According to the specific requirements of assembly products and assembly equipment conditions to select the appropriate assembly method, is the basis of efficient, low-cost assembly production, but also the main content of SMT patch processing technology design. The surface mount technology, refers to the miniaturization of components sheet structure components or suitable for surface mounting, in accordance with the requirements placed on the surface of printed circuit board, with reflow soldering or welding assembly, composed of electronic components assembly technology has certain function.
In the traditional THT printed circuit boards, components and solder joints are located on both sides of the board, and in the SMT patch printed circuit board, the solder joints and components are on the same side of the board. Therefore, in the SMT patch printed circuit board, the through-hole is used to connect the two sides of the circuit board, the number of holes is much less, the diameter of the hole is much smaller, so that the assembly density of the circuit board can be greatly improved. The following small series to introduce the processing technology of SMT patch assembly.
One, SMT single side mixed assembly mode
The first is the single mixed assembly, namely SMC/SMD and tht element (17HC) distribution mixed in different side of PCB, but it is only one side welding surface. This kind of assembly methods are single side PCB and wave soldering (now generally use double wave soldering) process, there are two kinds of assembly.
(1) first paste. The first assembly method called the first paste method, that is, in the PCB B surface (welding surface) first mount SMC/SMD, and then insert the A surface THC.
(2) post sticking method. The second method of Assembly called post paste, is the first in the PCB A surface mount THC, after the B surface mount SMD.
Two, SMT double-sided mixed assembly mode
The second type is duplex hybrid assembly, SMC/SMD and T.HC can be mixed in the same side of the PCB distribution, while SMC/SMD can also be distributed on the.PCB side. Double side hybrid assembly using double-sided PCB, double wave soldering or reflow soldering. In this type of assembly method is also the first paste or paste the difference between the SMC/SMD, generally based on the type of SMC/SMD and the size of the PCB reasonable choice, usually the first paste more. The assembly of the two commonly used assembly methods.
(1) SMC/SMD and 'FHC in the same way, SMC/SMD and THC on the side of.PCB.
(2) SMC/SMD and iFHC in different ways, the surface mount integrated chip (SMIC) and THC on the PCB side of the A, while the SMC and small outline transistor (SOT) on the B surface.
This type of assembly is due to a single or double sided SMC/SMD in the PCB, and the difficult to assemble the surface of the lead into the assembly of components, so the assembly density is quite high.
The assembly method and process flow of SMT chip processing mainly depend on the type of surface mount component (SMA), the type of components used and the condition of assembly equipment. In general SMA can be divided into single and double mixed and mixed 3 types of surface mount 6 assembly. Different types of SMA assembly methods are different, the same type of SMA assembly can also be different.