OVER THE MOLD PHOSPHOR LENS FOR AN LED
Rectangular LED dice are mounted on a submount wafer. A first mold has rectangular indentations in it generally corresponding to the positions of the LED dice on the submount wafer. The indentations are filled with silicone, which when cured forms a clear first lens over each LED. Since the wafer is precisely aligned with the mold, the top surfaces of the first lenses are all within a single reference plane irrespective of any x, y, and z misalignments of the LEDs on the wafer. A second mold has rectangular indentations filled with a phosphor-infused silicone so as to form a precisely defined phosphor layer over the clear first lens, whose inner and outer surfaces are completely independent of any misalignments of the LEDs. A third mold forms an outer silicone lens. The resulting PC-LEDs have high chromaticity uniformity from PC-LED to PC LED within a submount wafer and from wafer to wafer, and high color uniformity over a wide viewing angle.
1 . A method for forming a phosphor-converted light emitting diode (PC-LED) comprising:
mounting a plurality of substantially rectangular LED dice on a submount wafer;
molding a substantially rectangular clear first lens directly over each of the LED dice by compression molding, wherein a first mold is first filled with a first lens material, then the LED dice are immersed into the first lens material under compression while the submount wafer is aligned with the first mold, thereafter the clear first lens material is cured, and the LED dice and clear first lenses are separated from the first mold, the clear first lenses encapsulating the LED dice;
molding a substantially rectangular second lens containing a phosphor directly over each of the clear first lenses by compression molding to substantially completely cover an outer surface of the clear first lenses, wherein a second mold is first filled with a second lens material containing the phosphor, then the LED dice and clear first lenses are immersed into the second lens material under compression, thereafter the second lens material is cured, and the LED dice, clear first lenses, and second lenses are separated from the second mold, the second lens having dimensions unrelated to any misalignments of the LED dice in x, y, and z directions on the submount wafer, top surfaces of all the second lenses being substantially in a single reference plane, and a thickness of the second lenses being substantially uniform;
molding a clear third lens directly over each of the second lenses by compression molding to substantially completely cover an outer surface of the second lenses, wherein a third mold is first filled with a third lens material, then the LED dice, clear first lenses, and second lenses are immersed into the third material under compression, thereafter the third lens material is cured, and the LED dice, clear first lenses, second lenses, and clear third lenses are separated from the third mold; and
separating the submount wafer to form individual PC-LEDs.
2 . The method of claim 1 wherein the clear third lens is harder than the clear first lens.
3 . The method of claim 1 wherein the clear third lens has an index of refraction lower than an index of refraction of the clear first lens.
4 . The method of claim 1 wherein the submount wafer has metal leads in electrical contact with metal contacts on the LED dice.
5 . The method of claim 1 wherein the clear third lens has molded features for affecting optical properties of the clear third lens.
6 . The method of claim 1 wherein the clear first lens is substantially rectangular with rounded edges.
9 . The method of claim 1 wherein a range of hardness of the clear first lens is Shore 00 5-90, and the hardness of the clear third lens is greater than Shore A 30.
10 . The method of claim 1 wherein the LED dice emit visible blue light, and an overall color emitted by the PC-LED is a combination of the blue light and a light emitted by the phosphor in the second lens.
11 . The method of claim 1 wherein the LED dice emit a first light color, and an overall color emitted by the PC-LED is primarily light emitted by the phosphor in the second lens.
12 . The method of claim 1 wherein the second lens contains a plurality of phosphor types.
13 . A phosphor-converted light emitting diode (PC-LED) formed by a method comprising:
mounting a plurality of substantially rectangular LED dice on a submount wafer;
molding a substantially rectangular clear first lens directly over each of the LED dice by compression molding, wherein a first mold is first filled with a first lens material, then the LED dice are immersed into the first lens material under compression while the submount wafer is aligned with the first mold, thereafter the clear first lens material is cured, and the LED dice and clear first lenses are separated from the first mold, the clear first lenses encapsulating the LED dice;
molding a substantially rectangular second lens containing a phosphor directly over each of the clear first lenses by compression molding to substantially completely cover an outer surface of the clear first lenses, wherein a second mold is first filled with a second lens material containing the phosphor, then the LED dice and clear first lenses are immersed into the second lens material under compression, thereafter the second lens material is cured, and the LED dice, clear first lenses, and second lenses are separated from the second mold, the second lens having dimensions unrelated to any misalignments of the LED dice in x, y, and z directions on the submount wafer, top surfaces of all the second lenses being substantially in a single reference plane, and a thickness of the second lenses being substantially uniform;
molding a clear third lens directly over each of the second lenses by compression molding to substantially completely cover an outer surface of the second lenses, wherein a third mold is first filled with a third lens material, then the LED dice, clear first lenses, and second lenses are immersed into the third material under compression, thereafter the third lens material is cured, and the LED dice, clear first lenses, second lenses, and clear third lenses are separated from the third mold; and
separating the submount wafer to form individual PC-LEDs.
14 . The PC-LED of claim 13 wherein the clear third lens is harder than the clear first lens.
15 . The PC-LED of claim 13 wherein the clear third lens has an index of refraction lower than an index of refraction of the clear first lens.
16 . The PC-LED of claim 13 wherein the LED dice emit visible blue light, and an overall color emitted by the PC-LED is a combination of the blue light and a light emitted by the phosphor in the second lens.
17 . An intermediate light emitting diode (LED) structure during manufacturing comprising:
a submount wafer, prior to dicing, having a plurality of substantially rectangular flip-chip LED dice mounted thereon,
each LED die having molded directly over it a substantially rectangular clear first lens, wherein each clear first lens is aligned with respect to the submount wafer rather than to the LED dice, such that misalignments of the LED dice on the submount do not affect positions of the clear first lens over each LED die,
each clear lens having molded directly over it a substantially rectangular second lens containing a phosphor to substantially completely cover an outer surface of each clear first lens, wherein each second lens is aligned with respect to the submount wafer rather than to the LED dice, whereby each second lens has dimensions unrelated to any misalignments of the LED dice in x, y, and z directions on the submount wafer, top surfaces of all the second lenses being substantially in a single reference plane, and a thickness of the second lenses being substantially uniform from LED die to LED die, and
each second lens having molded over it a clear third lens to substantially completely cover an outer surface of the second lens.