Sensor Electrode-Protective Film Interface for Moisture Blocking
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Solution Overview
Problem
Existing sensor members face reliability issues due to moisture intrusion through the interface between the electrode and protective film, especially in harsh environments like high temperature and high humidity.
Innovation Solution
A sensor member design with a protective film structure that includes a thicker second protective film portion around the opening edges and a continuous interface with the electrode, preventing moisture intrusion by minimizing the exposed area and ensuring smooth connection without steps, along with the use of chemically stable electrodes and adhesive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective film is provided to protect the detection portion, then the reliability of the sensor member is improved, but moisture may intrude through the interface between the electrode and the protective film
Solution Approach 1:
The protective film is designed with varying thickness: a first thickness in the central region and a second thickness (greater than the first) at the peripheral region surrounding the opening. This local variation in thickness creates a stepped structure where the thicker peripheral portion extends further laterally, forming an overlapping configuration with the electrode that prevents moisture intrusion at the interface while maintaining adequate protection of the detection portion.
2Reliability
If the electrode is formed to ensure electrical connection with the detection portion, then electrical connectivity is achieved, but the opening area in the protective film cannot be completely covered
Solution Approach 1:
The protective film is configured with a stepped thickness structure where the peripheral portion (second thickness) extends laterally beyond the opening edges. This creates an overlapping region in the lateral dimension where the protective film and electrode coexist, effectively covering the opening area through vertical layering rather than horizontal expansion.
3Reliability
If the protective film thickness is increased around the opening edges, then moisture intrusion is prevented, but the device complexity increases
Solution Approach 1:
The protective film thickness parameter is varied spatially: a first thickness value is used in the central region while a second thickness value (greater than the first) is used at the peripheral region. This parameter change creates the stepped structure that provides enhanced moisture protection without requiring additional components or complex multi-layer configurations.
Data Source
AI summary
A sensor member capable of suitably preventing a problem such as the intrusion of moisture or the like through an interface between an electrode and a protective film, including: a protected portion provided on one surface of a metal base and including a detection portion; a protective film including a first protective film portion having a first thickness and a second protective film portion having a second thickness thicker than the first thickness and formed at an opening peripheral edge of an opening leading to the protected portion, and covering at least a part of the protected portion from above; and an electrode portion including a first electrode portion disposed in the opening and connected to the protected portion, and a second electrode portion connected to the first electrode portion at an outer peripheral edge of the first electrode portion and formed on the second protective film portion.