Solder Alloy Composition for Stable Paste Viscosity and Wettability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solder pastes face challenges in maintaining stable viscosity and wettability over time, especially with miniaturization of electronic devices, leading to issues with mechanical properties and temperature differences in solder joints, which affect the reliability of connections.
Innovation Solution
A solder alloy composition with specific ranges of As, Bi, Pb, and Sb is developed to suppress viscosity increase, enhance wettability, and narrow the temperature difference between liquidus and solidus temperatures, ensuring stable performance and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flux having a high activity is used to improve the wettability of the molten solder, then the wettability is improved, but the reaction of the solder alloy and the active agent increases, thereby increasing the viscosity of the paste
Solution Approach 1:
The patent changes the chemical composition parameters of the solder alloy by adding As (0.003-0.03 mass%) and Sb (0.003-0.03 mass%) elements. These compositional changes suppress the oxidation of Sn and improve wettability without requiring high-flux activity, thereby avoiding excessive viscosity increase while achieving reliable soldering performance.
Solution Approach 2:
The patent creates a composite solder alloy system combining Sn base metal with As and Sb additive elements. This composite composition works synergistically where As suppresses oxidation and Sb improves wettability, achieving both low viscosity and high wettability through material composition optimization rather than flux strength adjustment.
2Stability of the object's composition
If the amount of As is increased to suppress the increase in viscosity, then the viscosity increase is suppressed, but the fusibility is deteriorated
Solution Approach 1:
The patent optimizes the As content to a specific range (0.003-0.03 mass%) where it effectively suppresses viscosity increase through oxidation inhibition, while simultaneously introducing Sb (0.003-0.03 mass%) to improve wettability and compensate for any fusibility deterioration, achieving a balanced parameter optimization.
Solution Approach 2:
The Sb element acts as an intermediary that mitigates the negative effects of As on fusibility. While As suppresses viscosity increase, Sb compensates for fusibility deterioration by improving wetting characteristics, creating a balanced system where neither element's drawbacks dominate.
3Volume of moving object
If an electronic device is miniaturized to achieve smaller size, then the size is reduced, but the time required to use up the purchased solder paste is prolonged, leading to viscosity increase
Solution Approach 1:
The solder alloy composition itself provides the solution by incorporating As and Sb elements that actively suppress oxidation and viscosity increase during storage. The material self-regulates its stability properties through its compositional design, eliminating the need for external preservation measures even when storage time is extended due to miniaturization.
Data Source
AI summary
A solder alloy is provided which suppresses the change in a solder paste over time, decreases the temperature difference between the liquidus-line temperature and the solidus temperature, and exhibits a high reliability. The solder alloy has an alloy constitution composed of: 10 ppm by mass or more and less than 25 ppm by mass of As; at least one selected from the group consisting of 0 ppm by mass to 10000 ppm by mass of Bi and 0 ppm by mass to 5100 ppm by mass of Pb; more than 0 ppm by mass and no more than 3000 ppm by mass of Sb; and a remaining amount of Sn; and satisfies both the formula (1) and the formula (2).300≤3As+Sb+Bi+Pb (1)0.1≤{(3As+Sb)/(Bi+Pb)}×100≤200 (2)In the formula (1) and the formula (2), As, Sb, Bi, and Pb each represents an amount thereof (ppm by mass) in the alloy constitution.