Electronics are built from a surprisingly wide range of materials, from common metals like copper and tin to trace amounts of gold and rare earth elements. A single smartphone contains dozens of different substances, each chosen for specific electrical, structural, or thermal properties. Here’s what actually goes into the devices you use every day.
Circuit Boards: The Foundation
Nearly every electronic device contains at least one printed circuit board (PCB), the green (or sometimes black or blue) board that holds and connects all the components. The board itself is made from FR-4, a composite of woven fiberglass cloth bonded with flame-resistant epoxy resin. This material is strong, lightweight, electrically insulating, and resistant to catching fire.
Laminated onto one or both sides of that fiberglass panel is a thin layer of copper foil. The copper gets chemically etched into precise pathways called traces, which carry electrical signals between components. Copper is the material of choice because it conducts electricity extremely well and is relatively affordable. A complex board like the one inside your phone may have multiple layers of copper traces sandwiched between layers of fiberglass, all pressed together into a single compact unit.
Solder: The Glue That Connects Everything
Every component on a circuit board needs to be physically and electrically attached, and that’s the job of solder. Modern lead-free solder, the industry standard since lead was phased out for health reasons, is typically 96.5% tin, 3% silver, and 0.5% copper. This alloy melts at a predictable temperature, flows into joints, and hardens into a reliable electrical connection. Older electronics used a tin-lead mixture, which is one reason vintage devices are considered hazardous waste.
Batteries: Lithium and Its Partners
The rechargeable battery in your phone, laptop, or wireless earbuds is a lithium-ion cell, and lithium is just one of several key ingredients. The negative electrode (anode) is typically made of graphite, a form of carbon. The positive electrode (cathode) is where things get more complex, combining lithium with varying amounts of nickel, manganese, cobalt, and sometimes aluminum or iron.
Nickel increases energy density, which translates to longer battery life per charge. Manganese improves safety by helping prevent overheating. Cobalt boosts thermal stability, though manufacturers are actively trying to reduce cobalt content because it’s expensive and its mining raises serious ethical concerns. A popular alternative, lithium iron phosphate, trades some energy density for significantly better safety and longer lifespan. Between the electrodes sits a liquid electrolyte and a thin separator membrane that allows charged particles to flow while keeping the electrodes from touching.
Screens: Glass, Crystals, and Transparent Conductors
Modern displays rely on a material you can’t see even though it’s right in front of you: indium tin oxide (ITO). This compound, made from indium and tin oxides, has a rare combination of properties. It conducts electricity while remaining almost completely transparent, with roughly 89.5% of visible light passing through. That’s what makes touchscreens possible. Your finger changes the electrical field across the ITO layer, and the device registers where you touched.
The display glass itself is typically a chemically strengthened aluminosilicate, a blend of aluminum, silicon, and oxygen that’s been treated in a chemical bath to resist scratching and shattering. Behind the glass, the actual image comes from either liquid crystals manipulating a backlight (LCD) or individual organic compounds that emit their own light (OLED). OLED screens use thin layers of carbon-based molecules deposited onto the glass substrate.
Capacitors, Resistors, and Tiny Components
A circuit board is populated with hundreds or thousands of small components, each made from different materials chosen for specific electrical behaviors. Ceramic capacitors, the most common type, use barium titanate or similar ceramic materials as their core. These ceramics store and release electrical energy rapidly. Tantalum capacitors use tantalum pentoxide as their core material, valued for its high ability to store charge in a small space. Tantalum is a dense, corrosion-resistant metal mined primarily in central Africa.
Resistors control the flow of current and are often made from carbon film, metal film, or metal oxide deposited onto a ceramic rod. Semiconductors, the chips that do the actual computing, are built on wafers of ultra-pure silicon, one of the most abundant elements on Earth. The silicon is precisely “doped” with tiny amounts of other elements like boron or phosphorus to control how electricity moves through it.
Precious and Rare Earth Metals
Electronics contain small but meaningful amounts of precious metals. A typical smartphone holds around 0.034 grams of gold, 0.34 grams of silver, 0.015 grams of palladium, and less than one-thousandth of a gram of platinum. Those numbers sound tiny, but multiplied across billions of devices produced each year, the totals are substantial. Gold is used for connector plating because it resists corrosion and maintains reliable contact. Silver appears in solder points and switch contacts. Palladium shows up in capacitors and connector plating.
Rare earth elements play critical roles too. Neodymium is the key ingredient in the powerful, compact magnets used in speakers, vibration motors, and camera autofocus systems. Other rare earths like gadolinium, praseodymium, and lanthanum appear in various components including phosphors (the materials that produce colored light) and certain types of batteries. Despite the name, rare earth elements aren’t especially rare in the Earth’s crust, but they’re difficult to extract and process, and production is concentrated in a small number of countries.
Housings and Structural Materials
The exterior of a device is usually aluminum, plastic, glass, or some combination. Premium phones and laptops favor machined aluminum alloy for its strength-to-weight ratio and ability to dissipate heat. The back panels of many smartphones use the same type of strengthened glass as the screen. Budget devices often use polycarbonate, a tough, lightweight plastic that can be molded into complex shapes. Internal structural pieces, brackets, and shielding cans are typically stamped from thin stainless steel or aluminum.
Cables and connectors add their own material mix. The wires inside are copper, often plated with gold or nickel at the contact points. Cable insulation is usually PVC or thermoplastic elastomer. USB connectors contain a small PCB of their own, with the same fiberglass, copper, and solder found inside the device.
Hazardous Materials in Electronics
Electronics also contain substances that are harmless during normal use but become dangerous when devices are improperly discarded. Brominated flame retardants are added to plastic housings and circuit boards to prevent fires, but they persist in the environment and accumulate in living organisms. Mercury appears in some types of backlit displays and certain switches. Cadmium shows up in older rechargeable batteries, some printer components, and the fluorescent coatings of old CRT screens. Lead, arsenic, and chromium are also present in various components, particularly in older devices manufactured before modern restrictions took effect.
This is why electronics recycling matters. When devices end up in landfills, these heavy metals and persistent organic pollutants can leach into soil and groundwater. Proper recycling recovers the valuable materials, including those precious metals, while safely containing the hazardous ones.