Do you know how to solder? Have you ever soldered surface mount devices?

Soldering joins component leads to PCB pads by melting solder (a fusible metal alloy) to form an electrical and mechanical bond. Good practice: heat the joint (pad and lead) with the iron, apply solder to the heated joint (not the iron tip), use flux to clean the metal and help wetting, and aim for a shiny, concave fillet. Use appropriate iron temperature and tip size, and avoid cold joints (dull/grainy) and bridges.

• Through-hole: leads pass through plated holes and are soldered on the far side—forgiving and easy by hand.
• Surface-mount (SMT/SMD): components sit on pads on the board surface. Hand-soldering small SMT parts uses a fine tip, flux, and often tweezers; fine-pitch parts use techniques like drag-soldering and solder wick to clear bridges. Hot-air rework stations and reflow (solder paste plus controlled heating, e.g., a reflow oven or hot plate) are used for placing and reworking SMT parts, including leadless packages (QFN/BGA) that can't be reached with an iron. Volume production uses stencil-applied paste and reflow ovens.