# Estimating Recycling Return of Integrated Circuits Using Computer Vision on Printed Circuit Boards
## 2 Background  
### Printed Circuit Board (PCB) and Integrated Circuit (IC) Recycling  
The PCB composition is complex, so the recycling process is arduous [7; 9]. A PCB comprises about 30% metallic components. Some of these are high-value metals like gold, silver, and copper. Even though these high-value materials are less than 1% of the PBC weight, it can represent 80% to 88% of the PCB recycling value [9; 15]. [PERSON] et al. [7] estimated that 1 ton of WPCBs contained approximately 284 g of gold.  
WPCB recycling processes are mainly interested in the recovery of those valuable metals. However, depending on the recycling process used, there are environmental problems with residues and hazardous substances resulting from the recycling process [17; 18].  
Usually, the WPCB recycling process involves three steps: dismantling, physical crushing or mechanical process, and some chemical leaching processes [9]. The dismantlingprocess aims to eliminate hazardous materials, gather components for reuse, and optimize the whole recycling process [18].  
Eco-friendly recycling usually involves some WPCB dismantling processes [9]. WPCBs dismantling can reduce metal loss, leading to maximum precious metal recovery. The WPCB dismantling process can be done manually, semi-automatically, or automatically [18].  
Some PCB recycling facilities perform crushing without dismantling the WPCB. This method reduces the human cost and protects the worker's health [18]. However, automatic dismantling can lead to cost-effective and sustainable WPCB recycling, especially if WPCBs are from different equipment types [19]. The current challenge of WPCB recycling is to achieve economic, environmental, and marketability viability [15]. For this purpose, a combination of several recycling techniques and a proper way to choose the recycling process may lead to an outcome that satisfies the market standard. For instance, even automatic disassembly adds a cost to the recycling process. Consequently, the outcomes of WPCB recycling can be improved by some methods to choose the recycling process such as when to dismantle a WPCB before shredding [15,18].  
Precious metals such as Au, Ag, and Pd are used as contact materials or as plating layers in ICs [18]. Therefore, recycling ICs can lead to a better recovery of these highly valuable metals, while the non-metallic parts can be recycled in another process [1]. [PERSON] and [PERSON] [20] describe a physical process to recycle ICs and recovery metallic values. This study gathered 500 kg of WPCBs from computers and laptops, from which 15 kg of ICs were removed mechanically or by desoldering. The authors proposed a physical separation recycling method comprised of grinding, screening, water fluidization, magnetic separation, and density separation. The recycling outcomes are reported in Table 1.  
Aside from physical separation, leaching is another approach for integrated circuit recycling [21]. The leaching process is applied after physical separation. [PERSON] at. al. reported 100% recovery of gold (Au), silver (Ag), and copper (Cu) with thiourea leaching [21].  
Considering recycling the entire WPCB, precious metals (Au, Pd, Pt, and Ag) are about 88% of the intrinsic value of the WPCB [15]. Most studies consider the recovery of these precious metals from printed circuit boards as a whole [15]. Although studies indicate the concentration of the precious metal in integrated circuits, the percentage of the integrated circuit mass corresponding to precious metals is challenging [21]. This measurement difficulty occurs because the concentration of precious metals is small, and there is a considerable variation in concentration depending on the sample of the ICs.