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Valuable Substances in e-waste

Electrical and electronic equipment contain various fractions of valuable materials. Most of the valuable substances are found in printed circuit boards, which occur in relevant quantities mainly in the categories Office, Information and Communication Equipment as well as Entertainment and Consumer Electronics. Besides well known precious metals such as gold, silver, platinum and palladium also scarce materials like indium and gallium start to play an important role, due to their application in new technologies (e.g flat screens, photovoltaics).

 

The following table presents the composition of a desktop computer plus a CRT screen in 1996. More than 80% of the weight consists of silica (glass), plastics, iron and aluminium. Precious and scarce materials account for only a small percentage of the total weight. Nevertheless, the concentration of such metals, e.g. gold, is higher in a desktop computer than found in naturally occurring mineral ore.

Composition of a Desktop Personal Computer Based on a typical desktop computer, weighing ~27 kg

Material name Content (% of total weight) Weight of material in computer (kg) Use Location
Plastics 22.9907 6.26 Insulation Cable, Housing
Lead 6.2988 1.72 Metal joining Funnel glass in CRTs, PWB
Aluminum 14.1723 3.86 Structural, Conductivity Housing, CRT, PWB, connectors
Germanium 0.0016 < 0.1 Semiconductor PWBs
Gallium 0.0013 < 0.1 Semiconductor PWBs
Iron 20.4712 5.58 Structural, Magnetivity Housing,CRTs, PWBs
Tin 1.0078 0.27 Metal joining PWBs, CRTs
Copper 6.9287 1.91 Conductivity CRTs, PWBs, connectors
Barium 0.0315 < 0.1   Panel glass in CRTs
Nickel 0.8503 0.23 Structural, Magnetivity Housing, CRT, PWB
Zinc 2.2046 0.6 Battery, Phosphor emitter PWB, CRT
Tantalum 0.0157 < 0.1 Capacitor Capacitors/PWB, power supply
Indium 0.0016 < 0.1 Transistor, rectifier PWB
Vanadium 0.0002 < 0.1 Red Phosphor emitter CRT
Terbium 0 0 Green phosphor activator, dopant CRT, PWB
Beryllium 0.0157 < 0.1 Thermal Conductivity PWB, connectors
Gold 0.0016 < 0.1 Connectivity, Conductivity Connectivity, conductivity/PWB, connectors
Europium 0.0002 < 0.1 Phosphor activator PWB
Titanium 0.0157 < 0.1 Pigment, alloying agent Housing
Ruthenium 0.0016 < 0.1 Resistive circuit PWB
Cobalt 0.0157 < 0.1 Structural, Magnetivity Housing, CRT, PWB
Palladium 0.0003 < 0.1 Connectivity, Conductivity PWB, connectors
Manganese 0.0315 < 0.1 Structural, Magnetivity Housing, CRT, PWB
Silver 0.0189 < 0.1 Conductivity Conductivity/PWB, connectors
Antinomy 0.0094 < 0.1 Diodes Housing, PWB, CRT
Bismuth 0.0063 < 0.1 Wetting agent in thick film PWB
Chromium 0.0063 < 0.1 Decorative, Hardner Housing
Cadmium 0.0094 < 0.1 Battery, blue-green Phosphor emitter Housing, PWB, CRT
Selenium 0.0016 0.00044 Rectifiers rectifiers/PWB
Niobium 0.0002 < 0.1 Welding Housing
Yttrium 0.0002 < 0.1 Red Phosphor emitter CRT
Rhodium 0   Thick film conductor PWB
Platinum 0   Thick film conductor PWB
Mercury 0.0022 < 0.1 Batteries, switches Housing, PWB
Arsenic 0.0013 < 0.1 Doping agent in transistors PWB
Silica 24.8803 6.8 Glass, solid state devices CRT,PWB


Source: Microelectronics and Computer Technology Corporation (MCC). 1996.
Electronics Industry Environmental Roadmap. Austin, TX: MCC.
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