Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

previous by date index next by date
previous in topic topic list next in topic

Subject: Re: [Homebrew_PCBs] Re: A $500.00 "UV" non-trivial exposure box.....

From: "Stefan Trethan" <stefan_trethan@...>
Date: 2005-11-17

You guessed right, relatively thin cardboard. maybe 0.5mm. Like the big
parts of cornflakes boxes.

Again, the procedure:
You cut your layout pretty close to the board edge, but with 2cm border on
one side (same side both layouts).
Then you put together the toner sides, and slide around holding against a
light until it matches.
Now you should have prepared that cardboard, folded in the middle, well
larger than the PCB, because you open the folded piece with one hand, and
slide the layout in with the excess border towards the folded edge. Now
you hold the three pieces together with your other hand, from the outside
of the cardboard, on the folded edge. This allows you to slide the PCB in
and position (this is why you had to cut it close to the board outline on
all but one side, makes positioning easier). Let the cardboard close and
simply hold the stack together (pressing at the PCB). Feed the whole thing
folded edge first. Depending on your fuser you might want a second pass
flipped over, or even two more runs with the cardboard missing. The paper
should be stuck fast by now.

The strange thing is, if you do this without the cardboard the fuser will
"drag" one paper forward, at the board edge. If you imagine the papers
beeing together with zero distance before the board, and 1.5mm then,
there's a 1.5mm length to be taken from somewhere. With the cardboard
feeder, although it makes a crease in it where the board starts, there
seems to be no such movement.

The fuser could easily take the added thickness without modification,
dunno about other machines. But you can also tack it with a iron if you
run into trouble. Then you needn't even use the cardboard, as the iron
doesn't move anything.

ST

On Thu, 17 Nov 2005 04:09:12 +0100, Ron <mnphysicist@...> wrote:

>
> Could you elaborate on the folded cardboard? I'm having a problem
>
> visualizing exactly what you are doing. I'm assuming you tape the
>
> copperviews to maintian alignment, and then slip them into the folded
>
> over cardboard to hold them and the pcb laminate static during the 2
>
> passes through the laminator.
>
>
> Also, did you have to mod the laminator to deal with the thicker
>
> stack? Then again, I tend to think of cardboard as 3-4mm thick,
>
> perhaps what you are using is thinner.
>