It has been claimed on another board that some SMT components cannot be used in an automated production line (i.e. reflow or wave soldering) because they cannot withstand the heat/temperature. Hand soldering is used to avoid these problems.
An example given where this was the case was film capacitors. Capacitors are often the component which limits the maximum temperature and time at high temperature, but I haven't seen any that preclude the use of reflow soldering.
I haven't encountered a single SMT component that cannot be used in an automated soldering process in the past. Some require care i.e. the temperature profile must be carefully chosen and times at high temperature limited. Some components do not support the use of lead free solder (in terms of maximum temperature), but these are becoming rare.
I suspect that requiring hand soldering is either due to:
- Limitations in the equipment i.e. the reflow oven cannot deliver heat quickly enough to meet the requirements.
- Poor design i.e. it hasn't been designed with reflow in mind and large and small components cannot be soldered at the same time.
- A few very special components require special treatment and it is easier to hand solder than change manufacturing processes.
- Small scale production where hand soldering doesn't cause costs to explode.
I also feel it might be incorrect to assume that hand soldering results in lower temperatures, but that is not the core question here.
I don't think it would ever be an inherent limit in an SMT component - they pretty much came about to support automated manufacture.