I’m trying to make a PCB using the photoresistive film. To test the future image I have printed the PCB on a piece of white paper (using “Plot” menu item and then saving to PDF). The resulting image made me sad:
the spaces between IC pads are too small;
the tracks that are assigned to be 0.4 mm in thickness actually 0.8 mm. The spaces between tracks are also too small.
What I do wrong? How to make pads and tracks of the proper size?
I run KiCad v5.1.4 for Ubuntu.
So the tracks on paper are clearly wider than on the gerber.
What are you attempting to do with the print out? It’s clearly not dark enough nor transparent enough for home etching.
Maybe something went wrong in the .pdf generation in KiCad, but it seems more likely that your pdf viewer or printer settings try to help yo by “enhancing” black lines.
I’m going to print the negative PCB image on a transparent film (to use it as a template for photoresist).
It seems like PDF file has low resolution (lower than it should be for correct printing). What is the correct way of printing negative images? I have no ink printer for transparent film so I have to export file to bring it to a printing service.
Give a screenshot of your Plot dialog which shows all settings.
BTW, I’m not sure what you’re going to do, but remember that the bottom layers are mirrored! If the etched board has the pattern of your pdf, you can’t install your components in it.
Home etching is an error prone process, especially if you go down to (what looks like) 0.8mm pitch QFP’s
With 10 PCB’s for EUR10 from China you also get much better PCB’s then you can hope of making yourself (Double sided metalized through holes 2 solder masks and 2 silk screens and the nasty FR4 stuff cut to size) All this with just a few mouse clicks…
With home etching there are a lot of variables to take care of, and each process has it’s own pro and con’s.
Marco Reps has experimented with UV dry film on the PCB and a UV led or laser for directly drawing into the dry film. BigClive also has made a nice youtube vid of his process of home-etching PCB’s.
There is also milling, but it’s also difficult to get the required resolution.
Yet another method is with a pen plotter and a thin felt tip pen with etch resistant ink, and then draw directly on the PCB. This has been used with success by some as early as the 70’s.
In these “modern times” “high resolution” is often used as a gimmick word and manufacturers of (consumer grade) electronics do all kind of stuff to make stuff look good to casual observers (such as smooth lines) but not real accuracy. Also multiple layers of “enhancement” of pictures by photo programs, laser printers and other equipment.
One way of fine tuning your process is to make a test PCB with different pitch components and track widths and clearances, and get that PCB through the whole process and look at the final etched result. I’ts probably the fastest way to a process that works for YOU.
SVG is also a pretty common format. You can probably also do your own post processing to modify line widths or convert to a format that your printing service accepts.
Printers, and printer drivers, have also been known to scale printouts to “fit” a page. Or perhaps that is, “fit” the page after subtracting the printer’s hardware margins.
At its foundation, the *.PDF format is designed for presenting text and graphics to human eyeballs (and the perception system behind those eyeballs). Unlike Gerber, it’s not designed for presenting information to machines, with accuracy and precision. I have neither knowledge nor experience in such details but my intuition suggests that the .SVG format is worth investigating. Another possibility is the postscript (.PS) format. Back in the early 90’s, I seem to recall some people suggesting that postscript should replace Gerber as the standard file format for PCB design.
(At it’s core, “postscript” is not a file format but rather a high-level programming language. The operators and structures defined in postscript happen to be especially useful for describing how to place ink on an otherwise clean sheet of paper. Postscript is also one of the few programming languages based on a data “stack”, and a form of reverse-Polish notation (RPN).)
The ex-YAHOO group “Homebrew PCBs” seems to have morphed into " Homebrewpcbs@groups.io ". It appears to be rather inactive, but perhaps you can find helpful information in their message archives. You may also get help from other Forums in the “Maker” or DIY community, such as DIY Audio.
I need home made PCB at least for test reasons. If my board has a bug I will recognize it only two or more weeks later needed to get parcel from China. No mention about wasted money…
Meanwhile, I was able to convert SVG file into a PNG of pretty good quality using GIMP. The point is to define the correct sheet size and the resolution of 600 dpi.
Do you have any experience with programming?
.SVG is a vector format, Open sourced, well defined and very likely multiple libraries freely available in any decent programming on this ball of dirt we’re living on.
It is probably very doable to write a little program to change track thicknesses and such.
Does your workflow leave hole marks for centering the drill? If it does not, then those can probably also be added pretty easily.
