Homebrew PCBs

This comes in a pack of 25 sheets for $13.99 at Staples - so far the
only place I've seen it. It's 'synthetic', so it's basically a
'plastic' paper. It's extremely thin, as well.

After a little testing I found the best way to transfer is to run it
through a laminator (I use a GBC Creative 9", the $50 one from Staples
that sometimes goes on sale for $30, since I etch brass sheet and not
PCBs) about 3 times. Then to remove the paper, you need to run it
through again and start peeling about 3" after the metal leaves the
laminator. Too hot, and the toner sticks mostly to the paper. The
distance would probably be different for PCBs due to the different
dissipation of heat from the core compared to solid metal sheeting.
Let it cool down just a little, and start to peel, and about 90% of
the toner transfers. I'm sure with practice I could get better results
(the second test I did came out quite well). I made copies on the
Xerox DocuColor 12 that many Staples stores seem to use. I'm hoping I
can encourage more people to test it on different brand printers. I
tried running it on Transparency mode to see if I could get more toner
to coat the paper but the copier just jammed.

http://www.fenrironline.com/test-transfer.tif

Left it as a TIFF to keep the quality as brass doesn't scan well. The
tranfer isn't as nice as it looks - there's a lot of pinholes going on
which I think is the nature of Laser technology and why you need to
use the green TRF film from Pulsar. It's not an issue for me as long
as it only causes pitting, as I use the other side of the brass for
most of the work I do but I know with PCBs that the coat needs to be
pretty solid. I wonder if there's anything else that can be used like
TRF film. I've heard exposure a slight amount of xylene fumes might
'melt' the toner enough to close the pinholes. Not sure if I want to
go that far. I'm going to test it with different color toners next to
see if that changes anything.

"fenrir_co" <fenrir@...> writes:
> since I etch brass sheet and not PCBs

Could you elaborate on this a bit?  I'm thinking of etching my own
solder paste stensils for my next project.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> "fenrir_co" <fenrir@...> writes:
> > since I etch brass sheet and not PCBs
> 
> Could you elaborate on this a bit?  I'm thinking of etching my own
> solder paste stensils for my next project.
>

I etch through brass sheet (hobby stores carry 4" x 10" sheets) in
.005" and .010" thickness. I've done .016" and .032" but it takes WAY
too long and there's massive amount of undercutting.

Usually I only transfer to one side and spray paint the other side
with oil based (not acrylic/latex) paint from a can (specifically,
Rust Oleun's cheaper 'Painter's Touch'). Red makes a good contrast
against the brass to see how well the etching is going. I suspend the
brass sheet face down in a tray of etchant using a sheet of acrylic
with 'feet' and slide-in runners made of more acrylic superglued onto
it so I don't have to do any taping or such to hold it up. With fresh
etchant the .005" takes about an hour, hour and a half, double the
time then take a little off for the thicker ones. Once it's done I use
a little bit of acetone which makes the paint bubble, let it dry just
a little and you can lift it right off.

Don't spraypaint until 2 days before you plan on etching. Earlier than
that and the paint won't be dry underneath. Longer than a few weeks,
the paint will be difficult to remove.

(deleted/reposted on the group page to correct the brass sheet size.
Forgot the zero)

Thanks for the info.  How accurate can you etch?  The board I'm
working on has 0.5mm (20 mil) pitch parts, so I'd need something like
10 mil holes with 10 mil brass between them, about 40-65 mil long.
This would be in the 5 mil thick brass, I think.

If you use lacquer based paint it will cure in 24 hrs or less and you can
take it or enamels off with lacquer thinner, will not affect the brass.

  -----Original Message-----
  From: Homebrew_PCBs@yahoogroups.com
[mailto:Homebrew_PCBs@yahoogroups.com]On Behalf Of fenrir_co
  Sent: Monday, January 29, 2007 11:14 PM
  To: Homebrew_PCBs@yahoogroups.com
  Subject: [Homebrew_PCBs] brass etching [was Re: New paper to test: Xerox
Waterproof]


  --- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
  >
  >
  > "fenrir_co" <fenrir@...> writes:
  > > since I etch brass sheet and not PCBs
  >
  > Could you elaborate on this a bit? I'm thinking of etching my own
  > solder paste stensils for my next project.
  >

  I etch through brass sheet (hobby stores carry 4" x 1" sheets) in
  .005" and .010" thickness. I've done .016" and .032" but it takes WAY
  too long and there's massive amount of undercutting.

  Usually I only transfer to one side and spray paint the other side
  with oil based (not acrylic/latex) paint from a can (specifically,
  Rust Oleun's cheaper 'Painter's Touch'). Red makes a good contrast
  against the brass to see how well the etching is going. I suspend the
  brass sheet face down in a tray of etchant using a sheet of acrylic
  with 'feet' and slide-in runners made of more acrylic superglued onto
  it so I don't have to do any taping or such to hold it up. With fresh
  etchant the .005" takes about an hour, hour and a half, double the
  time then take a little off for the thicker ones. Once it's done I use
  a little bit of acetone which makes the paint bubble, let it dry just
  a little and you can lift it right off.

  Don't spraypaint until 2 days before you plan on etching. Earlier than
  that and the paint won't be dry underneath. Longer than a few weeks,
  the paint will be difficult to remove.



  


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Thanks for the info.  How accurate can you etch?  The board I'm
> working on has 0.5mm (20 mil) pitch parts, so I'd need something like
> 10 mil holes with 10 mil brass between them, about 40-65 mil long.
> This would be in the 5 mil thick brass, I think.
>

I've never tested the accuracy but it has more to do with the toner
transfer process than the etching process. Which is still hit and miss
for me. I'm about ready to go back to P'n'P Blue again rather than
keep experimenting, though the Xerox Waterproof seems to work well
with -some- printers. I tried it in an Office Depot Xerox copier and
1) the copier couldn't feed the thin sheets properly, I lost half the
stack when it tried to feed eight at once, and the toner doesn't
transfer as well as the Xerox Docucolor 12 that Staples has. I was
hoping people would test various home printers that they already own.

 I checked out Pulsar quite awhile back and immediately canceled the
order when they wanted to charge $14 shipping on the 20 sheet pack of
transfer paper which shouldn't cost more than $2 to ship.

--- In Homebrew_PCBs@yahoogroups.com, "Russ Blakeman" <rhb57@...> wrote:
>
> If you use lacquer based paint it will cure in 24 hrs or less and
you can
> take it or enamels off with lacquer thinner, will not affect the brass.
> 

Lacquer thinner is far far more toxic than acetone or mineral spirits
which can take the oil based paints off.

Forgot to mention that the best finish is to neutralize the etchant
with baking soda and water after rinsing in plain water (going
straight to the baking soda from the etch tank will wear it out very
quickly) and then cleaning the brass with isopropyl alcohol (I can't
find denatured near me that isn't thinned with MEK)

"fenrir_co" <fenrir@...> writes:
> I've never tested the accuracy but it has more to do with the toner
> transfer process than the etching process.

Ok, I can do down to 7 mil with TT.

> 1) the copier couldn't feed the thin sheets properly,

Hmmm... you can feed the brass right through the printer?  That would
save some hassle.

>  I checked out Pulsar quite awhile back and immediately canceled the
> order when they wanted to charge $14 shipping on the 20 sheet pack of
> transfer paper which shouldn't cost more than $2 to ship.

You can get Pulsar stuff through Digikey and Mouser too, so just add
it to your next order and share the shipping.  They list other vendors
too.

Regarding shipping costs...

My most recent Digikey order cost US$56 for the item and US$131 for 
delivery! Caveat emptor!

Regards,

Ross McKenzie
ValuSoft
Melbourne Australia


DJ Delorie wrote:

>
>
> > I checked out Pulsar quite awhile back and immediately canceled the
> > order when they wanted to charge $14 shipping on the 20 sheet pack of
> > transfer paper which shouldn't cost more than $2 to ship.
>
> You can get Pulsar stuff through Digikey and Mouser too, so just add
> it to your next order and share the shipping. They list other vendors
> too.
>
>

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

> > 1) the copier couldn't feed the thin sheets properly,
> Hmmm... you can feed the brass right through the printer?  That would
> save some hassle.

No, I meant the Xerox waterproof paper that I've been experimenting with.

The brass is thin enough to run through the printer but I'm very wary
of using my new R220 because it's a discontinued model. I bought one
spare, but since I use the printers for heavy duty printing (using
refill kits) and the new Epsons can't be refilled (easily, anyway), I
don't want to break it...

You really have to watch the undercutting on the brass. Leaving it in
the etchant too long will definitely have a bad effect on the accuracy.

Stephen wrote:
    I use 0.005" thick Brass Shim from a Non Ferrous Metal supplier who 
had a end of roll at a good price 300mm wide by about 5 meters long I 
think. To etch patterns thru it I
1 Clean it completly within an hour of using it closer the better 
otherwise the self oxidation of the surface reprotects it from the 
Ferric Chloride or stops the Ink from the Ink Jet printer sticking to 
the Brass (also serves the same as a microetch mentioned in other threads)
2 Feed it thru my Epson C87 taped to a piece of paper as a carrier using 
the standard Durabrite Inks but use a mix of Magenta & Yellow to produce 
a really crappy brown colour this is the most resistant I have found to 
Ferric Chloride
3 Carefully remove it from the paper carrier & using a paint stripping 
grade hot air gun (super hairdryer should work as well but I've not 
tried one) wave the hot air stream over the damp ink surface & I've 
found as it drys/cures it releases a small amount of steam/solvent smoke.
4 Leave for a min to cool down. Coat the back with PCB Lacquer  
(Conformal Coating whatever) dry in an oven at 70 C for 15 mins or so.
5 Check for blemishes & patch with a  Staedtler Perm Lumocolor (318-9) 
if nesc.
6 Warm up some Ferric Chloride to 37 to 40 degrees or so place the item 
ink up in the FeCl in a Glass or Plastic dish & with slow careful 
rocking motion for 10 to 15min tops. I always pull it out at 7 mins, 
10min, 12min etc to check for early punch thrus & to prevent 
undercutting over etching wash off & touch up the done bits with the 
Lumocolor or Parcelmate Texta, if it takes longer than 20mins something 
is wrong (either etchant is old, the brass has self oxidised & isn't 
etching)
7 The ink & Lacquer both move with Acetone (use in a well ventilated area)

    the finest lines I've etched & measured using this method is 6 thou 
(0.006") wide & experience tells me I could get it at least a thou 
thinner but I've not had the need yet

This method is a method I have previously outlined in another post back 
in November & it was developed by adapting info found in the Archives of 
this list plus experience with things like the Conformal coating & the 
texta/Lumocolor from other projects.

I hope this helps as having to plan the painting the back of a piece of 
brass days ahead then having to clean the front again seems like hard 
work. The above method from start to finish takes about hour & a half if 
all the bits are lined up & ovens are warm, critical things are really 
clean dry dust free brass shim before you start, fresh warm FeCl & 
patience because this is the shortest way of I've worked out of doing it 
reliably & this is a list of my "shortcuts".

    Have fun

Regards
Stephen Lane