Method for producing a luminescence conversion substance layer, composition therefor and component comprising such a luminescence conversion substance layer

Abstract

Method for producing a luminescence conversion substance layer (20) on a substrate (1) with a semiconductor element (10) emitting primary radiation during operation, comprising the method steps: (a) providing the substrate (1); (b) providing a composition (21) comprising a luminescence conversion substance (25), a matrix material and a solvent; (c) applying the composition (21) to the substrate (1), wherein the composition (21) has a viscosity of < 1 Pa*s upon application; (d) removing at least a portion of the solvent so that the luminescence conversion substance layer (20) is formed on the substrate (1), in which the concentration of the luminescence conversion substance (25) in a matrix comprising the matrix material has a gradient.

Description

[0001] The following publications describe a method for producing a luminescence conversion layer: US 2004 / 0104391 A1, US 2007 / 0001568 A1, US 2010 / 0006880 A1.

[0002] The invention relates to a method for producing a luminescence conversion substance layer, a composition used in the method, and a component comprising such a luminescence conversion substance layer.

[0003] In radiation-emitting devices, luminescence conversion substances are often used to partially convert the radiation emitted by a radiation source into radiation with a modified wavelength. In a radiation-emitting device, a uniform color impression of the emitted radiation and high efficiency are generally desirable, which is why the incorporation of the luminescence conversion substance into the device is particularly important.

[0004] An object to be achieved by the invention is therefore to provide a method for producing a luminescence conversion substance layer with improved properties.

[0005] Further objects are to provide a composition used in such a method and a component comprising such a luminescence conversion substance layer with improved properties.

[0006] At least one of these objects is achieved by the method, the composition and the component according to at least one embodiment of the invention.

[0007] A method for producing a luminescence conversion substance layer on a substrate with a semiconductor element emitting primary radiation during operation is specified, which method comprises the following steps: (a) providing the substrate; (b) providing a composition comprising a luminescence conversion substance, a matrix material and a solvent; (c) applying the composition to the substrate; (d) removing at least a portion of the solvent so that the luminescence conversion substance layer is formed on the substrate.

[0008] In particular, process steps (a) and (b) can be performed in any order or simultaneously. Process steps (c) and (d) can be performed simultaneously if necessary, but usually sequentially. The semiconductor element that emits primary radiation during operation is also referred to below as the "semiconductor element."

[0009] The luminescence conversion substance layer can be formed at least partially by sedimentation, i.e., the sinking of the luminescence conversion substance. For this purpose, some time can elapse between the application of the composition and the actual removal of the solvent. The removal of the solvent in process step (d) and / or the addition of the composition in process step (c) can also be carried out in such a way that the luminescence conversion substance can at least partially settle during this process. The luminescence conversion substance can settle in the presence of the solvent and the matrix material, even if there is already more matrix material than solvent present.During application of the composition in process step (c) and / or during formation of the luminescence conversion substance layer in process step (d), turbulent flows can be avoided, allowing the luminescence conversion substance layer to be formed on the substrate with improved uniformity. This is facilitated by the solvent in the composition compared to conventional compositions without a solvent. Therefore, for example, heating the composition to a temperature above ambient temperature, for example, above 25°C, for application can be omitted, thereby simplifying the process.

[0010] Uniformity can be assessed by taking microsections through the layer and the substrate, or parts of the substrate, for example, in cross-section, and then analyzing them with a microscope or a scanning electron microscope (SEM). This allows, for example, the degree and gradient of luminescence conversion substance attenuation, the density of the phosphor layer, and density gradients to be determined.

[0011] The luminescence conversion substance layer formed in process step (d) can exhibit good adhesion, particularly to the substrate or to the layer on which it is directly produced, so that neither an adhesive nor an adhesive layer is required. This eliminates a work step for applying the adhesive, as well as the adhesive itself. Advantageously, this also improves the radiation characteristics and color homogeneity of a radiation-emitting component with such a luminescence conversion substance layer, since, unlike a conventional component, a transparent adhesive layer cannot inadvertently function as a light guide through which unconverted primary radiation could be coupled out.

[0012] During operation, the semiconductor element emits primary radiation with a first wavelength, where the first wavelength specifies the spectrum of the primary radiation. The luminescence conversion substance converts the primary radiation at least partially into secondary radiation with a second, longer wavelength. The second wavelength specifies the spectrum of the secondary radiation.

[0013] The choice of semiconductor materials is not limited according to the invention. In particular, semiconductor materials that emit primary radiation in the visible range of the spectrum (420 to 780 nm wavelength) or in the UV range (200 to 420 nm wavelength) can be used.

[0014] The choice of luminescence conversion substance is not limited according to the invention. Examples of such luminescence conversion substances and luminescence conversion substance mixtures are: - Chlorosilicates, as disclosed, for example, in DE 100 36 940 A1 and the prior art described therein, - Orthosilicates, sulfides, thiometals and vanadates as disclosed, for example, in WO 00 / 33 390 A1 and the prior art described therein, - aluminates, oxides, halophosphates, as disclosed for example in US 6616862 and the prior art described therein, - Nitrides, siones and sialons as disclosed, for example, in DE 10147040 and the prior art described therein, and - Garnets of rare earths such as YAG:Ce and alkaline earth elements as disclosed, for example, in US 2004 / 0 062 699 A1 and the prior art described therein.

[0015] The luminescence conversion substance can also be a combination of different luminescence conversion substances. The luminescence conversion substance can be present in particles that can be, for example, spherical, platelet-shaped, polyhedral, amorphous, any other defined shape, and / or combinations of these shapes. These particles consist at least partially of the luminescence conversion substance. The disclosure content of the references is hereby incorporated by reference.

[0016] The luminescence conversion layer can, in particular, form uniformly on the substrate and in the beam path of the primary radiation. This can improve the overall uniformity of the radiation and the color impression of the emitted radiation of a component. In this context, "radiation" refers to the superposition of all radiation emitted during operation, for example, the superposition of primary radiation and secondary radiation. The emitted radiation can exhibit any color impression in the CIE diagram, for example, a white color impression.

[0017] According to a further embodiment, process steps (c) and (d) can be performed multiple times in succession. Process steps (b), (c), and (d) can also be performed multiple times in succession, whereby different compositions, for example, with different luminescence conversion substances, can also be used. This makes it possible to adjust the color impression of the emitted radiation particularly precisely. According to a further embodiment, in process step (c), the composition is applied into a recess in the substrate. The semiconductor element can, in particular, be arranged in the recess and / or form a base of the formation.

[0018] According to a further embodiment, the composition applied in process step (c) has a meniscus. Such a meniscus can be formed, for example, by interactions, such as adhesion effects, between the composition and the sidewalls of a recess. Therefore, the formed luminescence conversion substance layer can also have a slightly concave edge. This can be demonstrated, for example, by microsections through the substrate with the luminescence conversion substance layer and subsequent evaluation using a microscope.

[0019] Such a meniscus may sometimes be only weakly formed if the luminescence conversion substance layer has a very high density. Embodiments are also conceivable in which no meniscus can be detected, for example, if the luminescence conversion substance layer contains only a small amount of matrix material.

[0020] According to a further embodiment, in process step (c) the composition is applied directly to the semiconductor element.

[0021] The fact that a first layer, a first region or a first device is arranged or applied "on" a second layer, a second region or a second device can mean in this application that the first layer, the first region or the first device is arranged or applied in direct mechanical and / or electrical contact on the second layer, the second region or the second device or with the two further layers, regions or devices. Furthermore, indirect contact can also be referred to, in which further layers, regions and / or devices are arranged between the first layer, the first region or the first device and the second layer, the second region or the second device or the two further layers, regions or devices.

[0022] The luminescence conversion substance layer can thus also be formed directly on the semiconductor element. The luminescence conversion substance layer exhibits particularly good adhesion to the surface of the semiconductor element, eliminating the need for adhesives. The luminescence conversion substance layer can be bonded to the semiconductor element in a form-fitting and / or force-fitting and / or material-fitting manner, which occurs in particular via the matrix material. The luminescence conversion substance layer can uniformly cover the exposed surfaces of the semiconductor element, thereby achieving the advantages already described.

[0023] Because the exposed surfaces of the semiconductor element are more evenly covered with luminescence conversion material than in the prior art, spots or areas with insufficient conversion of the primary radiation are reduced or completely eliminated. Therefore, compared to conventional components in which, for example, a luminescence conversion material element is arranged on a semiconductor element with an adhesive layer, the radiation can be emitted more evenly. In contrast, such an adhesive layer can act like a light guide and couple out radiation. However, this is then only insufficiently converted or not converted at all, resulting in an uneven color impression of the emitted radiation (so-called blue piping).

[0024] If the luminescence conversion substance layer is formed directly on the semiconductor element, the heat generated by radiation conversion can be better dissipated and dissipated via the semiconductor element than is the case with a conventional arrangement with an adhesive layer between the semiconductor element and the luminescence conversion substance element. This can improve the conversion efficiency of the luminescence conversion substance, since it is generally more efficient at low temperatures than at higher temperatures. This allows the semiconductor element to be operated at higher currents, for example.

[0025] According to a further embodiment, the semiconductor element in the substrate provided in method step (a) has a reflective material on its lateral surfaces. This allows only one main surface of the semiconductor element to be exposed, so that the luminescence conversion material layer formed in method step (d) is generated only on this main surface. Thus, the primary radiation is emitted only, or at least primarily, through this main surface of the semiconductor element, which can lead to further improved color consistency and more uniform radiation.

[0026] Reflective materials such as TiO 2 , ZrO 2 , Al 2 O 3 , glass, SiO 2 Particles and combinations of these materials can be used. These materials can be arranged either directly or, for example, in a matrix made of a glass or a polymer material.

[0027] For example, as already explained, the semiconductor element can be arranged in a recess of the substrate, and the reflective material can be used to create a flat surface that encompasses the main surface of the semiconductor element. This allows the luminescence conversion material layer to be formed with improved uniformity.

[0028] According to a further embodiment, the substrate provided in method step (a) has a recess whose lateral boundaries form structures comprising or consisting of a photoresist. The composition can be applied into this recess in method step (c). The lateral boundaries can be shaped such that the bottom of the recess is at least partially formed by the semiconductor element or a main surface of the semiconductor element. This enables, in particular, a uniform formation of the luminescence conversion substance layer directly on the semiconductor element.

[0029] According to a further development of this embodiment, in a further method step (e), the structures comprising a photoresist are removed. This can be done by irradiation, for example, with UV radiation, so that the photoresist can subsequently be easily removed, for example, with a solvent. The areas in which the photoresist was removed have little or no residue of the composition or the luminescence conversion substance layer, so that the semiconductor element can be easily divided in these areas.

[0030] For example, chips can be produced from the semiconductor element that have a luminescence conversion substance layer according to at least one embodiment of the invention on a main surface. In particular, several such semiconductor chips, which emit radiation with a desired color impression during operation, for example, white, can be produced in parallel. For example, these semiconductor chips can be used in components, so that a further step for applying luminescence conversion substances can be omitted, thereby simplifying the manufacture of the components and reducing production costs.

[0031] According to a further embodiment, in process step (d), a semiconductor chip emitting with a white color impression is obtained from the semiconductor element and the luminescence conversion substance layer. Several such semiconductor chips emitting with a white color impression can also be produced in parallel, as described above.

[0032] The composition in process step (c) has a viscosity of < 1 Pa*s upon application. The composition may have a viscosity of ≤ 100 mPa*s and in particular ≤ 50 mPa*s, for example < 20 mPa*s, upon application in process step (c). Viscosity here indicates the dynamic viscosity of the composition and is determined using a rheometer.

[0033] The low viscosity of the composition ensures uniform wetting of the surfaces to which it is applied. In particular, this compensates for (minor) unevenness. The low viscosity also results in the composition's low surface tension. A further advantage is that sedimentation of the luminescence conversion substance, or of the particles containing or consisting of the luminescence conversion substance, occurs particularly uniformly and can usually occur to a significant extent. This results in the formation of a particularly uniform luminescence conversion substance layer on the substrate in process step (d). Furthermore, such a composition is easy to handle and dose.

[0034] According to a further embodiment, the composition provided in process step (b) is designed such that it can be applied via a needle-shaped outlet with an opening diameter of ≤ 1 mm, in particular 0.1 to 0.5 mm.

[0035] In addition to the selection of the components of the composition, a reduction in viscosity can also be achieved by heating the composition during or before process step (c). Additionally or alternatively, the composition can be stirred, shaken, and / or forced through a needle, thereby shearing the composition. Due to the shearing, the viscosity decreases.

[0036] According to a further embodiment, in method step (d), a luminescence conversion substance layer is formed which has a layer thickness of ≤ 60 µm, in particular ≤ 50 µm, and often ≤ 40 µm. This means that the formed luminescence conversion substance layer generally has a smaller layer thickness than is the case with conventional luminescence conversion substance elements, which generally have layer thicknesses of ≥ 80 µm. Thus, the luminescence conversion substance layer according to the application also allows for the realization of smaller components or components with a lower height, and heat dissipation across the semiconductor element can be improved.

[0037] According to a further embodiment, in process step (d), a luminescence conversion substance layer is formed which has a luminescence conversion substance content of ≥ 50 wt.% (wt.% = weight percent). The luminescence conversion substance content can be ≥ 75 wt.% and in particular ≥ 85 wt.%, for example 90 wt.%. This information refers to the total mass of the luminescence conversion substance layer. The luminescence conversion substance layer can adhere well to the substrate or to the semiconductor element even with a high luminescence conversion substance content. In particular, the materials are selected such that, regardless of the specific wt.% content, a luminescence conversion substance layer is formed which has > 35 vol.%, in particular > 45 vol.%, for example 50 vol.%, of luminescence conversion substance (vol.% = volume percent).

[0038] Advantages of such a high luminescence conversion substance concentration include, for example, good thermal conductivity. This allows the heat radiated by the semiconductor element, and in particular the heat generated during conversion, to be more effectively dissipated by the luminescence conversion substance layer. Improved heat dissipation also leads to higher conversion efficiency. Furthermore, the color homogeneity of the radiation emitted by a component is also increased.

[0039] Since the composition used to produce the luminescence conversion substance layer contains a solvent, the luminescence conversion substance can be present in higher concentrations in the luminescence conversion substance layer after at least partial removal of the solvent than is the case with conventional layers or elements. The luminescence conversion substance layer can therefore be formed according to the application such that it has a denser packing of luminescence conversion substance than in the prior art. The luminescence conversion substance can at least partially form a densest packing in the matrix material.

[0040] According to a further embodiment, the luminescence conversion substance layer formed in process step (d) has a matrix material content of ≤ 50 wt.%. The matrix material content can be ≤ 25 wt.% and in particular ≤ 15 wt.%, for example 10 wt.%. The luminescence conversion substance layer can thus be formed largely or entirely from luminescence conversion substance and matrix material.

[0041] According to a further embodiment, the composition is applied such that, before and / or during process step (d), the luminescence conversion substance is sedimented within 60 minutes, and in particular within 30 minutes, for example within 15 minutes. Partial or complete sedimentation of the luminescence conversion substance generally occurs within this period. Afterward and / or during this time, the solvent can be at least partially removed.

[0042] According to a further embodiment, in process step (d), the solvent is removed at elevated temperature and / or at reduced pressure and / or by irradiation. An elevated temperature means a temperature above room temperature (25°C), so that the solvent can be removed more easily or more quickly.

[0043] According to a further development of this embodiment, in process step (d) the solvent is removed at a temperature between 40 and 160°C and in particular between 40 and 80°C, for example at 60°C.

[0044] According to a further development of this embodiment, in process step (d), the solvent is removed at a pressure between 0.5 and 800 mbar, and in particular between 1 and 100 mbar, for example at 10 mbar. A negative pressure accelerates the removal of the solvent.

[0045] According to a further development of this embodiment, in process step (d), radiation is used to remove the solvent. The radiation can be, for example, beta or gamma radiation. UV radiation or infrared radiation can also be used. In principle, microwaves can also be used for irradiation or heating. The radiation used for irradiation does not correspond to the radiation emitted during operation of the semiconductor element.

[0046] For at least partial removal, the solvent can be heated in process step (d) and / or a vacuum can be applied and / or irradiated with radiation in any combination. The solvent is generally largely removed in process step (d), so that the luminescence conversion substance layer has only a small or no residual solvent content.

[0047] According to a further embodiment, the luminescence conversion substance layer formed in process step (d) contains a residual solvent content of up to 5 wt% and in particular up to 3 wt%, typically 1 to 2 wt%. A small residual solvent content can be used to improve the adhesion of the luminescence conversion substance layer to the substrate or to the semiconductor element. The solvent can therefore act as an adhesion promoter. The residual solvent content in the luminescence conversion substance layer can be determined by means of solid-state nuclear magnetic resonance spectroscopy (solid-state NMR).

[0048] In process step (d), a luminescence conversion substance layer is formed in which the concentration of the luminescence conversion substance in a matrix comprising or consisting of the matrix material exhibits a gradient. This gradient can be formed, for example, as a result of the sedimentation of the luminescence conversion substance.

[0049] Such a gradient can be designed such that a higher concentration of luminescence conversion substance is present in the regions of the formed luminescence conversion substance layer facing the substrate or the semiconductor element than in the regions facing away. The gradient can be linear, for example. A gradient can be used for a gradually varying effective refractive index. For example, the refractive index difference (so-called index jump) between the semiconductor element and the luminescence conversion substance can be reduced compared to a silicone potting compound optionally arranged thereon or compared to a gas atmosphere, thereby improving radiation outcoupling.

[0050] According to a further embodiment, the composition provided in process step (b) contains, in addition to matrix material and solvent, 2 to 50 wt% and in particular 5 to 30 wt% of luminescence conversion substance. During at least partial removal of the solvent in process step (d), the proportion of luminescence conversion substance is increased until the solvent is sufficiently removed and the luminescence conversion substance layer is formed.

[0051] According to a further embodiment, the particles of the luminescence conversion substance in the composition provided in process step (b) have an average diameter of ≤ 20 µm and in particular ≤ 10 µm. This allows for thinner layer thicknesses compared to conventional luminescence conversion elements. However, the particle size is not particularly limited in the process. For example, very small particles can also be used, which would not sediment in a conventional process without solvent. The average particle diameters can be determined using a sieving method.

[0052] According to a further embodiment, at least 95 wt% and in particular at least 99 wt% of the particles of the luminescence conversion substance in the composition provided in process step (b) have a maximum diameter of ≤ 20 µm and in particular of ≤ 15 µm. According to a further embodiment, at least 95% and in particular at least 99% of the particles of the luminescence conversion substance in the composition provided in process step (b) have a minimum diameter of ≥ 2 µm and in particular ≥ 5 µm. Smaller particles can be separated beforehand, for example, by a sieving process. Radiation can be strongly scattered, particularly by small particles, for example, with a diameter of up to 2 µm. This improves transmission because fewer radiation losses occur in the luminescence conversion substance layer.

[0053] According to a further embodiment, the composition provided in process step (b) contains 5 to 25 wt% matrix material. The composition may contain ≤ 15 wt%, for example 10 wt%, matrix material.

[0054] According to a further embodiment, the matrix material in the composition provided in process step (b) is selected from: silicone, epoxy resin, acrylic resin, precursors of these polymer compounds, and combinations of the aforementioned materials. Combinations also include hybrid materials. A combination of silicone and epoxy resin, for example, can therefore also be a silicone-epoxy hybrid material. If the matrix material contains or consists of precursors of polymer compounds, these can be at least partially crosslinked in process step (d) during the formation of the luminescence conversion substance layer. Crosslinking can occur by curing, for example by heating and / or irradiation with the radiation mentioned above. This can occur simultaneously and / or after removal of the solvent.The matrix material is particularly transparent to primary radiation as well as to secondary radiation, so that only minimal radiation losses occur through the matrix material in the luminescence conversion layer.

[0055] According to a further embodiment, the matrix material in the composition provided in process step (b) is a silicone. The silicone may contain or consist of a commercially available silicone, in particular polydialkylsiloxane, polydiarylsiloxane, polyalkylarylsiloxane, or a combination thereof. Examples of such a silicone are poly(dimethylsiloxane), polymethylphenylsiloxane, or a combination thereof.

[0056] According to a further embodiment, the composition provided in process step (b) contains 30 to 95 wt.%, in particular 50 to 75 wt.%, for example 60 wt.%, of solvent. Thus, the composition generally has a significantly larger volume than the luminescence conversion substance layer formed in process step (d).

[0057] According to a further embodiment, the solvent in the composition provided in process step (b) is suitable for dissolving the matrix material and in particular a silicone.

[0058] According to a further embodiment, the solvent in the composition provided in process step (b) is selected from: ester, ether, silyl ether, disiloxane, aliphatic, aromatic hydrocarbon, halogenated hydrocarbon, and combinations of these solvents. The solvent is generally volatile, so that it can be easily at least partially removed in process step (d). For example, the solvent may have a boiling point of ≤ 120°C at atmospheric pressure (1013.25 mbar hPa). Therefore, there is no risk of damage to the luminescence conversion substance layer upon removal of the solvent; damage typically only occurs after prolonged heating above 200°C.

[0059] Low-molecular-weight compounds that can be used as precursors for polymer compounds are typically not considered solvents but rather matrix materials. Examples of such low-molecular-weight compounds include acrylic and methacrylic acid derivatives, epoxides, olefins, isocyanates, and similar polymerizable compounds. It is essential, in any case, that the solvent is at least partially removed in process step (d), for example, to ≥ 90 vol% and especially ≥ 95 vol% (vol% = volume percent).

[0060] According to a further embodiment, the solvent in the composition provided in process step (b) is a disiloxane, for example hexamethyldisiloxane (Me 3 SiOSiMe 3This solvent has the particular advantage of being able to dissolve silicones very well, being comparatively volatile, and being used in low concentrations as an adhesion promoter in the luminescence conversion layer. Other typical solvents are toluene and benzene as aromatic hydrocarbons, which can be used alone or in combination with other solvents, such as hexamethyldisiloxane.

[0061] The composition provided in process step (b) can be formed, for example, by mixing the luminescence conversion substance, matrix material, and solvent. In principle, it is possible to mix a conventional printing paste containing a luminescence conversion substance, such as that used for printing luminescence conversion elements, with a solvent and thereby obtain a composition according to at least one embodiment of the invention.

[0062] According to a further embodiment, a potting compound is arranged on the substrate provided in method step (a). Therefore, the luminescence conversion substance layer is not arranged directly on the semiconductor element. This potting compound can be arranged, for example, in the beam path of the primary radiation and / or in the beam path of radiation partially converted by a further, second luminescence conversion substance. This second luminescence conversion substance can be arranged, for example, in a conventional element, in a luminescence conversion substance layer according to at least one embodiment of the invention, or distributed in the potting compound. The luminescence conversion substances already described can be used as the second luminescence conversion substance. The luminescence conversion substance layer can also be formed on the potting compound in method step (d) as an element for so-called remote phosphor conversion.In this case, no second luminescence conversion substance is required. Remote phosphor conversion refers to radiation conversion that occurs at a large distance from the radiation source, for example, > 750 µm.

[0063] Typically, according to this embodiment, the composition is applied directly to the potting compound in process step (c). In particular, this allows the color impression of the radiation to be very finely adjusted. This often also improves the uniformity of the radiation.

[0064] It is therefore possible, for example, to provide a radiation-emitting component comprising a radiation-emitting semiconductor element as well as a second luminescence conversion substance and a potting compound as the substrate in method step (a), to determine the color impression of the radiation emitted by the component, and subsequently to adjust this color impression using a luminescence conversion substance layer formed on the potting compound according to at least one embodiment of the invention. This can be carried out individually for each component or each substrate.

[0065] According to a further development of this embodiment, in method step (d), a luminescence conversion substance layer is formed in which the concentration of luminescence conversion substance decreases toward the lateral sides. Thus, the concentration of luminescence conversion substance is higher in the center of the formed luminescence conversion substance layer, resulting in a higher conversion there.

[0066] In conventional components, the color location of the radiation can depend on the angle θ to the main emission direction (θ = 0°) of the radiation. This means that the radiation is emitted with a non-uniform color impression. Using the method according to at least one embodiment of the invention, a luminescence conversion substance layer can be formed such that such a different color impression is at least partially compensated. For example, a thin luminescence conversion substance layer can be produced on a potting compound in which the concentration of luminescence conversion substance has a gradient. The concentration can be higher, in particular, in the main emission direction than at an angle to the main emission direction.

[0067] In this way, the dependence of the colour impression on the angle θ can be at least partially reduced, resulting in a more uniform colour impression overall.

[0068] According to a further development of this embodiment, the luminescence conversion substance layer formed in process step (d) has a layer thickness of ≤ 30 µm, for example, 20 µm. Such a thin luminescence conversion substance layer will therefore convert a smaller proportion of the incident radiation compared to a thicker layer. Thus, the color coordinate of the radiation can be very finely adjusted, which is particularly important in an embodiment of the invention in which the composition is applied to a potting compound in process step (c).

[0069] According to a further development of this embodiment, in process step (d), a luminescence conversion substance layer is formed in which at least 85% of the particles of the luminescence conversion substance are arranged as a monolayer or submonolayer. For example, the concentration of luminescence conversion substance can be increased in the region of the main emission direction of a component. More than one layer of luminescence conversion substance particles can be present in this region. Evidence of the particle arrangement in the luminescence conversion substance layer can be determined by microsections and subsequent SEM analysis.

[0070] According to the application, a composition for producing a luminescence conversion layer is also specified, comprising: - a luminescence conversion substance, - a matrix material and - a solvent.

[0071] The composition can also consist of these materials. The composition can be used in particular for a method according to at least one embodiment of the invention to produce a luminescence conversion substance layer on a substrate or on a semiconductor element. The composition can thus have the properties already described above.

[0072] According to the application, a component is also specified that contains a semiconductor element that emits primary radiation during operation and a luminescence conversion substance layer arranged in the beam path of the emitted primary radiation, which can be produced or is produced by the method according to at least one embodiment of the invention. The radiation emitted by the component thus has, in particular, a uniform color impression.

[0073] The component may comprise the usual components of an optoelectronic component, such as electrical leads, a lead frame, a bonding pad, a bonding wire, solder compound, etc. A recess of the component may be at least partially filled with a potting compound.

[0074] The semiconductor element may, for example, comprise a thin-film light-emitting diode chip, which is characterized in particular by the following characteristic features: - a reflective layer is applied or formed on a first main surface of a radiation-generating epitaxial layer sequence facing a carrier element, said reflective layer reflecting at least part of the electromagnetic radiation generated in the epitaxial layer sequence back into the epitaxial layer sequence; - the epitaxial layer sequence has a thickness in the range of 20 µm or less, in particular in the range of 10 µm and often in the range of 2 µm; and - the epitaxial layer sequence contains at least one semiconductor layer with at least one surface which has a mixing structure which ideally leads to an approximately ergodic distribution of the radiation in the epitaxial epitaxial layer sequence, i.e. it has as ergodic stochastic scattering behaviour as possible.

[0075] A basic principle of a thin-film light-emitting diode chip is described, for example, in I. Schnitzer et al., Appl. Phys. Lett. 63 (16), October 18, 1993, 2174-2176, the disclosure content of which is hereby incorporated by reference.

[0076] The invention is explained in more detail below with reference to exemplary embodiments and drawings. Like reference numerals indicate like elements in the individual figures. However, references are not to scale; rather, individual elements may be enlarged and / or shown schematically for better understanding.

[0077] It shows Fig. 1a to Fig. 1c shows several method steps of a method according to at least one embodiment of the invention; Fig. 2 shows a further substrate on which a luminescence conversion substance layer according to an embodiment of the invention is formed; Fig. 3a to Fig. 3d further embodiments of the invention; and Fig. 4a to Fig. 4d further embodiments of the invention in which the composition is formed on a potting compound.

[0078] The Fig. 1a to 1c show a cross-section through a substrate 1 comprising a recess 5, for example, in a housing made of plastic or ceramic, and a semiconductor element 10, which can emit primary radiation during operation and is arranged in the recess 5. The housing can contain reflective materials (not shown). Furthermore, the substrate 1 can comprise the usual components of an optoelectronic component, such as electrical leads, a lead frame, a bond pad, a bond wire, soldering compound, etc. (not shown for the sake of clarity), so that an optoelectronic component can be produced from the substrate.

[0079] In Fig. 1a shows, among other things, a composition 21 according to at least one embodiment of the invention, which was applied to the substrate 1 in a method step (c). In this case, the composition 21 was applied into the recess 5 and directly onto the substrate 1 or onto the semiconductor element 10. The composition 21 contains 2 to 50 wt. %, for example 30 wt. %, of luminescence conversion substance particles 25. Furthermore, the composition 21 contains 5 to 25 wt. %, for example 10 wt. %, of matrix material, for example a silicone, and 50 to 75 wt. %, for example 60 wt. %, of solvent. Hexamethyldisiloxane can be used as the solvent.

[0080] In Fig. Figure 1b shows a moment of a process step (d) according to at least one embodiment of the invention, in which a large part of the luminescence conversion substance 25 has already sedimented and a part of the solvent has been removed or is currently being removed, as indicated by the arrow 22. It is also possible for the luminescence conversion substance 25 to be (completely) sedimented first, and then the solvent to be at least partially removed (not shown).

[0081] In Fig. 1c shows a completed method step (d) according to at least one embodiment of the invention. A luminescence conversion substance layer 20, which is also referred to below as "layer 20," is uniformly produced directly on the exposed surfaces of the semiconductor element 10 or on the substrate 1. The concentration of luminescence conversion substance 25 in the matrix material of the layer 20 is higher in the regions adjacent to the semiconductor element 10 or the substrate 1 than in the remote regions of the layer 20, so that a gradient is present. The layer 20 is, in particular, uniformly produced on the semiconductor element 10, so that radiation with a uniform color impression can be emitted uniformly during operation. This avoids, for example, so-called blue piping.

[0082] The formed layer 20 generally comprises at least 75 wt%, in particular 85 wt%, for example 90 wt%, of luminescence conversion substance 25. Furthermore, the layer 20 may contain at most 25 wt%, in particular at most 15 wt%, such as 9 wt%, of matrix material and 1 to 2 wt%, for example 1 wt%, of solvent.

[0083] The substrate 1 on which a luminescence conversion substance layer 20 is produced according to at least one embodiment of the invention can be used to produce a component. For example, a conventional encapsulant, for example made of a silicone or an epoxy resin, can be arranged on the layer 20 and optionally shaped as a lens (not shown). Such a component can emit radiation with any desired color impression, for example, white.

[0084] In Fig. 2 shows a further embodiment of the invention, in which the substrate 1 is made, for example, of Fig. 1a additionally has a layer 15 containing reflective materials such as TiO 2 comprises or consists of. For example, the semiconductor element 10 and the layer 15 can form a flat or nearly flat (including deviations of ≤ 15 µm) surface. In this example, a layer 20 is produced directly on the semiconductor element 10 or on the substrate 1.

[0085] In Fig. 3a shows a substrate 1 as provided according to at least one embodiment of the invention in a method step (a). The substrate 1 can be a semiconductor element 10 on which structures 6 are produced. The structures 6 can be arranged directly on the semiconductor element 10 and comprise or consist of a photoresist. The structures 6 and the semiconductor element 10 form, for example, a recess 5, wherein the bottom of the recess 5 can be formed by the semiconductor element 10, as shown.

[0086] The substrate 1 of the Fig. 3a can, for example, be a section of a substrate 1 as shown in Fig. 3b, which comprises a plurality of recesses 5, so that according to at least one embodiment of the invention a plurality of luminescence conversion substance layers 20 can be produced thereon in parallel.

[0087] In Fig. 3c is a substrate 1 of the Fig. 3a and / or Fig. 3b, on which the layer 20 is produced directly on the substrate 1 or the semiconductor element 10. The layer 20 is particularly uniformly formed.

[0088] In Fig. 3d shows a component, a semiconductor chip 50, which, after a process step (e), is made of the substrate 1 with a layer 20, as shown in Fig. 3c. For this purpose, the structures 6 were irradiated with UV radiation and subsequently removed. The semiconductor element 10 was divided, for example, by sawing, at least in some of the now uncoated areas.

[0089] The semiconductor chip 50 comprises a semiconductor element 10 having a layer 20 according to at least one embodiment of the invention on a main surface. Thus, the semiconductor chip 50 can emit radiation with any desired color impression during operation, for example, white. The semiconductor chip 50 is particularly suitable for use in an optoelectronic component, which thus requires no additional luminescence conversion substances to emit radiation with a desired color impression during operation. This can, in particular, simplify the production of this optoelectronic component, thereby reducing manufacturing costs.

[0090] In Fig. 4a shows a composition 21 according to at least one further embodiment of the invention, which is applied directly to a potting compound 40 of a substrate 1. The recess 5 can project slightly beyond the potting compound 40 on the sides. The potting compound 40 can, for example, also be convex or concave (not shown). The substrate 1 comprises, for example, a semiconductor element 10 and a second (conventional) luminescence conversion substance element 45, which is arranged on the semiconductor element 10 with a layer 46 of adhesive. Instead of the second luminescence conversion substance element 45, the substrate 1 can also have a luminescence conversion substance layer 20, as can be produced according to at least one embodiment of the invention. The substrate 1 can comprise further components required for an optoelectronic component, as already explained above.The substrate 1 can, for example, be an optoelectronic component that emits radiation with a color impression that is to be adjusted.

[0091] In Fig. 4b shows how on the substrate 1 of Fig. 4a, in a method step (d), a luminescence conversion substance layer 20 according to at least one embodiment of the invention is formed. The layer 20 has a layer thickness of ≤ 30 µm, for example 20 µm, so that only a slight conversion occurs, which can be used to adjust the color impression of emitted radiation. In the layer 20, at least 85% of the particles of the luminescence conversion substance 25 are arranged in a monolayer or submonolayer, wherein the concentration in the region of the main emission direction (θ = 0°), which is represented by the arrow 60, is higher than in other regions of the layer 20.

[0092] In Fig. 4c shows a further component in which a luminescence conversion substance layer 20 according to at least one embodiment of the invention is produced directly on a potting compound 40. The luminescence conversion substance layer 20 can be the layer 20 of Fig. 4b. In this case, no second (conventional) luminescence conversion substance element 45 is arranged on the semiconductor element 10, but rather particles 41 containing or consisting of a second luminescence conversion substance are distributed in the potting compound 40.

[0093] In Fig.4d shows a further component comprising a luminescence conversion substance layer 20 formed according to at least one embodiment of the invention. In this case, no further luminescence conversion substances are present, since the luminescence conversion substance layer 20 is formed as an element for so-called remote phosphor conversion, for example, directly on a potting compound 40.

Claims

[1] Method for producing a luminescence conversion substance layer (20) on a substrate (1) with a semiconductor element (10) emitting primary radiation during operation, comprising the method steps: (a) providing the substrate (1); (b) providing a composition (21) comprising a luminescence conversion substance (25), a matrix material and a solvent; (c) applying the composition (21) to the substrate (1), wherein the composition (21) has a viscosity of < 1 Pa*s upon application; (d) removing at least a portion of the solvent so that the luminescence conversion substance layer (20) is formed on the substrate (1), in which the concentration of the luminescence conversion substance (25) in a matrix comprising the matrix material has a gradient. [2] Method according to the preceding claim, wherein in method step (c) the composition (21) is applied into a recess (5) of the substrate (1). [3] Method according to one of the preceding claims, wherein in method step (c) the composition (21) is applied directly to the semiconductor element (10). [4] Method according to one of the preceding claims, wherein in method step (d) a luminescence conversion substance layer (20) is formed which has a layer thickness of ≤ 60 µm, in particular of ≤ 50 µm. [5] Method according to one of the preceding claims, wherein in method step (d) a luminescence conversion substance layer (20) is formed which has a content of luminescence conversion substance (25) of ≥ 75 wt% and in particular of ≥ 85 wt%. [6] Method according to one of the preceding claims, wherein the composition (21) provided in method step (b) contains 2 to 50 wt% and in particular 5 to 30 wt% of luminescence conversion substance (25). [7] Method according to one of the preceding claims, wherein in the composition (21) provided in method step (b) at least 95 wt% of the particles of the luminescence conversion substance (25) have a maximum diameter of ≤ 20 µm and in particular of ≤ 15 µm. [8] A process according to any one of the preceding claims, wherein the composition (21) provided in process step (b) contains 5 to 25 wt% matrix material. [9] A method according to any one of the preceding claims, wherein in the composition (21) provided in step (b), the matrix material is selected from: silicone, epoxy resin, acrylic resin, percursors of these polymer compounds and combinations of said materials. [10] A process according to any one of the preceding claims, wherein in the composition (21) provided in step (b) the solvent is selected from: ester, ether, silyl ether, disiloxane, aliphatic, aromatic hydrocarbon, halogenated hydrocarbon and combination of said solvents. [11] Method according to one of claims 1 to 2 and 4 to 10, wherein a potting compound (40) is arranged on the substrate (1) provided in method step (a). [12] Composition (21) having a viscosity of < 1 Pa*s for producing a luminescence conversion substance layer (20) in which the concentration of a luminescence conversion substance (25) in a matrix comprising a matrix material has a gradient, comprising: - a luminescence conversion substance (25), - a matrix material and - a solvent. [13] Component comprising a semiconductor element (10) which emits primary radiation during operation, and a luminescence conversion substance layer (20) arranged in the beam path of the emitted primary radiation, which can be produced by a method according to one of claims 1 to 11.

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