Laser Substrate Cutting With Overlapped Sub-Threshold Pulses
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Solution Overview
Problem
Existing methods for cutting thin substrates like glass and ceramics suffer from low processing speeds, reduced edge quality, and unwanted damage due to laser ablation, particularly at the edges and depths below the surface, leading to micro-cracks, residual stress, and phase changes.
Innovation Solution
A method using ultrashort sub-nanosecond laser pulses with an elongate cross-sectional profile and controlled fluence below the single shot damage threshold, combined with spatial overlap along a cutting path, to minimize thermal stress and improve edge quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser ablation is used to cut thin substrates, then cutting capability is achieved, but material damage and micro-cracks increase
Solution Approach 1:
The patent applies periodic pulsed laser action instead of continuous laser exposure. By delivering energy in discrete pulses with controlled duration (nanosecond to picosecond range) and spacing, the material accumulates damage gradually through repeated cycles, enabling complete cutting while controlling the severity of damage at each stage. This periodic approach allows the material to respond differently to each pulse, building up the desired cut profile without excessive single-shot damage.
Solution Approach 2:
The patent applies preliminary low-fluence laser pulses before the main cutting operation. These initial pulses create a modified surface layer or stress pattern that facilitates subsequent cutting with reduced overall damage. The preliminary action prepares the material by creating a more favorable state for the main cutting process, reducing the energy required for subsequent pulses and thereby reducing cumulative damage.
2Productivity
If high fluence laser pulses are used, then ablation threshold is exceeded and cutting occurs, but thermal stress and heat affected zone increase
Solution Approach 1:
The patent uses periodic pulsed laser delivery with carefully controlled pulse duration in the nanosecond to picosecond range. This periodic action allows thermal diffusion to occur between pulses, preventing excessive heat accumulation. The pulse timing and duration are optimized so that each pulse delivers sufficient energy for ablation while allowing partial cooling between pulses, thereby maintaining ablation efficiency while minimizing the heat affected zone and thermal stress.
Solution Approach 2:
The patent changes the temporal parameters of laser delivery by using ultrashort pulses (nanosecond to picosecond duration) instead of continuous or long-pulse delivery. This parameter change fundamentally alters the thermal interaction with the material, enabling ablation with minimal heat diffusion. The pulse duration is specifically selected to be shorter than the thermal diffusion time scale, confining thermal effects to a very small zone while maintaining effective cutting.
3Productivity
If laser processing is used on thin substrates, then cutting is achieved, but edge quality deteriorates
Solution Approach 1:
The patent applies periodic pulsed laser action with optimized pulse duration and repetition rate to achieve clean edges on thin substrates. The pulsed nature allows precise control over material removal, creating a more controlled ablation process that produces cleaner edges compared to continuous laser processing. The periodic delivery enables better control over the ablation front propagation, resulting in improved edge quality while maintaining cutting speed.
Solution Approach 2:
The patent changes the temporal parameters of laser delivery by using ultrashort pulses (nanosecond to picosecond duration) which fundamentally alters the ablation mechanism. This parameter change enables precise material removal with minimal thermal diffusion, producing cleaner edges with less melting and resolidification. The ultrashort pulse duration confines the energy deposition to a very short time window, improving edge quality while maintaining effective cutting of thin substrates.
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 achieves precise cutting with reduced thermal stress, minimal micro-cracking, and improved edge quality, suitable for scalable manufacturing of thin substrates.
Implementation Method 1
Laser ablation is the ejection of matter from a surface following exposure to a beam of laser energy
Implementation Method 2
The laser energy is distributed in a cross-sectional spatial profile. Typically this profile is Gaussian, and is therefore most intense in the centre and least intense at the edges of the beam
Implementation Method 3
the greater the ablation threshold fluence, the greater the impact this damage has on the material and the effectiveness of laser cutting, drilling and scribing processes
Data Source
AI summary
The present application relates to a method (100) for use in cutting a substrate or preparing a substrate for cleaving. The method (100) comprises: irradiating (102) the substrate with a plurality of pulses of a laser beam, the pulses having a pulse duration of less than a nanosecond and an elongate cross sectional spatial profile, and wherein the fluence of the plurality of pulses is controlled to be less than a single shot damage threshold fluence of the substrate; providing (104) relative movement between the laser beam and the substrate such that the plurality of pulses are arranged along a cutting path; and controlling (106) the relative movement such that each of the pulses is spatially overlapped with at least one other of the pulses along the cutting path. An apparatus having a laser system configured to perform the method (100) is also disclosed.