Explained
How a laptop works.
What's inside a laptop
A modern thin laptop is mostly battery. Flat lithium-ion cells fill the bottom of the case, and the logic board, processor and cooling system are squeezed into a strip near the hinge. On top sits the top case with the keyboard and trackpad, and the display lives in the lid. The model here is generic and unbranded, but the layout is common across thin laptops.
The logic board joins everything together. The processor sits in the middle, with memory either on the same package or beside it on the board. Storage is soldered flash memory or a removable SSD. Ports, speakers and the keyboard all connect to the board with flat flex cables.
Keeping it cool
The processor turns electrical power into heat, and it has to lose that heat to keep running fast. A copper heat pipe is pressed against the chip. Inside the sealed pipe a small amount of liquid soaks a wick. At the hot end the liquid boils, the vapour rushes to the cooler end and condenses, and the liquid creeps back through the wick. This cycle moves heat far better than a solid copper bar of the same size.
At the far end of the pipe are thin metal fins and a blower fan that pushes air through them and out of the vents. Some very thin laptops have no fan at all and spread the heat into the case instead. They stay silent but slow down sooner under heavy work.
Keyboard, trackpad and hinge
Each key press closes a circuit in a grid of rows and columns, and a controller scans the grid many times a second to see which keys are down. The trackpad is a capacitive sensor under a glass surface. Some trackpads do not physically click at all: a haptic motor taps the glass so it feels like a click.
The hinge is a friction hinge. It is stiff enough to hold the screen still while you type but light enough to open with one finger. Cables for the display and the antennas run through it. Open Play to swing the lid open and closed, then look inside, or remove each layer in turn.
Parts glossary
- Display
- An LCD or OLED panel fills the lid, with its cables routed through the hinge to the logic board.
- Lid
- The aluminium lid protects and stiffens the screen. Its antennas often sit near the hinge.
- Hinge
- A friction hinge holds the screen at any angle but still lets it open with one finger.
- Keyboard
- Each key sits on a small mechanism over a membrane or switch layer. Pressing a key completes a circuit that the keyboard controller scans.
- Trackpad
- A glass surface over a capacitive sensor tracks your fingers. Some trackpads use haptic motors to fake the feel of a click.
- Top case
- The top case carries the keyboard and trackpad and closes the inside of the machine.
- Processor
- The main chip combines CPU cores, graphics and memory controllers. It makes most of the laptop's heat.
- Logic board
- The board connects the processor to memory, storage, ports and power. In thin laptops it is small and densely packed.
- Heat pipe and fan
- A copper heat pipe carries heat from the chip to fins, and a blower fan pushes air through them and out of the vents. Fun fact: Inside a heat pipe, liquid boils at the hot end and the vapour condenses at the cool end, carrying heat far better than solid copper.
- Speakers
- Sealed speaker boxes sit either side of the keyboard.
- Battery cells
- Several flat lithium-ion cells are wired together and fill most of the bottom of the case.
- Ports
- USB-C and other connectors carry charging power, data and video.
- Bottom case
- A single aluminium plate closes the bottom, with rubber feet and vents.
