Grating-Based In-Plane Strain Measurement Using Laser Scanning
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Solution Overview
Problem
Current strain sensing techniques face challenges in achieving high strain sensitivity, high spatial resolution, and a large field of view for mapping in-plane strain distribution across electronic device substrates, particularly due to mismatched coefficients of thermal expansion among materials, which affects the reliability and performance of electronic products.
Innovation Solution
A method involving the formation of a grating on a substrate surface with a wavelength of 750 nm to 850 nm, which is scanned with a small laser beam to detect strain through diffraction angle variations, allowing for high-resolution strain mapping with a small laser spot size and amplification of nanoscale changes into measurable diffraction peak shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro Moiré technique is used for strain sensing, then strain sensitivity is improved, but spatial resolution deteriorates due to large illuminated area requirement
Solution Approach 1:
The patent segments the measurement process by using a scanning approach with a small laser spot that systematically scans across the grating. This divides the large measurement area into small sequential measurement points, allowing high spatial resolution at each point while maintaining the ability to cover large areas, thus resolving the contradiction between strain sensitivity and spatial resolution
Solution Approach 2:
The patent transitions from a static full-field measurement approach to a dynamic scanning approach by adding the time dimension. The laser scans across the grating point by point, transforming the measurement from a spatial problem to a spatio-temporal process, enabling both high spatial resolution and large field of view coverage
2Manufacturing precision
If DIC technique is used for strain sensing, then spatial resolution is improved, but field of view deteriorates due to large optical magnification requirement
Solution Approach 1:
The patent employs a dynamic scanning mechanism where the laser spot moves across the grating surface in a systematic pattern. This dynamic approach allows the system to maintain high spatial resolution at each measurement point while progressively covering a large field of view, eliminating the need for large optical magnification and enabling both high spatial resolution and large area coverage
Solution Approach 2:
The measurement area is segmented into small discrete points that are measured sequentially by the scanning laser. This segmentation allows the system to achieve high spatial resolution at each point while the cumulative effect of scanning across many points provides comprehensive coverage of large areas, resolving the field of view limitation
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 high sensitivity and spatial resolution strain mapping, effectively identifying potential failure locations in electronic packages by capturing strain distributions across large areas with improved accuracy and reliability.
Implementation Method 1
A laser is then focused onto the grating to determine the strain on the surface by determining the variation of the grating wavelength due to the strain on the surface... The induced strain is related to the grating wavelength variation, which leads to the diffraction angle variation that is captured by the strain sensing measurements.
Data Source
AI summary
Methods for measuring and/or mapping in-plane strain of a surface of a substrate. A grating is formed on at least a portion of the surface of the substrate. A laser is then used focused onto the grating to determine the strain on the surface by determining the variation of the grating wavelength due to the strain on the surface. The strain information is essentially carried by the grating, in terms of grating wavelength, because it varies according to the volume change of the underlying substrates. By scanning the surface grating with the small laser size, a high resolution strain map of the surface can be produced. The induced strain is related to the grating wavelength variation, which leads to the diffraction angle variation that is captured by the strain sensing measurements.