How is the chip welded to the circuit board?

The chip is what we call IC, which is composed of the crystal primitive and the outer package, as small as a triode. Our computer CPU is what we call IC, which is generally installed on the PCB (printed circuit board) through the pin, which is divided into different volume packages, there are in-line, there are patches. There are also not directly installed on the PCB, such as our computer CPU, in order to replace the convenience, it is fixed on the socket or pin press form, there is a chip, such as we said, is seen before a black knot, such as the electronic watch inside, they are directly fixed on the PCB board. For example, some electronics enthusiasts do not have a suitable PCB, so directly from the pin line out of the shed can also be.

The chips are "attached" to the circuit board, or "welded" to be precise. The chips are welded to the circuit board by soldering, and the circuit board is "wired" to establish the electrical connection between the chips. The circuit board is the carrier of components, which not only fixes the chip but also ensures the electrical connection to ensure the stable work of each chip.

The pin of the chip

The chip has many pins, through which the chip and other chips, components, circuits establish electrical connection. The more functions the chip has, the more pins it has. According to the different pin out form, can be divided into LQFP series package, QFN series package, SOP series package, BGA series package and DIP series of in-line package. As shown in the picture below.

PCB circuit board

The common circuit board is generally with green oil, called PCB board, in addition to green, commonly used colors and blue, black, red, etc. PCB board has welding pad, routing, and hole, etc. The arrangement of the pad is consistent with the package of the chip, and the chip and the pad can be welded together by the solder; The wiring and through-hole provide electrical connections. The PCB board is shown in the following figure.

PCB board can be divided into double layer board, four layer board, six layer board, or even more layers according to the number of layers. Commonly used PCB board is FR-4 material, commonly used thickness of 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm and so on. This is a hard circuit board, there is a soft, called flexible circuit board, such as mobile phone, computer kind of soft line is flexible circuit board.

Welding tool

To weld a chip, you need a welding tool. If it is manual welding, it is necessary to use electric iron, solder wire, flux and other tools. Manual welding is suitable for a small number of samples, not suitable for mass production welding, because of low efficiency, poor consistency, leakage welding and other problems. Now the degree of mechanization is getting higher and higher, and SMT patch components welding is a very mature standardized industrial process, this process will involve tin-brushing machine, patch machine, reflow furnace, AOI testing and other equipment, the degree of automation is very high, the consistency is very good, the error rate is very low, to ensure the mass shipment of electronic products. SMT can be said to be the infrastructure industry of the electronics industry.

Basic process of SMT

SMT is a standardized industrial process, involving PCB circuit board and incoming material inspection, SMT machine material, solder paste/red glue, SMT machine material, over reflux furnace, AOI testing, cleaning and other processes. Any link can not be wrong, the incoming material check link mainly ensures the correctness of the material, the placement machine needs to be programmed to determine the position and direction of each component, the solder paste is applied to the solder paste on the PCB pad through the steel mesh, reflow welding is the process of melting the solder paste, AOI is the detection process.

The chip is to be welded on the circuit board, the circuit board can not only play the role of fixing the chip but also ensure the electrical connection between the chips.