Assembly of light sources, motor vehicle lighting device comprising same and method for manufacturing such an assembly

Abstract

The invention relates to an assembly of light sources including an integrated circuit with a connection pad, a light-emitting part with micro-LEDs and an active surface, a fan-out encapsulation surrounding at least a part of the integrated circuit, a first multilayer metal layer, a second metal layer that includes contact parts being in direct contact with a rear face of the integrated circuit, a heat sink, a matrix fixation layer arranged between the second metal layer and the heat sink and a printed circuit board. The first metal layer is arranged so as to cover at least a part of the front face of the integrated circuit, providing an electrical connection between the pad of the integrated circuit and a pad of the assembly.

Claims

1. An assembly of light sources for a motor vehicle lighting device, the assembly comprising: an integrated circuit with a first side and a second side opposite the first side, with a first connection pad in the first side; a light-emitting part with a plurality of micro semiconductor light sources which are electrically connected to the first side of the integrated circuit and an active surface arranged so as to modify the wavelength of the micro semiconductor light sources; a fan-out packaging, surrounding at least part of the integrated circuit; a first multilayer metal layer arranged so as to cover at least part of the first side of the integrated circuit, providing an electrical connection between the first connection pad and a connection pad of the assembly; a second metal layer including contact portions which are in direct contact with the second side of the integrated circuit; a heat sink element; an array bonding layer arranged between the second metal layer and the heat sink element; and a printed circuit board.

2. The assembly of light sources as claimed in claim 1, wherein the second metal layer includes copper and a finish made of nickel, palladium and gold.

3. The assembly of light sources as claimed in claim 1, wherein the active surface is arranged in a plane that is parallel to the first and second sides of the integrated circuit.

4. The assembly of light sources as claimed in claim 1, wherein the second metal layer is parallel to the active surface.

5. The assembly of light sources as claimed in claim 1, wherein a distance between the connection pad of the assembly and the active surface is between 2 mm and 4 mm.

6. The assembly of light sources as claimed in claim 1, wherein the second side of the integrated circuit is partially covered by the fan-out packaging, and the second metal layer comprises metal projections which pass through the fan-out packaging to come into contact with the second side of the integrated circuit.

7. The assembly of light sources as claimed in claim 1, wherein the first multilayer metal layer includes at least one redistribution layer.

8. The assembly of light sources as claimed in claim 7, wherein the redistribution layer is arranged around the light-emitting part.

9. The assembly of light sources as claimed in claim 1, wherein the first multilayer metal layer includes a ribbon cable which connects the connection pad of the assembly to the printed circuit board.

10. The assembly of light sources as claimed in claim 1, wherein the first multilayer metal layer includes a via which passes through the fan-out packaging and connects the first connection pad to the connection pad of the assembly.

11. The assembly of light sources as claimed in claim 1, wherein the array bonding layer includes at least one element from among a silicone adhesive, a solder alloy, a silver sinter paste or metal fillers.

12. The assembly of light sources as claimed in claim 1, wherein the active layer is a phosphor coating comprising a silicone-based material and metal particles.

13. A motor vehicle lighting device, comprising: a plurality of assemblies of light sources, with each of the plurality of assemblies of light including: an integrated circuit with a first side and a second side opposite the first side, with a first connection pad in the first side; a light-emitting part with a plurality of micro semiconductor light sources which are electrically connected to the first side of the integrated circuit and an active surface arranged so as to modify the wavelength of the micro semiconductor light sources; a fan-out packaging, surrounding at least part of the integrated circuit; a first multilayer metal layer arranged so as to cover at least part of the first side of the integrated circuit, providing an electrical connection between the first connection pad and a connection pad of the assembly; a second metal layer including contact portions which are in direct contact with the second side of the integrated circuit; a heat sink element; an array bonding layer arranged between the second metal layer and the heat sink element; and a printed circuit board.

14. A method for producing an assembly of light sources, the method comprising: providing an initial integrated circuit carrier; selecting portions of the initial integrated circuit carrier that are suitable for the production of an assembly of light sources; placing appropriate portions of an adhesive tape to form a reconstructed carrier; placing interposers for electrical connection; selecting the portions of the reconstructed carrier that are suitable for packaging; grinding the rear face of the reconstructed carrier to define the thickness or to expose a silicon rear face; adding a second metal layer to the second face of the reconstructed carrier; adding a first multilayer metal layer to the first face of the reconstructed carrier to create a connection between each of a plurality of integrated circuit pads and each of a plurality of assembly pads; attaching a plurality of micro semiconductor light sources; and dicing the reconstructed carrier.

15. The method as claimed in claim 14, further comprising: reflowing process after attaching micro semiconductor light sources; underfilling deposition between the micro semiconductor light sources and the reconstructed carrier; performing treatments on the micro semiconductor light sources; and performing opto-electrical tests.

16. The method as claimed in claim 15, wherein the performing treatments includes performing a surface treatment.

17. The method as claimed in claim 15, wherein the performing treatments includes performing a thinning treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To supplement the description and to allow better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate one embodiment of the invention, which should not be interpreted as limiting the scope of the invention, but merely as an example of how the invention may be carried out. The drawings comprise the following figures:

(2) FIG. 1 shows a general approach of a first embodiment of an assembly of light sources according to the invention.

(3) FIG. 2 shows a general approach of a first embodiment of an assembly of light sources according to the invention.

(4) FIG. 3 shows a detail of the redistribution layers of one embodiment of an assembly of light sources according to the invention.

(5) FIG. 4 shows a detail of the contact projections between two layers of an assembly of light sources according to the invention.

(6) FIG. 5a, FIG. 5b, and FIG. 5c show the steps of a production method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) The exemplary embodiments are described in sufficient detail to allow those of ordinary skill in this art to carry out and implement the systems and processes described herein. It is important to understand that these examples may be provided in a number of different forms and should not be construed as being limited to the examples presented here.

(8) Consequently, although the embodiment may be modified in various ways and take various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below by way of example. No limitation to the particular forms disclosed is intended. Rather, all modifications, equivalents and alternatives falling within the scope of the appended claims are to be included. The elements of the exemplary embodiments are systematically denoted by the same reference numerals throughout the drawings and detailed description, where applicable.

(9) FIGS. 1 and 2 show a general approach of two embodiments of an assembly of light sources 1 according to the invention. FIG. 1 is oriented toward a submount connection, while FIG. 2 shows the incorporation intended to be connected via a connection defined by a solder mask (SMT).

(10) The assemblies 1 illustrated in FIGS. 1 and 2 comprise an integrated circuit 2, a light-emitting portion with micro LEDs 3 and an active surface 4, a fan-out packaging 5, a first metal multilayer 6, a second metal layer 8, a chip bonding layer 9, a heat sink 11 and a printed circuit board 12.

(11) The integrated circuit 2 is an ASIC with a first side 21 and a second side 22 opposite the first side 21 and comprises a pad 23 in the first side 21.

(12) The light-emitting portion comprises a plurality of micro LEDs 3 which are electrically connected to the first side 21 of the integrated circuit 2, so as to receive power and control. The active surface 4 is arranged so as to modify the wavelength of the micro LEDs 3, such that the final light emission is white, as required by motor vehicle functionalities.

(13) The fan-out packaging 5 is arranged so as to surround the integrated circuit 2. The fan-out assembly 5 is responsible for surrounding it laterally, but the second side 22 of the integrated circuit 2 is also protected by a small portion of the fan-out assembly 5.

(14) The first metal multilayer 6 is arranged so as to cover part of the first face 21 of the integrated circuit 2. As this first metal multilayer 6 is different in each variant, it will be described in more detail later. In all cases, this first metal multilayer 6 provides an electrical connection between the pad 23 of the integrated circuit 2 and the pad 7 of the assembly.

(15) The second metal layer 8 comprises metal projections 81 which pass through the fan-out packaging 5 so as to be in direct contact with the second side 22 of the integrated circuit 2. This second metal layer is made of copper and has a nickel finish.

(16) The array tie layer 9 is arranged between the second metal layer 8 and the heat sink 11, and its purpose is different for each embodiment.

(17) As can be seen in these two figures, the active surface 4 is arranged along a plane that is parallel to the first 21 and second 22 sides of the integrated circuit 2. This plane is also parallel to the second metal layer 8. This parallel arrangement is easier to design and manufacture, and also affords good structural robustness, such that these small pads are able to retain their shape despite the thermal and structural loads that they experience.

(18) Above the micro LEDs 3, the active layer 4 comprises a phosphor coating which is deposited by sputtering. This coating is a silicone-based material filled with metal particles to give a white color to the final projected light (since the LEDs emit in the blue wavelength). In some embodiments, this coating may also be spread over redistribution layers, to play a protective role and an additional role of releasing local stress. However, this layer does not reach the pads of the assembly 7, as it would be considered a contaminant for these elements. The additional area provided by the fan-out packaging 5 helps to avoid such contamination.

(19) FIG. 1 shows one embodiment of an assembly of light sources 1 which is particularly configured for use in a submount connection. The structure of the first metal multilayer is therefore different from that of FIG. 2.

(20) In this figure, the first metal multilayer comprises multiple redistribution layers 61 which provide the electrical connection between the pad 23 of the driver 2 and the pad 7 of the assembly which, in this embodiment, is located on the upper face of the assembly 1.

(21) The minimum distance between the pad 7 and the active surface 4 depends on the optical system chosen to be placed above the assembly of light sources, but may vary between 2 and 4 mm. This smaller distance contributes to simplifying the masking system which is placed above in order to avoid any directly incident light, such as due to optical reflection from the wire or ribbon 62.

(22) Thermal problems are also mitigated by the position of the redistribution layers 61, around the light-emitting portion.

(23) The tie layer 9 of this embodiment is intended to transfer thermal energy with the lowest possible resistance. A solder alloy paste with metal fillers is used so that the heat is easily dissipated toward the heat sink 11. In addition, this chip bonding layer 9 mechanically bonds the assembly of light sources 1 to the main structure of the lighting device, which is represented by the heat sink 11.

(24) FIG. 2 shows another embodiment of an assembly of light sources 1, which is particularly configured for use in a connection defined by a solder mask (SMT). The structure of the first metal multilayer is therefore different from that of FIG. 1.

(25) In this case, the first metal multilayer 6 comprises a conductive via 63 which passes through the fan-out packaging 5 connecting the pad of the driver 23 to the pad of the assembly 7, which in this case is located in the lower portion of the assembly 1.

(26) In this case, the connection pad 7 is connected to the printed circuit board 12 by means of a bonding layer 13. As this bonding layer 13 performs an electrical function, a solder alloy is used. In various embodiments, an electrically conductive adhesive, with or without sintering, may be used for this purpose.

(27) FIG. 3 shows a detail of the redistribution layers of one embodiment of an assembly of light sources according to the invention.

(28) The integrated circuit 2 comprises a passivation layer 64 which is deposited on the first face 21 of the integrated circuit. The passivation layer is not applied to the pad of the driver 23, which receives the first redistribution layer 61. This first redistribution layer 61 is deposited on a first polymer layer 71, while a second polymer layer 72 is deposited on top, leaving a space for the connection of a second redistribution layer 61. A third polymer layer 73 is deposited on this second redistribution layer 61, leaving an empty space for the third and last redistribution layer. This third redistribution layer provides the connection pad 7 of the assembly which is intended to be connected to the printed circuit board 12 by means of a ribbon cable 62, as shown in FIG. 1.

(29) The micro LEDs 3 are connected to the anodes 24 and to the cathodes 25 of the driver by means of a solder paste 13 which connects each anode and each cathode to the connection pads of the LEDs 31.

(30) FIG. 4 shows a detail of the contact protuberances between two layers of an assembly of light sources according to the invention.

(31) In this embodiment, the packaging 5 comprises a portion that covers the second side 22 of the integrated circuit 2, and the second metal layer 8 comprises metal projections 81 which pass through this portion of the packaging 5 so as to be in direct contact with the second side 22 of the integrated circuit 2. This second metal layer 8 is made of copper and has a nickel finish.

(32) FIGS. 5a to 5c show the steps of a production method according to the invention.

(33) FIG. 5a shows the provision of an initial carrier 101, where the integrated circuit of the future assembly is designed.

(34) This original wafer is tested to identify the appropriate portions. Next, the original wafer is diced and, according to FIG. 5b, the appropriate portions 102 are arranged on a tape, forming a reconstructed wafer 103.

(35) Various elements are added to this reconstructed carrier 103 to form a complete electronic assembly. First, interposers are added, in order to provide an electrical connection between the portions in good condition and the future substrate where the assembly will be connected.

(36) Next, the surface of the reconstructed carrier receives a packaging, in order to secure each portion of the carrier and to handle the reconstructed carrier as one piece. The reconstructed carrier is then ground to expose the silicon of the well-conditioned portions, so that the metal layers may be added. These metal layers make it possible to control deformation and to provide the electrical connections between the terminals of the integrated circuit and the terminals of the assembly. Once these layers have been added, the reconstructed carrier is ready to receive the LED population.

(37) The installation of the redistribution layers at an early stage in the process, independently of the final connection of the assembly, as a sub-assembly or SMD, makes the process easier and less expensive, since yield is improved, and the final assembly of the heat sink elements is also improved.

(38) FIG. 5c shows the final result of the reconstructed carrier 103 after having undergone the preceding steps. All of the required electronic elements are arranged so as to form an assembly of light sources according to the invention.

(39) Once the LEDs have been arranged in the reconstructed carrier, a reflow process takes place, followed by underfill deposition between the micro LEDs and the conductive portions. Next, the array of micro LEDs is treated and ready to be tested and isolated.

(40) The elements of the exemplary embodiments are systematically denoted by the same reference numerals throughout the drawings and detailed description, where applicable: 1 Assembly of light sources 2 Integrated circuit 21 First side of the integrated circuit 22 Second side of the integrated circuit 23 Pad of the integrated circuit 24 Anode 25 Cathode 3 Micro-LED 31 Micro-LED pad 4 Active surface 5 fan-out packaging 6 First multilayer metal layer 61 Redistribution layers 62 Wire 63 Polymer through-via 64 Passivation layer 7 Connection pad 71 First polymer 72 Second polymer 73 Third polymer 8 Second metal layer 81 Contact portions of the second metal layer 9 Tie layer 10 Motor vehicle lighting device 11 Heat sink 12 Printed circuit board 13 Intermediate thermal layer 101 Initial carrier 102 Appropriate portions 103 Reconstructed carrier