Adhesive Member Bonding Sensor Device to Case for Thermal Stress Suppression
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Solution Overview
Problem
Existing sensor units face reduced detection accuracy due to external vibrations and thermal stress, which causes deformation and stress on inertial sensors, especially when exposed to high temperatures and upon temperature changes.
Innovation Solution
A sensor unit configuration where an adhesive member is used to securely bond the sensor device, substrate, and case member together, ensuring continuous coverage over the sensor device and its outer periphery, with a linear expansion coefficient higher than the substrate and case member, to minimize deformation and stress during temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the adhesive member is not connected to the inner wall of the case member (leaving a space between them), then the assembly is easier to manufacture, but thermal stress deformation cannot be suppressed after temperature changes
Solution Approach 1:
The adhesive member acts as an intermediary between the substrate and the case member, filling the space between them and bonding to both surfaces. This intermediary role allows the adhesive to absorb and distribute thermal stress, preventing direct stress transmission to the sensor device while maintaining structural integrity and detection accuracy stability after temperature changes.
Solution Approach 2:
The adhesive member is specifically selected with a linear expansion coefficient that matches or is compatible with the substrate and sensor device, differing from the case member material. This parameter change in material selection allows the adhesive to accommodate differential thermal expansion between components, suppressing deformation and stress after temperature changes while maintaining ease of assembly.
2Ease of manufacture
If the adhesive member covers only the substrate without extending to the outer edge of the sensor device, then the manufacturing process is simpler, but thermal stress and vibration cannot be effectively suppressed
Solution Approach 1:
The adhesive member's coverage area is segmented into two functional zones: a central area covering the substrate for basic bonding, and an extended outer peripheral area reaching the outer edge of the sensor device for enhanced stress suppression. This segmentation allows the adhesive to simultaneously provide structural support and protect against thermal stress and vibration, maintaining manufacturing simplicity while improving measurement precision.
Solution Approach 2:
The adhesive member extends not only in the planar dimension but also in the vertical dimension by reaching from the substrate surface to the outer edge and side surface of the sensor device. This dimensional extension creates a three-dimensional adhesive structure that effectively suppresses thermal stress and vibration from multiple directions, protecting the sensor device while maintaining manufacturing feasibility.
3Strength
If the adhesive member is used to bond the substrate and case member, then the structural integrity is improved, but the linear expansion coefficient mismatch causes deformation and stress at high temperatures
Solution Approach 1:
The adhesive member is specifically selected with a linear expansion coefficient that matches or is compatible with the substrate and sensor device, differing from the case member material. This parameter change in material selection allows the adhesive to accommodate differential thermal expansion between components, suppressing deformation and stress after temperature changes while maintaining ease of assembly.
Solution Approach 2:
The sensor unit employs a composite material strategy where the adhesive member serves as a distinct material layer with specifically tailored properties介于 between the substrate and case member. This composite structure, with the adhesive having intermediate expansion characteristics, allows differential expansion of metal and resin components while maintaining overall structural integrity and dimensional stability at high temperatures.
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
This configuration effectively suppresses changes in detected values over time, maintaining accurate inertia detection even under temperature fluctuations and external vibrations.
Implementation Method 1
differences occur, when returned to a normal temperature, in the return of the members from the deformation due to the thermal stress because of differences among linear expansion coefficients of the respective members
Implementation Method 2
an adhesive member bonding the sensor device and the case member together and bonding the substrate and the case member together
Data Source
AI summary
A sensor unit includes: a sensor device including an inertial sensor; a substrate to which the sensor device is bonded; a case member accommodating at least the sensor device; and an adhesive member provided to cover, in a plan view of the substrate as viewed from the case member side, an outer periphery of the sensor device and so as to connect the sensor device with the case member.