When it comes to electronic waste structure, printed circuit boards, which we frequently hear in recycling, come to mind with its complex structure and precious metal content. In order to better understand the recycling methods, these complex structures should first be characterized.
Structure and Contents of PCBs
Printed circuit boards providing connection between software and hardware are found in almost all electronic systems. It is a thin sheet made of epoxy resin and glass fiber coated with copper film layers and contains many electronic components in its structure such as resistance, relay, capacitor, transistor, heat sink, chip lines and processors.
There are metals such as Ga, In, Ti, Si, Ge, As, Sb, Se and Te on the chip lines. Thin Sn or Ag films are used on the surface to protect against oxidation.
The connectors are made of gold and silver. Ceramic capacitors have tantalum and other capacitors have aluminum coated cylindrical structures.
The highest content in terms of metal composition is copper (Cu) used in the circuit, then iron (Fe) used in soldering and lead frames, aluminum (Al), tin (Sn) and lead. (Pb)
In terms of precious metal composition, gold (Au), silver (Ag) and palladium (Pd) are present as contact materials or as coating layers due to their high conductivity and chemical stability.
The outer layer material consists of fiberglass sheets pre-impregnated with epoxy resin. The purity of copper here varies between 86% and 93%.
There are two types of PCBs (ie FR-4 and FR-2) normally used in computers and mobile phones. FR-4 type consists of multilayer epoxy resins and fiberglass coated with copper layer. It is used on small devices such as mobile phones and is usually green or blue.
It is made of FR-2 type cellulosic paper layer and copper coated phenolic structure. It is used in televisions and household items and generally its resins are yellow or brown.
Both cannot be remelted and reformatted. It is thermoplastic like bromine based resins used as flame retardant.
Resins are low quality and high cost organic polymers. Fiber glass fiber used as resin reinforcing fiber makes up about 50-70% of the printed circuit boards.
In this article, organic compounds that make printed circuit boards and the function of some metals are emphasized. Due to its rich content, its components must be well analyzed and recycled to avoid potential risks to the environment and human health. As the Proses Makina team, we develop recycling methods on this road that we set off with the vision of zero waste and meet the demands of our customers in the international arena with our machines that suit with EU standards.