Thermistor Metal Base Split Electrodes Reflow Mounting
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Solution Overview
Problem
Existing thermistors face challenges in minimal space mounting due to wire bonding requirements, high production costs, and susceptibility to cracking, which affects their temperature sensing accuracy and reliability.
Innovation Solution
A thermistor design featuring a metal base material and a thermistor thin film layer with split electrodes, where the metal base material and thermistor thin film layer are laminated and fired integrally, allowing for reflow soldering and reduced height, flexibility, and cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wire bonding is used for electrical connection to the electrode film, then electrical connection is achieved, but mounting on minimal space (150 to 200 μm) is not possible
Solution Approach 1:
The electrode is divided into two separate electrodes formed directly on the metal substrate surface, eliminating the need for wire bonding. This segmentation allows direct mounting on minimal spaces while maintaining electrical connection capability
Solution Approach 2:
The metal substrate serves dual functions as both the structural base and one of the electrodes, eliminating the need for separate electrode films and wire bonding processes, enabling mounting in minimal spaces
2Ease of manufacture
If gas phase method (sputtering) is used to form the themosensitive resistor film, then the film is formed, but production cost increases and productivity decreases
Solution Approach 1:
The gas phase sputtering method is replaced with a solid phase firing process using ceramic slurry and metal powder paste, eliminating complex vacuum equipment and gas phase reactions, thereby reducing production cost and improving productivity while maintaining film quality
Solution Approach 2:
The manufacturing approach changes from gas phase deposition to solid phase firing, altering the physical state and processing parameters to achieve cost-effective production without compromising film formation quality
3Reliability
If the thermistor structure uses a plate-like metal substrate with electrode film, then electrical connection is established, but cracking occurs in the metal substrate or themosensitive resistor film causing resistance fluctuation
Solution Approach 1:
The structure uses a composite of metal powder paste and ceramic slurry fired together, creating an integrated material system with matched thermal expansion coefficients, preventing cracking and resistance fluctuation while maintaining reliability
Solution Approach 2:
The metal substrate and themosensitive resistor film are merged into a single integrally fired structure, eliminating interface cracks and improving crack resistance, thereby ensuring stable resistance characteristics
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
Enables mounting on minimal spaces without cracking, maintains electrical characteristics under stress, and reduces production costs while ensuring reliability and accuracy as a temperature sensor.
Implementation Method 1
the sheet-shaped metal base material and the sheet-shaped thermistor thin film layer are fired in an integrally laminated state
Implementation Method 2
a themosensitive resistor film formed on one surface of the plate-like metal substrate
Data Source
Figure 1(A)~3
Figure 4(A)~4(E)
Figure 6~7
AI summary
To obtain a method for manufacturing a thermistor which allows a reduction in the height or mounting by reflow, which can be mounted on a minute space, which can be manufactured at a low cost, and in which the occurrence of cracking can be suppressed as much as possible. An NTC thermistor has a metal base material (11), a thermistor thin film layer (15) formed on the metal base material (11), and a pair of split electrodes (21) and (22) formed on the thermistor thin film layer (15). A ceramic slurry is applied onto a carrier film to form the thermistor thin film layer (15), a metal powder containing paste is applied onto the thermistor thin film layer (15) to form the metal base material (11), and further an electrode paste is applied onto the metal base material (11) to form the split electrodes (21) and (22). Thereafter, the three substances are integrally fired.