Homebrew PCBs

You may have mentioned it elsewhere and I did not see it, what are you
using for the laminator?


--- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <homebrew-pcb@...>
wrote:
>
> Brian,
> 
> The foil actually only is suposed to serve as a carrier for the dry
film 
> laminate on both sides of it. The one I use is less than one mil thick, 
> and I suggest to use the thinnest one you can get hold of as long as
you 
> manage to laminate it which is not all that hard. Just make sure to
feed 
> your laminator in a direction in which the foil was not originally bent 
> cause otherwise there is the risk that the foil wraps itself around one 
> of the rols of the laminator (been there, had to disassemble/reassemble 
> the laminator :-( ). The extremly thin aluminium foil is also the
reason 
> why the aluminium is etched away almost instantly (with some impressive 
> bubbling, smoke and even some heat :-) ) when dipping it into Fe3Cl at 
> those spots where the dry film laminate was developped away. You truly 
> don't need any air agitation for this etching process. Dipping is 
> enough. I usually dip it shortly, then rinse and check if still 
> aluminium is there. Somethimes it's necessairy to stick it back into
the 
> developement bath, then back into the etchant. After two or three
cycles 
> the stencil will be perfect! The dry film then gives the alluminium at 
> those spots where it's really fine some aditional strenght. I do have a 
> PC microscope but for some reasons it does not work at the moment, so 
> the biggest magnification I can do here are my 8 times magnifying 
> googles and using them I can't tell if there are spots where only 
> dryfilm is present or if the aluminium is still there. The all
important 
> point though is that even if the aluminium shold be gone, the silk 
> screenig of the solderpaste works without problems for me.
> 
> I think though that my end resulting stencil is probably not so far
away 
> from a mylar stencil. I never had one, but I figure structures that
fine 
> will break easily anyways no matter what material is used. So care must 
> be taken not to bend the stencil sharply. I was however amazed to see 
> how strong it was. The stencil kind of sucked itself to the PCB surface 
> and I've ben able to rub in all directions to truly evenly spread the 
> paste. Raising it thereafter was also no problem and thereafter all
fine 
> structures at the stencil were still ok. Needless to say that they were 
> also present on the PCB.
> 
> You may have noted that I took a plastified card of a cardgame as the 
> spatula/squeegee. They are IMHO fairly well suited for the job, can
even 
> be cleaned thereafter (reused many times) and dirt cheap (just make
sure 
> you take your sons yugioh (spelling?) or pokemon cards AFTER he grew
out 
> of it!). Since they are made of cardboard, they do not scratch up the 
> stencil and by bending them more and less you can easily press the 
> solderpaste down to the PCB.
> 
> The stencil ideally should be 4 mils thick to end up with the propper 
> amount of solder paste on the pads. Since using my method you end up 
> with a stencil of that thickness, subsequent soldering is no problem.
> 
> I've so far not been able to clean the stencil after use cause all the 
> fluids I tried so far destroyed the dryfilm laminate. It's no
problem to 
> use the stencil for multiple PCBs while you are at it. Just if the
paste 
> dries it's (so far) over. However that's really no problem for me cause 
> I a) anyways only produce prototypes (5 pieces of one PCB is a hughe 
> quantity! :-) ) and b) since it only takes 15 minutes to creae a new 
> stencil and since the material costs is close to nothing that doesn't 
> bother me. The time saved compared to hand soldering, and the perfectly 
> looking result way outweight it.
> 
> As mentioned elsewhere I'm in the process of creating a website with 
> tutorials on how I create my PCBs and how all the equipement I use was 
> made with descriptions and pictures for those intersted in building
part 
> of it on their own etc. etc. I then also will upload sample pictures of 
> projects done this way.
> 
> Markus
> 
> Brian schrieb:
> >
> > Never thought of this. Cool idea. You said to use thin foil, when you
> > apply the paste do you have a problem with the foil between the pads
> > breaking? and if so does it matter since when it reflows it sucks
up to
> > the pads? Also, using thin foil, is there any problem with having
> > enough solder to make a reliable solder joint? Do you have a
picture of
> > the final board?
> >
> > Brian
> >
> > --- In Homebrew_PCBs@yahoogroups.com 
> > <mailto:Homebrew_PCBs%40yahoogroups.com>, Markus Zingg <homebrew-pcb@>
> > wrote:
> > >
> > > Hi group
> > >
> > > Under the folowing path in the files section you find a description
> > on
> > > how to create your own fine pitch stencils. There you also see
how to
> > > apply solder paste with it. The example given is made with one
of the
> > > (four layer) PCB's I created here at home.
> > >
> > > Files </group/Homebrew_PCBs/files/> > PhotoEtching
> > > </group/Homebrew_PCBs/files/PhotoEtching/> > solderpaste and stencil
> > >
> > > I hope this helps others. Enjoy!
> > >
> > > Markus
> > >
> >
> >
>