June,

Two comments:

> B) MINOR REMOVAL OF SILKSCREEN DATA IS PERMISSIBLE TO ELIMINATE INK FROM
> ON
> PADS OR IN HOLES.  RELOCATION OF SILKSCREEN DATA IS NOT
> PERMISSIBLE.
Be careful on this.  We recently had a board where our CAD system was set to
a certain backoff from holes/pads and the board fabricator's system was set
to a larger number to match their tolerances (.009" back off, I believe).
While the reference designators mostly looked clear and legible on our
drawing, on the board there were a lot of partial letters and numbers

> D) WARP AND TWIST OF PWB SHALL NOT EXCEED .010 INCH PER LINEAR INCH.
>
This is 1% bow and twist.  0.7% bow and twist is commonly called out for SMT
in order to accommodate processing.

Hope this helps.

-Steve



Steven K. Lustig
Process Engineer
EMS Technologies, Inc.
Norcross, GA
(770) 263-9200 x4714
[log in to unmask]

> ----------
> From:         [log in to unmask][SMTP:[log in to unmask]]
> Sent:         Monday, July 12, 1999 11:28 PM
> To:   [log in to unmask]
> Subject:      [TN] fab dwg notes...critique
>
> 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
>
>
> 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.
>
> 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.
>
> IMPEDANCE:  SEE NOTES ON SHEET 2 FOR SPECIFIC CRITERIA. TDR TEST
> CERTIFICATIONS OF EACH BOARD ARE REQUIRED.
>
> SOLDER MASK, BOTH SIDES:
> A) SOLDER MASK MATERIAL SHALL BE GREEN IN COLOR, GLOSS FINISH .001 MIN
> THICK,
> TYPE A OR B PER IPC-SM-840, CLASS 3.
> B) SOLDER MASK SHALL BE APPLIED OVER BARE COPPER ON BOTH SIDES OF  BOARD
> WITH
> THE EXCEPTION OF PADS AND PLATED THROUGH HOLES (VIAS MAY BE COVERED).
> C) SOLDER MASK SHALL BE IN ACCORDANCE WITH THE SOLDER MASK MASTER AND
> REGISTRATION SHALL BE SUCH THAT 360 DEGREES OF ALL    TERMINAL LAND AREAS
> (PADS) ARE EXPOSED (.000 TO .010 LARGER THAN PADS).
> D) SOLDER MASK SHALL BE SMOOTH AND FREE OF LUMPS AND BUBBLES.  MASKED AREA
> SHALL EXHIBIT STRAIGH, SHARPLY DEFINED EDGES.
> E) SOLDER MASK MATERIAL SHALL NOT LIFT FROM PRINTED WIRING OR BASE
> LAMINATE
> WHEN EXPOSED TO 500 DEGREE SOLDER FOR 30 SECONDS.
>
> SILKSCREEN, BOTH SIDES:
> A) SILKSCREEN SHALL BE IN ACCORDANCE WITH THE SILKSCREEN MASTER USING
> PERMANENT SOLVENT-RESISTANT WHITE INK.
> B) MINOR REMOVAL OF SILKSCREEN DATA IS PERMISSIBLE TO ELIMINATE INK FROM
> ON
> PADS OR IN HOLES.  RELOCATION OF SILKSCREEN DATA IS NOT
> PERMISSIBLE.
> C) SILKSCREEN SHALL BE SHARPLY DEFINED AND FULLY LEGIBLE.
>
> REGISTRATION, UNLESS OTHERWISE SPECIFIED:
> A) PADS MUST BE ALIGNED WITHIN .003 FROM FRONT TO REAR.
> B) LAYER TO LAYER REGISTRATION MUST BE WITHIN +/- .003.
> C) HOLE TO PAD REGISTRATION SHALL BE .005 TRUE POSITION DIAMETER OF CENTER
> INDICATED ON THE MASTER ARTWORK.
>
> DRILLING:
> A) SEE HOLE CHART ON SHEETS 3-6 FOR FINISHED HOLE SIZES AND TOLERANCES.
> B) DRILLED HOLE SIZE OVER FINISHED HOLE SIZE MUST BE NO LARGER THAN .003
> FOR
> HOLES WITH LESS THAN .062 INDICATED FINISHED SIZE PER THE CHART.
>
> GENERAL:
> A) FABRICATION PROCESS SHALL BE UL APPROVED AND PCB SHALL BE IDENTIFIED
> WITH
> MANUFACTURER'S APPROVED LOGO AND TYPE    DESIGNATION PER MANUFACTURER'S
> SPECIFICATION.
> B) WITH THE EXCEPTION OF TOOLING FILM ADJUSTMENT TO COMPENSATE FOR ETCH
> FACTORS, NO CHANGES ARE ALLOWED TO ANY MASTER PATERN OR MEDIA WITHOUT
> PRIOR
> WRITTEN APPROVAL OF DESIGN ORIGINATOR.
> C) ACCEPTABILITY OF MEASLING AND CRAZING SHALL MEET OR EXCEED REQUIREMENTS
> OF
> IPC-A-600, CLASS 2.
> D) WARP AND TWIST OF PWB SHALL NOT EXCEED .010 INCH PER LINEAR INCH.
> E) FINISHED PRINTED WIRING BOARD SHALL AGREE WITH THE MASTER PATTERN
> SUPPLIED
> WITH RESPECT TO PAD SIZE AND SHAPE, AND LINE WIDTH AND ROUTING.
>