The soldered joint is a fuse. If you use silver solder it will no longer be a fuse. Originally it was a crimped plug of very low temp solder which melted at about 120º. This is hard to find but is used by white metal modellers, for soldiers and the like. You can also use an actual thermal fuse in the 120-130 range, about $1, which is cheaper than the solder. There is often a blob of solder left on the join so if you can hold the two sides together with fine tweezers, a quick dab with a soldering iron will often rejoin them.
See http://www.pelicanparts.com/techarticles/mult_vdo_clock_repair/mult_vdo_clock_repair.htm

http://jlw97.fatcow.com/saabstories/pages/clockfix/