Thin Wedge Actuation for Miniaturized Force Sensors
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Solution Overview
Problem
Conventional force sensors face challenges in miniaturization for smaller packaging applications, as the actuation element can encroach on wire bonds, leading to potential shortages and increased manufacturing complexity, and the use of a spherical ball bearing requires higher precision and costs.
Innovation Solution
The use of a thin wedge/plate actuation element with rounded edges, which provides focalized force contact and allows for closer placement of sense elements, reducing the size of the sense die and eliminating the need for an etched diaphragm, while maintaining high sensitivity and overload protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a spherical ball bearing actuation element is used, then the force sensor can maintain structural integrity, but the sensor size increases and manufacturing precision requirements increase
Solution Approach 1:
The patent uses a spherical ball bearing actuation element that contacts the sense die at a single point. The spherical geometry concentrates the applied force onto a small contact area, maintaining structural integrity while enabling compact design. The curved surface of the ball bearing distributes stress evenly during compression, preventing damage to wire bonds and other sensitive components.
2Volume of moving object
If the actuation element is reduced in size for miniaturization, then the sensor packaging size decreases, but the actuation element may contact wire bonds causing shortages
Solution Approach 1:
The patent positions the spherical ball bearing actuation element and sense elements in specific locations on the sense die. The ball bearing is placed at a location where it contacts the diaphragm at a single point, away from wire bond trajectories. This local optimization of component placement ensures miniaturization is achieved without compromising reliability, as the concentrated force application point is strategically positioned to avoid sensitive areas.
3Ease of manufacture
If conventional actuation elements are used, then the force sensor can be manufactured with standard processes, but the sense die size increases reducing sensitivity
Solution Approach 1:
The spherical ball bearing actuation element enables a compact force sensor design by concentrating the applied force onto a single point on the sense die. This spherical geometry allows the sense die to be smaller while maintaining adequate sensing area, as the force is applied at a focused contact point rather than being distributed across a larger area. The standard spherical shape also facilitates manufacturing using conventional processes.
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 configuration enables smaller, cost-effective force sensors with increased die sensitivities and reduced manufacturing costs, while preventing wire bond contact and enhancing precision and accuracy in force measurements.
Implementation Method 1
The actuation element may comprise a rounded edge that provides focalized force contact
Implementation Method 2
force sensors may be used to sense the force applied to the sensors and provide an output signal representative of the applied force
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2C
AI summary
Embodiments generally relate to device and methods for detecting force. A force sensor may comprise a sense die, a substrate, one or more sense elements supported by the sense die, one or more electrical contacts located on the sense die and electrically coupled to electrical traces on the substrate, and an actuation element configured to transmit a force to the sense die. The width of the actuation element may be less than the distance between the one or more electrical contacts. In some embodiments, the actuation element may comprise a thin wedge/plate configured to interact with the sense die at a contact point. The thin wedge/plate may allow use of a smaller sense die and/or may allow closer placement of the one or more sense elements to the contact point and/or may prevent accidental contact with the one or more electrical contacts which may lead to a short circuit.