Image Sensor Chip Scale Package Dam Combination Design
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Solution Overview
Problem
Conventional image sensor packages face challenges in microminiaturization due to large substrate footprints, contamination during dam formation, and inadequate adhesive areas, leading to poor sensing performance and reliability issues.
Innovation Solution
A chip scale package with a dam combination comprising a first and second dam part, where the horizontal spacing from the dam peripheries to the image sensing area is less than 200 μm, and a transparent lid is used to airtight seal the image sensing window, ensuring adequate adhesive area and minimizing photoresist residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the dam opening is enlarged to reduce the substrate footprint, then the package size is reduced, but the transparent lid becomes easily detached due to less adhesive area
Solution Approach 1:
The dam structure is segmented into multiple parts (first dam part and second dam part) that are disposed at different locations. The first dam part is disposed on the active surface of the image sensor chip, while the second dam part is disposed on the lid, allowing the dam opening to be enlarged for reduced footprint while maintaining sufficient adhesive area through the distributed dam structure.
Solution Approach 2:
The dam structure transitions from a conventional single-layer configuration to a multi-dimensional arrangement where the first dam part is on the chip surface and the second dam part is on the lid surface. This spatial distribution in multiple dimensions enables both enlarged opening and sufficient adhesion area.
2Reliability
If the dam thickness is increased to improve package reliability, then the horizontal spacing requirement increases to greater than 200 μm, but this prevents further microminiaturization of the image sensor chip
Solution Approach 1:
The dam is divided into first and second dam parts disposed at different locations and orientations. This segmentation allows the horizontal spacing to be reduced to 200 μm or less while maintaining reliability through the distributed structural support of multiple dam parts rather than relying on a single thick dam.
Solution Approach 2:
The dam structure utilizes three-dimensional spatial distribution with the first dam part on the chip and the second dam part on the lid, enabling reduced horizontal spacing while maintaining reliability through vertical and spatial distribution of the dam function.
3Reliability
If the dam opening is reduced to improve sensing performance, then photoresist residues are disposed on the corners and peripheries, but this leads to poor sensing performance
Solution Approach 1:
The dam structure is segmented into multiple parts with the first dam part having a first opening and the second dam part having a second opening. This segmentation allows optimization of the opening size to minimize photoresist residues while maintaining sufficient sensing area, as the distributed structure reduces the concentration of residues in critical sensing regions.
Data Source
AI summary
Disclosed is a chip scale package of image sensor having a dam combination, comprising an image sensor chip, a dam combination, a transparent lid disposed on the dam combination, and a plurality of external terminals disposed on the backside of the chip. An image sensing area is formed on the active surface of the image sensor chip. A dam combination consists essentially of at least two dam parts and has an image sensing window. The peripheries of the image sensor window are formed by a pre-formed dam part and are adjacent to the image sensing area with horizontal spacing not greater than 200 μm. There is a combination interface between the two dam parts. The combination interface and the post-formed dam part are far away from the image sensing area than the pre-formed dam part to keep residues caused by the disposition of the pre-formed dam part to be away from the 200 μm exclusive region around the image sensing area.