Illuminator

• US 20040080939A1
• Filed: 10/22/2003
• Published: 04/29/2004
• Est. Priority Date: 04/23/2001
• Status: Active Grant

• Current Assignee: Lumos Solutions Limited
• Original Assignee: Plasma Ireland Limited
• Inventors: Kavanagh, Kieran, Braddell, Jules, Herbert, Anthony
• Granted Patent: US 6,995,405 B2
• Time in Patent Office: Days
• US Class Current: 362/240
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• 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 33/64 Heat extraction or cooling elements
• CPC Class Codes: H01L 33/648 the elements comprising fluids, e.g. heat-pipes

Abstract

An illuminator (1) comprises a substrate (2) supporting light source dies (4) driven via wire bonds (5). The substrate (2) comprises a silicon strip (20) in direct contact with a brass heat sink (3), thus providing for excellent heat transfer away from the die (4). Pads (10, 11, 12) of Ni, Ti, and Ag sub-layers support the die (4) and the wire bonds (5). These both provide electrical connections for the die (4) and also light reflection upwardly because the Ag sub-layers of the pads (10, 11, 12) are evaporated over a thermally grown oxide layer (21) on the Si (20). The oxide has a very high dielectric strength, thus maintaining excellent electrical insulating properties over a large voltage range.

Claims

1. An illuminator comprising light sources mounted on a substrate and an integrally moulded lens covering the light sources, characterised in that,

the substrate comprises a layer of semiconductor material and pads of conductive and reflective material overlying the semiconductor material,

said pads are electrically connected to the light sources to provide power, and

the substrate is mounted directly on a heat sink.

2. An illuminator as claimed in claim 1, wherein the moulded lens material extends completely over the substrate and a top portion of the heat sink to hermetically seal the substrate and the light sources.

3. An illuminator as claimed in claim 1, wherein the substrate comprises a layer of electrically-insulating material over the semiconductor material and the pads overlie said electrically-insulating layer.

4. An illuminator as claimed in claim 3, wherein said electrically-insulating material comprises an oxide of the semiconductor material.

5. An illuminator as claimed in claim 4, wherein the oxide is thermally grown and has a dielectric strength in excess of 5×

10⁶ V/cm.

6. An illuminator as claimed in claim 5, wherein the oxide comprises SiO₂.

7. An illuminator as claimed in claim 5, wherein the oxide depth is at least 2 microns.

8. An illuminator as claimed in any preceding claim, wherein the pads comprises reflective silver or gold.

9. An illuminator as claimed in any preceding claim, wherein the pads comprise a top sub-layer of a reflective metal over at least one adhesion sub-layer.

10. An illuminator as claimed in claim 9, wherein said adhesion sub-layer comprises Ti.

11. An illuminator as claimed in claim 9, wherein said adhesion sub-layer comprises Ni.

12. An illuminator as claimed in any of claim 9, wherein said sub-layers are deposited by evaporation over the oxide of the semiconductor material.

13. An illuminator as claimed in any of claim 8, wherein said sub-layers each have a depth in the range of 50 nm to 3 microns.

14. An illuminator as claimed in claim 1, wherein said light sources comprise semiconductor die placed and wire bonded on said tracks.

15. A method of producing an illuminator of the type comprising light sources mounted on a substrate and an integrally moulded lens covering the light sources, the method comprising the steps of:

providing a semiconductor material base,

depositing pads of electrically conductive and optically reflective material on the base to provide a substrate,

placing the light sources and electrical connectors on the pads of the substrate,

adhering the substrate at a lower surface of the base to a heat sink, and

moulding a lens over and around the substrate to hermetically seal the substrate and the light sources.

16. A method as claimed in claim 15, comprising the further step of growing an oxide layer on a surface of the base, and depositing the pads on the oxide layer.

17. A method as claimed in claim 16, wherein the oxide layer is grown to a depth of at least 2 microns.

18. A method as claimed in claim 15 wherein the base is of silicon material and the oxide is silicon dioxide.

19. A method as claimed in any of claim 15, wherein the pads are deposited by patterning with use of a photo-resist.

20. A method as claimed in any of claim 15, wherein the lens is moulded by placing the substrate upside-down in a mould cavity and filling the cavity until liquid lens material surrounds the substrate.

21. A method as claimed in claim 20, wherein the mould is sloped during filling, and the cavity is filled from the higher end.