Laser Scribe Method for Sapphire Using Birefringent Beam Splitting
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Solution Overview
Problem
Laser processing of hard and brittle materials like glass and sapphire often results in irregular cracks due to thermal stress, making uniform cutting difficult, and existing methods require specialized equipment or cooling processes that are inefficient and prone to deformation.
Innovation Solution
A laser scribe processing method that splits a laser beam into ordinary and extraordinary components, forming multiple pairs of beam spots to control crack directionality and minimize thermal stress, allowing for uniform and symmetrical cutting by adjusting the beam spot positions and intensities using a birefringent prism and polarization elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is irradiated onto a board formed from a noncrystalline hard and brittle material, then thermal processing occurs to cut the material, but irregular cracks are formed due to strain stress generated concurrently with thermal processing
Solution Approach 1:
The laser beam is divided into multiple beams (e.g., three beams) that irradiate different regions of the material simultaneously. This segmentation allows thermal processing to occur in multiple locations, distributing the thermal stress and preventing the formation of irregular cracks that would result from concentrating all energy in a single spot.
Solution Approach 2:
Each laser beam is focused to create a specific beam waist position at a predetermined depth below the surface of the material. By controlling the focal depth and positioning multiple beam waists at different locations, the thermal processing is localized to specific regions, enabling precise crack formation along the desired cutting path while minimizing unwanted thermal stress in other areas.
2Manufacturing precision
If a special light converging optical system is used to prevent generation of cracks, then crack prevention is achieved, but device complexity increases
Solution Approach 1:
Instead of using a complex special optical system to control a single beam, the invention segments the laser beam into multiple simpler beams that can be focused using standard optical components. Each beam is focused to a predetermined depth, and by controlling the relative positions of these multiple beam waists, crack control is achieved through distributed thermal processing rather than through complex single-beam control mechanisms.
3Productivity
If thermal stress is greatly increased to execute cutting using a laser beam, then cutting capability is improved, but deformation of the board and occurrence of nonuniform torn surface occur
Solution Approach 1:
The total laser energy required for cutting is distributed across multiple beams irradiating different regions simultaneously. This segmentation of energy delivery allows the material to be processed through distributed thermal stress rather than concentrated thermal shock, maintaining high cutting efficiency while preventing excessive localized heating that would cause deformation and nonuniform torn surfaces.
Solution Approach 2:
The laser beams are irradiated in a controlled sequence or simultaneously with controlled timing, creating a periodic or synchronized thermal processing pattern. This controlled temporal distribution of thermal energy allows the material to undergo gradual thermal stress changes rather than sudden thermal shock, reducing deformation while maintaining cutting efficiency.
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 enables efficient, uniform, and symmetrical cutting of hard and brittle materials by forming controlled cracks along desired directions, reducing thermal stress and deformation, and simplifying the processing steps while improving operational efficiency.
Implementation Method 1
a splitting step of splitting the laser beam into an ordinary light component and an extraordinary light component having different travel directions
Implementation Method 2
a laser converged spot (beam waist) having an elevated power density is irradiated onto a board to cut the board
Implementation Method 3
irregular cracks are formed that result from strain stress generated concurrently with thermal processing
Data Source
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AI summary
An object of the invention is to provide a laser scribe processing method for use inprocessing of a hard and brittle material such as sapphire. An aspect of the present invention is a laser scribe processing method of forming a crack that runs along a scribe direction of a processing target substance using a light source that emits a laser beam, and an optical system for irradiation that leads the laser beam onto the processing target substance, the method including: an emission step of emitting a laser beam from the light source; a splitting step of splitting the laser beam into an ordinary light component and an extraordinary light component having different travel directions; a light converging step of converging the ordinary light component and the extraordinary light component to form multiple pairs of beam spots; and an irradiation step of intermittently irradiating with the laser beam having multiple pairs of beam spots in a scribe direction of the processing target substance. For splitting the ordinary light component and the extraordinary light component in the splitting step, a birefringent prism disposed in the optical system for irradiation may be used.