EMZETT.Circuit Boards
In short: Printed circuit boards (PCBs), on which electronic components are mounted and electrically connected via printed traces.
In more detail: Almost every computer component — motherboard, graphics card, expansion card — is at its core a circuit board with soldered-on chips. Multi-layer boards (several copper layers stacked on top of each other) enable more complex circuits in a smaller space.
In Depth
Manufacturing process
A circuit board is created by selectively etching away a thin copper layer on a carrier material (usually glass-fibre-reinforced epoxy resin, known by the material designation FR4), so that only the desired traces remain as copper. The process begins with a light-sensitive protective layer (photoresist), which is exposed exactly according to the desired trace pattern; unexposed areas are then chemically etched away, leaving only the protected copper traces. These traces take on the function that loose hanging wires used to have, just immovably fixed, extremely precisely positioned and mass-producible. Electronic components (chips, capacitors, resistors) are then applied to the board in a solder oven (reflow soldering) and electrically connected to each other via these traces.
Multi-layer boards
For simple circuits, a single copper layer on each side of the board (single- or double-sided) is enough; for complex components like a motherboard with thousands of connections, by contrast, multi-layer boards with eight or more stacked copper layers separated by insulating layers are common — only this way can the enormous connection density be fitted into a limited area, without traces crossing and short-circuiting each other. Connections between different layers run via so-called vias — tiny holes drilled through all relevant layers and lined with copper, acting like a vertical wire between the horizontal trace layers.
Signal integrity at high frequencies
The number of layers, the quality of the copper and the precision of manufacturing directly affect how high a frequency and how much electrical power a board can reliably transmit. At very high data rates (modern PCIe standards, fast RAM), the board itself becomes a critical electrical component: traces behave like small antennas at high frequencies and can radiate signals or interfere with neighbouring traces (crosstalk), which is why certain pairs of signal traces often have to be specifically routed with exactly equal length and a defined distance from each other, to minimise signal distortion.
Special construction types
Besides the rigid standard boards, there are also flexible boards (made of bendable polyimide instead of rigid FR4), which adapt to curved case shapes — common in smartphones and other compact devices, where rigid boards wouldn’t make optimal use of the available space. Hybrid forms (rigid-flex) combine both properties in a single board with rigid and flexible sections.
See also: Motherboard/Mainboard