Silicon Pressure Sensor Overpressure Stop With Glass Frit Gap Control
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Solution Overview
Problem
Existing silicon-based pressure sensors have limited over-pressure capability and are prone to catastrophic failure due to excessive pressure, which exceeds the crystalline structure's fracture strength, and modern manufacturing techniques struggle to achieve precise tolerances for overpressure features.
Innovation Solution
A pressure sensor design incorporating a deflectable diaphragm with an overpressure feature mounted on a silicon die, utilizing a glass frit bonding technique to ensure precise alignment and engagement of an overpressure pedestal, and etching to control gap dimensions with micrometer-level precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If crystalline diaphragms are used to provide monotonic movement, then measurement precision is improved, but overpressure capability deteriorates due to limited fracture strength
Solution Approach 1:
The sensor is divided into two separate silicon dies: a first silicon die containing the crystalline diaphragm for precise measurement, and a second silicon die serving as a backup structure. This segmentation allows the measurement function and overpressure protection function to be separated, enabling the crystalline diaphragm to provide monotonic movement while the second die provides overpressure capability.
Solution Approach 2:
The second silicon die is positioned to contact the first silicon die at a predetermined interface, creating a mechanical stop before the crystalline diaphragm can experience excessive pressure. This beforehand cushioning prevents the diaphragm from reaching fracture conditions by engaging the second die as a protective barrier.
2Manufacturing precision
If etching is used to control gap dimensions, then manufacturing precision is improved, but device complexity increases due to additional processing steps
Solution Approach 1:
The etching process is applied to the silicon dies themselves, utilizing the material's inherent properties to create the required gap dimensions. The silicon material is etched to form the deflectable diaphragm and the spacing structure, allowing the material to define its own dimensional characteristics through controlled removal rather than requiring separate spacing components.
Solution Approach 2:
The gap dimension is controlled by changing the etching parameters (etch depth, etch rate, etch pattern) rather than requiring mechanical adjustment or additional components. By precisely controlling the etching process parameters, the desired micrometer-level gap precision is achieved directly during fabrication.
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 enables a pressure sensor with enhanced overpressure protection, engaging quickly and accurately beyond the upper measurement limit, thereby preventing diaphragm failure and extending the pressure sensing range while maintaining manufacturing precision.
Implementation Method 1
Glass frit is disposed in the frit gap
Implementation Method 2
a flexible diaphragm moves relative to a base in response to pressure applied to the top of the diaphragm
Implementation Method 3
The diaphragm typically includes one or more electrical structures, such as electrodes or traces, that have an electrical characteristic, such as resistance or capacitance, that changes with the deflection of the sensing diaphragm
Data Source
AI summary
A pressure sensor includes a first silicon die having a deflectable diaphragm and a second silicon die contacting the first silicon die at an interface. An electrical structure is mounted relative to one of the first and second silicon dies. The electrical structure has an electrical characteristic that changes based on deflection of the deflectable diaphragm. An overpressure feature is mounted relative to one of the first silicon die and the second silicon die. The overpressure feature has a surface that is configured to contact the other of the first silicon die and second silicon die during an overpressure condition. At least one frit region has a frit gap. Glass frit is disposed in the frit gap. A pressure transmitter having the above-described pressure sensor is also disclosed.