Laminated Fuse Element for Reflow Compatibility and High-Speed Blowout
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Solution Overview
Problem
Existing fuse elements face challenges with surface mounting using reflow, low current ratings, and maintaining high-speed blowout properties, particularly due to limitations with lead-containing solders under the RoHS directive.
Innovation Solution
A fuse element with a laminated structure comprising a low melting point metal layer and a high melting point metal layer, where the low melting point metal layer erodes the high melting point metal layer to achieve rapid blowout, allowing for increased current ratings and reflow compatibility without using lead-containing solders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low melting point solder is used in the fuse element, then surface mounting using reflow becomes possible, but the fuse element blows during reflow process
Solution Approach 1:
The fuse element is segmented into multiple functional layers: a low melting point metal layer (for reflow compatibility and blowout function) and a high melting point metal layer (for structural support during reflow). This segmentation allows each layer to perform its specific function without interfering with the other, enabling surface mounting while preventing premature blowout during reflow process.
Solution Approach 2:
The invention uses a composite structure combining metals with different melting points. The low melting point metal (e.g., Sn, Pb, or their alloys) provides reflow compatibility and blowout functionality, while the high melting point metal (e.g., Ag, Cu, or their alloys) provides structural stability during reflow. This composite material approach resolves the contradiction between reflow compatibility and blowout prevention.
2Quantity of substance
If the fuse element size is increased to raise current rating, then higher current ratings are achieved, but the blowout speed decreases
Solution Approach 1:
The fuse element employs local quality differentiation through its layered structure. The low melting point metal layer is strategically positioned to provide rapid melting and erosion characteristics, ensuring fast blowout speed. Meanwhile, the overall element size and cross-sectional area are optimized to achieve the required current rating. This local quality approach allows the fuse to maintain high blowout speed despite increased size for higher current ratings.
Solution Approach 2:
The invention changes the physical parameters of the fuse element by using metals with different melting points and controlling their layer thicknesses. The low melting point metal layer melts rapidly at相对较低 temperatures, creating a fast blowout response. By adjusting the thickness and material composition parameters, the fuse achieves both high current rating capability and rapid blowout performance simultaneously.
3Reliability
If a high melting point Pb-containing solder is used to maintain blowout property, then blowout property is maintained, but surface mounting using reflow becomes impossible and RoHS compliance is violated
Solution Approach 1:
The fuse element is segmented into multiple functional layers: a low melting point metal layer (for reflow compatibility and blowout function) and a high melting point metal layer (for structural support during reflow). This segmentation allows each layer to perform its specific function without interfering with the other, enabling surface mounting while preventing premature blowout during reflow process.
Solution Approach 2:
The invention uses a composite structure combining metals with different melting points. The low melting point metal (e.g., Sn, Pb, or their alloys) provides reflow compatibility and blowout functionality, while the high melting point metal (e.g., Ag, Cu, or their alloys) provides structural stability during reflow. This composite material approach resolves the contradiction between reflow compatibility and blowout prevention.
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 fuse element efficiently supports surface mounting and high-speed blowout while maintaining high current ratings, improving pulse tolerance and surge resistibility, and allowing for thinner designs compared to conventional chip fuses.
Implementation Method 1
the low melting point metal layer erodes the high melting point metal layer and blowout occurs when the current flows
Implementation Method 2
the low melting point metal layer erodes the high melting point metal layer
Implementation Method 3
self-generated heat caused by a rate-exceeding current flowing therethrough causes blowout of the fuse element
Data Source
AI summary
A fuse element capable of surface-mounting and capable of increased ratings while maintaining high-speed blowout property; and a fuse device using the same. A fuse element blown by self-generated heat caused when a rate-exceeding current flows therethrough constitutes a current path of a fuse device and has a low melting point metal layer and a high melting point metal layer laminated onto the low melting point metal layer; when the current flows therethrough, the low melting point metal layer erodes the high melting point metal layer and blowout occurs.