Insertable PPTC Device with Porous Matrix for High-Voltage Endurability
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Solution Overview
Problem
Existing over-current protection devices face challenges in enhancing high-voltage endurability without increasing device size, which affects their reliability and electrical properties.
Innovation Solution
An insertable PPTC over-current protection device is designed with first and second electrodes, conductive lead pins, and a PTC polymer matrix with at least one hole to accommodate thermal expansion, preventing structural deformation and improving high-voltage endurability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area or thickness of the PTC element is increased to enhance high-voltage endurability, then the high-voltage endurability is improved, but the size of the over-current protection device is undesirably increased
Solution Approach 1:
The PTC polymer matrix is designed with a porous structure containing multiple voids distributed throughout its volume. These voids allow the polymer to expand during thermal runaway without increasing the overall device dimensions, while simultaneously providing pathways for stress relief and improving high-voltage endurability through enhanced charge distribution.
Solution Approach 2:
The patent introduces voids at specific locations within the PTC polymer matrix to create localized expansion zones. This allows the bulk of the device to maintain its compact size while specific regions accommodate thermal expansion, resolving the contradiction between small size and high-voltage endurability.
2Reliability
If the PTC polymer matrix is made thicker to improve high-voltage endurability, then the electrical properties are enhanced, but the device size increases
Solution Approach 1:
By incorporating voids within the PTC polymer matrix, the patent achieves improved electrical properties and high-voltage endurability without increasing the physical thickness of the matrix. The voids provide internal space for stress accommodation and charge distribution, enhancing electrical performance while maintaining a thin profile.
Solution Approach 2:
Instead of improving electrical properties by increasing thickness in one dimension, the patent uses voids distributed throughout the matrix volume to provide three-dimensional pathways for stress relief and charge distribution, achieving enhanced electrical properties without increasing the dominant dimension.
3Volume of moving object
If the PTC polymer matrix is constrained without expansion space, then the device size is minimized, but structural deformation occurs during thermal expansion
Solution Approach 1:
The porous structure with distributed voids provides internal expansion space within the compact PTC polymer matrix. During thermal runaway, the polymer can expand into these voids, maintaining structural integrity and preventing deformation while keeping the overall device size minimal.
Solution Approach 2:
The voids are pre-formed within the PTC polymer matrix before assembly, creating advance cushioning spaces that accommodate thermal expansion during operation. This prevents structural deformation by providing predetermined expansion pathways, maintaining both compact size and structural stability.
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 device achieves improved high-voltage endurability and reliability by allowing thermal expansion without increasing device size, as demonstrated by switching cycle and thermal runaway tests.
Implementation Method 1
having an effective volume to accommodate thermal expansion of the PTC polymer matrix when temperature of the PTC polymer matrix is increased
Data Source
AI summary
An insertable PPTC over-current protection device includes: first and second electrodes; a solder material; conductive lead pins bonded to the first and second electrodes, respectively, each of the lead pins having a connecting segment extending along and bonded to an outer surface of the respective one of the first and second electrodes through the solder material, and a free segment extending outwardly from the connecting segment beyond a peripheral edge of the respective one of the first and second electrodes; and a PTC polymer matrix laminated between the first and second electrodes. The PTC polymer matrix is formed with at least one hole that has an effective volume to accommodate thermal expansion of the PTC polymer matrix.