Image Sensor Package Structure With Pre-Formed Dams and Reduced KOZ
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Solution Overview
Problem
Prior image sensor packages are susceptible to environmental factors such as moisture penetration and edge flare, leading to performance degradation, and have a large non-optically active area (KOZ) that limits die size and production yield.
Innovation Solution
The use of chip-scale packaging with pre-formed attachment dams, through-vias, and encapsulants to secure a protective cover, reducing the KOZ and preventing tilt, while eliminating wire bonds and enhancing edge protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective cover is attached to the semiconductor die using conventional methods, then the die is protected from environmental factors, but the non-optically active area (KOZ) increases, reducing the number of dies that can be produced on a wafer
Solution Approach 1:
The patent applies preliminary action by pre-forming attachment dams on the semiconductor die before die attachment. These dams are created through a series of steps including forming a first layer of material, patterning it, forming a second layer, and planarizing. This pre-formed structure enables precise control of the attachment area, reducing the KOZ while ensuring reliable protective cover attachment and environmental protection.
2Reliability
If the protective cover is attached with a large KOZ to ensure proper attachment, then attachment reliability is improved, but the overall die size increases, reducing production yield
Solution Approach 1:
The patent applies preliminary action by pre-forming attachment dams on the semiconductor die before die attachment. These dams are created through a series of steps including forming a first layer of material, patterning it, forming a second layer, and planarizing. This pre-formed structure enables precise control of the attachment area, reducing the KOZ while ensuring reliable protective cover attachment and environmental protection.
Solution Approach 2:
The patent utilizes planarization through chemical mechanical polishing (CMP), which involves hydraulic and mechanical processes to achieve a flat surface. This planarization step ensures that the attachment dams provide a uniform attachment surface, improving attachment reliability while maintaining a compact die size for higher production yield.
3Device complexity
If conventional packaging is used, then the structure is simple, but the package is susceptible to edge flare and tilt of the protective cover
Solution Approach 1:
The patent applies segmentation by dividing the attachment structure into multiple distinct layers and components: a first layer of material forming the attachment dam, a second layer of material, and an optional third layer. This segmented approach allows each layer to perform a specific function, with the combined structure providing both mechanical support and precise geometric control to prevent cover tilt and edge flare while maintaining reasonable structural simplicity.
Solution Approach 2:
The patent applies local quality by creating attachment dams with specific geometric characteristics at the attachment region. The dams have controlled height, width, and shape (including tapered or angled sides) that are optimized for preventing cover tilt and edge flare. This localized structural enhancement provides the necessary mechanical constraints only where needed, without complicating the entire package structure.
Data Source
AI summary
In a general aspect, a semiconductor package includes a semiconductor die having an image sensor disposed on a first surface. The package further includes a signal redistribution layer disposed on a second surface of the semiconductor die that is opposite the first surface. The package also includes at least one via extending through the semiconductor die from the first surface to the second surface, where a via of the at least one via electrically connects a signal trace on the first surface of the semiconductor die with the signal redistribution layer. The package also includes a glass cover coupled with a portion of the first surface of the semiconductor die via an attachment dam. The portion of the first surface excluding the image sensor, and the attachment dam and the glass cover define a sidewall that is orthogonal to the first surface of the semiconductor die.