Sn-Cu Solder Alloy Composition for Continuous Casting Thickness Control

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Solution Overview

Problem

Existing solder alloys designed for flow soldering are not suitable for continuous casting due to differences in flowability and liquidus temperature requirements, leading to difficulties in obtaining a cast product with desired thickness and wettability issues with rotary molds.

Innovation Solution

Optimizing the content ranges of Cu, Ni, P, and Ge in the solder alloy to balance their interactions, ensuring the liquidus temperature and flowability are suitable for casting, with specific relations between these elements to achieve the desired viscosity and prevent oxidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If Sn-Cu based solder alloy is cast by continuous casting method in atmosphere, then the solder alloy can be produced efficiently, but oxidation of molten solder progresses and flowability decreases

Engineering Contradiction:

Improvecontinuous casting efficiencyVSAvoidoxidation of molten solder

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies inert atmosphere protection by conducting the continuous casting process in a controlled environment that prevents oxidation of the molten Sn-Cu solder alloy. This is achieved by limiting oxygen exposure during casting while maintaining the productivity benefits of continuous casting method.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Reliability

If Ni is added in amount equal to or more than specific amount to Sn-Cu solder alloy, then oxidation resistance is improved, but flowability of molten solder is impaired

Engineering Contradiction:

Improveoxidation resistanceVSAvoidflowability impairment

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the Ni content parameter within a specific range (0.01-0.4 mass%) to achieve the desired balance between oxidation resistance and flowability. By precisely controlling the Ni concentration, the patent maintains reliable oxidation protection while preserving adequate molten solder flowability for successful casting.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If P and Ge are added in large amounts to Sn-Cu solder alloy, then oxidation resistance is improved, but viscosity increases and flowability is impaired

Engineering Contradiction:

Improveoxidation resistanceVSAvoidviscosity increase

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent carefully controls the combined content of P and Ge within specific limits (P: 0.001-0.08 mass%, Ge: 0.001-0.08 mass%) to achieve oxidation resistance without excessive viscosity increase. This parameter optimization ensures that the molten solder maintains adequate flowability while gaining protection against oxidation during the casting process.

Inventive Principle:

Principle #35Parameter changes

4Strength

If Cu and Ni contents are increased in Sn-Cu-P-Ge-Ni solder alloy, then strength is improved, but liquidus temperature increases

Engineering Contradiction:

Improvesolder alloy strengthVSAvoidliquidus temperature

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent optimizes the Cu and Ni content parameters within specific ranges (Cu: 0.1-0.6 mass%, Ni: 0.01-0.4 mass%) to achieve the desired balance between strength and liquidus temperature. By controlling these compositional parameters, the patent ensures adequate mechanical strength while maintaining a liquidus temperature suitable for the casting process.

Inventive Principle:

Principle #35Parameter changes

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 optimized solder alloy composition allows for the production of cast products with a desired thickness and improved wettability, suitable for both continuous casting and fixed mold casting methods, ensuring consistent quality and performance.

Implementation Method 1

the oxidation of the molten solder progresses due to oxygen in the atmosphere... from the viewpoint of preventing the oxidation of the Sn-Cu based solder alloy

Methodology Applied

Scientific EffectOxidation prevention: Oxidation

Implementation Method 2

ensuring the liquidus temperature and flowability are suitable for casting, with specific relations between these elements to achieve the desired viscosity

Methodology Applied

Scientific EffectLiquidus temperature control:

Implementation Method 3

in a case where the Sn-Cu based solder alloy is cast as it is by the continuous casting method... the flowability of the molten solder decreases... wettability issues with rotary molds

Methodology Applied

Scientific EffectWetting: Wetting

Data Source

PatentEP3940096B1Solder alloy, cast product, formed product, and use of the cast product

Publication Date: 2024.10.23 SENJU METAL IND CO LTD

Figure 1~2

AI summary

Provided are a solder alloy with which it is possible to cast a cast article having a desired thickness, a cast article, a formed article, and a solder joint. The solder alloy has an alloy composition comprising, in terms of mass%, 0.1-2.0% of Cu, 0.01-0.4% of Ni, 0.001-0.08% of P, and 0.001-0.08% of Ge, the balance being Sn. The alloy composition satisfies expressions (1) to (3). Expression (1): (Cu + 5Ni) ≤ 0.945% Expression (2): (P + Ge) ≤ 0.15% Expression (3): 2.0 ≤ (Cu + 5Ni)/(P + Ge) ≤ 1000 In expressions (1) to (3), Cu, Ni, P, and Ge each represent component contents (in mass%) within the solder alloy.