kicad-lib-committers team mailing list archive

[Carl Poirier <carl.poirier.2@xxxxxxxxx>]

Thanks for the clarifications. I will commit that shortly.


On Sun, Jun 8, 2014 at 11:35 AM, Jean-Paul Louis <louijp@xxxxxxxxx> wrote:

> Let’s get back to the basics.
>
> WHY A SILKSCREEN?
>
> Originally, PCB were assembled by hand, and the markings were dual
> purpose, Assembly and Inspection.
> They were printed on the PCB using colored paint and silk (plastic) or
> metal screens, So the outline of the component was helping the operators to
> stuff the board, and the RefDes was to make sure you were using the right
> part, and also for trouble-shooting a failed test.
> When the board is fully assembled, the outline is meaningless, only the
> RefDes keep its value.
>
> And there is no difference in purpose between Through Hole and Surface
> Mounted parts.
> For polarized capacitors, I have seen a lot of different options, the most
> efficient one being a circle or a square with a “+” sign to show the
> polarity, The “+” sign or sometimes a dot being outside the shape.
> What is important is that the marking eliminate ambiguity, but does not
> jeopardize reliability. So it is VERY important that it does not touch or
> cover a solder area.
>
> my $0.02,
>
> Jean-Paul
> AC9GH
>
>
> On Jun 8, 2014, at 11:14 AM, Carl Poirier <carl.poirier.2@xxxxxxxxx>
> wrote:
>
> > About these rules for the silkscreen, are they only for SMD? I am under
> the impression it does not apply well to THT components, for example an
> electrolytic capacitor where we often see a circle with one half full to
> indicate polarity. This would be partly hidden once the board is assembled.
> >
> >
> > On Thu, Jun 5, 2014 at 5:24 PM, Bernd Wiebus <bernd.wiebus@xxxxxx>
> wrote:
> > Hello Pawel.
> >
> > Am Montag, den 02.06.2014, 09:57 +0200 schrieb Paweł Dras:
> >
> > > With pads over the silk is the same situation, in many cases after
> > > silk erasure by solder mask it don't looks good on final product.
> >
> > It is not only about "looking good". Silkscreen print over Pads is
> > nasty, if someone forgets to distract the pads from the silkscreen.
> > It may be expensiv, but shure will cost time at last.....
> >
> > If you place your silksceen across pads, and erase it over the pads,
> > your silkscreen will be chopped. so better you chopp it by yourself and
> > make it looking good.
> >
> >
> > > Another problem is to wide placed silk.
> >
> > Think about, that you perhaps need place for rework tools.
> > And wave soldering needs more space around the devices than reflow.
> >
> > Some years ago, KiCad insisted in thik lines, because you could not
> > change the wide of silk screen lines. Of course, it was possible by
> > editing the library file by hand.
> >
> > But this thick lines are sometimes needed, because a manufacturer who
> > use a real silk-screen printing process and not a optical process, meeds
> > the wide lines.
> >
> > So bee careful, if you use thin lines. Think about the spacing.
> >
> > > I have a question, can be ref and value placed as in my attachment or
> > > should  be above and below resistor?
> >
> > It is a bad idea, to place text under devices, because it cannot be read
> > anymore, if the device is once mounted......so i put text to this
> > positions, only if there is nowhere a better place for the text.
> >
> > Personally, i switch the value at layouts and silkscreens to invisible,
> > and keep only reference as a designator.
> >
> > Having reference AND value at the layout costs place and is terrible to
> > read. So better i use only the reference, and the BOM of course. ;O)
> >
> > For big boards with few devices, it migt be ok to have both, but for
> > growing sisze, it will get diffcult to read.
> >
> > the exeption is, if you use the silk-screen not as an silk-screen at the
> > board, but as an assembly layer. So you are not stuck to board
> > dimensions, but can make DIN A2 prints for boards the size of a small
> > stamp. ;O)
> >
> > With best regards: Bernd Wiebus alias dl1eic
> >
> >
> >
> >
> >
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>