Hi Patty,
     
     I do not have a solution for your problem, but here are some questions 
     that may help lead you to a solution.
     
     From your description, you have core materials on the outer layers?  
     Are the 2 / 9 cores of the same core thickness and manufacturing lot?
     Were the 2 / 9 cores imaged and etched at the same time as the 
     remaining cores?
     
     You may have a problem with your tooling system in the inner layer 
     imaging operation.  (a brief description of your system may help)
     
     Are you sure that this is a "shift" and not a "shrinkage" of the 2 / 9 
     images?  If there is a shrinkage, you will need to compensate the 2 / 
     9 CAD data.  If there is an image shrinkage of the 2 / 9 layers, the 
     "shift" should be symmetrical around the center of the panel.  
     
     Good Luck,
     Joe Brunetto
     Process Engineer
     Zycon Corporation


______________________________ Reply Separator _________________________________
Subject: FAB(Shifting Layers)
Author:  [log in to unmask] at corp
Date:    3/20/97 12:47 PM


We are experincing a reaccuring problem with our lamination process on 10 
layer projects with the following stackup: 
     
1.  1 oz copper on all 5 FR4 5 mil sheets;
2.  3 sheets of PGFK1080 2.5mil prepreg in each gap (total of 7.5mils each 
gap); 
3.  Grain of prepreg is in the same direction; 
4.  finished thickness 69 mils;
5.  layers 2-4 & 7-9 are signal layers; 
6.  layers 5&6 are ground/VCC planes.
     
Problem:  We are consistently seeing layers 2 and 9 shift 3-4 mils more than 
the other layers (3:4, 5:6, & 7:8).  Layers 3:4, 5:6, & 7:8 all align well 
with each other and the outermost sheets are shifted to the right by this 3-4 
mils.  Once layers 1 and 10 are imaged onto the drilled panel, they also line 
up well with the innermost layers (3:4, 5:6, & 7:8).  We are losing panels due 
to annualar rings less than 2 mils on layers 2 & 9 (Mil-P-55110).
     
We would appreciate any suggestions from those who have seen similar 
occurances.
     
Patty Causey / Marty W. Sheppard
Process Engineering Section
email address:  [log in to unmask] / 
[log in to unmask]
Phone: (912) 926-9473(9632)
     
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