodiments and further developments result from the exemplary embodiments described in the following in connection with the figures.

(2) FIG. 1A shows a hydrosilylation reaction;

(3) FIG. 1B shows a backbiting mechanism;

(4) FIG. 1C shows the structural formulae of two cyclic siloxanes;

(5) FIG. 1D shows the hydrosilylation of cyclic and linear siloxanes;

(6) FIG. 1E shows thermogravimetric curves according to an exemplary embodiment and comparison examples; and

(7) FIGS. 2 to 5 show schematic side views of an optoelectronic component according to an embodiment.

(8) In the exemplary embodiments and figures, identical, similar or equivalent elements can each be provided with the same reference signs. The elements shown and their proportions are not to be regarded as true to scale. Rather, individual elements, such as layers, components, devices and areas, can be displayed in an exaggeratedly large format for better representability and/or better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(9) FIG. 1A shows the reaction of a silane with a vinyl-containing siloxane using a platinum catalyst. In other words, a silane is bound to a double bond under a syn-selective anti-Markovnikov addition. This binding can also be referred to as hydrosilylation. Such a reaction is described, for example, in HydrosilylationA Comprehensive Review on Recent Advances, B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009, doi:10.1007/978-1-4020-8172-9.

(10) FIG. 1B shows the schematic representation of the so-called backbiting mechanism. In the backbiting mechanism, linear siloxane units can be degraded via an intramolecular mechanism. Cyclic siloxanes and residues of linear siloxane units are formed. Backbiting is described, for example, in Brook, M. A., Silicon in Organic, Organometallic and Polymer Chemistry, Wiley, New York, 2000, ISBN: 978-0-471-19658-7.

(11) FIG. 1C shows the molecular structure of D.sub.4.sup.Vi (left) and D.sub.4.sup.H (right). These cyclic siloxanes have four SiO units. It is therefore an eight-ring siloxane. Crosslinking these two cyclic siloxanes produces a silicone that has a strong crosslinking and is therefore very hard, brittle and glassy. It is therefore not very suitable for use as a potting compound for optoelectronic components.

(12) FIG. 1D shows the reaction of the cyclic siloxane with the linear siloxane to form the silicone as a polymer material for the optical element 50 according to an embodiment. In general, it is possible in this context both to incorporate the D.sub.4 molecules as additives in commercial products and to combine them with other linear or branched siloxanes. This makes it possible to provide a silicone with high thermal stability and flexibility at the same time. Effects of the addition of cyclic systems on the thermal properties of silicones could be shown by thermogravimetric measurements (FIG. 1E). The relative weight w in percent was plotted as a function of the temperature T in C. The weight of the silicones was measured by means of thermogravimetric measurements (FIG. 1E). As material the commercially available Shin-Etsu LPS 3541 was heated under oxygen atmosphere at 20 K/min heating rate. Shown are two samples of the original system (1-1 and 1-2) as well as 5% by weight addition of D.sub.4.sup.Vi (1-3) and 10% by weight addition of D.sub.4.sup.H (1-4).

(13) It can be stated that there are optimal conditions, so that the thermal stability initially increases and decreases again with a too high proportion of cyclic systems or even no further curing can be observed. This is probably due to the fact that the mobility of the already cross-linked chains decreases and therefore not all reactive groups find a reaction partner. However, both free vinyl and hydride groups are potential weak points of polymers and should therefore be avoided by complete crosslinking.

(14) According to the manufacturer, the material Shin-Etsu LPS 3541 is used as follows: The silicone is formed from two components, namely vinyl component A and hydride component B, which are mixed in a weight ratio of 1:1, corresponding to LPS-3541A resin and LPS-3541B hardener. These two components are thoroughly mixed, for example, by mechanical stirring, and then degassed under reduced pressure for about 30 minutes. The mixture can now be poured into a desired mold and is then cured for 4 hours at 150 C.

(15) For example, the Shin-Etsu LPS 3541 systems shown in FIG. 1E are mixed by the manufacturer in a 1:1 weight ratio. For an addition of 10% by weight D.sub.4.sup.H, 1 g SiH components, e.g., linear siloxanes with 0.1 g D.sub.4.sup.H as cyclic siloxane, can be mixed and then 1.1 g Si-vinyl components can be added as a second linear siloxane. The components are stirred and subjected to the temperature program specified for the respective system, wherein, in particular, if the D.sub.4 content is high, care must eventually be taken to ensure slow heating, otherwise bubbles may easily form.

(16) In another example, Shin-Etsu LPS 3541 is crosslinked with cyclic siloxanes as follows: The desired siloxane, D.sub.4.sup.Vi or D.sub.4.sup.H, is added in the appropriate quantity, for example, 200 mg per 2 g total mass of pure silicone LPS 3541, i.e., 1 g component A and 1 g component B. In order to compensate for the additional reactive groups, the same mass is also added to the complementary component, i.e., A if D.sub.4.sup.H is used and B if D.sub.4.sup.Vi is used. This results in a total mixture of 1 g component A, 200 mg D.sub.4.sup.Vi and 1.2 g component B, for example.

(17) The rest of the procedure preferably follows the same procedure as for Shin-Etsu LPS 3541, whereby the volatility of the cyclic siloxanes is advantageously taken into account during degassing, i.e., the final pressure should be selected accordingly high, and a slower heating rate should be selected during heating, especially with large additive quantities, in order to avoid foaming. A similar procedure is preferred for the use of cyclic siloxanes in other commercial products.

(18) For the crosslinking of cyclic siloxanes with other linear or branched siloxanes, the following must be observed in particular: The use of commercial products as in the above example has the disadvantage that the exact parameters of the products such as chain length, degree of branching, additives for adjusting viscosity or adhesion, for example, are often not precisely known. In contrast, when using individually available siloxanes, it is easier to estimate the number of reactive groups, for example, and to coordinate them. For this purpose, it is advisable to optimize based on the stoichiometric ratio. The amount of platinum catalyst to be added should also be optimized for the desired application of the product in order to achieve complete curing on the one hand and to avoid the formation of platinum colloids or discolorations, which can occur with excessive amounts, on the other.

(19) FIG. 2 shows a schematic side view of an optoelectronic component according to one embodiment. Here, for example, an LED is shown. The component 100 comprises a housing 20 in combination with a carrier substrate 15. The housing can comprise a ceramic or a heat- or radiation-resistant plastic. A semiconductor chip 10 is arranged in a recess 25 of the housing 20, which emits radiation during operation of the component 100. The side walls of the recess 25 are sloped here and can include a reflective material. The semiconductor chip 10 can be energized via electrically conductive terminals 30, 31 and a bonding wire 32.

(20) The component 100 has an optical element 50. The optical element comprises a polymer material. The polymer material is a silicone. The silicone has repeating units of a cyclic siloxane and a linear siloxane which are arranged in alternation. The optical element 50 here is transparent to the radiation emitted by the semiconductor chip 10 and can be shaped as a lens (not shown here). In the example in FIG. 2, the optical element 50 can also be shaped as a potting 51, which surrounds the semiconductor chip 10. The optical element 50 can have particles 60, for example, converter materials or inorganic fillers homogeneously distributed in the optical element 50. Alternatively or additionally, the component 100 can include a conversion element 61, which can be arranged in the form of a platelet on the semiconductor chip 10 (not shown here). In addition, other inorganic fillers such as diffusers or thermally conductive particles such as silicon dioxide particles can be embedded in the optical element 50. The inorganic fillers, for example, can make up 10 to 80% by weight of the optical element 50. Component 100 can emit visible light with any color impression, especially white light.

(21) The optical element 50 has a high thermal stability as well as a high flexibility, so that crack formation in the optical element 50 during operation of the component 100 is avoided.

(22) FIG. 3 shows a schematic side view of an optoelectronic component 100 according to one embodiment. The device essentially corresponds to the device 100 of FIG. 2. Instead of converter materials comprising particles 60, here a conversion element 61 is arranged on the semiconductor chip 10. The optical element 50 is formed here as lens 70, which can project beyond the housing 20.

(23) FIG. 4 shows a schematic side view of an optoelectronic component 100 according to an embodiment. As an optical element 50, it comprises a lens 70 which is arranged on the component 100, for example, by means of an adhesive. The optical element 50 comprises a silicon according to at least one embodiment according to the application. Such a lens 70 can be, for example, cast and hardened separately in mold. In this example, the semiconductor chip 10 is encased in a potting 51 that fills the recess 25. The potting 51 can also be an optical element 50 according to an embodiment of the application or consist of conventional materials. Component 100 can include converter materials 60, for example, in the form of particles or a platelet (not shown here).

(24) FIG. 5 shows a schematic side view of an optoelectronic component 100 according to one embodiment. The optical element 50 here is designed as a reflector 52 and can comprise a reflective filler. The reflective filler can make up 10 to 80% by weight, in particular 20 to 60% by weight, of the optical element 50 and can be selected, for example, from titanium dioxide, zirconium dioxide, aluminum oxide and combinations thereof. The optical element 50 can line at least a part of the recess 25 and thus reflect the generated radiation, thereby increasing the radiation yield of the component 100. Alternatively, the optical element 50 can also form part of the housing 20. The housing 20 can also be made entirely of the polymer material of the optical element 50 and then has a reflective filler at least in the area of the recess.

(25) In this example, the semiconductor chip 10 is encapsulated with a potting 51, whereby the potting 51 can in turn be an optical element 50 according to at least one embodiment of the application.

(26) The exemplary embodiments described in connection with the figures and their characteristics can also be combined with each other according to further exemplary embodiments, even if such combinations are not explicitly shown in the figures. Furthermore, the exemplary embodiments described in connection with the figures may have additional or alternative features as described in the general part.

(27) The invention is not limited by the description of the exemplary embodiments to these. Rather, the invention includes each new feature as well as the combination of features, which in particular includes each combination of features in the patent claims, even if that feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.