Partial Acoustic Coupling Medium for MEMS Ultrasonic Sensors
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Solution Overview
Problem
Sensor devices often face defective acoustic coupling due to cavities, air bubbles, or impurities between the touch-sensitive surface and the sensor, which hampers their operation in applications like touchscreens.
Innovation Solution
A sensor device with MEMS structures configured to transmit and receive ultrasonic signals, featuring an acoustic coupling medium that partially covers the sensor chip's surface, optimizing the decoupling and injection of ultrasonic signals, and a manufacturing method involving selective deposition of the acoustic coupling medium on MEMS structures before wafer separation into sensor chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic coupling medium is applied between touch-sensitive surface and sensor, then acoustic coupling is improved, but material usage and cost increase
Solution Approach 1:
The acoustic coupling medium is selectively applied only in specific regions where acoustic coupling is needed, rather than covering the entire sensor surface. This localized application maintains effective acoustic coupling between the touch-sensitive surface and sensor while minimizing material consumption and reducing the risk of impurities affecting large areas.
Solution Approach 2:
Instead of applying acoustic coupling medium across the full sensor area, the invention uses partial coverage with the medium applied only where necessary for acoustic coupling. This partial action approach achieves the required acoustic coupling effect while using less material and reducing potential harmful effects from excess medium.
2Reliability
If acoustic coupling medium is applied to ensure adequate coupling, then signal transmission is improved, but unwanted reflections and impurities increase
Solution Approach 1:
The acoustic coupling medium is applied selectively in localized regions rather than uniformly across the entire sensor surface. This localized application ensures adequate acoustic coupling for signal transmission while minimizing the total amount of medium present, thereby reducing unwanted reflections and the likelihood of impurities forming in excess material.
Solution Approach 2:
The invention acknowledges that acoustic coupling medium can cause unwanted reflections and impurities, but converts this potential harm into benefit by precisely controlling where the medium is applied. The selective application ensures the medium provides necessary coupling while its limited presence reduces harmful reflections, turning a potential problem into a controlled solution.
3Manufacturing precision
If selective deposition of acoustic coupling medium is implemented, then manufacturing precision is improved, but manufacturing complexity increases
Solution Approach 1:
The acoustic coupling medium is deposited selectively on the sensor chip before the chip is separated from the semiconductor wafer. This preliminary action allows the coupling medium to be applied in a controlled manner while the chip is still part of the larger wafer structure, potentially simplifying the deposition process and reducing the complexity of subsequent handling steps.
Solution Approach 2:
The deposition of acoustic coupling medium is combined with the wafer-level processing steps, allowing selective application to occur while multiple chips are still mounted on the semiconductor wafer. This merging of operations reduces manufacturing complexity by performing the selective deposition in a batch process rather than requiring individual chip handling.
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 ensures reliable detection of touch events by minimizing unwanted reflections and impurities, providing improved acoustic coupling and reduced material usage, thus enhancing the sensor's operational reliability and manufacturing efficiency.
Implementation Method 1
an acoustic coupling medium arranged selectively on the at least one MEMS structure, wherein the acoustic coupling medium is configured to decouple an ultrasonic signal to be emitted from the at least one MEMS structure and/or to inject a received ultrasonic signal into the at least one MEMS structure
Data Source
AI summary
A sensor device contains at least one sensor chip having at least one MEMS structure arranged at a main surface of the at least one sensor chip, wherein the at least one sensor chip is configured to transmit ultrasonic signals and/or to receive ultrasonic signals. The sensor device further contains an acoustic coupling medium arranged selectively on the at least one MEMS structure, wherein the acoustic coupling medium is configured to decouple an ultrasonic signal to be emitted from the at least one MEMS structure and/or to inject a received ultrasonic signal into the at least one MEMS structure. The acoustic coupling medium only partially covers the main surface of the at least one sensor chip.