gerber errors & solution about pcb design

7/29/2019 Gerber Errors & Solution about pcb design

1/19

Common Errors in PCB Gerber andSolutionsPCB Prototyping and Medium volume specialist in

Shenzhen,China


2/19

LOGO

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. Thefollowing list reviews the most common mistakes made with Gerber files

and our suggestions.

Contact: Jing Song | T +86 755 8693 6426 | E [email protected] | Skype : caringcircuit | www.caringcircuit.com


3/19

LOGOMissing 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.



4/19

LOGOMissing 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 if274X 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.



5/19

LOGOMissing 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 itfor 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 cancenter 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 viewerscan be used to check if your software is placing the board outline in your files.



7/19

LOGOMissing excellon drill file or tool listespecially no mention PTH orNPTH, 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 isused 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.



8/19

LOGOInsufficient 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.



9/19

LOGOInsufficient copper traceWidth/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.



10/19

LOGOnsufficient 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.



11/19

LOGOnsufficient solder mask open orcovered

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.



12/19

LOGOWrong place of pads, solder maskopening, holes,silkscreenPlace 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.



13/19

LOGOCopper exposed may be viewable oncircuit board edge or insidecutouts 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 withcutouts:

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 ofthe board edge to prevent exposed copper.



14/19

LOGO

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 scoreline 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.



15/19

LOGO

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.



16/19

LOGOiscrepancies of unit board or a paneldimension

:

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 dimensionsfound 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.



17/19

LOGOWe 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 holduntil these discrepancies are resolved.



18/19

LOGO

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19/19

Thanks for your time!Jing Song

Tel: +86 755 8693 6426

E-mail:[email protected]

Skype: caringcircuit

www.caringcircuit.com

No.12 Building Zhongxing City,Chuangye

Road,Nanshan,Shenzhen,China
mailto:[email protected]://www.caringcircuit.com/http://www.caringcircuit.com/mailto:[email protected]

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