Dynamic Digital Fringe Projection Techniques For Measuring Warpage
AssigneeGeorgia Tech Research Corporation
InventorsIfeanyi Charles Ume, Sungbum Kang
Life of this patent
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Abstract
Dynamic digital fringe projection (DDFP) techniques for measuring warpage. The DDFP technique generates a dynamic fringe pattern, in which a proper fringe intensity distribution is dynamically determined based on the surface reflectance of an unpainted sample in order to obtain better fringe image contrasts. The DDFP technique includes the automatic segmentation method to segment the chip package and PWB regions in an unpainted PWB assembly PWBA image. It also includes calibration methods to compensate the mismatches in coordinates and intensities between the projected and captured images.
Claims20
A method of measuring warpage of a sample having a first region of a first surface reflectance and a second region of a second surface reflectance comprising:
- projecting a dynamic fringe pattern onto the first and second regions, wherein the dynamic fringe pattern comprises an intensity distribution based upon the first surface reflectance and the second surface reflectance;
- capturing phase-shifted fringe images of the dynamic fringe pattern reflected from the first and second regions of the sample;
- generating a wrapped-phase image from the phase-shifted fringe images;
- unwrapping the wrapped-phase image to obtain an unwrapped-phase image;
- and
- converting the unwrapped-phase image into a displacement image indicative of warpage of the first region and the second region of the sample.
The method of claim 15 further comprising:
- segmenting the sample into the first region and the second region prior to projecting the dynamic fringe pattern.
A method of measuring warpage of at least a portion of a PWBA having a first region of a first surface reflectance and a second region of a second surface reflectance comprising:
- projecting a dynamic fringe pattern onto the first and second regions, wherein the dynamic fringe pattern comprises an intensity distribution based upon the first surface reflectance and the second surface reflectance, the dynamic fringe pattern containing sinusoidal fringes with different intensity distributions for each of the regions;
- capturing phase-shifted fringe images of at least a portion of the dynamic fringe pattern reflected from the first and second regions of at least a portion of the PWBA;
- generating a wrapped-phase image from the phase-shifted fringe images;
- unwrapping the wrapped-phase image to obtain an unwrapped-phase image;
- and
- converting the unwrapped-phase image into a displacement image indicative of warpage of the first region and the second region of at least a portion of the PWBA.
A method of measuring warpage of a sample having a first region of a first surface reflectance and a second region of a second surface reflectance comprising:
- segmenting the sample into the first region and the second region;
- generating a dynamic projected image from a dynamic fringe pattern, the dynamic fringe pattern comprising sinusoidal fringes with different intensity distributions for each of the regions;
- projecting the dynamic projected image onto the first and second regions, wherein the dynamic projected image comprises an intensity distribution based upon the first surface reflectance and the second surface reflectance;
- capturing phase-shifted images of the dynamic projected image reflected from the first and second regions of the sample;
- generating a wrapped-phase image from the phase-shifted images;
- unwrapping the wrapped-phase image to obtain an unwrapped-phase image;
- and
- converting the unwrapped-phase image into a displacement image evidencing warpage of the first region and the second region of the sample.
Dependencies are inferred from the claim text.