Surface-Mountable PTC Over-Current Protection Device with Insulating Notches
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Solution Overview
Problem
Surface-mountable over-current protection devices struggle to withstand high voltages due to potential electric arcs and inadequate insulation, leading to safety issues and reduced reliability, especially in high-voltage applications like automotive and communication systems.
Innovation Solution
The design incorporates insulating members between the PTC material layer and conductive members, using insulating resin with specific viscosity and CTE to prevent direct contact and enhance electrical insulation, along with a laminated structure with varying conductive layer thicknesses and electroplated metal layers to improve voltage endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating members are added between PTC material layer and conductive members, then voltage endurance and anti-arc ability are improved, but device complexity increases
Solution Approach 1:
Insulating members (insulating resin blocks) are introduced as intermediary elements between the PTC material layer and conductive members (conductive through holes). These insulating blocks prevent direct contact and potential electric arcs, while still allowing electrical connection through the conductive members to reach the PTC material. This mediator approach resolves the contradiction by adding a protective layer that improves voltage endurance without completely isolating the electrical path.
Solution Approach 2:
The insulating structure is segmented into multiple insulating blocks positioned at specific locations where conductive through holes contact the PTC material layer. Rather than using a continuous insulating layer that would block all electrical connection, the insulation is divided into discrete segments that provide anti-arc protection only at critical contact points while maintaining electrical connectivity elsewhere.
2Ease of manufacture
If the PTC material layer is in direct contact with conductive through holes, then manufacturing is simplified, but electric arcs may occur causing safety issues
Solution Approach 1:
Insulating blocks serve as intermediary elements inserted between the conductive through holes and the PTC material layer at contact points. This prevents direct contact that causes electric arcs, while the conductive members still extend through the insulating blocks to establish electrical connection. The mediator approach eliminates the harmful electric arc effect while preserving the simplified manufacturing advantage of using through holes.
3Reliability
If conductive filler amount is decreased for high voltage applications, then voltage endurance is improved, but hold current decreases
Solution Approach 1:
The device structure is segmented into regions with different conductive filler concentrations. The PTC material layer can maintain higher conductive filler content for adequate hold current, while insulating blocks are strategically placed at high-voltage stress points (where conductive through holes contact the PTC layer) to provide localized voltage protection. This spatial segmentation allows simultaneous optimization of both hold current and voltage endurance.
Solution Approach 2:
Different parts of the device have different insulation requirements. The insulating blocks provide enhanced insulation quality specifically at critical contact points between conductive members and PTC material, while other regions maintain their original design for optimal electrical performance. This local quality approach allows high hold current in bulk material while providing voltage protection where needed.
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 significantly increases the device's ability to withstand high voltages, reducing the risk of electric arcs and enhancing reliability, allowing for higher hold currents and improved performance in high-voltage environments.
Implementation Method 1
The left insulating member is disposed in the left notch and between the left conductive member and the PTC material layer for isolation. The right insulating member is disposed in the right notch and between the right conductive member and the PTC material layer for isolation.
Implementation Method 2
The resistive material has positive temperature coefficient (PTC) characteristic; that is, the resistance of the PTC material remains extremely low at a normal temperature; however when an over-current or an over-temperature occurs in the circuit, the resistance instantaneously increases to a high resistance state
Implementation Method 3
The first conductive layer comprises a primary portion disposed on an upper surface of the PTC material layer and a secondary portion extending over the left notch. The second conductive layer comprises a primary portion disposed on a lower surface of the PTC material layer and a secondary portion extending over the underside of the right notch.
Data Source
AI summary
A surface mountable over-current protection device comprises a PTC material layer, first and second conductive layers, left and right electrodes, left and right conductive members, and left and right insulating members. The PTC material layer comprises a left notch at a left end and a right notch at a right end. The first conductive layer comprises a primary portion disposed on an upper surface of the PTC material layer and a secondary portion extending over the left notch, and the second conductive layer comprises a primary portion disposed on a lower surface of the PTC material layer and a secondary portion extending over the underside of the right notch. The left conductive member connects to the left electrode and the first conductive layer and isolates from the second conductive layer. The right conductive member connects to the right electrode and the second conductive layer and isolates from the first conductive layer. The left and right insulating members are disposed in the left and right notches, respectively. The PTC material layer is not in direct contact with the left and right conductive members, and the primary portion and the secondary portion of the first or second conductive layer have different thicknesses.