1. circuit board

PCB printed circuit board is an indispensable part of all computer boards. It is actually made of several layers of resin materials, and copper foil wiring is used inside. The general PCB circuit board is divided into four layers, the upper and lower layers are signal layers, and the middle two layers are grounding layer and power layer. Put the ground plane and the power plane in the middle, so that the signal line can be easily corrected. And some boards with higher requirements can reach 6-8 layers or even more.

How is the motherboard (circuit board) made? The manufacturing process of PCB is to use glass epoxy resin (glass

Epoxy) or similar material. The first step in manufacturing is to draw the connection lines between parts. The method is to "print" the circuit negative of the designed PCB on the metal conductor through negative transfer.

This technology is to spread a thin layer of copper foil on the whole surface to eliminate the redundant parts. And if the production is a double panel, then both sides of the PCB substrate will be covered with copper foil. To make a multilayer board, two double panels can be "pressed" together with a special adhesive. Next, drilling and electroplating required for connecting components can be carried out on the PCB. After the machines and equipment are drilled according to the drilling requirements, the inner side of the hole wall must be electroplated (PTH). After metal treatment in the hole wall, the inner circuits can be connected with each other.

Impurities in the holes must be removed before electroplating. This is because the epoxy resin will produce some chemical changes after heating, which will cover the internal PCB layer, so it should be removed first. Cleaning and electroplating actions will be completed in the chemical process. Next, it is necessary to cover the outermost wiring with solder resist paint (solder resist ink) so that the wiring will not touch the electroplated part.

Then, labels of various components are screen printed on the circuit board to indicate the position of each component. It cannot cover any wiring or gold fingers, otherwise it may reduce solderability or the stability of current connection. In addition, if there is a metal connection part, the "golden finger" part is usually plated with gold to ensure high-quality current connection when inserted into the expansion slot.

Finally, it is a test. Test PCB for short circuit or open circuit, which can be tested by optical or electronic means. Optical scanning is used to find out the defects of each layer, while electronic testing usually uses flying needles to check all connections. Electronic testing is more accurate in finding short circuits or open circuits, but optical testing can more easily detect the problem of incorrect gaps between conductors.

After the completion of the circuit board substrate, a finished motherboard installs various components, large and small, on the PCB substrate as required-first, the IC chip and the component are "soldered" with an SMT automatic mounter, and then some work that the machine can't do is manually plugged in, and these plugged-in components are firmly fixed on the PCB through the wave soldering/reflow soldering process, so that a motherboard is produced.

In addition, if the circuit board wants to be the main board on the computer, it needs to be made into different boards. Among them, AT board is the most basic board, which is characterized by simple structure and low price. Its standard size is 33.2cmX30.48cm, and the AT motherboard needs to be used with the power supply of the AT chassis, which has been eliminated. The atX board is like a large horizontal AT board, which is convenient for the fan of the ATX chassis to dissipate heat to the CPU, and many external ports on the board are integrated on the motherboard, unlike many COM ports and printing ports on the AT board, which are output by wiring. In addition, ATX also has a miniature ATX small board, which can support up to four expansion slots, reducing the size, power consumption and cost.

2. North Bridge Chip

Chipset is the core component of the motherboard, which is usually divided into north bridge chip and south bridge chip according to the different arrangement positions on the motherboard. For example, Intel's i845GE chipset consists of 82845GE GMCH north bridge chip and ICH4(FW8280 1DB) south bridge chip. VIA KT400 chipset consists of KT400 north bridge chip and VT8235 south bridge chip (there are also single-chip products, such as SIS630/730, etc. ), in which the north bridge chip is the main bridge, which can generally cooperate with different south bridge chips to achieve different functions and performances.

Northbridge chip generally provides support for CPU type and main frequency, memory type and maximum capacity, ISA/PCI/AGP slot, ECC error correction, etc. They are usually located on the motherboard near the CPU slot. Because this chip has a high calorific value, a radiator is installed on this chip.

3. South Bridge Chip

Southbridge chip is mainly used to connect I/O devices and ISA devices, and is responsible for managing interrupts and DMA channels, which makes the devices work more smoothly. It supports KBC (Keyboard Controller), RTC (Real-time Clock Controller), USB (Universal Serial Bus), Ultra DMA/33(66)EIDE data transmission mode and ACPI (Advanced Energy Management). It is located near the PCI slot.

4.CPU socket

The CPU socket is where the processor is installed on the motherboard. The mainstream CPU sockets mainly include Socket370, Socket 478, Socket 423 and Socket A. Socket370 supports processors such as PIII, New Celeron and CYRIXIII. The early Pentium 4 processor used Socket 423, while the current mainstream Pentium 4 used Socket 478.

Processor.

Socket A(Socket462) supports AMD's processors such as Duron and Athlon. In addition, the CPU socket type is Socket7 socket, which supports Pentium/Pentium MMX and K6/K6-2 processors. SLOT 1 slot supports PII or PIII and AMD.

SLOTA socket for ATHLON and so on.

5. Memory slot

The memory slot is where the memory is installed on the motherboard. At present, the common memory slots are SDRAM memory and DDR memory slots, and others are early EDO and non-mainstream RDRAM memory slots. It should be noted that different memory slots have different pin, voltage and performance functions, and different memories cannot be used interchangeably in different memory slots. For SDRAM memory with 168 line and DDR SDRAM memory with 184 line, the main difference in appearance is that there are two gaps on the gold finger of SDRAM memory, while DDR SDRAM memory has only one.

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