LIGHT EMITTING DIODE FOR HARSH ENVIRONMENTS

• US 20080218759A1
• Filed: 03/06/2008
• Published: 09/11/2008
• Est. Priority Date: 03/08/2007
• Status: Active Grant

• Current Assignee: Senseonics, Incorporated (Senseonics Holdings, Inc.)
• Original Assignee: Sensors For Medicine and Science Incorporated
• Inventors: DeHennis, Andrew, Colvin, Jason D., Krsmanovic, Jody L., Colvin, Arthur E.
• Granted Patent: US 7,939,832 B2
• Time in Patent Office: Days
• US Class Current: 356/442
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• 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 2924/00012 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 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01087 Francium [Fr]
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding
• 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 31/0203 Containers; Encapsulations , e.g. encapsulation of photodiodesfor photovoltaic devices H01L31/048; for organic photosensitive devices H10K30/80
• CPC Class Codes: H01L 31/125 Composite devices with photosensitive elements and electroluminescent elements within one single body
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/483 : Containers
• CPC Class Codes: H01L 33/52 : Encapsulations
• CPC Class Codes: H01L 33/54 : having a particular shape
• 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 emitting diode for harsh environments includes a substantially transparent substrate, a semiconductor layer deposited on a bottom surface of the substrate, several bonding pads, coupled to the semiconductor layer, formed on the bottom surface of the substrate, and a micro post, formed on each bonding pad, for electrically connecting the light emitting diode to a printed circuit board. An underfill layer may be provided between the bottom surface of the substrate and the top surface of the printed circuit board, to reduce water infiltration under the light emitting diode substrate. Additionally, a diffuser may be mounted to a top surface of the light emitting diode substrate to diffuse the light emitted through the top surface.

Claims

1. A light emitting diode for harsh environments, comprising:

a substantially transparent substrate;

a semiconductor layer deposited on a bottom surface of the substrate;

a plurality of bonding pads, coupled to the semiconductor layer, formed on the bottom surface of the substrate; and

a plurality of micro posts, formed on the bonding pads, for electrically connecting the light emitting diode to a printed circuit board.

2. The light emitting diode of claim 1, wherein the substrate is sapphire.

3. The light emitting diode of claim 1, wherein the semiconductor layer includes at least one p-n junction.

4. The light emitting diode of claim 1, wherein the plurality of bonding pads and the plurality of micro posts are gold.

5. The light emitting diode of claim 4, wherein the plurality of micro posts are bonded to the plurality of bonding pads and to a respective plurality of gold bonding pads on the printed circuit board, one micro post to each bonding pad pair.

6. The light emitting diode of claim 5, wherein the micro posts are bonded to the bonding pads using thermocompression bonding, thermosonic bonding, ultrasonic bonding, or welding.

7. The light emitting diode of claim 1, further comprising a diffuser, mounted to a top surface of the substrate, to diffuse the light emitted through the top surface of the substrate.

8. The light emitting diode of claim 1, further comprising an underfill layer, including a polymer and a filler, disposed between the bottom surface of the substrate and a top surface of the printed circuit board, to reduce water infiltration under the substrate.

9. The light emitting diode of claim 8, wherein the filler includes a plurality of microballoons and the polymer is cyanate ester.

10. The light emitting diode of claim 8, wherein the filler is a light-scattering filler and the polymer is an optical epoxy.

11. The light emitting diode of claim 8, wherein the underfill layer is about 70% by weight of polymer and about 30% by weight of filler.

12. The light emitting diode of claim 9, wherein each microballoon has a diameter from about 2 μ

m to about 11 μ

m.

13. The light emitting diode of claim 9, wherein each microballoon is a gas-filled sphere having a diameter of about 11 μ

m and a wall thickness of about 1 μ

m.

14. The light emitting diode of claim 7, wherein the diffuser includes titanium(IV) oxide to increase light reflectivity.

15. The light emitting diode of claim 7, wherein the diffuser includes microballoons to increase light reflectivity.

16. The light emitting diode of claim 8, wherein the light-scattering filler is titanium(IV) oxide and the optical epoxy is Epo-Tek 301-2.

17. The light emitting diode of claim 9, wherein the microballoons are pre-treated with an adhesion promoter.

18. The light emitting diode of claim 17, wherein the adhesion promoter is silane.

19. The light emitting diode of claim 7, wherein the diffuser is a substantially transparent, hemispherical diffuser.

20. A semiconductor device for harsh environments, comprising:

a printed circuit board having a top surface with a plurality of gold bonding pads;

a light emitting diode, including;

a substantially transparent substrate,

a semiconductor layer deposited on a bottom surface of the substrate,

a plurality of gold bonding pads, coupled to the semiconductor layer, formed on the bottom surface of the substrate, and

a plurality of gold micro posts, formed on the bonding pads, bonded to the gold bonding pads of the printed circuit board;

an underfill layer, including a polymer and a filler, disposed between the bottom surface of the substrate and the top surface of the printed circuit board, to reduce water infiltration under the light emitting diode substrate; and

a substantially transparent, hemispherical diffuser, mounted to a top surface of the substrate, to diffuse the light emitted through the top surface of the substrate.

21. The semiconductor device of claim 20, wherein the filler includes a plurality of gas-filled, glass microballoons and the polymer is cyanate ester.

22. The semiconductor device of claim 20, wherein the underfill layer is about 70% by weight of epoxy and about 30% by weight of filler.

23. The semiconductor device of claim 21, wherein each microballoon has a diameter from about 2 μ

m to about 11 μ

m, and a wall thickness of about 1 μ

m.

24. The semiconductor device of claim 20, wherein the filler is a light-scattering filler and the polymer is an optical epoxy.

25. The semiconductor device of claim 24, wherein the light-scattering filler is titanium(IV) oxide and the optical epoxy is Epo-Tek 301-2.

26. The semiconductor device of claim 20, wherein the micro posts are bonded to the bonding pads using thermocompression bonding, thermosonic bonding, ultrasonic bonding, or welding.

27. The semiconductor device of claim 21, wherein the microballoons are pre-treated with an adhesion promoter.

28. The semiconductor device of claim 27, wherein the adhesion promoter is silane.

29. An optical-based sensor for determining the presence or concentration of an analyte in a medium, said sensor comprising:

an optically transmissive sensor body which functions as an optical wave guide, said sensor body having an outer surface surrounding said sensor body;

a radiation source in said sensor body which emits radiation within said sensor body, including;

a substantially transparent substrate,

a semiconductor layer deposited on a bottom surface of the substrate,

a plurality of bonding pads, coupled to the semiconductor layer, formed on the bottom surface of the substrate, and

a plurality of micro posts, formed on the bonding pads, for electrically connecting the light emitting diode to a printed circuit board;

an indicator element having an optical characteristic that is affected by the presence or concentration of an analyte, said indicator element being positioned on said sensor body to receive radiation that travels from said radiation source, and which transmits radiation into said sensor body; and

a photosensitive element located in said sensor body and positioned to receive radiation within the sensor body and which emits a signal responsive to radiation received from said indicator element.

30. The sensor of claim 29, further comprising an underfill layer, including a polymer and a filler, disposed between the bottom surface of the substrate and a top surface of the printed circuit board, to reduce water infiltration under the substrate.

31. The sensor claim 30, wherein the filler includes a plurality of microballoons and the polymer is cyanate ester.

32. The sensor of claim 30, wherein the filler is a light-scattering filler and the polymer is an optical epoxy.

33. The sensor of claim 30, wherein the underfill layer is about 70% by weight of polymer and about 30% by weight of filler.

34. The sensor of claim 31, wherein each microballoon has a diameter from about 2 μ

m to about 11 μ

m.

35. The sensor of claim 31, wherein each microballoon is an air-filled sphere having a diameter of about 11 μ

m and a wall thickness of about 1 μ

m.

36. The sensor of claim 29, further comprising a substantially transparent, hemispherical diffuser, mounted to a top surface of the radiation source substrate, to diffuse the light emitted through the top surface of the radiation source substrate.

37. The sensor of claim 36, wherein the diffuser includes titanium oxide to increase light reflectivity.

38. The sensor of claim 36, wherein the diffuser includes microballoons to increase light reflectivity.

39. The sensor of claim 31, wherein the light-scattering filler is titanium(IV) oxide and the optical epoxy is Epo-Tek 301-2.

40. The sensor of claim 30, wherein the microballoons are pre-treated with an adhesion promoter.

41. The sensor of claim 40, wherein the adhesion promoter is silane.

42. A method for mounting a light emitting diode to a printed circuit board in a flip chip orientation, comprising:

removing a reflective layer from a first surface of the light emitting diode;

bonding a micro post to each bonding pad on a second surface of the light emitting diode, the second surface being opposite the first surface;

bonding the micro posts to corresponding bonding pads on the printed circuit board so that the light emitting diode is mounted in a flip chip orientation; and

mounting a diffuser on the first surface of the light emitting diode to diffuse the light emitted through the first surface of the light emitting diode.