EP1875522A2

EP1875522A2 - Optical element, optoelectronic component comprising said element, and the production thereof

Info

Publication number: EP1875522A2
Application number: EP06742249A
Authority: EP
Inventors: Gertrud KRÄUTER; Andreas PLÖSSL
Original assignee: Osram Opto Semiconductors GmbH
Current assignee: Osram GmbH
Priority date: 2005-04-26
Filing date: 2006-04-18
Publication date: 2008-01-09
Also published as: CN102683561A; US20080224159A1; CN101164174A; CN102683561B; JP2008539567A; TW200702153A; DE102005036520A1; WO2006114082A2; WO2006114082A3; KR20080003768A; CN101164174B; TWI381935B

Abstract

The invention relates to an optical element (1, 25) having a defined shape and comprising a thermoplastic material that has been further cross-linked during or following the shaping thereof. Such thermoplastic materials have an increased heat distortion, but can be easily and economically shaped before the additional cross-linking as a result of the thermoplastic properties thereof.

Description

Optical component, optoelectronic component with the component and its manufacture

In Vergussmaterialen for optoelectronic devices, such Bei ^'Piel radial LEDs Smard LEDs or chip LEDs, housing materials for optoelectronic components such as SMT LEDs or optical components such as lenses, it is often required that the respective materials solder resistant are. That's why today are filled with glass fibers and / or minerals

Used high temperature plastics, which are very expensive and can be processed only with special injection molding at high temperatures. Thermosetting plastics such as epoxy polymers or silicones can be used for the encapsulations or optical components of optoelectronic components. However, these plastics are difficult to mold.

The aim of the present invention is therefore to provide an optical component which reduces the above-mentioned disadvantages.

This object is achieved according to the invention by an optical component according to claim 1. Further advantageous embodiments of the optical component and an optoelectronic component with the component and its production are the subject of further claims.

The invention relates to an optical component having a specific shape, comprising a thermoplastic which has been crosslinked during or after molding. The advantage of an optical component according to the invention is that a standard thermoplastic can be used which, due to its thermoplastic properties, has a flow transition range above its service temperature and is therefore particularly simple in the softened state, for example by pressing, extrusion, injection molding or injection compression molding and other shaping processes can be formed into an optical component. The thermoplastic is then crosslinked only during or after molding, resulting in a modified thermoplastic having increased temperature dimensional stability, a lower coefficient of thermal expansion, and improved mechanical performance. The inventors have surprisingly found that, despite the networking carried out subsequently optical components made of these crosslinked thermoplastics still have sufficiently good optical properties in order to use the components in optoelectronic systems can. Surprisingly, the optical components according to the invention which comprise the additionally crosslinked thermoplastics are also solder-stable, so that optoelectronic components which have these components can also be mounted particularly easily by means of soldering to substrates, for example printed circuit boards.

Depending on the application, optical components according to the invention can have any desired shapes. So they can z. B. be formed as a housing for the radiation-emitting semiconductor chips, as reflectors or as lenses. The optical components can thus be brought into any form that can be used for optoelectronic applications. Due to the thermoplastic properties, the shape, z. B. by means of injection molding particularly simple, wherein only during or after shaping the crosslinking takes place.

In a further embodiment of the invention, an optical component is understood to be a component that interacts with light, that is to say in particular light-shaping, light-guiding and / or light-transducing. Examples of optical components are z. As lenses that can focus the light and reflectors that reflect the light.

In one embodiment of the invention, it is possible that after molding the thermoplastic has been crosslinked by irradiation. Such irradiation for the crosslinking of the thermoplastic can be carried out, for example, by irradiation with beta or gamma rays. Such irradiations can be carried out, for example, in conventional electron accelerators and gamma systems. Due to the irradiation u. a. Radicals generated in the readily processable thermoplastics, which cause a further crosslinking of the thermoplastic polymer strands due to their reactivity, so that highly crosslinked three-dimensional polymer networks can arise.

In another embodiment of the invention, it is possible that during the shaping, for example during the extrusion, additional crosslinking takes place under high pressure by adding crosslinking agents. Such crosslinking agents may include, for example, organic peroxides, which may also provide for the chemical crosslinking of the thermoplastics. This can result in a uniform network of thermoplastic macromolecules. Crosslinking aids can also be used in the above-mentioned beam crosslinking to shorten the irradiation times and by-products of irradiation z. B. by fragmentation or oxidation to reduce.

Due to the networking occurring during or after the shaping of the optical component, it is possible according to the invention to use all previously unexpensive inexpensive engineering thermoplastics which can be processed, for example, at moderate temperatures by injection molding. The thermoplastics used in the optical components according to the invention may be selected from a group comprising the following plastics: polyamide, polyamide 6, polyamide 6,6, polyamide 6,12, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyphenylene oxide, polyoxymethylene, acrylonitrile butadiene Styrene copolymer, polymethyl methacrylate, modified polypropylene, ultrahigh molecular weight polyethylene, ethylene-styrene interpolymers, copolyester elastomers, thermoplastic urethane, polymethyl methacrylimide, cycloolefin copolymers, cycloolefin polymers, polystyrene and styrene-acrylonitrile copolymer.

The plastics mentioned can each be used alone or in any desired combinations in the production of optical components according to the invention.

By means of various thermal, physical and mechanical tests, it is possible to detect the property changes which occur during the subsequent crosslinking of thermoplastics. In this way it is possible to crosslink conventional non-crosslinked thermoplastics Thermoplastics to distinguish. For example, the incorporation of polar oxygen-containing groups on the surface of radiation-crosslinked thermoplastics can be detected by means of IR spectroscopy. U. a. Electron irradiation increases the surface tension of radiation cured thermoplastic materials, thereby increasing the polarity of the surface of the thermoplastics.

The increase in the glass transition temperature of additionally crosslinked thermoplastics can be detected, for example, by means of dilatometric, dielectric, dynamic-mechanical or refractometric measurements by DSC (differential scanning calorimetry) or by means of NMR spectroscopy, all of which are known to a person skilled in the art.

DMA torsion tests also provide direct information on the glass transition temperature T ₉ , the changed melt crystallization behavior and the temperature stability of the cross-linked thermoplastics. In the vicinity of the glass transition region, cross-linked thermoplastic materials up to the melting range are often stiffer than uncrosslinked thermoplastic materials with the consequence that cross-linked thermoplastics no longer flow, so that an improved temperature dimensional stability is ensured. Crosslinked thermoplastics often behave elastically in the melting area and do not flow anymore. The crosslinking further reduces the thermal expansion and the permeability to water and oxygen. Likewise, silver migration is restricted. - S -

Optical components according to the invention advantageously comprise a thermoplastic which is substantially transparent to radiation. In this case, the radiation can be emitted by all possible radiation sources, for example optoelectronic components, into which the optical component is integrated. Substantially transparent means that the thermoplastic has a transparency of about 70 to 80%, preferably up to 92%, for the radiation. The inventors have surprisingly found that crosslinked thermoplastics still have sufficiently transparent properties.

Furthermore, an inorganic coating may additionally be arranged on an optical component according to the invention. This can increase the mechanical resistance, soldering resistance and resistance to water penetration in addition to crosslinking. This inorganic coating may include, for example, materials selected from silica and titania. The coating may comprise only one of the materials or a combination of both materials. Such layers can be applied, for example, in a gas phase deposition process with layer thicknesses of about 50 nm to 1000 nm. Coatings with such layer thicknesses are additionally also largely transparent to radiation.

In a further embodiment, connecting elements can be formed from the thermoplastic material of an optical component according to the invention (see, for example, FIGS. 3 and 4). Such connecting elements can serve, for example, to connect optical components with optoelectronic radiation-emitting components. Optoelectronic components with these optical Components can then also be mounted on a substrate, for example a printed circuit board, in a particularly simple manner via further connecting elements made of the crosslinked thermoplastics (see, for example, FIG. 4). The connecting elements, such as pins, tabs, plugs or the like can be particularly easily formed from thermoplastic materials, since they are well meltable and therefore easily malleable. Only after or during the formation of these connecting elements, the thermoplastic materials of an optical component according to the invention are then further crosslinked, so that an increased stability results.

Optical components according to the invention can in this case comprise a lens or a reflector (see, for example, FIGS. 1 to 5). In the case of a lens, this can be glued onto an existing encapsulation of an optoelectronic component, this component then being solder resistant in spite of the thermoplastic (see, for example, FIG. 2). In the case of a reflector as an optical component, a thermoplastic material is preferably used which has a high reflectivity and is not transparent. Frequently, in this case, the thermoplastic still further additives, such as titanium dioxide (white pigment) is added. It is also possible to form housings of subsequently cross-linked thermoplastic material, which at the same time also have reflector properties (see, for example, Figures 1 and 2).

The invention further relates to an optoelectronic, radiation-emitting component with an optical component comprising a crosslinked thermoplastic. Such components often have similar good optical properties as components from previously used special high-temperature plastics, but are easier and cheaper to produce.

It is particularly advantageous if the optical component is formed as a housing, since in this way a particularly good soldering stability of a radiation-emitting component can be ensured. Due to its good optical properties, for example its good transparency, the optical component can also be arranged in the beam path of the component and is then substantially transparent to the emitted radiation (see, for example, FIG. 2).

Due to the increased temperature resistance and improved properties of crosslinked thermoplastic materials, it is particularly advantageous to attach a radiation-emitting component to a substrate via this material. This can be done, for example, by means of closure elements or soldering methods (see, for example, FIGS. 4 and 5).

The invention further provides a method for producing an optical component of a specific shape with the method steps:

A) providing a thermoplastic,

B) transferring the thermoplastic into the desired shape,

C) crosslinking of the thermoplastic, wherein the optical component is formed.

Advantageously, an injection molding process is used in process step B). Often, a crosslinking aid is additionally added before process step C). - S -

z. As triallyl isocyanurate (TAIC) added, which facilitates the crosslinking.

In the case of chemical crosslinking processes, it is possible, for example, to carry out process steps B) and C) together, using chemical crosslinkers such as, for example, organic peroxides.

In the case of radiation crosslinking, in method step C) the molded thermoplastic can be exposed to an irradiation dose of about 30 to 400 kGy, preferably 33 to 165 kGy, with electron beams.

In the following, the invention will be explained in more detail with reference to figures and embodiments.

embodiments

2-3 mm thick lenses with a diameter of 0.8 cm were sprayed from a polyamide (Grilamid TR 90), wherein triallyl isocyanurate (TAIC, Peralink 301) was added in liquid form to the plastic matrix as a crosslinking aid. The proportion of the added TAIC was 2-5 wt% _# preferably about 3 to 4 wt%. The addition was either directly as a liquid or adsorbed to a hollow granules. Calcium silicate was not used, as usual, as a carrier material for TAIC, since it adversely affects the transparency of the lenses. Subsequent cross-linking was by irradiation with beta rays at typically 66-132 kGy for a few seconds. Irradiation is sequential in 33 kGy increments. The irradiation takes place at least twice, but preferably four times with, for example, the same in each case Radiation doses. The lenses may have connecting elements for anchoring in the form of legs (see, for example, FIGS. 3 and 6).

Performing the injection molding with a purged with inert gas, z. B. N ₂ -purged granules in a N ₂ -purged injection molding machine through, you get crystal clear products. Radiation crosslinking leads to color centers, which lead to a yellowing of the pointed cast parts. This discoloration completely disappears when soldering at 260 ^° C. The soldered products are crystal clear with a transparency of 85-90%. Instead of N ₂ , other inert gases can be used, and the inventors have found that when using the inert gases, as described above, the discoloration occurring during radiation crosslinking is then reduced or completely disappears during soldering. Particularly advantageous is also during the beam crosslinking under inert gas, for. B. N ₂ worked. This can be z. B. done by packaging the optical components under inert gas in plastic bags and then networked.

The lenses of the radiation-crosslinked Grilamid TR 90 were, in contrast to lenses made of the uncrosslinked material solder-stable and had a transparency of about 70-95%, preferably 85-90%. In addition, the water absorption of the lenses of the crosslinked material was reduced so much that when blasting at a maximum temperature of 260 ⁰ C at 30s no blistering was observed.

Analogous to the above-mentioned radiation crosslinking of the lenses, housings of LEDs which comprise thermoplastics filled with white pigment can also be used, for example. B. produced by means of injection molding and radiation crosslinking the resulting housing then in contrast to the non-radiation crosslinked housings are solder resistant. In addition to the one shown in Fig. 1 -6 known to a person skilled in the art "TOP LEDs" can also be such. B. still the housing of so-called the expert also known "SMART LEDs", and "chip LEDs" are radiation crosslinked. "SMART LEDs" are described, for example, in the document DE 199 63 806 C2, which is hereby incorporated by reference, and have an LED with a leadframe which is encapsulated by a plastic molding compound in such a way that the LED is connected to its LED The plastic molding compound can still be mixed with a light conversion substance, in the case of "chip LEDs", LEDs are mounted on a PCB that has contacts for mounting and encapsulated by a plastic molding compound.

Figures 1 to 7 show various embodiments of radiation-emitting devices according to the invention with optical components of crosslinked thermoplastic materials in cross section and a radiation-crosslinked lens, which is suitable for installation in an optoelectronic device.

FIG. 1 shows, in cross-section, a radiation-emitting component 5A, in which a semiconductor component 5, e.g. B. an LED by means of a bonding wire 10 and a conductor strip 20 is electrically contacted. The semiconductor component 5 is located in a reflector trough which has a reflector surface 2 and which concentrates the light emitted by the semiconductor component. The reflector pan and the semiconductor component 5 located therein are of a casting 15, z. B. encompassing epoxy or silicone. The radiation-emitting component 5A has a housing 1 made of a radiation-cured or chemically crosslinked thermoplastic on, which has high reflectivity and from the same time the reflector surfaces 2 of the reflector trough are formed. In contrast to conventional radiation-emitting components, in which the housing 1 consists either of expensive high-temperature plastics or thermosetting plastics, radiation-emitting components according to the invention are cheaper and easier to produce due to the easy formability of the thermoplastics.

FIG. 2 shows a cross section of a further embodiment of a radiation-emitting component 5A according to the invention. In contrast to the component of FIG. 1, a lens 25 is additionally present, which is applied to the encapsulation 15 of the component. Such a lens 25 may also be particularly easily formed from a post-crosslinked thermoplastic material. Depending on the requirements of the component, the housing 1 may also include a thermoplastic material crosslinked according to the invention in the component of FIG. 2 or may comprise conventional high-temperature thermoplastics or thermosetting plastics. Since it is surprisingly also possible to produce subsequently crosslinked thermoplastic materials with sufficiently transparent properties, it is readily possible to arrange the lens 25 made of the subsequently crosslinked thermoplastic material in the beam path 60 of the component 5A.

FIG. 3 shows a further variant of a radiation-emitting component 5A according to the invention, in which a lens 25 is arranged on the casting 15, which likewise subsequently comprises radiation-crosslinked thermoplastic material and which additionally has connecting elements 30A. In this case, the connecting elements 30A consist of small feet it allow by means of a snap mechanism to anchor the feet in recesses 3OC of the housing 1 mechanically. In such an embodiment, it is no longer necessary, as usual, to fasten the lens 25, for example by gluing, on the casting 15 of the component 5A.

As an alternative or in addition to the exemplary embodiment of FIG. 3, connecting elements 3OB can also be formed in the housing 1, which additionally comprises crosslinked thermoplastic materials according to the invention, which allow an anchoring of the component 5A on a substrate 100, for example a printed circuit board, in a particularly simple manner. Also in this case, the fasteners 3OB are fixed in the form of feet by means of a snap mechanism in recesses 3OD of the substrate 100. Such fastening methods can replace, for example, conventional soldering methods and thus reduce or prevent thermal stress on the component.

Due to the additional temperature dimensional stability of additionally crosslinked thermoplastic materials, radiation-emitting components having the housings 1 made from these materials can also be attached to substrates 100 without major problems by means of soldering methods.

FIG. 5 shows in cross-section a further embodiment of the invention, in which both the lens 25 and the housing 1 comprise subsequently cross-linked thermoplastic materials. To increase the soldering resistance even further, to increase the barrier properties for water and to increase the mechanical stability, on both optical components, the lens 25 may be an inorganic one Coating 25A and be disposed on the housing 1, an inorganic coating IA. Such coatings, which may include, for example, materials selected from silica and titania, may be deposited, for example, by gas deposition processes having layer thicknesses of 50 nm to 1000 nm. The device is mounted by soldering through the solder 50 on the substrate 100.

FIG. 6 shows a component in which the lens 25 is placed on the housing 1 via fastening elements 25B. In contrast to the component shown in FIG. 3, the fastening elements 25 B comprise the housing 1.

FIG. 7 shows in FIGS. 7A and 7B perspective views of a possible embodiment of a lens 25 which, similar to that shown in FIG. 6, can be plugged onto a housing 1. In addition to the fastening elements 25B, pins 25C are also provided, which are inserted into corresponding recesses in the housing. Figure IC shows the lens 25 in cross section.

The invention presented here is not limited to the embodiments presented. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments. Further variations are possible above all with regard to the thermoplastic materials used as well as the shape and function of the optical components formed from these subsequently crosslinked thermoplastic materials.

Claims

claims

An optical component (1, 25) having a specific shape comprising a thermoplastic which has been crosslinked during or after molding.

2. An optical component (1, 25) according to the preceding claim, has been crosslinked in the after molding of the thermoplastic by means of irradiation.

3. An optical component (1, 25) according to claim 1, in which a crosslinking has taken place during the shaping by adding crosslinking agents.

4. An optical component (1, 25) according to any one of the preceding claims, wherein the thermoplastic is selected from a group comprising the following plastics: polyamide (PA), polyamide 6 (PA 6); Polyamide 6,6 (PA 6,6), polyamide 6, 12 (PA 6,12); Polybutylene terephthalate (PBT); Polyethylene terephthalate (PET); Polycarbonate (PC); Polyphenylene oxide (PPO); Polyoxymethylene (POM); Acrylonitrile-butadiene-styrene copolymer (ABS); Polymethyl methacrylate (PMMA); modified polypropylene (PP-modified); ultrahigh molecular weight polyethylene (PE-UHMW), ethylene-styrene interpolymers (ESI); Copolyester elastomers (COPE); thermoplastic urethane (TPU); Polyuriethylmethacrylimide (PMMI);

Cycloolefin copolymers (COC); Cycloolefin polymers (COP) polystyrene (PS) and styrene-acrylonitrile copolymer (SAN).

5. Optical component (1, 25) according to one of the preceding claims,

In which the thermoplastic is substantially transparent to radiation.

6. Optical component (1, 25) according to any one of the preceding claims, on which in addition an inorganic coating (IA, 25A) is arranged.

7. An optical device (1, 25) according to the preceding claim, wherein the inorganic coating (IA, 25A) comprises materials selected from: SiO ₂ and TiO ₂ .

8. An optical component (1, 25) according to any one of claims 6 or 7, wherein the coating has a layer thickness of 50 nm to 1000 nm.

9. Optical component (1, 25) according to one of the preceding ^f 'claims, in which in addition from the thermoplastic fasteners (3OA, 30B) are formed.

10. An optical component (25) according to any one of the preceding claims, comprising a lens.

11. An optical component (1) according to any one of claims 1 to 10, comprising a reflector.

12. Optoelectronic, strahlungsemittierend.es device (5A) with

- An optical component (1, 25) according to any one of the preceding claims.

13. Radiation-emitting component (5A) according to the preceding claim,

- Wherein the optical component (1, 25) is formed as a housing.

14. A radiation-emitting component (5A) according to any one of claims 12 or 13, wherein the optical component (1, 25) in the beam path (60) of the device (5A) is arranged and is substantially transparent to the emitted radiation.

15. Radiation-emitting component according to one of claims 12 to 14, wherein the entire component is encapsulated by the housing.

16. Arrangement of a radiation-emitting component (5A) according to one of claims 12 to 15 on a substrate (100),

- Wherein the component (5A) via the optical component (1, 25) on the substrate (100) is attached.

17. Arrangement according to the preceding claim, wherein the device (5A) by means of soldering on the substrate (100) is attached.

18. Method for producing an optical component (1, 25) of a specific shape with the method steps: A) providing a thermoplastic,

B) transferring the thermoplastic into the desired shape and,

C) crosslinking of the thermoplastic, wherein the optical component is formed.

19. Method according to the preceding claim, wherein an injection molding process is used in process step B).

20. The method according to any one of claims 17 to 19, wherein before the process step C) additionally a crosslinking aid is added.

21. The method according to any one of claims 18 to 20, wherein after step B) in step C), the molded thermoplastic is exposed to an irradiation dose of about 33 to 165 kGy with electron beams.

22. The method according to any one of claims 18 to 20,

- In which the process steps B) and C) are carried out together.

23. The method according to any one of claims 18 to 22, wherein a transparent thermoplastic is used.

24. The method according to any one of claims 18 to 23,

- In which the process step B), the transfer of the thermoplastic is carried out in the desired shape under inert gas.

25. The method according to any one of claims 18 to 24,

- In which the process step C) is carried out under inert gas.

26. The method according to any one of claims 18 to 25,

- In which in step C) of the molded thermoplastic is crosslinked at least twice by means of radiation.

27. Use of components of a particular shape comprising a thermoplastic which has been crosslinked during or after molding for optoelectronic devices.