Homebrew_PCBs

I had some really crumby results with using nail polish as acid resist
so I had no great expectations from enamel hobby paint
BUT THIS WORKS GREAT!!!!!!
My search for a readily available acid resist for PCB touchup or hand crafted etching is over.
I painted on the copper with the thinnest paint brush I could find but I am certain this
paint would flow freely from a fine point technical pen or dip ink pen to make SOIC traces.
pictures:
  http://www.learnmorsecode.com/laminator/etch/enamel.html

Use a Silver sharpie for touch ups or simple circuits. Over the counter
goodness, needing no extras or special skills.

I did use the Silver Sharpie and had terrible results.
It burned off the PCB and floated just like India ink did.
It left streaks of etched hairlines inside 1/8th inch traces.
More than once.
So...nope... no Silver Sharpie for me.

I thought maybe it was an age issue becuase I do use silver sharpies to write on
black plastic cases..... so I tried a second time using a brand new fresh silver sharpie...
and got floaters.

My test method is VERY consistent.
The copper PCBs all come from the same source.
I scrub until shiny and scratches with very fine sand paper then
wash clean with acetone.
THEN
apply thin ink line for testing.
I make one pass with a marker and usually leave just enough pigment to be translucent
and then I apply a second coat..... usually then being the dark color its supposed to be.

BUT
the enamel craft paint went on translucent where thin... dark black where thick (paint brush)  and I noticed that even those very thin layers blocked etching.... much better than my silver sharpies ever did.

MY etch mixture is 100ml of 3% hydrogen peroxide and 50ml of 30% muriatic acid.
My etch time is usually about 6 minutes.

It has been extremely consistant results again and again so I am very pleased with this process.
My quest for a good etch resist is driven by the fact that the readily available sharpie products failed me....
drying out before I was finished touching up a board.... and then the silver floaters and streaking.
The sharpies drying out might be just be because I take much much longer to trace over toner traces than normally done by the rest of you all with good vision. 
So if I have to resort to a wetter etch resist...like craft paint in a bottle... then I'm OK with that idea.

 

Use a Silver sharpie for touch ups or simple circuits. Over the counter
goodness, needing no extras or special skills.

Posted by: AncelB <mosaicmerc@...>