Stenciling phosphor layers on light emitting diodes

• US 6,650,044 B1
• Filed: 10/13/2000
• Issued: 11/18/2003
• Est. Priority Date: 10/13/2000
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Lowery, Christopher H.
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Yun, Jurie
• Application Number:
  US09/688,053
• Time in Patent Office: 1,131 Days
• Field of Search: 313/498, 313/499, 313/503, 313/506, 313/502, 313/511, 313/512, 313/504, 313/485, 313/486, 257/40, 257/98, 257/99, 257/100, 438/82, 438/99, 445/25
• US Class Current: 313/502
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil

Abstract

A method for forming a luminescent layer on a light emitting semiconductor device includes positioning a stencil on a substrate such that a light emitting semiconductor device disposed on the substrate is located within an opening in the stencil, depositing a stenciling composition including luminescent material in the opening, removing the stencil from the substrate, and curing the stenciling composition to a solid state. The resulting light emitting device includes a stack of layers including semiconductor layers comprising an active region and a luminescent material containing layer having a substantially uniform thickness disposed around at least a portion of the stack. A surface of the luminescent material containing layer not adjacent to the stack substantially conforms to a shape of the stack. In one embodiment, the light emitting device emits white light in a uniformly white spatial profile.

Claims

1. A light emitting device comprising:

a stack of layers including semiconductor layers comprising an active region, the stack of layers being attached to a superstrate; and

a luminescent material containing layer having a substantially uniform thickness disposed around at least a portion of said stack;

wherein the stack of layers is oriented in a flip chip geometry and a surface of said luminescent material containing layer not adjacent to said stack substantially conforms to a shape of said stack.

2. The light emitting device of claim 1, wherein said luminescent material containing layer comprises at least one silicone polymer.

3. The light emitting device of claim 1, wherein said luminescent material containing layer comprises silica particles.

4. The light emitting device of claim 3, wherein said silica particles are fumed silica particles.

5. The light emitting device of claim 1, wherein said luminescent material containing layer comprises phosphors that convert light of a wavelength emitted by said active region to at least another wavelength.

6. The light emitting device of claim 5, wherein said phosphors comprise yttrium aluminum garnet doped with gadolinium and cerium.

7. The light emitting device of claim 1, wherein said active region emits blue light, and wherein said luminescent material containing layer includes phosphors that convert a portion of said blue light to light combinable with a remaining portion of said blue light to produce white light.

8. The light emitting device of claim 1, further comprising an optically transparent layer disposed between said luminescent material containing layer and said stack.

9. The light emitting device of claim 8 wherein the optically transparent layer comprises at least one silicone polymer.

10. The light emitting device of claim 8 wherein the optically transparent layer comprises silica particles.

11. The light emitting device of claim 1 further comprising a substrate connected to a surface of the semiconductor layers opposite the superstrate.

12. The light emitting device of claim 1 wherein at least a portion of light emitted by the active region is extracted from the device through the superstrate.

13. The light emitting device of claim 1 wherein the luminescent material containing layer overlies the superstrate.

14. A light emitting device comprising:

a stack of layers including semiconductor layers comprising an active region, the stack of layers being attached to a superstrate; and

a luminescent material containing layer having a substantially uniform thickness disposed around at least a portion of said stack, said luminescent material containing layer comprising a silicone polymer, fumed silica particles, and phosphors;

wherein the stack of layers is oriented in a flip chip geometry and a surface of said luminescent material containing layer not adjacent to said stack substantially conforms to a shape of said stack.