Accurate alignment of an LED assembly
View Patent ↗An LED assembly includes a heat sink and a submount. The heat sink has a top mating surface that is solder wettable, and the submount has a bottom mating surface that is solder wettable. The top and the bottom mating surfaces have substantially the same shape and area. The submount is soldered atop the heat sink. During solder reflow, the molten solder causes the submount to align with the top mating surface of the heat sink. The LED assembly may further include a substrate having a top mating surface, and the heat sink may further include a bottom mating surface. The top and bottom mating surfaces have substantially the same shape and area. The heat sink is soldered atop the substrate. During solder reflow, the molten solder causes the heat sink to align with the top mating surface of the substrate.
1. An LED assembly, comprising:
a substrate comprising a first top surface that is solder wettable;
a heat sink comprising a flange and a body protruding above the flange, the flange comprising a first bottom surface that is raised below the flange and solder wettable, the body comprising a second top surface that is raised above the body and solder wettable, the first bottom surface having substantially the same shape and area as the first top surface of the substrate, the heat sink being mounted atop the substrate by a first solder between the first bottom surface and the first top surface;
a submount comprising a second bottom surface that is solder wettable, the second bottom surface having substantially the same shape and area as the second top surface of the heat sink, the submount being mounted atop the heat sink by a second solder between the second bottom surface and the second top surface;
an LED die mounted atop the submount;
an insulating body defining a cavity for receiving the heat sink;
metal leads attached to the insulating body; and
bond wires coupling the submount to the metal leads.
2. The assembly of claim 1 , wherein at least one of the first top surface and the second top surface has a hexagon shape.
3. The assembly of claim 1 , wherein the LED die is a flip chip.
4. The assembly of claim 1 , wherein the LED die includes contact pads, wherein the contact pads are mounted to conductors atop the submount by a third solder.
5. The assembly of claim 4 , wherein the third solder has a higher liquidous temperature than the second solder, and the second solder has a higher liquidous temperature than the first solder.
6. The assembly of claim 1 , wherein at least one of(1) the first bottom surface and the first top surface and (2) the second bottom surface and the second top surface have substantially the same shape and area when one circumference is at least 50% of another circumference.
7. The assembly of claim 1 , wherein at least one of(1) the first bottom surface and the first top surface and (2) the second bottom surface and the second top surface have substantially the same shape and area when the first solder aligns the top and bottom mating surfaces with an accuracy of 20 microns or better.