Inertial Sensor Mounting Layout to Reduce Temperature Hysteresis
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Solution Overview
Problem
Inertial sensor units, such as those described in JP-A-2017-20829, often experience temperature hysteresis in bias signals due to foreign matters remaining between the sensors and the substrate, leading to reduced detection accuracy.
Innovation Solution
The sensor unit design includes a circuit board with an insulating layer on the electrode pads and recessed sections, allowing for a larger gap between the inertial sensor and the circuit board, facilitating easier cleaning and reducing the likelihood of foreign matter retention, thereby minimizing temperature-related stress and hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the inertial sensor is surface-mounted on the substrate, then the sensor unit can be compactly constructed, but foreign matters remain between the sensor and substrate causing temperature hysteresis
Solution Approach 1:
The insulating layer is divided into multiple regions: a first region with the insulating layer providing electrical insulation, and a second region without the insulating layer creating a gap between the sensor and substrate. This segmentation allows the sensor to be mounted compactly while preventing foreign matter retention in the gap region, thereby eliminating temperature hysteresis and maintaining detection accuracy.
2Reliability
If the insulating layer is provided on the electrode pads, then electrical insulation is ensured, but foreign matters may remain between the sensor and substrate
Solution Approach 1:
The insulating layer is segmented into a first region covering the electrode pads for electrical insulation and a second region omitted to create a gap. This segmentation ensures that the insulating layer provides necessary electrical insulation while the gap region prevents foreign matter retention, as the gap allows for proper spacing and eliminates the trapping of contaminants.
3Volume of moving object
If the gap between sensor and substrate is small, then the sensor unit is compact, but cleaning becomes difficult and foreign matters remain
Solution Approach 1:
By segmenting the insulating layer configuration, a controlled gap is created in the second region between the sensor and substrate. This gap is large enough to prevent foreign matter retention and facilitate cleaning, while the overall sensor unit remains compact due to the insulating layer's presence in the first region maintaining proper electrical spacing.
Data Source
AI summary
A sensor unit includes a circuit board including, on a first surface, a plurality of electrode pads to which a plurality of mounting terminals of an inertial sensor are respectively attached via connecting members. The first surface of the circuit board includes an insulating layer provided on the outer side of the plurality of electrode pads in a plan view, includes, in a portion overlapping a center region further on the inner side than the mounting terminals of the inertial sensor in the plan view, a first region where the insulating layer is not provided, and includes, from the first region to the outer side of the inertial sensor in the plan view, a second region where the insulating layer is not provided.