PCBA Tech - Mounting method in SMT patch processing

1. SMT single-sided hybrid mounting method

The first type is single-sided hybrid mounting, that is, SMC/SMD and through-hole plug-in components (17HC) are distributed on different sides of the PCB, but the soldering surface is only single-sided. This type of mounting method uses single-sided PCB and wave soldering (currently double wave soldering is generally used). There are two specific mounting methods.

(1) Paste first. The first mounting method is called the first mounting method, that is, the SMC/SMD is mounted on the B side (welding side) of the PCB first, and then the THC is inserted on the A side.

(2) Post-sticking method. The second mounting method is called post-attachment method, which is to first insert THC on the A side of the PCB, and then mount the SMD on the B side.

2. SMT double-sided hybrid mounting method

The second type is double-sided hybrid mounting. SMC/SMD and T.HC can be mixed and distributed on the same side of the PCB. At the same time, SMC/SMD can also be distributed on both sides of the PCB. Double-sided hybrid mounting adopts double-sided PCB, double wave soldering or reflow soldering. In this type of mounting method, there is also a difference between first and second SMC/SMD. Generally, it is reasonable to choose according to the type of SMC/SMD and the size of the PCB. Usually, the first method is more. Two types of mounting methods are commonly used in this type of mounting.

SMC/SMD and ‘FHC are on the same side, SMC/SMD and THC are on the same side of the PCB.

SMC/SMD and iFHC have different side methods. The surface mount integrated chip (SMIC) and THC are placed on the A side of the PCB, while the SMC and small outline transistor (SOT) are placed on the B side.

In this type of mounting method, SMC/SMD is mounted on one or both sides of the PCB, and leaded components that are difficult to be surface mounted are inserted into the mounting, so the mounting density is quite high.

Third, the whole surface mount method

Full surface mounting means that there is only SMC/SMD and no THC on the PCB. As the current components have not yet fully realized SMT, there are not many such mounting forms in practical applications. This type of mounting method is generally on a PCB or ceramic substrate with a fine line pattern, using fine-pitch devices and a reflow soldering process for mounting. It also has two mounting methods:

Single-sided surface mount method: Single-sided PCB is used to mount SMC/SMD on one side.

Double-sided surface mounting method: double-sided PCB is used for mounting on both sides, SMC/SMD, and the mounting density is higher.

The mounting 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 conditions of the mounting equipment.

In general, SMA can be divided into three types of single-sided mixed packaging, double-sided mixed packaging and full-surface mounting, totaling 6 types of mounting methods. Different types of SMA have different mounting methods, and the same type of SMA can also have different mounting methods.