Flexible Wiring Board Cutout for Sensor Chip Stress Relaxation
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Solution Overview
Problem
Conventional mechanical quantity measuring devices experience changes in sense output over time due to stress relaxation in the flexible wiring board, which affects the accuracy of measurements.
Innovation Solution
A mechanical quantity measuring device with a sensor chip supported on a flexible wiring board featuring a cutout near the sensor chip, allowing the wire to detour and reducing the adhering area that causes changes in sense output, thereby minimizing the impact of external tension and stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensor chip is deposited on the flexible wiring board, then the device is easier to handle and attach to the object to be measured, but the sense output changes with time due to stress relaxation in the flexible wiring board
Solution Approach 1:
The patent extracts the harmful portion of the flexible wiring board by creating a cutout that removes the adhesive application area near the sensor chip. This extraction eliminates the source of stress relaxation that causes sense output drift, while preserving the flexible wiring board's overall flexibility and ease of attachment functions.
Solution Approach 2:
The flexible wiring board is segmented into two functional zones: an area with adhesive for attachment to the object to be measured, and a cutout area near the sensor chip where no adhesive is applied. This segmentation allows different portions of the same component to serve different purposes - one for ease of attachment, another for maintaining measurement stability.
2Strength
If the flexible wiring board has a large adhering area for attachment, then the device attaches more securely to the object to be measured, but the stress relaxation in the adhering area causes changes in sense output over time
Solution Approach 1:
The harmful adhesive application area near the sensor chip is extracted through the cutout structure. This removes the source of stress relaxation that compromises measurement precision, while adhesive is still applied to other areas of the flexible wiring board to maintain secure attachment strength.
Solution Approach 2:
The adhesive application is made non-uniform through the cutout design: adhesive is applied in areas that do not interfere with the sensor chip (maintaining attachment strength), but deliberately avoided in the local area near the sensor chip (preserving measurement precision by eliminating stress relaxation in that critical zone).
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 device effectively stabilizes sense output over time, maintaining measurement accuracy by reducing the influence of stress relaxation and external tension on the sensor chip.
Implementation Method 1
a device which uses a sensor chip applying an effect of resistance that varies depending on the strain (piezoresistive effect)
Implementation Method 2
the sensor chip is attached to an object to be measured, with an adhesive
Implementation Method 3
the sense output may change with time in some cases
Data Source
AI summary
In a mechanical quantity measuring device (1) having a sensor chip (2) which outputs a sense output (S) corresponding to a mechanical quantity acting on the object to be measured (4), and a flexible wiring board (3) which supports the sensor chip (2) and has a wire (6) to lead out the sense output (S) to outside, and in which in measuring the mechanical quantity, the sensor chip (2) and the flexible wiring board (3) are attached to the object to be measured (4), a cutout (5) is provided on the flexible wiring board (3) near the sensor chip (2) and on the side where the wire (6) is arranged for the sensor chip (2). Thus, change in the sense output (S) with time can be restrained.