As-Enriched Solder Material for Color-Stable, Wettable Joints
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Solution Overview
Problem
Solder materials face issues with color change and increased viscosity over time, which affect wettability and reliability, especially in the form of solder pastes, and existing solutions do not adequately address these problems while maintaining good wettability and reliability.
Innovation Solution
A solder material with an As-enriched layer on its surface, containing Sn or a Sn-containing alloy and specific amounts of As, Bi, Sb, and Pb, which inhibits color change and viscosity increase, while maintaining excellent wettability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If elements such as P, Ge or Ga are added to a solder material to inhibit yellowing color change, then the color stability is improved, but the wettability of the solder material is degraded
Solution Approach 1:
The patent applies local quality by creating an As-enriched layer specifically on the surface of the solder material, rather than uniformly distributing As throughout the bulk material. This surface-localized As layer (with As content of 0.01-5 wt%) provides color stability by preventing oxidation, while the bulk solder material (with As content of 0.003-0.1 wt%) maintains its inherent wettability properties. The gradient distribution of As from surface to bulk resolves the contradiction between color stability and wettability.
2Stability of the object's composition
If a SnO2 film is formed on the solder layer to inhibit yellowing color change, then the color stability is improved, but the production process becomes complicated due to plasma exposure
Solution Approach 1:
The patent changes the compositional parameter by adding As to the solder material, which fundamentally alters the oxidation behavior. Instead of forming a SnO2 film through plasma exposure, the As-containing solder material forms an As-enriched layer during conventional cooling that naturally prevents yellowing. This parameter change (adding As) replaces the complex plasma process with a simpler, more cost-effective solution that achieves the same color stability goal.
3Duration of action of stationary object
If a solder paste is stored for a long time, then the viscosity of the solder paste increases
Solution Approach 1:
The patent extracts the reactive Sn component that causes viscosity increase through oxidation and replaces it with As-stabilized surface layers. The As-enriched layer on the solder material surface prevents Sn from reacting with oxygen and flux components during storage, thereby extracting the source of viscosity instability. This allows the solder paste to maintain stable viscosity over extended storage periods while preserving printability.
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 As-enriched solder material minimizes color change and viscosity increase, ensuring good wettability and high reliability, even when used as a solder paste, by forming an As-enriched layer that prevents reaction with flux components.
Implementation Method 1
The Sn reacts with oxygen in the air during or after production to form a film of a Sn oxide on the surface thereof, which may cause yellowing color change in some cases.
Implementation Method 2
a solder material including Sn or a Sn-containing alloy and 40 to 320 ppm by mass of As, the solder material including an As-enriched layer
Data Source
AI summary
The present invention provides a solder material containing Sn or a Sn-containing alloy and 40 to 320 ppm by mass of A, the solder material including an As-enriched layer.