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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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