Flexible PTC Sheet for Battery Overcurrent Protection
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Solution Overview
Problem
Existing PTC devices are too rigid due to their thickness, making them unsuitable for applications requiring flexible and malleable properties, such as overcurrent and overtemperature protection in batteries for cellular telephones and wearable electronic devices.
Innovation Solution
Development of an ultrathin, flexible sheet of PTC material with a thickness ranging from 10 μm to 100 μm, formed by a method involving a polymer resin and conductive filler dissolved in a solvent, applied as a uniform layer and optionally perforated to enhance flexibility, coupled with conductive foils for thermal and electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PTC materials with thickness of 200 μm or more are used, then the PTC device provides reliable overcurrent and overtemperature protection, but the device becomes too rigid for use in flexible electronic devices
Solution Approach 1:
The patent applies this principle by transitioning from conventional thick PTC devices to an ultrathin flexible PTC sheet with thickness of 10 μm to 100 μm. The thin film structure provides the necessary flexibility for integration into flexible electronic devices while maintaining the PTC protection function through the inherent temperature-dependent resistance characteristics of the PTC material layer.
Solution Approach 2:
The patent applies this principle by changing the thickness parameter of the PTC device from 200 μm or more to 10 μm to 100 μm. This parameter change fundamentally alters the mechanical properties (increasing flexibility) while preserving the electrical protection function through the PTC effect in the thin film structure.
2Adaptability or versatility
If the PTC device thickness is reduced to 10 μm to 100 μm, then the device becomes flexible and suitable for modern electronic devices, but conventional manufacturing methods cannot produce such thin layers
Solution Approach 1:
The patent applies this principle by replacing conventional mechanical manufacturing methods with a chemical solution-based approach. The PTC material is dissolved in a solvent to form an ink that can be deposited as a thin uniform layer, enabling production of ultrathin flexible PTC sheets that are incompatible with traditional mechanical cutting or molding processes.
Solution Approach 2:
The patent applies this principle by creating a composite structure consisting of PTC material particles suspended in a solvent matrix. This composite ink formulation enables the PTC material to be processed into thin flexible sheets while maintaining the electrical and thermal properties necessary for protection functionality.
3Adaptability or versatility
If the PTC sheet is perforated to enhance flexibility, then the device can be conformally wrapped around structures for enhanced surface area coverage, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies this principle by introducing perforations (holes) into the continuous PTC sheet structure. This segmentation creates a patterned structure that enhances flexibility and enables conformal wrapping around irregular surfaces while maintaining electrical connectivity through the remaining material bridges between perforations.
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 flexible PTC sheet provides effective overcurrent and overtemperature protection by increasing resistance at activation temperature, protecting batteries and loads while accommodating the flexible nature of modern electronic devices, and can be conformally wrapped around various structures for enhanced surface area coverage.
Implementation Method 1
PTC material in such devices is selected to have a relatively low resistance within a normal operating temperature range of the electronic, and a high resistance above the normal operating temperature of the electronic device. When the temperature of the PTC device reaches an 'activation temperature,' the resistance of the PTC device increases sharply.
Implementation Method 2
a method involving a polymer resin and conductive filler dissolved in a solvent, applied as a uniform layer
Implementation Method 3
coupled with conductive foils for thermal and electrical connectivity
Implementation Method 4
coupled with conductive foils for thermal and electrical connectivity
Data Source
AI summary
An electronic device including a protected component, a flexible positive temperature coefficient (PTC) device including a flexible sheet of PTC material coupled to a surface of the protected component, the flexible PTC device electrically connected to the protected component and adapted to arrest or mitigate electrical current flowing through the protected component upon the occurrence of an overcurrent condition, and a battery management system coupled to the flexible PTC device, the battery management system configured to measure a voltage across the flexible PTC device and to arrest or mitigate electrical current in the electronic device if the measured voltage across the flexible PTC device exceeds a predetermined threshold.