Multi-Element Solder Alloy Composition for Rupture-Resistant Joints
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Solution Overview
Problem
Conventional solder alloys, such as Sn-3Ag-0.5Cu, face challenges in maintaining reliability and preventing rupture under extreme temperature changes and external forces due to differences in thermal expansion and coefficient of thermal expansion between electronic components and substrates, leading to stress concentration at solder joints.
Innovation Solution
A solder alloy composition with specific ranges of Ag, Cu, Sb, In, Ni, Bi, and optional elements like Co, Zr, Fe, and others, optimized to enhance strain energy, tensile strength, and wettability, forming a dense alloy structure that resists stress and maintains joint integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Sn-3Ag-0.5Cu solder alloy is used, then manufacturing cost and ease of manufacture are maintained, but reliability deteriorates under extreme temperature changes and external forces due to stress concentration at solder joints
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of multiple alloying elements (Sn: 90-97 wt%, Ag: 1-5 wt%, Cu: 0.5-3 wt%, Bi: 0.1-2 wt%, In: 0.1-1 wt%, Ni: 0.01-0.5 wt%, Co: 0.01-0.1 wt%) to optimize the solder alloy's mechanical properties. This compositional parameter optimization enhances tensile strength and strain energy while maintaining reliability under thermal stress and external forces.
Solution Approach 2:
The patent employs composite materials by creating a multi-element solder alloy system that combines Sn base metal with multiple alloying elements (Ag, Cu, Bi, In, Ni, Co). This composite alloy structure leverages the synergistic effects of different elements to achieve superior tensile strength, strain energy, and resistance to stress concentration compared to conventional single-element or binary solder alloys.
2Strength
If alloy composition is optimized for tensile strength and strain energy, then resistance to stress concentration improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific compositional ranges for each alloying element to achieve the desired balance between strength and manufacturability. By specifying Sn: 90-97 wt%, Ag: 1-5 wt%, Cu: 0.5-3 wt%, Bi: 0.1-2 wt%, In: 0.1-1 wt%, Ni: 0.01-0.5 wt%, Co: 0.01-0.1 wt%, the patent establishes controllable parameter windows that enable manufacturers to achieve high tensile strength and strain energy without requiring ultra-precise composition control.
Data Source
AI summary
Provided are a solder alloy, a solder ball, a solder preform, a solder paste, and a solder joint which have excellent wettability and high reliability by prevention of rupture of solder joints. The solder alloy has an alloy composition of, by mass %, Ag: 1.0 to 3.8%, Cu: 0.4 to 0.8%, Sb: 0.03 to 2.90%, In: 1.1 to 4.2%, Ni: 0.01 to 0.14%, Bi: 0.1 to 5.0%, with the balance being Sn.