Inertial Sensor Bonding Member Step Section Thermal Stress
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Solution Overview
Problem
Inertial sensors with die-bonding resins that rise along the side surfaces experience thermal stress, affecting the distance between movable elements and electrodes, leading to deterioration in detection characteristics.
Innovation Solution
The inertial sensor design incorporates a support substrate, a sensor main body, and a bonding member that extends along the first principal surface and a recessed step section, preventing the bonding member from spreading outward and reducing thermal stress transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If die-bonding resin is used to bond MEMS sensor to substrate, then bonding strength is improved, but thermal expansion causes stress transmission to sensor substrate deteriorating detection characteristics
Solution Approach 1:
The substrate is segmented into a first substrate and a second substrate that are disposed apart from each other, with the MEMS sensor bonded to the first substrate and the circuit board to the second substrate. This segmentation isolates the sensor from stress transmitted through the bonding resin, preventing thermal expansion stress from affecting detection characteristics while maintaining bonding strength.
Solution Approach 2:
A resin layer is introduced as an intermediary between the first substrate (carrying the MEMS sensor) and the second substrate (carrying the circuit board). This intermediate resin layer acts as a stress isolation barrier, allowing the bonding resin to provide strong adhesion while preventing thermal expansion stress from being transmitted to the sensitive sensor elements.
2Area of stationary object
If bonding member extends along side surface, then bonding area is increased, but bonding member rises in form of fillet transmitting stress to sensor
Solution Approach 1:
The bonding member is configured to extend primarily in the planar direction (along the first principal surface) rather than rising vertically along the side surface. This dimensional change in the bonding member's geometry allows sufficient bonding area to be achieved through lateral extension, preventing fillet formation and the associated stress transmission to the sensor while maintaining adequate bonding strength.
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 unintended changes in the sensor's output due to thermal stress, enhancing the accuracy of acceleration detection in multiple axes and improving long-term reliability.
Implementation Method 1
a bonding member that is located between the support substrate and the sensor main body and bonds the sensor main body to the support substrate
Implementation Method 2
The substrate has a side surface, a first principal surface facing the support substrate, and a recessed step section that is located between the side surface and the first principal surface and connects the side surface to the first principal surface. The bonding member extends along the first principal surface and the step section.
Data Source
AI summary
An inertial sensor includes a support substrate, a sensor main body supported by the support substrate, and a bonding member that is located between the support substrate and the sensor main body and bonds the sensor main body to the support substrate. The sensor main body includes a substrate bonded to the support substrate via the bonding member and a capacitance-type sensor device provided at a side of the substrate opposite to the support substrate. The substrate has a side surface, a first principal surface facing the support substrate, and a recessed step section that is located between the side surface and the first principal surface and connects the side surface to the first principal surface. The bonding member extends along the first principal surface and the step section.