Ultrashort Pulse Laser Fluence Switching for Protrusion Control
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Solution Overview
Problem
During ultrashort pulse laser processing, protrusions with elliptical cross-sections can form on the surface of target layers, leading to decreased processing quality, especially in deep holes. High fluence can suppress protrusion growth but increases thermal effects and reduces surface precision.
Innovation Solution
A laser processing device that switches the fluence of the pulse laser beam between low and high fluence based on predefined switching conditions, using a control device with a switching unit and a switching condition setting unit to manage the fluence switching during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ultrashort pulse laser is irradiated at high fluence to suppress protrusion generation, then protrusion growth is suppressed, but thermal effect on material increases and surface precision decreases
Solution Approach 1:
The patent applies periodic action by alternately switching between high fluence and low fluence irradiation modes. The control device monitors protrusion generation in real-time and periodically switches the fluence level: using high fluence when protrusions are detected and low fluence when the surface is smooth, thereby achieving protrusion suppression while minimizing thermal accumulation
Solution Approach 2:
The patent changes the fluence parameter dynamically based on the processing state. The control device adjusts the laser fluence between high and low levels according to whether protrusions are generated, making the fluence parameter adaptive rather than fixed. This resolves the contradiction by applying high fluence only when necessary for protrusion suppression while using low fluence otherwise to minimize thermal effects
2Object-affected harmful factors
If ultrashort pulse laser is irradiated at low fluence to minimize thermal effect, then surface precision is maintained, but protrusions are generated and grow on the surface
Solution Approach 1:
The patent implements feedback control where the control device continuously monitors the workpiece surface for protrusion generation and adjusts the laser fluence accordingly. When protrusions are detected, the system feedbacks by switching to high fluence mode to suppress them; when no protrusions are present, it switches to low fluence mode to minimize thermal effects. This closed-loop feedback resolves the contradiction by making fluence selection dependent on actual surface conditions
Solution Approach 2:
The patent makes the fluence level dynamic rather than static. The control device transitions between low fluence and high fluence states based on real-time detection of protrusion generation. This dynamic adjustment allows the system to adapt to changing surface conditions, maintaining low thermal effects during normal processing while activating high fluence only when protrusions threaten surface precision
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
This approach minimizes high-fluence processing, reducing thermal effects and maintaining surface precision while effectively removing protrusions, thus enhancing the overall processing quality.
Implementation Method 1
When a workpiece is irradiated with an ultrashort pulse laser having a pulse width on the order of equal to or less than a single picosecond, a material in an irradiated portion is non-thermally dispersed and removed (ablation).
Data Source
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Figure 3A~3B
AI summary
According to the present invention, provided is a laser processing device, including: an irradiation device, and a control device. The irradiation device is configured to process one or more target layers sequentially from the workpiece by irradiating the target layers with a pulse laser beam having a pulse width of less than 10 picoseconds at a predetermined low fluence, and to removing a protrusion generated on a surface of the target layers by irradiation with the pulse laser beam at a high fluence higher than the low fluence. The control device includes a switching unit and a switching condition setting unit. The switching unit switches the pulse laser beam output from said irradiation device between the low fluence and the high fluence based on switching conditions.