Homebrew PCBs

On Mon, 20 Jun 2005 10:05:08 +0200, Philip Pemberton  
<philpem@...> wrote:

> The best thing I've used is 600-grit 3M "WetOrDry" silicon-carbide  
> paper. Put
> the board in a bowl full of water, then use the wet-dry paper to remove  
> any
> dirt on the board. Rub in two orthogonal directions, then lift the board  
> out
> of the water. If water beads up on the surface, give that area a bit  
> more of
> a scrub. When the board is perfectly clean, the water will form a
> more-or-less solid "sheet" on the copper.
> Takes about 10 minutes to do it properly, but it gets all the crap off.  
> Same
> trick works for removing the toner, though I sometimes use acetone for  
> that.
> Spray the board with flux after you've removed the toner.
> I'm going to try and get hold of a pair of broken Laserjet III printers  
> at
> some point. Hopefully it shouldn't be too hard to build a controller for  
> the
> fuser. Need to get a thermocouple or a PT100 sensor first though (to set  
> the
> trip point on the temperature controller).
> Just out of curiosity, what temperature are you guys running your fusers  
> at?
> Later.


I had expected it to be rather difficult to clean a board with water only  
and paper, but it seems it isn't that hard (a bit time consuming tho.)

Anyway, if you want a "dry" approach dry sand the board with the paper,  
and then wipe with acetone and a paper towel. The paper is quickly clogged  
up in dry mode, but you only need small pieces and it's cheap. Takes less  
than a minute. There's also 1000grit paper which gives a less scratched  
finish.

I would use sanding sparingly, as the copper is very thin to start out  
with. It isn't hard to sand it off at the edges. I usually just sand  
enough to get sandmarks all over the board and not more.

For taking the toner off, i use a steel scraper. just scrape it off dry  
and rinse with water. Works very well. Haven't managed to damage a track  
yet, seems difficult. Acetone works but i don't see why i should waste it  
if a mechanic approach is that easy.


The LJIII has the fuser unit easily removeable, and has a thermistor on it  
as any fuser (still need meter for initial adjustment). There might even  
be a triac on that small board on the side, not sure. I guess you would  
need to get one of the gears out of the printer too, or find some other  
way to drive it. I don't remember if it is easy to modify for thicker  
material.


I'm running my fuser at 160C.


ST