Wafer level package for very small footprint and low profile white LED devices
View Patent ↗A surface mount LED package having a tight footprint and small vertical image size is fabricated by a method comprising: forming light emitting diode chips each having a substrate and a plurality of layers configured to emit electroluminescence responsive to electrical energizing; forming electrical vias in a sub mount, the electrical vias passing from a front side of the sub-mount to a back-side of the sub-mount; flip chip bonding the light emitting diode chips on the front-side of the sub mount such that each light emitting diode chip electrically contacts selected electrical vias; thinning or removing the substrates of the flip-chip bonded light emitting diode chips; and after the thinning, disposing a phosphor over the flip chip bonded light emitting diode chips.
1. A method for fabricating a light emitting diode package, the method comprising:
forming light emitting diode chips each having a substrate and a plurality of layers configured to emit electroluminescence responsive to electrical energizing;
forming electrical vias in a sub mount, the electrical vias passing from a front-side of the sub-mount to a back-side of the sub-mount;
flip chip bonding the light emitting diode chips on the front-side of the sub-mount such that each light emitting diode chip electrically contacts selected electrical vias;
thinning or removing the substrates of the flip-chip bonded light emitting diode chips; and
after the thinning, disposing a phosphor over the flip chip bonded light emitting diode chips.
2. The method as set forth in claim 1 , further comprising:
after the disposing of the phosphor, separating the submount to form surface mount light emitting diode packages.
3. The method as set forth in claim 1 , further comprising:
disposing an underfill material between the front-side of the sub-mount and the light emitting diode chips.
4. The method as set forth in claim 3 , wherein the underfill material is disposed before flip-chip bonding.
5. The method as set forth in claim 3 , wherein the underfill material is disposed after the flip-chip bonding.
6. A method for fabricating a light emitting diode package, the method comprising:
forming light emitting diode chips each having a substrate and a plurality of layers configured to emit electroluminescence responsive to electrical energizing;
forming electrical vias in a sub-mount, the electrical vias passing from a front-side of the sub-mount to a back-side of the sub-mount;
flip chip bonding the light emitting diode chips on the front-side of the sub-mount such that each light emitting diode chip electrically contacts selected electrical vias;
removing the substrates of the flip-chip bonded light emitting diode chips; and
after the removing of the substrates, disposing a phosphor over the flip chip bonded light emitting diode chips.
7. The method as set forth in claim 6 , wherein the removing comprises removing the substrate by an optical lift-off process.
8. The method as set forth in claim 6 , wherein the removing comprises removing the substrate by a laser lift-off process.
9. The method as set forth in any one of claims 8 , wherein the light emitting diode chips are group III nitride-based light emitting diode chips.
10. The method as set forth in claim 9 , wherein the light emitting diode chips emit UV light and the disposing of a phosphor comprises disposing a phosphor that produces substantially white converted light.
11. The method as set forth in claim 9 , wherein the light emitting diode chips emit violet or blue light and the disposing of a phosphor comprises disposing a phosphor that produces substantially yellowish converted light that blends with the violet or blue light to output substantially white light.
12. The method as set forth in claim 1 , wherein the disposing of a phosphor comprises disposing a phosphor over substantially the entire frontside of the submount including the light emitting diode chips.
13. The method as set forth in claim 1 , wherein the disposing of a phosphor comprises disposing a phosphor over the light emitting diode chips without substantial disposing onto exposed areas of the frontside of the submount.
14. The method as set forth in claim 13 , wherein the disposing of a phosphor comprises disposing the phosphor over each light emitting diode chip in an area including the light emitting diode chip that is less than 20 microns larger than the light emitting diode chip.
15. A method for fabricating a light emitting diode package, the method comprising:
forming light emitting diode chips each having a substrate and a plurality of layers configured to emit electroluminescence responsive to electrical energizing;
forming electrical vias in a sub-mount, the electrical vias passing from a front-side of the sub-mount to a back-side of the sub-mount;
flip chip bonding the light emitting diode chips on the front-side of the sub-mount such that each light emitting diode chip electrically contacts selected electrical vias;
thinning or removing the substrates of the flip-chip bonded light emitting diode chips wherein the light emitting diode chips after thinning or removal of the substrate have thicknesses of less than 5 microns; and
after the thinning, disposing a phosphor over the flip chip bonded light emitting diode chips.
16. The method as set forth in claim 1 , wherein the disposing a phosphor comprises:
selectively deposited the phosphor in areas each encompassing and slightly larger than one of the light emitting diode chips.
17. The method as set forth in claim 16 , wherein the areas of selective phosphor deposition each extend less than 20 microns larger than the light emitting diode chip.