Laser processing method of ceramic substrate

Abstract

The invention relates to the technical field of laser processing, and discloses a laser processing method of a ceramic substrate, which adopts an ultrashort pulse laser and nanosecond laser dual-laser system process, integrates the advantages of precise surface modification of ultrashort pulse laser and efficient processing of nanosecond laser, and forms a micron-sized porous sacrificial layer on the surface of a ceramic material. Micropores and microcracks on the micron-sized porous sacrificial layer destroy the continuous heat conduction path of the original compact ceramic, and heat is gathered on the micron-sized porous sacrificial layer formed on the surface, so that when subsequent nanosecond laser acts, compared with the original smooth ceramic substrate, the generated cracks are easy to block, two-dimensional cracks are not easy to generate on the surface of the ceramic substrate, and the surface of the ceramic substrate is not easy to crack. And low-power and high-efficiency processing can be carried out on the ceramic material without coating an auxiliary material, and high-absorption and low-heat-influence processing is realized.

Description

Technical Field

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

[0002] Laser processing technology is an advanced manufacturing process that uses a laser beam with a high energy density to locally irradiate a material, causing it to evaporate or melt to achieve material removal, connection, or modification. It has the advantages of high precision, a low heat-affected zone, and the ability to process complex shapes and structures, and is widely used in the processing of various materials. Ceramic substrates are widely used in the fields of electronics, aerospace, etc. due to their excellent physical and chemical properties. However, there are two inherent problems in laser processing of ceramics: on the one hand, the inherent brittleness of ceramics and the lack of plastic deformation ability result in the easy expansion of microcracks into macro-cracks during laser irradiation; on the other hand, the low thermal conductivity of ceramics (such as about 30 W / (m·K) for alumina, significantly lower than 398 W / (m·K) for copper) makes it impossible for the processing heat to quickly dissipate, causing local heat accumulation and resulting in thermal damage and thermal cracks.

[0003] In addition, due to the low absorption rate of ceramics to lasers, currently in industry, it is generally common to pre-coat a colored ink or dye (such as carbon paste) on the ceramic surface first to enhance the laser absorption rate and then perform processing. After processing, it is necessary to take water washing or chemical cleaning to remove the coating. However, this method has the following disadvantages: 1) additional coating and cleaning steps are required, and the process is complex and time-consuming; 2) ink residues cause surface contamination or microcracks on the ceramics; 3) environmental problems brought about by the subsequent treatment of the wastewater generated by cleaning. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the above background art, such as the complex and time-consuming process of using lasers to process ceramic materials currently, the easy contamination of ceramics themselves, the lack of plastic deformation ability of ceramic materials, and the low thermal conductivity resulting in thermal damage and thermal cracks during laser processing, the present invention provides a laser processing method for ceramic substrates. An ultrashort pulse laser is used to form a micron-level porous sacrificial layer on the surface of the ceramic material, which destroys the continuous heat conduction path of the dense ceramic, blocks the generated cracks, and is not easy to generate two-dimensional cracks on the ceramic surface; at the same time, the micron-level porous sacrificial layer will make the heat generated by the subsequent nanosecond laser difficult to disperse, further melting and vaporizing the ceramic material, improving the removal rate and the energy utilization rate of the nanosecond laser.

[0005] The technical solution adopted by the present invention is as follows: A laser processing method for ceramic substrates includes the following steps: 1) Scanning or spot irradiating a ceramic substrate with an ultrashort pulse laser to obtain a ceramic substrate with a micron-scale porous sacrificial layer on the surface, where the peak power of the ultrashort pulse laser ≥ 150 kW, and the pore diameter range of the pores in the micron-scale porous sacrificial layer on the surface is 0.5 - 2 μm; 2) Processing the ceramic substrate with a micron-scale porous sacrificial layer on the surface obtained in step 1) with a nanosecond pulse laser to obtain a processed ceramic substrate.

[0006] In the present invention, by performing the laser treatment process step by step, first, an ultrashort pulse laser with a high peak power is used to induce a microscopic rough structure (i.e., a porous layer) on the surface of the ceramic substrate in a scanning or spot irradiating manner. The generated micropores and microcracks destroy the continuous heat conduction path of the original dense ceramic, so that when the subsequent nanosecond laser acts, compared with the original smooth ceramic substrate, the generated cracks are easily blocked and it is not easy to generate two-dimensional cracks on the surface of the ceramic substrate; the ultrashort pulse laser changes the electronic energy band structure by creating point defects (vacancies) or non-stoichiometric phases in the ceramic material, thereby improving the absorption rate of the laser, and increasing the energy utilization rate of the subsequent nanosecond laser by 3 - 4 times; the porous layer, as a micron-scale "porous sacrificial layer" with a mechanical strength far lower than that of the bulk dense ceramic, can reduce the energy density threshold of nanosecond laser processing and further reduce the generation of deep cracks in the subsequent processing; the thermal conductivity of the "porous sacrificial layer" is much lower than that of the dense ceramic material, and the heat accumulation of the subsequent nanosecond laser is not easy to disperse, which can effectively melt and vaporize the ceramic material, improving the removal rate and the energy utilization rate of the nanosecond laser; this solution combines the precise surface modification of the ultrashort pulse laser and the high-efficiency processing advantages of the nanosecond laser, without the need to coat auxiliary materials and omitting the cleaning step.

[0007] Further, the pulse width of the ultrashort pulse laser ≤ 200 ps, and the parameters of the ultrashort pulse laser are optimized to ensure roughening of the matte surface while not generating deep cracks and improving the production quality.

[0008] Further, in step 1), the repetition frequency of the ultrashort pulse laser is 100 kHz - 1000 MHz, the spot diameter is 10 - 50 μm, and the scanning rate is 200 - 10000 mm / s.

[0009] Further, in step 1), the thickness of the micron-scale porous sacrificial layer on the surface is 1 - 5 μm.

[0010] Further, the material of the ceramic substrate is one of alumina ceramics, aluminum nitride ceramics, silicon nitride ceramics, silicon carbide ceramics, or boron nitride ceramics.

[0011] Further, the surface roughness of the ceramic substrate with a micron-scale porous sacrificial layer on the surface obtained in step 1) > 1 μm.

[0012] Further, in step 2), the peak power of the nanosecond pulsed laser is 5 kW to 20 kW, so that the nanosecond laser power is matched with the scanning speed, enabling efficient processing at a lower power and avoiding thermal stress damage.

[0013] Further, the pulse width is 1 to 100 ns.

[0014] Further, the repetition frequency of the nanosecond pulsed laser is 10 kHz to 100 MHz, and the scanning rate is 100 - 5000 mm / s.

[0015] Further, in step 2), the processing method of the nanosecond pulsed laser is one of drilling, cutting, or scribing.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention uses an ultrashort pulsed laser to perform surface processing on a ceramic material. The generated micropores and microcracks destroy the continuous heat conduction path of the original dense ceramic, and the heat accumulates in the micropore layer formed on the surface. When the subsequent nanosecond laser acts, compared with the original smooth ceramic substrate, the generated cracks are easily blocked and it is not easy to generate two-dimensional cracks on the surface of the ceramic substrate.

[0017] 2) The "porous sacrificial layer" with a mechanical strength far lower than that of the original dense ceramic is formed on the surface of the ceramic material by the porous layer formed by the ultrashort pulsed laser in the present invention, reducing the energy density threshold of nanosecond laser processing, further reducing the generation of deep cracks in the subsequent processing. The thermal conductivity of the "porous sacrificial layer" is much lower than that of the dense ceramic material, and the heat generated by the subsequent nanosecond laser is not easy to disperse, which can effectively melt and vaporize the ceramic material, improving the removal rate and the energy utilization rate of the nanosecond laser.

[0018] 3) The present invention adopts a dual-laser collaborative process, combining the precise surface modification of the ultrashort pulsed laser with the high-efficiency processing advantages of the nanosecond laser. Point defects (vacancies) or non-stoichiometric phases are created in the ceramic material by the ultrashort pulsed laser, changing the electronic energy band structure, thereby enhancing the laser absorption rate. The energy utilization rate of the subsequent nanosecond laser is increased by 3 to 4 times, enabling the enhancement of the laser absorption rate without coating auxiliary materials, eliminating the cleaning step, shortening the processing cycle by more than 30%, and simultaneously achieving the technical effects of no ceramic chipping and no cracks.

[0019] 4) The present invention optimizes the parameters of the ultrashort pulsed laser and uses a high-peak ultrashort pulsed laser to ensure roughening of the surface of the ceramic material without generating deep cracks and avoiding substrate damage; by optimizing the nanosecond laser power to match the scanning speed, "high absorption - low heat influence" processing is completed, and at the same time, the ink consumption and wastewater treatment cost can be reduced, the process flow can be simplified, and green production can be achieved. Specific embodiments

[0020] All features disclosed in this specification, or steps in all methods or processes disclosed, can be combined in any way, except for mutually exclusive features and / or steps.

[0021] The present invention will be further described below in conjunction with embodiments. Embodiment

[0022] A method for processing through holes in an aluminum nitride ceramic substrate 1) Ultrafast pulse laser pretreatment Use a femtosecond laser with a pulse width of 500 fs, a peak power of 1 MW, and a scanning speed of 5000 mm / s to scan the surface of the aluminum nitride ceramic substrate, forming an aluminum nitride ceramic substrate with a micron-scale porous sacrificial layer on the surface. The thickness of the micron-scale porous sacrificial layer is 2 μm, and the pore diameter is 1 μm.

[0023] 2) Nanosecond laser drilling Use a nanosecond laser with a pulse width of 100 ns, a peak power of 10 kW, and a scanning speed of 1000 mm / s to perform circular scanning on the aluminum nitride ceramic substrate with a micron-scale porous sacrificial layer on the surface obtained in step 1), and process a through hole with a diameter of 0.2 mm to achieve the effect of no cracks. Embodiment

[0024] A processing method for scribing an alumina ceramic substrate 1) Ultrafast pulse laser pretreatment Use a femtosecond laser with a pulse width of 10 fs, a peak power of 500 kW, and a scanning speed of 3000 mm / s to scan the surface of the alumina ceramic substrate, forming an alumina ceramic substrate with a micron-scale porous rough band on the surface. The thickness of the micron-scale porous sacrificial layer is 1 μm, and the pore diameter is 0.5 μm.

[0025] 2) Nanosecond laser cutting Use a nanosecond laser with a pulse width of 50 ns, a peak power of 5 kW, and a scanning speed of 500 mm / s to perform high-speed scribing along the linear rough band on the alumina ceramic substrate with a micron-scale linear rough band on the surface obtained in step 1). After measurement, the cutting depth consistency reaches ±5 μm.

[0026] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0027] The above-described embodiments merely represent specific implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application.

Claims

1. A laser processing method for a ceramic substrate, characterized in that, The method includes the following steps: 1) Scanning or spot irradiating a ceramic substrate with an ultrashort pulse laser to obtain a ceramic substrate with a micron-scale porous sacrificial layer on its surface. The peak power of the ultrashort pulse laser is ≥150 kW, and the pore diameter of the holes in the micron-scale porous sacrificial layer on the surface ranges from 0.5 to 2 μm; 2) Processing the ceramic substrate with a micron-scale porous sacrificial layer obtained in step 1) using a nanosecond pulse laser to obtain a processed ceramic substrate.

2. The laser processing method of a ceramic substrate according to claim 1, wherein, The pulse width of the ultrashort pulse laser is ≤200 ps.

3. A laser processing method for a ceramic substrate according to claim 1 or 2, characterized in that, In step 1), the repetition frequency of the ultrashort pulse laser is 100 kHz to 1000 MHz, the spot diameter is 10 to 50 μm, and the scanning rate is 200 to 10000 mm / s.

4. A laser processing method for a ceramic substrate according to claim 1, characterized in that, In step 1), the thickness of the micron-scale porous sacrificial layer on the surface is 1 to 5 μm.

5. A laser processing method for a ceramic substrate according to claim 1, wherein, The material of the ceramic substrate is one of alumina ceramics, aluminum nitride ceramics, silicon nitride ceramics, silicon carbide ceramics, or boron nitride ceramics.

6. A laser processing method for a ceramic substrate according to claim 1, characterized in that, The surface roughness of the ceramic substrate with a micron-scale porous sacrificial layer obtained in step 1) is >1 μm.

7. A laser processing method for a ceramic substrate according to claim 1, characterized in that, In step 2), the peak power of the nanosecond pulse laser is 5 kW to 20 kW.

8. A laser processing method for a ceramic substrate according to claim 7, characterized in that, The pulse width is 1 to 100 ns.

9. A laser processing method for a ceramic substrate according to claim 7, characterized in that, The repetition frequency of the nanosecond pulse laser is 10 kHz to 100 MHz, and the scanning rate is 100 - 5000 mm / s.

10. A laser processing method for a ceramic substrate according to claim 1, characterized in that, In step 2), the processing method of the nanosecond pulse laser is one of drilling, cutting, or scribing.