To solder the wires to the relay, tin the end of the required wire, and bend the tinned end of wire in the middle with needle nose pliers to form a "U" shape. Please refer to them during installation in order to avoid problems. The protective measures used will determine suitability for automatic soldering or automatic cleaning. Please follow the recommendations. As electronic devices become more compact, it is becoming a common practice to weld the relay to a PC board (along with the semiconductors) rather than using plug-in relays with sockets. When relays are welded, their functionality may be affected due to seepage of flux into the relay. Where to find. In this guide, I'll walk you through pro-level soldering techniques, safety tips, and insights from real PCB assembly challenges.