Double-Sided Laser Cutting for Crack-Resistant Waveguide Glass
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Solution Overview
Problem
Glass optical waveguides in eyewear devices face reliability issues due to micro-cracks and flaws generated during the cutting and singulation process, leading to poor drop test performance, as they are not chemically strengthened and traditional laser cutting methods create larger defects.
Innovation Solution
A double-sided laser cutting process is employed, where lasers cut partially into the wafer from both sides simultaneously or sequentially, reducing the power requirement and minimizing micro-cracks by cutting to different depths, such as 50% or 30% and 70%, to enhance glass strength and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional single-sided laser cutting is used to cut the wafer, then the cutting process is simple, but micro-cracks and flaws are generated leading to poor glass strength
Solution Approach 1:
The cutting process is segmented into two separate operations: a first laser cut from the first surface to a first depth, and a second laser cut from the second surface to a second depth. This segmentation allows each cut to be optimized independently, reducing micro-crack propagation and improving glass strength while maintaining process manageability.
Solution Approach 2:
The invention transitions from single-sided cutting to double-sided cutting by utilizing the third dimension (depth from opposite surfaces). By cutting from both the first surface and the second surface of the wafer, the process creates a more precise cut with reduced micro-defects, improving glass strength without excessive complexity.
2Productivity
If high power laser is used to cut through the entire wafer thickness from one side, then the cutting is complete in one pass, but larger micro-cracks and flaws are created
Solution Approach 1:
The single high-power cut is segmented into two lower-power cuts from opposite surfaces. Each laser cut only needs to penetrate partway through the wafer thickness, reducing the power required for each individual cut and minimizing micro-crack formation while maintaining complete cutting efficiency.
Solution Approach 2:
Each laser performs a partial cut rather than attempting to cut through the entire wafer thickness. The first laser cuts to a first depth from the first surface, and the second laser cuts to a second depth from the second surface, with the combined effect achieving complete separation while each individual action remains controlled and minimal.
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 results in a 20% gain in glass strength and improved drop test performance, potentially eliminating or reducing the need for post-singulation polishing, thereby enhancing the reliability and durability of optical waveguides.
Implementation Method 1
A double-sided laser cutting process is employed, where lasers cut partially into the wafer from both sides simultaneously or sequentially
Implementation Method 2
lasers cut partially into the wafer from both sides simultaneously or sequentially, reducing the power requirement and minimizing micro-cracks
Data Source
AI summary
Cutting a wafer having devices, such as glass optical waveguides, into die by cutting into both sides of the wafer to reduce or eliminate micro-cracks and defects in the die. The wafer can be cut by simultaneously cutting the wafer from both sides using separate lasers at a controlled depth. The wafer can also be sequentially cut by cutting into one side of the wafer, flipping the wafer, and then cutting into the other side of the wafer. A processor controls the power of each laser to select the depth of each cut, such that each cut may be 50% into the wafer, or other depths such as 30% for one cut and 70% for the other cut. The wafer may be cut into the bottom surface of the wafer first, and then cut into the top surface of the wafer having the optical waveguides.