Laser processing method for ceramic substrate

Abstract

The application relates to the technical field of laser processing, and discloses a laser processing method for a ceramic substrate, which adopts a double-laser system process of an ultrashort pulse laser and a nanosecond laser, combines the advantages of precise surface modification of the ultrashort pulse laser and efficient processing of the nanosecond laser, forms a micrometer-level porous sacrificial layer on the surface of the ceramic material, and the micropores and microcracks on the micrometer-level porous sacrificial layer destroy the continuous heat conduction path of the originally dense ceramic, so that heat is gathered in the micrometer-level porous sacrificial layer formed on the surface; when the subsequent nanosecond laser acts, compared with the originally smooth ceramic substrate, the cracks generated by the ceramic substrate are easy to be blocked, and it is not easy to generate two-dimensional cracks on the surface of the ceramic substrate, the ceramic material can be processed at low power and high efficiency without coating auxiliary materials, and the "high absorption-low heat influence" processing is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser processing, and particularly relates to a laser processing method for a ceramic substrate. BACKGROUND

[0002] Laser processing technology is an advanced manufacturing process that uses a high-energy-density laser beam to irradiate a material locally, causing it to evaporate or melt, thereby achieving material removal, connection or modification. It has the advantages of high precision, 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, but there are two inherent problems in laser processing of ceramics. On the one hand, the inherent brittleness and lack of plastic deformation ability of ceramics cause micro-cracks to easily expand into macro-cracks when irradiated by a laser. On the other hand, the low thermal conductivity of ceramics (such as alumina, about 30 W / (m·K), which is significantly lower than that of copper, 398 W / (m·K)) causes the processing heat to be unable to disperse quickly, resulting in local heat accumulation and causing thermal damage and thermal cracks.

[0003] In addition, due to the low absorption rate of ceramics to laser, it is currently common in the industry to first coat the ceramic surface with colored ink or dye (such as carbon paste) to enhance the laser absorption rate before processing, and then remove the coating by water washing or chemical cleaning after processing is completed. However, this method has the following disadvantages: 1) additional coating and cleaning steps are required, the process is complex and time-consuming; 2) ink residues cause contamination or micro-cracks on the ceramic surface; 3) environmental problems caused by subsequent treatment of waste water generated by cleaning. SUMMARY

[0004] In order to solve the technical problems of the existing laser processing of ceramic materials mentioned in the background, such as complex process, long processing time, and easy pollution to the ceramic itself, the lack of plastic deformation ability of the ceramic material itself, and the low thermal conductivity of the ceramic material, which leads to thermal damage and thermal cracks when using laser processing, the present application provides a laser processing method for a ceramic substrate. The method uses an ultrashort pulse laser to form a micron-scale 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 makes it difficult to produce two-dimensional cracks on the ceramic surface. At the same time, the micron-scale porous sacrificial layer will cause the heat generated by the subsequent nanosecond laser to accumulate and not disperse easily, further melting and vaporizing the ceramic material, and improving the removal rate and energy utilization rate of the nanosecond laser.

[0005] The technical solution adopted by the present application is as follows: a laser processing method for a ceramic substrate, comprising the following steps:

[0006] 1) scanning or point irradiation on the ceramic substrate with an ultrashort pulse laser to obtain a ceramic substrate with a microporous sacrificial layer on the surface, wherein the ultrashort pulse laser has a peak power of 150 kW or more, and the microporous sacrificial layer on the surface has a pore size range of 0.5-2 microns;

[0007] 2) processing the ceramic substrate with a microporous sacrificial layer on the surface obtained in step 1) with a nanosecond pulse laser to obtain a processed ceramic substrate.

[0008] The present application performs the laser processing process in steps. First, an ultrashort pulse laser with high peak power is used to induce the formation of a micro-rough structure (i.e. a porous layer) on the surface of the ceramic substrate in a scanning or point irradiation manner. The micro-holes and micro-cracks produced destroy the continuous heat conduction path of the original dense ceramic, so that when the subsequent nanosecond laser acts, the cracks are more likely to be blocked and less likely to produce 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 micrometer-scale "porous sacrificial layer" with much lower mechanical strength than 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 process. The thermal conductivity of the "porous sacrificial layer" is much lower than that of the dense ceramic material, so the heat generated by the subsequent nanosecond laser is not easily dissipated, which can effectively melt and vaporize the ceramic material, improve the removal rate and energy utilization rate of the nanosecond laser. The present application combines the advantages of precise surface modification by ultrashort pulse laser and efficient processing by nanosecond laser, without the need for coating auxiliary materials and cleaning steps.

[0009] Further, the pulse width of the ultrashort pulse laser is ≤200 ps, and the parameters of the ultrashort pulse laser are optimized to ensure that the roughening of the surface does not produce deep cracks and improve the production quality.

[0010] Further, in step 1), the repetition frequency of the ultrashort pulse laser is 100 kHz-1000 MHz, the spot diameter is 10-50 microns, and the scanning speed is 200-10000 mm / s.

[0011] Further, in step 1), the thickness of the microporous sacrificial layer on the surface is 1-5 microns.

[0012] Further, the ceramic substrate is made of one of alumina ceramic, aluminum nitride ceramic, silicon nitride ceramic, silicon carbide ceramic or boron nitride ceramic.

[0013] Further, the surface roughness of the ceramic substrate with a microporous sacrificial layer on the surface obtained in step 1) is >1 micron.

[0014] Further, in step 2), the peak power of the nanosecond pulse laser is 5kW~20kW, so as to match the nanosecond laser power with the scanning speed, realize efficient processing at a lower power, and avoid thermal stress damage.

[0015] Further, the pulse width is 1~100ns.

[0016] Further, the repetition frequency of the nanosecond pulse laser is 10kHz~100MHz, and the scanning speed is 100-5000mm / s.

[0017] Further, in step 2), the processing mode of the nanosecond pulse laser is one of drilling, cutting or scribing.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1) The present application uses ultra-short pulse laser to process the surface of ceramic materials, and the micro-holes and micro-cracks generated destroy the continuous heat conduction path of the original dense ceramic. The heat is gathered in the micro-hole layer formed on the surface, so that when the subsequent nanosecond laser acts, the cracks generated are easy to be blocked, and it is not easy to generate two-dimensional cracks on the surface of the ceramic substrate.

[0020] 2) The porous layer formed by the ultra-short pulse laser forms a "porous sacrificial layer" on the surface of the ceramic material, which has a mechanical strength much lower than that of the bulk dense ceramic. The energy density threshold of nanosecond laser processing is reduced, and the generation of deep cracks in the subsequent processing process is further reduced. 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, improve the removal rate and the energy utilization rate of the nanosecond laser.

[0021] 3) The present application adopts a double laser collaborative process, combines the advantages of precise surface modification of ultra-short pulse laser and efficient processing of nanosecond laser, changes the electronic energy band structure by manufacturing point defects (vacancies) or non-stoichiometric phases in the ceramic material through ultra-short pulse laser, so as to improve the absorption rate of laser, increase the energy utilization rate of the subsequent nanosecond laser by 3~4 times, realize the enhancement of laser absorption rate without coating auxiliary materials, save the cleaning step, shorten the processing cycle by more than 30%, and achieve the technical effects of no ceramic collapse and no cracks.

[0022] 4) The present application optimizes the parameters of the ultra-short pulse laser, adopts high-peak ultra-short pulse laser, ensures that the surface of the ceramic material is roughened without deep cracks, avoids damage to the substrate, optimizes the nanosecond laser power to match the scanning speed, completes the "high absorption-low heat affected" processing, reduces the ink consumption and wastewater treatment cost, simplifies the process flow, and realizes green production. DETAILED DESCRIPTION

[0023] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0024] The present invention will be further described below with reference to the embodiments. Example

[0025] A method for processing through-holes in aluminum nitride ceramic substrates

[0026] 1) Ultrashort pulse laser pretreatment

[0027] A femtosecond laser with a pulse width of 500fs, a peak power of 1MW, and a scanning speed of 5000mm / s is used to scan the surface of an aluminum nitride ceramic substrate to form 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 2μm and the pore size is 1μm.

[0028] 2) Nanosecond laser drilling

[0029] The aluminum nitride ceramic substrate with a micron-scale porous sacrificial layer on its surface obtained in step 1) is subjected to circular scanning using 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 machine a through hole with a diameter of 0.2 mm, achieving a crack-free effect. Example

[0030] A processing method for scribing an alumina ceramic substrate

[0031] 1) Ultrashort pulse laser pretreatment

[0032] A femtosecond laser with a pulse width of 10 fs, a peak power of 500 kW, and a scanning speed of 3000 mm / s was used to scan the surface of an alumina ceramic substrate to form an alumina ceramic substrate with a micron-scale porous rough band on the surface, wherein the thickness of the micron-scale porous sacrificial layer was 1 μm and the pore diameter was 0.5 μm.

[0033] 2) Nanosecond laser cutting

[0034] On the alumina ceramic substrate with micron-scale linear rough bands on the surface obtained in step 1), high-speed scribing along the linear rough bands was performed using a nanosecond laser with a pulse width of 50ns, a peak power of 5kW, and a scanning speed of 500mm / s. After measurement, the cutting depth consistency reached ±5μm.

[0035] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0036] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the technical concept of the present application, and all such variations and improvements fall within the scope of protection of the present application.

Claims

1. A laser processing method for a ceramic substrate, characterized in that: The following steps are involved: 1) Scanning or spot-irradiating a ceramic substrate with an ultrashort pulse laser to obtain a ceramic substrate having a micron-scale porous sacrificial layer on the surface, wherein the peak power of the ultrashort pulse laser is ≥150 kW, the micron-scale porous sacrificial layer on the surface has a pore size range of 0.5-2 μm, a thickness of 1-5 μm, and a surface roughness greater than 1 μm; 2) The ceramic substrate with the micron-scale porous sacrificial layer on its surface obtained in step 1) is processed using a nanosecond pulse laser to obtain a processed ceramic substrate.

2. The laser processing method for a ceramic substrate according to claim 1, characterized in that: The pulse width of ultrashort pulse laser is ≤200ps.

3. The 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 10,000 mm / s.

4. The laser processing method for a ceramic substrate according to claim 1, characterized in that: The material of the ceramic substrate is one of alumina ceramics, aluminum nitride ceramics, silicon nitride ceramics, silicon carbide ceramics or boron nitride ceramics.

5. The 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 5kW~20kW.

6. The laser processing method for a ceramic substrate according to claim 5, characterized in that: Pulse width 1~100ns.

7. The laser processing method for a ceramic substrate according to claim 5, characterized in that: The repetition frequency of nanosecond pulse laser is 10kHz~100MHz, and the scanning rate is 100-5000mm / s.

8. The 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.