Questions of a newby ons different subjects

[RikV]

When I want some parts of my PCB to have exposed copper surfaces, how do I proceed? Adapting the .mask wille leave the copper opened but finished according to HASL or ENIG selection. I do not want that in this case, realy pure copper surface is what I need. Is there a way?

[Benta]

That's a question for the PCB manufacturer. KiCAD has nothing to do with it.

[SiliconWizard]

Each manufacturer will have their rules and requirements about that - a few may not even offer this possibility.

If they do, they'll pretty much each ask for something different, so yes, just ask.
A general safe bet is to create an additional custom mask layer with the areas to exclude from finish.

Note that no finish at all is an odd choice. Raw copper oxidizes extremely quickly, and if there are unfinished areas right in the middle of finished ones, copper may start oxidizing at the edges of the finish and eventually damage the PCB over time. What do you want to achieve?

[RikV]

So it is not standard practice to have blank copper surfaces. Indeed, it oxidizes quicklybut it offers the best thermal conduction when treated properly. I hoped it was possible to include this demand in the Gerbers . Well, there are ways to remove the solder mask.
Thanks for clarifying.

[Benta]

It's not a problem making holes in the solder mask, KiCAD can do that.
The issue is: what's the manufacturer going to do? Tin-plate it? Gold-plate it? HAL-surface? Leave blank?
Only the manufacturer can answer those questions.

[Doctorandus_P]

I agree with the others here, you have to talk to your PCB manufacturer. Sometimes parts of the PCB are temporarily masked with tape, for example to mask of holes during wave soldering if things have to be added later. This can also be used to mask of ENIG of HASL.

But also, this has nothing to do with KiCad. It's a generic PCB manufacturing question.

In modern Gerber variants (Such as X3) a lot of extra's have been added. It is for example possible to define V-Score lines directly in the Gerber files, and masking parts off may also be specified. (I have not checked) However, support for features like this is very slow in the PCB manufacturing industry. The Gerber standard is freely downloadable from the Ucamco website.

[Chat GPT]

Yes, there is a way to create exposed copper areas on your PCB. Here are the steps:

Open your PCB layout in KiCad.
Select the "Zone" tool from the toolbar.
Draw a closed polygon around the area where you want the exposed copper.
Right-click on the polygon and select "Add Filled Zones" from the context menu.
In the "Filled Zones" dialog box, select "Copper" from the "Net" drop-down list.
Set the "Clearance" to a value that will allow for the size of the exposed copper area you want.
Set the "Min thickness" and "Max thickness" to the desired thickness of the exposed copper area.
Click "OK" to create the exposed copper area.
By creating a filled copper zone with a clearance that is larger than the traces and pads in the area, you can create a copper area that is not covered by solder mask or any other finish. This will give you a pure copper surface.

Note that if you want to create multiple areas of exposed copper on your PCB, you will need to create a separate polygon and filled zone for each area. Also, be sure to check the design rules for your PCB manufacturer to ensure that the exposed copper areas meet their requirements.

[JohnG]

You could try an OSP finish instead of ENIG or HASL. For example, see https://www.pcbway.com/blog/PCB_Manufacturing_Information/Organic_Solderability_Preservative__OSP_.html. It's a pretty fragile coating, and I would guess it is easily removed with some solvent or other. Certainly hot flux will remove it.

If you want to selectively coat some mask openings with OSP and other opening with something else, I don't think any PCB house will do that, or it will be real expensive. It's generally all or nothing.

John