LED lens design with more uniform color-over-angle emission

• US 9,065,024 B2
• Filed: 04/19/2013
• Issued: 06/23/2015
• Est. Priority Date: 05/01/2012
• Status: Active Grant

• Current Assignee: Bridgelux Incorporated
• Original Assignee: Bridgelux Incorporated
• Inventors: Tong, Tao, Zhang, Wenhui, West, R. Scott
• Primary Examiner(s): Ingham, John C
• Application Number:
  US13/866,562
• Publication Number:
  US 20130292709A1
• Time in Patent Office: 795 Days
• Field of Search: 257/89, 257/98, 257/100, 257/E33.061, 257/E33.073, 438/29
• US Class Current: 1/1
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

An LED device with improved angular color performance has a silicone lens shaped as a portion of a sphere. The lens is molded over an array of LED dies disposed on the upper surface of a substrate. Phosphor particles are disbursed throughout the material used to mold the lens. The distance between farthest apart edges of the LED dies is more than half of the length that the lens extends over the surface of the substrate. The distance from the top of the lens dome to the surface of the substrate is between 57% and 73% of the radius of the sphere. Shaping the lens as the top two thirds of a hemisphere reduces the non-uniformity in the emitted color such that neither of the CIE color coordinates x or y of the color changes more than 0.004 over all emission angles relative to the surface of the substrate.

Claims

1. An apparatus, comprising:

a substrate with a upper surface;

light emitting diode (LED) dies disposed on the upper surface of the substrate, wherein a surface emitter length is a maximum distance between farthest apart edges of the LED dies;

a lens material disposed on the upper surface of the substrate over the LED dies, wherein the lens material is shaped as a portion of a sphere having a dome and a radius, and wherein a dome height extends from a top of the dome to the upper surface of the substrate; and

phosphor particles disbursed throughout the lens material, wherein a bottom chord length is a maximum length that the lens material extends over the upper surface of the substrate, wherein the bottom chord length is less than twice the surface emitter length, and wherein the dome height is between 57% and 73% of the radius.

2. The apparatus of claim 1, wherein the upper surface of the substrate is more reflective than are the LED dies.

3. The apparatus of claim 1, wherein the lens material is silicone.

4. The apparatus of claim 1, wherein the LED dies are arranged in a square matrix of LED dies.

5. The apparatus of claim 1, wherein the lens material is molded over the LED dies.

6. The apparatus of claim 1, further comprising:

a layer of highly reflective material disposed over the upper surface of the substrate, wherein the layer does not extend under the LED dies and does not extend over the LED dies, and wherein the layer contacts at least one edge of each of the LED dies.

7. An apparatus, comprising:

a substrate with a upper surface;

light emitting diode (LED) dies disposed on the upper surface of the substrate, wherein a surface emitter length is a maximum distance between farthest apart edges of the LED dies;

a lens material disposed on the upper surface of the substrate over the LED dies, wherein the lens material is shaped as a portion of a sphere having a dome and a radius, wherein the lens material is compression molded to form the dome together with a flash layer over the upper surface of the substrate, and wherein a dome height extends from a top of the dome to the upper surface of the substrate; and

phosphor particles disbursed throughout the lens material, wherein a bottom chord length is a maximum length that the lens material extends over the upper surface of the substrate, wherein the bottom chord length is less than twice the surface emitter length, and wherein the dome height is between 57% and 73% of the radius.

8. The apparatus of claim 7, further comprising:

contact pads disposed on the upper surface of the substrate, wherein the contact pads are outside of the dome, and wherein the dome and the flash layer are disposed over substantially all of the upper surface of the substrate except for over the contact pads.

9. A method, comprising:

attaching light emitting diode (LED) dies on an upper surface of a substrate, wherein a surface emitter length is a maximum distance between farthest apart edges of the LED dies;

disbursing phosphor particles in a lens material; and

forming a lens over the LED dies using the lens material containing the disbursed phosphor particles, wherein the lens is shaped as a portion of a sphere, wherein the sphere has a radius and the lens has a dome, wherein a dome height extends from a top of the dome to the upper surface of the substrate, wherein a bottom chord length is a maximum length that the lens material extends over the upper surface of the substrate, wherein the bottom chord length is less than twice the surface emitter length, and wherein the dome height is between 57% and 73% of the radius.

10. The method of claim 9, wherein the forming the lens is performed using compression molding.

11. The method of claim 9, wherein the lens material is compression molded to form the lens together with a flash layer over the upper surface of the substrate.

12. The method of claim 9, wherein the upper surface of the substrate is more reflective than are the LED dies.

13. The method of claim 9, wherein the lens material is silicone.

14. The method of claim 9, wherein the LED dies are arranged in a square matrix of LED dies.

15. The method of claim 9, further comprising:

depositing a layer of highly reflective material onto the substrate such that the layer does not cover the LED dies, wherein the depositing occurs after the attaching the LED dies.

16. The method of claim 9, further comprising:

depositing a contact pad on the upper surface of the substrate, wherein the contact pad is laterally outside of the lens, and wherein the forming the lens also forms a flash layer over the upper surface of the substrate; and

removing the flash layer from above the contact pad.

17. The method of claim 15, wherein the layer of highly reflective material is deposited onto the substrate such that the layer contacts at least one edge of each of the LED dies.