Pressure Sensor Membrane Decoupling via Suspension Elements
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Solution Overview
Problem
Pressure sensors are sensitive to mechanical stress during mounting, which can be transmitted to the deformable membrane, affecting accuracy due to direct attachment to a carrier and stress-induced mechanical coupling.
Innovation Solution
A pressure sensor design featuring a deformable membrane mechanically decoupled from the substrate and cap, with a container suspended by suspension elements, allowing for orthogonal deflection and reducing stress propagation, using a cap with a cavity and a deformable membrane integrated into the cap, and a porous protection membrane to prevent particle interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure sensor is mounted with back side to a carrier and electrically connected thereto, then electrical connection and mechanical support are achieved, but mechanical stress is transmitted via solder balls to the first substrate and specifically to stress sensitive structures such as the membrane
Solution Approach 1:
The pressure sensor is divided into functionally independent modules: the first substrate with processing circuitry, the cap with container and holder, and the deformable membrane. This segmentation allows the membrane to be mechanically decoupled from the substrate, preventing stress transmission while maintaining electrical connectivity through separate pathways.
Solution Approach 2:
The cap acts as an intermediary structure between the first substrate and the deformable membrane. The holder within the cap provides mechanical support and electrical connection points, while the suspension elements provide controlled mechanical coupling. This intermediary structure prevents direct stress transmission from the substrate to the membrane.
2Strength
If the deformable membrane is directly attached to the first substrate, then structural support is provided, but stress induced from external carrier or during mounting is transmitted to the membrane affecting accuracy
Solution Approach 1:
The cap and holder serve as intermediary structures that provide mechanical support to the deformable membrane without creating direct rigid attachment to the first substrate. The suspension elements provide controlled mechanical coupling that supports the membrane while allowing it to deflect freely in response to pressure changes without transmitting mounting stresses.
Solution Approach 2:
The mechanical support function is separated from the electrical connection function. The holder provides mechanical support and electrical connection points, while the suspension elements provide controlled mechanical coupling. This segmentation allows the membrane to be supported without direct rigid attachment to the substrate, preventing stress transmission.
3Stability of the object's composition
If the membrane is mechanically coupled to the cap portion mounted to the first substrate, then structural stability is achieved, but stress propagation from the substrate to the membrane occurs
Solution Approach 1:
The suspension elements provide localized mechanical coupling with specific properties: they are rigid enough to provide structural stability and electrical connection, but flexible enough to allow membrane deflection and block stress propagation. This local quality differentiation within the mechanical coupling structure resolves the contradiction between stability and stress isolation.
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
Significantly reduces stress-induced errors by decoupling the membrane from the substrate and cap, enhancing accuracy and durability while maintaining sensitivity to pressure changes.
Implementation Method 1
a deformable membrane (412) providing a separation between a cavity (411) with in the case of an absolute pressure sensor an essentially constant pressure and a port open to the outside of the sensor
Implementation Method 2
The container is suspended from the holder by means of one or more suspension elements... the deformable membrane is mechanically decoupled from the first substrate
Implementation Method 3
A recess (44) in the cap (4) is provided for covering by a protection membrane (8)
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3d
AI summary
A pressure sensor comprises a first substrate (1) containing a processing circuit integrated thereon and a cap (4) attached to the first substrate (1). The cap (4) includes a container (41), a holder (42), and one or more suspension elements (45) for suspending the container (41) from the holder (42). The container (41) includes a cavity (411) and a deformable membrane (412) separating the cavity (411) and a port open to an outside of the pressure sensor. The container (41) is suspended from the holder (42) such that the deformable membrane (412) faces the first substrate (1) and such that a gap (6) is provided between the deformable membrane (412) and the first substrate (1) which gap (6) contributes to the port. Sensing means (116) are provided for converting a response of the deformable membrane (412) to pressure at the port into a signal capable of being processed by the processing circuit.