Force Sensor Gap-Controlled Over-Force Protection
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Solution Overview
Problem
Force sensors with mechanical deflection limiters are needed to protect microelectronic sensors from excessive deformation and breakage, especially in environments where high external forces are unpredictable and could exceed the sensor's operational limits.
Innovation Solution
A force sensor design featuring a flip-chip mounted force-sensing die with a flexible diaphragm and a predetermined gap between the die and the mounting substrate, which includes a mechanical stop to limit deflection and prevent deformation beyond a breaking point, ensuring precise and reliable measurements even under high external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the force sensor is designed to be highly sensitive for precise measurements, then measurement precision is improved, but the sensor becomes vulnerable to damage from excessive forces
Solution Approach 1:
A mechanical stop is integrated into the force sensor structure to physically limit the deflection of the flexible diaphragm before excessive force can damage the sensor. This predetermined mechanical barrier cushions the sensor against over-force events, allowing the use of highly sensitive sensing elements without compromising reliability.
2Reliability
If a mechanical deflection limiter is added to protect the sensor, then sensor durability is improved, but the device complexity increases
Solution Approach 1:
The mechanical stop is integrated directly into the substrate structure, merging the protective function with the mounting structure. This eliminates the need for separate protective components and reduces overall device complexity while maintaining sensor durability.
Solution Approach 2:
The mechanical stop structure automatically limits diaphragm deflection through its predetermined geometry, requiring no external control systems or additional components. The structure serves its own protective function, simplifying the overall device design.
3Volume of moving object
If the gap between the force-sensing die and mounting substrate is reduced for compact packaging, then device size is reduced, but the deflection limitation capability is compromised
Solution Approach 1:
The substrate is designed with a localized mechanical stop feature at the specific location where deflection limitation is needed, while maintaining a compact overall gap structure. This allows precise control of diaphragm deflection at the sensing region without requiring a large overall device volume.
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 enables force sensors to operate reliably and accurately over a long period, preventing damage from excessive forces and allowing for precise low-force measurements, while also enabling compact packaging for use in small spaces, thus reducing replacement costs and enhancing performance in applications like medical devices.
Implementation Method 1
an unflipped back surface being thinned so as to create a flexible diaphragm responsive to an externally applied force
Implementation Method 2
a predetermined space remains between the top surface of the force-sensing die and the mounting substrate it faces, the substrate presenting a deflection limitation for the deformation of the flexible membrane during a force event
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2B
AI summary
Apparatus and associated methods relate to a force sensor having flip-chip mounted force-sensing die having a force-sensing element fabricated on an unflipped top surface and an unflipped back surface being thinned so as to create a flexible diaphragm responsive to an externally applied force, wherein, when the force-sensing die is flipped and mounted, a predetermined space remains between the top surface of the force-sensing die and the mounting substrate it faces, the substrate presenting a deflection limitation for the deformation of the flexible membrane during a force event. In an illustrative embodiment, the force sensor may have a mechanical stop to precisely establish a predetermined deflection limitation. In some embodiments, the predetermined deflection limitation may advantageously limit the deflection of the flexible membrane so as not to deflect beyond a breaking point.