Thermal Mass Flow Meter Chip Mounting for Reduced Thermal Resistance
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Solution Overview
Problem
Conventional thermal mass flow meters face challenges in achieving high measuring sensitivity and stability due to thermal resistance issues caused by coating resins and uneven adhesive thickness, leading to variations in ambient temperature effects.
Innovation Solution
The thermal mass flow meter employs chip-type heater and temperature sensor chips with molding resin coatings, anchored on the piping with thermal conductive adhesives to minimize thermal resistance and heat loss, and includes a temperature-measuring element for ambient temperature correction to stabilize flow rate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If temperature sensor chips are coated with molding resin for protection and electrical connection, then ease of manufacture is improved, but thermal resistance increases causing reduced measurement precision
Solution Approach 1:
The patent divides the temperature sensing function into separate chips that can be independently mounted on the piping surface, allowing the molding resin coating to be minimized or eliminated at the critical sensing interface while maintaining protection and electrical connection through alternative means
Solution Approach 2:
The patent introduces thermal conductive adhesives as intermediary substances between the temperature sensor chips and the piping surface, which provide both mechanical bonding and high thermal conductivity to compensate for any thermal resistance from coatings, thereby maintaining measurement precision
2Ease of operation
If adhesive thickness is varied to accommodate uneven surfaces, then ease of operation is improved, but thermal resistance varies leading to reduced measurement precision
Solution Approach 1:
The patent specifies controlling the adhesive thickness within a narrow range (5-20 μm) to optimize thermal conduction while maintaining ease of application on uneven surfaces, balancing operational simplicity with measurement precision through parameter optimization
Solution Approach 2:
The patent uses thermal conductive adhesives as composite materials that combine bonding functionality with high thermal conductivity properties, allowing varied adhesive thickness to be compensated by the material's inherent thermal properties, thus maintaining measurement precision
3Measurement precision
If heater and temperature sensors are assembled on a single substrate using MEMS technique, then measurement precision is improved due to close proximity, but manufacturing cost increases and device complexity increases
Solution Approach 1:
The patent separates the heater and temperature sensors into independent components that can be mounted individually on the piping, eliminating the need for complex MEMS substrate assembly while maintaining measurement precision through careful positioning and thermal conductive adhesive bonding
Solution Approach 2:
The patent replaces the MEMS micro-electromechanical assembly process with simpler mechanical mounting techniques using thermal conductive adhesives, reducing device complexity and manufacturing cost while achieving the same measurement precision through alternative means
4Device complexity
If ambient temperature variations are not corrected, then device complexity is reduced, but measurement precision deteriorates due to thermal drift
Solution Approach 1:
The patent incorporates ambient temperature sensing and correction algorithms that continuously monitor and compensate for ambient temperature variations, using feedback from temperature measurements to adjust flow rate calculations and maintain measurement precision despite changing environmental conditions
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
This configuration enhances measuring sensitivity and stability by reducing thermal resistance and correcting for ambient temperature variations, resulting in accurate and consistent flow rate measurements.
Implementation Method 1
the fluid inside the piping is heated to a predetermined temperature by the heater 32
Implementation Method 2
the surface temperatures of the pipe 31 at the respective positions are measured by the temperature sensors 34a and 34b
Implementation Method 3
anchored on the piping with thermal conductive adhesives to minimize thermal resistance and heat loss
Implementation Method 4
thermal resistance issues caused by coating resins
Data Source
AI summary
A piping is anchored onto the lower faces of a heater chip and temperature sensor chips by using a thermal conductive adhesive. The heater chip and the temperature sensor chips are coated with a molding resin, and thermal resistance up to an element formed inside thereof is made smallest on a lower face side.