Thermal shock refers to shock at high temperature, usually molten
     solder at 550F for duration of 10 secs, the IPC-TM-650 has the
     procedure.

     Temp cycling subjects the test specimen to hot and cold environment
     with a specific transition time. Cold temp could be -40C or -65C
     depending on customer requirement, hot temp could be 85C or 125C.
     Again, IPC-TM-650 has a standard procedure.

     Thermal shock looks at board reliability when it is subjected to short
     duration of high temperature, such as assembly wave soldering. Temp
     cycling looks at reliability of board when used in environment that
     has quick temperature change, such as aircraft, from ground temp to
     severe cold up in the air. Thermal shock is not necessarily more
     severe than temp cycling.


     Teik M. Ng
     Corporate Quality Manager
     Kalex Circuit Board Ltd.



______________________________ Reply Separator _________________________________
Subject: [TN] Reliability test
Author:  <[log in to unmask]> at INTERNET
Date:    99-8-2 22:25


Could anyone enlighten me on the difference between Thermal shock and
Temperature cycling test. I know the former is more severe but what is each
test looking at?

Thanks.

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