DPL linear array laser dopa strip collinear packaging method

Abstract

The application belongs to the technical field of semiconductor laser package, and relates to a DPL linear array laser dopa strip collinear package method, which comprises the following steps: welding a sub-module through a first solder; setting a ceramic substrate with a high-wettability gold-plated area and a low-wettability non-gold-plated area on the upper surface, and the non-gold-plated area comprises a groove located directly below the laser dopa strip; using a packaging clamp with a positioning block to limit the sub-module at equal intervals, and welding through a second solder, so that the sub-module is arranged collinearly and at equal intervals through the wettability difference between the high-wettability gold-plated area and the low-wettability non-gold-plated area and the mechanical limiting of the positioning block; and setting a heat sink with a groove structure, and welding the ceramic substrate module in the groove of the heat sink through a third solder. Through the cooperation of wettability self-alignment and mechanical limiting, the collinear precision and the interval precision of the dopa strip package are improved, and the risk of solder overflow and short circuit is reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser packaging technology, and relates to a method for collinear packaging of DPL linear array lasers with multiple bar strips. Background Technology

[0002] The core pump source of a diode-pumped solid-state laser (DPL) is a linear array of semiconductor lasers, typically composed of multiple laser bars arranged at equal intervals along a straight line. The spatial positioning accuracy between the emission points of these laser bars directly determines the uniformity of the energy distribution of the pump spot, thus affecting the photoelectric conversion efficiency and beam quality of the DPL system.

[0003] Currently, typical DPL linear array laser multibar packaging methods employ a two-stage solder system. The process involves: first, using a first solder to weld tungsten-copper electrodes to a ceramic substrate to form a ceramic substrate module; then, using the same first solder, welding laser bars onto the ceramic substrate module to form sub-modules; and finally, using a second solder with a lower melting point to weld all sub-modules and auxiliary materials to the heat sink surface in a single process. However, when multiple sub-modules are welded to the heat sink or ceramic substrate surface in the same welding step, the surface tension and flow pull generated by the molten solder can disturb the solder layer of the initially aligned sub-modules, causing slight misalignment of the preceding sub-modules. This accumulates over time, resulting in significant collinearity deviations. Simultaneously, the lack of differentiated wetting treatment on the heat sink and ceramic substrate surfaces allows molten solder to flow randomly under unconstrained conditions, climbing to the sidewalls of the laser bars, creating a short-circuit risk. Uneven solder distribution further exacerbates the deterioration of collinearity and axial spacing accuracy due to the pulling effect of the laser bars. Summary of the Invention

[0004] The purpose of this invention is to provide a collinear packaging method for DPL linear array lasers with multiple bar lines, in order to solve the technical problems in the prior art that lead to large cumulative collinearity errors due to solder disturbance, short circuits caused by disordered solder flow, and precision degradation.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for collinear packaging of DPL linear array laser multibar strips, comprising the following steps: Step S1: Weld at least one laser bar to a tungsten-copper electrode using a first solder to form a submodule; Step S2: Set up a ceramic substrate, which is used to support multiple sub-modules. The upper surface of the ceramic substrate has a high wettability gold-plated area and a low wettability non-gold-plated area. The low wettability non-gold-plated area includes a groove located directly below the laser bar. The groove is used to guide and coarsely position the sub-modules when they are placed. Place multiple sub-modules on the ceramic substrate and use a packaging jig with positioning blocks to limit the sub-modules at equal intervals. Solder them with a second solder with a melting point lower than the first solder. During the soldering process, based on the guidance and coarse positioning, the wettability difference between the high wettability gold-plated area and the low wettability non-gold-plated area, as well as the mechanical limiting of the positioning blocks, and in coordination with the mechanical limiting of the positioning blocks, achieve the collinear and equally spaced arrangement of the multiple sub-modules on the ceramic substrate to form a ceramic substrate module. Step S3: Set up a heat sink, which is used to weld to the ceramic substrate module by a third solder. The upper surface of the heat sink has a groove structure. Weld the ceramic substrate module to the groove structure of the heat sink by a third solder with a melting point lower than that of the second solder.

[0006] Preferably, the width of the groove on the upper surface of the ceramic substrate is 10 to 20 micrometers larger than the bottom width of the laser bar, and its depth is 30% to 40% of the thickness of the laser bar.

[0007] Preferably, the high wettability gold-plated area is a region with a gold-plated layer on its surface, and the low wettability non-gold-plated area is a region of exposed ceramic surface.

[0008] Preferably, the packaging fixture includes a side plate and a positioning block, the positioning block having an L-shaped structure including a long segment and a short segment; in step S2, one side of the sub-module is attached to the side plate, the opposite side of the sub-module attached to the side plate is attached to the inner side of the long segment, and the short segment is located between two adjacent sub-modules.

[0009] Preferably, the melting point of the first solder is 270°C to 300°C, the melting point of the second solder is 200°C to 230°C, and the melting point of the third solder is 110°C to 170°C.

[0010] Preferably, the first solder is a gold-tin alloy, the second solder is a silver-copper alloy or a tin-silver-copper alloy, and the third solder is an indium-based alloy.

[0011] Preferably, the groove structure on the upper surface of the heat sink matches the bottom contour of the ceramic substrate.

[0012] Preferably, the submodule formed in step S1 includes a laser bar, two layers of first solder located on the upper and lower surfaces of the laser bar, and two tungsten copper electrodes welded to the upper and lower surfaces of the laser bar by the first solder.

[0013] Beneficial effects Compared to existing technologies, on the one hand, the highly wettable gold-plated area and the low-wetting non-gold-plated area containing the groove on the surface of the ceramic substrate together form a difference in the wettability spatial structure. When the second solder melts, the solder preferentially wets and spreads in the gold-plated area. The resulting surface tension drives the tungsten-copper electrode at the bottom of the contacting sub-module to move towards the target position, forming a self-alignment effect. At the same time, the groove directly below the laser bar provides a receiving space for the bottom of the laser bar, and its non-wetting surface effectively prevents the solder from climbing up to the sidewall and light-emitting surface of the laser bar, preventing short circuits. On the other hand, the positioning block of the packaging fixture physically and precisely defines the axial spacing between adjacent sub-modules. These two work together: wettability self-alignment provides "active" positioning power, while the fixture positioning block provides "passive" precision limiting. Both are indispensable and together achieve collinearity and equal spacing accuracy. Simultaneously, the melting points of the first, second, and third solders decrease sequentially, ensuring that the temperature of subsequent soldering steps remains lower than the melting point of the previous solder. This prevents the solidified solder layer from remelting and shifting position, thus maintaining the high-precision alignment achieved in step S2. The grooved structure of the heat sink in step S3 provides guidance and positioning for the entire ceramic substrate module, further preventing displacement during final integration. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of a submodule of the present invention; Figure 2 This is a schematic diagram of the three-gradient solder welding structure of the present invention; Figure 3 This is a schematic diagram of the welding fixture of the present invention; Figure 4 This is a schematic diagram of the structure of the ceramic substrate of the present invention; Figure 5 This is a schematic diagram of the welding structure of the packaging fixture of the present invention; Figure 6 This is a schematic diagram of the DPL linear array laser after packaging according to the present invention. Figure 7 This is a schematic diagram of the process flow of the present invention; Figure 8 This is a schematic diagram illustrating the method for measuring collinearity and axial spacing according to the present invention.

[0015] Figure label: 1. Tungsten copper electrode; 2. Laser bar; 3. First solder layer; 4. Second solder layer; 5. Ceramic substrate; 6. Third solder layer; 7. Heat sink; 8. Welding fixture; 9. Submodule; 10. High wettability gold-plated area; 11. Low wettability non-gold-plated area; 12. Side plate; 13. Positioning block. Detailed Implementation

[0016] The technical solutions of this application will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0017] like Figure 7 As shown, this embodiment provides a multi-bar collinear packaging method for a DPL linear array laser. Along the heat conduction path from the laser bar 2 to the heat sink 7, a three-stage solder system with progressively decreasing melting points is employed. Specific materials can be selected as follows: the first solder is a gold-tin alloy (e.g., Au80Sn20, melting point approximately 280°C); the second solder is a tin-silver-copper alloy (e.g., SAC305, melting point approximately 217°C) or a silver-copper alloy; and the third solder is an indium-based alloy (e.g., In97Ag3, melting point approximately 143°C). The soldering sequence strictly follows the order of decreasing melting points.

[0018] The packaging process is as follows: Step 1: Submodule welding.

[0019] like Figure 1 and Figure 3 As shown, the materials are stacked sequentially in the following order using welding fixture 8: tungsten-copper electrode 1, first solder layer 3, laser bar 2, first solder layer 3, and tungsten-copper electrode 1. Uniform, minute pressure is applied to the topmost tungsten-copper electrode 1 to ensure close contact between the layers. The entire assembly is heated to approximately 300°C (approximately 20°C above the melting point of the first solder) to complete eutectic welding, forming a submodule 9. This step simultaneously welds both ends of the laser bar 2, ensuring its initial parallelism.

[0020] Step 2: Positioning and welding of the ceramic substrate.

[0021] First, an aluminum nitride ceramic substrate 5 is set up to support multiple sub-modules 9. For example... Figure 4As shown, the upper surface of the ceramic substrate 5 is patterned with a high-wetness gold-plated area 10 and a low-wetness non-gold-plated area 11 through sputtering gold plating, photolithography, and etching processes. The high-wetness gold-plated area 10 corresponds to the preset welding position of each tungsten copper electrode 1 and is a gold-plated layer; the low-wetness non-gold-plated area 11 is an exposed aluminum nitride ceramic surface, and a groove is formed by etching in the area directly below the laser bar 2. The groove is used to guide and coarsely position the submodule 9 when it is placed, so that it can achieve preliminary alignment with the target position. The width of the groove is 15 micrometers larger than the bottom width of the laser bar 2, and the depth is 35% of the thickness of the laser bar 2. The lower surface of the ceramic substrate 5 is a full gold-plated layer for reliable welding with the third solder.

[0022] Next, a second solder layer 4 (such as a solder sheet) is pre-formed on the high wettability gold plating area 10 of the ceramic substrate 5. Multiple sub-modules 9 obtained in step one are then placed onto the ceramic substrate 5. Subsequently, as... Figure 5 As shown, a packaging fixture is used for positioning. The packaging fixture includes a side plate 12 and an L-shaped positioning block 13, which includes a long segment and a short segment. One side of the sub-module 9 is attached to the side plate 12, the inner side of the long segment of the positioning block 13 is attached to the opposite side of the sub-module 9, and the short segment of the positioning block 13 is located between two adjacent sub-modules 9, with its thickness precisely corresponding to the designed axial spacing, thereby achieving equidistant positioning of the sub-modules 9.

[0023] The assembled device is heated to approximately 232°C (about 15°C above the melting point of the second solder), melting the second solder layer 4. Because the molten solder has excellent wettability to the gold plating layer but almost no wettability to the exposed aluminum nitride ceramic, driven by the surface tension difference and guided by the groove for guidance and coarse positioning, the tungsten copper electrode 1 at the bottom of submodule 9, along with the entire submodule 9, is "pulled" to the center of the highly wettable gold plating area 10, achieving active self-alignment. Simultaneously, the short rigid section of the positioning block 13 rigidly limits the axial spacing between adjacent submodules 9, ensuring that the self-alignment process does not cause spacing deviation. The groove directly below the laser bar 2 accommodates the bottom of the laser bar 2 and, due to its non-wetting properties, prevents the solder from climbing upwards. After cooling, multiple submodules 9 are arranged with high precision, collinearity, and equal spacing on the ceramic substrate 5, forming a ceramic substrate module.

[0024] Step 3: Welding of heat sink and auxiliary materials.

[0025] A heat sink 7 is provided for welding to the ceramic substrate module via the third solder layer 6. Its upper surface is precision-machined with a groove structure, the groove contour of which matches the bottom dimensions of the ceramic substrate 5. For example... Figure 2As shown, a third solder layer 6 (such as an indium-based solder sheet) is pre-placed in the groove of the heat sink 7, and necessary auxiliary materials (such as electrode connecting pieces) are also pre-placed. The ceramic substrate module completed in step two is placed into the groove of the heat sink 7, with the sidewalls of the groove acting as a guide and physical constraint. The overall temperature is raised to approximately 158°C (approximately 15°C above the melting point of the third solder) to complete the final soldering. Because this temperature is much lower than the melting points of the first and second solders, the previously obtained high-precision collinear alignment is completely preserved.

[0026] Step 4: Cooling, cleaning, and testing.

[0027] The packaged module was cooled to room temperature and then subjected to ultrasonic cleaning and optical inspection. The resulting... Figure 6 The DPL linear array laser shown was tested for photoelectric performance and optical homogenization effect.

[0028] To verify the technical effectiveness of the present invention, a comparative experiment was conducted. Three sets of DPL linear array laser samples were encapsulated using both the existing technology method described in the background section and the method of this embodiment, and their collinearity and axial spacing were measured under the same conditions.

[0029] 1. Measurement method: Figure 8 The laser bar arrangement uses one side of the chip as the reference zero line.

[0030] Collinearity is decomposed into: overall collinearity (using point A as the reference point, measuring the tolerance values ​​between point A and points C, E, and G, and measuring the tolerance values ​​in the Y-axis direction), and individual parallelism (using points A, C, E, and G as reference points, measuring the tolerance values ​​between points B, D, E, and H, and measuring the tolerance values ​​in the Y-axis direction).

[0031] Axial spacing: The standard value for axial spacing is 5mm (measured in the X-axis direction tolerance).

[0032] 2. Measurement data: Table 1 shows the test data (unit: μm) for DPL lasers packaged using existing solutions. Based on Table 1 above, the existing solution for packaging DPL lasers has the following tolerances: overall collinearity tolerance ±160µm; individual parallelism tolerance ±60µm; and axial spacing tolerance ±260µm.

[0033] Table 2 shows the test data (unit / µm) for DPL lasers packaged using existing solutions. Based on Table 2 above, the DPL laser packaged in this invention has the following tolerances: overall collinearity tolerance ±20µm; individual parallelism tolerance ±5µm; and axial spacing tolerance ±50µm.

[0034] 3. Data Analysis Comparative experimental results strongly demonstrate that the method provided in this embodiment reduces the overall collinearity tolerance from ±160μm to ±20μm, the individual parallelism tolerance from ±60μm to ±5μm, and the axial spacing tolerance from ±260μm to ±50μm, significantly improving packaging accuracy. This is attributed to: the one-time soldering of submodule 9 in step S1 ensuring initial parallelism and reducing cumulative errors; the synergistic effect of wettability self-alignment and the mechanical limiting of the short segment of positioning block 13 in step S2 precisely controlling the collinearity and parallelism in the Y-axis direction, as well as the axial spacing in the X-axis direction; and the three-stage solder system in step S3 ensuring that the accuracy of the preceding soldering stage is not compromised by subsequent processes.

[0035] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for collinear packaging of DPL linear array laser strips with multiple bar lengths, characterized in that, Includes the following steps: Step S1: Weld at least one laser bar to a tungsten-copper electrode using a first solder to form a submodule; Step S2: Set up a ceramic substrate, which is used to support multiple sub-modules. The upper surface of the ceramic substrate has a high wettability gold-plated area and a low wettability non-gold-plated area. The low wettability non-gold-plated area includes a groove located directly below the laser bar. The groove is used to guide and coarsely position the sub-modules when they are placed. Place multiple sub-modules on the ceramic substrate and use a packaging jig with positioning blocks to limit the sub-modules at equal intervals. Solder them with a second solder with a melting point lower than the first solder. During the soldering process, based on the guidance and coarse positioning, the wettability difference between the high wettability gold-plated area and the low wettability non-gold-plated area, as well as the mechanical limiting of the positioning blocks, enable multiple sub-modules to be collinear and equally spaced on the ceramic substrate to form a ceramic substrate module. Step S3: Set up a heat sink, which is used to weld to the ceramic substrate module by a third solder. The upper surface of the heat sink has a groove structure. Weld the ceramic substrate module to the groove structure of the heat sink by a third solder with a melting point lower than that of the second solder.

2. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The width of the groove on the upper surface of the ceramic substrate is 10 to 20 micrometers larger than the bottom width of the laser bar, and its depth is 30% to 40% of the thickness of the laser bar.

3. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The high wettability gold-plated area is the area with a gold-plated layer on the surface, and the low wettability non-gold-plated area is the exposed ceramic surface area.

4. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The packaging fixture includes a side plate and a positioning block. The positioning block has an L-shaped structure, including a long section and a short section. In step S2, one side of the sub-module is attached to the side plate, and the opposite side of the sub-module attached to the side plate is attached to the inner side of the long section. The short section is located between two adjacent sub-modules.

5. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The first solder has a melting point of 270°C to 300°C, the second solder has a melting point of 200°C to 230°C, and the third solder has a melting point of 110°C to 170°C.

6. The DPL linear array laser multibar collinear packaging method according to claim 5, characterized in that, The first solder is a gold-tin alloy, the second solder is a silver-copper alloy or a tin-silver-copper alloy, and the third solder is an indium-based alloy.

7. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The groove structure on the upper surface of the heat sink matches the bottom contour of the ceramic substrate.

8. The DPL linear array laser multibar collinear packaging method according to claim 1, characterized in that, The sub-module formed in step S1 includes a laser bar, two layers of first solder located on the upper and lower surfaces of the laser bar, and two tungsten-copper electrodes welded to the upper and lower surfaces of the laser bar by the first solder.

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