Homebrew PCBs

Stefan Trethan wrote:
> On Sun, 29 May 2005 07:52:38 +0200, Robert Hedan  
> <robert.hedan@...> wrote:
> 
> 
>>And now for the really stupid question:
>>Do you print on the inner surface of the roll?
>>I tried that and I'm getting decent printing, but the transfer is a total
>>zero.
>>Robert
>>
> 
> Robert, you are seeing much the same thing i saw back then when trying  
> baking paper.
> The coating is just too slippery to hold the toner. The back allows  
> printing because it is not coated.
> 
> It seems, baking paper works only with certain printers and or for certain  
> people.
> 
> If i were you, i'd try silicone coating with high-temp silicone. The  
> difference is the surface is kind of sticky.
> 
> 


Ok here are my results and what I see..

   First off, mainly used the outside so far since it's smoother.  Going to try 
the inside since it may be better, never can tell.

   S, this stuff is impregnated.  While there is a small texture difference, 
it's the paper not the silicone, or the silicone on that side had a rougher 
roller.  Both sides print equally well, and there's nothing in the instructions 
to say cook on one side.  You can barely even feel the difference it's so 
slight, I'm sure most of the general public wouldn't ever notice it.  The other 
still may be slightly better but the sheet I have is excellent, I'd say the 
problems are mostly not with the sheet but heating and board problems.  Makes me 
appreciate that a large part of how well my inkjet paper TT worked was the 
coating on the paper binding it together better.

   Toner is sticking fine for printing, it is the transfer that is a problem. 
Did much better when I preheated the board 2 passes with a paper to protect it 
from oxidizing from the heat and air.  Then put on the print and did 4 passes in 
or so.  Did ok but not perfect, I'd grade it about 75%.  Really about 95% of the 
toner of course, just breaks etc.

   Most of the breaks are on scratch lines etc from cleaning.  The sections that 
transferred near 100% where where I'd done the best job of prep.  I think that a 
simple system to clean the board without scratching, and then burnish it to good 
smoothness may make it an excellent method.  A cheap electric disc 
sander/polisher ($20 or so) wouldn't add much to the cost or complexity if it 
let you use $2 pre-made paper.



   The cheap GBC (Does anyone else say Game Boy Color in their head every time 
they see GBC?) laminator works ok.  But 12-15 min warm up time.  The Xerox 
(there is another brand name for same one) heats up in only 4 mins, so has much 
better heat capability.  You really need the high wattage to be able to keep 
temp when a cold PC board hits it, even then probably a few passes.  Or a good 
preheat of the board, basically what my extra passes did.  Paper and silicone 
are both not great at heat conduction.  The liquid silicone stuff for heat sinks 
is for gap filling, and usually impregnated with a better heat conductor.



   For a really different paper, it just hit me to try and laminate a print from 
my aluminum foil.  Since my printer has little problem with an AL piece, it is 
worth a try.  Should give much better heat transfer than silicone does, and 
smoother too.. :)  Track widths do 'sink' into the paper a bit, but I've got a 
board with wide tracks so it won't matter much.  The lines are a little bit 
thinner from the toner denting the thin foil into the paper, maybe will spread 
back out in transfer.  May have dueling metal foils though, wonder which the 
toner will stick to better.

   And I need to find 1/2 or 1 oz copper foil.  I could easily print with a 
paper sheet carrier to pull the foil through, and then glue the foil to the 
board then etch.


   My direct printing from laser won't quite work with no mods.  It will feed 
90% plus parts of the path by itself, but there are a few places it will hang up 
due to slight bends etc in the paper path.  Basically it has 1 plane then 
another at a slight angle, so I'm going to have to cut the side frames, get them 
in line, and bolt on some of the metal straps from the hardware store.  Still 
relatively simple mod, but a truly straight printer would be better.  Not sure 
if any are out there, I bet they almost all hit low on the rollers and expect 
some small ability to bend.

   Any printers with a truly round roller fuser would be a start, since it'll 
suck in anything aligned too high.  Anyone know for sure their printer has a 
round top and bottom roller fuser please speak up, it'll have less critical 
alignment.  Doesn't even matter to me if the path is straight, none will likely 
be straight enough so all will probably need a mod, just more or less of one.


   Time for some foil.

   Oh yeah big PS.  My old toner cart was HP.  The new one is HP.  Old one was 
definitely better for toner transfer.  Go figure, I think they changed something 
just a little.  Might possibly have been refill toner but from the page count I 
got the printer at I think it was just older original.  New one prints even 
better on page, but seems just a little bit 'thinner', and that makes a big 
difference for transfers.

Alan