A collection of difficulties and solutions in the SMT assemb

News     |      2021-10-11 10:32

Abstract: Surface mount technology, also known as the SMT assembly process, is a kind of electronic assembly process, which originated in the 1960s. It was originally developed by IBM in the United States and gradually matured in the late 1980s. This technology is to mount PCB components, such as resistors, capacitors, transistors, integrated circuits, etc., on a printed circuit board and form electrical connections through soldering. The components used are also referred to as surface mount components.

 

Table of content:

1 High reliability and strong anti-vibration ability

2 Electronic products are small in size and high in assembly density

3 Good high-frequency characteristics and reliable performance

4 Improve productivity and realize automated production

5 Reduce costs and reduce expenses

 

The big difference between SMT and through-hole insertion technology is that the SMT assembly process does not need to reserve corresponding through holes for component pins, and the component size of surface mount technology is much smaller than that of through-hole insertion technology. The overall processing speed can be increased by applying surface mount technology, however, due to the miniaturization of parts and the increase in density, the risk of circuit board defects increases. Therefore, in the circuit board manufacturing process of any surface mount technology, error detection has become A necessary part.

  PCB components

      The advantages of SMT chip processing technology:

   1. High reliability and strong anti-vibration ability

The SMT assembly process uses chip-shaped PCB components, which have high reliability, small and light components, so strong vibration resistance, automatic production, high mounting reliability, and the general bad solder joint rate is less than ten parts per million. The wave soldering technology of through-hole plug-in components is one order of magnitude lower, which can guarantee the low defect rate of solder joints of electronic products or PCB components. At present, almost 90% of electronic products adopt the SMT process.

 

   2. Electronic products are small in size and high in assembly density

The volume of SMT chip components is only about 1/10 of the traditional plug-in components, and the weight is only 10% of the traditional plug-in components. Usually, the use of SMT technology can reduce the volume of electronic products by 40%~60% and the quality by 60%~80 %, the occupied area and weight are greatly reduced. The SMT patch processing assembly component grid has developed from 1.27MM to the current 0.63MM grid, and individual grids have reached 0.5MM. The through-hole mounting technology is used to install the components, which can make the assembly density higher.

 

   3. Good high-frequency characteristics and reliable performance

   Because the chip PCB components are firmly mounted, the devices are usually leadless or short leads, which reduces the influence of parasitic inductance and parasitic capacitance, improves the high-frequency characteristics of the circuit, and reduces electromagnetic and radio frequency interference. The ultra-high frequency of the circuit designed by SMC and SMD is up to 3GHz, while the chip component is the only 500MHz, which can shorten the transmission delay time. It can be used in circuits with a clock frequency above 16MHz. If the MCM technology is used, the clock frequency of the computer workstation can reach 100MHz, and the additional power consumption caused by parasitic reactance can be reduced by 2-3 times.

 

  4. Improve productivity and realize automated production

   At present, if the perforated printed board is to be fully automated, it is necessary to expand the area of ​​the original printed board by 40% so that the insertion head of the automatic plug-in can insert the components. Otherwise, there is not enough space and the parts will be damaged. The automatic placement machine (SM421/SM411) adopts a vacuum nozzle to suck and release the components. The vacuum nozzle is smaller than the shape of the component, which increases the installation density. In fact, small components and fine-pitch QFP devices are produced by automatic placement machines to achieve full-line automated production.

 SMT assembly process

   5. Reduce costs and reduce expenses 

   (1) The use area of ​​the printed board is reduced, the area is 1/12 of the through-hole technology, if the CSP is used for installation, the area will be greatly reduced;

   (2) The number of holes on the printed circuit board is reduced, saving repair costs;

   (3) As the frequency characteristics are improved, the circuit debugging costs are reduced;

   (4) Due to the small size and lightweight of chip PCB components, the cost of packaging, transportation, and storage is reduced;

 

The use of the SMT assembly process can save materials, energy, equipment, manpower, time, etc., and can reduce costs by 30% to 50%.

 

Kingford Technology is a company specializing in electronic product design, electronic program development, and electronic product PCBA processing. The main design electronic products include industrial control, automobile, power supply, communication, security, and medical electronic product development. The company’s core business is to provide one-stop PCBA services for the design, program development, and processing of electronic products in industrial control electronics, automotive electronics, medical electronics, security electronics, consumer electronics, communication electronics, power electronics, and other fields, to meet different customers. We can provide PCBA processing in small and medium batches on demand. The company’s products cover industrial production equipment control equipment electronic development, automotive MCU electronic control system program design, servo control board PCBA processing, CNC machine tool motherboard PCBA processing, smart home electronics research and development, 3D printer control board PCBA processing, and other fields. The business process includes electronic program development and design, PCB production, component procurement, SMT chip processing, prototype production and debugging, PCBA small and medium batch processing and production, and one-stop PCBA processing services for post-quality assurance and maintenance.