Hi Andrew,
That FAB note has a number of shortcomings.
"Construction to be SMOBD, using liquid photoimageable (LPI) solder mask
material, type XXXX. Apply to both external layers in accordance with IPC,
(Type B, Class 2). Use appropriate solder mask artworks for each side of
board."
I would thing SMOBD should be SMOBC.
I have never heard of a solder mask material Type "anything;" why put 
anything like this "down" if it does not have an accepted technical meaning?
"...in accordance with IPC" is meaningless without giving an IPC document 
number—IPC-D-325 is a 'documentation' document; for specification purposes you 
should be using IPC-SM-840.
(Type B, Class 2) also do not correspond to any accepted way of specifying 
solder mask.

I would recommend a FAB Note like this: 
"SOLDER MASK OVER BARE COPPER ACCORDING TO IPC-SM-840, CLASS H, TYPE LIQUID 
PHOTO IMAGEABLE (LPI), 0.0015 MAX THICKNESS, COLOR: GREEN, BOTH SIDES OF THE 
BOARD.   ALL FIDUCIALS, LANDS AND HOLES, EXCEPT VIAS, SHALL BE FREE OF SOLDER 
MASK MATERIAL."

If you are in the process of wring a specification document for your PCBs, my 
White Paper in the subject may be helpful—I am sending the details in a 
separate e-mail.



Werner

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