SAW Strain Sensor Temperature Compensation Split-Carrier Package
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Solution Overview
Problem
Conventional SAW strain sensors face challenges in temperature compensation, particularly in manufacturing and practical application, due to the complexity of separating temperature and strain influences, which leads to inaccurate strain measurements and difficulties in mass production.
Innovation Solution
A temperature-compensated SAW sensor apparatus with a package that isolates the reference die from mechanical strain and maintains both dies at the same temperature, using a split-shim base with thermally conductive materials to ensure accurate temperature compensation across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference die is used for temperature compensation in SAW strain sensors, then temperature compensation accuracy is improved, but manufacturing complexity and difficulty increase due to the need for precise mechanical separation and adhesion control
Solution Approach 1:
The sensor is divided into two separate dies: a measurement die that experiences both strain and temperature, and a reference die that experiences only temperature. This segmentation allows independent optimization of each die's function and simplifies the manufacturing process by eliminating the need for precise mechanical separation on a single substrate.
Solution Approach 2:
A thermally conductive adhesive is introduced as an intermediary material to bond both dies to the substrate. This adhesive serves as a thermal pathway that ensures both dies experience the same temperature conditions, enabling accurate temperature compensation while simplifying the manufacturing process.
2Measurement precision
If individual die manipulation and sawcutting is performed for each sensor, then temperature compensation is achieved, but manufacturing time and labor intensity increase significantly
Solution Approach 1:
Both the measurement die and reference die are fabricated and mounted on the substrate simultaneously before final assembly. This preliminary action allows mass production techniques to be applied, eliminating the need for individual die manipulation and sawcutting operations for each sensor.
Solution Approach 2:
The mounting processes for both dies are merged into a single operation where both dies are bonded to the substrate at the same time using the same thermally conductive adhesive. This combining of operations dramatically reduces manufacturing time and labor requirements.
3Measurement precision
If precise adhesive application and clamping is performed in a controlled environment, then strain isolation of the reference die is achieved, but the process becomes difficult to implement for arbitrary components
Solution Approach 1:
The thermally conductive adhesive serves dual functions: it provides mechanical bonding and simultaneously acts as a thermal pathway. This self-service approach eliminates the need for complex clamping mechanisms and controlled environment processes, making the sensor adaptable to various components and field conditions.
4Reliability
If wire bonding is performed after mounting the SAW substrate on the test article, then electrical connection is achieved, but multiple obstacles including cleanliness maintenance and space limitations arise
Solution Approach 1:
Electrical connections are established before mounting the sensor on the test article. This preliminary action allows wire bonding to be performed in a controlled manufacturing environment with proper equipment and cleanliness protocols, eliminating the obstacles of space limitations and difficulty in maintaining cleanliness during field installation.
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 solution achieves strain measurement resolutions better than 0.2με and allows for easier handling and attachment of the sensor without cleanliness concerns, enabling practical applications in various attachment methods.
Implementation Method 1
The package is thermally conductive and maintains both die at the same temperature
Implementation Method 2
acoustic wave devices, which are generally built on piezoelectric substrates, are sensitive to mechanical stresses
Data Source
AI summary
The present disclosure provides a new and improved temperature compensated surface-launched acoustic wave (SAW) strain sensor using multiple reflectors in SAW devices mounted on a split-carrier package that provides complete isolation from strain for a temperature sensing portion of the device, while exposing a strain sensing portion of the device to both strain and temperature, with the influence of temperature being common to the various portions of the device, and a single acoustic reference with respect to which multiple differential acoustic measurements can be made, to provide inherently temperature-compensated strain measurements.