Bonding an optical element to a light emitting device

• US 20060105478A1
• Filed: 11/12/2004
• Published: 05/18/2006
• Est. Priority Date: 11/12/2004
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Krames, Michael R., Steranka, Frank M., Camras, Michael D., Wall, Franklin J. Jr., Imler, William R., Tichy, Ladislav, Ticha, Helena
• Granted Patent: US 7,419,839 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• 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 33/58 Optical field-shaping elements
• CPC Class Codes: H05B 45/20 Controlling the colour of the light

Abstract

A device is provided with at least one light emitting device (LED) die mounted on a submount with an optical element subsequently thermally bonded to the LED die. The LED die is electrically coupled to the submount through contact bumps that have a higher temperature melting point than is used to thermally bond the optical element to the LED die. In one implementation, a single optical element is bonded to a plurality of LED dice that are mounted to the submount and the submount and the optical element have approximately the same coefficients of thermal expansion. Alternatively, a number of optical elements may be used. The optical element or LED die may be covered with a coating of wavelength converting material. In one implementation, the device is tested to determine the wavelengths produced and additional layers of the wavelength converting material are added until the desired wavelengths are produced.

Claims

1. A method comprising:

mounting at least one light emitting device die to a submount through contact elements; and

bonding an optical element to the at least one light emitting device die after the light emitting device die is mounted to the submount, wherein the bonding of the optical element to the at least one light emitting device die is effected by a bonding layer disposed between the optical element and the at least one light emitting device die.

2. The method of claim 1, wherein the bonding layer comprises an inorganic material.

3. The method of claim 1, wherein bonding comprises:

elevating the temperature of the optical element, the bonding layer, the light emitting device die, and the submount to a temperature that is less than the melting temperature of the contact elements; and

applying a pressure to press the optical element and the light emitting device die together, thereby bonding the optical element to the light emitting device die through the bonding layer.

4. The method of claim 3, wherein the temperature is elevated to a temperature that is greater than the temperature used to mount the light emitting device die and the submount.

5. The method of claim 1, wherein the contact elements are on at least one of the bottom surface of the light emitting device die and the top surface of the submount, the contact elements providing electrical contact between the light emitting device die and the submount.

6. The method of claim 5, wherein the contact elements are at least one of bumps and pads formed from a material that includes at least one of Au and AuSn.

7. The method of claim 4, wherein the temperature used to mount the at least one light emitting device die to the submount is less than approximately 250°

C.

8. The method of claim 1, wherein the temperature used to bond the optical element to the at least one light emitting device die is less than approximately 400°

C.

9. The method of claim 1, wherein the bonding layer between the optical element and the light emitting device die comprises at least one of an oxide of tellurium, oxide of tungsten, oxide of lead, and oxide of zinc.

10. The method of claim 1, wherein the bonding layer between the optical element and the light emitting device die comprises at least one of an oxide of sodium, oxide of potassium, oxide of lithium, and fluoride of zinc.

11. The method of claim 1, wherein a plurality of light emitting device dice are mounted to the submount.

12. The method of claim 11, wherein one optical element is bonded to the plurality of light emitting device dice.

13. The method of claim 12, further comprising selecting the submount and the one optical element to have approximately matching coefficients of thermal expansion.

14. The method of claim 11, wherein a separate optical element is bonded to each of the plurality of light emitting device dice.

15. The method of claim 1, further comprising depositing a coating of wavelength converting material over the optical element.

16. The method of claim 15, wherein depositing a coating of wavelength converting material over the optical element comprises:

depositing a layer of the wavelength converting material over the optical element;

determining the wavelengths of light produced by the device when a forward biasing current is applied to the light emitting device die;

repeatedly altering the thickness of the layer of wavelength converting material and determining the wavelengths of light produced by the device until the desired wavelengths of light are produced.

17. The method of claim 1, further comprising placing a layer of wavelength converting material between the at least one light emitting device die and the optical element prior to bonding the optical element to the light emitting device die.

18. The method of claim 17, wherein the layer of wavelength converting material is bonded on at least one of the bottom surface of the optical element and the top surface of the light emitting device die.

19. The method of claim 1, wherein the optical element includes wavelength converting material.

20. The method of claim 1, wherein the light emitting device die comprises a stack of semiconductor layers, at least one of which is an active region that emits lights, and a first contact and a second contact electrically coupled to apply a voltage across the active region;

the first contact and the second contact disposed on a same side of the stack.

21. A method comprising:

providing a submount having a first coefficient of thermal expansion;

providing a plurality of light emitting device dice;

mounting the plurality of light emitting device dice to the submount;

providing an optical element having a second coefficient of thermal expansion that is approximately the same as the first coefficient of thermal expansion; and

bonding the optical element to the plurality of light emitting device dice after the light emitting device dice are mounted to the submount.

22. The method of claim 21, wherein mounting the plurality of light emitting device dice to the submount is performed using one of thermo-compression and thermo-sonic bonding.

23. The method of claim 22, wherein bonding the optical element to the plurality of light emitting device dice comprises elevating the temperature of the optical element, the light emitting device dice and the submount to a temperature that is greater than that the temperature used to mount the plurality of light emitting device dice and the submount, and applying a pressure to press the optical element and the light emitting device dice together.

24. The method of claim 23, wherein at least one of the light emitting device dice and the submount include contact elements, the contact elements providing electrical contact between the light emitting device dice and the submount and wherein the temperature of bonding the optical element to the plurality of light emitting device dice is less than the melting temperature of the contact elements.

25. The method of claim 24, wherein the contact elements are at least one of bumps and pads formed from a material that includes at least one of Au and AuSn.

26. The method of claim 22, wherein the coefficients of thermal expansion of the plurality of light emitting device dice are approximately the same as the first coefficient of thermal expansion.

27. The method of claim 21, further comprising depositing a coating of wavelength converting material over the optical element.

28. The method of claim 27, wherein depositing a coating of wavelength converting material over the optical element comprises:

depositing a layer of the wavelength converting material over the optical element;

determining the wavelengths of light produced by the device when a forward biasing current is applied to the light emitting device die;

repeatedly altering the thickness of the layer of wavelength converting material and determining the wavelengths of light produced by the device until the desired wavelengths of light are produced.

29. The method of claim 21, wherein each of the light emitting device dice comprise a stack of semiconductor layers, at least one of which is an active region that emits light, and a first contact and a second contact electrically coupled to apply a voltage across the active region;

the first contact and the second contact disposed on a same side of the stack.

30. An apparatus comprising:

a submount;

a plurality of light emitting device dice mounted to the submount; and

a single optical element bonded to a surface of each of the plurality of light emitting device dice.

31. The apparatus of claim 30, further comprising contact elements that are on at least one of the top surface of the submount and the bottom surfaces of the light emitting device dice, the light emitting device dice being electrically coupled to the submount through the contact elements.

32. The apparatus of claim 31, wherein the contact elements are formed from a material that includes at least one of Au and AuSn.

33. The apparatus of claim 30, further comprising a coating of wavelength converting material over the optical element.

34. The apparatus of claim 30, further comprising a layer of wavelength converting material between the optical element and at least a plurality of the light emitting device dice.

35. The apparatus of claim 30, wherein the submount and the optical element are formed from materials with approximately the same coefficient of thermal expansion.

36. The apparatus of claim 35, wherein the light emitting device dice have coefficients of thermal expansion that are approximately the same as the coefficient of thermal expansion of the submount.

37. The apparatus of claim 30, further comprising a layer of a bonding material between the optical element and each of the light emitting device dice, the bonding layer comprising an inorganic material.

38. The apparatus of claim 30, wherein each of the light emitting device dice comprise a stack of semiconductor layers, at least one of which is an active region that emits lights, and a first contact and a second contact electrically coupled to apply a voltage across the active region;

the first contact and the second contact disposed on a same side of the stack.

39. A method comprising:

mounting at least one light emitting device die to a submount with contact elements, wherein the light emitting device die is mounted to the submount at a first temperature; and

bonding an optical element to the at least one light emitting device die after the light emitting device die is mounted to the submount, wherein the optical element is bonded to the light emitting device die at a second temperature that is greater than the first temperature.

40. The method of claim 39, wherein the light emitting device die is mounted to the submount thermosonically.

41. The method of claim 39, wherein the second temperature is between approximately 150°

C. and 450°

C.

42. The method of claim 39, wherein the contact elements melt at a third temperature and wherein the second temperature is less than the third temperature.

43. The method of claim 39, wherein the contact elements are at least one of bumps and pads formed from a material that includes at least one of Au and AuSn.

44. A device comprising:

a semiconductor light emitting device comprising a stack of semiconductor layers including an active region;

an optical element bonded to the semiconductor light emitting device;

a bonding layer disposed between the optical element and the semiconductor light emitting device, wherein the bonding layer comprises an oxide of tellurium; and

a submount electrically connected to the light emitting device.

45. The device of claim 44, wherein the submount comprises a ceramic.

46. The device of claim 44, wherein the submount comprises a material selected from the group of AlN, alumina, and Si.

47. The device of claim 44, further comprising contact elements that electrically connect the submount to the light emitting device, wherein the contact elements are formed from a material that includes at least one of Au and AuSn.

48. The device of claim 44, wherein the optical element comprises a material selected from the group of sapphire, SiC, aluminum oxynitride, zirconia oxide, GaN, AlN, spinel, GaP, ZnS, an oxide of tellurium, an oxide of lead, an oxide of tungsten, and transparent alumina.

49. A device comprising:

a semiconductor light emitting device comprising a stack of semiconductor layers including an active region;

an optical element bonded to the semiconductor light emitting device; and

a bonding layer disposed between the optical element and the semiconductor light emitting device, wherein the bonding layer comprises a material selected from the group of an oxide of lead, an oxide of tungsten, and an oxide of zinc.

50. The device of claim 49, further comprising a submount electrically connected to the light emitting device.

51. The device of claim 50, wherein the submount comprises a ceramic.

52. The device of claim 50, wherein the submount comprises a material selected from the group of AlN, alumina, and Si.

53. The device of claim 50, further comprising contact elements that electrically connect the submount to the light emitting device, wherein the contact elements are formed from a material that includes at least one of Au and AuSn.

54. The device of claim 49, wherein the optical element comprises a material selected from the group of sapphire, SiC, aluminum oxynitride, zirconia oxide, GaN, AlN, spinel, GaP, ZnS, an oxide of tellurium, an oxide of lead, an oxide of tungsten, and transparent alumina.

55. A method comprising:

providing a semiconductor light emitting device comprising a stack of semiconductor layers including an active region;

providing an optical element; and

bonding the semiconductor light emitting device to the optical element effected by a bonding layer disposed between the optical element and the semiconductor light emitting device, wherein the bonding layer comprises a material selected from the group of an oxide of tellurium, an oxide of lead, an oxide of tungsten, and an oxide of zinc.

56. The method of claim 55, wherein the temperature used to bond the light emitting device to the optical element is between about 200°

C. and 400°

C.

57. The method of claim 55, wherein the time that the optical element and light emitting device are at bonding temperature is between about 30 seconds and 30 minutes.

58. The method of claim 55, wherein the pressure used to bond the light emitting device to the optical element is between about 700 and 3000 psi.

59. The method of claim 55, further comprising bonding the semiconductor light emitting device to a submount before bonding the semiconductor light emitting device to the optical element.

60. A device comprising:

a semiconductor light emitting device comprising a stack of semiconductor layers including an active region;

an optical element bonded to the semiconductor light emitting device; and

a bonding layer disposed between the optical element and the semiconductor light emitting device, wherein the bonding layer comprises a material selected from the group of chalcogenide and chalcogen-halogenide glass.