Lead-Free Solder Alloy Composition for Low-Temperature Reflow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lead-free solder alloys face challenges in achieving a low melting point and excellent connection strength while maintaining cost-effectiveness, particularly in soldering processes requiring reduced reflow temperatures below 240°C.
Innovation Solution
A solder alloy composition comprising tin, silver, copper, bismuth, antimony, indium, and nickel, with specific content ratios and optional inclusion of cobalt, germanium, gallium, iron, or phosphorus, which is formulated to achieve a low melting point and enhanced connection strength, thereby improving workability and reducing damage to components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silver content is reduced to achieve cost reduction, then manufacturing cost decreases, but connection strength may deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content ratios of multiple alloying elements (silver: 0.05-0.2 mass%, copper: 0.1-1 mass%, nickel: 0.01-0.2 mass%, antimony: 0.01-2.5 mass%, bismuth: 0.01-4 mass%, indium: 0.005-2 mass%) to achieve both cost reduction and maintained connection strength. The specific compositional parameters resolve the contradiction by optimizing the balance between silver content (for strength) and other elements (for cost control).
Solution Approach 2:
The patent employs composite materials by creating a multi-element solder alloy system (Sn-Ag-Cu-Ni-Sb-Bi-In) where each element contributes specific properties. The composite nature of the alloy allows synergistic effects that maintain connection strength while reducing overall silver content, thus resolving the contradiction between cost and performance.
2Object-affected harmful factors
If reflow temperature is reduced below 240°C to suppress damage to members, then damage to members decreases, but connection strength may deteriorate
Solution Approach 1:
The patent uses parameter changes by adjusting the chemical composition parameters of the solder alloy to enable low-temperature soldering (below 240°C) while maintaining connection strength. The specific composition (particularly the balance of Bi, In, and other elements) lowers the melting point and allows effective soldering at reduced temperatures without sacrificing joint strength.
Solution Approach 2:
The patent exploits phase transitions by designing an alloy composition that undergoes controlled solidification and melting transitions at lower temperatures. The eutectic and near-eutectic composition enables a narrow solidification range and controlled phase transformation during cooling, which ensures strong connections even when soldering at reduced temperatures below 240°C.
3Strength
If multiple alloying elements are added to improve connection strength, then connection strength improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by establishing specific content ratio ranges for each alloying element (silver: 0.05-0.2 mass%, copper: 0.1-1 mass%, nickel: 0.01-0.2 mass%, etc.) that optimize connection strength while controlling manufacturing complexity. The defined parameter ranges provide clear manufacturing specifications that balance performance requirements with production feasibility.
Data Source
AI summary
In a solder alloy consisting essentially of tin, silver, copper, bismuth, antimony, indium, and nickel, the content ratio of the silver is 0.05 mass% or more and below 0.2 mass%; the content ratio of the copper is 0.1 mass% or more and 1 mass% or less; the content ratio of the bismuth is above 4.0 mass% and 10 mass% or less; the content ratio of the antimony is 0.005 mass% or more and 8 mass% or less; the content ratio of the indium is 0.005 mass% or more and 2 mass% or less; the content ratio of the nickel is 0.003 mass% or more and 0.4 mass% or less; and the content ratio of the tin is the remaining ratio and the mass ratio (Bi/Ni) of the bismuth content with respect to the nickel content is 35 or more and 1500 or less.