Low stress heatsink and optical system

• US 5,848,082 A
• Filed: 08/11/1995
• Issued: 12/08/1998
• Est. Priority Date: 08/11/1995
• Status: Expired due to Fees

• Current Assignee: SDL Inc (RWS Holdings Plc)
• Original Assignee: SDL Inc (RWS Holdings Plc)
• Inventors: Shum, Frank T. C.
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Wise, Robert E.
• Application Number:
  US08/513,695
• Time in Patent Office: 1,215 Days
• Field of Search: 257/712, 257/713, 257/720, 165/67, 165/68, 372/36
• US Class Current: 372/36
• CPC Class Codes: G02B 6/4204 the coupling comprising intermediate optical elements, e.g. lenses, holograms encapsulated active devices H01S5/02208, H01L33/52
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/4207 with optical elements reducing the sensitivity to optical feedback anti-reflection devices specially adapted for lasers, see H01S3/0064
• CPC Class Codes: G02B 6/4225 by a direct measurement of the degree of coupling, e.g. the amount of light power coupled to the fibre or the opto-electronic element
• CPC Class Codes: G02B 6/4257 having a supporting carrier or a mounting substrate or a mounting plate G02B6/3648 takes precedence
• CPC Class Codes: G02B 6/4269 with heat sinks or radiation fins
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches
• CPC Class Codes: H01S 5/024 Arrangements for thermal management
• CPC Class Codes: H01S 5/02415 by using a thermo-electric cooler [TEC], e.g. Peltier element
• CPC Class Codes: H01S 5/02469 Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC
• CPC Class Codes: H01S 5/02484 Sapphire or diamond heat spreaders
• CPC Class Codes: H01S 5/50 Amplifier structures not provided for in groups H01S5/02 - H01S5/30

Abstract

A heatsink and an optical system are provided for use in conjunction with a dissipating semiconductor or electronic device, such as a light source, that generate a large amount of heat and is required to be cooled for optimum performance. The light source may be a laser diode or laser array or bar and is generally mounted on the heatsink with other optical components, such as collimating and focusing lenses, isolators or terminal ends of optical fibers, for coupling the output beam of the light source in aligned relation to these optical elements. Because of the higher temperature operation of such light sources, the heat generated causes thermal expansion of mechanically connected structures, such as between the heatsink for supporting the light source and its associated submount and an underlying support, usually a cooler. Because of the differences in thermal expansion rates between these different structures comprised of materials of different coefficients of expansion, the preset or subsequently adjusted alignment of the output beam with these associated optical components will become misaligned due to mechanical warpage and stress deflection of the heatsink. The disclosed heatsink is designed to provide high efficient heat transfer from the heat dissipated from the device while concurrently absorbing mechanical stresses due to differences in the thermal heat transfer coefficients between the heatsink and the underlying support so that component misalignment does not occur.

Claims

1. A heatsink comprising:

a body of high thermal, heat transfer capacity having a first surface for supporting a semiconductor device;

said body having a second surface for heat transfer coupling to a third surface of a supporting member;

a first leg structure integral with and spatially disposed on said body second surface;

said first leg structure formed along at least a portion of said second surface along a longitudinal length thereof and comprising a plurality of spatially disposed legs for substantial heat transfer via its leg ends in contact with said third surface;

said first leg structure supporting said heatsink body on said third surface and having sufficient flexibility to bend to compensate for thermal stress deflection and warpage caused by the thermal expansion of said heatsink body as the temperature of the heatsink changes so that said heatsink body is not subject thermal strain and stress and, correspondingly, said semiconductor device is not subjected to thermal stress deflection and warpage;

said plurality of spatially disposed legs of said first leg structure comprise plural, spatially disposed fins having a width extending transversely of the longitudinal length of the heatsink body providing for heat transfer via ends of said fins to said third surface; and

a second leg structure spatially disposed from said first leg structure on said second surface, said second leg structure having at least one fin having a transverse width smaller than the transverse width of said plural fins.

2. The heatsink of claim 1 wherein said second leg structure comprises two or more of said fin.

3. The heatsink of claim 1 wherein said plurality of spatially disposed legs of said leg structure comprise a plurality of spatially disposed fins extending for substantially a full width of the heatsink.

4. The heatsink of claim 1 wherein said supporting member is a thermal electric cooler.

5. The heatsink of claim 1 wherein said semiconductor device is a light source, laser diode, flared gain device, MOPA device, laser diode array, single or multiple laser bar, optical transceiver, optical integrated circuit, semiconductor chip or integrated circuit chip.

6. The heatsink of claim 1 wherein said semiconductor device is a resonator having a gain portion that permits a diverging phase front for light traveling in said resonator.

7. The heatsink of claim 1 wherein said supporting member comprises a thermo-electric element.

8. A heatsink comprising:

a body of high thermal, heat transfer capacity having a first surface for supporting a semiconductor device;

said body having a second surface for heat transfer coupling to a third surface of a supporting member;

a first leg structure integral with and spatially disposed on said body second surface;

said first leg structure formed along at least a portion of said second surface along a longitudinal length thereof and comprising a plurality of spatially disposed legs for substantial heat transfer via its leg ends in contact with said third surface;

said first leg structure supporting said heatsink body on said third surface and having sufficient flexibility to bend to compensate for thermal stress deflection and warpage caused by the thermal expansion of said heatsink body as the temperature of the heatsink changes so that said heatsink body is not subject thermal strain and stress and, correspondingly, said semiconductor device is not subjected to thermal stress deflection and warpage;

a second leg structure spatially disposed from said first mentioned leg structure on said second surface, a belly portion comprising an integral part of said body portion formed between said first and second leg structure, said belly portion not in engagement with said third surface and aiding in the prevention of stress deflection of said heatsink body so that deflection tendencies of the heatsink are absorbed in said leg structures.

9. The heatsink of claim 8 comprising a heatsink material of high thermal conductivity.

10. The heatsink of claim 9 wherein said heatsink material is copper.

11. A heatsink comprising:

a body of high thermal, heat transfer capacity having a first surface for supporting a semiconductor device;

said body having a second surface for heat transfer coupling to a third surface of a supporting member;

a first leg structure integral with and spatially disposed on said body second surface;

said first leg structure formed along at least a portion of said second surface along a longitudinal length thereof and comprising a plurality of spatially disposed legs for substantial heat transfer via its leg ends in contact with said third surface;

said first leg structure supporting said heatsink body on said third surface and having sufficient flexibility to bend to compensate for thermal stress deflection and warpage caused by the thermal expansion of said heatsink body as the temperature of the heatsink changes so that said heatsink body is not subject thermal strain and stress and, correspondingly said semiconductor device is not subjected to thermal stress deflection and warpage;

said heatsink comprising a diamond faceplate formed on a base of high thermal conductivity.

12. The heatsink of claim 11 wherein said base is comprised of copper.

13. A heatsink comprising:

a body having high thermal heat transfer and low thermal resistance characteristics,

a first surface of said body portion for supporting a high temperature operating semiconductor device or the like,

a second surface of said body portion having

a first section with a plurality of adjacently extending fins spatially formed along and integral with said second surface,

a second section having at least one extending fin integral with said second surface,

said at least one fin spatially separated from said plural fins on said second surface,

said first and second fins absorbing the thermal deflection imposed on said heatsink body due to changes in its body temperature cause by said semiconductor device, and

a third section formed between said first and second sections having a belly portion integral with said body and extending between said first and second sections functioning as a stiffening element for said heat heatsink body, ends of said fins extending away from said second surface beyond a bottom surface of said belly portion for engagement with a third surface.

14. A heatsink comprising:

a body having high thermal heat transfer and low thermal resistance characteristics,

a first surface of said body portion for supporting a high temperature operating semiconductor device or the like,

a second surface of said body portion having

a first section with a plurality of adjacently extending fins spatially formed along and integral with said second surface,

a second section having at least one extending fin integral with said second surface,

said at least one fin spatially separated from said plural fins on said second surface,

said first and second fins absorbing the thermal deflection imposed on said heatsink body due to changes in its body temperature cause by said semiconductor device, and

said plural fins in said first bottom section extend for a full width of the heatsink to provide for maximum heat transfer via said fins, said at least one fin having a smaller width compared to the width of said plural fins.

15. The heatsink of claim 14 wherein said at least one fin further comprises several of such fins with smaller widths compared to the width of said plural fins.

16. A heatsink comprising:

a body having high thermal heat transfer and low thermal resistance characteristics,

a first surface of said body portion for supporting a high temperature operating semiconductor device or the like,

a second surface of said body portion having

a first section with a plurality of adjacently extending fins spatially formed along and integral with said second surface,

a second section having at least one extending fin integral with said second surface,

said at least one fin spatially separated from said plural fins on said second surface,

said first and second fins absorbing the thermal deflection imposed on said heatsink body due to changes in its body temperature cause by said semiconductor device,

said heatsink body comprises copper.

17. A low stress heatsink comprising:

a heat transfer member having a first substantially planar surface for supporting a heat generating device, said heat generating device in axial alignment with at least one other component in a given direction, said component also supported relative to said body first surface;

a supporting member;

said heat transfer member having a second surface opposite of said first surface supported on and secured to said supporting member;

the coefficient of thermal expansion of said heat transfer member different than that of said supporting member such that when the heatsink is subjected to elevated heat transfer conditions, said first surface undergoes thermal stress warpage along said given direction to become sufficiently nonplanar to cause misalignment of said axially aligned device and component;

the improvement comprising a leg structure integral with said heat transfer member along at least a portion of said second surface extending from said second surface to said supporting member for deforming in said given direction when the heatsink is subjected to elevated heat transfer conditions due to said thermal expansion difference preventing the occurrence of thermal stress warpage at said first surface so that said axial alignment is maintained.

18. The low stress heatsink of claim 17 wherein in said leg structure comprises a plurality of spatially disposed fins formed along at least a portion of said second surface, said fins having major planar extents aligned transverse to said given direction.

19. The low stress heatsink of claim 17 further comprising a second leg structure integral with said heat transfer member and spatially disposed from the first mentioned leg structure on said second surface along at least a portion thereof, said second leg structure extending from said second surface to said supporting member, said first and second spatially disposed leg structures supporting said heat transfer member on said supporting member.

20. The low stress heatsink of claim 19 wherein in said leg structures comprise a plurality of legs wherein the number of legs for said first leg structure is greater than the number of legs for said second leg structure.

21. The low stress heatsink of claim 19 further comprising a bulk belly portion disposed between said first and second spatially disposed leg structures extending toward said supporting member but not in engagement therewith.

22. The low stress heatsink of claim 21 wherein in said leg structures comprises a plurality of spatially disposed fins formed along at least a portion of said second surface, said fins having major planar extents aligned transverse to said given direction, said first leg structure comprising a larger number of fins than said second leg structure.

23. The low stress heatsink of claim 17 wherein said at least one other component is an optical device and said heat generating device is a semiconductor laser having a light output in optical alignment with said optical device.

24. The low stress heatsink of claim 17 wherein said supporting member comprises a thermoelectric element.

25. The low stress heatsink of claim 17 wherein said heat generating device comprises a semiconductor device.

26. The low stress heatsink of claim 25 wherein said semiconductor device is a light source, laser diode, flared gain device, MOPA device, laser diode array, single or multiple laser bar, optical transceiver, optical integrated circuit, semiconductor chip or integrated circuit chip.

27. The low stress heatsink of claim 25 wherein said semiconductor device is a resonator having a gain portion that permits a diverging phase front for light traveling in said resonator.