From: henry@spsystems.net   
      
   In article <4015df55.108433806@news.eircom.net>,   
   Russell Wallace  wrote:   
   >>...And so the electronics will see increasing   
   >>temperature swings, and increasing thermal-contraction stresses between   
   >>different materials.  Fairly soon, things will start to crack.   
   >   
   >That makes sense, though I'm surprised it isn't possible to find   
   >materials that don't crack when put through heating/cooling cycles. Or   
   >is it the case that it could be done, but would cost more than it'd be   
   >worth?   
      
   There is very limited room to maneuver on this, because you need materials   
   that can do their jobs in other respects.  In practice, one tries to avoid   
   gross mismatches of thermal expansion anyway, because there is some   
   exposure to heat in soldering etc., but often there is little or no choice.   
      
   And yes, economics do enter the picture as well.  The MER project couldn't   
   possibly have afforded to custom-make all its ICs, for example.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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