Optical Sensor Package Epoxy Dam for Lid Gap and Contamination Control
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Solution Overview
Problem
Current semiconductor device assemblies, such as optical sensor modules, face challenges with liquid resin encapsulants that can bleed onto active areas, contaminating the sensor and tilting the glass lid due to uncontrolled thickness and shrinking dimensions, leading to increased risk of contamination and improper alignment.
Innovation Solution
A protective dam is formed using a multi-layer epoxy structure that can change phases from liquid to solid, acting as a spacer to control the gap between the optical sensor and the glass lid, preventing encapsulant bleeding and ensuring a uniform gap to maintain the lid's flatness, comprising layers that can be fully hardened through curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid resin encapsulant is used to protect components, then protection is provided, but the resin can bleed onto active areas contaminating the sensor and cause tilting of the glass lid
Solution Approach 1:
A dam structure made of photosensitive adhesive material is introduced as an intermediary barrier between the encapsulant and the sensor die. This dam prevents the encapsulant from bleeding onto the active areas while still allowing the encapsulant to provide protection. The dam is formed using photolithography and serves as a physical barrier that mediates between the protective encapsulant and the sensitive sensor components.
Solution Approach 2:
The patent uses photosensitive adhesive material that changes from liquid to solid state through photopolymerization. This parameter change allows the material to be applied in a liquid state for precise patterning, then transformed into a solid dam structure that provides mechanical support and containment. The phase change enables both the formation of precise structures and the provision of structural integrity.
2Volume of moving object
If dimensions are reduced for compact devices, then device size is reduced, but the risk of encapsulant bleeding and contamination increases
Solution Approach 1:
The dam structure is formed in advance using photolithography before the encapsulant is applied. This preliminary action creates a pre-defined barrier that prevents encapsulant bleeding, allowing the device to be miniaturized without increasing the risk of contamination. The dam is prepared as part of the substrate structure, enabling compact design while maintaining protection against encapsulant intrusion.
3Manufacturing precision
If uniform gap between sensor and glass lid is required for proper alignment, then image quality is maintained, but controlling the gap thickness becomes more difficult with shrinking dimensions
Solution Approach 1:
The photosensitive adhesive material undergoes photopolymerization, changing from liquid to solid state, which enables precise control of the gap thickness. The liquid state allows for uniform application, and the solidification process locks in the desired gap dimension. This parameter change provides a simple yet effective method for controlling gap thickness without adding complex adjustment mechanisms.
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
The solution effectively prevents contamination of the active sensor area and maintains the glass lid's alignment, ensuring the quality of images formed by the sensor while accommodating tighter dimensions and providing a stable support structure.
Implementation Method 1
The techniques described herein relate to forming a photosensitive adhesive layer on a glass substrate; patterning the photosensitive adhesive layer
Implementation Method 2
A protective dam is formed using a multi-layer epoxy structure that can change phases from liquid to solid
Data Source
AI summary
An optical sensor module includes a transparent lid spaced apart from the optical sensor die by a protective dam. The dam can be formed by photosensitive epoxy materials that can be patterned using a photolithography process. The epoxy materials can change between liquid and solid phases during assembly, and then can be fully hardened by curing. The protective dam can be formed as a single layer, or as a multi-layer stack of epoxy materials, in which the layers may have different properties. In some implementations, the epoxy dam acts as a spacer that provides a substantially uniform gap to minimize a tilt angle of the transparent lid with respect to the optical sensor.