Do not overheat when soldered. This may greatly shorten the product life or cause liquid leakage. ln case
of a 1.6mm-thick and single side printed board. for example, keep
the following soldering conditions: temperature lower then 260℃,
time within 6.5 to 10 seconds. When a board thinner than 1.6 mm or
multi-layer printed board is used, contact us. ln
the case of hand soldering, the iron tip temperature is lower than 400℃, time is shorter than 4 seconds. The coin types and multilayer coin types excluding the DZ and reflow-compatible coin types use polypropylene as the packing material for sealing and therefore susceptible to excessive heat. Note that the component body temperature shall be controlled so as not to exceed 90℃ including preheating.
http://www.elna.co.jp/en/capacitor/double_layer/catalog/pdf/d_caution_e_p211-212.pdf