Over-current protection device
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Solution Overview
Problem
Small-sized over-current protection devices face challenges in maintaining low electrical resistivity while achieving excellent voltage endurance, as reducing the size or thickness of the PTC material layer increases electrical resistance and decreases voltage endurance, making them prone to burnout under high current and power conditions.
Innovation Solution
Incorporating a titanium-containing dielectric filler with a perovskite structure into the PTC composite material layer, which includes a fluoropolymer matrix and conductive filler, to enhance voltage endurance while maintaining low electrical resistivity, by dispersing the filler evenly to form an electrically conductive path and improve charge polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the top-view area or thickness of the PTC material layer is reduced to make the device smaller, then the device size is decreased, but the electrical resistance increases and voltage endurance capability is reduced
Solution Approach 1:
The patent uses a composite PTC material layer comprising fluoropolymer matrix, conductive filler (e.g., tungsten carbide, carbon black), and titanium-containing dielectric filler (e.g., BaTiO3, SrTiO3, CaTiO3) with perovskite structure. This composite structure enables the material to simultaneously achieve low electrical resistance and high voltage endurance capability, resolving the contradiction between device miniaturization and reliability.
Solution Approach 2:
The patent optimizes the volume percentage of titanium-containing dielectric filler (5-15%) and conductive filler (10-30%) within the PTC material layer to balance electrical resistance and voltage endurance properties, allowing small-sized devices to maintain high reliability.
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 results in an over-current protection device with electrical resistivity ranging from 0.0136 Ω·cm to 0.0211 Ω·cm and improved voltage endurance, capable of withstanding high currents and power without burnout, as demonstrated by the device's ability to pass a 100-cycle life test.
Implementation Method 1
by dispersing the filler evenly to form an electrically conductive path and improve charge polarization
Implementation Method 2
the conductive filler is dispersed in the polymer matrix, thereby forming an electrically conductive path in the PTC material layer
Implementation Method 3
the electrical resistance of conductive composite materials having a positive temperature coefficient (PTC) characteristic is very sensitive to temperature variation
Data Source
AI summary
An over-current protection device includes first and second electrode layers and a PTC material layer laminated therebetween. The PTC material layer includes a polymer matrix, a conductive filler, and a titanium-containing dielectric filler. The polymer matrix has a fluoropolymer. The titanium-containing dielectric filler has a compound represented by a general formula of MTiO3, wherein the M represents transition metal or alkaline earth metal. The total volume of the PTC material layer is calculated as 100%, and the titanium-containing dielectric filler accounts to for 5-15% by volume of the PTC material layer.