Homebrew PCBs

It seems there are two bondings going on here:  toner to paper and 
toner to board.  The goal is to increase the ratio of bonding to the 
board vs bonding to the paper so the paper will release.  Of course 
there needs to be a minimum level of bonding to the board.  coated 
paper works because the toner only bonds to the board-side layer and 
soaking causes the layers to seperate.

The starch method of decreasing paper bonding is very promising but 
I've not been able to get smooth enough paper to feed cleanly.  My 
best effort got creases and spacial distortion of the transfer 
pattern.  I'm skeptical of this working well for 8 mil traces and 
tqfp packages.  I've got some 90 lb paper that might maintain its 
integrity during starch treatment and will give it a try.  There may 
be other products that don't wet the paper but decrease the paper-
toner bonding. a very thin coating of a light oil (wd40 springs to 
mind) might do it.

--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
> Stefan Trethan wrote:
> 
> > I thought so too first ;-)
> > i thought gravy, with the fat/grease and all, that is never
> > going to work. (i didn't believe my dictionary)
> > 
> > but then, when it was said to use flour or starch i can well 
believe it.
> > i may actually try it some day too...
> > 
> 
> 
>    Yes, same here.  The idea is more understandable when you 
realize that this 
> is more familiar to most as paper mache glue not really gravy.  
Sticking to the 
> page yet releasing easier than the paper makes much more sense 
then.  I'll be 
> trying it out today.
> 
>    And he just mentioned that large areas don't work as well.  They 
work fine on 
> the jetprint paper, but I suspect that may be as much his printer 
as the paper. 
>   All lasers have some degree of less printing on large areas, part 
of how they 
> work.  Then again the glue covered paper could be interfering and 
making it a 
> bit worse.  Conductivity can interfere, so if my initial prints 
aren't perfect 
> I'll bake a sheet or two so I know it's completely dry.
> 
>    Even with some extra prep work it's all very simple, as long as 
the rest 
> works as well or better I'll switch.  No sense bothering to buy the 
other papers 
> if this little bit of prep now and then makes something as good out 
of regular 
> paper.  And I like the idea of being able to control your coating's 
consistency, 
> that means things can be adjusted until the best point of toner 
adhesion and 
> later release from the paper are found.  I'm following some PM glue 
> instructions, but I'm going to try consderably less water than 
called for since 
> PM is only trying to make a very sparse coating that just glues 
here and there. 
>   Shouldn't need so much water even for a thin coating when 
actually trying to 
> coat the page.
> 
> Alan