Multi-Step Image Sensor Package for Pre-Seal Testing and Rework
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Solution Overview
Problem
Conventional image sensor packages face yield limitations due to defect density, particularly for large dies, and lack a rework solution after the cover glass is sealed, making them sensitive to environmental cleanliness.
Innovation Solution
The image sensor package features a multi-step cavity on a substrate with an image sensor bonded to the bottom, where a cover glass is sealed over a raised-step structure, allowing for pre-sealing verification through image/electrical tests and enabling a rework process if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sealing method is used with a planar sealing interface, then the manufacturing process is simple, but the yield is limited by defect density and no rework is possible after sealing
Solution Approach 1:
The cavity is divided into multiple levels with different heights, creating a multi-step structure. The first cavity portion has a first height and the second cavity portion has a second height different from the first, allowing the cover glass to be positioned at a specific elevation before final sealing. This segmentation enables intermediate testing while maintaining structural integrity.
Solution Approach 2:
The cover glass is placed on the raised step structure before final sealing to allow preliminary image and electrical tests to be performed. This preliminary action enables defect detection and rework opportunities before the package is permanently sealed, improving yield without compromising the final sealed structure.
2Reliability
If the cover glass is sealed immediately without testing, then the manufacturing process is efficient, but defects cannot be detected and rework is impossible
Solution Approach 1:
The multi-step cavity structure enables preliminary testing of image sensors and electrical connections before final sealing. The cover glass is positioned on the raised step at an intermediate stage, allowing time for defect detection and validation without extending the overall manufacturing cycle significantly.
Solution Approach 2:
The raised step structure acts as an intermediary platform that temporarily supports the cover glass during testing. This intermediary structure allows for non-destructive testing and potential rework while maintaining the integrity of the sealed package structure.
3Reliability
If adhesive is applied extensively for sealing, then the sealing is robust, but excessive glue spillage occurs
Solution Approach 1:
The raised step structure creates a localized sealing region where adhesive is applied only at the interface between the cover glass and the raised step. This local quality approach ensures robust sealing at the critical interface while preventing adhesive from spreading to unwanted areas, eliminating excessive glue spillage.
Data Source
AI summary
An image sensor package with a multi-step cavity formed in or on a substrate, which includes an image sensor bonded onto bottom of the multi-step cavity, and a cover glass placed and sealed on a lower portion of the multi-step cavity. Lower portion of the multi-step cavity includes at least a first and a second raised-step structures protruding from the bottom of the multi-step cavity, and the cover glass is placed and sealed over the first raised-step structure.