Hi, Eddie,

Polyimide boards always seemed pretty good at higher temps, and you'll need
a very high melting point solder as well - normal 63/37 eutectic solder
will be well reflowed at 205 deg C.

My immediate concern would be component survival at 205 Deg C, especially
for 4 hours! Most chip dies won't survive prolonged exposure like that at
temperatures over 125-150 deg C without the internal wire bonding coming
apart and other forms of terminal death. You will have to design in some
internal cooling for your equipment to keep your chips within their normal
operating temperature range.

FYI, Commercial grade chips will operate reliably in a maximum ambient
(still air) temperature (Ta) of 70 deg C, Industrial grades operate at Ta
max of 85 deg C and Military grades operate at a Ta max of 125 deg C. So
you see, you'll have trouble at 205 deg C without cooling the chips. Heat
pipe technology is worth looking at for a solution, or put the boards on a
cold wall and pump refridgerated air through it when required.

You have a "harsh operating condition" here, my friend. Good luck!

Peter



Eddie Rocha <[log in to unmask]>     27/06/2002 12:37 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Eddie Rocha

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: [TN] High operating temperature








Can someone recommend a laminate for product that will, at
times see operating temperatures of 205C for 4 hours. Also
would this require a different solder? Will solder reflow?
Any comments?
thanks,

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