Flip-Chip Sensor Dam Structure for Underfill Protection
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Solution Overview
Problem
Existing sensor assembly manufacturing processes face challenges in preventing underfill material from covering the sensing area during flip-chip mounting, which requires precise alignment and can complicate the manufacturing process, especially in cost-sensitive applications like consumer electronics.
Innovation Solution
A sensor assembly design featuring a dam structure between the sensor chip and substrate, where the dam is formed from a photoresist material and extends between the sensor chip and substrate, preventing underfill from entering the sensing area by creating a chamber that communicates with the environment through a controlled opening, allowing for conventional flip-chip mounting and underfill application without obstructing the sensing area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dam structure is added to prevent underfill from covering the sensing area, then the sensing area is protected from underfill contamination, but the device complexity increases due to additional alignment requirements
Solution Approach 1:
The dam structure is formed on the substrate before the sensor chip is mounted. This preliminary formation of the dam eliminates the need for complex alignment during the chip mounting process, as the dam is already in its final position and configuration. The pre-formed dam structure guides the underfill application and prevents contamination of the sensing area without requiring precise real-time alignment.
2Productivity
If conventional flip-chip mounting is used, then manufacturing efficiency is maintained, but underfill may cover the sensing area causing contamination
Solution Approach 1:
The dam structure acts as an intermediary element between the substrate and the sensor chip. It serves as a physical barrier that intercepts the underfill material before it can reach the sensing area, while still allowing the conventional flip-chip mounting process to proceed without modification. The dam structure mediates between the need for efficient manufacturing and the need to prevent contamination.
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
This design simplifies the manufacturing process by maintaining the sensing area's accessibility and compatibility with conventional underfilling techniques, ensuring effective prevention of underfill and solder flux from reaching the sensing area, thus reducing manufacturing complexity and costs.
Implementation Method 1
the dam is formed from a photoresist material
Implementation Method 2
the liquid is then drawn into the gap using capillary forces
Data Source
Figure 1~9
Figure 3~5
Figure 6~8
AI summary
The sensor assembly comprises a substrate (1), such as a flexible printed circuit board, and a sensor chip (2) flip-chip mounted to the substrate (1), with a first side (3) of the sensor chip (2) facing the substrate (1). A sensing area (4) and contact pads (5) are integrated on the first side (3) of the sensor chip (2) and located in a chamber (17) between the substrate (1) and the sensor chip (2). Chamber (17) is bordered along at least two sides by a dam (16). Underfill (18) and/or solder flux is arranged between the sensor chip (2) and the substrate (1), and the dam (16) prevents the underfill from entering the chamber (17). An opening (19) extends from the chamber to the environment and is located between the substrate (1) and the sensor chip (2) or extends through the sensor chip (2).