Prepatory work on Gerbers

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The best thing to do is to send the files exactly as they are created and to also send the following sort of information in both the document that goes with them and a file called "README.txt"

SILF.PLT is the component side silk screen COMPMASK.PLT is the component side solder mask COMP.PLT is the component side copper L1.PLT is the upper internal layer copper L2.PLT is the lower internal layer copper SOLDER.PLT is the solder (bottom) side copper SOLDMASK.PLT is the solder side solder mask

The file 56-6789.dxf is the FAB drawing for this PCB

Mr. Bill Jones Flaky Electronics Corp Phone (123)456-7890

Sending the fab in DXF format means that they can read it with nearly any drafting program. Sending the README.txt in plain ascii means that it can be opened with any word processor etc. You are best off to make the ".txt" part lower case because it appears that some versions of MS word don't know that ".TXT" means a text document.

Never send a ".doc" file or a ".dwg" file. If you do you are likely to get a phone call in a few days telling you that they can't read the file. Your job will have been kicked out the cue and will be delayed by several days.

For historic reasons I still use all uppercase on the plot file names. I don't think this matters any more just make sure you never have two files that differ only in the case of the names.

What is this "fab" drawing?

We need RS-274X format gerber file, and only accept following files: a.. Positive Gerber layers: Top & Bottom (more inner layers for multilayer boards) b.. Aperture/Dcode file (if not RS274X) c.. NC Excellon Drill file d.. Drill Tool list (if not listed in NC Drill file) e.. Soldermask f.. Silkscreen The specs they require such as thickness, finish, dimensions, etc are all given in some form so I do not think they need such mechanical information. They will probably simply check the gerbers against the form information to make sure the quote is accurate(else you could just quote something cheap and send different gerbers).

What I'm a bit confused on is if I should mirror the bottom layer or not. It would be very bad to get a board with one of the layers mirrored ;/ I'm sure they have methods to check against this but it's always better safe than sorry.... (it's pretty obvious in most two layer boards, specially mine, what to do so...)

From the old photoplot days.... to get the emulsion next to the pcb, as opposed to being the 'thickness of the film' off the board, resulting in thin tracks from the photo imaging process....(I'm sure you know what I mean) lol

Here's one:

ftp://jjlarkin.lmi.net/22D346A.pdf

We zip this with the Gerbers and email to the board house.

John

Don't. Send the Gerbers as-is.

Decent board houses make all sorts of manual and automated checks and rarely get anything wrong. They usually call us if they see anything suspicious, like a dead-end trace, a suspected short, copper going all the way to the board edge, like that.

We do label and put alignment targets on all the layers.

John

Check them carefully in a Gerber viewing program, if they look okay then send them out exactly as-is.

too late ;) I just zipped all the outputs. NC Drill file and gerber outputs. If it's not good enough then oh well. Just wish I was a bit more sure on the outcome but I imagine it will be fine... if not then a waste of 400$.

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No, you don't mirror any layerrs. We use the followings for many fabs without problems:

ts (top screen), tm (mask), tc (copper), bc (bottom), bm, bs

If it's a good company, their front end will pick up 99%+ of 'stupid' errors.

Relax, chill out, have a drink.....pat yourself on the back for a job well done :)

The "fab" or fabrication drawing is the one where you show the PCB thickness, and spec things like warp and twist and copper weight and silk screen color.

It usually also has a mechanical drawing of the PCB with the outside dimensions and a few other details like that. The PCB house usually only uses the notes but the picture can be helpful.

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Many years ago, I wrote a program that added the symbols to the fab drawings hole sizes. Nobody needs this sort of thing any more but it was cool because it knew about groups of holes and how to draw a wavy line around a bunch that all needed to be the same size etc.

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I always send the files un-mirrored ei: X-ray view from above.

They only said to include the basic gerber stuff and drill files so thats what I did. They said that stuff like a readme will not be used. Not sure if it would have helped or not but hopefully they'll call if there is any confusion.

"queue"

The Gerbers don't mention material, stackup, overall thickness, copper thickness, colors, tolerances, plating, testing requirements, UL, and (maybe?) not outline dimensions.

John

All of the board houses i used do not mind (mirror or not), but they all agree that "industry standard" is mirror.

That stuff has to be specified somewhere! I suppose some proto houses could have a web form or something where you enter the relevant information and most of the options are just not offered, but I've never sent a PCB out without a readme.txt file (usually just cut and paste and make changes from a previous file).

Besides outline dimensions (and tolerances!) there are V-groove locations and such like that require a mechanical drawing.

The only thing I've edited manually after it came out of the layout program was the Excellon drill file, and that was just to fiddle with the tool diameters (drill sizes) for prototype purposes.

Best regards, Spehro Pefhany

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The *old* DOS Orcad PCB program only worked for hole sizes up to

Lately I have used ExpressPCB to make prototype/breadboard PCBs. There are some things they just won't do but for breadboards it is OK. A local machine shop will do some of the things like slots.

I do my breadboards as large featured surface mount PCBs.

For text jigs we have also started using PCBs from them. If you have a simple circuit, you can use the PCB as the lid of the box. The connectors and controls all come out the back. You screw the PCB face down on the box.

"The Journey is the reward"

eff.com