Sn-Cu Solder Alloy Casting With Ultrasonic Grain Refinement
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Solution Overview
Problem
The continuous casting of Sn-Cu based solder alloys is prone to cracking and breakage due to the formation of coarse intermetallic compounds, which complicates the manufacturing process and increases the risk of breakage during transportation, especially when the Cu content is high, leading to inefficiencies in the casting process and product quality.
Innovation Solution
Applying micro-vibrations, such as ultrasonic waves, during the continuous casting of Sn-Cu solder alloys with a Cu content of 0.8% or more, while maintaining the rotary mold in a horizontal state, to improve the fluidity of the molten solder and reduce the maximum grain size of intermetallic compounds, thereby preventing cracking and breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the continuous casting method is used to manufacture Sn-Cu based solder alloy, then productivity is improved, but coarse intermetallic compounds are generated during solidification causing cracking and breakage
Solution Approach 1:
The patent applies ultrasonic vibration to the molten solder during continuous casting to prevent the formation of coarse intermetallic compounds. The vibration disrupts the solidification process, preventing grain coarsening and intermetallic compound aggregation, thereby eliminating cracking and breakage while maintaining continuous casting productivity
Solution Approach 2:
The patent changes the solidification parameters by applying ultrasonic vibration energy to the molten solder. This alters the cooling rate and nucleation conditions during solidification, transforming the microstructure from coarse intermetallic compounds to fine-grained structure, thus preventing cracking while maintaining continuous casting efficiency
2Ease of manufacture
If high Cu content (0.8% or more) is used in Sn-Cu based solder alloy, then melting point is reduced and ease of manufacture is improved, but coarse intermetallic compounds are generated causing cracking
Solution Approach 1:
Ultrasonic vibration is applied during solidification to prevent the growth of intermetallic compound grains even when high Cu content is present. The vibration energy disrupts the normal solidification process, preventing coarse grain formation that would otherwise occur with high Cu content alloys, thus maintaining manufacturing precision while benefiting from lower melting point
Solution Approach 2:
The patent changes the solidification dynamics by introducing ultrasonic vibration, which modifies how high Cu content alloys solidify. This parameter change prevents the formation of coarse intermetallic compounds that typically occur with high Cu content, allowing the alloy to maintain both ease of manufacture and manufacturing precision
3Manufacturing precision
If cooling rate is increased to refine eutectic structure, then manufacturing precision is improved, but manufacturing complexity increases due to mold cooling requirements
Solution Approach 1:
The patent replaces complex cooling systems with ultrasonic vibration to achieve fine eutectic structure. The vibration directly refines the microstructure during solidification without requiring complex mold cooling arrangements, thus improving manufacturing precision while reducing device complexity
Solution Approach 2:
The patent substitutes the thermal cooling mechanism with mechanical ultrasonic vibration to achieve microstructure refinement. Instead of relying on complex cooling water circulation systems, the ultrasonic vibration directly controls solidification, simplifying the manufacturing system while maintaining or improving eutectic structure refinement
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 approach results in a continuous cast product with improved quality, reduced breakage risk, and enhanced continuous castability, as evidenced by the small maximum grain size and low area ratio of intermetallic compounds, allowing for longer, unbroken cast products and improved workability.
Implementation Method 1
Applying micro-vibrations, such as ultrasonic waves, during the continuous casting of Sn-Cu solder alloys
Data Source
Figure 1
Figure 2(a)~2(b)
AI summary
Provided is a solder alloy having superior continuous casting performance. The solder alloy of the present invention has an alloy composition, by mass%, of Cu: 0.8 to 10%, the remainder being Sn, and includes an intermetallic compound. In a region with a thickness of more than or equal to 50 µm from a surface of the solder alloy, the intermetallic compound has a maximum crystal grain size of not more than 100 µm.