A Guide to the PCB Recycling Process

Printed circuit boards (PCBs) serve as the core components of electronic products; they contain valuable materials such as gold, silver, and copper, but also hazardous substances like lead, mercury, and flame retardants. Consequently, whether disposed of via landfill or incineration, they pose a threat to the environment.

Therefore, the key to PCB recycling lies in two primary objectives: recovering the valuable metals and effectively containing the hazardous substances. The recycling process itself can be broken down into several distinct steps.

Step 1: Pre-processing and Disassembly

Circuit boards contain various components—such as capacitors, resistors, and chips—some of which contain precious metals like gold and silver. Therefore, the first step in recycling circuit boards is to remove these small components.

There are two primary methods for disassembly:

The first involves heating the board to over 200 degrees Celsius; once the solder melts, the components can be removed.

The second method utilizes specialized solvents to dissolve the solder, allowing the components to be detached intact and undamaged.

Step 2: Crushing

The second step in bare board recycling is shredding, which is carried out in two stages:

♻️Coarse Shredding:

A dual-shaft shredder is used to cut the boards into small pieces measuring 3 to 5 centimeters.

♻️Fine Shredding:

A hammer mill is used to grind these small pieces into granules of approximately 1 millimeter; the objective is to dissociate the metallic components from the non-metallic ones, thereby preparing the material for subsequent separation.

Step 3: Sorting

Following the crushing process, a mixed powder of metallic and non-metallic materials is obtained; separation is primarily achieved through physical methods that exploit differences in properties such as density, electrical conductivity, and magnetism. The main techniques include:

♻️Magnetic Separation:

Extracts ferromagnetic substances (e.g., iron, nickel); capable of separating only magnetic metals.

♻️Eddy Current Separation:

Utilizes an alternating magnetic field to induce eddy currents in non-ferrous metals (e.g., copper, aluminum), causing them to be repelled and separated from plastics and fibers; this method is suitable for materials with regular shapes and larger particle sizes.

♻️Electrostatic Separation:

Exploits differences in electrical conductivity to separate metallic particles from non-metallic particles within a high-voltage electrostatic field; frequently employed for the further purification of fine-grained materials.

♻️Air Classification:

Leverages density differences to separate lightweight non-metallic particles from heavier metallic particles through the action of an airflow.

♻️Hydraulic Separation:

Achieved through the use of hydraulic shaking tables and density differences. Although this method offers high recovery rates, it entails high costs and necessitates the installation of a corresponding water treatment system to prevent secondary pollution.

Following the sorting process, two categories of materials are produced:

♻️Metal Concentrates:

Containing copper, aluminum, iron, and trace amounts of gold, silver, palladium, etc. The metal recovery rate exceeds 90%, with certain processes achieving rates as high as 99%.

♻️Non-metallic Powder:

Consisting primarily of glass fibers and resins.

Furthermore, the dust removal system achieves an efficiency of over 99%.

Step 4: Metal Refining & Extraction

The metal-rich concentrates obtained through physical separation require further purification, primarily utilizing chemical or thermal treatment methods.

♻️ Copper Recovery (The largest component, accounting for approximately 20–30%)

Pyrometallurgy:

Following smelting, electrolysis is performed to yield electrolytic copper with a purity exceeding 99.9%.

Hydrometallurgy:

The material is leached using sulfuric acid, followed by solvent extraction and electrowinning to produce cathode copper.

♻️ Precious Metal Recovery (Gold, Silver, Palladium)

Although the content of precious metals is low, their value is exceptionally high. One ton of standard circuit boards contains approximately 200 grams of gold (40 times the grade of typical gold ore), while one ton of mobile phone circuit boards can yield as much as 2 kilograms.

♻️Hydrometallurgy:

Solvents are used to dissolve the precious metals; the metals are then recovered via activated carbon adsorption or zinc powder displacement to produce “gold mud,” which is finally refined into gold ingots.

♻️Pyrometallurgy:

Heating and smelting are employed to separate the metals from impurities.

♻️Electrolysis:

High-purity metals are obtained through electrolytic deposition.

Currently, advanced technologies can boost the recovery rate of precious metals to over 99%, thereby achieving a near-zero-waste process.

Step 5: Non-Metallic Material Processing

Non-metallic materials (primarily glass fibers and resins) constitute approximately 60% to 70% of a circuit board’s composition. There are four primary methods for processing these materials:

♻️Utilization in Building Materials:

Serving as a filler in concrete to enhance structural strength, or being mixed with resins and compressed into engineered panels.

♻️Composite Materials:

Blending with plastics to produce recycled granules—achieving a purity level exceeding 98%—which are then utilized in products such as appliance casings and automotive interior components.

♻️Pyrolysis Treatment:

Decomposing the resins at high temperatures within an oxygen-free environment to generate combustible gases and pyrolysis oils; the residual glass fibers are subsequently ground down for use as fillers.

If you require the recycling and disposal of PCBs, Gomine possesses a wide range of equipment capable of processing such electronic waste. You are welcome to contact us at any time.