Cavity Sensor Package Layout to Reduce Flare and Delamination
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Solution Overview
Problem
Current sensor packaging techniques face challenges in achieving a compact size due to increased risks of bleeding, delamination, and undesirable flare from light reflection, especially when shrinking the epoxy dam.
Innovation Solution
A sensor package design that includes a sensor die in a cavity of a circuit substrate, with a dielectric dam outside the cavity covering electrical connections and a cover layer, and an encapsulant laterally covering the dam and layer, reducing the impact on the sensing area and enabling a compact, cost-effective package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the width of the epoxy dam is shrunk to achieve a smaller package size, then the package size is reduced, but the risk of bleeding to the sensing area and delamination increases
Solution Approach 1:
The patent divides the packaging structure into distinct functional zones: the sensor die with sensing area, the epoxy dam confined to non-sensing regions, and the metal interconnects. This segmentation allows the epoxy dam to be positioned away from the sensing area, enabling package miniaturization without compromising reliability since the epoxy cannot bleed into the sensing region.
Solution Approach 2:
The patent applies different material properties and structural characteristics to different regions: the epoxy dam is configured with specific width and positioning in non-sensing areas, while the sensing area maintains its optical properties. This local differentiation allows the epoxy dam to perform its structural function without interfering with light detection, resolving the contradiction between size reduction and reliability.
2Volume of moving object
If the epoxy dam is shrunk to achieve a smaller package size, then the package size is reduced, but the risk of delamination at interfaces increases
Solution Approach 1:
The patent segments the bonding structure so that the epoxy dam is confined to specific non-sensing regions and does not extend to the sensing area. This creates distinct bonding zones with optimized interface stability, allowing the cover glass to be securely bonded without the epoxy interfering with the sensing region, thus maintaining interface stability while reducing overall package size.
Solution Approach 2:
The patent introduces metal interconnects as intermediary structures between the sensor die and external connections. These interconnects provide mechanical support and bonding surfaces, distributing stresses away from the epoxy dam interfaces and enhancing overall interface stability, which allows for reduced epoxy dam dimensions without compromising bonding reliability.
3Volume of moving object
If the epoxy dam is shrunk, then the package size is reduced, but undesirable flare caused by light reflection from the epoxy dam increases
Solution Approach 1:
The patent extracts the epoxy dam from the sensing area and confines it to non-sensing regions. By removing the epoxy material from areas where light interacts with the sensor, the source of optical flare is eliminated. The epoxy dam remains present for structural support and bonding functions but is positioned where it cannot cause harmful light reflection into the sensing pixels.
Solution Approach 2:
The patent applies optical considerations locally by ensuring the epoxy dam is positioned only in non-sensing regions where light reflection does not affect sensor performance. This local optical optimization allows the epoxy to perform its structural function while preventing flare, enabling package size reduction without optical penalties.
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 design reduces the risk of optical flare and delamination while allowing for a smaller package size and improved process reliability, with enhanced flexibility and reduced keep-out zone restrictions.
Implementation Method 1
undesirable flare caused by the reflection of the incident light from the corner of the cover glass and from the epoxy dam occurs
Implementation Method 2
The encapsulant is disposed on the first side of the circuit substrate and laterally covers the dielectric dam and the cover layer
Implementation Method 3
The electrical connection electrically connects the first side of the sensor die and the first side of the circuit substrate
Data Source
AI summary
A sensor package includes a circuit substrate, a sensor die, an electrical connection, a dielectric dam, a cover layer, and an encapsulant. The circuit substrate includes a first side, a second side opposite to the first side, and a cavity recessed from the first side toward the second side. The sensor die is disposed in the cavity and includes a first side, a sensing area on the first side, and a second side opposite to the first side and facing the circuit substrate. The electrical connection electrically connects the first sides of the sensor die and the circuit substrate. The dielectric dam is disposed on the first side of the circuit substrate and outside the cavity, and the dielectric dam partially covers the electrical connection. The encapsulant is disposed on the first side of the circuit substrate and laterally covers the dielectric dam and the cover layer.