Copper-Tin Brazing Wire Composition for Low-Melt, Low-Brittleness Joining
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Solution Overview
Problem
Copper-tin brazing materials with high tin content suffer from brittleness and high melting points, causing thermal damage to base materials during brazing, and existing solutions fail to balance melting temperature and processability effectively.
Innovation Solution
A copper-tin brazing wire with a composite metal layer containing Cu, Sn, and P, where the mass ratio of Cu, Sn, and P is (45-55):(46-56):(0.5-1.5), is developed, using ultra-fine copper wires coated with a mixed molten liquid of Cu, Sn, and P, which are then twisted into a strand to achieve high alloying degree, compositional uniformity, low brittleness, and a reduced liquidus melting temperature of 800°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the tin content in copper-tin brazing material is increased to reduce melting temperature, then the liquidus melting temperature decreases, but the brittleness of the brazing material significantly increases and processability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the tin content within 18-25 wt% and phosphorus content within 0.05-1.5 wt%, rather than using high tin content alone. This optimized composition range achieves liquidus temperature below 850°C while maintaining acceptable brittleness levels. The multi-parameter optimization resolves the contradiction between lowering melting point and controlling brittleness.
Solution Approach 2:
The patent creates a composite brazing material system combining copper, tin, and phosphorus in specific proportions. The phosphorus acts as a modifying element that forms intermetallic compounds and alters the microstructure, creating a composite effect that reduces melting temperature while simultaneously improving ductility and reducing brittleness, thus resolving the trade-off between temperature reduction and mechanical property maintenance.
2Temperature
If the tin content is increased to achieve low melting point, then the brazing temperature can be reduced, but the processability and formability of the brazing material significantly deteriorate
Solution Approach 1:
The patent optimizes multiple compositional parameters simultaneously: copper content (73.5-79.5 wt%), tin content (18-25 wt%), and phosphorus content (0.05-1.5 wt%). This multi-parameter optimization achieves brazing temperature below 850°C while maintaining sufficient processability and formability, resolving the contradiction between low temperature requirement and manufacturing ease.
Solution Approach 2:
The patent introduces phosphorus as a localized modifying element that specifically affects the eutectic structure and liquidus temperature without significantly impacting overall formability. The phosphorus concentrates at specific microstructural locations to lower melting point while the bulk material maintains good processability, thus resolving the local contradiction between temperature reduction and manufacturing ease.
3Ease of operation
If existing copper-tin brazing material BCu88Sn is used, then the material is available and easy to use, but the melting point is high (825-990°C) causing thermal damage to base material
Solution Approach 1:
The patent modifies the compositional parameters of conventional copper-tin brazing material by adding controlled amounts of phosphorus (0.05-1.5 wt%) and adjusting the Sn content to 18-25 wt%. This parameter modification reduces the liquidus temperature to below 850°C, eliminating thermal damage to base materials while maintaining ease of operation and usability similar to conventional materials.
Solution Approach 2:
The patent introduces phosphorus as an intermediary element that mediates between the copper and tin phases, forming a eutectic system with lower melting point. This intermediary phosphorus enables the brazing material to operate at lower temperatures (below 850°C) without compromising ease of use, thus resolving the contradiction between reducing thermal damage and maintaining operational simplicity.
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 copper-tin brazing wire exhibits improved processability, reduced brittleness, and lower melting points, ensuring better wetting performance and joint strength without thermal damage to base materials, while maintaining a high Sn content and alloying degree.
Implementation Method 1
a plurality of ultra-fine copper wires as a base undergo a high-temperature alloying reaction with a composite metal layer containing Cu, Sn, and P in a certain proportion to form multiple ultra-fine brazing wires
Implementation Method 2
coating a mixed molten liquid of Cu, Sn, and P on surfaces of copper wires
Implementation Method 3
twisting the coated copper wires into one strand to obtain the copper-tin brazing wire
Data Source
AI summary
A copper-tin brazing wire and a preparation method and use thereof are provided. A copper-tin brazing wire includes a plurality of copper wires each having a composite metal layer on a surface thereof; the copper-tin brazing wire includes, in parts by weight, 75-84 parts of Cu, 20-25 parts of Sn, and 0.4-0.5 parts of P; and the composite metal layer includes Cu, Sn, and P, in which a mass ratio of Cu, Sn, and P is (45-55):(46-56):(0.5-1.5).