MATRIX LIGHT SOURCE HAVING AN ADJUSTABLE ARCHITECTURE

Abstract

The invention relates to a matrix light source having a plurality of elementary light sources with a light-emitting semiconductor element and an integrated circuit which includes the control logic pertaining to the elementary light sources of the matrix. The architecture of the light source is adjustable in that during production the size of the integrated circuit can be adapted to house matrices of different sizes using a repeatable structure.

Claims

1. A matrix light source comprising an integrated circuit and a matrix array of electroluminescent semiconductor element-based elementary light sources, wherein the integrated circuit comprises at least one electronic circuit intended to drive the supply of electric power to the elementary light sources, and a reception area having a substrate and intended to receive said matrix array, characterized in that the integrated circuit comprises at least one part, including a part of the reception area and the electronic circuit, that is repeated at least once along a main axis.

2. The light source as claimed in claim 1, wherein the substrate of the reception area comprises at least part of the electronic circuit.

3. The light source as claimed in claim 2, wherein the elementary light sources are electrically connected to the electronic circuit by connections that are vertical with respect to the extent of the reception area.

4. The light source as claimed in claim 1, wherein the matrix array of elementary light sources consists of at least two separate matrix components.

5. The light source as claimed in claim 1, wherein the integrated circuit comprises at least one connection area adjacent to the reception area), the connection area being intended to connect the electronic circuit to at least one external component.

6. The light source as claimed in claim 5, wherein the connection area extends along at least one edge of the integrated circuit that follows the main axis.

7. The light source as claimed in claim 5, wherein the connection area comprises at least one through-aperture.

8. The light source as claimed in claim 5, wherein the connection area comprises a plurality of connection pads, the respective areas of which depend on the signals and/or the electric current intensities that they are intended to transmit.

9. The light source as claimed in claim 5, wherein the connection area comprises means for connection to an electricity source, the connection means being formed by a metal layer.

10. A lighting module for a motor vehicle, the module comprising a heat sink element, a printed circuit board and a matrix light source, wherein the matrix light source is as claimed in claim 1.

11. The lighting module as claimed in claim 10, wherein the substrate of the integrated circuit is in thermal contact with the heat sink element.

12. The lighting module as claimed in claim 10, wherein the matrix light source is electrically connected to the printed circuit board by way of at least one bridging connection.

13. The light source as claimed in claim 2, wherein the matrix array of elementary light sources consists of at least two separate matrix components.

14. The light source as claimed in claim 2, wherein the integrated circuit comprises at least one connection area adjacent to the reception area, the connection area being intended to connect the electronic circuit to at least one external component.

15. The light source as claimed in claim 6, wherein the connection area comprises at least one through-aperture.

16. The light source as claimed in claim 6, wherein the connection area comprises a plurality of connection pads, the respective areas of which depend on the signals and/or the electric current intensities that they are intended to transmit.

17. The light source as claimed in claim 6, wherein the connection area comprises means for connection to an electricity source, the connection means being formed by a metal layer.

18. A lighting module for a motor vehicle, the module comprising a heat sink element, a printed circuit board and a matrix light source, wherein the matrix light source is as claimed in claim 2.

19. The lighting module as claimed in claim 11, wherein the matrix light source is electrically connected to the printed circuit board by way of at least one bridging connection.

20. The light source as claimed in claim 3, wherein the matrix array of elementary light sources consists of at least two separate matrix components.

Description

[0037] Other features and advantages of the present invention will be better understood with the aid of the description of the examples and of the drawings, in which:

[0038] FIG. 1 schematically shows a plan view of a matrix light source according to one preferred embodiment of the invention;

[0039] FIG. 2 schematically shows a cross section of a matrix light source according to one preferred embodiment of the invention;

[0040] FIG. 3 schematically shows a plan view of an integrated circuit of a matrix light source according to one preferred embodiment of the invention.

[0041] Unless specified otherwise, technical features that are described in detail for one given embodiment may be combined with the technical features that are described in the context of other embodiments described by way of example and without limitation. Similar reference numerals will be used to describe similar concepts across various embodiments of the invention. For example, the references 100 and 200 denote two embodiments of a matrix light source according to the invention.

[0042] The description focuses on the elements and components of a motor vehicle that are linked directly to the aspects of the invention. Other well-known elements will not be described in detail or mentioned. For the example of a lighting module in accordance with aspects of the invention, this involves, for example and without limitation, optical elements such as optical lenses or reflectors, or various supports for keeping components in their intended locations.

[0043] The illustration in FIG. 1 shows a pixelated light source or matrix light source 100 according to one preferred embodiment of the invention. The light source 100 comprises an integrated circuit 110 as well as a matrix array 130 that comprises a plurality of electroluminescent element-based elementary light sources 131. The integrated circuit is preferably produced using the well-known CMOS (“complementary metal oxide semiconductor”) technology, and it comprises in particular at least one electronic circuit 120 intended to drive the supply of electric power to the elementary light sources 131. Without limitation, the electronic circuit 120 may for example comprise means for connection to an electricity source external to the matrix source, such as a battery or a converter capable of supplying an electric current of an intensity suitable for supplying power to the elementary light sources. The electronic circuit may furthermore comprise switch elements, formed for example by way of MOSFET field-effect transistors, which make it possible to selectively supply power to the elementary sources 131 individually or in groups, in accordance with received commands. To this end, the electronic circuit may comprise a circuit for receiving such a command, the command being generated by an entity external to the matrix source.

[0044] The integrated circuit 110 comprises a reception area 112 intended to house the matrix array 130. The reception area is preferably rectangular. The geometry of the integrated circuit 110 is particular in that at least part of its structure, including the reception area and the electronic circuit that is integrated therein, is repeated at least once along a main axis 101.

[0045] In the illustration in FIG. 1, the part of the integrated circuit that is repeated is located between two dashed vertical lines. Each repetition of this structure is implemented using an identical mask during production of the integrated circuit through CMOS technology. The invention is obviously not limited to a single repetition of the structure. Depending on the size of the matrix array 130 that will be housed by the integrated circuit, the same mask may be used along the main axis 101 so as to extend the integrated circuit, in order to increase the number of addressable pixels of the matrix array 130. Since the electronic circuit 120 of each repeated part comprises the electronic components required to supply power to and control the elementary light sources 131 that are housed by the corresponding repeated part of the reception area 112, the architecture is adjustable in terms of size along the axis 101.

[0046] In the example shown, two matrix components 130′ and 130″ are used to form the matrix array 130. The matrix components are for example produced independently of one another.

[0047] FIG. 2 shows a cross section along the axis A-A indicated in FIG. 1. It shows the reception area 112, which is preferably formed by a rectangular recess in the substrate, generally made of silicon, Si, of the integrated circuit. This geometrical characteristic does not however limit the invention. The electronic circuit 120 comprises connections at the reception area 112, which make it possible in particular to make electrical contact with each of the elementary light sources 131 individually via their lower face, which is in contact with the substrate of the reception area 112. The vertical connection thus produced by elements embedded in the integrated circuit makes it possible to dispense with individual wiring for the elementary light sources.

[0048] The matrix light source 100 comprises a matrix array 130 of electroluminescent semiconductor element-based elementary light sources 131 and may comprise a common substrate, not illustrated, in mechanical and electrical contact with and functionally connected to the integrated circuit 120. The elementary light sources are typically light-emitting diodes (LEDs).

[0049] The matrix light source 100 preferably, but without limitation, comprises a monolithic matrix component, in which the semiconductor layers of the elementary light sources 131 are for example arranged on the common substrate. The matrix array of elementary light sources 130 preferably comprises a parallel assembly of a plurality of branches, each branch comprising electroluminescent semiconductor light sources 131.

[0050] By way of example and without limitation, the matrix array of elementary light sources 130 comprises, along the thickness of the substrate and starting at the end opposite the location of the elementary sources 310, a first electrically conductive layer deposited on an electrically insulating substrate. This is followed by an n-doped semiconductor layer whose thickness is between 0.1 and 2 μm. The following layer is the active quantum well layer having a thickness of around 30 nm, followed by an electron-blocking layer, and finally a p-doped semiconductor layer, the latter having a thickness of around 300 nm. Preferably, the first layer is an (Al)GaN:Si layer, the second layer is an n-GaN:Si layer, and the active layer comprises quantum wells made of InGaN alternating with barriers made of GaN. The blocking layer is preferably made of AlGaN:Mg and the p-doped layer is preferably made of p-GaN:Mg.

[0051] In order to achieve elementary light sources 131 having semiconductor layers having homogeneous thicknesses, the monolithic component is preferably manufactured by depositing the layers homogeneously and uniformly over at least part of the surface of the substrate so as to cover it. The layers are deposited for example using a metal oxide chemical vapor deposition (MOCVD) method. Such methods and reactors for implementing them are known for depositing semiconductor layers on a substrate, for example from patent documents WO 2010/072380 A1 or WO 01/46498 A1. Details on their implementation will therefore not be described in the context of the present invention. The layers thus formed are then pixelated. By way of example and without limitation, the layers are removed using known lithographic methods and by etching at the sites that subsequently correspond to the spaces between the elementary light sources 131 on the substrate. A plurality of several tens or hundreds or thousands of pixels 131 having a surface area smaller than one square millimeter for each individual pixel, and having a total surface area greater than 2 square millimeters, having semiconductor layers with homogeneous thicknesses, and therefore having homogeneous and high internal series resistances, are thus able to be produced on the substrate of a matrix light source. Generally speaking, the more the size of each LED pixel decreases, the more its series resistance increases, and the more this pixel is able to be driven by a voltage source. As an alternative, the substrate comprising the epitaxial layers covering at least part of the surface of the substrate is sawn or divided into elementary light sources, each of the elementary light sources having similar characteristics in terms of their internal series resistance.

[0052] The invention also relates to types of semiconductor element-based elementary light sources involving other configurations of semiconductor layers. In particular the substrates, the semiconductor materials of the layers, the arrangement of the layers, their thicknesses and any vias between the layers may be different from the example that has just been described.

[0053] The integrated circuit 110 is preferably soldered to the lower face of the matrix array, which houses the elementary light sources on its upper face, so as to establish mechanical and electrical contact with the substrate and the elementary light sources. Using an integrated circuit 110 in mechanical and electrical contact with the substrate on which the elementary light sources reside makes it possible to dispense with wired connections, the number of which would be at least equal to the number of pixels of the matrix light source. Preferably, a power supply circuit may be integrated into the substrate when the monolithic component is manufactured.

[0054] The illustration in FIG. 3 shows a pixelated light source or matrix light source 200 according to another preferred embodiment of the invention. The light source 200 comprises an integrated circuit 210 as well as a matrix array, not illustrated, that consists of a plurality of electroluminescent element-based elementary light sources. The integrated circuit is preferably produced using the well-known CMOS (“complementary metal oxide semiconductor”) technology, and it comprises in particular at least one electronic circuit intended to drive the supply of electric power to the elementary light sources. At least one connection area 213, 214 of the integrated circuit makes it possible to connect the electronic circuit to other external components. The connection area 213, 214 extends along an edge that follows the main axis of the integrated circuit. In the example in FIG. 2, connection areas 213, 214 are provided on the two opposite edges that follow the main axis.

[0055] The part 213 of the connection area makes it possible in particular to connect the matrix light source 200 to an external electricity source. The Si substrate of the integrated circuit is preferably soldered directly or adhesively bonded by way of a thermal adhesive to a heat sink element, for example consisting of an aluminum block. The connection area 213 makes it possible to connect the electronic circuits installed in the integrated circuit 210 to various electrical potentials Vin, Gnd, as well as preferably digital logic control signals via a direct bridging link to an external printed circuit board that houses the corresponding electrical sources. To this end, the connection area comprises dedicated connection pads. The pads Vin, Gnd may for example have a maximum area that makes it possible to transmit an electric current of high intensity, for example at least 15 A. Other connection pads provided for the transmission of digital commands may have smaller areas. The bridging links may therefore also be formed by way of wires or ribbons having suitable dimensions. Wires with a diameter of 50 or 125 μm may be used for digital signal transmission. For example, ribbons measuring 400×100 μm or a wire with a diameter of 200 μm may be used to transmit an intense electric current. The connection area may preferably comprise four connections capable of transmitting a high-intensity electric current, distributed over two edges of the integrated circuit.

[0056] The direct thermal link between the Si substrate of an integrated circuit and a heat sink element, as well as the direct bridging link to an external circuit, may also be applied to other types of integrated circuit that do not comprise the other features in accordance with the aspects of the present invention.

[0057] A bridging connection using the technique known as “wire bonding” or “ribbon bonding” or even “copper clip” is used for this purpose. This type of connection allows the transmission of high electric currents and the rapid transmission of logic signals. The connection comprises a connection pad on the printed circuit board and in the connection area 213 of the integrated circuit 210, and an electrically conductive wire that connects the two connection pads. Each connection pad is electrically connected to the electronic circuit of the respective printed circuit board/integrated circuit. The electrically conductive wire is soldered between the two connection pads, for example by ultrasonic soldering. The material of the wire is aluminum, gold, copper or silver, while its diameter is between 75 μm and 250 μm. According to one preferred embodiment, the connection pads comprise, at least on their surface, a layer of the same material of which the wire consists in order to facilitate the soldering step.

[0058] The connection areas 213, 214 preferably comprise a metal layer, the dimensions of which are suitable for conducting high-intensity electric currents, for example of more than 15 A. Specifically, the matrix source should be capable of managing intense electric currents, given the large number of elementary light sources that it may house.

[0059] The integrated circuit 210 furthermore comprises a reception area 212 adjacent to the connection area 213, 214 and intended to house the matrix array of elementary light sources. The reception area is preferably rectangular. The geometry of the integrated circuit 210 is particular in that at least part of its structure, including the reception area and the electronic circuit that is integrated therein, is repeated at least once along a main axis. In the illustration in FIG. 3, only the part of the integrated circuit that is repeated is shown, the repetitions not being illustrated. This structure is implemented using an identical mask during production of the integrated circuit through CMOS technology. The repetitions are advantageously implemented without any offset between the repeated structures, but some variants may be implemented with an offset, as long as the matrix function is not altered. Since the size of the integrated circuit 210 may become large depending on the number of repetitions of the modular pattern of the integrated circuit along the main axis, apertures, preferably through-apertures, or holes 215 may be provided at the connection area 213, 214 of the integrated circuit 210, in order to reduce the mechanical stresses therein. This measure in particular reduces the risk of the connection pads used in the bridging links becoming unstuck due to mechanical stresses in the substrate of the integrated circuit 210.

[0060] It goes without saying that the integrated circuit may comprise other electronic circuits and/or memory elements used for other functions in connection with the matrix light source and/or with the elementary light sources. This includes but is not limited to circuits for detecting a short circuit or an open circuit fault with an elementary light source.

[0061] The scope of protection is defined by the claims.