Homebrew PCBs

On 01/01/2014 11:52 PM, seeifyoucanmeetme@... wrote:
>
> Hi everyone,
>
>
> I've been using the toner-transfer method with vinyl for some time 
> now, but I'm consistently running into a pitting issue across all of 
> my boards.
> On large polygons/planes, and even on fine traces, pits and weathering 
> appear on the surface of the copper.  I've added an image in a link below:
>
> https://drive.google.com/file/d/0B4daAsGd6n41aGRRY3QyeVlaS28/edit?usp=sharing
>
> Where the image appears clean, I covered that surface with a sharpie 
> in addition to the toner.
>
> My printer is a Samsung ML-2525. 1200 DPI. (Toner set to transparency 
> and max darkness setting.)
>
> Vinyl is from a local sign retailer.
>
> Currently, I'm not sure if the pitting is from insufficient toner, or 
> from the vinyl, although the vinyl pretty-much always comes out 
> perfectly clean from the transfer.
>
> I picked up some laser foil to try to recoat the board, though I only 
> used it once as I watched it immediately flake off when the pcb 
> entered the etchant bath.
>
> Etchant is cupric chloride.
>
> Thanks for any advice!
> 
> <http://groups.yahoo.com/group/Homebrew_PCBs/post;_ylc=X3oDMTJxNm9oOW4wBF9TAzk3MzU5NzE0BGdycElkAzQ1MDUzNjEEZ3Jwc3BJZAMxNzA1MDgzMjkxBG1zZ0lkAzMyOTk1BHNlYwNmdHIEc2xrA3JwbHkEc3RpbWUDMTM4ODY0NTU2Ng--?act=reply&messageNum=32995>
> 	
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>

I will try to help.  First I use Hammermill Laser Gloss paper, so my 
technique
may be different.

Several things that I have found that help prevent pitting.

1.  I preheat board to 40 deg C before running through a laminator
with paper and toner then applied to the board and repeat through the 
laminator
until the board and paper comes out at 90 deg C.  I use a cheap
IR thermometer to read the temp.

I soak paper off at cool to luke warm temp.  Do not exceed 40 deg
C at which the toner softens or even melts.  Do not soak for too
long a period as this also seems to cause pitting.  Because I am using
paper and toner I carefully rub off after soaking in water about 5 mins
and do not use a lot of pressure.  Just a gentle rubbing using the
thumbs to roll off the paper.  I can do a video if more is needed.

2.  I am using Hydrogen Peroxide and Muriatic acid bath (2 parts HP to
1 parts HCl).  I do not heat above 100 deg F and only if the lab is cool
around 60 deg F.  Do not leave in bath more than necessary to remove
all copper between traces.

You do not say if the cupric chloride is heated.  The reaction is also
exothermic and may cause the temperature to rise and soften the
toner.

Just a few ideas for you to investigate.  It took me a couple of
boards to find the right combo.

And sometimes you might get what I call the planetarium effect
with small pits that look like star fields in the ground plane when 
board is held up to
the light (for single sided boards).

Here is a photo of a board using 0.5 oz FR-4 board.

http://www.k7qo.net/k7qo-photo-0044.jpg

FYI

chuck, k7qo