Method for producing an optoelectronic component

Abstract

The invention relates to a method for producing an optoelectronic component, comprising the following method steps: providing a support having a top side. Arranging an optoelectronic semiconductor chip on the top side of the support. Furthermore, arranging a potting material on the top side of the support, embedding the optoelectronic semiconductor chip in the potting material. The potting material forms a potting surface. A portion of the potting material is removed at the potting surface. In this case, a topography is generated at the potting surface.

Description

Technical Field

[0001] The invention relates to a method for producing an optoelectronic component according to the independent claim.

[0002] This patent application claims the priority of German patent application 10 2017 117 438.9, the disclosure content of which is incorporated herein by reference. Background Art

[0003] Optoelectronic components having optoelectronic semiconductor chips embedded in a potting compound are known from the prior art. Also known from the prior art are optoelectronic components whose potting compound has a roughened potting surface. Summary of the invention

[0004] It is an object of the present invention to provide a method for producing an optoelectronic component.

[0005] This object is achieved by a method for producing an optoelectronic component having the features of the independent claim. Different developments are given in the dependent claims.

[0006] The method for manufacturing an optoelectronic component has the following method steps. A carrier having an upper side is prepared. An optoelectronic semiconductor chip is arranged on the upper side of the carrier. A casting material is also arranged above the upper side of the carrier, wherein the optoelectronic semiconductor chip is embedded in the casting material. The casting material forms a casting surface. A portion of the casting material is removed at the casting surface. Thus, a topography is generated at the casting surface. The topography generated by removing a portion of the casting material at the casting surface provides the following advantages: electromagnetic radiation arriving from the outside can be scattered at the casting surface. Thereby, the specular reflection of the electromagnetic radiation at the casting surface can be suppressed. In this way, the gloss of the casting surface can be reduced or eliminated. For example, this is very important for a display screen that can include multiple optoelectronic components and is arranged in a bright environment. Suppressing the specular reflection at the casting surface can, for example, make the element (especially the display of the element as dark or black) be displayed without a gloss effect. The method for manufacturing an optoelectronic component provides the following advantages: such a topography of the casting surface can be created in a simple manner, namely by removing a portion of the casting material at the casting surface.

[0007] In one form of embodiment, the casting material is hardened before removing a portion of the casting material at the casting surface. Advantageously, the hardening of the casting material makes it possible to remove a portion of the casting material at the casting surface, wherein the topography generated at the casting surface is maintained.

[0008] In one form of embodiment, the removal of a portion of the casting material at the casting surface is performed by wet chemical etching. Advantageously, the wet chemical etching is very easy to perform.

[0009] In one form of embodiment, the etchant is sprayed onto the casting surface.This variant of the method can also be used advantageously for producing a plurality of optoelectronic components, since the etchant is sprayed over a large area.

[0010] In one form of embodiment, the casting surface is immersed in an etchant. Advantageously, the etchant is not atomized in this way. This is particularly advantageous in cases where the etchant is harmful to health.

[0011] In one form of embodiment, the removal of a portion of the casting material at the casting surface is performed by dry etching. The removal of a portion of the casting material at the casting surface by dry etching is advantageously performed without using etchants that are potentially hazardous to health.

[0012] In one form of embodiment, the removal of a portion of the casting material at the surface of the casting is performed by laser interference structuring. The removal of a portion of the casting material at the surface of the casting by laser interference structuring is advantageously performed without the use of etchants that are potentially harmful to health. Another advantage is found in that the topography generated at the surface of the casting can be monitored, since the precise formation of the topography is influenced by the interference pattern.

[0013] In one form of embodiment, the casting material comprises embedded particles. Advantageously, the particles can be arranged to dispersedly scatter incident electromagnetic radiation in the casting material. This can reduce the gloss at other components of the optoelectronic component. Other particles can be provided, for example, to suppress the gloss at a lead frame, where the optoelectronic semiconductor chip can be arranged. In addition, the particles can be arranged to adjust the thermal expansion coefficient of the casting material. For example, the carrier and the casting material may have different thermal expansion coefficients, so that thermal stresses, for example, during the operation of the optoelectronic component, lead to damage to the optoelectronic component. Thermal stresses can, for example, have the effect of delaminating the casting material from the carrier, whereby, for example, moisture can penetrate into the optoelectronic component. The particles can be configured to prevent this effect.

[0014] In one form of embodiment, the particles are exposed by removing a portion of the casting material at the casting surface. Advantageously, the particles exposed at the casting surface contribute to the creation of a diffusely scattering casting surface.

[0015] In one form of embodiment, particles are released from the casting material when a portion of the casting material at the casting surface is removed. Advantageously, the particles released when a portion of the casting material at the casting surface is removed leave irregularities in the casting surface, which can also contribute to the fact that incident electromagnetic radiation can be dispersedly scattered at the casting surface.

[0016] In one form of embodiment, the casting material comprises a wavelength-converting fluorescent material. The wavelength-converting fluorescent material is advantageously configured to modify the wavelength of the electromagnetic radiation that can be emitted from the optoelectronic semiconductor chip, since the wavelength-converting fluorescent material absorbs the electromagnetic radiation emitted from the optoelectronic semiconductor chip and thereupon emits electromagnetic radiation with a different wavelength. For example, it is conceivable that the optoelectronic semiconductor chip is designed to emit blue light, while the wavelength-converting fluorescent material embedded in the casting material is configured to absorb blue light and emit yellow light, for example. In this case, the optoelectronic component may radiate full light and give the impression of being white. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above-mentioned properties, features and advantages of the present invention and the ways to achieve them will become clearer and more clearly understood in conjunction with the following description of exemplary embodiments, which will be explained in more detail in conjunction with the accompanying drawings. Here, in the drawings, each of which is schematic:

[0018] Figure 1 : shows the spraying of etchant on the casting surface;

[0019] Figure 2 : shows the casting surface being immersed in an etchant;

[0020] Figure 3 : shows dry etching of the casting surface;

[0021] Figure 4 : shows the removal of casting material at the casting surface by laser interference structuring; and

[0022] Figure 5 :shows the Figures 1 to 4 Side view of an optoelectronic component manufactured by one of the methods shown. DETAILED DESCRIPTION

[0023] Figures 1 to 4 In each case a variant of a method for producing an optoelectronic component 10 is shown.

[0024] A carrier 20 having an upper side 21 is prepared. Figure 1In the example shown in , the carrier 20 is formed as a housing. The carrier 20 configured as a housing comprises a cavity 23 which is laterally surrounded by a wall 24. However, this is not an essential requirement. The carrier 20 may also be a flat substrate, so that the cavity 23 and the wall 24 may be omitted. Figures 1 to 5 2 shows, by way of example, only the following variant of the carrier 20 in which the carrier 20 is formed as a housing.

[0025] If the carrier 20 is formed as a housing, it may include plastic, such as polyphthalamide (PPA). The carrier 20 may be manufactured, for example, using a molding method, such as an injection molding method. If the carrier 20 is a flat substrate, the carrier 20 may be, for example, a metal substrate, a semiconductor substrate, a semiconductor oxide substrate, a ceramic substrate, a glass substrate, or a printed circuit board.

[0026] The optoelectronic semiconductor chip 30 is arranged above the upper side 21 of the carrier 20 . The optoelectronic semiconductor chip 30 comprises an upper side 31 and an underside 32 opposite the upper side 31 . The optoelectronic semiconductor chip 30 is arranged with its underside 32 above the upper side 21 of the carrier 20 .

[0027] For example, the optoelectronic semiconductor chip 30 may be designed to emit electromagnetic radiation at its upper side 31. However, the optoelectronic semiconductor chip 30 may also be designed to detect electromagnetic radiation reaching the upper side 31. The optoelectronic semiconductor chip 30 may therefore be, for example, a light emitting diode chip or a photodiode chip.

[0028] In order to supply the optoelectronic semiconductor chip 30 with electrical energy for operation, the carrier 20 comprises laterally protruding electrical terminals 22. The electrical terminals 22 can, for example, be part of a metal lead frame that can be embedded in the carrier 20, which is formed as a housing. The lead frame usually typically comprises a first lead frame segment and a second lead frame segment, wherein the lead frame segment is exposed at the upper side 21 of the carrier 20 (at the Figure 1 The optoelectronic semiconductor chip 30 can be arranged at a first section of the lead frame, wherein the optoelectronic semiconductor chip 30 can be connected to a second section of the lead frame by means of a bonding wire. In this case, the optoelectronic semiconductor chip 30 comprises a contact surface at its upper side 31 and a further contact surface at its lower side 32.

[0029] exist Figures 1 to 5In the illustration of , one optoelectronic semiconductor chip 30 is arranged above the upper side 21 of the carrier 20. However, a plurality of optoelectronic semiconductor chips 30 may also be arranged above the upper side 21 of the carrier 20. For example, three optoelectronic semiconductor chips 30 may be arranged above the upper side 21 of the carrier 20. The three optoelectronic semiconductor chips 30 may, for example, be designed to emit electromagnetic radiation of different wavelengths. The three optoelectronic semiconductor chips 30 may, for example, form an RGB pixel. In this case, the optoelectronic semiconductor chip 30 emits red, green and blue light.

[0030] The potting material 40 is arranged above the upper side 21 of the carrier 20 . Figure 1 In the example shown, the casting material 40 is arranged in the cavity 23. Since the carrier 20 does not have to be formed as a housing, the casting material 40 also does not have to be arranged in the cavity 23. If, for example, the carrier 20 is formed as a flat substrate, the casting material 40 can be arranged over the upper side 21 of the carrier 20 in such a way that the casting material 40 forms, for example, a lens. In both cases, the casting material 40 forms a casting surface 41.

[0031] The potting material 40 may include a plastic, for example an epoxy or a silicone. The potting material 40 may be arranged over the top 21 of the carrier 20 by means of a metering method, for example.

[0032] exist Figures 1 to 5 In the illustration of FIG. 2 , the casting material 40 is arranged in the cavity 23 up to the upper edge 25 of the wall 24. This is also not an essential requirement. In the case where the carrier 20 is formed as a housing, a plurality of casting materials 40 can also be arranged in layers in the cavity 23. This is Figure 1 In the example indicated, a further compound 43 is arranged above the casting material 40. The further compound 43 also comprises a plastic, such as an epoxy or a silicone. The further compound 43 can also be arranged above the casting surface 41 by means of a quantitative method. However, the further compound 43 can also be omitted. Figure 1 The fact that a further compound 43 can be arranged above the casting surface 41 is explained by way of example. For the sake of simplicity, the further compound 43 is not considered further in the following description.

[0033] The particles 80 are embedded in the casting material 40. The particles 80 may include, for example, silicon dioxide or titanium dioxide. The particles 80 may have Figure 1 80 corresponds to a spherical shape. However, this is not an essential requirement. The particles 80 can also have another shape, for example flocculent. The average diameter of the particles 80 can be, for example, between 1 μm and 30 μm. Deviations from the quoted average diameter are possible.

[0034] The particles 80 can be provided, for example, to dispersely scatter incident electromagnetic radiation in the potting material 40. In this way, it can be ensured that gloss is prevented at the lead frame. The particles 80 can also bring about a setting of the thermal expansion coefficient of the potting material 40. However, the particles 80 can also be omitted.

[0035] Furthermore, the optoelectronic component 10 may have a wavelength conversion fluorescent material 90 embedded in the casting material 40. The wavelength conversion fluorescent material 90 is configured to convert the wavelength of the electromagnetic radiation emitted from the optoelectronic semiconductor chip 30. The wavelength conversion fluorescent material 90 may be present, for example, in the form of particles. Particles that emit electromagnetic radiation from a different spectral region due to absorption of electromagnetic radiation from a first spectral region are considered. The wavelength conversion fluorescent material 90 may, for example, include a granular fluorescent material doped with a rare earth element, such as yttrium aluminum particles doped with cerium ions (Ce:YAG), which are typically configured to generate a larger wavelength by fluorescence. However, the wavelength conversion fluorescent material 90 may also be omitted.

[0036] exist Figures 1 to 4 In all four variants of the method for producing an optoelectronic component 10 illustrated in FIG. 1 , hardening of the casting material 40 takes place before a portion of the casting material 40 is removed at the casting surface 40 .

[0037] In order to generate a topography suitable for dispersedly scattering electromagnetic radiation at the casting surface 41, according to Figure 1 An etchant 51 is sprayed onto the casting surface 41 by means of a spray head 50. The etchant 51 removes a portion of the casting material 40 at the casting surface 41. As a result, grooves and other irregularities 100 appear in the casting surface 41 which are suitable for dispersively scattering electromagnetic radiation.

[0038] However, if Figure 1 As shown in FIG. 5 , wet chemical etching does not necessarily have to be performed by means of a spray etchant 51 . Figure 2 A variant of the method for producing an optoelectronic component 10 is shown, in which the etchant 51 is not sprayed onto the casting surface 41. Instead, the casting surface 41 is immersed in the etchant 51. Figure 2 The element indicated by reference numeral 52 in FIG. 5 represents a container 52 for an etchant 51 .

[0039] The solvent for the casting material 40 may be considered as an etchant 51. If the casting material 40 comprises, for example, ester groups, for example consisting of anhydride-hardened epoxides, then an aqueous or alcoholic solution of potassium hydroxide (potash) or an organic base in a suitable solvent may be used as etchant 51.

[0040] It is conceivable that the etching agent 51 comes into contact not only with the casting surface 41 but also with the plastic forming the housing. In this case, the surface of the housing can also be subjected to an etching process, whereby the housing can also disperse the incident electromagnetic radiation. In addition, a mask is possible, which can allow selective etching of the casting material 40 at the surface of the housing or at the casting surface 41.

[0041] In one form of embodiment of the method for producing an optoelectronic component 10, a portion of the casting material 40 on the casting surface 41 is removed by dry etching, thereby roughening the casting surface 41. This can be done chemically, physically or by a combination of both methods.

[0042] Chemically active ions, excited species or reactive molecules (e.g. ozone) can react with the casting material 40 at the casting surface 41 to produce gaseous reaction products. In this case, the casting surface 41 is chemically etched. The generation of chemically reactive particles can be, for example, by a plasma of a suitable gas (preferably oxygen, hydrogen, NF 3 Or other fluorine-containing gases, or gas mixtures containing one or more of these gases). However, the chemically reactive particles can also be generated without the use of plasma, for example with the aid of an ozone generator.

[0043] The physical removal of a portion of the casting material 40 at the casting surface 41 can be performed by means of ions 60 which are accelerated at the casting surface 41 to be eroded. Figure 3 This variant of the method for producing an optoelectronic component 10 is shown. The accelerated ions 60 can release or atomize fragments 42 of the casting material 40 at the casting surface 41 by pulsed delivery (sputtering). As a result, a topography is generated at the casting surface 41, which causes the electromagnetic radiation that encounters the casting surface 41 to be scattered in a dispersed manner. The ions 60 required for this purpose can be generated by means of a plasma of a suitable gas, such as argon, neon, krypton or other noble gases, or oxygen, or a gas mixture containing these gases.

[0044] The ions 60 are accelerated by the electric and / or magnetic fields. A cathode can be arranged, for example, below the carrier 20, so that the ions 60 are accelerated in the direction of the casting surface 41. The acceleration voltage is then located between the cathode and the ion source, wherein the carrier 20 is arranged between the ion source and the cathode.

[0045] The chemical and physical removal of a portion of the casting material 40 at the casting surface 41 can also be combined with one another, for example by adding reactive gases to the plasma sputtering process.

[0046] By skillful selection of the process parameters, the roughening of the casting surface 41 by removing a portion of the casting material 40 at the casting surface 41 can be adapted to the casting material 40 to be eroded and the desired roughness.

[0047] Figure 4 Another variant of the method for producing an optoelectronic component 10 is shown. In this case, a portion of the casting material 40 at the casting surface 41 is removed by laser interference structuring. Here, at least two lasers 70, 71 emitting coherent laser radiation 72 are directed at the casting surface 41. An interference pattern is generated at the casting surface 41 by the interference between the laser radiation 72 of the first laser 70 and the second laser 71. A topography corresponding to the interference pattern at the casting surface 41 is created at the casting surface 41. The irradiation of the casting surface 41 with the laser radiation 72 occurs with pulses of as high energy as possible, so that the interference pattern can be transferred to the casting surface 41. UV lasers can be used, for example, as the first laser 70 and the second laser 71.

[0048] During the irradiation of the casting surface 41 with the laser radiation 72, the casting surface 41 is heated. Here, the casting surface 41 is locally heated. The interference pattern determines the local heating of the casting material 40. Wherever the maximum interference exists, a local ablation process will occur at the casting surface 41, which means that the casting material 40 will be heated in such a way that a sudden evaporation process occurs. As a result, the casting material 40 can be locally eroded, which means that a part of the casting material 40 at the casting surface 41 is removed. In this way, periodic structures can be created at the casting surface 41, which exhibit a periodicity corresponding to the interference pattern of the laser radiation 72. These periodic structures form a topography of the casting surface 41 that is suitable for dispersedly scattering incident electromagnetic radiation. Specular reflection of the electromagnetic radiation at the casting surface 41 is thereby suppressed.

[0049] In an alternative variant of the method for manufacturing the optoelectronic component 10, a portion of the casting material 40 at the casting surface 41 is removed by means of blasting with a combination of compressed air or water and a solid abrasive. This method may also be referred to as spraying or wet spraying. The solid abrasive may be, for example, sand. In the compressed air or water spraying, the abrasive is accelerated by means of a nozzle and directed at the casting surface 41. The abrasive removes a portion of the casting material 40 at the casting surface, thereby leaving uneven portions 100 at the casting surface 41. These uneven portions 100 form a topography of the casting surface 41 that is suitable for dispersedly scattering incident electromagnetic radiation. As a result, specular reflection of the electromagnetic radiation at the casting surface 41 can be suppressed. Figures 1 to 4 Compared to the method illustrated in FIG, a rougher casting surface 41 can be created with the aid of compressed air or water spraying.

[0050] In addition to spraying with compressed air or water combined with solid abrasives or by using Figures 1 to 4 In addition to the unevenness 100 produced by removing a portion of the casting material 40 at the casting surface 41 by one of the methods shown in , the particles 80 may also be exposed when a portion of the casting material 40 is removed at the casting surface 41. This may also result in the unevenness 100 at the casting surface 41. In addition, when a portion of the casting material 40 is removed at the casting surface 41, the particles 80 may be released from the casting material 40. This leaves further depressions and unevennesses 100 in the casting surface 41, which are configured to dispersely scatter the incident electromagnetic radiation, thereby suppressing the specular reflection of the incident electromagnetic radiation at the casting surface 41.

[0051] Figure 5 Shows that according to Figures 1 to 4 Schematic side view of an optoelectronic component 10 manufactured by one of the methods shown in . It has an unevenness 100 created by removing a portion of the casting material 40 at the casting surface 41. Particles 80 that have been exposed or released at the casting surface 41 can also create unevenness 100 in addition.

[0052] Figure 5 The optoelectronic component 10 shown in FIG. 4 is designed to dispersely scatter incident electromagnetic radiation at the casting surface 41. As a result, specular reflection of the electromagnetic radiation reaching the casting surface 41 is suppressed.

[0053] In addition to the fact that the removal of a portion of the casting material 40 at the casting surface 41 creates a topography at the casting surface 41 that is configured to dispersedly scatter electromagnetic radiation arriving from the outside, the topography created at the casting surface 41 can also be used to improve the extraction efficiency of the optoelectronic component 10. That is, the unevenness 100 created at the casting surface 41 can suppress the total internal reflection of the electromagnetic radiation emitted by the optoelectronic semiconductor chip 30 inside the casting surface 41. As a result, a larger proportion of the electromagnetic radiation emitted by the optoelectronic semiconductor chip 30 can be emitted from the optoelectronic component 10 at the casting surface 41. This can be achieved if the unevenness 100 is formed as a microstructure with a structural size, for example, in the range of more than 1 μm. The unevenness 100 can also be formed to improve the extraction efficiency of the optoelectronic component 10, because Fresnel reflections at the casting surface 41 are avoided. "Fresnel reflection" refers to the reflection of electromagnetic radiation at the boundary surface that conforms to the Fresnel formula. Fresnel reflection can be avoided because the unevenness 100 is formed as a submicron structure or a nanostructure, whose structure size is less than, for example, 1 μm, in particular, whose structure size is in the range of 100 nm to 400 nm. The casting surface 41 may also include an unevenness 100 for suppressing total internal reflection and an unevenness 100 for suppressing Fresnel reflection. For example, this can be achieved by generating two interference patterns with different periodicities in a two-stage process when structuring the casting surface 41 by laser interference. A microstructure can be applied to the casting surface 41 by means of a first interference pattern. A submicrostructure or a nanostructure covering the microstructure can be applied to the casting surface 41 by means of a second interference pattern.

[0054] In order to improve the outcoupling of light, microstructures with a periodicity between 1 μm and 100 μm are generated, and an aspect ratio between height and width between 0.5 and 1.5 is generated. Here, the microstructure should have a gradient distribution range that is as wide as possible. Therefore, the microstructure should be curved, for example, formed in the shape of a hemispherical microlens. The microstructure can also be covered by other structures with other periodicities. The microstructure can, for example, have a sinusoidal modulation. In order to keep the proportion of flat surface area as small as possible at the casting surface 41, the microstructure can, for example, be arranged hexagonally. Alternatively, the microstructure can, for example, be formed as a cross-shaped structure or randomly distributed with a certain overlap.

[0055] In addition to laser interference structuring, which allows the production of microstructures with lateral structure dimensions of less than about 15 μm, direct write laser methods (DLW, direct laser writing) can also be used as methods. This allows the production of microstructures with lateral structure dimensions of up to 100 µm.

[0056] The method for manufacturing the optoelectronic component 10 is not limited to individual optoelectronic components 10. For example, a two-dimensional composite of a plurality of optoelectronic components 10, such as an LED array, may also be provided with unevenness 100, which is generated simultaneously on a plurality of casting surfaces 41. Individual optoelectronic components 10 may also be manufactured by cutting the composite into small pieces. As a result, it is not necessary to generate the unevenness 100 on each individual optoelectronic component 10.

[0057] The present invention has been described and illustrated in more detail with reference to preferred exemplary embodiments. However, the present invention is not limited to the disclosed examples. Instead, those skilled in the art may derive different variations therefrom without departing from the scope of protection of the present invention.

[0058] Reference numerals list

[0059] 10 Optoelectronic components

[0060] 20 Carrier

[0061] 21 Upper side of carrier

[0062] 22 For electrical connection of optoelectronic semiconductor chips

[0063] 23 Cavity

[0064] 24 wall

[0065] 25 Upper edge of wall

[0066] 30 Optoelectronic semiconductor chips

[0067] 31 Top side of optoelectronic semiconductor chip

[0068] 32 Underside of optoelectronic semiconductor chip

[0069] 40 Casting materials

[0070] 41 Casting surface

[0071] 42 Fragments of casting material

[0072] 43 Other compounds

[0073] 50 Nozzles

[0074] 51 Etching agent

[0075] 52 Container for etchant

[0076] 60 ions

[0077] 70 First Laser

[0078] 71 Second Laser

[0079] 72 Laser radiation

[0080] 80 pcs

[0081] 90 wavelength conversion fluorescent material

[0082] 100 Uneven part.

Claims

1. A method for producing an optoelectronic component (10), comprising the following method steps: - providing a carrier (20) having an upper side (21); - an optoelectronic semiconductor chip (30) is arranged on the upper side (21) of the carrier (20); - a casting material (40) is arranged above the upper side (21) of the carrier (20), wherein the optoelectronic semiconductor chip (30) is embedded in the casting material (40), wherein the casting material (40) forms a casting surface (41); - removing a portion of the casting material (40) at the casting surface (41), wherein a topography is generated at the casting surface (41), wherein the removal of a portion of the casting material (40) at the casting surface (41) is performed by laser interference structuring, wherein an interference pattern is generated at the casting surface (41) and a local ablation process takes place at the casting surface (41) wherever an interference maximum exists, where two interference patterns with different periodicities are generated in a two-stage process, wherein a microstructure is applied to the casting surface (41) by means of a first interference pattern, In this case, a submicrostructure or nanostructure overlying the microstructure is applied to the casting surface (41) by means of a second interference pattern.

2. The method according to claim 1, The following method steps are performed before removing a portion of the casting material (40) at the casting surface (41): - Hardening of the casting material (40).

3. The method according to claim 1, The casting material (40) includes embedded particles (80).

4. The method according to claim 3, The particles (80) are exposed by removing a portion of the casting material (40) at the casting surface (41).

5. The method according to claim 3, Wherein particles (80) are released from the casting material (40) when a portion of the casting material (40) at the casting surface (41) is removed.

6. The method according to claim 1, The casting material (40) includes a wavelength conversion fluorescent material (90).

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