Basin, Grigoriy(San Francisco, CA, United States); West, Robert Scott(Morgan Hill, CA, United States); Martin, Paul S.(Pleasanton, CA, United States)  - US 20060105484 A1
05/18/2006
Abstract:
One or more LED dice are mounted on a support structure. The support structure may be a submount with the LED dice already electrically connected to leads on the submount. A mold has indentations in it corresponding to the positions of the LED dice on the support structure. The indentations are filled with a liquid optically transparent material, such as silicone, which when cured forms a lens material. The shape of the indentations will be the shape of the lens. The mold and the LED dice/support structure are brought together so that each LED die resides within the liquid silicone in an associated indentation. The mold is then heated to cure (harden) the silicone. The mold and the support structure are then separated, leaving a complete silicone lens over each LED die. This over molding process may be repeated with different molds to create concentric shells of lenses. Each concentric lens may have a different property, such as containing a phosphor.

Close-up side view of a non-flip-chip LED die mounted on a submount

Background of the invention

LED dies typically emit light in a Lambertian pattern. It is common to use a lens over the LED die to narrow the beam or to make a side-emission pattern. A common type of lens for a surface mounted LED is preformed molded plastic, which is bonded to a package in which the LED die is mounted. One such lens is shown in U.S. Pat. No. 6,274,924, assigned to Lumileds Lighting and incorporated herein by reference.

Brief summary of the invention

A technique for forming a lens for surface mounted LEDs is described herein.
One or more LED dice are mounted on a support structure. The support structure may be a ceramic substrate (a submount) or other type of support structure with the LED dice electrically connected to metal pads on the support structure.
A mold has indentations in it corresponding to the positions of the LED dice on the support structure. The indentations are filled with a liquid, optically transparent material, such as silicone, which when cured forms a hardened lens material. The shape of the indentations will be the shape of the lens. The mold and the LED dice/support structure are brought together so that each LED die resides within the liquid lens material in an associated indentation.
The mold is then heated to cure (harden) the lens material. The mold and the support structure are then separated, leaving a complete lens over each LED die. This general process will be referred to as over molding.
The over molding process may be repeated with different molds to create concentric shells of lenses. Each lens may have a different property, such as containing a phosphor.

Claims

1. A method for forming an optical element over a light emitting diode (LED) die comprising: providing an LED die attached to a support structure; filling a first indentation in a first mold with a liquid first lens material; bringing the first mold and the support structure together so that the LED die is within the liquid first lens material; curing the liquid first lens material until it hardens; and removing the support structure from the first mold so that a first lens formed from the hardened first lens material overlies the LED die.

2. The method of claim 1 wherein bringing the first mold and support structure together comprises bringing the first mold and support structure together so that the LED die is fully within the liquid first lens material, and wherein removing the support structure from the first mold comprises removing the support structure from the first mold so that the first lens formed from the hardened first lens material encapsulates the LED die.

3. The method of claim 1 wherein the liquid first lens material comprises silicone.

4. The method of claim 1 wherein the support structure comprises a submount having metal leads in electrical contact with metal contacts on the LED die.

5. The method of claim 1 wherein the LED die is a flip-chip with metal contacts directly bonded to the metal leads of the submount.

6. The method of claim 1 wherein the support structure comprises a circuit board having metal leads in electrical contact with metal contacts on the LED die.

7. The method of claim 1 wherein the LED die has a phosphor material coating at least one surface of the LED die.

8. The method of claim 1 further comprising: providing a second mold having a second indentation filled with a liquid second lens material; bringing together the second mold and the support structure, having attached to it the LED die having the first lens, so that the first lens is within the liquid second lens material in the second indentation; curing the liquid second lens material until it hardens; and removing the support structure from the second mold so that the hardened second lens material forms a first shell over the first lens.

9. The method of claim 8 wherein the second lens material comprises a first phosphor material.

10. The method of claim 8 wherein the second lens material is different from the first lens material.

11. The method of claim 8 wherein the second lens material comprises a first phosphor material, wherein a light emission from the combination of the LED die and first phosphor material is a white light.

12. The method of claim 8 wherein the second lens material comprises a first phosphor material, the method further comprising: providing a third mold having a third indentation filled with a liquid third lens material; bringing together the third mold and support structure, having attached to it the LED die having the first shell over the first lens; curing the liquid third lens material until it hardens; and removing the support structure from the third mold so that the hardened third lens material forms a second shell over the first shell.

13. The method of claim 12 further comprising: providing a fourth mold having a fourth indentation filled with a liquid fourth lens material, the fourth lens material comprising a second phosphor; bringing together the fourth mold and support structure, having attached to it the LED die having the second shell over the first shell; curing the liquid fourth lens material until it hardens; and removing the support structure from the fourth mold so that the hardened fourth lens material forms a third shell over the second shell.

14. The method of claim 13 further comprising forming a fourth shell containing a third phosphor material overlying the third shell so that a light emission from the combination of the LED die, the first phosphor material, the second phosphor material, and the third phosphor material is a white light

15. The method of claim 1 wherein the LED die is a flip-chip.

16. The method of claim 1 wherein the LED die has at least one wire bond electrically connecting the LED die to the support structure.

17. The method of claim 1 wherein the LED die is one of a plurality of LED dice affixed to the support structure.

18. A light emitting device comprising: a light emitting diode (LED) die attached to a support structure; and a first lens directly molded over the LED die and encapsulating the LED die.

19. The device of claim 18 wherein the first lens is formed over the LED die by the process comprising: filling a first indentation in a first mold with a liquid first lens material; bringing the first mold and support structure together so that the LED die is within the liquid first lens material; curing the liquid first lens material until it hardens; and removing the support structure from the first mold so that a first lens formed from the hardened first lens material overlies the LED die.

20. The device of claim 18 further comprising at least one shell over the first lens formed by molding the at least one shell over the LED die.

21. The device of claim 18 wherein the first lens material comprises silicone.

22. The device of claim 18 wherein the support substrate is a submount having metal leads electrically connected to metal contacts on the LED die.

23. The device of claim 22 wherein the LED die is a flip-chip.

24. The device of claim 18 further comprising a backlight for a display, the backlight incorporating the light emitting diode and first lens.

25. The device of claim 24 wherein the display is a television.

26. The device of claim 18 further comprising a camera having as a flash the light emitting diode and first lens.

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