LED-Based Light Source Utilizing Asymmetric Conductors

• US 20120112220A1
• Filed: 04/13/2011
• Published: 05/10/2012
• Est. Priority Date: 11/08/2010
• Status: Active Grant

• Current Assignee: Bridgelux Incorporated
• Original Assignee: Bridgelux Incorporated
• Inventors: Chai, Yan, West, R. Scott
• Granted Patent: US 9,478,719 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48 of an individual wire connector
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/005 relating to encapsulations
• 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 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/486 : adapted for surface mounting
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• 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

A light source includes LED dies that are flip-chip mounted on a flexible plastic substrate. The LED dies are attached to the substrate using an asymmetric conductor material with deformable conducting particles sandwiched between surface mount contacts on the LED dies and traces on the substrate. A diffusively reflective material containing light scattering particles is used instead of expensive reflective cups to reflect light upwards that is emitted sideways from the LED dies. The diffusively reflective material is dispensed over the top surface of the substrate and contacts the side surfaces of the dies. The light scattering particles are spheres of titanium dioxide suspended in silicone. The light source is manufactured in a reel-to-reel process in which the asymmetric conductor material and the diffusively reflective material are cured simultaneously. A silicone layer of molded lenses including phosphor particles is also added over the mounted LED dies in the reel-to-reel process.

Claims

1. A light source comprising:

a light emitting diode (LED) having a first surface, a second surface and a lateral boundary, wherein the second surface is disposed opposite the first surface, wherein the LED die has surface mount contacts on the first surface and emits light from the second surface, and wherein the surface mount contacts include a p-contact and an n-contact;

a mounting substrate having a top surface;

a plurality of connection traces on the top surface of the mounting substrate, wherein the connection traces include an n-trace positioned to underlie the n-contact and a p-trace positioned to underlie the p-contact;

an asymmetric conductor material sandwiched between the surface mount contacts and the connection traces; and

a diffusively reflective material disposed on the top surface of the mounting substrate only outside the lateral boundary of the LED die.

2. The light source of claim 1, wherein the mounting substrate is a flexible plastic substrate.

3. The light source of claim 1, wherein the LED die has a side surface that is substantially perpendicular to the first surface, and wherein the diffusively reflective material contacts the side surface.

4. The light source of claim 1, wherein the diffusively reflective material comprises light scattering particles suspended in a transparent carrier material.

5. The light source of claim 4, wherein the light scattering particles are spheres of titanium dioxide.

6. The light source of claim 4, wherein the light scattering particles exhibit a reflectivity greater than 90 percent.

7. The light source of claim 1, wherein the asymmetric conductor material comprises deformable conducting particles suspended in a transparent carrier material.

8. The light source of claim 1, further comprising:

an optics layer disposed over the diffusively reflective material and the LED die, wherein the optics layer includes a dimple-shaped lens centered over the LED die.

9. A light source comprising:

a light emitting diode (LED) die having a first surface, a second surface and a side surface, wherein the second surface is disposed opposite the first surface, and wherein the side surface is substantially perpendicular to the first surface;

a mounting substrate having a top surface that is parallel to the first surface;

an asymmetric conductor material disposed between the first surface the top surface; and

a diffusively reflective material in contact with the side surface.

10. The light source of claim 9, wherein the mounting substrate is a flexible plastic substrate.

11. The light source of claim 9, whereto the asymmetric conductor material comprises deformable conducting particles suspended in a transparent carrier material, and wherein the diffusively reflective material comprises light scattering particles suspended in the transparent carrier material.

12. The light source of claim 9, wherein the LED die has surface mount contacts on the first surface that include a p-contact and an n-contact, wherein connection traces are disposed on the top surface of the mounting substrate, wherein the connection traces include an n-trace positioned to underlie the n-contact and a p-trace positioned to underlie the p-contact, and wherein the n-contact is electrically coupled to the n-trace through the asymmetric conductor material.

13. A method comprising:

depositing an amount of asymmetric conductor material on a mounting substrate, wherein the asymmetric conductor material comprises deformable conducting particles suspended in a transparent carrier material;

mounting a light emitting diode (LED) die onto the mounting substrate in a flip-chip manner over the deposited amount of asymmetric conductor material;

dispensing a diffusively reflective material onto the mounting substrate adjacent to the mounted LED die such that the diffusively reflective material contacts the LED die, wherein the diffusively reflective material comprises light scattering particles suspended in the transparent carrier material;

pressing the LED die against the mounting substrate such that some of the deformable conducting particles deform; and

heating the transparent carrier material such that both the asymmetric conductor material and the diffusively reflective material cure to a hardened state.

14. The method of claim 13, wherein the asymmetric conductor material is not fully cured before the heating of the transparent carrier material.

15. The method of claim 13, wherein the mounting substrate is a flexible plastic substrate.

16. The method of claim 13, further comprising:

unrolling the mounting substrate using a reel-to-reel machine before the depositing the amount of asymmetric conductor material.

17. The method of claim 13, wherein the transparent carrier material is silicone.

18. The method of claim. 13, further comprising:

depositing a layer of cured transparent carrier material over the LED die and the diffusively reflective material, wherein the layer comprises phosphor particles suspended in the cured transparent carrier material.

19. A light source comprising:

a light emitting diode (LED) die having a first surface and a side surface, wherein the side surface is substantially perpendicular to the first surface;

a mounting substrate having a top surface that is parallel to the first surface;

an asymmetric conductor material disposed between the first surface and the top surface; and

means for reflecting light that is emitted from the side surface of the LED die away from the top surface of the mounting substrate, wherein the means is dispensed onto the mounting substrate adjacent to the LED die, and wherein the mean is more reflective than the asymmetric conductor material.

20. The light source of claim 19, wherein the asymmetric conductor material comprises deformable spheres having an average first diameter, wherein the means comprises second spheres having an average second diameter, and wherein the average first diameter is greater than the average second diameter.

21. The light source of claim 19, wherein the means absorbs less than five percent of the light that is emitted from the side surface of the LED die.