Thanks budd, you are right, easier and quicker. And Gerber files look so cool, just discovered them for the first time.
The days when a PCB price depended on the number of vias, went away decades ago.
It’s all about board size, number of layers and any special processes these days
I don’t understand why a PCB only service needs a BOM
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I just checked in 6.0.5 and if I make a reference invisible using properties, it is hidden in the 3D viewer and not plotted in the Gerber file, so the 3D viewer is showing what you will get.
To restore them in the Gerber, you have to go back to PCB and make the reference visible and then replot the Gerber
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look at the sample of the file i have shared. I f i print this file for the gerber files, their will be no writings on it or even any lettering because gerber files control what should be printed and not the wording.
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We never send BOM to PCB only manufacturer.
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This is strange. Were you dealing with a web form, or with a customer rep who (doesn’t know what they are doing / was trying to upsell you PCBA services / was thinking something else)? Have you asked them?
This was actually the owner of the firm, was supposed to know his job.
No I didn’t ask, but just sent the gerber files, intending to wait for the guy to ask for the BOM again and then see. The request hasn’t come yet, but the quote has, so maybe he doesn’t want it anymore.
Thanks. How to make the reference visible again. Can’t find that functionality.
Ah well these days it’s hard to hire good help. 
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Select the footprint and Update the footprint from the library, with the Update/reset text layers and visibilities box checked
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I do not know why he would want the BOM. Here are two speculations.
- It is simply a mistake, or misundersanding.
- With the BOM one can get a good idea of the cost of the finished PCB, and thus how critical the cost of the bare board is in the greater picture. This could ‘help’ in making a quote.
Or the worst case - to steal the design
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Yeah, but in any case that guy is off the project. At his quoted price I could get the PCB made, mounted and shipped from china, DHL cost included.
KiCad can produce gerbers in X2 format. I do not claim to understand much about it but these gerbers contain some intelligence. It is not just a dumb image; with X2 format and the right gerber viewer, the viewer can find reference designations for example. This is not true for older gerber formats. I do not know whether this functionality will work if ref designations are not plotted, but I would not bet against it.
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Gerber X2 indeed can contain the reference designators, but it does not have to. AFAIK the fabricator does not need these. Without BOM the refdes do not reveal much IP.
However X2 contains many things the fabricator needs to know: what the file represents, e.g. top copper, what holes are plated or non-plated, where the via’s are, the BGAs etc. And it can contain the netlist, which is unfortunately often missing.
Change that into: It can contain the netlist in textual format, with the same net labels as used in the schematic.
Gerber files always contain the netlist, because it is implicitly defined by the layout of the tracks.
I’ve recreated some KiCad projects from a schematic in PDF and a set of Gerber files:
If mistakes are made during schematic entry then the PCB will end up with DRC errors, and you have to examine and fix the differences.
Maybe it is just a misunderstanding. You wrote that manufacturer was quite expensive, maybe he quoted you for a price inclusive assembly, which of course needs the BOM.
Yes and no. The Gerber file unequivocally reveals whether two points are connected. Only the geometry is needed. If you know the locations of the net endpoints, you know the net. However, do you know the end points? You can make a good guess from the traces, but it is far from perfect. Consider pads embedded in copper pours, etched components, non connector copper such as text and logo’s. Non-connected pads still need to be isolated from other nets. A trace can connect to a copper pour, which is not an endpoint. From the geometry you can make a guess at the netlist, but it is not reliable.
Remarkably, most fabrication data sets do not contain an explicit netlist, but the fabricator is expected to do an electrical test. That is paramount to telling the fabricator: “You must test the netlist, but what the netlist is, you guess.” It is one of the mysteries of this industry that this is the established workflow. With an explicit netlist, there is no need for guessing.
Adding the netlist has another advantage. If there is any error in the output or input of the Gerber files, chances are that it will change the netlist. The fabricator can check whether the geometry fits the netlist. Thus adding the netlist is a very powerful checksum on the image. I consider it completely daft that this is not used routinely.
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Over the years manufacturers have become quite good at guessing pads in gerbers, but in the older versions the concept of a “pad” did not even exist. It’s just flash codes at some locations. (flash codes are like postage stamps. you stamp the form of it somewhere on the PCB. Even if a pad is not visible (in a zone, no thermal relief) the flashcode may still be there, and also on the solder mask layer.
In newer Gerber revisions X2 or X3, the full netlist and all pad locations can be embedded and this removes the need for guesswork, and makes automation easier. One use for this is flying probe tests. But this needs pad locations, and not the BOM.
One use of the BOM could be to check for mismatches between the parts and footprints.
Edit:
If you’re interested about gerber details, the Gerber format is maintained by Ucamco (a manufacturer of gerber plotters) and the standards are freely available.
Currently KiCad also only supports a sub-set. the newest (X2 or X3) version for example specifies a specific layer for V-grooving and it has features for defining “copper items” such as PCB inductors and closed solder jumpers, so more guesswork can be eliminated for things such as flying probe tests.
True, fabricators are good at guessing the netlist. They have to. But it is guessing. As so often in this industry, we do not solve the root problem, but live with the problem, and organize ourselves around it.
Also true, with X2 the pads can be identified unequivocally, and then the netlist can be determined from the geometry, without guessing. But the netlist is still a powerful checksum, one wonders that it is not included more often. Note that this is regional, the vast majority of US datasets contain the netlist. Not in Europe - a self-inflicted competitive disadvantage.
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