A high-precision ceramic GEM preparation method based on a short pulse laser

Abstract

The application belongs to the technical field of neutron detectors in nuclear technology and high-energy physics, and particularly relates to a high-precision ceramic GEM preparation method based on a short pulse laser and application; the method is characterized in that a solder mask layer is first covered on a double-sided copper-clad substrate, then short pulse laser is used to perforate and punch, then the copper layer at the hole is etched to form a rim ring, the solder mask layer is removed, and the hole wall carbide is removed through plasma cleaning, and finally, the preparation is completed through cleaning, cutting and baking; the laser drilling rate is high, up to 20000 holes / min, the alignment accuracy is micron level, ceramic GEMs with different hole diameters, spacings and thicknesses can be prepared, laser non-contact processing has no drill bit loss, and the insulation performance is improved through plasma cleaning; the ceramic GEM prepared by the method is used for a neutron detector, a high-performance neutron detector can be developed, and the technical development is promoted.

Description

Technical Field

[0001] This invention relates to the field of laser precision machining technology in the field of high-end equipment manufacturing, focusing on neutron detection technology related to nuclear technology and high-energy physics, specifically a method for preparing a high-precision ceramic gas electron multiplier (GEM) based on short-pulse laser. Background Technology

[0002] Ceramic GEMs, with their advantages of low hydrogen content and radiation resistance, exhibit less self-absorption and scattering of neutrons compared to traditional GEM films, making them a promising candidate for neutron detectors. Currently, ceramic GEMs are primarily fabricated using PCB mechanical drilling and etching processes, achieving a pore density of approximately 320 pores / cm². However, mechanical drilling technology has several limitations: the drilling speed is slow, around 300 pores / min, and the pore accuracy is not high (approximately 30 μm); due to the high hardness of the ceramic substrate, frequent drill bit replacements are necessary to prevent drill wear and subsequent degradation in drilling quality and accuracy, increasing production costs and process complexity. As the application area of ​​GEMs expands, the quality, efficiency, and stability of mechanical drilling in GEM fabrication can no longer meet practical requirements, severely hindering the development of GEM detectors.

[0003] Laser technology, with its monochromaticity, coherence, directionality, and high energy density, has seen widespread application in laser drilling in recent years. Laser drilling achieves hole drilling by directing a focused laser beam at the workpiece, burning through a designated area. It offers advantages such as high speed, high efficiency, the ability to achieve large aspect ratios, applicability to various materials, no tool wear, and suitability for multi-hole processing. Drilling rates can reach 20,000 holes / min, significantly improving manufacturing efficiency and shortening production cycles. Despite its widespread use in industrial production, the technology for drilling perfectly circular micropores in ceramic materials is still immature. During laser drilling, re-condensed raw materials and their excrement may deform and protrude along the upper edge of the hole, affecting drilling quality and consequently the performance of the full-area ceramic GEM. For a ceramic GEM with an effective area of ​​200mm × 200mm, the number of holes is enormous (approximately 128,000 holes). Optimizing the laser drilling process to achieve large-area, high-density, and numerous perfectly circular micropores has become a key technical challenge in ceramic GEM fabrication. Summary of the Invention

[0004] To address the aforementioned problems, this invention aims to provide a method for fabricating a high-precision ceramic gas electron multiplier (GEM) based on short-pulse lasers, and the application of the ceramic GEM fabricated using this method in neutron detectors, especially in high-pressure neutron detectors used in conjunction with ³He gas.

[0005] The technical solution adopted in this invention is: a high-precision ceramic GEM preparation method based on short-pulse laser, comprising the following steps: S1 substrate preparation: Cover the copper-clad substrate on both sides with a solder mask to protect the surface copper layer. S2 short-pulse laser drilling: Uses a short-pulse laser to drill through holes in the solder mask layer, copper layer and ceramic substrate to form through holes; S3 acid etching to form rim rings: Acid etching is performed on the copper layer at the opening location to form rim rings to improve the GEM withstand voltage. S4 Remove solder mask: Removes the solder mask covering the surface; S5 plasma cleaning treatment: The GEM film after laser drilling is subjected to plasma cleaning treatment to remove the carbonized material generated inside the hole wall; S6 Cleaning, Cutting and Baking: Cleaning, cutting and baking are performed to complete the preparation of ceramic GEM.

[0006] The pulse width of the short-pulse laser is in the order of ns, ps, or fs.

[0007] During the laser drilling process, the laser parameters need to be repeatedly adjusted to obtain the perfect GEM hole shape and surface quality.

[0008] The gas environment for the plasma cleaning process is a mixture of CH4 and O2.

[0009] The ceramic GEM has a thickness of 50 μm to 300 μm, a pore size of 50 μm to 200 μm, a pore spacing of 200 μm to 600 μm, and an insulating ring (rim) width of 40 μm to 80 μm.

[0010] The method also includes optimizing the laser parameters, cleaning gas composition and flow rate ratio during the preparation process to achieve large-area, high-density, and numerous perfectly circular micropores.

[0011] The solder resist layer is a photosensitive solder resist or other solder resist material suitable for laser processing.

[0012] The etching solution used in the acid etching step is a hydrochloric acid solution, a sulfuric acid solution, or other chemical solutions suitable for etching copper layers.

[0013] The ceramic GEM is used in neutron detectors, particularly with... 3 A high-pressure neutron detector that uses He gas.

[0014] The neutron detector features a large area, high count rate, high efficiency, and high gamma suppression capability.

[0015] The high-precision ceramic GEM fabrication method based on short-pulse laser of the present invention has the following significant advantages over the prior art: In this invention, the laser drilling rate is much higher than that of traditional mechanical drilling, reaching 20,000 holes / min, which greatly shortens the production cycle and improves the preparation efficiency of ceramic GEMs.

[0016] This invention features high laser alignment accuracy, employing short-pulse lasers (pulse width at the ns, ps, or fs level) for drilling, resulting in minimal thermal damage to the substrate and less spatter. It ensures drilling accuracy down to the micrometer level, guaranteeing overall uniformity and consistency of the drilling process, and effectively improving and optimizing the ceramic GEM performance.

[0017] This invention can prepare ceramic GEMs with different pore sizes and pore spacings, and can obtain ceramic GEMs with thinner thickness (50μm-300μm), smaller pore size (50μm-200μm), and pore spacing (200μm-600μm) to meet diverse application needs.

[0018] The laser processing of this invention is a non-contact process, eliminating the problem of drill bit wear and avoiding the quality degradation caused by drill bit wear in mechanical drilling. This results in better hole quality and improves the yield and quality of large-area ceramic GEMs. By performing plasma cleaning treatment on the GEM film after laser drilling, the carbonized material generated in the hole wall is removed, effectively solving the problem of cross-layer conductivity of the GEM film caused by carbonized material in the hole wall, and improving the insulation performance of the GEM film.

[0019] The ceramic GEM prepared by the method of this invention can be used in neutron detectors, especially high-pressure neutron detectors used in combination with ³He gas. It can be used to develop neutron detectors with large area, high count rate, high efficiency and high gamma suppression capability, laying a solid foundation for the development of neutron detector technology. Attached Figure Description

[0020] Figure 1 This is a ceramic GEM image under a microscope prepared by the method of the present invention.

[0021] Figure 2 This is a schematic diagram of the process flow for preparing ceramic GEMs using the laser drilling technology of this invention. Detailed Implementation

[0022] This invention proposes a high-precision ceramic GEM fabrication method based on short-pulse lasers, aiming to solve the problems of low precision, low efficiency, and low yield faced by traditional mechanical drilling techniques in the fabrication of large-area, high-density ceramic GEMs. The invention is described in detail below through specific embodiments.

[0023] like Figure 1-2 As shown, Figure 1This is a microscopic image of a ceramic GEM film prepared using the method of this invention. The image shows the structure of the ceramic GEM film observed under a microscope. Uniformly distributed circular micropores with consistent diameter, smooth edges, and no deformation or protrusions can be clearly seen in the image. This demonstrates that the ceramic GEM film prepared using short-pulse laser drilling technology has high precision and excellent surface quality. Figure 2 This is a schematic diagram of the process flow for preparing ceramic GEMs using the laser drilling technology of this invention. The diagram details the process flow of preparing ceramic GEMs using short-pulse laser technology. First, a solder resist layer is deposited on a copper-clad substrate. Then, through-holes are drilled using a short-pulse laser to form an array of vias. Next, the copper layer at the hole locations is acidically etched to form rim rings. Afterward, the solder resist layer is removed. The GEM film is then subjected to plasma cleaning. Finally, after cleaning, trimming, and baking, the preparation of the ceramic GEM is complete. This process intuitively demonstrates the innovation and practicality of the method of this invention.

[0024] like Figure 1-2 As shown, a high-precision ceramic GEM fabrication method based on short-pulse laser mainly includes the following steps: S1. Substrate preparation: Cover the copper-clad substrate on both sides with a solder mask to protect the surface copper layer. S2. Short-pulse laser drilling: Short-pulse lasers are used to drill through holes in the solder resist layer, copper layer and ceramic substrate to form through holes; S3. Acid etching to form rim rings: Acid etching is performed on the copper layer at the opening location to form rim rings to improve the GEM withstand voltage. S4. Remove solder mask: Remove the solder mask covering the surface; S5. Plasma cleaning treatment: Plasma cleaning treatment is performed on the GEM film after laser drilling to remove the carbonized material generated in the hole wall; S6. Cleaning, cutting and baking: Cleaning, cutting and baking are carried out to complete the preparation of ceramic GEM.

[0025] Example: High-precision ceramic GEM fabrication based on short-pulse laser S1: Substrate preparation In this embodiment, a ceramic substrate with double-sided copper plating is selected, with a substrate size of 200mm × 200mm and a copper plating thickness of 15μm. A photosensitive solder resist layer with a thickness of 20μm is covered on both sides of the substrate to protect the surface copper layer from damage during subsequent laser processing.

[0026] S2: Short-pulse laser drilling In this embodiment, a short-pulse laser with a pulse width in the picosecond range is used to drill holes in a ceramic substrate covered with a solder resist layer. The laser parameters are set as follows: wavelength 532nm, power 30W, and repetition frequency 100kHz. A precision laser alignment system ensures that the laser beam is accurately focused on the drilling location, and a through-hole array is formed by scanning point by point. During the drilling process, the laser parameters are monitored and adjusted in real time to obtain perfectly circular microholes with a diameter of 200μm and a spacing of 600μm.

[0027] S3: Acid etching forms a rim ring. In this embodiment, after drilling, the copper layer at the opening location is subjected to acid etching. Hydrochloric acid solution is used as the etching solution, and by controlling the etching time and temperature, the copper layer around the opening is precisely removed to form a rim ring with a width of 70 μm, thereby improving the pressure resistance of the GEM film.

[0028] S4: Remove solder mask In this embodiment, a chemical stripping method is used to completely remove the solder mask layers on both sides of the substrate, exposing the ceramic surface and the copper rim ring after drilling.

[0029] S5: Plasma Cleaning Treatment In this embodiment, the GEM film with the solder resist layer removed is placed in a CH4 and O2 mixed gas environment for plasma cleaning to remove the carbonized material generated inside the hole walls due to laser processing, ensuring the insulation performance of the GEM film. The volume ratio of CH4 to O2 in the cleaning gas is 1:2, and the cleaning time is 30 minutes.

[0030] S6: Cleaning, Cutting, and Baking In this embodiment, the GEM membrane after plasma cleaning is ultrasonically cleaned to remove surface residues. Subsequently, it is cut to the required size according to design requirements and baked at 120°C for 2 hours to remove internal moisture and improve pressure resistance.

[0031] In this embodiment, the ceramic GEM film prepared by the above steps has a thickness of 200 μm, a pore size of 200 μm, a pore spacing of 600 μm, and a rim ring width of 70 μm. Testing showed that the GEM film has high pore precision, good surface quality, and no deformation or protrusions, meeting the requirements of neutron detectors for high-performance GEM films.

Claims

1. A high-precision ceramic GEM fabrication method based on short-pulse laser, characterized in that, Includes the following steps: S1 substrate preparation: Cover the copper-clad substrate on both sides with a solder mask to protect the surface copper layer. S2 Short Pulse Laser Drilling: A short pulse laser is used to drill through holes in the solder resist layer, copper layer and ceramic substrate to form through holes. The laser drilling rate is 20,000 holes / min and the pulse width of the short pulse laser is in the order of ns, ps or fs. S3 Acid Etching to Form an Insulating Rim Ring: The copper layer at the opening location is acid-etched to form a rim ring used to improve the GEM withstand voltage. S4 Remove solder mask: Removes the solder mask covering the surface; S5 Plasma Cleaning Treatment: The GEM after laser drilling is subjected to plasma cleaning treatment to remove the carbonized material generated in the hole wall. The gas environment for plasma cleaning treatment is a mixture of CH4 and O2, and the volume ratio of CH4 to O2 is 1:

2. S6 Cleaning, Cutting and Baking: Cleaning, cutting and baking are performed to complete the preparation of ceramic GEM; The ceramic GEM is used with 3 A high-pressure neutron detector using He gas; the neutron detector has a large area, high count rate, high efficiency and high gamma suppression capability.

2. The high-precision ceramic GEM fabrication method based on short-pulse laser according to claim 1, characterized in that, The ceramic GEM has a thickness of 50 μm to 300 μm, a pore size of 50 μm to 200 μm, a pore spacing of 200 μm to 600 μm, and an insulating ring rim width of 40 μm to 80 μm.

3. The high-precision ceramic GEM fabrication method based on short-pulse laser according to claim 1, characterized in that, The solder resist layer is a photosensitive solder resist or other solder resist material suitable for laser processing.

4. The high-precision ceramic GEM fabrication method based on short-pulse laser according to claim 1, characterized in that, The etching solution used in the acid etching step is a hydrochloric acid solution or a sulfuric acid solution.

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