Image Sensor Barrier Structure for Underfill Contamination
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Solution Overview
Problem
Conventional image sensor packaging is susceptible to damage and contamination from underfill adhesives and environmental particles, lacks sufficient rigidity, and has difficulties in aligning structures during manufacturing.
Innovation Solution
The implementation of a barrier structure on the package substrate and image sensor carrier, formed from materials like dry film or B-stage epoxy resin, to block underfill adhesive and particles, and the use of a thermal compression head to align the image sensor and window normal vectors during flip-chip bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill adhesive is applied during packaging, then stress redistribution and thermal aging improvement are achieved, but contamination and damage to image pixel arrays occur
Solution Approach 1:
The package substrate is divided into distinct functional zones: a first region containing the image sensor die and discrete mounts, and a second region containing the window. A barrier structure separates these regions, preventing underfill adhesive from the first region from contaminating the image sensor die while allowing the underfill to perform its stress redistribution function in the mounting area.
Solution Approach 2:
A barrier structure acts as an intermediary element between the underfill adhesive and the image sensor die. This barrier prevents direct contact between the adhesive and the sensitive image pixel arrays, thereby eliminating contamination while allowing the underfill to remain in place for stress management.
2Ease of manufacture
If discrete mounts are used for flip-chip bonding, then electrical connection and mounting are achieved, but susceptibility to adhesive contamination and particle damage increases
Solution Approach 1:
The package substrate is segmented into a first region for mounting operations and a second region for the window, separated by a barrier structure. This segmentation creates a protected environment for the image sensor die during the flip-chip bonding process, allowing discrete mounts to be used for electrical connection while preventing particle contamination.
3Ease of operation
If conventional packaging structure is used, then basic mounting function is achieved, but sufficient rigidity for certain operating conditions is lacking
Solution Approach 1:
The package substrate is formed as a composite structure combining a first region with discrete mounts for electrical connection and a second region with a window for light transmission. The barrier structure integrated into this composite design provides both structural rigidity for operating conditions and functional separation for contamination prevention.
4Manufacturing precision
If alignment adjustment is attempted during manufacture, then positioning accuracy may be improved, but manufacturing complexity increases
Solution Approach 1:
The barrier structure is formed on the package substrate before the image sensor die is mounted. This preliminary formation of the barrier defines the boundaries of the first and second regions in advance, establishing precise alignment references that guide subsequent mounting operations without requiring complex alignment adjustment mechanisms during assembly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents contamination and damage from underfill adhesive and environmental particles, enhances the structural integrity of the image sensor package, and facilitates precise alignment of the image sensor and window normal vectors, improving the yield and operational capabilities of packaged image sensors.
Implementation Method 1
use of a thermal compression head to align the image sensor and window normal vectors during flip-chip bonding
Data Source
AI summary
An image sensor package including a barrier structure to prevent image sensor die contamination is described. A barrier structure may surround an image sensor die that is attached on an image sensor carrier. The barrier structure may be attached to a transparent window structure as well as a package substrate. The barrier structure may extend through a hole in the package substrate. The image sensor carrier may be mounted to the package substrate using a thermal compression head that is able to apply independently varying compressive forces to corresponding regions of a surface at a given time. The thermal compression head may be used to cure the barrier structure and/or adhesives used in the image sensor package. Underfill adhesive may be deposited between discrete mounting structures used to mount the package substrate to the image sensor carrier, after the barrier structure has been applied.