Tin Solder Alloy Purification via Organic Acid Reaction
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Solution Overview
Problem
Conventional solder alloys face challenges in forming miniature, fine, narrow-pitched circuits due to excessive solder volume, leakage failures, and the generation of Kirkendall voids, which affect the reliability and impact resistance of electronic components under high-temperature exposure.
Innovation Solution
A tin or solder alloy production method involving the use of organic acids with a carboxyl group to remove metal oxides and impurities, reducing oxygen concentration to near-zero, resulting in improved ductility, lower viscosity, and enhanced solderability, allowing for the formation of high-density, reliable joints without flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder alloys are used for fine and narrow-pitched circuits, then soldering can be performed by soaking in molten solder liquid, but excessive solder volume forms projections causing leakage failures
Solution Approach 1:
The invention changes the chemical composition parameters of the solder alloy by adding specific elements (Ni: 0.01-1.0 mass%, Ge: 0.01-0.5 mass%, and/or In: 0.01-0.5 mass%) to control the solidification characteristics and reduce excessive solder volume, thereby preventing leakage failures in narrow-pitched circuits
Solution Approach 2:
The invention uses a disposable flux coating applied to the solder alloy that decomposes during soldering to control the soldering process and prevent excessive solder formation, allowing for precise control in fine-pitch applications
2Object-affected harmful factors
If lead-free solder alloys are used to replace tin-lead solder, then hazardous substance restrictions are met, but thermal fatigue resistance and impact resistance deteriorate
Solution Approach 1:
The invention creates a composite solder alloy system combining Sn with multiple additional elements (Ni, Ge, In) that work synergistically to improve thermal fatigue resistance and impact resistance while maintaining lead-free composition, achieving both environmental compliance and enhanced reliability
Solution Approach 2:
The invention optimizes the concentration ranges of multiple alloying elements to achieve the desired mechanical properties and thermal fatigue resistance, transforming the material parameters to overcome the inherent weaknesses of conventional lead-free solders
3Ease of manufacture
If solder alloys with metallic oxide are used, then soldering can be performed, but viscosity increases and solderability decreases
Solution Approach 1:
The invention employs a flux coating that is applied to the solder alloy and decomposes during the soldering process to remove metallic oxides, enabling easy soldering while maintaining low viscosity and high solderability throughout the manufacturing process
4Ease of manufacture
If conventional solder alloys are used for long-time high-temperature exposure, then soldering can be performed, but Kirkendall voids are generated reducing impact resistance
Solution Approach 1:
The invention develops a composite solder alloy containing multiple elements (Ni, Ge, In) that work together to suppress Kirkendall void formation during high-temperature exposure, maintaining impact resistance while preserving soldering capability
Solution Approach 2:
The flux coating decomposes during soldering to leave behind a protective residue that helps prevent void formation during subsequent high-temperature exposure, improving long-term reliability without affecting the initial soldering process
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 method enables the production of miniature, fine-pitched electronic circuits with improved joint reliability, reduced leakage failures, and enhanced impact resistance, allowing for the assembly of small-sized, lightweight semiconductor and electronic apparatuses with high-density, high-reliability connections.
Implementation Method 1
metal oxides and impurities are removed and defecated by reacting with a solution containing 1-80 mass % of organic acid having a carboxyl group (—COOH)
Implementation Method 2
The liquids 14 and 17 are circulated to the reactor 1 via the pump 15, the pipe (for the molten tin or the molten solder liquid) 16, the pump 18 and the pipe (for the organic acid solution) 19 respectively, and the metal oxides and the impurities existing in the molten tin or the molten solder alloy are removed and defecated
Data Source
AI summary
The invention provides a technique and a device that dramatically improve joint reliability of miniature joints of fine electronic components. According to the invention, when producing a tin or a solder alloy used for electronic components, an ingot of a tin or a solder alloy is heated, melted and delivered to a reactor. Also, a solution containing organic acid having a carboxyl group (—COOH) is delivered to the reactor. After stirring and mixing the two liquids intensively, the mixed liquid is separated into a molten tin or a molten solder alloy liquid and an organic acid solution according to the difference in specific gravity. Then, the respective liquids are circulated to the reactor, and the metal oxides and the impurities existing in the molten tin or the molten solder alloy are removed, and the molten tin or the molten alloy is purified to have oxygen concentration of 5 ppm or less.