Laser Wafer Cutting With Liquid Jet Cooling
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Solution Overview
Problem
Existing laser machining methods face challenges with material ejections adhering to the workpiece surface, inefficient cooling, and the need for subsequent cleaning, as well as difficulties in expelling melt and managing laser beam quality due to liquid layers used for cooling.
Innovation Solution
A method involving a thin liquid layer (less than 1 mm thick) on the workpiece surface, generated by a liquid jet with high velocity, which allows undisturbed laser radiation penetration, effective cooling, and efficient ejection of material residues, eliminating the need for cutting gas and subsequent cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a liquid layer is used for cooling the workpiece during laser machining, then cooling efficiency is improved, but the laser beam is disturbed (refraction, diffusion, damping) causing loss of sharpness and energy
Solution Approach 1:
The patent applies a thin liquid layer selectively at the operating point where laser machining occurs, rather than covering the entire workpiece. This localized application provides cooling exactly where needed (at the laser interaction zone) while minimizing the liquid layer thickness to less than 1mm to reduce optical disturbance. The liquid layer is generated by a liquid jet directed at the workpiece surface in the machining region, ensuring cooling efficiency is maintained without significantly compromising laser beam quality.
2Object-generated harmful factors
If a thicker liquid layer is used to flush away ejections, then ejection removal is improved, but laser radiation penetration is disturbed
Solution Approach 1:
The patent optimizes the liquid layer thickness parameter to be less than 1mm (specifically between 0.01mm and 0.5mm according to preferred embodiments). This parameter change allows the liquid layer to be sufficiently thick to flush away material ejections and cool the workpiece, yet thin enough to permit effective laser radiation penetration. The high velocity of the liquid jet (achieved through pressurization) enhances the flushing capability within this constrained thickness range, resolving the contradiction between ejection removal and laser energy transmission.
3Productivity
If a liquid jet with high velocity is used to generate the liquid layer, then ejection flushing is improved, but device complexity increases
Solution Approach 1:
The patent employs a liquid jet (typically water) directed at the workpiece surface to generate the thin liquid layer and flush away ejections. The liquid jet system utilizes hydraulic principles where pressurized liquid flows through nozzles to create high-velocity streams. This approach leverages readily available hydraulic infrastructure and simple nozzle designs to achieve high flushing efficiency without requiring complex mechanical or electronic systems. The liquid jet can be easily controlled by adjusting flow rate and pressure, providing an economically simple yet effective solution.
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
Enables precise, efficient machining with minimal surface contamination, effective cooling, and extended laser beam length, allowing for narrow deep cuts and drillings with perpendicular side walls, while preventing vapor and odor binding.
Implementation Method 1
laser radiation is injected into a liquid jet which acts as a light guide
Implementation Method 2
the liquid at the same time acts as a coolant which efficiently cools the workpiece in the machining region
Implementation Method 3
vapors, particles and aerosols which occur during machining by laser radiation can be bound or prevented
Data Source
AI summary
The invention relates to a device (1) for cutting wafers (2) into a number of chips with a laser beam (6) injected into a liquid jet (7). A thin flowing liquid layer (9) having a blasting effect is produced on the surface (5) of the wafer (2). This makes it possible to prevent projections resulting during laser cutting from depositing once again on the surface of the wafer. The result is a very high cleanness of the surface after the cutting process. The liquid layer (9) is produced, in particular, so that it is thinner in a machining area (10) around the machining point (8) than outside of the machining area (10). This ensures that the liquid layer is sufficiently thin (14) at the machining point (8) so that enough laser energy for removing material is applied to the wafer surface, and ensures that the liquid layer is sufficiently thick (15) outside of the machining area so that no area of the surface (5) of the wafer (2) dries out.