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PCB Tech
SMT surface mount technology-how your phone is produced
PCB Tech
SMT surface mount technology-how your phone is produced

SMT surface mount technology-how your phone is produced


Mobile phones, computers, tablets and other electronic devices are an indispensable part of life for people nowadays. In the process of using them, will there be a question in your mind? That is how the electronic devices in our hands are made? from?

Next, we will introduce a technology used in the production of all electronic devices-surface-mount technology (SMT, surface-mount technology).

In simple terms, SMT is to print solder paste on a fixed point on a PCB circuit board, then mount resistors, capacitors and other components on the surface of the circuit board through machinery and equipment, and then bake the circuit board at a high temperature to make the solder paste Curing, so that the components are firmly soldered to the circuit board to form a complete circuit board assembly.

Among them, the SMT production line is mainly composed of the following equipment: solder paste printer, solder paste inspection equipment (SPI, Solder Paste Inspection), placement machine, AOI (Automated Optical Inspection), reflow oven, upper and lower board machines, and Barge equipment, rework station and other equipment.

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Among them, solder paste printers, placement machines, and reflow ovens belong to the processing equipment, SPI and AOI belong to the inspection equipment, and the upper and lower board machines, connection equipment, rework stations and other auxiliary equipment.

Usually a SMT production line is constructed in the order of the upper board machine-solder paste printer-solder paste inspection equipment (SPI)-placement machine-front AOI-reflow oven-back AOI-rework station-lower board machine , Interspersed with single-track or double-track transmission and connection equipment.

Solder paste printer: Place the solder paste on the designed stencil, and use the robot arm to control the scraper to scrape the solder paste from one end to the other end of the stencil. The solder paste will leak out of the stencil holes laid out on the stencil. Drop onto the corresponding position of the PCB board under the stencil.

Solder Paste Inspection Equipment (SPI): Detect the quality of solder paste after printing through optical principles to prevent problems such as missing printing, less tin, more tin, continuous tin, misalignment, poor shape, and board surface contamination.

Mounter: Pick up the components and materials through the suction nozzle, and paste the materials on the PCB surface at the correct position by controlling the mechanical arm.

AOI: Through the optical inspection of the component placement, whether there will be displacement, leakage, polarity, skew, wrong parts, etc., after reflow soldering, detect whether there is less tin, more tin, displacement, and poor shape And other issues.

Reflow oven: divided into different temperature zones, heated by hot air or infrared radiation, so that the temperature of different temperature zones in the furnace is gradient, when the PCB board passes through the furnace, the solder paste will solidify due to the increase in temperature.

Board loading and unloading machine, connecting equipment: equipment used to transfer PCB boards.

Rework station: It has the basic function of heating and is used for manual inspection of PCB boards that have been reworked and soldered.

The application of SMT is too extensive. For example, the smart phones that everyone holds now are circuit boards produced through this process, and then through the assembly process of the whole machine, the circuit boards, cameras, and thermal conductive glue are used. Adhesive glue, screen and other materials are assembled into a mobile phone. Companies including Foxconn, Huawei, OPPO, VIVO, Xiaomi, BYD and other companies have their own SMT lines, and these large electronics manufacturers also have many foundries. For example, Foxconn is Apple's most well-known foundry.

Although the current SMT is very mature, it also faces the following problems:

1. The accuracy of the equipment cannot reach 100%, and errors will still occur, causing the soldered PCB board to be scrapped;

2. Manual intervention, verification and repair of equipment are required;

3. There is a risk of aging and damage to complex and precise parts, leading to the risk of production line shutdown;

4. The data platforms of equipment from different manufacturers are not compatible with each other.

Therefore, the development trend of SMT production line in the future factory is very clear:

1. The device can perform closed-loop detection, which means that the device will perform in-depth learning and self-evolve through error processing to ensure that it will perform the correct processing in the same situation next time;

2. Everything is interconnected, and all equipment platforms are compatible, and will be connected with the enterprise's MES system to realize that one server can control several lines at the same time, and can adjust the distribution of production capacity and the transportation of materials in real time according to the data;

3. Monitoring of the core components of the equipment, such as adding a monitoring system to the hot air motor of the reflow furnace, which can monitor the operation of the motor in real time, and conduct manual intervention in time when an abnormality occurs;

4. Equipment early warning and foolproof function, electronic equipment, can not guarantee that the equipment will not appear line aging, short circuit and other phenomena. If once this phenomenon occurs, there is no early warning or foolproof function, which is for the production fire safety and the life safety of personnel. Great hidden danger. Therefore, all smart devices will be equipped with foolproof functions such as instant alarm when failure occurs, and the power supply will be shut off immediately when short circuit occurs;

5. Completely realize unmanned management, humans can be completely replaced by industrial robots and intelligent robots, all similar repairs, inspections and other processes are all completed by robots instead of humans. In the end, only a few people can take care of an entire SMT factory.