LIQUID COOLED LASER BAR ARRAYS INCORPORATING THERMAL EXPANSION MATCHED MATERIALS

Abstract

A laser diode array having a plurality of diode bars bonded by a hard solder to expansion matched spacers and mounted on a gas or liquid cooled heatsink. The spacers are formed of an aluminum/diamond composite, a silver/diamond composite or a silver/aluminum alloy/diamond composite material having a thermal expansion that closely matches that of the laser bars.

Claims

1. A laser bar array having a plurality of laser bars sandwiched between and soldered directly to spacers forming a laser bar/spacer sandwich, and the laser bar/spacer sandwich is mounted by solder with an intervening ceramic layer to a heat sink, wherein the spacers are foamed of an aluminum/diamond composite, a silver/diamond composite, or a silver-aluminum alloy/diamond composite material having a thermal expansion that closely matches that of the laser bars, and the heat sink includes an inlet hole and an outlet hole for passing a coolant through the heat sink, wherein the inlet and the outlet are connected via soft metal seals to a coolant fluid circulatory system; wherein the aluminum/diamond composite, the silver/diamond composite, or the silver/aluminum alloy/diamond composite material comprises 30-70 volume percent diamond and the balance comprises primarily aluminum, silver or silver-aluminum alloy, and; wherein the diamond particles have a maximum size of 500 microns.

2. The laser bar array of claim 1, wherein the aluminum/diamond composite comprises 40-70 volume percent diamond and the balance comprises primarily aluminum.

3. The laser bar array of claim 1, wherein the aluminum/diamond composite comprises 50-65 volume percent diamond and the balance comprises primarily aluminum.

4. The laser bar array of claim 1, wherein the silver/diamond composite comprises 30-60 volume percent diamond and the balance comprises primarily silver.

5. The laser bar array of claim 1, wherein the silver/diamond composite comprises 35-55 volume percent diamond and the balance comprises primarily silver.

6. The laser bar array of claim 1, wherein the silver-aluminum alloy/diamond composite comprises 35-65 volume percent diamond and the balance comprises primarily silver-aluminum alloy.

7. The laser bar array of claim 1, wherein the silver-aluminum alloy/diamond composite comprises 40-60 volume percent diamond and the balance comprises primarily silver-aluminum alloy.

8. The laser bar array of claim 1, wherein the diamond particles are relatively uniform in size.

9. The laser bar array of claim 1, wherein the diamond particles have a maximum size of 200 microns.

10. The laser bar array of claim 1, wherein the diamond particles have a maximum size of about 100 microns.

11. The laser bar array of claim 1, wherein the diamond particles are coated with a material selected from the group consisting of Cr, W, Mo, Co, Ti, Si, SiC, TIN, TiC, Ta and Zr.

12. The laser bar array of claim 1, wherein the solder comprises a hard, high temperature solder.

13. The laser bar array of claim 12, wherein the solder comprises a gold/tin hard, high temperature solder.

14. The laser bar array of claim 12, wherein the solder comprises a hard, high temperature gold/germanium solder.

15. The laser bar array of claim 1, wherein the laser bars are aligned end to end on the heat sink.

16. The laser bar array of claim 1, wherein the laser bars are aligned parallel to one another on the heat sink.

17. The laser bar array of claim 1, wherein the coolant comprises a gas or a liquid.

18. (canceled)

19. (canceled)

20. A laser bar array comprising: a plurality of laser bars sandwiched between and soldered directly to spacers forming a laser bar/spacer sandwich, and the laser bar/spacer sandwich is mounted by solder with an intervening electrical isolation layer to a heat sink, wherein the spacers are formed of an aluminum/diamond composite, a silver/diamond composite, or a silver-aluminum alloy/diamond composite material having a thermal expansion that closely matches that of the laser bars; and an inlet hole and an outlet hole formed in the heat sink for passing a coolant through the heat sink, wherein the inlet hole and the outlet hole are connected via soft metal seal attached thereto seals to a coolant circulatory system; wherein the aluminum/diamond composite, the silver/diamond composite, or the silver-aluminum alloy/diamond composite material comprises 30-70 volume percent diamond and the balance comprises primarily aluminum, silver or silver-aluminum alloy, and; wherein the diamond particles have a maximum size of 500 microns.

21. The laser bar array of claim 20, wherein the aluminum/diamond composite, the silver/diamond composite, or the silver-aluminum alloy/diamond composite material comprises greater than 50 volume percent diamond and the balance comprises primarily aluminum, silver or silver-aluminum alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Further features and advantages of the invention will be seen from the following detailed description, taken in conjunction with the accompanying drawings, wherein like numerals depict like parts, and wherein:

[0010] FIG. 1 is a side elevational view of a laser diode array assembly, and FIG. 1A is a prospective view of an individual laser bar array in accordance with one embodiment or the present invention; and

[0011] FIG. 2 is a top plan view of a laser diode array assembly, and FIG. 2A is a prospective view of a laser bar array in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION

[0012] The present invention provides laser diode array assembly with improved heat removal capability and reliability. More particularly, in accordance with the present invention, the laser bar array 12 includes spacer material 14 formed of an aluminum/diamond composite, a silver/diamond composite, or a silver/aluminum alloy/diamond composite material that has a thermal expansion that closely matches that of the laser bars 16. This permits the use of a hard solder and provides increased reliability. This array is then mounted on a heatsink or substrate with an intervening ceramic layer 28 to provide electrical isolation.

[0013] FIG. 1 and FIG. 1A illustrate a laser bar assembly 10 and laser bar array 12 in accordance with the first embodiment of the invention. The laser bar assembly comprises a plurality of laser diode bar arrays 12 having laser diode bars 16 aligned end to end on a heat sink or substrate 30. The laser diode bar arrays 12 are held in place on the substrate 30 by a hard solder layer 17.

[0014] Two holes 18, 20 for supplying a coolant are formed in substrate 30. One hole 18 is used as an inlet for coolant fluid while the other hole 20 is used as an outlet. Inlet 18 and outlet 20 are connected via conduits 22 and 24, respectively, to a coolant fluid (gas or liquid) circulatory system (not shown).

[0015] Laser bars 16 are formed of conventional laser diode materials. A feature and advantage of the present invention results from forming the spacer 14 from an aluminum/diamond composite, a silver/diamond composite or a silver/aluminum alloy/diamond composite material is that the spacer material has a thermal expansion that closely matches the thermal expansion of the laser bars 16. This reduces stress in the assembly and also permits the use of hard solder. Typically the aluminum/diamond composite or the silver/diamond composite material may comprise 30-70% by volume diamond depending on the composite. For aluminium/diamond, the composition is preferably 40-70% by volume diamond, more preferably 50-65% by volume diamond. For silver/diamond, the composition is preferably 30-60% by volume diamond, more preferably 35-55% by volume diamond. Preferably the diamond particles are relatively uniform in size and typically have a maximum size of about 500 microns, preferably less than 200 microns, more preferably less than 100 microns. If desired, the diamond particles may be coated, e.g., with a layer of Cr, W, Mo, Co, Ti, Si, SiC, TiN, TiC, Ta or Zr. The aluminum/diamond ratio, the silver/diamond ratio, or the silver/aluminum alloy/diamond ratio in the composite material is chosen to provide a material that has a thermal expansion that closely matches that of the laser bar material. As a result, the laser diode bars may be soldered directly to the spacers using a hard, high temperature solder such as a gold/tin solder or gold/germanium solder which are given as exemplary.

[0016] Referring to FIG. 2 and FIG. 2A, there is shown an alternative embodiment of the invention. In the FIG. 2/2A embodiment, the laser bars 16 are aligned parallel to one another in an array 32 on the substrate 34.

[0017] While the present invention has been described in connection with a macrochannel cooled laser array, it is not necessary that the substrate comprise a marcro-channel cooler. Rather, the heat sink may comprise a microchannel cooler, or an air cooled heat sink. Thus, the embodiments and examples set forth herein were presented in order to best explain the present invention and its practical application and to thereby enable those of ordinary skill in the art to make and use the invention. However, those of ordinary skill in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the teachings above without departing from the spirit and scope of the present invention.