Low-alpha Tin Purification via Electrolysis for Semiconductor Solder
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Solution Overview
Problem
Recent semiconductor devices are prone to soft errors due to alpha rays emitted from materials in their vicinity, necessitating high-purity tin or tin alloys with reduced alpha radiation for solder materials.
Innovation Solution
The method involves reducing the alpha dose in tin by minimizing the content of lead isotope 210Pb through electrolysis, achieving an alpha dose of less than 0.0005 cph/cm² by controlling the pH and tin concentration in the electrolyte, and using raw material tin with a lead isotope 210Pb content of 30 Bq/kg or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional refining methods are used to reduce alpha dose in tin, then alpha radiation level decreases, but production time increases significantly (three years or more)
Solution Approach 1:
The patent applies preliminary action by selecting raw material tin with already-low lead isotope 210Pb content (30 Bq/kg or less) before the refining process. This pre-selection ensures that the tin requires minimal refining time to achieve the target alpha dose level, eliminating the need for long-term storage or extended refining processes required by conventional methods
2Object-affected harmful factors
If lead isotope 210Pb is removed from tin to reduce alpha dose, then alpha radiation level decreases, but manufacturing complexity increases
Solution Approach 1:
The patent applies the extraction principle by selectively removing lead isotope 210Pb from tin through electrolysis with controlled pH and tin concentration. The process extracts only the harmful lead isotope while preserving the tin matrix, achieving alpha dose reduction below 0.0005 cph/cm² without requiring complex multi-step purification sequences
Solution Approach 2:
The patent applies parameter changes by optimizing electrolysis conditions, specifically controlling pH within 0.5-2.0 and maintaining tin concentration at 5-50 g/L. These parameter adjustments maximize the removal efficiency of lead isotope 210Pb while simplifying the overall manufacturing process compared to conventional multi-stage refining methods
3Manufacturing precision
If conventional electrolysis conditions are used, then tin purification is achieved, but alpha dose reduction is insufficient
Solution Approach 1:
The patent applies parameter changes by establishing specific electrolysis conditions: pH controlled at 0.5-2.0 and tin concentration maintained at 5-50 g/L. These optimized parameters enable simultaneous achievement of high tin purity and sufficient alpha dose reduction (below 0.0005 cph/cm²), overcoming the limitation of conventional electrolysis conditions that achieve purity but not adequate radiation reduction
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
This approach ensures a consistently low alpha dose in tin over time, reducing the risk of soft errors in semiconductor devices and providing high-purity tin suitable for semiconductor applications.
Implementation Method 1
The method involves reducing the alpha dose in tin by minimizing the content of lead isotope 210Pb through electrolysis
Implementation Method 2
there is an increasing risk of soft errors caused by the influence of α rays emitted from materials in the vicinity of semiconductor chips
Data Source
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AI summary
Disclosed is tin characterized in that a sample of the tin after melting and casting has an α dose of less than 0.0005 cph/cm2. Since recent semiconductor devices are highly densified and of high capacity, there is an increasing risk of soft errors caused by the influence of α rays emitted from materials in the vicinity of semiconductor chips. In particular, there are strong demands for high purification of solder materials and tin for use in the vicinity of semiconductor devices, and demands for materials with lower α rays. Accordingly, an object of the present invention is to clarify the phenomenon of the generation of α rays in tin and tin alloys, and to obtain high-purity tin, in which the α dose has been reduced, suitable for the required materials, as well as a method for producing the same.