Etch resistant pen Question

[MattAnonymous]

Can I just use a sharpie perm. marker as an etch resistant pen?

[niftydog]

according to a search of this forum; yes, but...

it's not ideal.  I searched around here and found the Sharpie Industrial pen was the go.

but by the time you've found one of these you may as well have just bought an etch resistant pen!

[The Tone God]

You can use Sharpies as etch resistant pens but usually you need two coats and it can be hard to get two consistant thick coats on. I only use them to touch up little areas.

Andrew

[Jim Jones]

The Sharpie Industrial types work perfectly...just used one this afternoon actually...  

Jim

[Aharon]

This comes up now and then,you can use several pens but the best in my experience is the Lumocolor from Staedtler.
I used them extensively in the early stages of the hobby making hand drawn PCBs,now I use them for touch ups.
Aharon

[Mark Hammer]

I've used the Lumocolor for over 20 years.  My favourite.  Just make sure that a) you get the waterproof ones,  b) you get a fine tip, and c) you put the lid back on as soon as your done with it.

Note as well that it is the medium that the pigments ride on which provides the resistant coating, and not the pigments themselves.  I've used assorted colours over the years that looked considerably less "dense" than black and they worked fine.

That being said, I generally use two colours of Lumocolors, a lighter colour for my first coat, and a darker one for my second.  Using two colours helps me keep track of what I've gone over already and what still needs a second coat.  And of course, to do that, the first coat needs to be lighter in colour than the second.  Red and black is a nice combination for that purpose.

You CAN successfully combine things like pens and rub-on transfers.  IC pads are a bugger to draw neatly and line up, so I often use rub-on transfers for IC pads and then link them up with pen-drawn traces.

Both Sharpies and other pens have the nasty habit of being stiff and porous enough to rub off a bit of copper from the board's surface over prolonged use.  This plugs up the holes preventing free ink flow.  You can fix this by simply providing a spare surface to draw on and reflow the ink.  Sharpies have an advantage over the finer-tipped Lumocolors when it comes to covering large areas (e.g., ground planes) quickly, although the medium-tipped Lumos can do a nice job as well.  Fine-tipped Lumocolors are obviously what you want if you need to draw narrow gauge traces.

Whatever you use, keep the board clean.  "Finger juice" has a way of corroding the surface of the bare copper and slowing down etching.  Anything that slows down the "vertical etching" (from the surface to the bare phenolic or fibreglass) increases the likelihood of "horizontal etching" (eating away at the sides of traces and pads).  This can lead some to attribute the problem to the pen, when really it is the state of the copper on the board.  There are many ways to do it, but the objective is to separate your fingers from the bare copper surface when drawing.  I like the "onion skin" paper that comes on the back of rub-on transfer sets since it has very low tack, is non-absorbent, keeps its shape, and is translucent enough that you can see the pattern underneath.  You can use plastic sandwich wrap, or the side of one of those anti-static bags too, though.  Whatever lets you draw well and keep the board clean.  Of course it helps to buff the board shiny first.

[petemoore]

Thank You Mark!
  Mark Hammer's out another great article !!!

[Joep]

Hi Mark,

Which Lumo do you use? I have a 313 here, that one is black, watterproof and a small tip. I remember the 317 also.....but not sure....

Bye,

Joep