The Method
In PCB assembly services, through-hole components are forwarded for soldering After inserting and fixing the details over the PCBs’ footprint position.
Workers participate in component placement or fixing for larger PCBs with more than 100 components.
Each worker places their designated details within the allocated time over the PCB and forwards them to the next worker.
For PCB movement motorized conveyer belt is installed.
Finally, after some inspection, the PCB with components is dipped into a hot molten solder reservoir for soldering.
This method, called wave soldering, is preferred for large-scale soldering of PCBs.
After soldering, the inspection is carried out for unsoldered components and wrong-placed pieces and proceeds for power-up.
At the last and final stage, a PCB becomes fault-free and qualifies for assembly in the mechanical jig. The PCB components fixing line is shown in Figure 1.
Figure 1: PCB components fixing and PCB assembly line
In Figure 2, the wave soldering method for through-hole parts is depicted.
Figure 2: Wave soldering method for through-hole components soldering
Steps of SMT PCB Assembly
A PCB is fitted aboard the SMT/ SMD Bill of Materials (BOM). At the first step of the PCB assembly, a small quantity of paste is applied using the stencil.
A stencil is a metallic/plastic sheet with holes in the components soldering.
The paste applied before the components’ placement holds them during PCB movement.
After placement, the PCB is soldered using the reflow method. PCBs with mixed components, such as DIP and SMD, are wave-soldered and reflow-soldered.
The hand soldering method is extensively applied in rework, troubleshooting, and small-scale productions, but that is unsuitable for large-scale PCB productions.
Figure 3 shows the SMT components pick-and-place machine.
Complex components, such as BGA and QFN packages, are soldered and inspected with specialized devices and are even more costly.
Figure 3: SMT/ SMD auto pick and place machine
