Sn-Ag-In-Bi-Sb Solder Alloy Thermal Cycle Durability
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Solution Overview
Problem
Lead-free solder alloys used in electronic devices face challenges in durability and resistance to phase transformation under severe temperature cycle conditions, leading to potential short circuits and damage, especially when soldering components of varying sizes.
Innovation Solution
A solder alloy composed of tin, silver, indium, bismuth, and antimony, with specific content ratios and optional inclusion of copper, nickel, cobalt, gallium, germanium, and phosphorus, is developed to suppress phase transformation and ensure durability across different component sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free solder alloys are used to reduce environmental load, then environmental compatibility is improved, but durability and resistance to phase transformation under severe temperature cycle conditions deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional ratios of multiple alloying elements (Sn-3.0Ag-6.0In-0.5Bi-0.5Sb) to achieve a eutectic-like composition that suppresses solid solubility and minimizes phase transformation temperature ranges, thereby improving durability while maintaining lead-free environmental compatibility
Solution Approach 2:
The patent uses composite materials by creating a multi-element alloy system combining Sn, Ag, In, Bi, and Sb that forms a complex eutectic structure with suppressed solid solubility, achieving both environmental compatibility and enhanced reliability under thermal cycling through the synergistic interaction of different elements
2Reliability
If narrow melting range and low melting point are achieved for excellent wettability, then soldering performance is improved, but resistance to phase transformation and deformation under temperature cycles deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the compositional parameters to achieve a specific eutectic-like composition (Sn-3.0Ag-6.0In-0.5Bi-0.5Sb) that simultaneously provides narrow melting range for good wettability and suppressed solid solubility for phase transformation resistance, resolving the contradiction between soldering performance and thermal stability
3Adaptability or versatility
If solder alloy is used for components of varying sizes, then versatility is improved, but uniformity of durability across different component sizes deteriorates
Solution Approach 1:
The patent applies universality by developing a solder alloy with eutectic-like characteristics and suppressed solid solubility that provides uniform durability performance across different component sizes (from 1005 to 3216 chip sizes), allowing the same material to universally satisfy reliability requirements for various electronic components
Data Source
AI summary
A solder alloy substantially consists of tin, silver, indium, bismuth, and antimony. With respect to the total amount of the solder alloy, the content ratio of the silver is 2.8 mass% or more and 4 mass% or less; the content ratio of the indium is 6.2 mass% or more and 9.0 mass% or less; the content ratio of the bismuth is 0.7 mass% or more and 5.0 mass% or less; the content ratio of the antimony is 0.3 mass% or more and 5.0 mass% or less; and the content ratio of the tin is the remaining ratio and the value of A in the discriminant (1) is 4.36 or less. A=0.87×In content ratiomass%−0.41×Ag content ratiomass%−0.82×Sb content ratiomass%