A conduction-cooled semiconductor laser package structure for pumping and a method of packaging the same

Abstract

The application relates to a pumped conduction-cooled semiconductor laser package structure and a packaging method thereof. The package structure comprises an L-shaped heat dissipation heat sink, an AlN ceramic substrate is arranged on the vertical arm of the L-shaped heat dissipation heat sink, a multi-chip array matched with the AlN ceramic substrate is arranged above the AlN ceramic substrate; the multi-chip array comprises alternately connected tungsten copper heat sinks and mini chips, and the tungsten copper heat sinks and the mini chips are arranged in an array with one end aligned; a groove is arranged on the AlN ceramic substrate, and the groove and the positions and numbers of the mini chips correspond; a mounting fixing hole is arranged on the horizontal arm of the L-shaped heat dissipation heat sink. The application realizes side light emission through side welding insulation of the chips, and overcomes the problem that the existing devices packaged by centimeter bar are usually upward light emission. Meanwhile, the current used at the same time is small, and uneven heat dissipation is avoided.

Description

Technical Field

[0001] This invention relates to a conductive cooling semiconductor laser packaging structure and packaging method for pumping, belonging to the field of semiconductor laser array packaging. Background Technology

[0002] Conductive-cooled semiconductor lasers possess advantages such as small size, low cost, high efficiency, and long lifespan, and are mainly used in industrial pumping, materials processing, medical aesthetics, and scientific research and military applications. In pumping applications, they primarily focus on pumping crystals such as Nd:YAG and Nd:YVO4. However, in applications involving end-face and side-pumping of the crystal, the requirements for the laser's packaging structure and the light-emitting surface typically differ. Currently, common conduction-cooled semiconductor lasers are mainly packaged using centimeter bars, with AlN ceramic or SiC material used for insulation at the bottom, and then the entire assembly is packaged onto a heat sink. Lasers packaged in this way typically emit light upwards, with heat being conducted and concentrated at the bottom of the laser. Another common type is the CS conduction-cooled laser, where the laser bar emits light to one side. However, both of these lasers are based on high-power centimeter bar packages, which generally require low voltage and high current for laser driving. At the same time, due to the inherent light emission characteristics of semiconductor lasers, the output beam has asymmetry on the fast and slow axes, with a smaller divergence angle on the slow axis and a larger divergence angle on the fast axis, resulting in overall output beam quality deviation. Both of the aforementioned centimeter bar packaging structures suffer from this problem and cannot meet the pumping requirements of certain crystal facets.

[0003] Chinese patent document CN204190156U discloses a conductive cooling stacked semiconductor laser packaging structure. In this structure, a positive electrode connection block and a negative electrode connection block are welded to the two end faces of the stacked module chip in the stacking direction. Two non-contacting L-shaped conductive sheets are arranged symmetrically on the surface of the insulating heat sink, serving as the positive and negative electrodes respectively. The bottoms of the positive and negative electrode connection blocks are welded and fixed to the long parts of the two L-shaped conductive sheets, respectively. The stacked module corresponds to the area enclosed by these two L-shaped conductive sheets on the surface of the insulating heat sink. Mounting holes are provided on the short parts of the two L-shaped conductive sheets. This patent solves the problems of large size and poor system integration in existing packaging structures. However, devices based on centimeter-bar packaging have upward-emitting lasers, which cannot meet the structural requirements for partial side-emitting lasers.

[0004] Chinese patent document CN203747236U discloses a high-power semiconductor laser with a low thermal stress structure. This structure mainly comprises four layers stacked sequentially. The first layer is a heat sink serving as a positive electrode connection block, with a chip mounting area and an insulating area on its mounting plane. The second layer includes a semiconductor laser chip and an insulating sheet; the semiconductor laser chip is soldered to the chip mounting area, and the insulating sheet is mounted in the insulating area. The third layer is an electrode connection layer that conducts electricity. The fourth layer is a negative electrode connection block. In the electrode connection layer, the portion soldered to the semiconductor laser chip has a planar toothed structure to reduce thermal stress between the electrode connection layer and the chip. This portion maintains a gap with the negative electrode connection block, while other portions of the electrode connection layer are soldered to the negative electrode connection block. This patented structure features single-bar side-emitting light, with the lateral direction being the slow axis and the vertical direction being the fast axis. It can adapt to complex working environments and meet pumping requirements. However, to improve beam quality, an optical system needs to be added. For laser drivers in centimeter-bar packages, stable output with low voltage and high current is required, resulting in high overall cost. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a packaging structure and packaging method for a conduction-cooled semiconductor laser used for pumping.

[0006] The technical solution of the present invention is as follows:

[0007] A conductive cooling semiconductor laser packaging structure for pumping includes an L-shaped heat sink, an AlN ceramic substrate disposed on the vertical arm of the L-shaped heat sink, and a multi-chip array matching the AlN ceramic substrate disposed above the AlN ceramic substrate.

[0008] The multi-chip array includes alternating tungsten copper heat sinks and mini chips, which are arranged in an array with one end aligned; the AlN ceramic substrate has grooves, and the positions of the grooves and mini chips correspond to their number; the horizontal arm of the L-shaped heat sink has mounting holes.

[0009] According to a preferred embodiment of the present invention, electrode plates are further provided on both sides of the conductive cooling semiconductor laser packaging structure. The electrode plates are L-shaped, with one part connected to the multi-chip array and the other part connected to the L-shaped heat sink via electrode insulating sheets. The electrode insulating sheets ensure that external voltage can be effectively supplied to the multi-chip array through the electrode plates, but will not affect the L-shaped heat sink.

[0010] According to a preferred embodiment of the present invention, the number of tungsten copper heat sinks is at least three, and the number of mini chips is at least two.

[0011] According to a preferred embodiment of the present invention, the tungsten copper heat sink is of type W90Cu, with parameters of 188 W / (m*K), CTE of 6.5 ppm / K, and a thickness of 0.2–0.8 mm. This effectively neutralizes the stress caused during encapsulation and soldering.

[0012] According to a preferred embodiment of the present invention, the width of the mini chip is less than or equal to 3 mm, the output power of a single mini chip is 1 to 20 W, and the thickness is 115 to 120 μm.

[0013] According to a preferred embodiment of the present invention, the length of the tungsten copper heat sink is greater than the length of the mini chip, and an insulating layer is provided on the side of the tungsten copper heat sink that extends beyond the mini chip portion.

[0014] In this invention, the width of the groove on the AlN ceramic substrate is the same as the thickness of the mini chip, and the distance between adjacent grooves is the same as the thickness of the tungsten copper heat sink. The gap formed by the mini chip and the groove is mainly used for insulation of adjacent mini chips, while preventing solder from contacting the bottom of the mini chip.

[0015] According to a preferred embodiment of the present invention, a metal layer is provided on the upper surface of the AlN ceramic substrate; further, the metal layer is an Au layer with a thickness of 0.4–0.5 μm. The Au layer can form a stable alloy with the solder, thereby soldering the AlN ceramic substrate and the multi-chip array together.

[0016] According to a preferred embodiment of the present invention, the number of mounting holes is 1 to 3. The mounting holes are used for fixing the laser while also ensuring heat dissipation.

[0017] The packaging method for the above-mentioned conduction-cooled semiconductor laser packaging structure for pumping includes the following steps:

[0018] (1) Mini chips are cut according to the effective absorption area and energy requirements of the pumped crystal. Tungsten copper heat sinks are selected according to the chip spacing based on the heat dissipation requirements. Mini chips and tungsten copper heat sinks are alternately soldered together with high-temperature hard solder in a one-end aligned manner to obtain a multi-chip array.

[0019] (2) Place the multi-chip array on top of the AlN ceramic substrate. The groove position of the AlN ceramic substrate corresponds to the position of the mini chip. Solder the multi-chip array to the AlN ceramic substrate with lead-free solder. Then, install the AlN ceramic substrate with the multi-chip array onto the heat sink to form a conductive cooling semiconductor laser package structure. Finally, install electrode insulating sheets and electrode sheets on both sides of the conductive cooling semiconductor laser package structure. Fix the laser in the mounting holes to complete the package of the conductive cooling semiconductor laser for pumping.

[0020] According to a preferred embodiment of the present invention, the high-temperature hard solder is AuSn solder.

[0021] According to a preferred embodiment of the present invention, the lead-free solder is SnAgCu solder.

[0022] Beneficial effects:

[0023] 1. The conductive cooling semiconductor laser packaging structure for pumping provided by this invention replaces the centimeter-long bar with mini-chips, and then encapsulates multiple chips in series to form a multi-chip array. After insulation through an AlN ceramic substrate, it is packaged onto a heat sink. Structurally, the multi-die parallel output structure of the bar is changed to a multi-chip series output structure. In terms of driving, the driving requirement is changed from low voltage and high current to high voltage and low current, reducing driving requirements and costs. Simultaneously, the fast and slow axis directions of the output beam are interchanged, i.e., the lateral direction becomes the fast axis direction and the vertical direction becomes the slow axis direction, making the laser energy distribution more uniform in the lateral direction, improving the beam quality of the crystal output light, and meeting the application requirements of special structures.

[0024] 2. The conductive cooling semiconductor laser packaging structure for pumping provided by this invention achieves side-emitting light by soldering insulation through the side of the chip, overcoming the problem that existing devices packaged with centimeter bar strips typically emit light upwards, thus meeting the application requirements of pumping with different special structures. Simultaneously, the operating current is low, avoiding uneven heat dissipation.

[0025] 3. The conductive cooling semiconductor laser packaging structure for pumping provided by the present invention can cut mini chips of appropriate length according to the effective absorption area of ​​the rod / planar crystal to be pumped, and can also determine the number of chips according to the required pumping energy, which is flexible and convenient.

[0026] 4. The packaging method provided by this invention is simple to operate, has high manufacturing efficiency, and is suitable for industrial application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the package structure of the conductive cooling semiconductor laser used for pumping according to the present invention.

[0028] Figure 2 This is a schematic diagram of the multi-chip array structure of the present invention.

[0029] Figure 3 This is a schematic diagram of the AlN ceramic substrate structure of the present invention.

[0030] Figure 4 This is a front view of the conductive cooling semiconductor laser package structure used for pumping according to the present invention.

[0031] In the figure, 1. mini chip, 2. tungsten copper heat sink, 3. L-shaped heat sink, 4. AlN ceramic substrate, 5. positive electrode sheet, 6. electrode insulating sheet, 7. mounting hole, 8. light-emitting surface direction, 9. groove, 10. metal layer, 11. insulating layer, 12. negative electrode sheet. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0033] Example 1

[0034] like Figures 1-3 As shown, a conductive cooling semiconductor laser packaging structure for pumping includes an L-shaped heat sink 3, an AlN ceramic substrate 4 disposed on the vertical arm of the L-shaped heat sink 3, and a multi-chip array matching the AlN ceramic substrate 4 disposed above the AlN ceramic substrate 4.

[0035] The multi-chip array includes alternating tungsten-copper heat sinks 2 and mini-chips 1, arranged in an array with one end aligned. The AlN ceramic substrate 4 has grooves 9, the positions of which correspond to the number of mini-chips 1. The horizontal arm of the L-shaped heat sink 3 has a mounting hole 7. The mounting hole 7 is used for laser fixation while ensuring heat dissipation.

[0036] The tungsten copper heat sink 2 is of type W90Cu, with parameters of 188W / (m*K), CTE of 6.5ppm / K, and a thickness of 0.5mm. The mini-chip has a width of 2mm, a single mini-chip output power of 10W, and a thickness of 120μm. The width of the groove 9 is the same as the thickness of the mini-chip, and the distance between adjacent grooves 9 is the same as the thickness of the tungsten copper heat sink 2. The length of the tungsten copper heat sink 2 is greater than the length of the mini-chip 1, and an insulating layer 11 is provided on the side of the portion of the tungsten copper heat sink 2 that extends beyond the mini-chip 1. The gap formed between the mini-chip 1 and the groove 9 is mainly used for insulation between adjacent mini-chips 1, while also preventing solder from contacting the bottom of the mini-chip 1.

[0037] The conductive cooling semiconductor laser packaging structure also has positive electrode plates 5 and negative electrode plates 12 on both sides. Both positive electrode plates 5 and negative electrode plates 12 are L-shaped, with one part attached to the multi-chip array and the other part connected to the L-shaped heat sink 3 through electrode insulating plates 6. The electrode insulating plates 6 ensure that external voltage can be effectively supplied to the multi-chip array through the electrode plates, but will not affect the L-shaped heat sink 3.

[0038] The upper surface of the AlN ceramic substrate 4 is provided with a metal layer 10.

[0039] The light-emitting surface direction 8 of the conductive cooling semiconductor laser packaging structure provided in this embodiment can achieve side light emission, overcoming the problem that existing devices packaged with centimeter bar strips usually emit light upwards, and meeting the usage requirements of certain special structure pumps.

[0040] Example 2

[0041] The packaging method for the conduction-cooled semiconductor laser packaging structure for pumping described in Example 1 includes the following steps:

[0042] (1) Mini chips are cut according to the effective absorption area and energy requirements of the pumped crystal. Tungsten copper heat sinks are selected according to the chip spacing based on the heat dissipation requirements. Mini chips and tungsten copper heat sinks are alternately welded with AuSn solder, with one end aligned. After welding, mini chips and tungsten copper heat sinks are arranged in an array to obtain a multi-chip array.

[0043] (2) Place the multi-chip array on top of the AlN ceramic substrate. The groove position of the AlN ceramic substrate corresponds to the position of the mini chip. Solder the multi-chip array to the AlN ceramic substrate with SnAgCu solder. Then, install the AlN ceramic substrate with the multi-chip array onto the heat sink to form a conductive cooling semiconductor laser package structure. Finally, install electrode insulating sheets and electrode sheets on both sides of the conductive cooling semiconductor laser package structure. Fix the laser on the mounting holes to complete the package of the conductive cooling semiconductor laser for pumping.

[0044] Example 3

[0045] like Figure 4 As shown, a conductive cooling semiconductor laser packaging structure for pumping is described in Embodiment 1, except that the number of mounting holes 7 is two.

[0046] Example 4

[0047] A conductive cooling semiconductor laser packaging structure for pumping is provided, as described in Example 1, except that the metal layer 10 is an Au layer with a thickness of 0.5 μm. The Au layer can form a stable alloy with solder, bonding the AlN ceramic substrate and the multi-chip array together via solder.

[0048] Example 5

[0049] A conductive cooling semiconductor laser packaging structure for pumping, the structure is as described in Example 1, except that the tungsten copper heat sink 3 has a thickness of 0.3 mm, the mini chip has a width of 3 mm, the output power of a single mini chip is between 20 W, and the thickness is 115 μm.

[0050] Comparative Example

[0051] Chinese patent document CN204190156U discloses a conductive cooling stacked semiconductor laser packaging structure.

[0052] Table 1 shows a parameter comparison between the comparative example and Example 1. As can be seen from Table 1, the performance of each parameter in Example 1 is better than that of the comparative example. Example 1 can achieve side-emitting light. Furthermore, by changing the multi-chip parallel output structure of the bar to a multi-chip series output structure, the low-voltage, high-current driving requirement is changed to a high-voltage, low-current driving requirement. At the same time, the fast and slow axis directions of the output beam are interchanged, that is, the lateral direction becomes the fast axis direction and the vertical direction becomes the slow axis direction. This makes the laser energy more uniformly distributed in the lateral direction, improves the beam quality of the crystal output light, and can meet the application requirements of special structures.

[0053] Table 1: Performance Comparison between Comparative Example and Example 1

[0054]

Claims

1. A conduction-cooled semiconductor laser package structure for pumping, characterized by, The L-shaped heat dissipation heat sink is provided with an AlN ceramic substrate on the vertical arm, and a multi-chip array matching the AlN ceramic substrate is arranged above the AlN ceramic substrate. The multi-chip array comprises alternating tungsten-copper heat sinks and mini-chips arranged in an end-aligned array; the AlN ceramic substrate is provided with grooves corresponding in position and number to the mini-chips; the horizontal arm of the L-shaped heat dissipation heat sink is provided with mounting fixing holes. The conductive cooling semiconductor laser package structure is further provided with electrode pieces on both sides, the electrode pieces are L-shaped, one part is connected with the multi-chip array, and the other part is connected with the L-shaped heat dissipation heat sink through an electrode insulation piece; the number of tungsten-copper heat sinks is at least 3, and the number of mini-chips is at least 2. The conductive cooling semiconductor laser package structure for pumping emits light from the side, realizes fast-axis transverse and slow-axis longitudinal conversion through side light emission, makes the energy distribution uniform, and improves the beam quality. The packaging method of the conductive cooling semiconductor laser package structure for pumping comprises the following steps: (1) According to the effective absorption area and energy demand of the pumped crystal, mini-chips are cut, and tungsten-copper heat sinks are selected according to the heat dissipation requirement; the mini-chips and tungsten-copper heat sinks are alternately welded together in an end-aligned form by high-temperature hard solder to obtain a multi-chip array; (2) The multi-chip array is arranged above the AlN ceramic substrate, the groove position of the AlN ceramic substrate corresponds to the position of the mini-chip, the multi-chip array is welded to the AlN ceramic substrate by lead-free solder, then the AlN ceramic substrate with the multi-chip array is installed on the heat dissipation heat sink to form a conductive cooling semiconductor laser package structure, finally, the electrode insulation piece and the electrode piece are installed on both sides of the conductive cooling semiconductor laser package structure, and the laser is fixed on the mounting fixing hole to complete the packaging of the conductive cooling semiconductor laser for pumping.

2. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The model of the tungsten-copper heat sink is W90Cu, the parameter is 188W / (m*K), the CTE is 6.5ppm / K, and the thickness is 0.2~0.8mm.

3. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The width of the mini-chip is less than or equal to 3mm, the output power of a single mini-chip is 1~20W, and the thickness is 115~120μm.

4. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The length of the tungsten-copper heat sink is greater than the length of the mini-chip, and an insulation layer is arranged on the side of the part of the tungsten-copper heat sink longer than the mini-chip.

5. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The upper surface of the AlN ceramic substrate is provided with a metal layer.

6. The conduction-cooled, pumped semiconductor laser package structure of claim 5, wherein, The metal layer is an Au layer with a thickness of 0.4~0.5μm.

7. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The number of mounting fixing holes is 1~3.

8. The conduction-cooled, pumped semiconductor laser package structure of claim 1, wherein, The high-temperature hard solder is AuSn solder, and the lead-free solder is SnAgCu solder.

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