Non-planar Image Sensor Packaging Reducing Optical Cross-talk
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Solution Overview
Problem
Conventional planar packaging of image sensors leads to optical cross-talk due to the distance between color filters and pixels, resulting in signal loss and reduced modulation transfer function, which complicates design and testing while imposing constraints on pixel scaling and increasing costs.
Innovation Solution
A non-planar frame base is used for image sensors, where the image sensor die is thinned and bonded into a concave or convex depression, aligning chief rays perpendicular to the image sensor surface, reducing optical cross-talk and simplifying testing and design by eliminating the need for complex lens shifts and probe card modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional planar CMOS packaging is used, then manufacturing simplicity is maintained, but optical cross-talk increases due to distance between color filters and pixels
Solution Approach 1:
The patent applies curvature by bonding the image sensor die to a non-planar frame base with a concave depression, causing the die to assume a curved configuration. This curvature positions the color filters closer to the pixel array, reducing optical cross-talk while maintaining manufacturing simplicity through conventional bonding processes.
Solution Approach 2:
The patent transitions from a planar two-dimensional packaging structure to a three-dimensional curved structure by bonding the die to a non-planar frame base. This dimensional change allows color filters to be positioned closer to pixels in the vertical dimension while maintaining lateral alignment, thereby reducing optical cross-talk.
2Manufacturing precision
If color filters are positioned closer to pixels to reduce optical cross-talk, then optical resolution improves, but pixel aspect ratio constraints increase
Solution Approach 1:
The curved configuration of the image sensor die bonded to the non-planar frame base allows color filters to be positioned closer to the pixel array without imposing strict aspect ratio constraints on the pixels. The curvature naturally accommodates the spatial relationship between filters and pixels, enabling improved optical resolution while maintaining design flexibility.
3Manufacturing precision
If color filters are offset towards the center to mitigate optical cross-talk, then optical performance improves, but design and layout complexity increases
Solution Approach 1:
The patent eliminates the need for offsetting color filters towards the center by using a curved die configuration. The curvature positions all color filters uniformly closer to their corresponding pixels across the entire sensor array, improving optical performance while maintaining regular, simple layout patterns without complex offsets.
4Ease of operation
If planar packaging is used, then testing with standard probe cards is simple, but optical cross-talk degrades measurement accuracy
Solution Approach 1:
The curved configuration of the image sensor die bonded to the non-planar frame base reduces optical cross-talk, thereby improving the accuracy of optical measurements and characterizations. This allows standard probe cards to be used with improved measurement precision, as the reduced cross-talk minimizes interference during testing.
Data Source
AI summary
A non-planar frame base for an image sensor.