Brittle-Hard Substrate Separation Using Laser Filament Defects
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Solution Overview
Problem
Existing methods for laser-assisted substrate separation, such as mechanical scribing and breaking, water-jet cutting, and thermal laser scribing, face limitations in producing high-quality cuts, especially for complex geometries and materials with low thermal expansion, leading to issues like edge quality and crack deviation.
Innovation Solution
A method using ultrashort pulsed laser beams to introduce filamentary defects along a separation line, optimizing the breaking stress and edge strength by controlling the spacing and number of laser pulses, allowing for precise cleaving with improved edge quality and tolerance to laser spot deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal laser scribing is used to heat and cool glass along the cutting line, then high edge qualities are achieved, but the method is not suitable for glasses with greater thickness or low coefficient of thermal expansion
Solution Approach 1:
The patent changes the fundamental parameter of the laser interaction mechanism from thermal heating/cooling cycles to ultrashort pulse-induced filamentation. This parameter change enables the method to work effectively on thick glasses and glasses with low thermal expansion coefficients, which are incompatible with thermal laser scribing.
Solution Approach 2:
The patent replaces the thermal field-based cutting mechanism with a mechanical field-based mechanism (ultrashort laser pulses creating filamentation and micro-explosions). This substitution eliminates the limitations imposed by thermal diffusion and thermal stress, enabling successful cutting of materials that are resistant to thermal processing.
2Ease of manufacture
If mechanical scribing and breaking is used for cutting, then the method is cost-effective, but it is essentially limited to straight cuts and requires complex post-processing
Solution Approach 1:
The patent replaces the mechanical scribing system with an optical field-based laser filamentation system. This substitution enables free-form geometry cutting while maintaining cost-effectiveness, as the laser method eliminates the need for expensive post-processing operations like grinding and polishing.
Solution Approach 2:
The patent performs preliminary action by creating filamentation paths and separation lines before the actual breaking occurs. This preliminary structuring of the glass along the desired separation path enables both complex geometries and high edge quality without post-processing.
3Adaptability or versatility
If water-jet cutting is used to achieve free-form geometries, then the method allows complex shapes, but it is slow and expensive with limited quality requiring further post-processing
Solution Approach 1:
The patent replaces the water-jet mechanical cutting system with an ultrashort laser pulse system. This substitution dramatically increases cutting speed while maintaining the ability to produce free-form geometries and achieving high edge quality that eliminates post-processing requirements.
Solution Approach 2:
The patent uses periodic ultrashort laser pulses to create filamentation along the cutting path. This periodic action enables rapid material modification along complex geometries, achieving both high speed and geometric flexibility simultaneously.
4Productivity
If laser filamentation with CO2 laser tracing is used for cleaving, then separation is achieved, but errors occur such as crack deviation or stopping, especially for complex geometries or materials with low coefficient of thermal expansion
Solution Approach 1:
The patent performs preliminary action by creating precise filamentation paths with ultrashort laser pulses before the cleaving step. These pre-formed structural weaknesses guide the crack accurately along the intended separation line, preventing deviation or stopping even in complex geometries and low thermal expansion materials.
Solution Approach 2:
The patent replaces the thermal tracing mechanism with a mechanical field-based ultrashort laser pulse system that creates permanent structural modifications. This substitution ensures reliable crack guidance independent of the material's thermal expansion properties, significantly improving crack accuracy and reliability.
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
Achieves high-quality separation edges with reduced need for post-processing, enabling faster cutting speeds and successful separation in materials with low thermal expansion, even with larger laser spot deviations.
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.