The chip is what we call IC, which is composed of crystal source and external packaging, as small as a transistor, and our computer CPU is what we call IC. Generally, it is installed on the PCB through pins (that is, The circuit board you mentioned), which is divided into different volume packages, including direct plug and patch. There are also ones that are not directly installed on the PCB, such as our computer CPU. For the convenience of replacement, it is fixed on it by means of sockets or pins. A black bump, such as in the electronic watch, is directly sealed on the PCB. For example, some electronic hobbyists do not have a suitable PCB, so it is also possible to build a shed directly from the pin flying wire.
The chip is to be “installed” on the circuit board, or “soldering” to be precise. The chip is to be soldered on the circuit board, and the circuit board establishes the electrical connection between the chip and the chip through the “trace”. The circuit board is the carrier of the components, which not only fixes the chip but also ensures the electrical connection and ensures the stable operation of each chip.
The chip has many pins, and the chip also establishes an electrical connection relationship with other chips, components, and circuits through the pins. The more functions a chip has, the more pins it has. According to the different pinout forms, it can be divided into LQFP series package, QFN series package, SOP series package, BGA series package and DIP series in-line package. As shown below.
Common circuit boards are generally green oiled, called PCB boards. In addition to green, commonly used colors are blue, black, red, etc. There are pads, traces, and vias on the PCB. The arrangement of the pads is consistent with the packaging of the chip, and the chips and the pads can be soldered correspondingly by soldering; while the traces and vias provide an electrical connection relationship. The PCB board is shown in the figure below.
PCB boards can be divided into double-layer boards, four-layer boards, six-layer boards, and even more layers according to the number of layers. The commonly used PCB boards are mostly FR-4 materials, and the common thicknesses are 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm, etc. This is a hard circuit board, and the other is a soft one, called a flexible circuit board. For example, flexible cables such as mobile phones and computers are flexible circuit boards.
To solder the chip, a soldering tool is used. If it is manual soldering, you need to use electric soldering iron, solder wire, flux and other tools. Manual welding is suitable for a small number of samples, but not suitable for mass production welding, because of low efficiency, poor consistency, and various problems such as missing welding and false welding. Now the degree of mechanization is getting higher and higher, and SMT chip component welding is a very mature standardized industrial process. This process will involve brushing machines, placement machines, reflow ovens, AOI testing and other equipment, and the degree of automation is very high. , The consistency is very good, and the error rate is very low, which ensures the mass shipment of electronic products. SMT can be said to be the infrastructure industry of the electronics industry.
The basic process of SMT
SMT is a standardized industrial process, which involves PCB and incoming material inspection and verification, placement machine loading, solder paste/red glue brushing, placement machine placement, reflow oven, AOI inspection, cleaning and other processes. No mistakes can be made in any link. The incoming material check link mainly ensures the correctness of the materials. The placement machine needs to be programmed to determine the placement and direction of each component. The solder paste is applied to the pads of the PCB through the steel mesh. Upper and reflow soldering is the process of heating and melting solder paste, and AOI is the inspection process.
The chip is to be soldered on the circuit board, and the circuit board can not only play the role of fixing the chip but also ensure the electrical connection between the chips.
Post time: May-09-2022