Sealed MEMS Membrane Device for Stress Decoupling
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Solution Overview
Problem
Microelectromechanical membrane sensors, particularly pressure sensors, face challenges due to thermal stress caused by soldering, which can deform the sensor chip and induce mechanical stresses on the membrane, leading to drift in sensing accuracy. Additionally, ceramic substrates, used to mitigate these effects, are expensive and limit design freedom and compatibility with waterproofing.
Innovation Solution
A microelectromechanical device with a sealed membrane is designed, featuring a semiconductor supporting body and a suspended platform with a membrane. The platform is connected to the supporting body via a flexure, and a sealing strip with low Young's modulus and thermal expansion is used to seal the gap between the platform and the supporting body, maintaining decoupling from thermomechanical stresses while ensuring waterproofing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the membrane is formed in a suspended platform connected to the sensor chip by flexures, then thermomechanical stress on the membrane is reduced, but waterproofing becomes difficult to obtain
Solution Approach 1:
A sealing strip made of low-modulus material is introduced as an intermediary element between the platform and the sensor chip. This sealing strip fills the gap created by the suspended platform structure and provides the necessary waterproofing function without transmitting thermomechanical stresses to the membrane, thus resolving the contradiction between stress reduction and waterproofing
Solution Approach 2:
The device combines multiple materials with different properties: the flexures provide mechanical compliance for stress isolation, while the sealing strip provides waterproofing. This composite approach allows each material to optimize its function without compromising the other, solving the contradiction between stress reduction and sealing effectiveness
2Reliability
If ceramic substrates are used as bases for assembling the sensor chip and control chip, then thermal stress effects are reduced, but cost increases and design freedom is limited
Solution Approach 1:
The invention replaces expensive ceramic substrates with a more economical platform structure made from the sensor chip itself. The platform is formed by depositing and structuring material on the sensor chip, eliminating the need for separate ceramic bases while maintaining thermal stress resistance through the flexure-based decoupling mechanism
Solution Approach 2:
The sensor chip serves multiple functions: it provides the supporting body, the platform structure, and the membrane support. This multi-functionality eliminates the need for separate ceramic substrates and reduces overall device complexity, cost, and manufacturing steps while maintaining thermal performance
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
The solution effectively reduces output drift caused by thermomechanical stresses, allows for the use of less expensive bases instead of ceramic, and maintains waterproofing without compromising the sensor's accuracy, enabling flexible bonding techniques and maintaining design freedom.
Implementation Method 1
The flexures may almost completely absorb the deformations of the sensor chip, as well as any shocks and vibrations, and preserve the membrane from stresses
Implementation Method 2
A sealing strip with low Young's modulus and thermal expansion is used to seal the gap between the platform and the supporting body, maintaining decoupling from thermomechanical stresses while ensuring waterproofing
Data Source
Figure 1~3
Figure 4~7
Figure 8~10
AI summary
A microelectromechanical membrane sensor includes: a supporting body (2), containing semiconductor material and having a recess (8) in a face (2a); a platform (3), housed in the recess (8) at a distance from the supporting body (2); a flexure (7), connecting the platform (3) to the supporting body (2) and configured to keep the platform (3) suspended in the recess (8). A gap (10) extends between the supporting body (2), the platform (3) and the flexure (7). A membrane (5) is housed in the platform (3) and delimits a buried cavity (11) incorporated in the platform (3). A sealing strip (15) extends on the supporting body (2), on the platform (3) and on the flexure (7) along the gap (10).