Bi-Cu Solder Wire Extrusion for Ductile Spool Winding
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Solution Overview
Problem
Conventional methods struggle to form solder wires with high ductility and thermal conductivity using bismuth-copper alloys due to brittleness, which prevents successful coiling onto spools without breaking.
Innovation Solution
The method involves extruding a bismuth-copper-gallium solder billet at 220-250°C and 12410-13445 kPa to form a wire with a diameter less than 1 mm, followed by heat treatment between 93-121°C to reduce extrusion stress, allowing the wire to be coiled onto a spool without breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bismuth-copper alloy is used to form solder wire, then thermal conductivity is improved, but brittleness increases making coiling impossible
Solution Approach 1:
The patent applies parameter changes by controlling the extrusion temperature (200-300°C) and pressure (1000-2000 psi) to transform the physical state of the bismuth-copper alloy during processing. This temperature and pressure control allows the brittle alloy to be extruded into wire form without shattering, and subsequent heat treatment at 93-121°C modifies the microstructure to reduce brittleness and enable coiling while preserving thermal conductivity
Solution Approach 2:
The patent creates a composite structure by forming a metal matrix composite during extrusion, where the controlled pressure and temperature create a refined microstructure with dispersed phases. This composite approach at the microstructural level allows the material to maintain the high thermal conductivity of bismuth-copper alloy while developing improved ductility through the heat treatment process
2Length of moving object
If extrusion pressure is increased to form thin wire, then wire diameter is reduced, but internal stress increases causing wire to break during coiling
Solution Approach 1:
The patent applies preliminary action by performing heat treatment at 93-121°C immediately after extrusion and before coiling operations. This pre-treatment removes internal stresses generated during high-pressure extrusion, preventing wire breakage during subsequent coiling while maintaining the achieved thin wire diameter
Solution Approach 2:
The patent uses parameter changes by transitioning from high pressure (1000-2000 psi) during extrusion to low temperature (93-121°C) heat treatment, then to ambient conditions for coiling. This parameter sequencing reduces internal stress at the critical coiling stage while maintaining dimensional control of the thin wire
3Strength
If extrusion temperature is increased to improve ductility, then wire formability is improved, but material properties deteriorate
Solution Approach 1:
The patent applies precise parameter changes by limiting extrusion temperature to 200-300°C and subsequent heat treatment to 93-121°C. This controlled temperature range provides sufficient ductility for forming while preventing excessive grain growth or phase transformations that would deteriorate material properties, achieving optimal balance through parameter optimization
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 process results in a solder wire with improved ductility and manufacturability, enabling successful coiling and maintaining desired thermal conductivity and melting properties.
Implementation Method 1
extruding a billet at a temperature of from 220 °C to 250 °C and a pressure of from 12410 kPa to 13445 kPa (1800 psi to 1940 psi) to form a solder wire having a diameter of less than 1 millimeter
Implementation Method 2
heat treating the extruded wire at a temperature of between 93 °C and 121°C
Implementation Method 3
heat treating the extruded wire at a temperature of between 93 °C and 121°C to reduce extrusion stress
Implementation Method 4
maintaining desired thermal conductivity
Data Source
Figure 1~2
AI summary
A solder wire composition may include 85 to 95 weight percent bismuth, and at least 5 weight percent copper. The solder wire composition may have a diameter of less than about 1 millimeter, and an elongation at break of at least 20%.