Force Sensor Third Substrate Cover Design
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Solution Overview
Problem
Conventional force sensors face reliability issues due to repeated pressing actions degrading the package body and wire bonding structure, and are difficult to standardize for different force scales, as the stress magnitude can only be controlled by modifying the package body thickness.
Innovation Solution
A third substrate is introduced between the package body and the MEMS element to act as a cover, isolating the MEMS element from direct stress and allowing it to move correspondingly, thereby increasing reliability and enabling different force sensor specifications by modifying the thickness of the third substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the package body thickness is modified to control stress magnitude, then the force sensing range can be adjusted, but the device complexity increases and standardization becomes difficult
Solution Approach 1:
The package body is segmented into multiple functional layers: a first substrate containing circuit elements, a second substrate containing the MEMS element, and a third substrate serving as a cover. This segmentation allows independent optimization of each layer's thickness and properties, enabling force range adjustment without increasing overall device complexity.
Solution Approach 2:
The third substrate acts as an intermediary component between the pressing force source and the MEMS element. It transmits force while protecting the leads and circuit elements from direct stress exposure, allowing standardized packaging across different force sensing ranges.
2Reliability
If repeated pressing actions are applied to test durability, then the reliability can be validated, but the wire bonding structure and package body degrade
Solution Approach 1:
The leads and circuit elements are extracted from the direct path of pressing forces by placing them on the first substrate below the third substrate. This separation removes the harmful stress from the wire bonding structure, enabling repeated pressing actions without degradation.
Solution Approach 2:
The third substrate serves as a protective cushion that absorbs and distributes pressing forces before they reach the sensitive leads and circuit elements. This beforehand protection prevents stress concentration on vulnerable components during repeated pressing actions.
3Volume of moving object
If the leads are positioned close to the MEMS element for compact design, then the device size is reduced, but the leads are more susceptible to stress damage
Solution Approach 1:
The leads are positioned in a different spatial dimension (on the first substrate below the third substrate) rather than being closely coupled with the MEMS element on the second substrate. This dimensional separation maintains compact overall device volume while protecting leads from stress.
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 enhances the reliability of force sensors by protecting the MEMS element from damage and allows for standardized packaging of sensors with varying specifications using a single package process.
Implementation Method 1
a third substrate is disposed between a package body and a MEMS element to function as the cover of the MEMS element, and wherein the MEMS element is connected with the cover and generates a movement corresponding to the deformation of the cover
Data Source
AI summary
A force sensor comprises a first substrate, a second substrate, a third substrate, and a package body. The first substrate includes a fixed electrode, at least one first conductive contact, and at least one second conductive contact. The second substrate is disposed on the first substrate and electrically connected to the first conductive contact of the first substrate. The second substrate includes a micro-electro-mechanical system (MEMS) element corresponding to the fixed electrode. The third substrate is disposed on the second substrate and includes a pillar connected to the MEMS element. The package body covers the third substrate. The foregoing force sensor has better reliability.