Optoelectronic Semi-Conductor Element and Method for Operating an Optoelectronic Semi-Conductor Element

Abstract

In an embodiment a method for operating an optoelectronic semiconductor component includes providing the optoelectronic semiconductor component having an optoelectronic semiconductor chip and a casing comprising a matrix material, wherein the semiconductor chip is embedded into the casing, and wherein optically inactive particles have been introduced as crack nuclei into the matrix material of the casing, and operating the optoelectronic semiconductor component such that cavities form entirely within the casing for at least some of the crack nuclei.

Claims

1.-14. (canceled)

15. An optoelectronic semiconductor component comprising: an optoelectronic semiconductor chip; and a casing comprising a matrix material, wherein the semiconductor chip is embedded into the casing, wherein optically inactive particles are located as crack nuclei in the matrix material of the casing, and wherein the casing takes such a form that, in operation of the optoelectronic semiconductor component, cavities form entirely within the casing at least at some of the crack nuclei.

16. The optoelectronic semiconductor component of claim 15, wherein the casing takes such a form that aging-related shrinkage of the matrix material causes formation of the cavities.

17. The optoelectronic semiconductor component of claim 15, wherein the particles are transparent to a radiation generated or received by the optoelectronic semiconductor chip.

18. The optoelectronic semiconductor component of claim 15, wherein the particles comprises a material matched in terms of refractive index to a refractive index of the matrix material.

19. The optoelectronic semiconductor component of claim 18, wherein the refractive index of the material of the particles varies by not more than 10% from the refractive index of the matrix material.

20. The optoelectronic semiconductor component of claim 18, wherein the refractive index of the material of the particles varies by not more than 5% from the refractive index of the matrix material.

21. The optoelectronic semiconductor component of claim 15, wherein at least some of the particles have an angular basic form.

22. The optoelectronic semiconductor component of claim 15, wherein the particles have an average diameter between 5 μm and 30 μm, inclusive.

23. The optoelectronic semiconductor component of claim 15, wherein the particles are present in the casing with a proportion between 3% by weight and 30% by weight inclusive.

24. The optoelectronic semiconductor component of claim 15, wherein the particles are present in the casing with a proportion between 5% by weight and 25% by weight inclusive.

25. The optoelectronic semiconductor component of claim 15, wherein the matrix material is silicone.

26. The optoelectronic semiconductor component of claim 15, wherein the matrix material has a refractive index of between 1.4 and 1.6, inclusive.

27. A method for operating an optoelectronic semiconductor component, the method comprising: providing the optoelectronic semiconductor component comprising an optoelectronic semiconductor chip and a casing comprising a matrix material, wherein the semiconductor chip is embedded into the casing, and wherein optically inactive particles have been introduced as crack nuclei into the matrix material of the casing; and operating the optoelectronic semiconductor component such that cavities form entirely within the casing for at least some of the crack nuclei.

28. An optoelectronic semiconductor component comprising: an optoelectronic semiconductor chip; and a casing comprising a matrix material, wherein the semiconductor chip is embedded into the casing, wherein optically inactive particles are located as crack nuclei in the matrix material of the casing, and wherein the casing is configured to form cavities entirely within the casing for at least some of the crack nuclei.

29. The optoelectronic semiconductor component of claim 28, wherein the casing is configured to form the cavities based on aging-related shrinkage of the matrix material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further configurations and expediencies are apparent from the description of the working examples in conjunction with the figures that follows.

[0041] The figures show:

[0042] FIGS. 1A and 1B: a working example of a semiconductor component and a method of operation of a semiconductor component by diagrams in schematic section view immediately after production (FIG. 1A) and after a given duration of operation (FIG. 1B);

[0043] FIG. 2A: a scanning electron micrograph of a reference sample with delaminated reference casing;

[0044] FIG. 2B: a scanning electron micrograph of a section through an above-described semiconductor component with a casing having cavities;

[0045] FIGS. 3A and 3B: measurement results for measurements of normalized luminous flux LN in percent, normalized to the luminous flux at time t=0 (also as lumen maintenance/Φ.sub.□) in FIG. 3A and the change in color locus (also color shift) Δv′ in pts compared to time t=0 in FIG. 3B in above-described semiconductor components and in reference samples as a function of duration of operation t in hours; and

[0046] FIGS. 4A and 4B: simulation results of delamination warpage assuming a casing having six cavities (FIG. 4A) or 18 cavities (FIG. 4B).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0047] Elements that are the same, of the same type or have the same effect are given the same reference numerals in the figures.

[0048] The figures are each schematic diagrams and are therefore not necessarily true to scale. Instead, comparatively small elements and especially layer thicknesses may be shown in excessively large size for illustration.

[0049] The optoelectronic semiconductor component according to the working example shown in FIG. 1A has an optoelectronic semiconductor chip 2 in the form, for example, of an LED semiconductor chip. The optoelectronic semiconductor chip 2 is embedded in a casing 3.

[0050] In the working example shown, the semiconductor chip 2 is in a cavity of a housing body 6 and is externally electrically contactable via a leadframe 61. However, the described configuration of the casing 3 is fundamentally suitable for any kind of housings in which an optoelectronic semiconductor chip is embedded into a casing 3, especially one that is radiation-transparent.

[0051] The casing 3 is formed such that cavities 5 entirely within the casing 3 are formed in operation of the optoelectronic semiconductor component. This is shown in schematic form in FIG. 1B. The semiconductor component 1 is thus deliberately operated in such a way that the cavities 5 form within the casing 3, especially in the form of microcracks.

[0052] By means of the cavities 5, it is possible to achieve reduction of stresses that could lead to delamination of the casing 3 from the semiconductor chip 2 or parts of the housing body 6, for example of the leadframe 61.

[0053] This becomes clear from the scanning electron micrographs shown in FIGS. 2A and 2B. In the case of a conventional reference casing 39, aging-related shrinkage of the reference casing can have the effect that the reference casing 39 becomes detached in places from the semiconductor chip 2. This is apparent in FIG. 2A at sites indicated by the arrows 91.

[0054] By contrast, the cavities 5 in the casing 3 that are indicated by the arrows 95 in FIG. 2B show that the casing 3 remains firmly bonded to the semiconductor chip 2 and the housing body 6.

[0055] Gaps between the casing 3 and a semiconductor chip 2, for example on account of corrosion effects, could lead to a reduction in brightness of the radiation emitted by the optoelectronic semiconductor component 1. The optical coupling of the optoelectronic semiconductor chip 2 to the casing 3 can also be impaired by such a gap, which likewise leads to a reduction in brightness.

[0056] In addition, this can also result in a shift in color locus of the radiation emitted by the semiconductor component overall. This is shown in FIGS. 3A and 3B. The measurements demonstrate that the drop in brightness for semiconductor components with the above-described casing, shown by the curves 7, is much smaller than for the reference curves 8. The change in color locus, as shown in FIG. 3B, is also much greater for the reference curves 8.

[0057] FIGS. 4A and 4B show results of simulations of the delamination stress that occurs. The basis used for this purpose was a casing having a cross section of 150 μm×250 μm. In addition, aging-related shrinkage of 4.5% was estimated for the casing 3. For a conventional homogeneous casing, i.e. a reference casing without cavities, this results in a delamination stress of 0.154 MPa.

[0058] FIGS. 4A and 4B show simulations in which, rather than a homogeneous conventional shell, six cavities (FIG. 4A) or 18 cavities (FIG. 4B) were assumed, with the cavities each having a length of 20 μm. According to simulation results, a reduced delamination stress of 0.139 MPa is found in the case of six cavities, and an even more significantly reduced delamination stress of 0.109 MPa for the case with 18 cavities. The simulations thus demonstrate that the cavities have a positive effect on delamination stress and hence promote the aging stability of the semiconductor component 1 overall.

[0059] A suitable matrix material 31 for the casing 3 is, for example, one that includes a silicone or consists of a silicone. Especially suitable is a highly refractive silicone, for example having a refractive index between 1.54 and 1.56. In principle, however, it is also possible to employ another one of the matrix materials mentioned in the general part of the description.

[0060] It is possible to introduce particles 4 into the matrix material 31 of the casing that serve as crack nuclei and promote the formation of cavities in the casing. Suitable materials for the particles are in principle all of those that are transparent to the radiation to be generated or received by the optoelectronic semiconductor chip. The particles 4 are preferably formed by a material which, in terms of refractive index, differs only slightly, if at all, from the refractive index of the matrix material 31. The refractive indices preferably differ from one another by not more than 10%, more preferably by not more than 5%. For example, the particles contain an oxide, for instance silicon dioxide.

[0061] Examples that are alternatively suitable for the particles include an acrylate, for instance polymethylmethacrylate (PMMA), an imide, for example poly(methylmethacrylimide) (PMMI), or a glass.

[0062] The particles 4 preferably have an average diameter between 5 μm and 30 μm inclusive.

[0063] It has additionally been found that particles 4 having an angular basic form act particularly efficiently as crack nuclei for the formation of cavities 5 in the casing 3. In principle, however, it is also possible to employ spherical particles.

[0064] The particles 4 are preferably present in the casing 3 in a proportion of at least 3% by weight, preferably at least 5% by weight. This reliably ensures that, on account of the aging-related shrinkage of the matrix material, sufficient cavities 5 are formed in the casing 3.

[0065] Appropriately, the particles 4 are present in the casing in a proportion of not more than 30%, especially not more than 25% by weight. This ensures that the casing is not too viscous in the production of the semiconductor component 1.

[0066] In addition, a luminophore 35 may also be disposed within the casing 3, such that the semiconductor component 1 produces mixed radiation overall, for example mixed light that appears white to the human eye.

[0067] The described configuration of the casing 3 is especially suitable for optoelectronic semiconductor components 1 where high light outputs are required in the continuous wave sector, as a result of which comparatively high temperatures occur in the casing 3. As a result, in the case of such optoelectronic semiconductor components 1, there is an elevated risk of delamination effects on account of aging-related shrinkage of the matrix material. In the case of such optoelectronic semiconductor components 1, high aging stability of the semiconductor components can be achieved, especially with regard to brightness and color locus of the radiation emitted, without having to reduce the power consumption of the optoelectronic semiconductor component.

[0068] In principle, however, the casing described is suitable for all kinds of optoelectronic semiconductor components, especially also for optoelectronic semiconductor chips 2 intended to receive radiation.

[0069] The invention is not limited by the description with regard to the working examples. Instead, the invention encompasses any new feature and any combination of features, which especially include any combination of features in the patent claims, even if this feature or this combination itself is not exclusively specified in the patent claims or working examples.