LED module with hermetic seal of wavelength conversion material
An LED module includes a substrate having a high thermal conductivity and at least one LED die mounted on the substrate. A wavelength conversion material, such as phosphor or quantum dots in a binder, has a very low thermal conductivity and is formed to have a relatively high volume and low concentration over the LED die so that the phosphor or quantum dots conduct little heat from the LED die. A transparent top plate having a high thermal conductivity is positioned over the wavelength conversion material, and a hermetic seal is formed between the top plate and the substrate surrounding the wavelength conversion material. The LED die is located in a cavity in either the substrate or the top plate. In this way, the temperature of the wavelength conversion material is kept well below the temperature of the LED die. The sealing is done in a wafer level process.
1. A light emitting diode (LED) device comprising:
an LED on a substrate, the substrate having a first thermal conductivity;
a wavelength conversion material surrounding the LED, the wavelength conversion material having a second thermal conductivity substantially lower than the first thermal conductivity, a volume of the wavelength conversion material is substantially larger than a volume of the LED;
a sealant material between the substrate and a transparent plate, the transparent plate having a third thermal conductivity greater than the second thermal conductivity, the sealant material extending to an edge of a cavity in the transparent plate surrounding the wavelength conversion material.
2. The LED device of claim 1 , wherein the substrate is substantially flat.
3. The LED device of claim 1 , further comprising a reflective layer on a surface of the substrate.
4. The LED device of claim 3 wherein the reflective later is metal.
5. The LED device of claim 1 , wherein the transparent plate comprises glass and the sealant material comprises glass and the sealant material comprises glass that has been melted to affix the transparent plate to the substrate.
6. The LED device of claim 1 , wherein the sealant material comprises a metal solder and the LED is bonded to a substrate electrode using the same metal solder, and wherein the hermetic seal is formed when the substrate is heated to melt the metal solder.
7. The LED device of claim 1 , wherein the sealant material comprises a metal solder and the LED is bonded to a substrate electrode using the same metal solder, and wherein the hermetic seal is formed when the substrate is heated to melt the metal solder.
8. The LED device of claim 1 , wherein the transparent plate is hermetically sealed to the substrate as a wafer, and the wafer is singulated to form the LED device module.
9. The LED device of claim 1 , wherein the transparent plate has optical features that redirect light emitted by the LED.
10. The LED device of claim 1 , wherein there are at least two cavities in the substrate containing the wavelength conversion material, wherein each of the cavities is sealed so that a break in the hermetic seal of one cavity does not break the hermetic seal of another cavity.
11. The LED device of claim 1 , wherein the wavelength conversion material comprises at least one of phosphor particles in a binder or quantum dots in a binder.
12. The LED device of claim 1 , wherein heat generated by the LED is at least partially removed by thermal conduction of the substrate, the sealant material, and the transparent plate, and wherein a temperature of the wavelength conversion material is lower than a temperature of the LED.
13. The LED device of claim 1 , wherein the second thermal conductivity is at least one order of magnitude lower than the first thermal conductivity.