LED with phosphor tile and overmolded phosphor in lens

• US 7,858,408 B2
• Filed: 02/26/2007
• Issued: 12/28/2010
• Est. Priority Date: 11/15/2004
• Status: Expired due to Fees

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: West, Robert Scott, Mueller-Mach, Regina, Martin, Paul S., Basin, Grigoriy, Mueller, Gerd O., Lim, Tze-Sen, Eberle, Stefan
• Primary Examiner(s): Purvis; Sue
• Assistant Examiner(s): KUO, WENSING W
• Application Number:
  US11/679,143
• Publication Number:
  US 20080048200A1
• Time in Patent Office: 1,401 Days
• Field of Search: 438/26, 438/27, 438/28, 438/29, 257/E21.504, 257/E33.059, 257/E33.061
• US Class Current: 438/27
• CPC Class Codes: B29C 41/14 Dipping a core B29C41/10 takes precedence
• CPC Class Codes: B29C 41/20 incorporating preformed parts or layers, e.g. moulding inserts or for coating articles
• CPC Class Codes: B29C 41/22 Making multilayered or multicoloured articles
• CPC Class Codes: B29K 2995/0031 Refractive
• CPC Class Codes: B29L 2011/00 Optical elements, e.g. lenses, prisms
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• 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 2224/81 using a bump connector
• CPC Class Codes: H01L 2224/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• 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 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01023 : Vanadium [V]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01055 : Cesium [Cs]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12041 : LED
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/1815 : Shape
• CPC Class Codes: H01L 2924/207 : Diameter ranges
• CPC Class Codes: H01L 2924/351 : Thermal stress
• CPC Class Codes: H01L 2933/0041 : relating to wavelength conversion elements
• CPC Class Codes: H01L 33/504 : Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin

Abstract

Overmolded lenses and certain fabrication techniques are described for LED structures. In one embodiment, thin YAG phosphor plates are formed and affixed over blue LEDs mounted on a submount wafer. A clear lens is then molded over each LED structure during a single molding process. The LEDs are then separated from the wafer. The molded lens may include red phosphor to generate a warmer white light. In another embodiment, the phosphor plates are first temporarily mounted on a backplate, and a lens containing a red phosphor is molded over the phosphor plates. The plates with overmolded lenses are removed from the backplate and affixed to the top of an energizing LED. A clear lens is then molded over each LED structure. The shape of the molded phosphor-loaded lenses may be designed to improve the color vs. angle uniformity. Multiple dies may be encapsulated by a single lens. In another embodiment, a prefabricated collimating lens is glued to the flat top of an overmolded lens.

Claims

1. A process for forming a light emitting diode (LED) structure comprising:

providing an LED emitting blue light on a submount;

affixing a substantially flat preformed phosphor plate to the LED, the preformed phosphor plate containing YAG phosphor emitting a yellow light, wherein a combination of blue light from the LED leaking through the phosphor plate and the yellow light produces white light;

providing a mold having an indention corresponding to an intermediate lens;

filling the indention with a liquid lens material containing a phosphor that generates at least red light when excited by the blue light leaking through the phosphor plate;

after the step of filling, immersing at least the phosphor plate and a portion of the LED into the liquid lens material in the mold; and

curing the liquid lens material to form a phosphor-loaded lens over the phosphor plate and LED.

2. The process of claim 1 wherein the liquid lens material encapsulates the LED and phosphor plate.

3. The process of claim 1 further comprising molding a clear lens over the phosphor-loaded lens and the LED by immersing the phosphor-loaded lens and the LED in a liquid lens material in a mold indention and then curing the liquid lens material.

4. The process of claim 1 further comprising determining a color temperature vs. viewing angle of the LED with the phosphor plate affixed to it, and then shaping the mold indention to increase uniformity of the color temperature vs. viewing angle.

5. The process of claim 1 wherein the combination of light from the LED, the phosphor plate, and the phosphor-loaded lens produces white light.

6. The process of claim 1 wherein the LED is mounted on a submount along with a plurality of identical LEDs, wherein the step of immersing at least the phosphor plate into the liquid lens material in the mold comprises immersing all the LEDs on the submount into the liquid lens material in an associated mold indentation at the same time.

7. A process for forming a light emitting diode (LED) structure comprising:

providing an LED emitting blue light or UV light on a submount;

molding a first phosphor phosphor-loaded lens containing a first phosphor over the LED;

molding a second phosphor-loaded lens over the first phosphor-loaded lens, the second phosphor-loaded lens containing a second phosphor different from the first phosphor; and

determining a color temperature vs. viewing angle of the LED with the first phosphor-loaded lens, and then molding the second phosphor-loaded lens to increase uniformity of the color temperature vs. viewing angle.

8. A process for forming a light emitting diode (LED) structure comprising:

providing an LED on a submount;

providing a first mold having a first indention with a shape corresponding to a first lens;

filling the first indention with a first liquid lens material;

after the step of filling, immersing the LED into the first liquid lens material in the first mold;

curing the first liquid lens material to form the first lens over the LED;

removing the LED with the first lens from the first mold;

plasma treating the first lens;

providing a second mold having a second indention with a shape corresponding to a second lens;

filling the second indention with a second liquid lens material;

after the step of filling the second indentation, immersing the LED and first lens into the second liquid lens material in the second mold;

curing the second liquid lens material to form the second lens over the LED, wherein the step of plasma treating increases adherence of the first lens to the second lens; and

removing the LED with the first lens and second lens from the second mold.

9. The process of claim 8 wherein the first lens material is the same as the second lens material.

10. The process of claim 8 wherein the first lens contains phosphor.

11. The process of claim 8 wherein plasma treating comprises plasma treating the first lens at between approximately 200-600 Watts to etch the first lens.