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Recycle Tin From Wasted-PCB Environmentally and Profitably

By Korbin Lan
Published: Oct 02,2014

Precious metals are indispensable production materials for electronics products and parts and components. These include wafers, resistors, capicitors, and connectors. Furthermore, PCB panels require precious metals for production and welding.

With daily rising demands and costs of precious metals, the production costs for electronic technology companies are also rising. Finding ways to reduce costs for precious metals is crucial to the industry’s future development.

On the other hand, disposed of electronics parts and components and PCB panels contain many precious metals. If throwing these materials away causes serious pollution to water resources, air, and soil and there is no well-arranged treatment or recycling, this will cause a grave impact on the environment and human lifestyles that will be difficult to remedy.

As Electronics Products Multiply, Electronics Waste is Becoming a Global Problem

With one place after another around the world starting to use 4G networks along with the popularization of the Internet of Things and more and more smart electronic devices expected to be presented to the public, it is expected that the use of all kinds of electronics parts and components and PCB panels will also rise and drive a further increase in the demand for precious metals.

At the same time, however, currently the lifespan of electronics products is shrinking substantially, which is causing people to dispose of large quantities of electronics products, and this is causing problems with electronics waste.

According to a UN report, including mobile phones and computers, approximately 50 million tons of electronics waste is produced globally each year, and it is possible that this rate will grow by 500%. This is especially the case in some developing countries, such as India and China.

Figure 1 :   Incineration of PCB board will produce a lot of dioxin and suspended particles, have serious air pollution
Figure 1 : Incineration of PCB board will produce a lot of dioxin and suspended particles, have serious air pollution

Currently, the United States produces the most electronics waste in the world, which is approximately 3 million tons of garbage. China produces the second highest amount of electronics waste, which is approximately 2.3 million tons of garbage.

Electronics waste contains large quantities of harmful chemical elements, such as lead, cadmium, beryllium, and mercury, and if they are carelessly disposed of, they are harmful to humans and the environment.

In addition, the current methods of treatment and recycling for electronics products are unsafe and inefficient. Even in developed countries, the industrial procedures for treating disposed of electronics are liable to create major safety threats for employees and residents of nearby communities.

Therefore, the most significant cause of danger to employees and to the environment is that the current facilities for recycling electronics use shredding, disassembly, and burning as their primary methods. Not only are the results poor, but they also produce dioxin pollutants.

Although electronics waste contains poisonous materials, they also contain some valuable scarce materials. Certain complex electronics facilities may contain up to 60 types of chemical and metal elements, and if they can be properly and effectively recycled, this will be a win-win situation for both the environment and for technological development.

The Cost of Tin rising, Recycling Tech is a Shining Star for Industry

PCB panels in particular have large amounts of metal materials, including precious metals such as gold, silver, copper, and tin. If the portions of these metal materials can be separated, stripped, and recycled, not only can the efficiency of their re-use be increased, but the entire production costs can be improved. This can also help the industry to progress a step in increasing its own production capacity.

In addition, electronics parts and components are welded to rigid PCB panels with solder paste, which contains large amounts of metal tin. As long as these metal tin materials are recycled, they can be re-used, and this can reduce production costs for businesses.

Figure 2 :   Tin price graphs (2003 to 2013)
Figure 2 : Tin price graphs (2003 to 2013)

Furthermore, after stripping the tin, electronics components such as circuit ICs, capacitors, transistors, and connectors can be easily obtained. Not only does this increase the speed and efficiency of recycling, but precious metals such as gold, silver, and palladium can also be collected from these parts and components.

On the other hand, Uwin Nanotech is researching and developing a new type of environmentally-friendly tin recycling technology that can selectively strip out metal materials.

Uwin Nanotech General Manager Xu Jing-xiang says, “The current methods of recycling PCB panels, for the most part, use burning or strong acids to strip away and collect precious metals; however, the former produces dioxin while the later pollutes the soil.”

Xu Jing-xiang further explained that using a burning method to burn PCB panels will produce large amounts of dioxin and suspended particles that heavily pollute the air.

Because the later uses strong acids such as nitric acid and aqua regia to strip away precious metals, the process is not only hazardous to the employees’ health, but after the treatment if the waste liquid containing tin that is left over is carelessly dumped out, it can seriously pollute the soil and water resources.

Environmentally-Friendly Tin Stripping Can Reach a Recycling Purity of 99.96%

In order to improve traditional stripping methods with nitric acid, Uwin Nanotech has begun to research environmentally-friendly stripping of tin additives and has successfully experimented with a neutral and environmentally-friendly stripping prescription – SnST-550A.

Xu Jing-xiang pointed out that this additive prescription for stripping tin uses a nickel corrosion inhibitor and a corrosion inhibitor for copper as neutral aqueous solutions in order to selectively strip away tin coating and more fully remove electronic parts and components from the motherboards and then follow-up with the recycling and treatment of all kinds of metals.

Figure 3 :   Electronic components can still be properly after stripping tinned, even pins and lines still intact, can increase subsequent reuse or recycling benefits
Figure 3 : Electronic components can still be properly after stripping tinned, even pins and lines still intact, can increase subsequent reuse or recycling benefits

As for the basic foundation of the environmentally-friendly tin stripping solution, it uses a chemical reaction produced by nitryl and tin to form a mercurous nitrate tin compound, and afterwards it obtains hydroxide solids using an acid-base titration deposition method.

“Using this tin-stripping solution, tin components soldered onto circuits can easily be obtained and the tin can be purified, in order to obtain the highest purity tin,” said Xu Jing-xiang.

Moreover, besides being safe and harmless, this type of environmentally-friendly tin-stripping solution is simple and easy to use, while also being highly efficient at stripping. Xu Jing-xiang stated that a server PCB panel with complex and lumber circuits only has to be soaked for 40 minutes in order to strip away the tin plating.

More importantly, after tin-stripping, the electronic components can be properly maintained with even pins and wires still intact, and this increases the effectiveness of re-using and recycling.

After acid-base titration, with a purification method using hydroxide solids, Uwin Nanotech’s procedure is extremely simple and safe. Because sodium nitrate is soluble in water, tin products only need to be rinsed in pure water, filtered, and baked in order to purify most of the tin.

Furthermore according to Uwin Nanotech’s EDX testing, after being washed in water, the amount of tin in solids is increased from 44.92% to 85.58%. Finally using an 800℃ high-temperature calcine purifying method, the reduced tin will be high-purity tin with a purity level of 99.96%.

Figure 4 :   calcined the tin compounds at 800 ℃ Celsius to reduction, achieved purity of 99.96%
Figure 4 : calcined the tin compounds at 800 ℃ Celsius to reduction, achieved purity of 99.96%

A Green Environment at An Environmentally-Friendly Cost

Using the SnST-550A tin-stripping formula, is not only a complete improvement over traditional treatment methods that use burning and strong acid procedures, it also is bringing about better treatment techniques for the electronics recycling industry and providing a better and more humane working environment.

It is also capable of significantly reducing pollution problems that may be caused by air and waste water treatment, and it is making a positive contribution to environmental protection.

More importantly, this tin-stripping prescription will greatly increase the effectiveness of tin recycling, while also increasing the quantity of precious metals (gold, silver etc.) that are re-used and recycled. It is also a great benefit to the operations and development of other related industries.

According to Uwin Nanotech’s estimations, if the all of the tin, gold, copper, and silver in disposed of computer motherboards is recycled, each ton will be worth approximately NT$450,000, and the value of each ton of recycled panels from thrown-away cellphones will be worth NT$600,000. The real economic benefits are considerably apparent.

Therefore, from the perspective of the current penny-pinching electronics industry in Taiwan, if the current manufacturing procedures can incorporate methods for recycling and re-using materials, their cost configurations can be improved and their entire production costs can be reduced.

From the perspective of recycling companies, creating more efficient recycling methods and better working environments is also a plan that cannot be delayed.

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