Composite Substrate Protection Device for High Current Applications
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Solution Overview
Problem
Existing protection devices for electronic apparatuses are inadequate for large current applications due to non-uniform heat transfer leading to cracking and are not suitable for over-voltage, over-current, and over-temperature protection beyond 70 A.
Innovation Solution
A modularized protection device with a composite substrate structure and a heat-conductive insulating layer between the heating and fusible elements, along with external electrodes of larger cross-sectional area, to ensure uniform heat dissipation and structural integrity, allowing for over-current, over-voltage, and over-temperature protection up to 300 A.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heating element is in direct contact with the substrate to transfer heat, then heat transfer efficiency is improved, but heat concentrates on a region of the substrate inducing cracking
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the heating element and the substrate. This layer has specific thermal conductivity properties that enable uniform heat distribution across the substrate surface, preventing localized heat concentration and cracking while maintaining effective heat transfer to the fusible element.
Solution Approach 2:
The patent modifies the thermal conductivity parameter of the insulating layer to optimize heat distribution. By carefully selecting materials and adjusting the thermal conductivity of the insulating layer, the system achieves uniform heat transfer across the substrate, resolving the contradiction between heat transfer efficiency and cracking prevention.
2Device complexity
If the low-melting metal layer connects to external electrodes through small cross-sectional areas, then device structure is simplified, but it is not suitable for large current applications
Solution Approach 1:
The patent segments the connection structure into multiple components: external electrodes with large cross-sectional areas for current entry/exit, intermediate connection layers, and the fusible element. This segmentation allows the external electrodes to handle large currents while the fusible element maintains its protective function, resolving the contradiction between structural simplicity and large current capability.
3Power
If the heating element generates large power to blow the fusible element, then over-voltage protection is achieved, but the heating element may be damaged due to non-uniform heat dissipation
Solution Approach 1:
The insulating layer acts as a thermal mediator that distributes the heat generated by the heating element uniformly across the substrate. This prevents localized overheating and damage to the heating element while enabling it to generate sufficient power to blow the fusible element when needed, resolving the contradiction between protection power and element durability.
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 enables reliable protection for large current applications by preventing cracking and extending the endurance of the heating element, reducing the power required to blow the fusible element, and maintaining structural integrity even if cracking occurs.
Implementation Method 1
current flows through the heating layer to generate heat to melt and blow the low-melting metal layer
Implementation Method 2
the insulating layer is disposed between the first planar substrate and the heating layer... the insulating layer has an area capable of uniformly dissipating the heat of the heating layer
Data Source
AI summary
A protection device comprises a first planar substrate, a second planar substrate, a heating element and a fusible element. The second planar substrate is attached to the underside of the first planar substrate to form a composite structure. The heating element comprises an insulating layer and a heating layer disposed thereon. The heating element is disposed on the first planar substrate, and the insulating layer is disposed between the first planar substrate and the heating layer. The fusible element is disposed above the heating element. The heating element heats up to blow the fusible element in the event of over-voltage or over-temperature.