1: SMT overview SMT is the abbreviation of surface mount technology, which is translated into surface mount technology. The United States is the birthplace of SMT. Since the emergence of the first surface mount component in the world and the launch of the first surface mount integrated circuit by Philips in 1963, SMT has been mainly used in military, aviation, aerospace and other cutting-edge products and investment products from the initial stage, and has gradually been widely used in computer, communication, military, industrial automation, consumer electronics and other industries. SMT is developing very rapidly. In the 1980s, SMT technology has become the most popular new generation of electronic assembly technology in the world, known as a revolution in electronic assembly technology.
2: SMT composition: it mainly consists of surface mount components (SMC / SMD), mount technology and mount equipment.
2.1: surface mount components (SMC / SMD)
2.1.1: surface mount components (SMC / SMD) Description: SMC: mainly refers to some active surface mount components; SMD: mainly refers to some passive surface mount components;
2.1.2: development trend of SMC / SMD (1) SMC – chip components are developing to small and thin. Its size develops from 1206 (3.2mm * 1.6mm) to 0805 (2.0mm * 1.25mm) – 0603 (1.6mm * 0.8mm) – 0402 (1.0mm * 0.5mm) – 0201 (0.6mm * 0.3mm).
(2) SMD – surface mount devices are developing towards small, thin and narrow pin spacing. The center distance of pins develops from 1.27 to 0.635mm-0.5mm-0.4mm and 0.3mm.
(3) new packaging forms BGA (ball grid array), CSP (ubga) and FILP chip (flip chip) have emerged. Due to QFP (four sided flatpack devices are limited by SMT process, and the pin spacing of 0.3mm is already the limit value. The pins of BGA are spherical and evenly distributed at the bottom of the chip. Compared with QFP, BGA has the most prominent advantages: firstly, the packaging area ratio of I / O number is high, which saves PCB area and improves assembly density. Secondly, the pin spacing is large, with 1.5mm, 1.27mm and 1.00mm, which is less difficult to assemble Lower, larger processing window. Example: when the pin spacing of 31mm * 31mmr ＾ BGA ＾ is 1.5mm, there are 400 solder balls (I / O); When the pin spacing is 1.0mm, there are 900 solder balls (I / O). Qfp-208 is also 31mm * 31mm. When the pin spacing is 0.5mm, there are only 208 pins. BGA is competitive in both performance and price, and has played a leading role in high (I / O) device packaging.
(4) narrow spacing Technology (FPT) is the inevitable trend of SMT development. FPT refers to the technology of assembling SMD with pin spacing between 0.635-0.3mm and SMC with length * width less than or equal to 1.6mm * 0.8mm on PCB. Due to the rapid development of computer, communication, aerospace and other electronic technologies, the integration of semiconductor integrated circuits is higher and higher, the SMC is smaller and smaller, and the pin spacing of SMD is narrower and narrower. At present, QFP with 0.635mm and 0.5mm pin spacing has become a communication device in industrial and military electronic equipment.