Sn-Cu-Ni-Ge Solder Alloy Composition for Bridge and Dross Suppression
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Solution Overview
Problem
Existing solder alloys for electronic devices face challenges in minimizing solder bridges, solder icicles, Cu leaching, and dross generation, while maintaining mechanical strength and controlling liquidus and solidus temperature differences, which are critical for modern miniaturized electronic components.
Innovation Solution
A solder alloy composition with specific ranges of Cu (2.0-3.0%), Ni (0.010-0.30%), and Ge (0.0010-0.20%) is developed, with the balance being Sn, to achieve a narrow temperature difference, suppress solder bridges and icicles, reduce dross, and enhance strength, avoiding the use of P, Ga, and Co to maintain stability and control viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If terminals remain in molten solder for a long time during dip soldering and flow soldering, then soldering process is completed, but Cu leaching occurs and dross is generated
Solution Approach 1:
The patent modifies the chemical composition parameters of the solder alloy by adding Ge (0.003-0.5 mass%) to the Sn-Cu-Ni base alloy. This compositional change alters the chemical reactivity of the molten solder, suppressing Cu leaching from terminals and reducing dross generation during prolonged immersion, while maintaining effective soldering.
Solution Approach 2:
The invention creates a multi-element composite solder alloy (Sn-Cu-Ni-Ge) that combines the benefits of each element: Sn provides base soldering properties, Cu enhances strength, Ni suppresses oxidation, and Ge further reduces Cu leaching and dross. The synergistic interaction of these elements resolves the contradiction between completing soldering and preventing harmful effects.
2Strength
If solder alloy contains higher Cu content to improve strength, then mechanical strength increases, but liquidus temperature increases and solder bridges occur
Solution Approach 1:
The patent optimizes the Cu content parameter to a specific range (1.0-3.0 mass%) and introduces Ge as a modifying element. This parameter control prevents excessive liquidus temperature elevation while maintaining sufficient strength. The Ge addition further refines the temperature-composition relationship to avoid solder bridges.
Solution Approach 2:
The invention applies different functional roles to different elements in the alloy: Cu provides strength enhancement in a controlled amount, while Ge specifically addresses the temperature issue by suppressing liquidus elevation and solder bridge formation. Each element targets a specific property need.
3Reliability
If solder alloy contains P or Ga to suppress oxidation, then oxidation resistance improves, but viscosity control becomes difficult and manufacturing complexity increases
Solution Approach 1:
The patent removes P and Ga from the alloy composition despite their oxidation suppression capabilities. Instead, it relies on Ni (0.003-0.5 mass%) and Ge (0.003-0.5 mass%) to provide oxidation resistance through more manageable mechanisms that do not interfere with viscosity control or require complex manufacturing processes.
4Reliability
If Ge content is increased to suppress oxide coating film generation, then oxidation suppression improves, but alloy composition control becomes more difficult
Solution Approach 1:
The patent establishes a balanced Ge content range (0.003-0.5 mass%) that provides sufficient oxidation suppression through oxide film formation on the solder surface, while maintaining controllable alloy composition and avoiding excessive complexity in manufacturing and quality control.
Data Source
AI summary
Provided are a solder alloy and a solder joint, which have a narrow ΔT to suppress solder bridges and solder icicles, and a small amount of dross generated in a solder tank, suppress Cu leaching, and have higher strength. The solder alloy has an alloy composition of, by mass %, Cu: more than 2.0% and less than 3.0%; Ni: 0.010% or more and less than 0.30%; and Ge: 0.0010 to 0.20% with the balance being Sn. Preferably, by mass %, Cu is more than 2.5% and less than 3.0%, and the alloy composition satisfies the following relations (1) and (2): 2.400≤Cu+Ni+Ge≤3.190 (1), and 0.33≤Ge/Ni≤1.04 (2). Cu, Ni, and Ge in the relations (1) and (2) each represent the contents (mass %) in the alloy composition.