The best soldering temperature must be considered

Another thing to consider is not just to consider the influence of temperature and time on the quality of welded joints. As the temperature of the welding alloy increases, the alloying and wettability of the filler will increase. Under normal circumstances, the welding temperature must be selected as a filler metal higher than the melting point. However, there are several factors that affect the temperature selection of the welding design. 

The best welding temperature must take into account: (1) the lowest possible welding temperature, (2) minimize the influence of thermal effects on the assembly, (3) keep the interaction of the filler/base metal to a minimum, and (4) ) Maximize the use of jigs or fixtures. In some cases, choose a higher welding temperature to accommodate other factors in the design (such as allowing the use of different filler metals, or controlled metallurgical effects, or adequate removal of surface contamination). Time is an important factor for welding joints, but most production processes generally choose to reduce welding time and costs. Although this is not always the case, because in some non-production factors, time and cost are limited by other attributes (such as strength, appearance).