Pressure Sensor Center-Region Adhesive Bonding Thermal Stress
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Solution Overview
Problem
Conventional pressure sensor devices experience air bubble formation and wire disconnection due to thermal stress and linear expansion differences between the pressure sensor unit and resin case, leading to reduced accuracy and potential defects.
Innovation Solution
A pressure sensor device design where the sensor unit and resin case are constrained only in a small central region by adhesive, with a mold release agent applied to the peripheral region to prevent air bubble formation and reduce thermal stress, using a fluororesin-based adhesive to minimize deformation and wire breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the sensor unit is fully fixed to the resin case using adhesive, then the structural stability is improved, but thermal stress and wire disconnection occur due to linear expansion differences
Solution Approach 1:
The adhesive fixing region is segmented into a center region (first region) and a peripheral region (second region). The center region provides structural stability through adhesive bonding, while the peripheral region remains unbonded to accommodate thermal expansion differences and prevent wire disconnection.
Solution Approach 2:
Different regions of the sensor unit bottom surface have different adhesive bonding properties. The center region has high bonding strength for stability, while the peripheral region has reduced or no bonding to allow thermal movement, creating local quality variations that resolve the contradiction.
2Reliability
If the adhesive region is reduced to minimize thermal stress, then wire disconnection is prevented, but air bubbles form in the gap between sensor unit and resin case
Solution Approach 1:
The adhesive application is segmented such that adhesive is applied to the center region for stable bonding while the peripheral region remains unbonded. This segmentation allows the adhesive to be confined to areas where it provides benefit without creating gaps that trap air bubbles.
Solution Approach 2:
The adhesive is applied in advance only to the center region before assembling the sensor unit, ensuring proper placement and eliminating air pockets that would form if adhesive were applied to the entire surface or if gaps existed at the periphery.
3Manufacturing precision
If the adhesive region is made smaller than the diaphragm, then manufacturing precision and accuracy are improved, but the structural support is reduced
Solution Approach 1:
The adhesive bonding is concentrated in the center region which provides sufficient structural support while maintaining the benefit of reduced thermal stress. The peripheral region without adhesive allows for thermal expansion accommodation, creating a local quality distribution that balances support and precision.
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 design effectively reduces thermal stress and air bubble occurrence, maintaining sensor accuracy and preventing wire breakage, thereby enhancing the reliability and longevity of the pressure sensor.
Implementation Method 1
a center region of the bottom surface of the sensor unit is fixed to the resin case by an adhesive between the center region and the resin case
Implementation Method 2
a sensor chip having a diaphragm, the sensor chip being configured to convert pressure caused by deformation of the diaphragm into an electrical signal
Implementation Method 3
differences in the linear expansion coefficients of the pressure sensor unit, and an adhesive due to temperature change
Data Source
AI summary
A pressure sensor device, comprising: a sensor unit having a sensor chip having a diaphragm, the sensor chip being configured to convert pressure caused by deformation of the diaphragm into an electrical signal, and a member supporting the sensor chip; and a resin case housing the sensor unit. The sensor unit is so disposed that a bottom surface thereof faces the resin case with an adhesive disposed therebetween. The bottom surface of the sensor unit has a center region and a peripheral region that are mutually exclusive. The center region of the bottom surface of the sensor unit is fixed to the resin case by the adhesive between the center region and the resin case, and the peripheral region of the bottom surface of the sensor unit is not fixed to the resin case by the adhesive between the peripheral region and the resin case.