Common errors in pcb gerber design| pcb mgf fab design guidelines|Caring Circuit|China

Common Errors in PCB Gerber
and Solutions
PCB Prototyping and Medium volume specialist in
Shenzhen,China

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No matter how long you have been a PCB designer, creating Gerber files
that accurately reflect what you want manufactured is a challenge .
However, by learning from others and avoiding the most common errors
about PCB design, you can speed up the turnaround time, reduce the
chance of orders placed on hold, and complete your projects faster. The
following list reviews the most common mistakes made with Gerber files
and our suggestions.
Contact: Jing Song | T +86 755 8693 6426 | E jing@caringcircuit.com | Skype : caringcircuit | www.caringcircuit.com

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Missing layers of Gerber Files
Gerbers usually come in a .zip or .rar file,but we often find some layers are
missing in it.
Suggestion: Gerber 274X or 274D with all layers including copper layer,
solder mask layer,drilling layer, outline layer,silkscreen layer( not
necessary), metric units or English unit are both ok.

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Missing Aperture List
Your Gerber files specify what to do and where. Your aperture list
specifies what tool to use.
Suggestion: A single comprehensive aperture list for all layers should be
sent with your gerber files, rather than a separate aperture list for each
layer. Please do not modify the aperture list your software outputs. An
aperture list does not need to be sent with 274X format files, because if
274X gerber, it already shows the tool size. If you send 274D format, we
use your aperture list in combination with your gerber files to create your
artwork.All layout packages which output 274D also output an aperture
list. Common extensions include .rep, .apt, and .apr. If you have difficulty
outputting an aperture list, please send 274X format.

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Missing circuit board rout outline
A circuit board outline/rout path needs to be included with your files. Gerber
files are preferred, but a dimensioned drawing will work provided it is simple
to make an outline from, and we can determine how to align it correctly
relative to the circuitry. As long as we can identify a line that is the perimeter
of your circuit board and it matches your ordered dimensions, we will use it
for your board outline.The most common method that customers use for
communicating how to cut out their board is to place a 10 mil line on the top
copper layer around the perimeter of their circuit, centered on where they
want us to cut. We prefer a 10 mil wide line on the mask layer. The edge of
the router bit will cut to the center of the given line unless we are told
otherwise in the notes. Some customers put the board outline on all layers.

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Suggestion:We can make an outline for you, but we will need your
confirmation to do so. If your board is a perfect square or rectangle, we can
make the outline if we know the exact dimensions and any corner relative to
a feature such as the center of a tooling hole. Alternatively, if we know you
board is a perfect rectangle and we know the x and y dimensions, we can
center this rectangle around you design.
Note: 1. GKO layers will NOT be used as an outline to cut out your board.
The GKO layer is meant to be the keep out layer. If no outline, we will ask if
you do want us to use the GKO outline as your board outline. 2. With many
software packages, the "outline" is seen on all layers (as a global layer), but
will commonly not appear in the outputted Gerber files. Gerber file viewers
can be used to check if your software is placing the board outline in your
files.

LOGOMissing excellon drill file or
tool list especially no mention
PTH or NPTH, or no mention
tool size
Suggestion: Excellon drill files are used to determine what size holes to drill
and where. Plated and non-plated holes need to be included in one drill file,
with plated and non-plated holes having different tool numbers.A tool list is
used in combination with your Excellon drill file to create your drill. Your drill
file specifies where to place the holes. Your tool list specifies what tool to
use. A tool list should be embedded in your Excellon drill file or sent as a
separate text file. Using a tool list provided on a fabrication drawing is also
ok.

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Insufficient annular ring
An annular ring is needed for some Plated through holes especially when this
hole connect to surface copper. The annular ring diameter should be enough
bigger than holes. For example, a .030" pad with an .020" hole would have
a .005" annular ring. This is required to allow for complete plating on vias, as
well as solderability on component holes.
Suggestion: A minimum of .003" annular ring for vias or a minimum of .007"
for component holes is required for manufacturing.We All layout packages
we will provide as a DFM check. Setting sufficient annular ring in your layout
software is the preferred method in order to maintain proper copper spacing.
If not, we will set that for you when we make working gerbers.

LOGOInsufficient copper trace
Width/Spacing
Copper spacing is the minimum air gap between any two adjacent copper
features. Trace width is the minimum width of a copper feature, usually
traces. For 1OZ copper weight, a minimum of .004" trace width/spacing is
necessary. A premium is charged for trace width/spacing less than .007".
Suggestion : Setting sufficient trace width/ spacing in your layout software is
the preferred method. Trace width and spacing push and pull against one
another, so changing a problem area may require rerouting traces, adding
vias, or moving components.

LOGOInsufficient inner clearances
Inner clearance is the minimum distance from the edge of a hole to any
adjacent, unconnected, inner layer copper. Sufficient inner clearances help
ensure that your drill does not cause shorts to your inner copper layers. This
is important for both plated and non-plated holes, as non-plated holes may
either cut into an adjacent trace or cause shorts during assembly. A minimum
of .006" inner clearance is required and .008" is preferred for 1oz copper
weight.
Suggestion: Most inner clearance issues can be resolved if negative image
inners are provided, but it is preferred to not modify these. Setting these
clearances in your layout software is the preferred method, as this will
maintain intended connectivity.
Spacing + Annular ring = Inner clearance. Another trick that can help resolve
problem areas is to move the affected traces to outer copper layers, where
this is not an issue.

LOGOInsufficient solder mask open or
covered
Suggestion: we will check all these kinds of errors when we make working
gerbers and come back to you with our suggestion for your confirmation.

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Wrong place of pads, solder mask
opening, holes,silkscreen
Place of pads, holes,silkscreen are at wrong places, solder mask opening or
covering are wrong.
Suggestion: we will check all these kindsof errors when we make working
gerbers and tell you.

LOGOCopper exposed may be viewable
on circuit board edge or
inside cutouts or Non-Plated
Holes
Exposed copper may be viewable on the board edge due to copper
being to close to the board outline that we will use to cut out the
circuit board(s).
Suggestion:
Single layer pcb(s), Tab-routed arrayed boards and boards with
cutouts:
Outer layer copper should be 0.01" away from the center of the
board edge to prevent exposed copper. Copper within 0.01" of the
center of the rout line may be exposed and viewable from the board
edge.
Inner layer copper should be 0.015" mils away from the center of
the board edge to prevent exposed copper.

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Scored circuit board(s):
For 0.062" thick boards:
Outer layer copper should be 0.015" away from the center of the
score line to prevent exposed copper. Copper within 0.015" of the
center of the scoring line may be exposed and viewable from the
board edge.
Inner layer copper should be 0.02" away from the center of the score
line to prevent exposed copper.
For 0.093" thick boards, add 0.005" more of space than described
above.
For 0.125" thick boards, add 0.01" more of space than described
above.

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Non-plated Drills/holes: Non-plated holes can have 0.005"
spacing from the edge of the drill to the nearest copper.
1) Pull back your copper from the danger zones (as mentioned
above) to assure that there will be no exposed copper,
Or 2) Put a note in your order (or write it in an readme.txt file
with the gerber .zip) that tells us that exposed copper is
intended and/or expected.
Or 3) Put a note in your order telling us that you would like us
to pull back any copper that might be in these danger zones
so that there will not be any exposed copper viewable when
the boards are completed.
Note: If there is copper trace that will be clipped due to being
too close to the board edge, Caring Circuits will come back to
you with suggestions for your confirmation because of the
possibility of severing/lifting the trace.

LOGODiscrepancies of unit board or a
panel dimension
:
If the ordered board dimensions do not match the size of the
board seen in the Gerber files or other documentation or emails,
the job may go on hold until these mismatches are resolved. If
the values are close. PCB orders will be run with the dimensions
found in the Gerber files.
Suggestion: Accurately measure the greatest X dimension and
Y dimension (extends) of circuit board, or add a note in the
readme.txt file that we should run with dimensions found in the
Gerber files.

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We remind you more
To make panel drawing economical. Border at two sides 5mm each
is enough for manufacturability.
If you need V-score (V-cut) the panels between small pieces, no
need distance between units, otherwise the out size will be bigger.
Pls mention your specifications, cooper weight, surface treatment,
material,solder mask color, silkscreen color, need panel or not.etc.
You could write it in .txt ,word,excel or write it in gerber directly.
If there is mismatches between your purchase order, your email
writing and what is found by the CAM Engineer in the Fabrication
Drawing, Gerber files, or Readme.txt files , the job may go on hold
until these discrepancies are resolved.

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Thanks for your time!
Jing Song
Tel: +86 755 8693 6426
E-mail: jing@caringcircuit.com
Skype: caringcircuit
www.caringcircuit.com
No.12 Building Zhongxing City,Chuangye
Road,Nanshan,Shenzhen,China

Common errors in pcb gerber design| pcb mgf fab design guidelines|Caring Circuit|China

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Common errors in pcb gerber design| pcb mgf fab design guidelines|Caring Circuit|China