The manufacturing principle of printed circuit board is composed of electricity, chemistry, machinery, materials, optics and other sciences, so its manufacturing
The process is complex and requires the use of various chemicals and special raw materials. A variety of wastes will be produced in the manufacturing process.
Many, or liquids; Or muddy; Or solid, etc. Its composition not only contains a variety of organic pollutants, but also has a large number.
Many heavy metals, such as copper, lead and nickel. If such wastes are not properly treated (intermediate treatment, reuse or final disposal)
Set) and arbitrarily discarded, its influence is very extensive, such as pollution of drinking water sources, damage to the environment, damage to human health, etc. , will also
Leading to an increase in corporate entities and social costs.
As mentioned above, there are all kinds of wastes in PCB manufacturing, such as waste PCB or
Powder, copper-containing sludge, waste etching solution, waste acid and alkali or waste liquid containing heavy metals, etc. ) There are different ways to use corresponding resources.
This paper only discusses the recycling technology of tin (tin-lead) stripping waste liquid.
First, the source of tin (tin-lead) stripping waste liquid
Generally speaking, the main purpose of tin-lead plating unit in printed circuit board process is to protect printed circuit board.
The printed circuit on the substrate will not be eroded during the etching process. Then, the unit is etched and enters the tin-lead stripping sheet after etching.
Yuan; The types of tin and lead stripping solution used in the process device can be roughly divided into nitric acid system, hydrofluoric acid system, fluoroboric acid system and so on.
Its main component is stripping acid (such as hydrofluoric acid, nitric acid, etc. ), oxidant (such as hydrogen peroxide, etc. ), buffers and interfaces.
Active agent, etc.
The tin-lead stripping unit uses a tin-lead stripping solution to strip the tin-lead coating on the printed circuit board.
In the process of tin stripping, the composition of tin-lead tin stripping solution will gradually decrease, and its tin stripping effect will gradually weaken, while tin stripping.
The content and concentration of tin, lead and copper in lead solution will increase. According to the experience of the factory, the aging process of different kinds of tin-lead stripping solutions is judged.
Generally speaking, when the tin content reaches about 50 100gL or the acid equivalent drops below 3.4 N, it will
As waste liquid, it needs to be replaced.
In short, the waste liquid from tin-stripping (tin-lead stripping) comes from the tin-lead stripping unit in the printed circuit board process, and its main component is fluorination.
Ammonium, nitric acid, hydrogen peroxide, etc., such as: COD is about 20,000 25,000 mgLCu2+ is about 1 0,000.
1, 0,500 mgLPb2+ is about1000015000mgl; Fe3+ is about 0.3 million mgl, etc.
Second, the recycling technology of tin (tin-lead) waste liquid
Technical reports, reports and guides
Due to the great demand for metal raw materials in the world, the recycling of tin (tin-lead) waste liquid is of great significance.
As long as the technical principle and engineering practice are feasible, economic incentives can be put into practice. As for its resource utilization rate, it can be roughly
It can be divided into "stock solution regeneration" and "reuse". The so-called "stock solution regeneration" means directly mixing the original waste liquid.
After the substance (i.e. no stock solution) is effectively separated, the composition is properly mixed with the composition to form a new tin (tin-lead) stripping solution;
"Reuse" refers to the removal of valuable substances (such as tin, lead, copper, etc.) from the original waste liquid by physical, chemical and heat treatment techniques.
) can be separated into single metal or compounded into oxide salt, etc.
However, in the actual factory operation and application, the above two recovery methods are not all operated separately.
The published technology or case of recovering tin (tin-lead) waste liquid can be "reused" separately; or
To cooperate with "stock solution regeneration"; Or separate "stock solution regeneration" and the like. Now, all kinds of representative tin stripping (tin
The summary of waste liquid recovery technology is shown in table 1. According to technical analysis, "reuse" systems and equipment.
It can be applied to various series of tin (tin-lead) waste liquid, which is generally reused outside the mine plant (relative to the production source).
The technical level is not high and the derivative products are diversified. The system and equipment of "stock solution regeneration" need to be stripped according to various series.
Tin (tin-lead) waste liquid can be adjusted, which can be operated in the factory or outside the factory (relative to the production source). The technical level is
High and unique, its derivatives can monopolize the market if they are effective. Based on the current domestic situation, it has been proved that.
In the case of factories, electrolytic recovery is the main unit, and then tin (tin-lead) waste is stripped off with related physical and chemical procedures.
"Regeneration" and "Reuse" of liquid. In addition, neutralization precipitation or oxidation-reduction combined fire method is also used.
Metallurgical process for recycling tin metal.
Table 1. Summary and evaluation of recycling technology of tin (tin-lead) stripping waste liquid
Resource utilization mode
Regeneration and reuse of stock solution
Technical characteristic data source analysis
◎ ○
Taking the waste liquid of tin (tin-lead) removal from nitric acid as the regeneration object,
Using electrolytic treatment, the original solution can be recovered in the factory and then
Health; Continuous or semi-continuous operation is possible; In the original waste liquid
Valuables (such as tin, lead, copper, etc.). ) may be in metal form.
Recycling; Subsequent processes such as precipitation and filtration are not needed.
U.s. patent number
Code: 494485 1 high technical level; System flow simplification
Want; High resource utilization efficiency.
◎
The waste liquid from tin stripping (tin and lead) in fluoboric acid system is used as its regeneration pair.
Elephant; Using procedures such as precipitation, filtration and ion exchange,
Impurities are directly removed from tin stripping waste liquid, and then fluorination is added.
Ammonium bicarbonate, hydrogen peroxide and other additives. , is mixed.
Regeneration.
U.s. patent number
Code: 467352 1
The system process is more complicated, but relatively expensive.
The source benefit is high; There must be a specific system.
The capacity of the original solution formula listed.
◎
Adde KOH into that tin sulfide waste liquid containing tin oxide,
Tin metal is made by electrolysis.
U.s. patent number
Code: 473735 1 low technical level; The system flow is larger.
Brief; The benefits of resource utilization are acceptable.
◎
Taking the waste liquid of tin (tin-lead) removal from nitric acid as the regeneration object,
Removing lead with sulfate or bisulfate, separating,
Then the stock solution is regenerated.
U.s. patent number
Code: 5505872, with high technical level; System flow simplification
Want; There must be a specific series of stock solutions.
Formulation ability; High resource utilization efficiency.
◎: Mainly; : secondary
Table 1. Overview, collection and evaluation of recycling technology of tin (tin-lead) stripping waste liquid (continued)
Resource utilization mode
Regeneration and reuse of stock solution
Technical characteristic data source analysis
◎
Keywords neutralization precipitation, redox, pyrometallurgical technology,
Recover tin metal from it.
College of the Republic of China
Profit number:
177,9 1 1
The technical level is not high; The system flow is larger.
Brief; The efficiency of resource utilization is acceptable; should do
Consider the cost of energy and pollution prevention.
◎
The waste liquid of tin (tin and lead) removal in fluoboric acid system or nitric acid system is used as
Reuse objects; The method is to apply continuous chemical reaction.
Step: adding precipitant and neutralizer into the waste liquid respectively.
Agent, filtration, heating to remove ammonia, precipitation and dissolution, etc.
Separation procedures to realize the recovery of valuable components in waste liquid (such as
Sodium stannate with a purity of more than 96% and sodium fluoride with a purity of 80% (or
Sodium nitrate) and 93% copper sulfate crystals.
College of the Republic of China
Profit number:
472,030
The system flow is complex; Relative resources
High quality of chemical products; Its overall interests
It remains to be considered.
◎ ◎
The waste liquid from tin and lead removal was reused by "selective electrolytic recovery method"
Produce tin and lead stripping stock solution, and recover valuable at the same time.
Copper, tin, lead and other metals, tin dioxide, nitrous oxide
Tin, tin hydroxide and other compounds and valuable inorganic salts.
Products.
College of the Republic of China
Profit number:
160,880
High technical level; The system flow is complicated.
Miscellaneous; There must be a specific series of stock solutions.
Formulation ability; High resource utilization efficiency.
◎: Mainly; : secondary
Third, the conclusion
Based on the above analysis, we can know the factors that must be considered when choosing the recycling technology of tin (tin-lead) waste liquid.
Quite a few, such as "applicable waste liquid", "chemical dosage", "practical operability", "energy input", "pollution prevention" and "development"
The value of raw products, etc. If the representative technologies listed in table 1 are evaluated, they actually have their own advantages and disadvantages. In short,
In order to balance environmental protection and economy, it is a challenge to find the "right" technology.
A comprehensive analysis of students' future trends and resource trends should give a satisfactory answer.
Zheng Zhi, Manager of Environmental Protection Center of Industrial Technology Research Institute, and