Dual Diaphragm Pressure Sensor Chip for Accurate Differential Measurement
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Solution Overview
Problem
Existing differential pressure sensors are prone to errors due to warpage, solidification, or changes in elastic modulus caused by temperature changes or moisture absorption, which affect the capacitance values and result in inaccuracies in detected differential pressures.
Innovation Solution
A pressure sensor chip design that includes a first and second insulating layer with cavities, a first and second conductive layer with diaphragms, and flow paths that allow communication between the cavities to cancel out stress-induced errors, thereby improving the accuracy of differential pressure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a differential pressure sensor uses a single conductive layer with two diaphragms, then the device complexity is reduced, but measurement precision deteriorates due to stress-induced errors from temperature changes and moisture absorption
Solution Approach 1:
The single conductive layer is divided into two separate conductive layers, each with its own diaphragm. This segmentation allows independent measurement of capacitance changes for each diaphragm, enabling error cancellation through differential calculation while maintaining manageable device complexity
Solution Approach 2:
Two insulating layers are introduced as intermediary elements between the conductive layers and external environment. These insulating layers protect the conductive layers from direct exposure to temperature and moisture variations, reducing stress-induced errors while maintaining device functionality
2Productivity
If the pressure sensor undergoes rapid temperature changes or reflow processes during manufacturing and mounting, then productivity is improved, but reliability deteriorates due to warpage and solidification of materials
Solution Approach 1:
The sensor structure is designed with inherent stress compensation capabilities before deployment. The dual-diaphragm configuration with flow paths allows pre-establishment of balanced stress states, cushioning against thermal shock and reflow process effects that occur during manufacturing and mounting
Solution Approach 2:
The sensor utilizes changes in capacitance parameters in response to pressure differentials while maintaining structural parameters that resist thermal warpage. The electrical measurement parameters are designed to be insensitive to mechanical stress caused by temperature variations
3Device complexity
If moisture absorption occurs in the sensor material, then the device complexity remains unchanged, but measurement precision deteriorates due to changes in elastic modulus
Solution Approach 1:
Insulating layers serve as protective intermediaries that prevent direct moisture contact with the conductive layers. This barrier function maintains the elastic modulus of the diaphragms by preventing moisture-induced material property changes, thereby preserving measurement precision
Solution Approach 2:
The harmful effect of moisture is extracted from the system by isolating the sensitive conductive layers from the external environment. The insulating layers effectively remove the moisture-conductive pathway, preventing elastic modulus changes in the diaphragm materials
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 proposed solution effectively reduces errors in detected capacitance values by canceling out stress influences, leading to more accurate measurements of differential pressures.
Implementation Method 1
A differential pressure between two pressures is detected by subtracting a capacitance value between the second diaphragm and the second conductive layer from a capacitance value between the first diaphragm and the second conductive layer
Implementation Method 2
when pressure is applied to the two films, the two films are deformed in directions opposite to each other, and accordingly an error in a detected pressure caused by the above-described various types of influence is canceled out and reduced
Data Source
AI summary
A pressure sensor chip includes a third conductive layer, a second insulating layer, a first conductive layer, a first insulating layer, and a second conductive layer stacked in order. The first insulating layer includes first and second cavities communicating externally. The second insulating layer includes third and fourth cavities respectively communicating with the second and first cavities. The first conductive layer includes first and second diaphragms, the second conductive layer includes first and second electrodes, and the third conductive layer includes third and fourth electrodes. The first diaphragm and the first electrode face each other with the cavity interposed therebetween, the second diaphragm and the electrode face each other with the first cavity interposed therebetween, the first diaphragm and the third electrode face each other with the fourth cavity interposed therebetween, and the second diaphragm and the fourth electrode face each other with the fourth cavity interposed therebetween.