Definition

Through-hole technology uses component leads inserted through plated holes and soldered on the opposite side. Choose through-hole over SMD when: mechanical strength matters (connectors see repeated mating cycles, components under mechanical stress), current exceeds SMD package ratings (through-hole handles 3-5A per pin easily), or hand soldering and field repair are expected. Through-hole pads must include thermal relief when connected to planes, otherwise wave soldering will not wet properly. Mixed-technology boards assemble SMT first (reflow), then through-hole (wave or selective soldering).