SMD or Surface Mount Device is the term to refer to the components that are attached to a printed circuit board through a soldering procedure. With the use of a soldering iron and solder, a component is securely attached to the PCB pad. Read this article on the exact procedure.
Apply the solder bead on the pad
Heat the soldering iron for about five minutes and apply a solder bead on the printed circuit board (PCB) pad where the SMD will be installed. Then, using a flux pen, apply some amount of liquid rosin based flux on the solder bead.
Position the SMD on the PCB pad
Pick up the SMD that you plan to install with a pair of tweezers and place this on the PCB pad. Then, with the heated soldering iron, apply heat to the solder bead, and at the same time pushing the SMD against the PCB pad. This is also the time that you need to position the SMD correctly on the PCB pad while the solder bead has not hardened yet. Then, take the soldering iron away and let the solder bead cool and harden.
Inspect the solder joint
After you have attached the SMD to the PCB pad, check the joint to make sure that the solder is there in between the SMD and the PCB pad. At this point, your main concern is not the quality of the solder, but the positioning of the SMD. The smd coils should create a flush against the printed circuit board and with both their ends attached to the pad. The SMD should be positioned straight and placed at the center of the two pads.
Attach the unsoldered end of the SMD to the PCB pad
With the flux pen, apply a good amount of liquid flux to both ends of the SMD. Then, heat the unsoldered end of the SMD and the adjacent PCB pad with the soldering iron, and apply solder bead to attach the SMD and the PCB pad together at this location. Make sure that the solder bead has flowed freely to the side of the SMD, as well as to the PCB pad.
Check the contact
After the solder bead has cooled down, check them to make sure that the SMD is securely attached to the PCB pad.
You may remove excess solder bead with a solder wick.
