Homebrew PCBs

here in israel, thought we are a very advanced country- it is 
sometimes very hard or impossible to find equipment for certain 
things. so, i want to built the etching tank by myself. can someone 
please explain me exacly how this "spray etcher" works???

thanks a lot,
mumin.

----- Original Message ----- 

From: "mumin55555" <MUMIN55555@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, February 17, 2004 7:35 PM
Subject: [Homebrew_PCBs] its me from the etching tank question again!


> here in israel, thought we are a very advanced country- it is
> sometimes very hard or impossible to find equipment for certain
> things. so, i want to built the etching tank by myself. can someone
> please explain me exacly how this "spray etcher" works???


The etchant is pumped through 'spray bars', tubes with holes drilled in
them. For a small unit you might only need a couple of them. Some
experimentation will be needed to get the pressure and hole size correct.
Spray etching has the advantage of speed - Mega Electronics claims 90 s with
fresh ferric chloride for their spray etcher. It does cost 1600 GBP, though.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

can you give me a picture or be more specified on how to build it???



--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon_heller@h...> wrote:
> 
> ----- Original Message ----- 
> From: "mumin55555" <MUMIN55555@H...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, February 17, 2004 7:35 PM
> Subject: [Homebrew_PCBs] its me from the etching tank question 
again!
> 
> 
> > here in israel, thought we are a very advanced country- it is
> > sometimes very hard or impossible to find equipment for certain
> > things. so, i want to built the etching tank by myself. can 
someone
> > please explain me exacly how this "spray etcher" works???
> 
> 
> The etchant is pumped through 'spray bars', tubes with holes 
drilled in
> them. For a small unit you might only need a couple of them. Some
> experimentation will be needed to get the pressure and hole size 
correct.
> Spray etching has the advantage of speed - Mega Electronics claims 
90 s with
> fresh ferric chloride for their spray etcher. It does cost 1600 
GBP, though.

> 
> Leon
> --
> Leon Heller, G1HSM
> Email: aqzf13@d...
> My low-cost Philips LPC210x ARM development system:
> http://www.geocities.com/leon_heller/lpc2104.html

You use bigger tank to etch multiple PCB's. You best bet is to go 
to a shop that sells lots of various plastic containers, and 
choose something there. Make sure it has a lid because you don't 
want evaporation or for stuff accidentally falling in the tank. 
Ferric chloride is cheap when buying in bulk. The difficult part 
is making PCB holders and the air bubble system. You will need to 
feed a hair hose into the tank so the lib can remain on when 
etching, Otherwise the bubbles create splashes outside the tank.


Adam

mumin55555 wrote:

> here in israel, thought we are a very advanced country- it is 
> sometimes very hard or impossible to find equipment for certain 
> things. so, i want to built the etching tank by myself. can someone 
> please explain me exacly how this "spray etcher" works???
> 
> thanks a lot,
> mumin.
> 
>

----- Original Message ----- 

From: "mumin55555" <MUMIN55555@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 18, 2004 4:31 AM
Subject: [Homebrew_PCBs] Re: its me from the etching tank question again!


> can you give me a picture or be more specified on how to build it???

The way I would make it is as follows: a tank containing a relatively small
amount of etchant in the base, with a heater, and a tube connected to a
peristaltic pump delivering the etchant to the spray bars.



Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

You are not going to get near the needed pressure/volume from a peristaltic
pump to use spray nozzles. (unless it's HUGE)

Most commercial units use magnetic drive centerfucial pumps. The closest
your going find on the cheap end is a submersible (saltwater style) aquarium
pump. And that may or may not be compatible with your etchant. The ones that
have high pressure, use a ceramic shaft.

You can get 100%  plastic spray nozzles, that screw right on to threaded
PVC "T"s, Usually used for small decorative fountains.

A 300Watt submersible aquarium heater (again saltwater safe all
plastic/glass) will get a few gallons of etchant up to temp fairly quickly.



----- Original Message ----- 
From: "Leon Heller" <leon_heller@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, February 18, 2004 4:02 AM
Subject: Re: [Homebrew_PCBs] Re: its me from the etching tank question
again!


>
> ----- Original Message ----- 
> From: "mumin55555" <MUMIN55555@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Wednesday, February 18, 2004 4:31 AM
> Subject: [Homebrew_PCBs] Re: its me from the etching tank question again!
>
>
> > can you give me a picture or be more specified on how to build it???
>
> The way I would make it is as follows: a tank containing a relatively
small

> amount of etchant in the base, with a heater, and a tube connected to a
> peristaltic pump delivering the etchant to the spray bars.
>
>
>
> Leon
> --
> Leon Heller, G1HSM
> Email: aqzf13@...
> My low-cost Philips LPC210x ARM development system:
> http://www.geocities.com/leon_heller/lpc2104.html
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>

On Wed, 18 Feb 2004 08:46:02 -0500, Jeremy Taylor <jt@...> wrote:

> You are not going to get near the needed pressure/volume from a 
> peristaltic
> pump to use spray nozzles. (unless it's HUGE)


we've had all this before.
i too do not think it is the ideal choice.

>
> Most commercial units use magnetic drive centerfucial pumps. The closest
> your going find on the cheap end is a submersible (saltwater style) 
> aquarium
> pump. And that may or may not be compatible with your etchant. The ones 
> that
> have high pressure, use a ceramic shaft.

must be a mighty big aquarium pump (for big fishes i guess).
but then there is seaworld and such stuff - they have big fish...

>
> You can get 100%  plastic spray nozzles, that screw right on to threaded
> PVC "T"s, Usually used for small decorative fountains.
>
> A 300Watt submersible aquarium heater (again saltwater safe all
> plastic/glass) will get a few gallons of etchant up to temp fairly 
> quickly.
>
>


Look at the rotrary spray etchers from bungard and similar.

it is nothing but a vertical pipe with holes in the side and a motor on 
the top.
the etchant sprayed out of the holes creates the suction which lifts
the etchant from the bottom. centrifugal force and so on.
maybe you need a "propeller like wheel" in the bottom end.
(for additional pressure and startup).
the motor on the top is nothing special, needs not to be sealed.
maybe you want to add a ceramic bearing on the bottom end for stability.
(you need some rpm). the pictures i have seen for the bigger sprayers
use a motor looking like a off-the-shelf ac motor.
(to give you an idea of the speed).
the small units use thinner pipes and brushed dc motors (and more rpm i 
think).


I believe if you really want to go with a spray etcher (which i wouldn't 
do)
then you might very well make a array of such roatating tubes on each side 
of the
pcb and it will work fine.

I still have no idea how much "a lot of pcbs in big numbers" is.

You also have to rething twice if you will use ferric cloride.
i think this depends on availability and the local laws (what you do with 
it when it is spent).
if you have a hard time disposing of it then you might consider the 
sulphuric acid / h2o2 thing.
there you can get out the copper by cooling (you get copper sulphate which 
you can use for
other funny stuff like electroplating). you wouldn't need to dispose of 
this etchant often.


ST

Stefan Trethan wrote:

> On Wed, 18 Feb 2004 08:46:02 -0500, Jeremy Taylor <jt@...> wrote:
> 
> 
>>You are not going to get near the needed pressure/volume from a 
>>peristaltic
>>pump to use spray nozzles. (unless it's HUGE)
> 
> 
> 
> we've had all this before.
> i too do not think it is the ideal choice.
> 

Yes we have, if you search the Homebrew_PCBs archives for subject: "Pump 
for sray etching" (note the misspelled sray) you'll find the pump of choice 
for a home made spray etcher is the Shurflo 2088-343-135, US$69

http://www.appealingtools.com/shurflo-12-volt-3-gpm-on-demand-diaphragm-pump,-model-2088-343-135.html

Chemical compatibility, pressures, flow rates and price have all been 
talked about.