Forming a multicolor phosphor-converted LED array
An array of phosphor pixels is positioned on an array of semiconductor LED pixels with thermally curable adhesive between them. Selected LED pixels of the array are electrically activated; resulting heat cures the adhesive to attach the corresponding phosphor pixel to the activated LED pixel and to release the corresponding phosphor pixel from a carrier. Removal of the carrier removes unattached phosphor pixels, leaving behind phosphor pixels attached to the LED pixels that were activated. The process can be repeated for phosphor pixels of different colors.
1. A method for making a light emitting apparatus, the method comprising:
positioning on a semiconductor LED array comprising multiple semiconductor LED pixels a first set of phosphor pixels arranged on a carrier substrate, with each phosphor pixel of the first set aligned with a corresponding semiconductor LED pixel of the array, the phosphor pixels of the first set having a layer of thermally curable adhesive, in an uncured state, on a surface thereof opposite the carrier substrate so that a corresponding segment of the adhesive is between and in contact with each phosphor pixel of the first set and a light output surface of the corresponding semiconductor LED pixel; and
electrically operating selected ones of the semiconductor LED pixels to emit light and to heat the corresponding phosphor pixels to a temperature that at least partially cures corresponding discrete segments of the adhesive and bonds each one of the selected semiconductor LED pixels to the corresponding phosphor pixel of the first set.
2. The method of claim 1 , further comprising separating the carrier substrate from the LED array, each phosphor pixel of the first set that is bonded to a corresponding one of the LED pixels remaining on the corresponding LED pixel, while other phosphor pixels of the first set remain on the carrier substrate.
3. The method of claim 1 , the thermally curable adhesive having a cure temperature between about 100° C. and about 150° C.
4. The method of claim 1 , the thermally curable adhesive including a silicone.
5. The method of claim 1 , the thermally curable adhesive has a refractive index between about 1.4 and about 1.6.
6. The method of claim 1 , the phosphor layer including one or more of phosphor/silicone, ceramic phosphor, phosphor in glass, or phosphor on glass.
7. The method of claim 1 , the phosphor pixels of the first set being attached to the carrier substrate by a UV releasable adhesive, wherein operating the selected ones of the semiconductor LED pixels to emit UV light releases the corresponding phosphor pixels from the substrate.
8. The method of claim 7 , further comprising separating the carrier substrate from the LED array, each phosphor pixel of the first set that is bonded to a corresponding one of the LED pixels remaining on the corresponding LED pixel, while other phosphor pixels of the first set remain on the carrier substrate, each area of the carrier substrate from which a phosphor pixel was removed having thereon a layer of the UV releasable adhesive in a released state.
9. The method of claim 1 , the phosphor pixels of the first set being attached to the carrier substrate by a thermally releasable adhesive, wherein operating the selected ones of the semiconductor LED pixels to emit light and to heat the corresponding phosphor pixels of the first set releases those corresponding phosphor pixels from the carrier substrate.
10. The method of claim 9 , the thermally releasable adhesive having a release temperature between about 150° C. and about 220° C.
11. The method of claim 9 , further comprising separating the carrier substrate from the LED array, each phosphor pixel of the first set that is bonded to a corresponding one of the LED pixels remaining on the corresponding LED pixel, while other phosphor pixels of the first set remain on the carrier substrate, each area of the carrier substrate from which a phosphor pixel was removed having thereon a layer of the thermally releasable adhesive in a released state.
12. The method of claim 1 :
the LED array having a second set of multiple phosphor pixels;
each phosphor pixel of the second set being positioned over a light output surface of a corresponding one of a first subset of the LED pixels and attached to that corresponding LED pixel by the thermally curable adhesive in a cured state;
a second subset of the LED pixels having no corresponding phosphor pixel of the second set attached thereto; and
the phosphor pixels of the first and second sets being arranged on the carrier substrate and the LED array, respectively, so that with the phosphor pixels of the first set positioned on the LED array, (i) each phosphor pixel of the first set is aligned with a corresponding one of the LED pixels that lacks a phosphor pixel of the second set, and (ii) each phosphor pixel of the second set is aligned with a corresponding area of the carrier substrate that lacks a phosphor pixel of the first set.
13. The method of claim 12 , the phosphor pixels of the second set including phosphor pixels of one or more colors, the phosphor pixels of the first set including phosphor pixels of at least one color different from the color of any phosphor pixel of the second set.
14. The method of claim 13 , the phosphor pixels of the first set being all a single color.
15. The method of claim 14 , the phosphor pixels of the second set being all a single color.
16. The method of claim 14 , the phosphor pixels of the second set including at least two different colors.
17. The method of claim 14 , the phosphor pixels of the second set including at least three different colors.
18. The method of claim 12 , the phosphor pixels of the second set having corresponding thicknesses less than thickness of any phosphor pixel of the first set.