WO2010133772A1 - A light source element and a method for manufacturing - Google Patents

A light source element and a method for manufacturing Download PDF

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Publication number
WO2010133772A1
WO2010133772A1 PCT/FI2010/050411 FI2010050411W WO2010133772A1 WO 2010133772 A1 WO2010133772 A1 WO 2010133772A1 FI 2010050411 W FI2010050411 W FI 2010050411W WO 2010133772 A1 WO2010133772 A1 WO 2010133772A1
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WO
WIPO (PCT)
Prior art keywords
light
light source
light emitting
source element
lenses
Prior art date
Application number
PCT/FI2010/050411
Other languages
French (fr)
Inventor
Vladislav V. Bougrov
Maxim A. Odnoblyudov
Original Assignee
Cjsc Optogan
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Publication date
Application filed by Cjsc Optogan filed Critical Cjsc Optogan
Publication of WO2010133772A1 publication Critical patent/WO2010133772A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
    • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48225—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
    • H01L2224/48227—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/52—Encapsulations
    • H01L33/54—Encapsulations having a particular shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/58—Optical field-shaping elements

Definitions

  • the present invention relates to light sources utilis- ing light emitting semiconductor devices, particularly light emitting diodes LEDs as the primary light generating elements.
  • the present invention also relates to manufacturing of such light sources.
  • any light source like a luminary, producing said kind of light beam there is a primary light generating element.
  • incandescent and gas-discharge lamps have formed the great majority of all primary light generating ele- ments particularly in the applications with less critical requirements for the light beam properties and the overall luminous efficiency and the long-term stability thereof.
  • those types of light generating elements suffer from several shortcomings including e.g. short lifetime, high service costs, ecology-related problems e.g. due to the presence of mercury in the gas-discharge lamps, difficulties in smooth regulation of the luminous efficiency and dynamical switching.
  • the defi- ciencies in the ecology-related and energy consumption issues have been under critical discussion for a long time.
  • a light source appa- ratus In addition to the primary light generating element and the energy supply equipment, a light source appa- ratus most often also necessitates some optics to redistribute, i.e. to collect and re-direct the initially generated light energy according to the desired directivity diagram of the light source. At a general level, this is common for all light sources irrespec- tive of the type of the primary light generating element. However, naturally the practical level details vary a lot due to the entirely different properties of the light generating element e.g. between an incandescent lamp and a LED. In general, two main aspects can be identified in the required redistribution of the light. First, proper scattering of the light is important to achieve uniform lighting conditions particularly in indoor living or work rooms.
  • light concentration along one or several princi- pal axes is important for external lighting and special illuminating equipments and applications.
  • the light scattering issue involves a number of challenges in generating sufficiently intense and uniform illumination on the target area to be illuminated with the primary light generating element being placed within the eyeshot.
  • the short distance between the target area and the light generating element sets strong restrictions to the brightness of the light generating element, since the brightness and illumination non- uniformity can be reasons for discomfort and fatigability experienced by the persons staying in the illuminated area.
  • the brightness of a light generating element can be described e.g. by means of radiance L:
  • external optics is needed to shape the beam emitted by a semiconductor light emitting element, e.g. a LED chip.
  • a semiconductor light emitting element e.g. a LED chip.
  • a small standard-shaped lens is integrated into the LED package.
  • One typical way to perform this is to mount a beforehand fabricated lens on the LED chip by first dispensing silicone on the chip and then attaching the lens thereon. This one-by-one process, though performed by fully automatic processing apparatus, is rather time-consuming and expensive.
  • silicone liquid molding has introduced as a more straightforward way to form and attach a lens on an LED chip.
  • a special mold containing an array of cavities each having the shape of the desired lens geometry is first installed in the molding machine. Then, liquid silicone is introduced in the cavities while pressing the mold on a carrier on which the LED chips are attached. The silicone is then possibly cured. Finally, as a result of the molding process, there is a lens on each of the LED chips.
  • HB LEDs high-brightness LEDs
  • RI con- trolled refractive index
  • thermo-opto- mechanical properties include their high transparency in the UV-visible region, con- trolled refractive index (RI), and stable thermo-opto- mechanical properties.
  • some secondary light source optics is needed to shape the combined light beam, consisting of the light beams of the individual LEDs, according to the desired beam shape and divergence.
  • the light emitting chip has to be connected to an electric power supply
  • the optical construction should be optimized for maximized light extraction with minimal losses caused by multiple light reflections and internal absorption within the optical medium; particularly in consumer applications, minimizing the overall production costs of a LED-based luminary is crucial.
  • the prior art surface mount LED packages are usually based on a construction comprising a plastic housing and a lead frame attached thereto to supply electric power to the light emitting chip and conduct heat therefrom.
  • the actual LED chip is attached to the housing and connected to the lead frame via gold wires bonded on the contact pads of the chip.
  • the chip lies in a cavity of the housing, the cavity volume above the chip being filled with an optical encapsulation material comprising possibly phosphor based substance.
  • the overall dimensions and the accurate geometry of the chip vary between the different manufacturers and assembly types.
  • a basic element for a multi-LED light source is usu- ally formed by combining several such LED assemblies into a single integrated source unit.
  • the surface mount LED assemblies are soldered or otherwise attached onto a printed circuit board or some other carrier.
  • This carrier is further attached on a radiator element designed for effective heat transfer from the LED assemblies via the carrier to the ambient.
  • a lens is attached on top of each of the LED assemblies.
  • a glass protective cover possibly operating also as an additional lens, is arranged to cover the entire ele- ment .
  • the purpose of the present invention is to provide a novel and cost-effective light source element, and novel and cost-effective method for manufacturing such light source element.
  • the light source element and the manufacturing method of the present invention are characterized by what is presented in claims 1 and 6, respectively.
  • the light source element of the present invention has a predetermined light beam properties and it comprises a plurality of semiconductor light emitting devices as primary light generating elements thereof. Each of the semiconductor light emitting devices has a lens in connection therewith to modify the light output of the semiconductor light emitting device.
  • light source element is meant here a unit which as such is capable of producing said kind of predetermined light output beam. It can be a module to be incorporated in a final light source, like a luminary, or an inseparably integrated part of such device.
  • the light beam properties can be determined by means of the light beam characteristics like e.g. the shape, size, and directivity of the light beam produced by the light source element.
  • the predetermined light beam properties can be some standardized set of characteristics as such useful in many applications, or they can be determined especially for some particular application .
  • semiconductor light emitting device is meant here any device producing light primarily by means of ra- diative recombination of charge carriers in a structure formed of one or more semiconductor materials.
  • Typical examples of these kinds of devices are light emitting diodes LEDs and semiconductor lasers, the former being the most useful components for most lighting and illuminating applications.
  • the semiconductor devices are usually manufactured as an array of a great number of components formed on one single substrate wafer. Finally, the wafer including completed components is divided into separate chips of individ- ual components. This is the meaning of the word "chip” in this document. Naturally, a plain semiconductor chip is not as such a working device but necessitates external energy supply as well as proper packaging protecting the chip as well as e.g.
  • the light generated within a semiconductor device is extracted out of the chip via one or more sides of it.
  • the characteristics of the extracted light beam are determined mainly on the chip internal structure and are as such usually not suitable for further purposes. For this reason, a lens is needed to modify the output.
  • the lenses of the different semiconductor light emitting devices can be separate ele- ments. On the other hand, they can also form an integrated single body, the separate lenses being implemented as different portions thereof.
  • the lenses are configured to produce modified light outputs of the semiconductor light emitting devices so as to together form a combination of the modified light outputs of the semiconductor light emitting devices according to the predetermined light beam properties of the light source element.
  • each of the lenses is configured so that the combination of the modified light outputs of the individual semiconductor light emitting devices is in accordance with the predetermined light beam properties of the entire light source element.
  • lens configuration is meant here the set of parameters defining the optical performance of the lens. These include the material, shape, and location of the lens with respect to the light emitting device.
  • the present invention utilizes a single-level optics approach. Only one lens stage is needed. This greatly simplifies the structure and thus decreases the costs of the element.
  • the different lenses are configured to together form the final output of the light source element, they can be seen as a single optics module modifying the output of a light generating element comprising several discrete emitting areas/points.
  • the lenses or the entire optics module with the required optical performance can be designed by normal optical engineering using known design principles, e.g. by means of some commercial optics design software.
  • the chip of each of the semiconductor light emitting devices lies directly on a common substrate, and the lens in connection therewith is in the form of a solid structure lying directly on the common substrate, thus encapsulating the chip.
  • the common substrate can be e.g. a printed circuit board.
  • direct lying on a substrate is meant that the chip itself is mounted directly on the substrate without any sub-mount.
  • LED chips are usually sold as packaged within an assembly forming a mechanical housing as well as the electrical connections of the chip.
  • This embodiment of the present invention takes another approach in that it utilizes the LED chips as such, i.e. without any intermediate packaging. This again simplifies the manufacturing and, as a consequence thereof, decreases the costs of a semiconductor chip based light source element.
  • the necessary protective encapsulation of the chip is implemented as the solid lens structure also lying directly on the common substrate and encapsulating the chip.
  • this kind of encapsulation in addition to performing the desired optical function, also effectively protects the chip against mechanical and chemical stresses.
  • At least two of the lenses form an integrated single body.
  • the lenses of different light emitting devices are implemented as inseparable portions of a single lens unit body. This simplifies the light source element configuration and also enables denser packaging of the light emitting device chips on the common substrate.
  • a preferred group of materials of which the lenses can be formed is formed by the different transparent polymer compounds, particularly the ones comprising silicone composi- tions. These kinds of materials enable high performance optical components with reasonably low costs. These materials, particularly the silicones, possess high transparency over a wide wavelength range and very stable optical, thermal and mechanical proper- ties. Besides, they can be applied initially in liquid form and cured thereafter, which enables very efficient mass-production of the lenses by molding. Naturally, a lens being formed of a transparent polymer compound can also include other substances as well.
  • the present invention is focused on a method for manufacturing a light source element producing an output light beam with predetermined light beam properties.
  • the method com- prises a step of forming a light emitting assembly comprising a plurality of semiconductor light emitting devices and, for each of the semiconductor light emit- ting devices, a lens in connection with the semiconductor light emitting device to modify the light output thereof.
  • the method comprises the steps of:
  • the lenses can be designed and fabricated as truly separate objects but also as an integrated op- tics module.
  • one lens can be designed to receive and guide light also from more than one semiconductor light emitting devices.
  • the key feature in the method according to the present invention is the design and manufacturing the lenses not separately and individually or as standard-form components but so that each of them properly contrib- ute to the final light output of the entire light source element.
  • each semiconductor device-lens pair forms, particularly from the operation point of view, an integral portion of the entire light source element.
  • the first stage of the optical system is designed according to the de- sired source element performance. This approach enables substantially one-stage optical system.
  • a protective glass cover can be needed but its optical performance is practically of no significance .
  • the desired light beam properties can be determined according to some standard set of properties as such useful in many different applications. They can also be determined according to the specific needs of some particular illuminating or lighting application. Relevant parameters in this kind of determination can include e.g. the size, shape, divergence, and directivity diagram of the output light beam.
  • the lenses can be designed according to the well established design principles and using e.g. some suitable optics design software. As is clear for a person skilled in the art, a lens performance depends on e.g. the optical properties of the lens material, the shape of the lens surfaces and the distance between the light generating element which is here the semiconductor light emitting device.
  • the chip of each of the semiconductor light emitting devices is attached directly on a common substrate, and the lens in connection therewith is formed as a solid structure directly on the common substrate so as to encapsulate the chip.
  • the common substrate means that the chips and the lenses are attached on a same single substrate.
  • a bare chip means that no pre- liminary mount is used but the chips substantially as such are attached directly on the substrate. As described in the above, this removes unnecessary manufacturing steps and parts and thus greatly simplifies the manufacturing leading thus also decrease costs thereof.
  • Direct attaching does not exclude adhesives or other necessary layers or elements between the chips and the substrate. The same applies to fabrication and mounting of the lenses. In attaching the chips on the substrate, processes and apparatuses known e.g. from electronics industry can be utilized.
  • At least two of the lenses are formed as an integrated single body. Combining several lenses into a single lens unit body simplifies the manufacturing and lowers the costs thereof .
  • the lens is formed by sup- plying a transparent polymer compound, preferably silicone, on the common substrate, preferably initially in liquid state.
  • a liquid form substance enables use of molding which, for its turn, can be performed by efficient mass- production molding processes.
  • the liquid form lens material can be inserted into a mold which is then brought together with the common substrate having the semiconductor light emitting device chips thereon. After curing then the lens preforms by heat or e.g. ul- traviolet radiation, the mold can be removed.
  • the fabrication and mounting of the lenses are carried out not separately but in a single process. Molding can be performed as a high volume process where lenses or optics modules for a great number of light source elements are fabricated at the same time. Silicone molding is a well estab- lished technological field, thus no detailed description of the process details is needed here.
  • the liquid form lens substance can be applied onto the common substrate also by suitably modified printing process. Different variations of printing techniques can further increase the productivity and cost-efficiency of the manufacturing process .
  • Figure 1 shows a typical prior art LED assem- bly
  • FIGS. 2 and 3 illustrate prior art LED- based light source elements
  • Figures 4 and 5 illustrate examples of LED- based light source element according to the present invention
  • Figure 6 shows a flow chart illustrating one embodiment of the manufacturing process according to the present invention
  • Figures 7 and 8 illustrate further examples of LED-based light source element according to the present invention.
  • the LED assembly 1 of Figure 1 LED comprises a lead frame 2, which is used to supply electric power to the actual LED chip 3 and also conduct excess heat out of the assembly.
  • the lead frame is connected to the chip by gold wires 4 bonded to contact pads on the chip.
  • the chip lies in a hollow 5 formed within a plastic housing 6 forming the body of the assembly.
  • the hollow is filled with some encapsulating material comprising typically also phosphor to convert the wavelengths of the light initially generated in the chip to white light.
  • LED assemblies 1 are attached on a printed circuit board (PCB) 8 which is further mounted on a radiator 9 optimized for transferring heat from the light source element to the ambient.
  • PCB printed circuit board
  • Each LED assembly has a pri- mary lens 10 mounted in front of it to collect and redirect the light extracted from the LED assembly.
  • a protective glass cover 11 is adjusted to close the entire light source unit. Due to standardized optical performance of the primary lenses, also the glass cover is configured to have a particular optical performance in order to get the combined output from the source element according to the desired optical performance.
  • a third optical stage can be implemented, comprising one or more lenses outside the light source element to perform the final shaping of the light beam thereby produced.
  • Figure 3 shows a variation of the basic configuration of Figure 2.
  • the radiator 9 has a surface with facets directed in different directions in order to increase the divergence of the combined light output from the light source element. In other words, optical performance is adjusted by means of more complicated mechanics of the light source element.
  • each of the LED chips has its own PCB carrier.
  • the prior art configurations illustrated in Figures 1 - 3 have several deficiencies and limitations. First, some elements in the source elements perform the same function twice. As an example, electrical connection between the LED chip and the PCB is implemented as a two-stage configuration. First, the LED chip 3 is connected to the lead frame 2 by the bonding wires 4. The lead frame is further connected to the PCB 8 via soldered joints.
  • the light source element 12 of Figure 4 illustrates the unique approach of the present invention.
  • the LED chips 3 are attached directly on a PCB 8 and connected thereto by bonded gold wires 4.
  • the PCB is further attached on a radiator 9 similar to that of Figures 2 and 3.
  • a small volume of a phosphor-containing material 13 encloses the chip to perform the white light conversion.
  • Solid lenses 14 formed of silicone lies on the PCB tightly enclosing the chips. The geometries of the phosphor-containing material volume and the lens are adjusted to perform an optical function so that the combined outputs of the different LEDs in the light source element together produce a light output of the light source element according to predetermined output beam properties.
  • the light source element of Figure 4 provides several essential advantages over the prior examples of Figures 1 - 3.
  • the entire manufacturing process of the light source can be performed more straightforward and with less discrete steps.
  • the total number of separate parts is decreased.
  • the combination of the phosphor-containing material volume and the silicone lens thereon together performs as well the encapsulation of the chips as the optical function required.
  • the encapsulation of the chip was performed by the encapsulating material in the hollow if the LED assembly housing.
  • the optical function for its turn, was implemented by the standard-form LED lenses and the protective glass cover.
  • the protective glass cover can be of a standard type because it is not needed in the optical performance of the source.
  • the possible effect thereof on the optical performance needs to be, however, taken into account in the lens design.
  • the con- figuration includes less reflective material interfaces, and both the electrical and heat conduction paths are simpler with less interfaces than is the case in the prior art approaches.
  • Figure 5 shows how also adjusting the divergence of the light output from the light source element is simpler in the present invention than with the prior art solutions. Adjusting the alignment of the optical axes 15 of the LEDs can be performed simply by the geometry and positioning of the lenses.
  • the carrier plate 16 to which the LED chips 3 as well as the lenses are attached is drawn with a different shading than the PCB in the other Figures to highlight the fact that a PCB is just one example of possible substrates .
  • the manufacturing process illustrated in Figure 6 starts by determining the desired light output properties of the light source element and designing then the lenses of the LEDs according to these properties.
  • the actual manufacturing then begins by attaching LED chips 3 on a single carrier plate, e.g. a PCB 8 (step A in the figure) . Attaching can be performed according any known method, e.g. by means of some adhesive first applied on the PCB and then placing the chips thereon. Next, electrical connections between the chips and the carrier are made using e.g. gold wire 4 bonding (step B) . Small volumes of phosphor-containing material 13 are then brought on the LED chips 3 (step C) .
  • a mould 17 comprising hollows according to the designed lens geometries and the positioning of the chips on the carrier is prepared (step D) .
  • the hollows are filled with liquid silicone 18, after which the mould and the carrier plate having the chips thereon are brought together (step E) .
  • the silicone is then cured, after which the mold can be separated.
  • LED chips 3 are tightly encapsulated within the solid lenses, i.e. without any gaps therebetween (step F) .
  • the absence of air gaps between the chip and the lens is a feature enhancing, for its part, the light extraction from the chip.
  • figures 7 - 8 illustrate another approach where lenses 14 of several LED chips 3 are implemented as inseparable portions of an integrated lens unit.
  • An integrated lens unit enables effective light collection from several LED chips with decreased lens material consumption. It also allows denser packaging of the chips on the carrier plate 16.
  • Figure 8 illustrates an example where the principle of an integrated lens unit is utilized to form an elongated lens structure over an array of LED chips. This kind of arrangement produces an elongated output light pattern.
  • the desired light source directivity diagram can be achieved in a more effective way than with the use of separate lenses for each of the chips.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Led Device Packages (AREA)

Abstract

A light source element (12) for producing an output light beam with predetermined light beam properties comprises a plurality of semiconductor light emitting devices (3), each semiconductor light emitting device having a lens (14) in connection therewith to modify the light output of the semiconductor light emitting device. According to the present invention, the lenses (14) are configured to produce modified light outputs of the semiconductor light emitting devices so as to together form a combination of the modified light out- puts of the semiconductor light emitting devices ac- cording to the predetermined light beam properties of the light source element.

Description

A LIGHT SOURCE ELEMENT AND A METHOD FOR MANUFACTURING
FIELD OF THE INVENTION
The present invention relates to light sources utilis- ing light emitting semiconductor devices, particularly light emitting diodes LEDs as the primary light generating elements. The present invention also relates to manufacturing of such light sources.
BACKGROUND OF THE INVENTION
There exists a huge variation of different types of illumination and lighting applications where a light source with a specified output light beam shape and divergence is needed. The need for particularly deter- mined light beam properties concerns as well the general indoor lighting in different kinds of buildings as e.g. the specific automotive applications with very accurately specified output beam properties.
Naturally, in the core of any light source, like a luminary, producing said kind of light beam there is a primary light generating element. Conventionally, incandescent and gas-discharge lamps have formed the great majority of all primary light generating ele- ments particularly in the applications with less critical requirements for the light beam properties and the overall luminous efficiency and the long-term stability thereof. However, as well known, those types of light generating elements suffer from several shortcomings including e.g. short lifetime, high service costs, ecology-related problems e.g. due to the presence of mercury in the gas-discharge lamps, difficulties in smooth regulation of the luminous efficiency and dynamical switching. Particularly the defi- ciencies in the ecology-related and energy consumption issues have been under critical discussion for a long time. For example, it is known that as much a 15 to 20 % of the total electrical energy produced is consumed in lighting. To further continue by improving the conventional technologies in order to overcome the prob- lems involved therein would necessitate enormous efforts. To summarize, it can be stated that these technologies have practically come to their end. Actually, regulation haven been already adopted in some economical areas concerning e.g. gradual prohibition of the use of incandescent lamps.
At the moment, the semiconductor light emitting devices like LEDs are clearly seen as the most promising alternatives for the future lighting. There is already a great variety of different LED-based solutions commercially available for different applications.
In addition to the primary light generating element and the energy supply equipment, a light source appa- ratus most often also necessitates some optics to redistribute, i.e. to collect and re-direct the initially generated light energy according to the desired directivity diagram of the light source. At a general level, this is common for all light sources irrespec- tive of the type of the primary light generating element. However, naturally the practical level details vary a lot due to the entirely different properties of the light generating element e.g. between an incandescent lamp and a LED. In general, two main aspects can be identified in the required redistribution of the light. First, proper scattering of the light is important to achieve uniform lighting conditions particularly in indoor living or work rooms. On the other hand, light concentration along one or several princi- pal axes is important for external lighting and special illuminating equipments and applications. The light scattering issue involves a number of challenges in generating sufficiently intense and uniform illumination on the target area to be illuminated with the primary light generating element being placed within the eyeshot. Particularly in indoor lighting applications, the short distance between the target area and the light generating element sets strong restrictions to the brightness of the light generating element, since the brightness and illumination non- uniformity can be reasons for discomfort and fatigability experienced by the persons staying in the illuminated area. The brightness of a light generating element can be described e.g. by means of radiance L:
S ωS wherein I is radiant intensity of the light source, 5 is the area of the light emitting surface of the light generating element, Φ is radiant flux from the light source, and CO is the solid angle of the emitted light beam. It follows from this formula that the brightness of the light generating element depends not only on the surface area but also on the magnitude of the solid angle of the spreading light flux. In comparison with the incandescent and gas-discharge lamps, semiconductor elements possess much smaller emitting sur- face area and deliver their light flux in a solid angle smaller than a half of the conventional elements. Thus, in production of semiconductor based luminaries, it is necessary to enlarge the area of the light dif- fuser in comparison to the incandescent and gas- discharge sources. This leads to enlargement of the overall dimensions of the lighting device, complicates the manufacturing process, and raises additional costs, which together tend to annul the advantages gained from e.g. the lower energy of the semiconductor sources. Therefore, cost-effective solutions for achieving a uniform radiant intensity emitted by semiconductor-based light emitting elements like LEDs are needed.
On the other hand, in the case of illuminating remote objects the main challenge often lies in difficulties in achieving uniform illumination intensity. It follows from the equation for the irradiance E, a measure of the illumination strength, of the surface element,
„ /cosα
that the magnitude of the illumination diminishes with the distance R from the light source and increasing of angle of sight CC for the incoming light beam. Light spreading in larger solid angles leads to the considerable optical losses that causes increased energy consumption .
In order to achieve the desired output performance taking into account the aspects discussed above, external optics is needed to shape the beam emitted by a semiconductor light emitting element, e.g. a LED chip. Usually a small standard-shaped lens is integrated into the LED package. One typical way to perform this is to mount a beforehand fabricated lens on the LED chip by first dispensing silicone on the chip and then attaching the lens thereon. This one-by-one process, though performed by fully automatic processing apparatus, is rather time-consuming and expensive.
As a further development, silicone liquid molding has introduced as a more straightforward way to form and attach a lens on an LED chip. In liquid silicone molding, a special mold containing an array of cavities each having the shape of the desired lens geometry is first installed in the molding machine. Then, liquid silicone is introduced in the cavities while pressing the mold on a carrier on which the LED chips are attached. The silicone is then possibly cured. Finally, as a result of the molding process, there is a lens on each of the LED chips.
The key attributes of silicones that make them attractive materials for high-brightness (HB) LEDs include their high transparency in the UV-visible region, con- trolled refractive index (RI), and stable thermo-opto- mechanical properties.
Particularly in the cases where more than one LED chips is needed in a light source to produce the light power needed, also some secondary light source optics is needed to shape the combined light beam, consisting of the light beams of the individual LEDs, according to the desired beam shape and divergence.
Today there are a number of commonly used constructions aimed to simplify the LED-based light source assembly, the most of them being compatible with surface mounting processes. Common for the different approaches is that in addition to the desired optical performance as such, also the following aspects need to be properly taken into account:
- the light emitting chip has to be connected to an electric power supply;
- it is necessary to ensure effective heat transfer from the chip to the substrate in order to prevent overheating of the semiconductor device; the optical construction should be optimized for maximized light extraction with minimal losses caused by multiple light reflections and internal absorption within the optical medium; particularly in consumer applications, minimizing the overall production costs of a LED-based luminary is crucial.
The prior art surface mount LED packages are usually based on a construction comprising a plastic housing and a lead frame attached thereto to supply electric power to the light emitting chip and conduct heat therefrom. The actual LED chip is attached to the housing and connected to the lead frame via gold wires bonded on the contact pads of the chip. The chip lies in a cavity of the housing, the cavity volume above the chip being filled with an optical encapsulation material comprising possibly phosphor based substance. The overall dimensions and the accurate geometry of the chip vary between the different manufacturers and assembly types.
A basic element for a multi-LED light source is usu- ally formed by combining several such LED assemblies into a single integrated source unit. The surface mount LED assemblies are soldered or otherwise attached onto a printed circuit board or some other carrier. This carrier is further attached on a radiator element designed for effective heat transfer from the LED assemblies via the carrier to the ambient. A lens is attached on top of each of the LED assemblies. A glass protective cover, possibly operating also as an additional lens, is arranged to cover the entire ele- ment .
The common approach described in the above possesses several deficiencies. Some elements of the constructions duplicate each other in the sense that the nec- essary functions are performed twice. For example, electrical connections to the chip are implemented by a two-stage configuration by first connecting the chip to the lead frame and then further the lead frame to the PCB. Corresponding situation concerns the heat conduction path between the chip and the ambient. This kind of approach complicates the device and manufac- turing thereof and increases the costs. The presence of bolt-on lenses for each LED also raises the costs and diminishes effective light extraction due to the presence of additional reflective interfaces. In general, this technology is based on first manufacturing separate LED modules and then incorporating them into a light source element.
To summarize, to avoid the excess steps and components needed to complete a light source element and thus also to diminish the costs thereof, new solutions for semiconductor light emitting device-based lighting device manufacturing are needed.
PURPOSE OF THE INVENTION The purpose of the present invention is to provide a novel and cost-effective light source element, and novel and cost-effective method for manufacturing such light source element.
SUMN[ARY OF THE INVENTION
The light source element and the manufacturing method of the present invention are characterized by what is presented in claims 1 and 6, respectively.
The light source element of the present invention has a predetermined light beam properties and it comprises a plurality of semiconductor light emitting devices as primary light generating elements thereof. Each of the semiconductor light emitting devices has a lens in connection therewith to modify the light output of the semiconductor light emitting device.
By light source element is meant here a unit which as such is capable of producing said kind of predetermined light output beam. It can be a module to be incorporated in a final light source, like a luminary, or an inseparably integrated part of such device. The light beam properties can be determined by means of the light beam characteristics like e.g. the shape, size, and directivity of the light beam produced by the light source element. The predetermined light beam properties can be some standardized set of characteristics as such useful in many applications, or they can be determined especially for some particular application .
By semiconductor light emitting device is meant here any device producing light primarily by means of ra- diative recombination of charge carriers in a structure formed of one or more semiconductor materials. Typical examples of these kinds of devices are light emitting diodes LEDs and semiconductor lasers, the former being the most useful components for most lighting and illuminating applications. The semiconductor devices are usually manufactured as an array of a great number of components formed on one single substrate wafer. Finally, the wafer including completed components is divided into separate chips of individ- ual components. This is the meaning of the word "chip" in this document. Naturally, a plain semiconductor chip is not as such a working device but necessitates external energy supply as well as proper packaging protecting the chip as well as e.g. providing heat transfer path out from the chip. Initially, the light generated within a semiconductor device is extracted out of the chip via one or more sides of it. The characteristics of the extracted light beam are determined mainly on the chip internal structure and are as such usually not suitable for further purposes. For this reason, a lens is needed to modify the output. The lenses of the different semiconductor light emitting devices can be separate ele- ments. On the other hand, they can also form an integrated single body, the separate lenses being implemented as different portions thereof.
According to the present invention, the lenses are configured to produce modified light outputs of the semiconductor light emitting devices so as to together form a combination of the modified light outputs of the semiconductor light emitting devices according to the predetermined light beam properties of the light source element.
In other words, each of the lenses is configured so that the combination of the modified light outputs of the individual semiconductor light emitting devices is in accordance with the predetermined light beam properties of the entire light source element. In practice this means in most cases, though not necessarily, that each of the lenses have individual configuration and thus optical performance. By lens configuration is meant here the set of parameters defining the optical performance of the lens. These include the material, shape, and location of the lens with respect to the light emitting device. Instead the conventional solution using first standard primary lenses to prelimi- narily modify the output of the light generating chips and then converting these individual modified beams into the final combined output, the present invention utilizes a single-level optics approach. Only one lens stage is needed. This greatly simplifies the structure and thus decreases the costs of the element. In the sense that the different lenses are configured to together form the final output of the light source element, they can be seen as a single optics module modifying the output of a light generating element comprising several discrete emitting areas/points. The lenses or the entire optics module with the required optical performance can be designed by normal optical engineering using known design principles, e.g. by means of some commercial optics design software.
Preferably, the chip of each of the semiconductor light emitting devices lies directly on a common substrate, and the lens in connection therewith is in the form of a solid structure lying directly on the common substrate, thus encapsulating the chip. The common substrate can be e.g. a printed circuit board. By direct lying on a substrate is meant that the chip itself is mounted directly on the substrate without any sub-mount. E.g. LED chips are usually sold as packaged within an assembly forming a mechanical housing as well as the electrical connections of the chip. This embodiment of the present invention takes another approach in that it utilizes the LED chips as such, i.e. without any intermediate packaging. This again simplifies the manufacturing and, as a consequence thereof, decreases the costs of a semiconductor chip based light source element. Besides, heat transfer out of the chip is facilitated when there is a direct contact between the chip and the substrate. In this embodiment, the necessary protective encapsulation of the chip is implemented as the solid lens structure also lying directly on the common substrate and encapsulating the chip. With suitably selected material (s) , this kind of encapsulation, in addition to performing the desired optical function, also effectively protects the chip against mechanical and chemical stresses.
In one preferred embodiment, at least two of the lenses, possibly all of them, form an integrated single body. In other words, in this embodiment, instead of separate lens components, the lenses of different light emitting devices are implemented as inseparable portions of a single lens unit body. This simplifies the light source element configuration and also enables denser packaging of the light emitting device chips on the common substrate.
A preferred group of materials of which the lenses can be formed, particularly in the case of solid encapsulating lens structures on the common substrate, is formed by the different transparent polymer compounds, particularly the ones comprising silicone composi- tions. These kinds of materials enable high performance optical components with reasonably low costs. These materials, particularly the silicones, possess high transparency over a wide wavelength range and very stable optical, thermal and mechanical proper- ties. Besides, they can be applied initially in liquid form and cured thereafter, which enables very efficient mass-production of the lenses by molding. Naturally, a lens being formed of a transparent polymer compound can also include other substances as well.
According to the method aspect, the present invention is focused on a method for manufacturing a light source element producing an output light beam with predetermined light beam properties. The method com- prises a step of forming a light emitting assembly comprising a plurality of semiconductor light emitting devices and, for each of the semiconductor light emit- ting devices, a lens in connection with the semiconductor light emitting device to modify the light output thereof.
According to the present invention, the method comprises the steps of:
- determining the desired light beam properties of the output light beam of the light source element; - designing the lenses to produce modified light outputs of the semiconductor light emitting devices so as to together form a combination of the modified light outputs of the semiconductor light emitting devices ac- cording to the predetermined light beam properties of the light source element; and
- fabricating the lenses and mounting them to the light source element.
What is discussed above concerning the light source aspect of the present invention about the details of the light source element, semiconductor light emitting devices, lenses and the light output concerns respectively also the manufacturing method. The same applies vice versa concerning the disclosure below explaining the method according to the present invention and the embodiments thereof. For example, as stated in the above, the lenses can be designed and fabricated as truly separate objects but also as an integrated op- tics module. On the other hand, one lens can be designed to receive and guide light also from more than one semiconductor light emitting devices.
The key feature in the method according to the present invention is the design and manufacturing the lenses not separately and individually or as standard-form components but so that each of them properly contrib- ute to the final light output of the entire light source element. In other words, each semiconductor device-lens pair forms, particularly from the operation point of view, an integral portion of the entire light source element. Thus, in contrast to the conventional art solutions being based on standardized semiconductor device packages and standard-form primary lenses, in the present invention already the first stage of the optical system is designed according to the de- sired source element performance. This approach enables substantially one-stage optical system. Naturally, also a protective glass cover can be needed but its optical performance is practically of no significance .
The desired light beam properties can be determined according to some standard set of properties as such useful in many different applications. They can also be determined according to the specific needs of some particular illuminating or lighting application. Relevant parameters in this kind of determination can include e.g. the size, shape, divergence, and directivity diagram of the output light beam.
The lenses can be designed according to the well established design principles and using e.g. some suitable optics design software. As is clear for a person skilled in the art, a lens performance depends on e.g. the optical properties of the lens material, the shape of the lens surfaces and the distance between the light generating element which is here the semiconductor light emitting device.
Preferably, in the step of forming the light emitting assembly, the chip of each of the semiconductor light emitting devices is attached directly on a common substrate, and the lens in connection therewith is formed as a solid structure directly on the common substrate so as to encapsulate the chip. The common substrate means that the chips and the lenses are attached on a same single substrate. A bare chip means that no pre- liminary mount is used but the chips substantially as such are attached directly on the substrate. As described in the above, this removes unnecessary manufacturing steps and parts and thus greatly simplifies the manufacturing leading thus also decrease costs thereof. Direct attaching, however, does not exclude adhesives or other necessary layers or elements between the chips and the substrate. The same applies to fabrication and mounting of the lenses. In attaching the chips on the substrate, processes and apparatuses known e.g. from electronics industry can be utilized.
Preferably, in the step of fabricating the lenses and mounting them to the light source element, at least two of the lenses are formed as an integrated single body. Combining several lenses into a single lens unit body simplifies the manufacturing and lowers the costs thereof .
In a preferred embodiment, the lens is formed by sup- plying a transparent polymer compound, preferably silicone, on the common substrate, preferably initially in liquid state. As described in the above, a liquid form substance enables use of molding which, for its turn, can be performed by efficient mass- production molding processes. The liquid form lens material can be inserted into a mold which is then brought together with the common substrate having the semiconductor light emitting device chips thereon. After curing then the lens preforms by heat or e.g. ul- traviolet radiation, the mold can be removed. Thus, in this kind of process the fabrication and mounting of the lenses are carried out not separately but in a single process. Molding can be performed as a high volume process where lenses or optics modules for a great number of light source elements are fabricated at the same time. Silicone molding is a well estab- lished technological field, thus no detailed description of the process details is needed here.
Instead of molding, the liquid form lens substance can be applied onto the common substrate also by suitably modified printing process. Different variations of printing techniques can further increase the productivity and cost-efficiency of the manufacturing process .
BRIEF DESCRIPION OF THE FIGURES
The present invention and preferred embodiments thereof are described in more detail in the following by means of the attached drawings, wherein
Figure 1 shows a typical prior art LED assem- bly;
Figures 2 and 3 illustrate prior art LED- based light source elements;
Figures 4 and 5 illustrate examples of LED- based light source element according to the present invention;
Figure 6 shows a flow chart illustrating one embodiment of the manufacturing process according to the present invention; and Figures 7 and 8 illustrate further examples of LED-based light source element according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The LED assembly 1 of Figure 1 LED comprises a lead frame 2, which is used to supply electric power to the actual LED chip 3 and also conduct excess heat out of the assembly. The lead frame is connected to the chip by gold wires 4 bonded to contact pads on the chip. The chip lies in a hollow 5 formed within a plastic housing 6 forming the body of the assembly. The hollow is filled with some encapsulating material comprising typically also phosphor to convert the wavelengths of the light initially generated in the chip to white light.
In the multi-LED light source element 7 of Figure 2, LED assemblies 1 are attached on a printed circuit board (PCB) 8 which is further mounted on a radiator 9 optimized for transferring heat from the light source element to the ambient. Each LED assembly has a pri- mary lens 10 mounted in front of it to collect and redirect the light extracted from the LED assembly. A protective glass cover 11 is adjusted to close the entire light source unit. Due to standardized optical performance of the primary lenses, also the glass cover is configured to have a particular optical performance in order to get the combined output from the source element according to the desired optical performance. Alternatively, a third optical stage can be implemented, comprising one or more lenses outside the light source element to perform the final shaping of the light beam thereby produced.
Figure 3 shows a variation of the basic configuration of Figure 2. The radiator 9 has a surface with facets directed in different directions in order to increase the divergence of the combined light output from the light source element. In other words, optical performance is adjusted by means of more complicated mechanics of the light source element. Also, in this case, each of the LED chips has its own PCB carrier. The prior art configurations illustrated in Figures 1 - 3 have several deficiencies and limitations. First, some elements in the source elements perform the same function twice. As an example, electrical connection between the LED chip and the PCB is implemented as a two-stage configuration. First, the LED chip 3 is connected to the lead frame 2 by the bonding wires 4. The lead frame is further connected to the PCB 8 via soldered joints. There are several contact interfaces in- creasing the total resistance between the chip and the circuitry on the PCB. Similarly, heat transfer path from the chip to the ambient comprises several interfaces, thus possibly decreasing the overall heat conductance. The optical path from the chip to the ambi- ent has as many as six material interfaces, each of them causing reflectance losses. In addition to these problems, this approach also comprises unnecessarily many manufacturing steps and individual parts in the final light source element, the both increasing the manufacturing costs thereof.
The light source element 12 of Figure 4 illustrates the unique approach of the present invention. The LED chips 3 are attached directly on a PCB 8 and connected thereto by bonded gold wires 4. The PCB is further attached on a radiator 9 similar to that of Figures 2 and 3. Naturally, this is not the only possibility to implement the electrical connections needed but also e.g. a flip-chip geometry of the chip could be used. A small volume of a phosphor-containing material 13 encloses the chip to perform the white light conversion. Solid lenses 14 formed of silicone lies on the PCB tightly enclosing the chips. The geometries of the phosphor-containing material volume and the lens are adjusted to perform an optical function so that the combined outputs of the different LEDs in the light source element together produce a light output of the light source element according to predetermined output beam properties.
The light source element of Figure 4 provides several essential advantages over the prior examples of Figures 1 - 3. First, the entire manufacturing process of the light source can be performed more straightforward and with less discrete steps. When an intermediate packaging of the LED is not needed, the total number of separate parts is decreased. For example, the combination of the phosphor-containing material volume and the silicone lens thereon together performs as well the encapsulation of the chips as the optical function required. In the prior art examples above, the encapsulation of the chip was performed by the encapsulating material in the hollow if the LED assembly housing. The optical function, for its turn, was implemented by the standard-form LED lenses and the protective glass cover. In the light source element of Figure 4, the protective glass cover can be of a standard type because it is not needed in the optical performance of the source. Naturally, the possible effect thereof on the optical performance needs to be, however, taken into account in the lens design. The con- figuration includes less reflective material interfaces, and both the electrical and heat conduction paths are simpler with less interfaces than is the case in the prior art approaches.
Figure 5 shows how also adjusting the divergence of the light output from the light source element is simpler in the present invention than with the prior art solutions. Adjusting the alignment of the optical axes 15 of the LEDs can be performed simply by the geometry and positioning of the lenses. In Figure 5, the carrier plate 16 to which the LED chips 3 as well as the lenses are attached is drawn with a different shading than the PCB in the other Figures to highlight the fact that a PCB is just one example of possible substrates .
The manufacturing process illustrated in Figure 6 starts by determining the desired light output properties of the light source element and designing then the lenses of the LEDs according to these properties. The actual manufacturing then begins by attaching LED chips 3 on a single carrier plate, e.g. a PCB 8 (step A in the figure) . Attaching can be performed according any known method, e.g. by means of some adhesive first applied on the PCB and then placing the chips thereon. Next, electrical connections between the chips and the carrier are made using e.g. gold wire 4 bonding (step B) . Small volumes of phosphor-containing material 13 are then brought on the LED chips 3 (step C) . Meanwhile, a mould 17 comprising hollows according to the designed lens geometries and the positioning of the chips on the carrier is prepared (step D) . The hollows are filled with liquid silicone 18, after which the mould and the carrier plate having the chips thereon are brought together (step E) . The silicone is then cured, after which the mold can be separated. As a re- suit, LED chips 3 are tightly encapsulated within the solid lenses, i.e. without any gaps therebetween (step F) . The absence of air gaps between the chip and the lens is a feature enhancing, for its part, the light extraction from the chip.
In contrast to the individual and separate lenses for each of the LEDs in figures 4 - 6, figures 7 - 8 illustrate another approach where lenses 14 of several LED chips 3 are implemented as inseparable portions of an integrated lens unit. An integrated lens unit enables effective light collection from several LED chips with decreased lens material consumption. It also allows denser packaging of the chips on the carrier plate 16. Figure 8 illustrates an example where the principle of an integrated lens unit is utilized to form an elongated lens structure over an array of LED chips. This kind of arrangement produces an elongated output light pattern. In general, by varying the number of the chips covered by a single lens unit, the desired light source directivity diagram can be achieved in a more effective way than with the use of separate lenses for each of the chips.
It is to be noted that the embodiments of the present invention described above are just examples only. The present invention is no way limited to those examples. Instead, the embodiments can freely vary within the scope of the claims. Particularly, the drawings in the figures are not to be understood as technically valid and feasible designs but as purely illustrative schematic presentations only.

Claims

1. A light source element (12) for producing an output light beam with predetermined light beam properties, the light source element comprising a plurality of semiconductor light emitting devices (3) , each semiconductor light emitting device having a lens (14) in connection therewith to modify the light output of the semiconductor light emitting device, characteri zed in that the lenses (14) are configured to pro- duce modified light outputs of the semiconductor light emitting devices so as to together form a combination of the modified light outputs of the semiconductor light emitting devices according to the predetermined light beam properties of the light source element.
2. A light source element (12) according to claim 1, wherein the chip (3) of each of the semiconductor light emitting device lies directly on a common substrate (8, 16), and the lens (14) in connection therewith is in the form of a solid structure lying directly on the common substrate (8, 16), thus encapsulating the chip.
3. A light source element (12) according to claim 1 or 2, wherein at least two of the lenses form an integrated single body.
4. A light source element (12) according to any of claims 1 to 3, wherein the lenses (14) are formed of a transparent polymer compound.
5. A light source element (12) according to claim 4, wherein the transparent polymer compound comprises silicone .
6. A method for manufacturing a light source element (14) producing an output light beam with predetermined light beam properties, the method comprising a step of forming a light emitting assembly comprising a plural- ity of semiconductor light emitting devices (3) and, for each of the semiconductor light emitting devices, a lens (14) in connection with the semiconductor light emitting devices to modify the light output thereof, characteri zed in that the method comprises the steps of:
- determining the desired light beam properties of the output light beam of the light source element (12);
- designing the lenses (14) to produce modi- fied light outputs of the semiconductor light emitting devices (3) so as to together form a combination of the modified light outputs of the semiconductor light emitting devices according to the predetermined light beam prop- erties of the light source element; and fabricating the lenses (14) and mounting them to the light source element (12) .
7. A method according to claim 6, wherein in the step of forming the light emitting assembly, the chip (3) of each of the semiconductor light emitting devices is attached directly on a common substrate (8, 16), and the lens (14) in connection therewith is formed as a solid structure directly on the common substrate (8, 16) so as to encapsulate the chip.
8. A method according to claim 6 or 7, wherein in the step of fabricating the lenses (14) and mounting them to the light source element (12), at least two of the lenses are formed as an integrated single body.
9. A method according to any of claims 6 to 8, wherein the step of fabricating and mounting the lenses (14) comprises supplying a transparent polymer compound on the common substrate, preferably initially in liquid state.
10. A method according to claim 9, wherein the transparent polymer compound comprises silicone.
11. A method according to claim 9 or 10, wherein the transparent polymer compound is supplied on the common substrate by printing.
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