SnBi Solder Wire Single-Crystal Production
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Solution Overview
Problem
Tin-bismuth soldering wires are difficult to produce in continuous form due to expansion anomalies and lack of ductility, making it challenging to create thin or flux-filled wires using conventional methods.
Innovation Solution
A method involving the formation of a substantially single crystal stud from the SnBi alloy, which is then formed into a solder wire through cold forming and drawing, allowing for improved cold-forming properties and reproducible mechanical processing without material tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional continuous casting methods are used for SnBi alloy, then production efficiency is maintained, but the alloy expands on cooling causing the strand to break off
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate and temperature gradient during solidification to manage the density anomaly of SnBi alloy. By adjusting these thermal parameters, the alloy can solidify without expanding abnormally, preventing strand breakage while maintaining continuous production capability.
Solution Approach 2:
The invention employs preliminary action by pre-heating the mold and controlling the initial solidification conditions before the main casting process. This preliminary thermal treatment prepares the system to handle the density anomaly, allowing continuous casting to proceed without strand breakage.
2Ease of manufacture
If cold forming and drawing processes are applied to SnBi alloy, then thin solid wires or flux-filled wires can be produced, but the lack of ductility makes it almost impossible to produce these products
Solution Approach 1:
The patent changes the microstructural parameters of SnBi alloy through controlled solidification and heat treatment processes. These parameter changes transform the material's ductility characteristics, enabling successful cold forming and drawing operations that would otherwise be impossible due to the alloy's inherent brittleness.
Solution Approach 2:
The invention creates a composite structure within the SnBi alloy through controlled solidification, producing a microstructure that combines the low melting point properties of SnBi with enhanced ductility. This composite microstructure enables both cold-forming capability and adequate strength for wire production.
3Temperature
If SnBi alloy is used as lead-free solder, then low melting temperature and high strength are achieved, but the alloy cannot be produced using conventional methods due to expansion on cooling
Solution Approach 1:
The patent applies parameter changes to the solidification process, specifically controlling cooling rates and temperature gradients, to eliminate the expansion anomaly that prevents conventional manufacturing. This allows SnBi alloy to be produced using standard industrial casting methods while retaining its desirable low melting temperature and high strength properties.
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
This method enables the production of SnBi soldering wires with enhanced workability and ductility, allowing for the creation of thin, flux-filled wires with improved mechanical properties and consistent quality.
Implementation Method 1
the solder alloy is at least partially melted and recrystallized
Implementation Method 2
the solder alloy is at least partially melted and recrystallized
Implementation Method 3
the alloy expands on cooling due to a density anomaly
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a method for producing a drawable solder wire, in particular an SnBi solder wire, wherein the method comprises the following steps: providing a solder alloy, forming a substantially single-crystal ingot from the solder alloy, wherein the solder alloy is at least partially melted and recrystallized, and forming a solder wire from the substantially single-crystal ingot. The present invention further relates to a drawable solder wire, in particular an SnBi solder wire, and to an apparatus for producing a drawable solder wire, in particular an SnBi solder wire.