Method of manufacturing an augmented LED array assembly

Abstract

A method of manufacturing an augmented LED array assembly is described which comprises providing an LED array assembly configured for inclusion in an LED lighting circuit, the LED array assembly comprising a micro-LED array mounted onto a driver integrated circuit, the driver integrated circuit comprising contact pads configured for electrical connections to a circuit board assembly; providing an essentially planar carrier comprising a plurality of contact bridges, each contact bridge extending between a first contact pad and a second contact pad; and mounting the contact bridge carrier to the LED array assembly by forming solder bonds between the first contact pads of the contact bridge carrier and the contact pads of the driver integrated circuit.

Claims

1. A method of manufacturing an augmented LED array assembly comprising: providing an LED array assembly, the LED array assembly comprising a micro-LED array mounted onto a driver integrated circuit, the driver integrated circuit comprising a plurality of driver integrated circuit contact pads on a top surface of the driver integrated circuit; providing a flexible printed circuit board (PCB) comprising a bottom surface, a plurality of first contact pads on the bottom surface, a plurality of second contact pads on the bottom surface, and a plurality of contact bridges, each of the plurality of contact bridges extending between one of the plurality of first contact pads and one of the plurality of second contact pads; and mounting the flexible PCB to the LED array assembly by forming solder bonds between the plurality of first contact pads of the flexible PCB and the driver integrated circuit contact pads.

2. The method according to claim 1, wherein the solder bonds are formed in a reflow soldering process.

3. The method according to claim 1, further comprising applying underfill about the solder bonds at the driver integrated circuit contact pads.

4. The method according to claim 1, wherein the solder bonds are formed in a diffusion soldering process.

5. A method of manufacturing an LED lighting circuit comprising: providing an augmented LED array assembly that comprises: an LED array assembly comprising a micro-LED array mounted on a driver integrated circuit (IC), the driver IC comprising driver IC contact pads on a top surface of the driver IC, and a flexible printed circuit board (PCB) comprising a bottom surface, a plurality of first contact pads on the bottom surface, a plurality of second contact pads on the bottom surface, and a plurality of contact bridges, each of the plurality of contact bridges extending from one of the plurality of first contact pads to one of the plurality of second contact pads, each of the plurality of driver IC contact pads being bonded to a corresponding one of the plurality of first contact pads of the flexible PCB; providing a circuit board assembly comprising a circuit board mounted onto a heat spreader and comprising circuit board assembly contact pads; mounting the augmented LED array assembly to the heat spreader; and bonding the plurality of second contact pads of the flexible PCB to the circuit board assembly contact pads.

6. The method according to claim 5, wherein mounting the augmented LED array assembly to the heat spreader is preceded by applying a thermally-conductive adhesive layer to a mounting surface of the heat spreader.

7. The method according to claim 6, wherein mounting the augmented LED array assembly to the heat spreader is followed by curing the thermally-conductive adhesive layer.

8. The method according to claim 5, wherein bonding the second contact pads of the contact bridge carrier to the contact pads of the circuit board assembly is performed by hot bar soldering.

9. An augmented LED array assembly comprising: an LED array assembly comprising a micro-LED array mounted on a driver integrated circuit (IC), the driver integrated circuit comprising driver IC contact pads on a top surface of the driver IC; and a flexible printed circuit board (PCB) comprising a bottom surface, a plurality of first contact pads on the bottom surface, a plurality of second contact pads on the bottom surface, and a plurality of contact bridges, each of the plurality of contact bridges extending from one of the plurality of first contact pads to one of the plurality of second contact pads; and each of the plurality of driver IC contact pads being bonded to a corresponding one of the plurality of first contact pads of the flexible PCB.

10. The augmented LED array assembly according to claim 9, wherein the flexible PCB comprises a multi-layer flexible substrate.

11. The augmented LED array assembly according to claim 9, wherein: the micro-LED array has an emission face, and an upper face of the flexible PCB is not higher than the emission face of the micro-LED array.

12. The augmented LED array assembly according to claim 9, further comprising a plurality of passive circuit components on the flexible PCB.

13. The augmented LED array assembly according to claim 9, wherein the flexible PCB further comprises conductive tracks for additional switching circuitry.

14. The augmented LED array assembly according to claim 13, further comprising a plurality of switching circuit components the flexible PCB.

15. An LED lighting circuit comprising: a circuit board assembly comprising a circuit board on a heat spreader and circuit board assembly contact pads; an augmented LED array assembly that comprises: an LED array assembly comprising a micro-LED array mounted on a driver integrated circuit (IC), the driver integrated circuit comprising driver IC contact pads on a top surface of the driver IC, and a flexible printed circuit board (PCB) comprising a bottom surface, a plurality of first contact pads on the bottom surface, a plurality of second contact pads on the bottom surface, and a plurality of contact bridges, each of the plurality of contact bridges extending from one of the plurality of first contact pads to one of the plurality of second contact pads, each of the plurality of driver IC contact pads being bonded to a corresponding one of the plurality of first contact pads of the flexible PCB and each of the circuit board assembly contact pads being bonded to a corresponding one of the plurality of second contact pads of the flexible PCB; and a thermal bond between the driver integrated circuit of the augmented LED array assembly and the heat spreader of the circuit board assembly.

16. The LED lighting circuit according to claim 15, wherein: the circuit board includes an aperture, and the heat spreader comprises a raised seat extending upward into the aperture and configured to receive the LED array assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross-section through an embodiment of an augmented LED array assembly;

(2) FIG. 2 shows a cross-section through a contact bridge carrier of an augmented LED array assembly;

(3) FIG. 3 shows a plan view of an embodiment of an augmented LED array assembly;

(4) FIG. 4 shows a plan view of a further embodiment of an augmented LED array assembly;

(5) FIG. 5 shows a cross-section through an embodiment of an LED lighting circuit;

(6) FIG. 6 shows a prior art LED lighting circuit.

(7) In the drawings, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) FIG. 1 shows an embodiment of an augmented LED array assembly 1, and shows an LED array assembly 10, 11 configured for inclusion in an LED lighting circuit. The LED array assembly 10, 11 comprises a micro-LED array 10 mounted onto a driver integrated circuit 11. FIG. 2 illustrates a manufacturing stage of the augmented LED array assembly 1, and shows a flexible contact bridge carrier 12 relative to one side of the driver IC 11. The driver integrated circuit 11 has contact pads 11C (some of these can be seen in FIG. 2) such as gold bumps of a ball grid array (BGA) which serve to electrically connect the driver IC 11 to external circuitry.

(9) The diagrams show an essentially planar flexible carrier 12 with a plurality of contact bridges 120 realised as a thin flexible PCB 12 with contact bridges 120 in its interior. A contact bridge 120 extends between a first “inner” contact pad 120C_a and a second “outer” contact pad 120C_b. The outer layers of the flex PCB 12 can be a suitable material such as polyimide, for example. The contact pads 120C_a, 120C_b can be made by depositing or printing copper or any other suitable metal.

(10) Each contact pad 11C of the driver integrated circuit 11 is soldered or bonded to an inner contact pad 120C_a of the planar carrier 12 to achieve a permanent bond 1B as shown in FIG. 1, which also indicates underfill 16 applied to the solder bond 1B in order to prevent damage to the electrical connection 1B during handling of the assembly 1. The diagram also shows that the upper face 12F of the contact bridge carrier (12 is no higher than the emission face 10F of the micro-LED array 10.

(11) FIG. 3 shows a plan view of an embodiment of an augmented LED array assembly 1. In this very simplified exemplary embodiment, the planar carrier comprises four sections arranged along the four sides of the LED array assembly, and each carrier section 12 can connect one quarter of the driver contacts to a circuit board assembly. A number of contact pads 120C_a, 120C_b and contact bridges 120 are indicated by the broken lines on the right-hand carrier section 12.

(12) FIG. 4 shows a plan view of a further embodiment of an augmented LED array assembly 1. In this very simplified exemplary embodiment, the planar carrier has the form of a square “collar” and extends about the four sides of the LED array assembly. The outer perimeter of the driver IC 11 is indicated by the dotted line.

(13) FIG. 5 shows an embodiment of a LED lighting circuit 3 at a manufacturing stage, and shows a circuit board assembly 2 with a circuit board 20 mounted onto a heat spreader 21. The circuit board 20 has contact pads 20C configured for electrical connections to the driver IC 11 of the LED array assembly. The diagram shows an embodiment of an augmented LED array assembly 1, after forming a thermal bond 13 between the driver integrated circuit 11 and the heat spreader 21 of the circuit board assembly 2. In this embodiment, the heat spreader 21 is shaped to have a raised seat 210 configured to receive the driver IC 11. On the left-hand side of the diagram, the outer or second contact pad 120C_b of the flexible carrier 12 is about to be soldered to a corresponding contact pad 20C of the PCB 20. To this end, a hot bar soldering tool will press the flexible carrier 12 towards the PCB 20, while applying heat. The combination of heat and pressure will bond the second contact pad 120C_b to the PBC contact pad 20C. On the right-hand side of the diagram, the outer or second contact pad 120C_b of the flexible carrier 12 has already been soldered to a corresponding contact pad 20C of the PCB 20. The flexibility of the carrier 12 makes it easy to form the bonds, and also allows a considerable difference in height to be overcome.

(14) FIG. 6 shows a prior art LED lighting circuit 6, with a driver IC 11 mounted on a heat sink 61 arranged in an aperture of a circuit board 20. Here, wire bonds 60 are used to connect the contact pads 20C of the circuit board 20 to contact pads 11C of the driver IC 11. This type of assembly can be expensive when the driver IC 11 has a many contact pads 11C, for example 200 contact pads 11C requiring 200 wire bonds 60.

(15) Although the disclosure describes embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the claims.

(16) For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.