PCBA Tech - About details and advantages that SMT is easy to overlook

Details that are easily overlooked in SMT patch processing

In the SMT patch manufacturing plant, it is generally easy to ensure the purposeful practical operation safety performance of the SMT placement machine. In the actual operation of the SMT placement machine, not only must have experienced technical professional technical personnel and working experience who have experienced professional ability training and learning. The technical personnel of the company come to cooperate in the actual operation of the machinery and equipment. Therefore, to ensure the high credibility and straight-through rate of the SMT patch. The scrap rate of arc welding and electric welding. High-quality high-frequency characteristics. Reduce the magnetic effect of a current and the hazard of radio frequency signals. It is easy to carry out automatic control and improve production efficiency.

The general management stipulates that the temperature of the production line of the SMT chip processing factory is in the middle of 25±3°C. The relative density of SMT patch is high, and the electronic equipment is small in size and light in weight. The volume size and net weight of SMT patch electronic devices are only half or even one-tenth of that of traditional plug-in electronic devices. After the SMT patch processing is generally selected, the overall volume of the electronic equipment will be reduced by 40%~60% and the net weight will be reduced by 60%~80% under the relative action conditions.

When facilitating solder paste packaging and printing, a special tool for pasting raw materials, steel leaves, wiping cloth, cyclone into detergent, and mixing knife must be prepared in advance.

In SMT chip processing plants, most of the companies' common solder paste aluminum alloy key components are Sn/Pb aluminum alloy, and the proportion of aluminum alloy development is 63/37. The main components of soldering materials are pasted into two parts, tin powder and flux. The flux is mainly capable of reasonably removing metal oxides, destroying the surface layer of molten tin to develop support and avoiding air oxidation again.

The volume ratio of tin powder particles to the flux solution in the SMT patch processing flux paste is about 1:1, and the net weight ratio is about 9:1. In SMT production and processing, the solder paste must be used after the actual operation of unfreezing and heating and mixing before application. The heating cannot be carried out according to the heating method of the application. One stage that is easily overlooked in PCBA manufacturing is the storage of BGA and IC chips. The storage of integrated ICs must be packaged and stored in a dry natural environment to maintain the dryness and oxidation resistance of key electronic devices.

Advantages of SMT chip processing technology

SMT surface assembly technology is also more perfect, and the role of machinery and equipment is gradually improving. SMT patch production and processing technology has slowly replaced traditional plug-in technology and has become a more popular processing technology in the electronic device assembly manufacturing industry. "Smaller, lighter, denser and stronger" are the advantages of SMT chip production and processing technology, and it is also the requirement for high integration and miniaturization of current electronic products.

SMT chip processing process: first apply solder paste on the surface of the printed circuit board pad, then accurately place the metalized terminals or pins of the component on the solder paste of the pad, and then connect the printed circuit board to the component Put them together in a reflow oven and heat the solder paste as a whole. After cooling and solidification of the solder paste, the mechanical and electrical connections between the components and the printed circuit are realized.

Let's talk to the Xunde technicians to understand the advantages of SMT chip processing technology.

1. 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.

2. High reliability and strong anti-vibration ability

SMT chip processing uses chip components with high reliability. The components are small and light, so it has strong anti-vibration ability. It adopts automated production and has high mounting reliability. Generally, the rate of bad solder joints is less than 10 parts per million. The wave soldering technology of through-hole plug-in components is one order of magnitude lower, which can ensure a low defect rate of solder joints of electronic products or components. At present, almost 90% of electronic products adopt SMT technology.

3. Good high frequency characteristics and reliable performance

Because the chip 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 high frequency of the circuit designed with SMC and SMD is up to 3GHz, while the chip component is 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 high-end 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) uses a vacuum nozzle to pick and place the components. The vacuum nozzle is smaller than the shape of the component, which increases the mounting density. In fact, small components and fine-pitch QFP devices are produced using automatic placement machines to achieve full-line automated production.

5. Reduce costs and reduce expenses

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

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

(3) As the frequency characteristic is improved, the circuit debugging cost is reduced;

(4) Due to the small size and light weight of chip components, packaging, transportation and storage costs are reduced;

(5) The use of SMT patch processing technology can save materials, energy, equipment, manpower, time, etc., and can reduce costs by 30% to 50%;