Light emitting diode for harsh environments
View Patent ↗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.
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;
a plurality of micro posts, formed on the bonding pads, for electrically connecting the light emitting diode to a printed circuit board; and
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;
wherein the filler includes a plurality of microballoons and the polymer is cyanate ester.
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 , wherein the filler is a light-scattering filler and the polymer is an optical epoxy.
9. The light emitting diode of claim 1 , wherein the underfill layer is about 70% by weight of polymer and about 30% by weight of filler.
10. The light emitting diode of claim 1 , wherein each microballoon has a diameter from about 2 μm to about 11 μm.
11. The light emitting diode of claim 1 , wherein each microballoon is a gas-filled sphere having a diameter of about 11 μm and a wall thickness of about 1 μm.
12. The light emitting diode of claim 7 , wherein the diffuser includes titanium(IV) oxide to increase light reflectivity.
13. The light emitting diode of claim 7 , wherein the diffuser includes microballoons to increase light reflectivity.
14. The light emitting diode of claim 8 , wherein the light-scattering filler is titanium(IV) oxide.
15. The light emitting diode of claim 1 , wherein the microballoons are pre-treated with an adhesion promoter.
16. The light emitting diode of claim 15 , wherein the adhesion promoter is silane.
17. The light emitting diode of claim 7 , wherein the diffuser is a substantially transparent, hemispherical diffuser.
18. 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;
wherein the filler includes a plurality of gas-filled, glass microballoons and the polymer is cyanate ester.
19. The semiconductor device of claim 18 , wherein the underfill layer is about 70% by weight of epoxy and about 30% by weight of filler.
20. The semiconductor device of claim 18 , wherein each microballoon has a diameter from about 2 μm to about 11 μm, and a wall thickness of about 1 μm.
21. The semiconductor device of claim 18 , wherein the filler is a light-scattering filler and the polymer is an optical epoxy.
22. The semiconductor device of claim 21 , wherein the light-scattering filler is titanium(IV) oxide.
23. The semiconductor device of claim 18 , wherein the micro posts are bonded to the bonding pads using thermocompression bonding, thermosonic bonding, ultrasonic bonding, or welding.
24. The semiconductor device of claim 18 , wherein the microballoons are pre-treated with an adhesion promoter.
25. The semiconductor device of claim 24 , wherein the adhesion promoter is silane.
26. 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.
27. The sensor of claim 26 , 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.
28. The sensor claim 27 , wherein the filler includes a plurality of microballoons and the polymer is cyanate ester.
29. The sensor of claim 27 , wherein the filler is a light-scattering filler and the polymer is an optical epoxy.
30. The sensor of claim 27 , wherein the underfill layer is about 70% by weight of polymer and about 30% by weight of filler.
31. The sensor of claim 28 , wherein each microballoon has a diameter from about 2 μm to about 11 μm.
32. The sensor of claim 28 , wherein each microballoon is an air-filled sphere having a diameter of about 11 μm and a wall thickness of about 1 μm.
33. The sensor of claim 26 , 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.
34. The sensor of claim 33 , wherein the diffuser includes titanium oxide to increase light reflectivity.
35. The sensor of claim 33 , wherein the diffuser includes microballoons to increase light reflectivity.
36. The sensor of claim 28 , wherein the light-scattering filler is titanium(IV) oxide.
37. The sensor of claim 27 , wherein the microballoons are pre-treated with an adhesion promoter.
38. The sensor of claim 37 , wherein the adhesion promoter is silane.