Copper And Brass Inner And Outer Caps Of Fuses: Material Properties, Industry Trends, And Technological Innovation

 

As the core component of circuit protection, the choice of inner and outer cap materials of fuses directly affects the reliability and life of the product. Copper Cap (pure copper) and Brass Inner Cap (copper-zinc alloy) are the current mainstream inner and outer cap materials, and there are significant differences between the two in terms of conductivity, mechanical strength, corrosion resistance, and cost.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Advantages of copper:
Copper has excellent electrical conductivity (electrical conductivity of about 58 MS/m) and thermal conductivity (thermal conductivity coefficient of 386.4 W/m·K), and is a good conductor second only to silver. Its high purity characteristics (copper content ≥99.9%) make it perform well in high-frequency circuits, and it has good ductility and is easy to cold-punch and stretch. For example, in high-voltage fuses for new energy vehicles, copper contacts can effectively reduce temperature rise and improve safety. In addition, Copper Stop End has strong corrosion resistance, especially in dry environments, and is not easy to oxidize, making it suitable for precision electronic equipment.

 

Features of brass:
Brass is composed of copper and zinc (the zinc content is usually 30%-40%), and its mechanical strength (tensile strength of about 300 MPa) and hardness (Brinell hardness of about 80 HB) are significantly higher than copper, and its cost is 15%-20% lower. For example, in fuses in the field of industrial control, the brass outer cap can withstand greater mechanical stress and avoid loosening due to vibration. In addition, brass has better corrosion resistance in sulfur-containing environments and is often used in outdoor or high-humidity scenarios.

 

Performance shortcomings:
Copper has a low hardness (about 35 HB), is prone to wear after long-term use, and has a high melting point (1083℃), and strict welding process requirements. The conductivity of the Brass Pipe End Cap is only 1/5 of that of copper (about 11 MS/m), which may cause heating problems in high-current scenarios. In addition, when the zinc content of brass exceeds 39%, it is prone to "season cracking", which needs to be improved by heat treatment or adding trace alloy elements (such as tin and aluminum).

 

 

 

Environmental protection regulations promote material innovation:
With the implementation of the EU RoHS Directive and China's "Management Measures for the Restriction of the Use of Hazardous Substances in Electrical and Electronic Products", the fuse industry has accelerated the elimination of lead-containing materials. For example, lead-free Brass End Cap (such as CuZn39Pb3 alternative materials) and nickel-tin plating are becoming increasingly popular, while the application of bio-based plastic shells (containing 30% plant fibers) can achieve 90% component recycling. In addition, the high recycling rate of Copper End Cap (about 95%) makes it more advantageous in the circular economy.

 

Intelligent and miniaturized demand:
The rapid development of new energy vehicles, photovoltaic energy storage, and other fields has put forward higher requirements for fuses. For example, smart fuses integrate temperature sensors and communication modules, which can transmit real-time current data via Bluetooth to achieve predictive maintenance. In terms of material selection, Copper Tube Cap is the first choice for high-frequency signal transmission due to its high conductivity, while brass improves contact reliability through surface gold plating processes (such as chemical nickel plating + immersion gold).

 

Exploration of emerging materials:
The industry is developing high-performance composite materials to replace traditional copper materials. In addition, the copper-graphene composite melt can increase the breaking efficiency by 50%, while the response time of liquid metal (such as gallium-based alloy) fuses are shortened to microseconds.