​ Various processing methods of PCB recycling

According to the 2021 State of Used Electronics Survey, 62 percent of consumers have one to three used electronics, and 38 percent have more than three. There are three ways to recycle old mobile phones: newer or less damaged ones are refurbished and end up in the second-hand market; If there is some damage, the available parts will be disassembled and reused; Completely unusable, can be used for refining raw materials. Most people's old phones sit idle at home. According to industry data, the number of mobile phones in China reached 1.856 billion in 2021.

Electronic products have circuit boards.With the constant upgrading of electronics, most households are hoarding discarded mobile phones, computers, cameras and other electrical and electronic products.

Discarded electronic products are full of treasure.

Waste electrical and electronic products are difficult to dispose of in several ways. First, electronic products themselves easily cause pollution. Waste electrical and electronic products generally contain heavy metals such as lead, mercury, cadmium and some other toxic and harmful substances. If abandoned, incinerated or refined by backward technology, it will cause serious harm to human body and the environment. Second, the quantity of waste electronic products is large, but the recycling channel is not perfect. China is a big producer and consumer of electrical and electronic products, many of which have reached the peak of obsolescence. Statistics show that in recent years, about 220 million household appliances have been scrapped annually in China, with an annual growth rate of about 16%. To this end, China has introduced relevant policies to standardize the recycling and dismantling system. However, it should be noted that problems still exist in the industry, such as small recycling scale, opaque recycling price, blocked channels and repeated prohibition of private dismantling. Third, users worry about their privacy disclosure, information deletion cost is high, but also significantly reduce the willingness to recycle. In addition, some products themselves do not take up much space, many people often put abandoned products in the home.

But every coin has two sides. The saying "garbage is a misplaced resource" also applies to the recycling of discarded electrical and electronic products. On the one hand, these products are "covered with treasure", containing non-ferrous metals, ferrous metals, glass, plastics and other recyclable substances. If effectively recycled and used, resources and energy consumption in ore mining, transportation, smelting, processing and molding can be greatly reduced, and environmental pollution can be reduced. On the other hand, straightening out the recycling channels of waste electrical and electronic products and improving the level and capacity of deep processing, reuse and remanufacturing in the recycling industry is not only conducive to the development of circular economy and the cultivation of people's green consumption concept, but also conducive to the realization of the "double carbon" goal.

To "turn waste into treasure", the key is to change the way of thinking. In recent years, China has revised and adopted the Circular Economy Promotion Law and issued the 14th Five-Year Plan for Circular Economy Development, which requires that in the process of production, circulation and consumption, the principle of "reduction, reuse and resource recovery" should be followed, and efforts should be made to build a resource-recycling industrial system and accelerate the construction of a recycling system of waste materials, so as to improve resource utilization efficiency and realize sustainable economic and social development. In the recycling of waste electrical and electronic products, we should change the concept of "electronic waste" in the past, but as an "electronic mine" in urgent need of effective use, and guide the production, circulation, consumption, recycling, recycling and other links of related products.

It is also important to improve the recycling system of waste electrical and electronic products. Like garbage recycling, the recycling of waste electrical and electronic products also involves production, consumption, recycling, reuse and other links, and the work needs to be promoted in an integrated way. At the production end, the extended producer responsibility system should be established and perfected to require producers to take good environmental responsibility within the product life cycle. At the consumer end, on the one hand, we should enhance consumers' awareness of environmental protection through publicity and education, and on the other hand, we should pay attention to consumers' concerns and protect the security of personal information. "14th Five-Year" circular Economy Development Plan "proposed to protect the whole process of mobile phones, computers and other electronic products recycling personal privacy information security; Recyclers should clean up users' personal information, according to a draft regulation on recycling waste electrical and electronic products issued by Beijing. These steps are certainly a good start. At the recycling and utilization end, production enterprises, recycling enterprises, e-commerce platforms and dismantling enterprises should be guided to play their respective roles, and all parties should be encouraged to promote high-value utilization through diverse participation and scientific and technological innovation, so as to balance the economic and social benefits of enterprises.

The recycling of waste electronic products is a huge and complex industry. According to the value of the components of the waste electronic products themselves, each component is digested by the recycling industry of different links of different chains in turn. For example, the whole metal shell enters the metal recycling industry, the shell or structural part of the polymer material with the whole structure enters the polymer recycling industry, and the electronic components enter the electronic component recycling industry. Basically become the main force of second-hand electronic components market. It can be said that each component of these waste electronics has a corresponding recycling cycle.

The recycling of printed circuit board is also an important component, and it is a difficult part of recycling, which is determined by the composition and components of discarded PCB.

So, what are the disposal methods of PCB recycling?

PCB recycling

According to the structure of PCB board is divided into single-sided printed board, double-sided printed board, multi-sided printed board, according to the insulation material is divided into paper base board, glass cloth base board, synthetic fiber board, etc. PCB board is a wide variety of complex structure, but the types of materials contained in it have similarities, all kinds of printed circuit boards are composed of metal, glass fiber, polymer resin, etc. At the same time in order to prevent the circuit board short circuit introduced some flame retardant halide flame retardant and so on. Studies have shown that recycling of PCB board is easy to cause secondary pollution, causing serious damage to the environment. Discarded PCB board contains heavy metals such as lead, mercury and chromium, as well as conventional metals such as gold, silver, copper and tin, as well as components such as polybrominated biphenyls and polybrominated diphenyl ethers, which are easy to cause air pollution. However, if properly used, Abandoned PCB also has high economic value, is a real inexhaustible urban mine.

According to the composition characteristics of discarded PCB, its recycling treatment technology mainly includes heat treatment, chemical treatment, mechanical and physical treatment, and because of the advantages and disadvantages of each method, a variety of methods are often used for comprehensive treatment.

Heat treatment method. Heat treatment method is mainly to remove the polymer material part of PCB by means of incineration, sintering, pyrolysis, microwave, melting and other means, so as to achieve the purpose of metal enrichment. In the heat treatment method, the main core is metal recovery, and the non-metallic part is separated by temperature difference, so it is easy to produce toxic and harmful gases and secondary waste.

Chemical treatment. Chemical treatment is a method of separation and purification by using chemical agents with different differentiation stability of PCB circuit boards groups, mainly including washing method, dissolution method, etc. The advantage of chemical method is that it can finally get more pure products, but the waste gas, waste water, waste residue and so on is a difficult problem

Mechanical physical treatment method is to crush PCB to a certain size of particle size, so that the metal part and the non-metal part are separated from each other, and then according to the differences between the two, the separation is carried out. According to the difference of the density, particle size and conductive and magnetic characteristics of the crushed metal and non-metallic mixed particles, gravity field separation, electric field separation and magnetic field separation are adopted. According to the current market frontier, the mechanical and physical recovery and separation technology combining crushing, screening, classification, gravity separation, electrical separation and magnetic separation has the advantages of low cost, good resource regeneration effect, high recovery rate and small secondary pollution. The development direction of composite marketization should become the main technology and method of waste PCB resource recovery at present and in the future.