LED lamp with remote phosphor on a cap structure

1. A lamp, comprising:

a substrate;

a plurality of light-emitting devices located over the substrate, wherein the plurality of light-emitting devices includes a first subset of light-emitting devices that are each free of a phosphor coating and a second subset of light-emitting devices that each include a phosphor coating; and

a cap that is located over the light-emitting devices, wherein the cap has both photo-conversion properties and light-scattering properties, and wherein the cap is located over the first subset of the light-emitting devices but exposes the second subset of the light-emitting devices.

2. The lamp of claim 1 , wherein:

the cap includes at least a first layer and a second layer that are mutually exclusive of each other;

the first layer contains phosphor particles for converting a first spectrum of light to a second spectrum of light; and

the second layer contains diffuser particles for scattering light.

3. The lamp of claim 2 , wherein the cap further includes a third layer that provides mechanical support for the first layer and the second layer.

4. The lamp of claim 1 , wherein a gap exists between the cap and the light-emitting devices.

5. The lamp of claim 4 , wherein the gap is greater than about 0.5 millimeters.

6. The lamp of claim 1 , wherein the cap has a round top-view profile.

7. The lamp of claim 1 , wherein the light-emitting devices include light-emitting diodes (LEDs).

8. The lamp of claim 1 , further comprising:

a thermal dissipation structure that is thermal conductively coupled to the substrate; and

a cover located over the substrate and housing the light-emitting devices and the cap underneath, wherein the cover contains a light-scattering material.

9. The lamp of claim 1 , wherein the substrate contains a ceramic material, a silicon material, a plastic material, a printed circuit board, AlN, Al2O3, Si3N4, or BeO.

10. The lamp of claim 1 , wherein a portion of the cap separates the first subset of the light-emitting devices and the second subset of the light-emitting devices.

11. A lamp, comprising:

a substrate;

a plurality of photonic devices disposed over the substrate, wherein a first group of the photonic devices are non-phosphor-coated, and a second group of the photonic devices are phosphor-coated;

a cap structure that covers the first group of the photonic devices in a top view but exposes the second group of the photonic devices in the top view, wherein the cap structure includes a plurality of sub-layers, and wherein at least a first one of the sub-layers contains phosphor particles, and wherein at least a second one of the sub-layers contains diffuser particles;

a heat sink that is thermal-conductively coupled to the substrate; and

a diffuser cap disposed over the substrate, the photonic devices, and the cap structure.

12. The lamp of claim 11 , wherein at least a third one of the sub-layers of the cap structure contains a polycarbonate material, a polymethyl methacrylate material, or a glass material.

13. The lamp of claim 11 , wherein a vertical distance separates the cap structure and the photonic devices.

14. The lamp of claim 11 , wherein the cap structure has a circular shape in the top view.

15. The lamp of claim 11 , wherein the substrate contains a ceramic material, a silicon material, a plastic material, a printed circuit board, AlN, Al2O3, Si3N4, or BeO.

16. The lamp of claim 11 , wherein the photonic devices include light-emitting diodes (LEDs).

17. A method of assembling a lamp, comprising:

placing a plurality of light-emitting diode (LED) devices on a substrate, wherein a first group of the LED devices are free of being coated with phosphor, and a second group of the LED devices are phosphor-coated;

providing a cap structure, the cap structure including a first sub-layer that contains phosphor particles and a second sub-layer that contains diffuser particles;

placing the cap structure over the substrate, the cap structure covering the first group of the LED devices in a top view but exposing the second group of the LED devices in the top view; and

attaching a diffuser cap to the substrate, the diffuser cap covering the LED devices and the cap structure.

18. The method of claim 17 , wherein the providing of the cap structure comprises forming the cap structure using a roll-to-roll process, a mask process, or an injection molding process.

19. The method of claim 18 , wherein the forming of the cap structure is performed in a manner such that the cap structure comprises a third sub-layer that provides mechanical support to the first and second sub-layers.

20. The method of claim 17 , wherein the placing of the cap structure is performed such that the cap structure is physically separated from the LED devices by a gap.