Sensor Module Relay Substrate Thermal Stress Distribution
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Solution Overview
Problem
The existing inertial measurement devices, such as those described in JP-A-2017-020829, face challenges with the mounting reliability of X-axis and Y-axis angular velocity sensors due to their placement on the side surfaces of the substrate, which can lead to changes in detection characteristics over time.
Innovation Solution
The proposed sensor module incorporates a substrate with a first relay substrate and a second relay substrate, each with a specific linear expansion coefficient, to distribute thermal stress and improve mounting reliability. The X-axis and Y-axis angular velocity sensors are mounted on these relay substrates, which are bonded to the substrate from both the upper and lower surfaces, enhancing bonding strength and electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the X-axis and Y-axis angular velocity sensors are mounted on the side surfaces of the substrate, then the device can be compact, but the mounting reliability is low and detection characteristics change over time
Solution Approach 1:
A relay substrate is introduced as an intermediary component between the substrate and the angular velocity sensors. The relay substrate has a first surface mounted on the substrate and a second surface mounted on the sensor, serving as a mediator that distributes thermal stress and improves mounting reliability while maintaining compact device structure
Solution Approach 2:
The linear expansion coefficient of the relay substrate is specifically controlled to be between those of the substrate and the sensor package. This parameter optimization allows the relay substrate to accommodate thermal expansion differences and reduce stress concentrations, thereby improving reliability without increasing device volume
2Device complexity
If the X-axis and Y-axis angular velocity sensors are mounted on the side surfaces of the substrate, then the device structure is simple, but the bonding strength is insufficient
Solution Approach 1:
The relay substrate acts as a bonding intermediary that connects the substrate and the sensor through multiple bonding interfaces. By distributing the bonding load across the relay substrate's first and second surfaces, the overall bonding strength is enhanced while maintaining relatively simple device structure
Solution Approach 2:
The mounting structure is segmented into three distinct layers: the substrate, the relay substrate, and the sensor package. This segmentation allows each component to be optimized independently and creates multiple bonding interfaces that collectively enhance bonding strength without significantly increasing structural complexity
3Ease of manufacture
If the linear expansion coefficient of the relay substrate is not optimized, then manufacturing is easier, but thermal stress concentrations reduce reliability
Solution Approach 1:
The linear expansion coefficient of the relay substrate is optimized to fall within a specific range between those of the substrate and the sensor package. This parameter optimization reduces thermal stress concentrations and improves reliability, while the relay substrate remains manufacturable using standard materials and processes
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 reduces thermal stress concentrations, improves the mounting reliability of the angular velocity sensors, and maintains the detection characteristics over time, enhancing the overall performance of the sensor module.
Implementation Method 1
α1 represents a linear expansion coefficient of the substrate in the first direction, α2 represents a linear expansion coefficient of the first relay substrate in the first direction, and α3 represents a linear expansion coefficient of the first package in the first direction
Data Source
AI summary
A sensor module includes: a substrate having a first surface and a second surface that are in a front-back relationship with each other, and side surfaces including a first side surface; a first relay substrate having a first front surface and a first back surface and mounted on the first side surface with the first back surface facing the first side surface, the first front surface and the first back surface being in a front-back relationship with each other; and a first inertial sensor including a first package mounted on the first front surface of the first relay substrate and a first sensor element housed in the first package.