We conducted two lenghly tests, temperature cycling and thermal shock, 
     where we encountered problems with unfilled via holes on 6-layer MLBs, 
     approximately .062 thickness. First our via holes were approximately 
     .035". The temperature range was -65C to 125C.  Test time per cycle 
     was 3-hrs. for temperature cycling and 42-min. for thermal shock.
     Results:  failures started occurring on the thermal shock boards at 
     440 cycles and 373 cycles on temperature cycled MLBs. Once the via 
     holes were filled with solder no more via hole failures were 
     experienced through 7650 shock cycles and 4910 temperature cycles, end 
     of test sequence.
     The above data was for bare MLBs.  We also had two different conformal 
     coatings in our tests. One an epoxide type coating which performed the 
     same as the bare MLBs for via holes however we were surprised with the 
     performance of Parylene-c coated MLBs. We never experienced any via 
     hole failures with these boards in the unfilled state through 7650 
     shock and 4910 temperature cycles.
     
     Regards,
     Arny Andrade
     Sandia National Laboiratories/California
     [log in to unmask] at CASMTP
     
     
     
     


______________________________ Reply Separator _________________________________
Subject: via data
Author:  [log in to unmask] at casmtp
Date:    10/9/96 12:02 PM


     Is there any research on finished via structure and the integrety of 
     the connection; specifically tented or plugged vias vs. non-tented 
     vias (lpi solder mask) filled with solder.
     
*************************************************************************** 
* TechNet mail list is provided as a service by IPC using SmartList v3.05 * 
*************************************************************************** 
* To unsubscribe from this list at any time, send a message to:           * 
* [log in to unmask] with <subject: unsubscribe> and no text.        * 
***************************************************************************
     

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************