Second Surface Laser Ablation for Coating Removal
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Solution Overview
Problem
Existing laser ablation processes face challenges in precisely removing coating layers from substrates without redepositing the removed material, requiring complex masking techniques and additional tooling, and often result in edges with high transmission haze and scalloped profiles.
Innovation Solution
A method involving a laser beam that passes through the substrate from one surface to the other, with a mask on the opposite surface to selectively remove the coating layer, using picosecond or femtosecond pulses to achieve precise edge definition and minimize haze, allowing for the formation of sharp, uniform edges with controlled angles and reduced characteristic length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is directed at the coating layer from the first surface to remove the coating, then the coating layer can be removed, but the removed material redeposits on the substrate creating scalloped edges and high transmission haze
Solution Approach 1:
The patent inverts the conventional laser ablation approach by directing the laser beam from the second surface (substrate side) through the substrate to ablate the coating layer at the first surface. This reverse direction prevents redeposition of ablated material onto the substrate, eliminating scalloped edges and reducing transmission haze while maintaining effective coating removal.
2Manufacturing precision
If conventional laser ablation is used to remove coating layers, then material removal is achieved, but additional masking and tooling are required to prevent redeposition
Solution Approach 1:
By inverting the laser beam direction to illuminate from the second surface through the substrate, the patent eliminates the need for complex masking arrangements and tooling designed to prevent redeposition. The physical geometry of the reversed ablation process inherently prevents material from falling back onto the substrate, simplifying the overall system.
Solution Approach 2:
The patent extracts and removes the unnecessary masking and complex tooling components from the conventional laser ablation system. By utilizing the substrate's transparency and reversing the beam direction, the solution eliminates redundant elements that were previously needed to manage redeposition issues.
3Measurement precision
If the laser beam is focused to create small ablation spots, then precise removal is achieved, but the edges exhibit scalloped profiles and high haze
Solution Approach 1:
The patent inverts the ablation direction to eliminate the scalloped edge profile problem. By ablating from the second surface through the substrate, the process prevents material redeposition that causes scalloping, while maintaining precise spot control for accurate pattern formation.
4Adaptability or versatility
If the substrate is made transparent to allow laser passage, then second surface ablation is enabled, but the substrate material selection is limited
Solution Approach 1:
The patent applies parameter changes by selecting specific laser wavelengths that match the transmission properties of particular substrate materials. By adjusting the laser wavelength parameter, the system can work with different transparent or translucent substrate materials, expanding material selection flexibility while maintaining effective second surface ablation.
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 enables precise removal of coating layers with edges that taper to zero thickness over short lengths, reducing transmission haze and producing smooth, uniform edges, eliminating the need for additional masking and tooling, and allowing for flexible pattern formation without redepositing material.
Implementation Method 1
removing a portion of the coating layer from the workpiece by directing a laser beam at the workpiece such that the laser beam passes through the substrate from the second surface to the first surface before the laser beam impinges on the coating layer
Implementation Method 2
producing confined vaporised coating material which causes an overlying region of coated material to be removed from the substrate
Data Source
Figure 1~2
Figure 3(a)~4(b)
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AI summary
A method of removing material from an opposite side of workpiece includes directing a laser beam at a first side of the workpiece to remove the material from an opposite second side of the workpiece. In a first aspect, a method is provided comprising: providing a workpiece comprising a substrate, a coating layer disposed over a first surface of the substrate, and a mask disposed over a second surface of the substrate; and removing a portion of the coating layer from the workpiece by directing a laser beam at the workpiece such that the laser beam passes through the substrate from the second surface to the first surface before the laser beam impinges on the coating layer.