The "B" Stage always contains moisture and solvents and may be necesssary to
achieve flow of the epoxy resin in the prepreg.  Evacuating the prepreg often
times produces thick dry laminations.  The main thing that should be done is
to keep the solvents and moisture dissolved and finely dispersed in the resin
in the prepreg during lamination and prevent these from forming little
bubbles that coalesce to form laminate voids.  

Suggest that you do a few lamination tests to try to eliminate the laminate
voids.
   I assume you are not using a vacuum assist press and that you are using a
kiss cycle before applyiing full pressure.

    (1) Use a 25 psi kiss pressure before going to full pressure instead of
the 15 psi

    (2) If you are usng the kiss pressure and going to full pressure
         at somewhere around 110oC internal package temperature, try
    backing off and go use the temperature to apply full pressure at      the
tempetatures of  80, 90 and 100oC.  Also try a one-step     laminating
process which is to apply full pressure immediately      after placing the
package onto the hot platen.

    (3) If you are using a vacuum assist press, I would also suggest
     that you do (2) above.

Of course, look for voids after the tests above 

Several things that are missing from you failure report are:
    Type of press
    Heat rise rate 
    Kiss or no kiss 
    Type of prepreg, glass style, gel time, scale flow   
    Kiss pressure 
    Laminating pressure 
    Area of panel where greatest laminate void density appears. 
     
All of these affect the prossibility of the formation of laminate voids.
and would give the failure analyst a better chance.  If you want give me a
call at the number below.

Phil Hinton 
[log in to unmask]    
520-745-1013