The reason soldered links break is the joint is not getting hot enough, usually because it was assembled using a soldering iron. The solder melts around the opening of the clevis and then solidifies and looks like a strong joint, until..

The best way to solder a joint is with a torch. Dip the end of the rod in flux and locate the clevis onto it. Heat the clevis and wire until they are nice and hot, then touch the solder to the joint. The solder will melt instantly and be carried into the space between the wire and clevis through capillary action. Plumbers call it a "sweat joint". It is incredibly strong!