Homebrew PCBs

On Thu, 06 Apr 2006 04:21:05 +0200, Robert Hedan  
<robert.hedan@...> wrote:

> Even the thin border line and super small text stayed on.  They
>
> usually fall off from being too close to the edge and not getting
>
> enough heat or pressure.

I have a theory on the "otline problem":

I notice a very small shrinkage when the paper cools after fusing. What if  
this shrinkage pulls the paper in and breaks the small outline off?

There is a simple workaround - i put another, wider outline around the  
whole board just outside the real one. Sometimes that will go partially  
over the edge of the PCB piece but that doesn't matter since as long as  
there is a little left it will protect the outline.

I find if i use a ground plane the effect is strongly reduced already,  
although sometimes flakes of the very outer edge get pulled off, so i also  
use a wider "sacrificial" outline here.

>
> The only drawback is a
>
> slight skew in the image, but that might be because I'm printing only
>
> on the right side of the page instead of dead center.  Yup, I screwed
>
> up when I refilled the toner and put a tiny scratch in the center of
>
> the drum.
>
>
> The problem with the skew is that the 2 sides cannot be perfectly
>
> aligned into a 'sandwich'.  I have to compromise a little and make
>
> the pads for the vias slightly larger, no big deal.


Get the service manual for he printer, skew can usually be adjusted out  
easily. There are normally two adjustments, one to turn the laser assy (to  
get a line parallel with the LE of the paper) and one to make the paper  
run straight (to get a line parallel with the side of the paper).

ST