PCB Technical - The relationship between SMT and placement machine

As the main component and main technology of electrical interconnection technology, the surface assembly technology, namely SMT, is the mainstream of modern electrical interconnection technology. After more than 20 years of development, SMT has now become the main technical means for PCB circuit component-level interconnection of modern electronic products. According to relevant data, the penetration rate of SMT applications in developed countries has exceeded 75%, and it has further developed into the assembly technology field represented by high-density assembly and three-dimensional assembly.

What is SMT and placement machine?

Surface Mount Technology (SMT) can also be referred to as surface mount technology, surface mount technology and patch welding technology. It is a board-level electronic assembly technology that mounts surface mount components (SMD) on a printed circuit board (PCB). At present, advanced electronic products, especially in computer and communication electronic products, have generally adopted surface mount technology.

Mounting machine: also known as "mounting machine", "Surface Mount System" (Surface Mount System), in the production line, it is configured after the dispenser or screen printing machine, by moving the placement head to mount the surface A device where components are accurately placed on PCB pads. Divided into two kinds of manual and automatic.

1 What are the advantages of SMT?

SMT was born with the development of the electronics industry, and developed with the development of electronic technology, information technology, and computer application technology. The rapid popularity of SMT is due to its following advantages, let's take a look at it together.

1) It is easy to realize automation and improve production efficiency.

2) High assembly density of components, small size and light weight of electronic products.

3) High reliability. Automated production technology ensures the reliable connection of each solder joint. At the same time, because the surface mount components (SMD) are leadless or short leads, and are firmly mounted on the PCB surface, they have high reliability and shock resistance. powerful.

4) Good high frequency characteristics. Surface mount components (SMD) have no pins or segment pins, which not only reduces the influence caused by the distribution characteristics, but also firmly attaches and solders to the PCB surface, which greatly reduces the parasitic capacitance and parasitic inductance between leads, so to a large extent Reduce electromagnetic interference and radio frequency interference, and improve high-frequency characteristics.

5) Reduce costs. SMT increases the PCB wiring density, reduces the number of holes, reduces the area, and reduces the number of PCB layers with the same function, all of which reduce the manufacturing cost of the PCB. Leadless or short lead SMC/SMD saves lead material, omits trimming and bending processes, and reduces equipment and labor costs. The improvement of frequency characteristics reduces the cost of radio frequency debugging. The size and weight of electronic products are reduced, which reduces the cost of the whole machine. Good welding reliability will naturally reduce repair costs.

2 What is the basic process flow of SMT?

The basic process components of SMT include: printing (red glue/solder paste) --> inspection (optional AOI automatic or visual inspection) --> placement (first paste small components and then paste large components: high-speed placement and Integrated circuit mounting) --> Inspection (optional AOI optical/visual inspection) --> Soldering (using hot air reflow soldering for soldering) --> Inspection (Can be divided into AOI optical inspection appearance and functional test inspection) - > Maintenance (tools: soldering station and hot-air desoldering station, etc.) --> board splitting (manual or splitting machine to cut the board)

1) To form an SMT production line, there must be 3 kinds of important equipment: printing machine\dispensing machine, placement machine, reflow oven\wave soldering machine. Among them, the wave soldering process, with the development of surface mount technology, In particular, the large number of applications of bottom-lead integrated circuit packaging BGA\QFN has become more and more insufficient, so the current mainstream is still the reflow soldering process.

2) Whether it is for mainframe manufacturers or medium-sized machine manufacturers, Dipeng Classic recommends that the SMT production line generally consists of 2 placement machines, 1 high-speed placement machine (chip component placement machine) and 1 high-precision placement machine ( IC component placement machine), so that each perform its own duties, which is conducive to the highest production efficiency of the entire SMT production line. But now the situation is changing. Many placement machine manufacturers such as Dipeng have launched a multi-function placement machine, making it possible for the SMT production line to consist of only one placement machine. A multi-function placement machine can complete the placement of all components while maintaining a high placement speed, reducing investment. Such a production line program is favored by many small and medium-sized enterprises and academies of sciences.

The development of placement machines is always the most concerned area in the electronics manufacturing industry. The current development of electronic technology has continuously put forward new and higher requirements for placement equipment. In turn, the new development of electronic component placement equipment has been powerful Promote the development of electronic assembly industry, and then promote the development of electronic technology. So next, I will briefly introduce the composition of the placement machine.

The simplest mounter model

Automatic placement machine is used to realize high-speed, high-precision automatic placement of components. It is the most critical and complex equipment in the entire SMT production.

The most basic placement machine is composed of a frame, a circuit board clamping mechanism, a feeder, a placement head, a suction nozzle, and X, Y, and Z axes. The Z axis can move in the Z direction and can also rotate in the θ direction ( In order to adjust the rotation angle of the components from the pad).