Gas Sensor Protective Layer Structure Against Moisture Capillarity
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Solution Overview
Problem
Existing sensor elements face challenges in preventing moisture from reaching the connector electrodes, which can lead to corrosion and other issues due to the presence of moisture in the measurement-object gas.
Innovation Solution
A sensor element with a protective layer having a thickness of 10 μm or less and a ratio of thicknesses T1/T2 of 1.0 or less is employed, where T1 is the thickness of the protective layer and T2 is the thickness of the front-side portion, to reduce moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is used to protect the connector electrode from moisture, then the reliability is improved, but the moisture can still penetrate through the protective layer by capillarity
Solution Approach 1:
The protective layer is divided into multiple layers with different thicknesses. The first protective layer has a thickness of 10 μm or less to reduce capillary action, while a second protective layer may have a different thickness to provide additional protection. This segmentation allows each layer to perform its specific function optimally.
Solution Approach 2:
Different regions of the protective layer have different thicknesses tailored to their specific needs. The region covering the connector electrode has a controlled thickness (T1 ≤ 10 μm) to prevent moisture penetration, while other regions may have different thicknesses to provide mechanical protection or meet other requirements.
2Reliability
If the protective layer thickness is increased to prevent moisture penetration, then the reliability is improved, but the capillary action of moisture is enhanced
Solution Approach 1:
The thickness parameter of the protective layer is optimized to be 10 μm or less. This parameter change reduces the capillary action of moisture while still providing adequate protection. The thickness is carefully controlled to balance protection needs with moisture penetration resistance.
3Reliability
If the protective layer is made thinner to reduce moisture penetration, then the reliability is improved, but the mechanical protection is reduced
Solution Approach 1:
The protective structure is segmented into multiple layers with different thicknesses and functions. The first protective layer (T1 ≤ 10 μm) provides moisture penetration resistance, while a second protective layer provides mechanical protection. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
The protective structure uses a composite of multiple layers with different properties. The combination of a thin first protective layer and a thicker second protective layer creates a composite structure that provides both moisture penetration resistance and mechanical strength.
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 protective layer effectively minimizes moisture reaching the connector electrodes, thereby reducing corrosion and enhancing the reliability and performance of the sensor element.
Implementation Method 1
Since moisture is unlikely to pass through the dense layer, in the case where moisture included in the measurement-object gas moves inside the porous layer by the capillarity
Data Source
AI summary
A sensor element includes an element body, an upper connector electrode disposed on a first surface of the element body, and a protective layer that covers at least a front end-side part of the first surface. The protective layer includes a first specific protective layer having a thickness T1 of 10 μm or less. The ratio T1/T2 of the thickness T1 to the thickness T2 of a front-side portion of the protective layer which faces the front end of the first specific protective layer is 1.0 or less.