Laser Filament Separation of Brittle Substrates With Strong Edges
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Solution Overview
Problem
Current methods for cutting glass, glass ceramics, and silicon substrates, such as mechanical cracking, water jet cutting, and thermal laser scribbling, face limitations in achieving high-quality edges with free-form geometries, especially for materials with low thermal expansion coefficients, leading to inconsistent crack propagation and the need for post-processing.
Innovation Solution
A process using pulsed laser beams to create filament-shaped damage along a predetermined dividing line, optimizing the average distance between laser pulses and the number of pulses to achieve a fracture voltage that is lower than the material's reference voltage, while ensuring high edge resistance, allowing for precise separation with improved edge quality and reduced post-processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical scoring and breaking is used for cutting glass, then the process is cost-effective and simple, but the edges lack sufficient quality and require extensive post-processing
Solution Approach 1:
The patent replaces the mechanical scoring and breaking system with a laser-based system. The laser introduces damages along the separation line by heating the glass, and subsequent cooling creates thermal stresses that propagate cracks along the desired path, eliminating the need for mechanical contact and achieving high edge quality without extensive post-processing
Solution Approach 2:
The patent utilizes phase transitions of glass under thermal stress. By rapidly heating the glass along the separation line with a laser and then cooling it, the glass undergoes thermal expansion and contraction cycles that create controlled cracks along the separation line, achieving precise cutting with high edge quality
2Adaptability or versatility
If waterjet cutting is used for free-form geometries, then complex shapes can be produced, but the process is slow and expensive with limited quality requiring further edge processing
Solution Approach 1:
The patent replaces the waterjet mechanical cutting system with a laser-based thermal process. The laser can follow complex free-form paths while maintaining high cutting speeds, and the thermal stress mechanism produces clean edges that minimize or eliminate the need for post-processing, thereby increasing productivity
Solution Approach 2:
The patent employs periodic laser pulsing to create a sequence of damages along the separation line. By controlling the pulse frequency and duration, the process efficiently creates the desired crack pattern along complex geometries at high speed, improving productivity compared to continuous waterjet cutting
3Manufacturing precision
If thermal laser scribing is used for high edge quality, then freeform geometries can be achieved, but the process is not suitable for thicker glasses or glasses with low thermal expansion coefficient
Solution Approach 1:
The patent segments the cutting process into two distinct stages: first, introducing damages along the separation line using a laser with appropriate pulse parameters, and second, propagating cracks through thermal stress application. This segmentation allows optimization of each stage for different material properties, including thicker glasses and materials with low thermal expansion coefficients
Solution Approach 2:
The patent employs parameter changes in the laser pulse characteristics (duration, energy, frequency) and thermal stress application to adapt the process to different materials and thicknesses. By adjusting these parameters, the process achieves high edge quality across a wide range of materials including those with low thermal expansion coefficients that were previously unsuitable
4Manufacturing precision
If laser filamentation with CO2 laser tracing is used for separation, then the substrate can be separated along the filament path, but errors occur with complex geometries or low thermal expansion coefficient materials where the crack does not follow the predetermined line
Solution Approach 1:
The patent applies preliminary action by first introducing a systematic pattern of damages along the entire separation line using laser pulses before attempting crack propagation. This preliminary damage pattern is optimized based on material properties, ensuring that when thermal stress is applied, cracks will reliably follow the predetermined line even for complex geometries and materials with low thermal expansion coefficients
Solution Approach 2:
The patent incorporates feedback mechanisms by optimizing the damage introduction parameters based on the specific material properties (including thermal expansion coefficient) and geometry being processed. This feedback approach ensures reliable crack propagation along the predetermined separation line across different material types and geometric complexities
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 process enables precise separation with high edge quality, minimizing the need for post-processing and allowing for complex geometries, including those with low thermal expansion coefficients, by controlling the fracture voltage and edge resistance, resulting in reliable and efficient cutting with improved edge strength and reduced operational costs.
Implementation Method 1
A filament is created using a high-energy, short laser pulse, and it is assumed that the nonlinear optical Kerr effect leads to self-focusing of the laser beam, thereby causing plasma formation.
Implementation Method 2
This involves using an ultrashort pulse laser to create a dividing line, e.g., in the form of a perforation, in the glass.
Implementation Method 3
In the thermal laser scribing process, the glass is heated along the cutting line using a CO2 laser, for example, and then immediately cooled down again.
Data Source
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AI summary
The invention relates to a method for separating a substrate, in particular made of a brittle-hard material, in which faults are introduced into the substrate at a distance to one another along a predetermined separation line using at least one pulsed laser beam, wherein both the average distance between neighbouring faults and the number of laser pulses for generating a respective fault is selected in that: a) the breaking tension σB for separating the substrate along the separation line is smaller than a first reference tension σR1 according to the respective substrate; b) the edge strength σK of the separation edge obtained after the separation is greater than a second reference tension σR2 according to the respective substrate; and c) after introducing the faults, the substrate can be separated by inflicting a tension along the separation line.