Brittle-Hard Substrate Cleaving via Pulsed Laser Filamentation
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Solution Overview
Problem
Current methods for cutting glass substrates, such as mechanical scribing and breaking, water-jet cutting, and thermal laser scribing, face limitations in achieving high-quality, free-form geometries, especially for materials with low thermal expansion coefficients, leading to issues like crack deviation and edge quality problems during the cleaving process.
Innovation Solution
A method utilizing pulsed laser filamentation to introduce defects along a predetermined separation line in glass, glass ceramics, or silicon substrates, optimizing the breaking stress and edge strength by controlling the spacing and number of laser pulses, allowing for precise separation and improved edge quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal laser scribing is used to cut glass substrates, then high edge quality and free-form geometries are achieved, but the method is not suitable for glasses with low coefficient of thermal expansion or greater thickness
Solution Approach 1:
The patent changes the fundamental cutting mechanism from thermal (CO2 laser heating) to mechanical (ultrashort pulsed laser-induced stress). By using ultrashort pulses with durations in the picosecond or femtosecond range, the laser energy is deposited so quickly that thermal diffusion is minimized, eliminating the thermal expansion issue while maintaining precise cutting capability.
Solution Approach 2:
The patent employs periodic ultrashort laser pulses spaced at specific intervals along the cutting line. The pulse repetition rate and spacing are carefully controlled to create a periodic stress field that propagates a clean crack through the material without thermal accumulation, enabling precise cutting of thermally sensitive materials.
2Ease of manufacture
If mechanical scribing and breaking is used to cut glass substrates, then cost-effective straight cuts are achieved, but complex geometries and high edge quality are not possible
Solution Approach 1:
The patent replaces the traditional mechanical scribing tool with an optical field (ultrashort pulsed laser). The laser induces stress fields within the glass that create controlled fracture paths, substituting mechanical contact with non-contact optical-mechanical interaction. This enables complex geometries while maintaining cost-effectiveness by eliminating mechanical tool wear and post-processing requirements.
3Adaptability or versatility
If water-jet cutting is used to achieve free-form geometries in glass substrates, then complex shapes are possible, but the process is slow, expensive, and produces limited edge quality requiring post-processing
Solution Approach 1:
The patent utilizes the phase transition of laser energy from optical to mechanical stress field. The ultrashort pulsed laser creates localized plasma and shock waves that propagate through the glass, causing rapid fracture. This phase transition enables high-speed cutting without the mechanical removal process required by water-jet cutting, significantly increasing productivity while maintaining geometric flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables successful separation of substrates with low thermal expansion coefficients, achieving high edge quality and allowing for larger positional tolerances during the cleaving process, reducing the need for post-processing and increasing cutting speed.
Implementation Method 1
it is assumed that the non-linear optical Kerr effect causes self-focusing of the laser beam thereby causing plasma formation
Implementation Method 2
the non-linear optical Kerr effect causes self-focusing of the laser beam thereby causing plasma formation
Implementation Method 3
the non-linear optical Kerr effect causes self-focusing of the laser beam thereby causing plasma formation
Implementation Method 4
the glass is heated, for example by a CO2 laser, along the cutting line
Implementation Method 5
the glass is heated, for example by a CO2 laser, along the cutting line and is immediately cooled down again
Data Source
AI summary
A method for separating a substrate of a brittle-hard material is provided. The method includes the steps of introducing defects into the substrate at a spacing from one another along a separation line using at least one pulsed laser beam; selecting an average spacing between neighboring defects and a number of laser pulses for generating a respective defect such that a breaking stress (σB) for separating the substrate along the separation line is smaller than a first reference stress (σR1) of the substrate and such that an edge strength σK of the separation edge obtained after separation is greater than a second reference stress (σR2) of the substrate; and separating the substrate after introducing the defects by applying a stress along the separation line.