normally is -55 to 125 C, depend upon if you are facing the sun or  
not... (even in the desert you are easily goes to 85 C...if your  
intended higher than that, you need active or passive cooling in your  
design).  you need to go back to MIL-STD establish date to find  
out... Your design limit usually is upper test limit plus 20 to 25 C  
for short duration... if you really need to operating at high temp,  
you need to prevent creep - that is not standard eutectic Sn/Pb...  
you should go back to ESA to find out design detail requirement and  
design criteria.  best of luck.
my 1.5 cents. IMHO.
jk
On Mar 1, 2018, at 2:13 AM, CANTAGALLO Luigi wrote:

> Hello Technetters.
>
> I have a question on a limitation of operating temperature of SnPb  
> solder joints in aerospace equipment's.
> The ESA (European Space Agency) specifications, concerning  
> soldering of components SMT or THT, tell " The mounting and  
> supporting of components, terminals and conductors applies to  
> assemblies designed to operate within the temperature limits of -55° 
> C to +85°C".
> The issue is the +85°C.
> We suspect that it is due to aging of solder joints (Law of  
> Arrhenius?) but, today, nobody manages to give an explanation to  
> this limit which seems historic. Somebody has an idea about this  
> topic ? Why +85°C and not +90°C or +100°C?
> Thanks for your advices.
>
> Best regards,
>
> CANTAGALLO Luigi
> Technology Engineer
> Thales Alenia Space Belgium
> [log in to unmask]
>
> [@@ OPEN @@]