Laser treatment method for ceramic aluminum nitride substrate

Abstract

The invention relates to the technical field of laser processing treatment, in particular to a laser treatment method for a ceramic aluminum nitride substrate, which comprises the following steps: respectively carrying out pretreatment and post-treatment on laser cutting treatment to enable the surface of the substrate to be treated to have a laser protective layer with adsorption performance, and combining with a cleaning solution prepared from multiple components, according to the method, aluminum metal, slag micro powder and the like separated out of the side face of the aluminum nitride substrate to be processed after laser cutting can be completely removed, meanwhile, metal layers on the front face and the back face of the aluminum nitride substrate and an aluminum nitride substrate body are not corroded, and the insulativity and the normal functions of the metal layers and the aluminum nitride substrate during cold head packaging are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to a laser processing method for a ceramic aluminum nitride substrate. Background Art

[0002] An infrared detector consists of a detector chip and a Dewar assembly. The Dewar assembly can be divided into a vacuum housing and a cold head part. The cold head part contains an aluminum nitride substrate. Aluminum nitride ceramic substrate has high thermal conductivity, low expansion coefficient, high strength, high temperature resistance, chemical corrosion resistance, high resistivity, and small dielectric loss. It is an ideal heat dissipation substrate and packaging material for large-scale integrated circuits and high-frequency circuits. Due to the high thermal conductivity of the aluminum nitride ceramic substrate, it can meet the good adiabatic characteristics of the Dewar assembly and is a functional component with the largest temperature hysteresis effect. The aluminum nitride ceramic substrate can stabilize the use function of the detector and improve the service life of the infrared detector. The ceramic aluminum nitride substrate in the cold head belongs to a special-shaped two-dimensional design structure. In production and manufacturing, laser cutting is mostly used for scribing to meet the requirements of special-shaped structures and dimensional tolerances.

[0003] Currently, during the laser cutting process, a high-energy laser beam causes high-temperature chemical reactions on the aluminum nitride ceramic substrate, resulting in the precipitation of aluminum metal on the cutting side. The precipitation of aluminum metal will cause leakage during the cold head packaging, burning out the infrared detector chip and scrapping the product. At the same time, laser slag will also remain on the surface of the aluminum nitride ceramic substrate and is difficult to remove.

[0004] Moreover, before laser cutting, the aluminum nitride ceramic substrate in the cold head has been metallized. And the surface polish of the ceramic substrate has very high requirements. Using the traditional hydrochloric acid and sulfuric acid corrosion method will damage the metal layer and roughen the surface polish of the aluminum nitride ceramic substrate; at the same time, it will also damage the polyimide layer (PI barrier layer) on the front surface, resulting in the peeling off of the metallized layer and unstable circuit signals.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a laser processing method for a ceramic aluminum nitride substrate. By performing pre-treatment and post-treatment during laser cutting and combining a laser protection liquid and a cleaning liquid, it can completely remove the aluminum metal precipitated on the side of the aluminum nitride substrate to be processed after laser cutting, while not corroding the metal layers on the front and back sides of the aluminum nitride substrate and the aluminum nitride substrate itself, ensuring the insulation, normal functions of the metal layer and the aluminum nitride substrate during cold head packaging, and solving the problems existing in the prior art.

[0007] To solve the above technical problems, the present invention adopts the following solutions: A laser processing method for a ceramic aluminum nitride substrate includes the following steps: S1, Laser pretreatment: Spin-coat a laser protective liquid on the surface of the aluminum nitride substrate to be processed to form an aluminum nitride substrate with a laser protection layer. S2, Laser cutting treatment: Laser cut the aluminum nitride substrate with a laser protection layer, and successively wash it with normal-temperature pure water and hot pure water. After dissolving the laser protection layer on the surface of the aluminum nitride substrate and the slag adsorbed by the laser protection layer, perform a primary drying treatment. S3, Laser post-treatment: Immerse the aluminum nitride substrate completed in step S2 in a cleaning solution to remove the aluminum metal precipitated on the side of the aluminum nitride substrate. After washing with pure water, perform a secondary drying treatment to obtain an insulating aluminum nitride substrate.

[0008] The present invention mainly performs pretreatment and post-treatment during laser treatment. The laser protective liquid in the pretreatment forms a laser protection layer with adsorption performance on the surface of the aluminum nitride substrate. During laser cutting, part of the slag and microparticles generated are physically blocked by the laser protection layer and part are adsorbed; the post-treatment uses a cleaning solution prepared by multi-component formulation to remove the remaining laser protection layer, slag, microparticles, and the aluminum metal precipitated on the side, and does not corrode the metal layer on the surface of the aluminum nitride substrate and the aluminum nitride substrate itself, ensuring the insulating performance of the final aluminum nitride substrate. Refer to Figure 5 。

[0009] Further, in step S1, by mass percentage, the laser protective liquid is composed of 1% - 20% polyvinyl alcohol, 1% - 20% propylene glycol methyl ether, and 60% - 98% deionized water, where the molecular weight of polyvinyl alcohol is 10×10 4 g / mol - 25×10 4 g / mol.

[0010] After spin-coating on the substrate surface, a laser protection layer containing a polyvinyl alcohol film is formed to isolate the direct thermal shock during laser cutting. The polyvinyl alcohol film adsorbs the splashed slag and microparticles during the cutting process to prevent them from adhering to the surface of the aluminum nitride substrate.

[0011] Further, add polyvinyl alcohol, propylene glycol methyl ether, and deionized water into a stirring container in sequence, stir at 300 r / min - 1000 r / min for 1 h - 2 h, and let it stand for 4 h - 24 h for use.

[0012] Further, during spin-coating, the rotation speed is 200 r / min - 220 r / min for 30 s - 40 s.

[0013] Further, in step S2, the laser power during laser cutting treatment is 2 W - 10 W, scan 5 times - 50 times, and the scan speed is 1 mm / s - 10 mm / s.

[0014] Further, during cleaning, rinse with normal-temperature pure water for 5 min to 8 min, the temperature of hot pure water is 50°C to 100°C, and ultrasonically soak for 5 min to 15 min.

[0015] Further, in step S3, the cleaning solution is composed of glacial acetic acid, phosphoric acid, nitric acid, sodium molybdate, and deionized water, and the volume ratio is 1 - 5:7 - 20:8 - 20:0.1 - 2:1 - 20.

[0016] Dissolve the residual polyvinyl alcohol in an acidic environment, remove the precipitated aluminum metal and slag, and sodium molybdate prevents the cleaning solution from corroding the substrate excessively.

[0017] Further, heat the cleaning solution to 45°C to 55°C, place the aluminum nitride substrate after laser cutting in the cleaning solution and clean for 30 min to 40 min, and stir the cleaning solution every 10 min.

[0018] Further, place the aluminum nitride substrate that has been cleaned with the cleaning solution in pure water at 50°C to 60°C and clean it by bubbling nitrogen for 5 min to 10 min.

[0019] Further, for the first spin-drying and the second spin-drying, rinse for 15 - 20 s at 600 r / min to 800 r / min in sequence; blow dry for 60 s to 80 s at 600 r / min to 800 r / min; During the first spin-drying, dry for 120 s to 150 s at 800 r / min to 1000 r / min; During the second spin-drying, dry for 60 s to 100 s at 800 r / min to 1000 r / min.

[0020] The beneficial effects of the present invention are as follows: For the laser treatment method of the present invention, on the one hand, before the laser cutting treatment of the aluminum nitride substrate, a laser protection solution is prepared to form a laser protection layer containing a polyvinyl alcohol film, so that the laser protection layer has an adsorption property to isolate the direct thermal shock during laser cutting. The polyvinyl alcohol film adsorbs the splashed slag and microparticles during the cutting process to prevent them from adhering to the surface of the aluminum nitride substrate.

[0021] On the other hand, after the laser treatment of the aluminum nitride substrate, it is cleaned with a cleaning solution made of multiple components. Dissolve the residual polyvinyl alcohol in an acidic environment, remove the precipitated aluminum metal and slag, and sodium molybdate prevents the cleaning solution from corroding the substrate excessively. After the laser cutting of the aluminum nitride substrate, the aluminum metal precipitated on the side of the aluminum nitride substrate can be completely removed without corroding the metal layers on the front and back sides of the ceramic substrate and the aluminum nitride ceramic substrate body itself, ensuring the insulation during the cold head packaging, the normal functions of the metal layer and the ceramic substrate, and improving the qualification rate of the Dewar cold head. Description of the Drawings

[0022] Figure 1It is a physical picture of the surface of an aluminum nitride substrate before and after cleaning after laser cutting in Example 1. Figure 1 In Figure 1 , A is the physical picture of the surface of the aluminum nitride substrate before cleaning. Figure 1 In Figure 1 , B is the physical picture of the surface of the aluminum nitride substrate after cleaning. Figure 2 It is a physical picture of the side of the aluminum nitride substrate after being cleaned with the cleaning solution in Example 1. Figure 3 It is a physical picture of the surface of the aluminum nitride substrate before and after traditional cleaning after laser cutting in Comparative Example 1. Figure 3 In Figure 3 , A is the physical picture of the surface of the aluminum nitride substrate before traditional cleaning. Figure 3 In Figure 3 , B is the physical picture of the surface of the aluminum nitride substrate after traditional cleaning. Figure 4 It is a physical picture of the side of the aluminum nitride substrate after being soaked and cleaned with traditional hydrochloric acid and sulfuric acid in Comparative Example 2. Figure 5 It is a schematic diagram of the principle of the laser treatment method of the present invention. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0024] In addition, for the sake of clarity and conciseness, descriptions of well-known structures, functions and configurations may be omitted. Those of ordinary skill in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0025] Technical means, methods and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, such technical means, methods and equipment should be regarded as part of the authorization specification.

[0026] In all the examples shown and discussed here, any specific value should be construed as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0027] Example 1 A laser treatment method for a ceramic aluminum nitride substrate includes the following steps: (1) Laser pretreatment: Prepare a laser protection liquid. By mass percentage, the laser protection liquid consists of 10% polyvinyl alcohol, 10% propylene glycol methyl ether, and 80% deionized water, where the molecular weight of polyvinyl alcohol is 10×10 4 g / mol; Add polyvinyl alcohol, propylene glycol methyl ether, and deionized water into a stirring container in sequence, stir at 300 r / min for 1 h, and let it stand for 8 h for later use.

[0028] Spin-coat the laser protection liquid on the surface of the aluminum nitride substrate to be processed to form an aluminum nitride substrate with a laser protection layer. The spin-coating parameters are 200 r / min and 30 s. It can block and adsorb some fine powder particles, slag, etc. generated on the substrate surface after laser cutting treatment of the aluminum nitride substrate to be processed, preventing the fine powder particles, slag, etc. from remaining on the substrate surface.

[0029] (2)Laser cutting treatment: Cut the aluminum nitride substrate with a laser protection layer by laser. When laser cutting, the laser power is 2 W, scan 15 times, and the scan speed is 3 mm / s. After cutting, rinse with normal-temperature pure water for 5 min, then use hot pure water at 80°C and ultrasonically soak for 10 min to dissolve the laser protection layer on the substrate surface and remove the fine powder particles, slag, etc. adsorbed on the laser protection layer. After one centrifugal drying treatment, rinse for 15 s at 600 r / min; blow dry for 60 s at 800 r / min; dry for 120 s at 800 r / min.

[0030] (3)Laser post-treatment: Prepare a cleaning liquid. The cleaning liquid consists of glacial acetic acid, phosphoric acid, nitric acid, sodium molybdate, and deionized water, and the volume ratio is 2:8:9:0.5:5. Add each component into a container in sequence and stir to make it.

[0031] Heat the cleaning liquid to 50°C, place the aluminum nitride substrate after one centrifugal drying treatment in a container containing the cleaning liquid, clean for 30 min, and stir the cleaning liquid every 10 min. Then place the aluminum nitride substrate in hot pure water at 55°C and purge with nitrogen bubbles for 5 min. Then perform a second centrifugal drying treatment, rinse for 15 s at 600 r / min; blow dry for 60 s at 800 r / min; dry for 60 s at 800 r / min. Remove the laser slag, fine dust on the surface of the aluminum nitride substrate after cutting, and the aluminum metal precipitated on the substrate surface, while not damaging the metal layer, PI layer, and ceramic substrate. The schematic diagram of the principle of the laser treatment method of the present invention is referred to Figure 5 as shown.

[0032] Example 2 A laser treatment method for a ceramic aluminum nitride substrate, comprising the following steps: (1)Laser pretreatment: Prepare a laser protection liquid. By mass percentage, the laser protection liquid consists of 20% polyvinyl alcohol, 20% propylene glycol methyl ether, and 60% deionized water, where the molecular weight of the polyvinyl alcohol is 20×10 4 g / mol; Add polyvinyl alcohol, propylene glycol methyl ether, and deionized water into a stirring container in sequence, stir at 500 r / min for 2 h, and let it stand for 12 h for standby.

[0033] Spin-coat the laser protection liquid on the surface of the aluminum nitride substrate to be processed to form an aluminum nitride substrate with a laser protection layer. The spin-coating parameters are 220 r / min and 30 s. It blocks and adsorbs some fine powder particles, slag, etc. generated on the substrate surface after laser cutting treatment of the aluminum nitride substrate to be processed, preventing the fine powder particles, slag, etc. from remaining on the substrate surface.

[0034] (2)Laser cutting treatment: Cut the aluminum nitride substrate with a laser protection layer by laser. When laser cutting, the laser power is 8 W, scan 20 times, and the scan speed is 6 mm / s. After cutting, rinse with normal-temperature pure water for 6 min, hot pure water at 70 °C, and ultrasonically soak for 15 min in sequence to dissolve the laser protection layer on the substrate surface and remove the fine powder particles, slag, etc. adsorbed on the laser protection layer. After one centrifugal drying treatment, rinse for 15 s at 800 r / min, blow dry for 80 s at 1000 r / min, and dry for 130 s at 1000 r / min in sequence.

[0035] (3)Laser post-treatment: Prepare a cleaning liquid. The cleaning liquid consists of glacial acetic acid, phosphoric acid, nitric acid, sodium molybdate, and deionized water, and the volume ratio is 5:14:10:1:8. Add each component into a container in sequence and stir to make it.

[0036] Heat the cleaning liquid to 55 °C, place the aluminum nitride substrate after one centrifugal drying treatment in a container containing the cleaning liquid, clean for 40 min, and stir the cleaning liquid every 10 min. Then place the aluminum nitride substrate in hot pure water at 60 °C and purge nitrogen bubbles for cleaning for 10 min. Then, after a second centrifugal drying treatment, rinse for 15 s at 600 r / min, blow dry for 60 s at 800 r / min, and dry for 60 s at 800 r / min in sequence. Remove the laser slag, fine dust on the surface of the aluminum nitride substrate after cutting, and aluminum metal precipitated on the substrate surface, while not damaging the metal layer, PI layer, and ceramic substrate.

[0037] Example 3 A laser treatment method for a ceramic aluminum nitride substrate, comprising the following steps: (1)Laser pretreatment: Prepare a laser protection liquid. By mass percentage, the laser protection liquid consists of 15% polyvinyl alcohol, 15% propylene glycol methyl ether, and 70% deionized water, where the molecular weight of the polyvinyl alcohol is 25×104 g / mol; Add polyvinyl alcohol, propylene glycol methyl ether, and deionized water into a stirring container in sequence, stir at 1000 r / min for 1 h, and let it stand for 24 h for later use.

[0038] Spin-coat a laser protection liquid on the surface of the aluminum nitride substrate to be processed to form an aluminum nitride substrate with a laser protection layer. The spin-coating parameters are 200 r / min for 40 s, which can block and adsorb some fine powder particles, slag, etc. generated on the substrate surface after laser cutting treatment of the aluminum nitride substrate to be processed, preventing the fine powder particles, slag, etc. from remaining on the substrate surface.

[0039] (2) Laser cutting treatment: Cut the aluminum nitride substrate with a laser protection layer by laser. The laser power during laser cutting is 10 W, scan 50 times, and the scan speed is 10 mm / s. After cutting, rinse with normal-temperature pure water for 8 min, hot pure water at 100 °C, and ultrasonically soak for 15 min in sequence to dissolve the laser protection layer on the substrate surface and remove the fine powder particles, slag, etc. adsorbed on the laser protection layer. After one centrifugal drying treatment, rinse for 25 s at 800 r / min; blow dry for 80 s at 1000 r / min; dry for 150 s at 1000 r / min in sequence.

[0040] (3) Laser post-treatment: Prepare a cleaning solution. The cleaning solution is composed of glacial acetic acid, phosphoric acid, nitric acid, sodium molybdate, and deionized water, and the volume ratio is 5:20:8:2:18. Add each component into a container in sequence and stir to make it.

[0041] Heat the cleaning solution to 45 °C, place the aluminum nitride substrate after one centrifugal drying treatment in a container containing the cleaning solution, and clean for 30 min, stirring the cleaning solution every 10 min. Then place the aluminum nitride substrate in hot pure water at 60 °C and purge nitrogen bubbles for cleaning for 8 min. After the second centrifugal drying treatment, rinse for 15 s at 600 r / min; blow dry for 60 s at 1000 r / min; dry for 60 s at 1000 r / min in sequence. Remove the laser slag, fine dust on the surface of the aluminum nitride substrate after cutting, and aluminum metal precipitated on the substrate surface, while not damaging the metal layer, PI layer, and ceramic substrate.

[0042] Comparative Example 1 Comparative Example 1 is implemented on the basis of Example 1. The main difference is that no laser protection layer is added before laser cutting treatment, with reference to Figure 2 .

[0043] Comparative Example 2 Comparative Example 2 is implemented on the basis of Example 1. The main difference is that the substrate is soaked in a mixture of traditional hydrochloric acid and sulfuric acid.

[0044] The insulation of the aluminum nitride substrates after final laser cutting in Example 1 and Comparative Example 2 was detected using a multimeter, as shown in Table 1 below: Table 1 Comparison of insulation test results of aluminum nitride substrates in Example 1 and Comparative Example 2 According to Figures 1 to 4 , and Table 1, it can be seen that in this Example 1, a laser protection liquid was spin-coated on the surface of the aluminum nitride substrate to be processed before laser cutting to form a laser protection layer with an adsorption function, which physically blocked and adsorbed the fine powder particles, slag, etc. generated on the surface of the aluminum nitride substrate after laser cutting, and its water solubility facilitated cleaning; after laser cutting, it was washed twice with pure water and then solvent-washed with a prepared cleaning solution, effectively removing the aluminum metal on the side of the aluminum nitride substrate after cutting without damaging the metal layer, PI layer, and the aluminum nitride substrate itself, making the finally obtained aluminum nitride substrate insulating, ensuring the insulation during cold head packaging, the normal functions of the metal layer and the aluminum nitride substrate, and improving the qualification rate of the Dewar assembly. The aluminum nitride substrates after cutting in Comparative Example 1 and Comparative Example 2 still had residual slag and fine powder particles; and there was current, that is, they were not insulated.

[0045] The above are only the preferred embodiments of the present invention and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to form equivalent embodiments with equivalent changes, but as long as the content does not depart from the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A laser processing method for a ceramic aluminum nitride substrate, characterized in that, It includes the following steps: S1, Laser pretreatment: Spin-coat a laser protection liquid on the surface of the aluminum nitride substrate to be processed to form an aluminum nitride substrate with a laser protection layer; S2, Laser cutting treatment: Laser cut the aluminum nitride substrate with a laser protection layer, and successively wash it with normal-temperature pure water and hot pure water. After dissolving the laser protection layer on the surface of the aluminum nitride substrate and the slag adsorbed by the laser protection layer, perform a primary drying treatment; S3, Laser post-treatment: Immerse the aluminum nitride substrate completed in step S2 in a cleaning solution to remove the aluminum metal precipitated on the side of the aluminum nitride substrate, wash it with pure water and then perform a secondary drying treatment to obtain an insulating aluminum nitride substrate.

2. The laser processing method for a ceramic aluminum nitride substrate according to claim 1, characterized in that, In step S1, by mass percentage, the laser protection liquid is composed of 1% - 20% polyvinyl alcohol, 1% - 20% propylene glycol methyl ether, and 60% - 98% deionized water, where the molecular weight of the polyvinyl alcohol is 10×10 4 g / mol - 25×10 4 g / mol.

3. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, Add polyvinyl alcohol, propylene glycol methyl ether, and deionized water into a stirring container in sequence, stir at 300 r / min to 1000 r / min for 1 h to 2 h, and let it stand for 4 h to 24 h for standby.

4. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, During spin-coating, the rotation speed is 200 r / min to 220 r / min for 30 s to 40 s.

5. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, In step S2, during laser cutting treatment, the laser power is 2 W to 10 W, scan 5 times to 50 times, and the scan speed is 1 mm / s to 10 mm / s.

6. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, During cleaning, rinse with normal-temperature pure water for 5 min to 8 min, the temperature of the hot pure water is 50°C to 100°C, and ultrasonically soak for 5 min to 15 min.

7. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, In step S3, the cleaning solution is composed of glacial acetic acid, phosphoric acid, nitric acid, sodium molybdate, and deionized water, and the volume ratio is 1 to 5:7 to 20:8 to 20:0.1 to 2:1 to 20.

8. A laser processing method for a ceramic aluminum nitride substrate according to claim 2, characterized in that, Heat the cleaning solution to 45°C to 55°C, place the aluminum nitride substrate completed with laser cutting in the cleaning solution for cleaning for 30 min to 40 min, and stir the cleaning solution every 10 min.

9. A laser processing method for a ceramic aluminum nitride substrate according to claim 8, characterized in that, Place the aluminum nitride substrate completed with cleaning by the cleaning solution in pure water at 50°C to 60°C and clean it by bubbling nitrogen for 5 min to 10 min.

10. A laser processing method for a ceramic aluminum nitride substrate according to claim 8, characterized in that, For the primary drying and secondary drying, rinse for 15 to 20 s at 600 r / min to 800 r / min in sequence; blow dry for 60 s to 80 s at 600 r / min to 800 r / min; During the primary drying, dry for 120 s to 150 s at 800 r / min to 1000 r / min; During the secondary drying, dry for 60 s to 100 s at 800 r / min to 1000 r / min.

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