Packaged Pressure Sensor With Ultrasonic Foreign Material Detection
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Solution Overview
Problem
Existing pressure sensors in portable and wearable devices face issues with false positives in detecting environmental changes due to foreign materials, particularly liquids like water, which can affect pressure signal accuracy and cause undesired function disabling.
Innovation Solution
Integration of a piezoelectric transduction structure, such as a PMUT, within the pressure sensor package to detect foreign materials using ultrasonic waves, allowing accurate identification of acoustic impedance changes caused by the presence of contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If automatic detection of operating environment variation is implemented based on pressure value thresholds, then the system can automatically activate/deactivate specific functions and vary full scale value, but false positives occur when foreign material enters the cavity causing incorrect environment detection
Solution Approach 1:
The patent introduces an acoustic wave transducer as an intermediary detection mechanism. Instead of relying solely on pressure value thresholds which can be misleading due to foreign material presence, the transducer sends acoustic waves through the coating gel to detect changes in acoustic impedance. This intermediary acoustic detection method provides reliable information about foreign material presence, allowing the system to distinguish between actual environment changes and false conditions caused by contaminants.
2Adaptability or versatility
If pressure sensor is made waterproof with coating gel filling the cavity, then the sensor can be used in underwater applications, but foreign material such as water can enter the cavity and affect pressure signal accuracy
Solution Approach 1:
The acoustic wave transducer acts as an intermediary detection system that monitors the integrity of the waterproof seal. By sending acoustic waves through the coating gel and analyzing the reflected signals, the system can detect the presence of foreign material without compromising the waterproof design. This allows the pressure sensor to maintain its underwater capability while providing a mechanism to detect when foreign material contamination occurs.
Solution Approach 2:
The patent implements a feedback mechanism where the acoustic wave detection system continuously monitors the cavity environment and provides information back to the processing circuit. When foreign material is detected through acoustic impedance changes, the system receives feedback about the contamination status and can adjust its operation accordingly, such as disabling pressure measurement functions until the foreign material is removed.
3Device complexity
If the pressure sensor uses a single full scale for environmental pressure detection, then the device structure remains simple, but the sensor cannot accurately detect both environmental pressure and underwater pressure with different scales
Solution Approach 1:
The acoustic wave transducer serves multiple functions: it detects foreign material presence, determines whether the device is in air or water environment, and enables the pressure sensor to accurately switch between different full scale values. This single component provides universal detection capability that supports both environmental pressure monitoring and underwater pressure measurement, eliminating the need for separate detection systems for different environments.
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
Enhances detection accuracy of foreign materials, reduces false positives, and enables timely adjustments in function activation/deactivation based on reliable environmental change detection.
Implementation Method 1
a piezoelectric transduction structure, of a ultrasonic type
Implementation Method 2
detect foreign material on said coating material within said package
Data Source
AI summary
A pressure sensor device has: a pressure detection structure provided in a first die of semiconductor material; a package, configured to internally accommodate the pressure detection structure in an impermeable manner, the package having a base structure and a body structure, arranged on the base structure, with an access opening in contact with an external environment and internally defining a housing cavity, in which the first die is arranged covered with a coating material. A piezoelectric transduction structure, of a ultrasonic type, is accommodated in the housing cavity, in order to allow detection of foreign material above the coating material and within the package. In particular, the piezoelectric transduction structure is integrated in the first die, which comprises a first portion, wherein the pressure detection structure is integrated, and a second portion, separate and distinct from the first portion, wherein the piezoelectric transduction structure is integrated.