Foamed Rubber Seal for Sensor Circuit Board Stress Reduction
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Solution Overview
Problem
Conventional sensors for detecting hydrogen leakage, where the sensor element is mounted directly on a circuit board housed in a casing member with an O-ring seal, face issues of stress-induced breakage of wiring traces and solder portions due to high pressure, and thermal expansion leading to potential damage.
Innovation Solution
A sensor design where the circuit board partially forms a measurement chamber, using a foamed rubber elastic seal member with flat end surfaces to reduce stress on the circuit board, providing a satisfactory seal without high-pressure fixation, thus preventing breakage and allowing for a simpler casing member structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an O-ring is pressed against the circuit board under high pressure to establish a hermetic seal, then sealing performance is improved, but stress-induced breakage of wiring traces and solder portions occurs
Solution Approach 1:
The patent changes the material parameter from conventional rubber O-ring to foamed rubber elastic seal member. This material substitution fundamentally alters the compression characteristics, allowing sealing at lower pressures while maintaining the hermetic seal function and preventing stress-induced breakage of wiring traces and solder portions.
Solution Approach 2:
The patent employs foamed rubber as an elastic seal member that combines the benefits of rubber elasticity with the stress-absorbing properties of foamed structure. This composite material approach enables the seal to deform and absorb mechanical stresses while maintaining sealing effectiveness, thereby protecting the circuit board from damage.
2Reliability
If the O-ring is pressed against the circuit board under high pressure to firmly fix the casing member, then sealing is improved, but thermal expansion forces are transmitted to the circuit board causing breakage
Solution Approach 1:
The foamed rubber elastic seal member serves as a cushioning element that absorbs and dissipates thermal expansion forces before they can be transmitted to the circuit board. The foam structure acts as a shock-absorbing medium, protecting the circuit board from thermal stress and preventing breakage of wiring traces and solder portions.
Solution Approach 2:
By changing from conventional rubber to foamed rubber material, the patent alters the thermal and mechanical parameters of the seal member. The foamed structure provides superior thermal insulation and stress absorption, reducing the transmission of thermal expansion forces to the circuit board while maintaining sealing performance.
3Reliability
If an O-ring is used to seal between the circuit board and casing member, then a measurement chamber is formed, but the casing member structure becomes complex
Solution Approach 1:
The patent merges the sealing function with the circuit board structure by using the foamed rubber elastic seal member to directly seal between the circuit board and casing member. This integration eliminates the need for separate sealing components and complex casing member structures, while still forming an effective measurement chamber.
Solution Approach 2:
The material parameter change from conventional rubber O-ring to foamed rubber enables a simpler sealing arrangement. The foamed rubber's unique properties allow it to function as both a seal and a stress-absorbing element, reducing the need for complex structural features in the casing member while maintaining the measurement chamber integrity.
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 sensor effectively prevents damage to the circuit board by reducing stress and allowing for absorption of external impacts, maintaining airtightness while simplifying the casing member's design and reducing material usage.
Implementation Method 1
an annular elastic seal member which is interposed between the element attachment surface and the casing member... the elastic seal member is formed of foamed rubber... the elastic seal member is compressed between the flat portions of the end surfaces
Data Source
AI summary
A sensor includes a sensor element; a circuit board having an element attachment surface on which the sensor element is mounted; a casing member for housing the circuit board, the casing member having a measurement chamber which faces the sensor element and communicates with the target atmosphere through a gas inlet; an annular elastic seal member which is interposed between the element attachment surface and the casing member in such a manner that the elastic seal member is in contact with the element attachment surface. The elastic seal member is made of foamed rubber and has an end surface flat portion which faces the casing member and another end surface flat portion which faces the element attachment. The elastic seal member is interposed between the element attachment surface and the casing member such that the elastic seal member is compressed between the flat portions of the end surfaces.