Thermal Flow Sensor Barrier Layer for Mass Flow Controller Drift
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Solution Overview
Problem
Mass flow controllers (MFCs) used in electronic device manufacturing experience 'drift' or shifting in mass flow rate accuracy over time, leading to adverse effects on production yield, especially when handling corrosive process gases.
Innovation Solution
A thermal flow sensor with a sensor tube having an inner surface coated with a material to form an inner barrier layer, which prevents corrosive reactions and maintains accurate mass flow rate measurements and control, is integrated into the MFC, coupled with a flow rate control valve and a controller to adjust the flow rate as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermal flow sensor is used to measure mass flow rate, then measurement capability is provided, but the sensor accuracy drifts over time when exposed to corrosive process gases
Solution Approach 1:
A barrier layer is introduced as an intermediary substance between the corrosive process gas and the thermal flow sensor. This barrier layer prevents direct contact between the corrosive gas and the sensor, thereby maintaining measurement accuracy and stability over time without affecting the sensor's measurement capability
Solution Approach 2:
The barrier layer creates an inert protective environment around the thermal flow sensor, isolating it from the corrosive process gases. This inert environment prevents chemical reactions and corrosion that would otherwise cause measurement drift, allowing the sensor to maintain its calibration and accuracy
2Manufacturing precision
If process gases are delivered with high mass flow rate accuracy, then electronic device manufacturing precision is improved, but the system experiences drift in accuracy over time
Solution Approach 1:
The barrier layer serves as a protective intermediary that prevents corrosive process gases from degrading the thermal flow sensor. This protection ensures that the mass flow rate measurements remain accurate and stable over time, thereby maintaining the high manufacturing precision required for electronic device fabrication
Solution Approach 2:
The barrier layer is applied in advance to the thermal flow sensor before the sensor is exposed to corrosive process gases. This preliminary protective action prevents corrosion and measurement drift before they can occur, ensuring long-term reliability of the mass flow control system
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 precise control of mass flow rates within predetermined accuracy, preventing drift and maintaining production quality by protecting the sensor from corrosive gases and improving repeatability of flow detection.
Implementation Method 1
The thermal flow sensor is configured to measure a mass flow rate of a gas flowing through the mass flow controller
Implementation Method 2
The inner surface is coated with a material to form an inner barrier layer
Data Source
AI summary
An electronic device manufacturing system includes a mass flow controller (MFC) that has a thermal flow sensor. The thermal flow sensor may measure a mass flow rate and may include a sensor tube having an inner surface coated with a material to form an inner barrier layer. The inner barrier layer may prevent or substantially reduce the likelihood of a corrosive reaction from occurring on the inner surface, which may prevent or reduce the likelihood of the MFC drifting beyond the MFC's mass flow rate accuracy specifications. This may improve the repeatability of flow detection by the MFC. Methods of measuring and controlling a mass flow rate in an electronic device manufacturing system are also provided, as are other aspects.