Tin Stripping Additive with Corrosion Inhibitors

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Solution Overview

Problem

Conventional methods for recycling tin from electronic components, such as burning and acid-washing, are inefficient and environmentally harmful, and the increasing demand for Pb-free tin requires a more effective and sustainable recycling method.

Innovation Solution

A tin stripping additive comprising copper and nickel corrosion inhibitors, used in conjunction with nitric acid, reduces the amount of nitric acid required while maintaining high tin-stripping efficiency, and a method involving immersion, alkaline solution addition, heating, and reduction reactions to recover tin, along with a reaction tank design for efficient metal recycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If conventional acid-washing method is used to recycle tin, then tin can be obtained from waste PCBs, but the process causes environmental pollution and requires large amounts of strong acid

Engineering Contradiction:

Improvetin recycling efficiencyVSAvoidenvironmental pollution from strong acid

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical parameters of the stripping solution by using nitric acid with controlled concentration (67-68 wt %) combined with specific corrosion inhibitors (copper corrosion inhibitor and nickel corrosion inhibitor), thereby reducing the harmful effects while maintaining effective tin stripping capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces corrosion inhibitors as intermediary substances that mediate between the nitric acid and the metal surfaces, protecting copper and nickel components while allowing tin to be selectively stripped, thus reducing overall acid consumption and environmental impact

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of substance

If conventional burning method is used to recycle metals from PCBs, then noble metals can be obtained, but air pollution is caused due to bromine-containing waste gas and dioxin

Engineering Contradiction:

Improvemetal recoveryVSAvoidair pollution from burning

Core Design Contradiction:

Loss of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the thermal/mechanical burning process with a chemical wet stripping method using nitric acid solution, thereby avoiding the combustion reactions that generate harmful air pollutants like dioxin and bromine-containing gases while still achieving effective metal recovery

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If mechanical physical recycling method is used to separate metals, then metal materials can be separated by density, but the purity of obtained metal is too low

Engineering Contradiction:

Improvemetal separation efficiencyVSAvoidmetal purity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent extracts tin specifically from the complex metal matrix of PCBs through selective chemical dissolution, separating tin from other metals based on their different chemical reactivities with nitric acid, thereby achieving high purity tin recovery that mechanical methods cannot accomplish

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If Pb-free tin paste is used to meet RoHS requirements, then environmental compliance is achieved, but the price of tin has significantly increased

Engineering Contradiction:

Improveenvironmental complianceVSAvoidtin cost

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent establishes a recycling process that recovers tin from waste electronic components and PCBs, creating a closed-loop system that reduces dependence on virgin tin resources and helps stabilize tin pricing while maintaining compliance with Pb-free requirements

Inventive Principle:

Principle #34Discarding and recovering

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 effectively recycles tin with reduced environmental impact and improved efficiency, achieving high purity tin recovery while minimizing nitric acid usage and operational risks.

Implementation Method 1

immersing an object to be processed into the tin stripping solution to obtain a wash-off solution

Methodology Applied

Scientific EffectChemical dissolution: Oxidation

Implementation Method 2

adding an alkaline solution to the wash-off solution to obtain a precipitate

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Implementation Method 3

heating the precipitate

Methodology Applied

Scientific EffectThermal heating: Heating

Implementation Method 4

conducting a reduction reaction to the precipitate being heated to obtain tin

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentUS11180826B2Tin stripping method

Publication Date: 2021.11.23 UWIN NANOTECH

AI summary

The present invention provides an additive for tin stripping, comprising 0.1 to 20 wt % of copper corrosion inhibitor and 0.1 to 20 wt % of nickel corrosion inhibitor; wherein said weight percentage is based on the total weight of said additive. The present additive can be used with nitric acid conventionally used for metal-stripping for not only reducing the usage of nitric acid but also improving the efficiency of tin stripping. The present invention also provides a method for Tin recycle and a reaction tank for metal recycle. Both of them are favorable for satisfying the needs of metal recycle (especially, tin recycle) in the field.