June in the Drafting asked:

>The following fabrication drawing notes have been suggested by a group of
>individuals (engineer, technician and designer) for a complicated RF board
>with tight tolerances (relatively speaking).  The smallest finished hole size
>is .008 in. (vias, semi-blind), the smallest thru-hole via is .013.  The
>board is .093 thick, 8 layers, SMT both sides.  Controlled impedance circuits
>in the form of microstrip and stripline on outer layers and an inner layer
>(respectively), the thinnest line width being .007 and the smallest spacing
>.005.
>Since you are all involved in the fabrication process in some way, your
>(collective) feedback is desired......have a ball!  Please know that your
>input will be appreciated.  Thanks, June in the Drafting

Why not specify IPC-6012 type 4 as your performance specification?
>
>NOTES:  UNLESS OTHERWISE SPECIFIED
>MATERIAL:
>EPOXY GLASS, NEMA GRADE FR-4, (SHALL MEET UL 94V-0), Dk = 4.3 NOMINAL, COPPER
>CLAD 1 OZ AND 2 OZ FINISHED COPPER AS SPECIFIED ON SHEET 2.  TOTAL THICKNESS
>.088/.098.

You should also specify min Tg 170 degrees C for an 0.093" thickness 8
layer, in order to gain better dimensional stability and freedom from
warpage.

>PLATING/FINISH:
>A) CIRCUITRY AND PLATED THROUGH HOLES SHALL BE ELECTROPLATED COPPER .001 TO
>.002 THICK AND SHALL MEET OR EXCEED THE ACCEPTABILITY REQUIREMENTS OF
>IPC-A-600, CLASS 2.
>
>B) VIAS MAY BE PLUGGED.
>
>C) CIRCUITRY AND PLATED THROUGH HOLES TO BE PLATED GOLD   (IMMERSION METHOD
>ACCEPTABLE) .00003 TO .00005 THICK OVER NICKEL .00015 MIN THICKNESS.

Why so thick on the Ni? Most specs are at 0.000050" or 0.000100"


regards,



Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com