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KR-102963908-B1 - Method and apparatus for forming a hole in a brittle material supported by stress reduction through heating

KR102963908B1KR 102963908 B1KR102963908 B1KR 102963908B1KR-102963908-B1

Abstract

A method for making a brittle substrate comprises: (i) heating at least a portion of a substrate to a depth (d) at a temperature (Tp) higher than 500 °C but lower than 1500 °C to form a heated region of the substrate; and (ii) irradiating at least a portion of the heated region of the brittle substrate with a laser beam emitted from an IR laser to form at least one hole in the brittle substrate.

Inventors

  • 아브라모브, 아나톨리 아나톨리에비치
  • 베커, 알레잔드로 안토니오

Assignees

  • 코닝 인코포레이티드

Dates

Publication Date
20260513
Application Date
20200828
Priority Date
20190830

Claims (20)

  1. A method for making a brittle substrate having at least one hole with a depth (d) (μm), wherein the method comprises: (i) heating at least a portion of a substrate to at least a depth (d) at a temperature (Tp) greater than 600 °C and less than 1500 °C to form a heated zone of the substrate, wherein the temperature (Tp) is below the softening point temperature of the substrate material and exceeds the annealing temperature of the substrate material; (ii) irradiating at least a portion of a heated area of a brittle substrate with a laser beam emitted from an IR laser to form at least one hole in the brittle substrate; and (iii) a step of maintaining the substrate or the area around the at least one hole for at least 1 to 30 minutes at a temperature 100°C or lower than the softening point temperature and higher than the annealing temperature after forming at least one hole.
  2. In claim 1, The brittle substrate is a glass, glass-ceramic, or ceramic substrate, method.
  3. In claim 1, A method further comprising the step of supporting the heated substrate while moving the heated substrate and the laser beam relative to each other.
  4. In claim 1, A method in which 600 ℃ < Tp ≤ 900 ℃.
  5. In claim 1, The laser beam is at least 5 kW/ cm² defined by P d = P 0 /S A method having an output density (P d ) (W/cm 2 ), where P 0 and S are the output and cross-sectional area of the laser beam on the substrate surface, respectively.
  6. In any one of claims 1 to 5, The above heating step is: A method comprising the step of heating the entire substrate to a temperature (Tp), wherein the temperature (Tp) is at least 10°C lower than the softening point temperature of the substrate material.
  7. In any one of claims 1 to 5, The above heating step is: A method comprising the step of heating at least one portion of the substrate to a temperature (Tp) by a defocused pulsed laser beam or a CW laser beam.
  8. In any one of claims 1 to 5, The laser beam is focused onto the substrate surface by a focusing optical component into a spot with a diameter (D) ≤ 0.5 mm; A method in which a laser beam is emitted from a CO2 or CO2 laser at each irradiation position for an irradiation time (t), wherein the irradiation time (t) is 0.1 ms to 500 ms.
  9. In claim 8, Method where D ≤ 0.25 mm.
  10. In claim 9, Method where D ≤ 0.1 mm.
  11. In claim 10, Method where D ≤ 0.05 mm.
  12. In claim 8, A method in which D ≤ 0.25 mm and the irradiation time (t) at each irradiation location is 0.1 ms to 250 ms.
  13. In claim 8, A method in which the irradiation time (t) at each irradiation location is 0.1 ms to 25 ms.
  14. In claim 8, A method in which the irradiation time (t) at each irradiation location is 0.1 ms to 2.5 ms.
  15. In any one of claims 1 to 5, A method in which 30 µm ≤ d ≤ 5000 µm.
  16. In claim 15, A method in which the hole diameter is 30 μm to 500 μm.
  17. In any one of claims 1 to 5, Method in which an IR laser is a pulsed laser operating in burst mode.
  18. In any one of claims 1 to 5, The hole is a penetrating hole, method.
  19. In any one of claims 1 to 5, A hole is a tapered hole, wherein the hole has an inlet hole diameter and an outlet hole diameter, and the inlet hole diameter is larger than the outlet hole diameter.
  20. In claim 19, A method in which the ratio of the inlet hole diameter to the outlet hole diameter is at least 1.1.

Description

Method and apparatus for forming a hole in a brittle material supported by stress reduction through heating This application claims priority to U.S. Provisional Application No. 62/894335 filed August 30, 2019, and U.S. Provisional Application No. 62/894132 filed August 30, 2019, the entirety of which is incorporated herein by reference. The present disclosure relates to a laser forming method for a hole in a glass substrate, a glass substrate, and a hole forming apparatus. Known laser ablation-based hole formation methods on brittle materials or substrates made of brittle materials (e.g., glass, glass-ceramic, or ceramic substrates in which stress fracture or cracking occurs without significant plastic deformation) have the problem of crack formation during or immediately after hole formation around the hole and on the inner wall of the hole or in a zone near the wall. If removed without being treated by etching, the cracks can reduce the strength of the substrate and eventually cause substrate failure. Etching is time-consuming and adds cost to the final substrate containing such holes. It is not acknowledged that all references cited herein constitute prior art. The applicant expressly reserves the right to object to the accuracy and appropriateness of the cited documents. FIG. 1 is a schematic cross-sectional view of a device for forming a laser hole in a brittle substrate according to one embodiment. FIG. 2 is a schematic cross-sectional view of another embodiment of a device for laser hole formation in a brittle substrate. FIG. 3 is a schematic diagram of a third embodiment of a device for forming laser holes in a brittle substrate. FIG. 4a shows a comparative example of a laser-drilled hole formed on a glass substrate at room temperature by a comparative method, showing the formation of an "arc" crack around the hole. FIG. 4b corresponds to FIG. 4a but shows a comparative example of a laser-drilled hole with a crack propagating through a substrate. FIG. 4c shows an exemplary drilled hole in which no “arc” crack is formed when a hole is formed in a glass substrate after the glass substrate is heated to a temperature higher than the annealing point, utilizing one embodiment of the method described herein. FIG. 5a shows a comparative example of a laser-drilled hole formed on a different glass substrate at room temperature by a comparative method, and also shows the formation of an "arc" crack around the hole. FIG. 5b shows an exemplary laser-drilled hole formed in a glass substrate after the glass substrate is heated to a temperature higher than the annealing point, utilizing one of the embodiments of the method described herein. FIG. 6 shows an example of a laser-drilled hole made in a glass-ceramic substrate after the glass-ceramic substrate is heated to a temperature higher than the annealing point, utilizing one of the embodiments of the method described herein. The strength of thin (i.e., < 5 mm thick) brittle substrates (e.g., glass-ceramic substrates, ceramic substrates, or glass substrates such as oxide-based glass) can be significantly lower than theoretical strength due to defects and flaws on the substrate surface. These defects and flaws can concentrate stress 10 to 100 times more than in substrate materials that do not contain holes. This lowers the material's fracture threshold and leads to substrate fracture. Once concentrated, the stress reaches a level capable of breaking atomic bonds, and fracture begins in the substrate. During the formation of holes in brittle materials by laser support, stress is concentrated in the substrate material (including the surface and the zone directly adjacent to the hole), which can cause undesirable cracking in the brittle material. Brittle materials are those that fracture or crack under stress without significant plastic deformation. Brittle materials can be, for example, glass, glass-ceramic, or ceramic. Therefore, it is important to minimize stress on the substrate material during hole formation. The applicant has discovered that, surprisingly, heating a substrate to a temperature (Tp) of less than 1500 °C but exceeding 500 °C results in significant and rapid transient stress relief during hole formation (e.g., through laser drilling and/or ablation), and that this stress relief suppresses crack formation around the hole in the brittle substrate, particularly during such hole formation. Some embodiments of the method and apparatus described herein utilize a pulsed laser beam to form a hole in a substrate made of a brittle material, while the substrate is heated to a temperature exceeding 600 °C but less than 1000 °C (e.g., between 600 °C and less than 850 °C). Heating the substrate (preheating) before hole formation, heating the substrate during hole formation, and preferably heating the substrate for at least 1 to 30 minutes after hole formation, or maintaining the substrate temperature above 500°C but below 1500°C (or, for example, above 600°C and