Semiconductor Sensor Underfill and Segmented Encapsulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fingerprint sensors face challenges in protecting the fingerprint detection region from physical and electrical impacts while maintaining detection sensitivity, as thick encapsulation resins can decrease sensitivity and manufacturing errors lead to variations in sensor properties.
Innovation Solution
A semiconductor device with a thin insulation layer covering the sensor element, an underfill between the sensor element and the substrate, and an encapsulation resin filling gaps between substrates, which protects the sensor element and maintains sensitivity by limiting variations in thickness and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick encapsulation resin is used to protect the sensor element, then the sensor element is protected from physical and electrical impacts, but the detection sensitivity decreases
Solution Approach 1:
The encapsulation structure is divided into two distinct parts: a thin first encapsulation resin layer that directly covers the sensor element to maintain sensitivity, and a second encapsulation resin layer that provides additional protection. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the encapsulation structure have different thicknesses and material properties. The first encapsulation resin layer is made thin locally where it contacts the sensor element to preserve detection sensitivity, while the overall encapsulation structure provides sufficient protection through the combination of layers and underfill material.
2Measurement precision
If the encapsulation resin is made thin to maintain detection sensitivity, then the detection sensitivity is maintained, but the sensor element becomes vulnerable to physical and electrical impacts
Solution Approach 1:
The encapsulation structure is divided into two distinct parts: a thin first encapsulation resin layer that directly covers the sensor element to maintain sensitivity, and a second encapsulation resin layer that provides additional protection. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
The underfill material acts as an intermediary substance filled in the gap between the sensor element and the substrate. It provides mechanical support and protection to the sensor element without requiring a thick encapsulation resin layer, thus maintaining detection sensitivity while enhancing reliability.
3Reliability
If wire bonding is used to connect the sensor element, then electrical connection is achieved, but the encapsulation resin must be thick enough to cover the bonding wires, decreasing detection sensitivity
Solution Approach 1:
Instead of connecting the sensor element to the substrate and then encapsulating it (which requires thick resin to cover wires), the invention inverts the sequence by first forming the thin encapsulation resin layer over the sensor element, then connecting to the substrate through this thin layer. This allows wire bonding or flip-chip connection without requiring thick encapsulation.
4Measurement precision
If no encapsulation resin is used to maintain sensitivity, then detection sensitivity is maximized, but the sensor element is exposed to physical and electrical impacts
Solution Approach 1:
Different regions of the encapsulation structure have different thicknesses and material properties. The first encapsulation resin layer is made thin locally where it contacts the sensor element to preserve detection sensitivity, while the overall encapsulation structure provides sufficient protection through the combination of layers and underfill material.
Solution Approach 2:
The underfill material acts as an intermediary substance filled in the gap between the sensor element and the substrate. It provides mechanical support and protection to the sensor element without requiring a thick encapsulation resin layer, thus maintaining detection sensitivity while enhancing reliability.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A semiconductor device (20;20A) includes an insulation layer (31), a wiring pattern (32) formed on a lower surface (31 B) of the insulation layer (31), and a sensor element (40) flip-chip-connected to the wiring pattern (32). The sensor element (40) includes an active surface (40A), including a sensor portion (41) adapted to perform fingerprint recognition, detection of a touching operation, or recognition of biometric information of a user, and a rear surface (40B), located at a side opposite to the active surface (40A). An encapsulation resin (70) fills a gap between the lower surface (31 B) of the insulation layer (31) and an upper surface of a wiring substrate (60), facing the rear surface (40B) of the sensor element (40) and connected to the wiring pattern (32) by a connecting member (50). The entire active surface (40A) of the sensor element (40) is covered by underfill (45) formed between the active surface (40A) of the sensor element (40) and the lower surface (31 B) of the insulation layer (31). The insulation layer (31) includes an upper surface (31A), defining an uppermost surface and free from a wiring layer.