The advantages of SMT packaging and PCB substrate materials

2021-11-10

Author：Downs

The advantages of SMT chip processing packaging over traditional packaging

1. Electronic equipment is small in size and relatively high in installation density

The size of SMT chip electronic components is only about 10% of traditional packaged electronic components, and the quality is only 10% of traditional plug-in electronic components. SMT technology can generally reduce the size of electronic equipment by 40% to 60%, reduce the mass by 60% to 80%, and greatly reduce the area and mass. The grid of SMT chip processing and mounting electronic components has developed from 1.27mm to 0.63mm grid so far, and some have reached 0.5mm grid. Using through-hole installation technology can increase the relative density of installation.

2. High reliability and strong anti-vibration ability

SMT chip processing uses chip components, which have high reliability, small size, light texture, strong anti-vibration ability, automated production, high installation reliability, and the rate of bad solder joints is usually less than 10 parts per million. The wave soldering technology of through-hole plug-in electronic components is one order of magnitude lower, which can ensure the low defect rate of solder joints of electronic equipment or components. So far, nearly 90% of electronic equipment uses 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 maximum frequency of the circuit designed by using SMC and SMD can reach 3 GHz, while the chip electronic component is only 500 MHz, which can shorten the transmission delay time. It can be used in circuits with a clock frequency above 16MHz. If the MCM technology is selected, the high-end clock frequency of the computer workstation can reach 100 MHz, and the additional power consumption caused by parasitic reactance can be greatly reduced by 2-3 times.

PCB

4. Improve productivity and realize automated production

So far, to realize the complete automation of perforated mounting printed circuit boards, it is necessary to expand the area of the original printed circuit board by 40% so that the insertion head of the automatic plug-in can be inserted into the electronic components, otherwise, there will be insufficient clearance and the parts will be damaged. The automatic placement machine (SM421/SM411) uses vacuum nozzles to suck and place electronic components. The vacuum nozzles are smaller than the shape of the electronic components, which increases the relative density of installation. In fact, small electronic components and fine-pitch QFP devices are produced by automatic placement machines to achieve full-line automatic production.

5. Reduce costs and reduce expenses

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

(2) Reduce the number of holes for printed circuit boards and greatly save rework costs;

(3) Because of the improvement of frequency characteristics, the cost of circuit debugging is greatly reduced;

(4) Because the chip components are small in size and light in texture, the packaging, transportation, and storage costs are greatly reduced;

SMT patch processing technology can greatly save materials, energy, equipment, manpower, time, etc. Costs can be greatly reduced by 30% and 50%.

PCB circuit board substrate material classification

The substrate, in short, is the basic material for the production of PCB circuit boards. Generally speaking, the PCB substrate is composed of resin, reinforcing materials, and conductive materials, and there are many types. The most common resins are epoxy resin and phenolic resin. Reinforcing materials include paper base, glass cloth, etc. The most commonly used conductive material is copper foil. Copper foil is divided into electrolytic copper foil and rolled copper foil.

PCB substrate material classification:

1. According to different reinforcement materials:

1. Paper substrate (FR-1, FR-2, FR-3);

2. Epoxy glass fiber cloth substrate (FR-4, FR-5);

3. Composite substrate (CEM-1, CEM-3 (Composite Epoxy Material Grade-3);

4. HDI (High-Density Interconnect) PCB sheet (RCC);

Special substrates (metal substrates, ceramic substrates, thermoplastic substrates, etc.).

2. According to the flame retardant performance:

1. Flame-retardant type (UL94-V0, UL94V1);

2. Non-flame retardant type (UL94-HB grade).

3. According to different resins:

1. Phenolic resin PCB board;