Wafer level packaging of light emitting diodes (LEDs)
An LED wafer includes LED dies on an LED substrate. The LED wafer and a carrier wafer are joined. The LED wafer that is joined to the carrier wafer is shaped. Wavelength conversion material is applied to the LED wafer that is shaped. Singulation is performed to provide LED dies that are joined to a carrier die. The singulated devices may be mounted in an LED fixture to provide high light output per unit area.
1. A lighting device comprising:
a crystalline substrate comprising an inner face, an outer face opposing the inner face, and a thickness;
an array of LEDs supported by the crystalline substrate proximate to the inner face, wherein the array of LEDs comprises a plurality of LEDs, and a plurality of conductive contacts, including a plurality of anode contacts and a plurality of cathode contacts in conductive electrical communication with the array of LEDs, the array of LEDs is arranged to transmit LED emissions through the crystalline substrate to exit the outer face, and the array of LEDs is arranged in a flip-chip configuration, with the array of LEDs positioned between the crystalline substrate and all conductive contacts of the plurality of conductive contacts;
a plurality of recesses arranged between LEDs of the plurality of LEDs, and extending from the outer face of the crystalline substrate in a direction toward the inner face; and
a wavelength conversion material arranged on or over the outer face of the crystalline substrate;
wherein each recess of the plurality of recesses is partially filled with the wavelength conversion material, each recess is partially not filled with the wavelength conversion material, and a non-uniform width of the wavelength conversion material is provided between adjacent LEDs of the plurality of LEDs over a majority of a depth of each recess.
2. The lighting device of claim 1 , wherein the crystalline substrate is continuous between different LEDs of the array of LEDs.
3. The lighting device of claim 2 , wherein each recess of the plurality of recesses extends through less than an entirety of the thickness of the crystalline substrate.
4. The lighting device of claim 1 , wherein the crystalline substrate comprises one of silicon carbide or sapphire.
5. The lighting device of claim 1 , wherein the outer face of the crystalline substrate comprises textural features.
6. The lighting device of claim 1 , wherein the crystalline substrate comprises a crystalline growth substrate on which epitaxial layers forming the array of LEDs were grown.
7. The lighting device of claim 1 , wherein each LED of the array of LEDs is in electrical communication with (i) a different anode contact of the plurality of anode contacts and (ii) a different cathode contact of the plurality of cathode contacts.
8. The lighting device of claim 1 , wherein the plurality of anode contacts and the plurality of cathode contacts are coplanar.
9. The lighting device of claim 1 , wherein each recess of the plurality of recesses comprises an air gap extending between portions of the wavelength conversion material with which the recess is partially filled.
10. The lighting device of claim 1 , wherein each recess of the plurality of recesses comprises beveled walls arranged non-perpendicular to the outer face.
11. The lighting device of claim 1 , further comprising a carrier comprising a plurality of anode pads in conductive electrical communication with the plurality of anode contacts, and comprising a plurality of cathode pads in conductive electrical communication with the plurality of cathode contacts.
12. The lighting device of claim 11 , wherein:
the carrier comprises an inner surface and an outer surface that opposes the inner surface;
the plurality of anode pads and the plurality of cathode pads are arranged on or along the inner surface; and
the carrier further comprises a plurality of packaged device anodes and a plurality of packaged device cathodes arranged on or along the outer surface.
13. The lighting device of claim 12 , wherein the carrier comprises a body, a first group of conductive vias extending through the body to provide conductive electrical communication between the plurality of anode pads and the plurality of packaged device anodes, and a second group of conductive vias extending through the body to provide conductive electrical communication between the plurality of cathode pads and the plurality of packaged device cathodes.
14. A method for fabricating a lighting device, the method comprising:
growing epitaxial layers over an inner face of a crystalline growth substrate to produce an array of LEDs comprising a plurality of LEDs, the crystalline growth substrate further comprising an outer face opposing the inner face, and a thickness;
providing a plurality of conductive contacts including a plurality of anode contacts and a plurality of cathode contacts in conductive electrical communication with the array of LEDs, wherein the array of LEDs is arranged in a flip-chip configuration, with the array of LEDs positioned between the crystalline growth substrate and all conductive contacts of the plurality of conductive contacts;
defining a plurality of recesses in the crystalline growth substrate extending in a direction from the outer face toward the inner face, wherein individual recesses of the plurality of recesses are registered with boundaries between different LEDs of the array of LEDs; and
providing a wavelength conversion material on or over the outer face of the crystalline growth substrate, and into each recess of the plurality of recesses;
wherein each recess of the plurality of recesses is partially filled with the wavelength conversion material, each recess is partially not filled with the wavelength conversion material, and a non-uniform width of the wavelength conversion material is provided between adjacent LEDs of the plurality of LEDs over a majority of a depth of each recess.
15. The method of claim 14 , wherein the crystalline growth substrate is continuous between different LEDs of the array of LEDs, and each recess of the plurality of recesses extends through less than an entirety of the thickness of the crystalline growth substrate.
16. The method of claim 14 , wherein the defining of the plurality of recesses comprises forming beveled walls in the crystalline growth substrate, and the beveled walls are arranged non-perpendicular to the outer face.
17. The method of claim 14 , further comprising forming textural features on the outer face of the crystalline growth substrate prior to the provision of the wavelength conversion material on or over the outer face.
18. The method of claim 14 , wherein the provision of the wavelength conversion material on or over the outer face comprises controlling a thickness of the wavelength conversion material to sidewalls of each recess of the plurality of recesses, and leaving an air gap extending between portions of the wavelength conversion material with which each recess is partially filled.
19. The method of claim 14 , wherein:
the lighting device further comprises a carrier comprising a plurality of anode pads and a plurality of cathode pads; and
the method further comprising establishing conductive electrical communication between the plurality of anode pads and the plurality of anode contacts, and establishing conductive electrical communication between the plurality of cathode pads and the plurality of cathode contacts.
20. The method of claim 19 , wherein the carrier comprises:
a body having an outer surface:
a plurality of packaged device anodes and a plurality of packaged device cathodes arranged on or along the outer surface;
a first group of conductive vias extending through the body to provide conductive electrical communication between the plurality of anode pads and the plurality of packaged device anodes, and
a second group of conductive vias extending through the body to provide conductive electrical communication between the plurality of cathode pads and the plurality of packaged device cathodes.