Homebrew PCBs

Hi there,

I've been having problems with my CuCl etching bath (and to a lesser
degree my FeCl etching bath). When I turn the air pump on, the etchant
starts to foam -- if I have the air valve set above a few percent, it'll
foam over the top of the tank in a few minutes.

Acid molarity was around 2.3M last time I checked, with a specific
gravity of around 1.3.

Does anyone know of a way I could reduce the amount of foam being
produced? Reducing airflow only slows down the process, it doesn't stop
it; the foam seems also seems to be quite resistant to being dispersed
and unusually long-lasting. The foam I get when the FeCl tank is being
aerated too quickly usually disperses inside a minute - this stuff takes
a good half hour to revert to a liquid state.

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

On 16/02/14 16:41, Sam Rod wrote:
> 
> 
> Perhaps you only need more room for the foam? Or reduce the liquid
> content translating into more room for foam. Put another way if your
> etchant is working.... The foam control is a small easily solved
> byproduct. :)

The tank is 1.5 litres, filled with 500ml of etchant, leaving 6-8 inches
of space from the liquid level to the top of the tank. The foam was
overflowing the tank after about ten minutes.

I really don't think 500ml of etchant should produce that much foam!

Aeration is an aquarium air-bubbler hose ("air curtain"), a little like
this one: http://www.ebay.co.uk/itm/181124311130
The difference is, mine has a right-angle connector on the end instead
of a straight fitting.

I checked the chemistry a few minutes ago -- bath parameters are:

  Acid molarity      1.3 Molar
  Specific gravity  ~1.225

I left a board etching earlier this afternoon - after half an hour the
CuCl had taken a fair bit of copper off but seemed to stop etching as it
got towards the end. I ended up dumping the board in the ferric chloride
tank to finish it off.

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

I'm lazy, rather than setup an air bubbler system, each time I etch I 
just chuck in a capful of 35% peroxide and give it a stir. 

Typical 5x5 cm double sided board etches in about 5 minutes, board 
vertical in the "tank", just manually moved back and forth gently.

Have never measured the etchant in any way other than "yep that looks 
about the right shade of green".



Philip Pemberton wrote:

>  
>
>
>
> I left a board etching earlier this afternoon - after half an hour the
> CuCl had taken a fair bit of copper off but seemed to stop etching as it
> got towards the end. I ended up dumping the board in the ferric chloride
> tank to finish it off.
>

On 17/02/14 07:01, Philip Pemberton wrote:
> On 16/02/14 16:41, Sam Rod wrote:
>>
>>
>> Perhaps you only need more room for the foam? Or reduce the liquid
>> content translating into more room for foam. Put another way if your
>> etchant is working.... The foam control is a small easily solved
>> byproduct. :)
>
> The tank is 1.5 litres, filled with 500ml of etchant, leaving 6-8 inches
> of space from the liquid level to the top of the tank. The foam was
> overflowing the tank after about ten minutes.
>
> I really don't think 500ml of etchant should produce that much foam!
>
> Aeration is an aquarium air-bubbler hose ("air curtain"), a little like
> this one: http://www.ebay.co.uk/itm/181124311130
> The difference is, mine has a right-angle connector on the end instead
> of a straight fitting.
>
> I checked the chemistry a few minutes ago -- bath parameters are:
>
>    Acid molarity      1.3 Molar
>    Specific gravity  ~1.225
>
> I left a board etching earlier this afternoon - after half an hour the
> CuCl had taken a fair bit of copper off but seemed to stop etching as it
> got towards the end. I ended up dumping the board in the ferric chloride
> tank to finish it off.

Foaming is usually a sign the liquid viscosity is too high. Long etching times 
are a symptom of that too.

The active ingredient should be diluted 1:1 with water. Add a few percent (like 
half a cup) of hydrochloric acid too.

With a setup similar to yours (but working properly), full etch happens in 
12mins at room temperature.

In article <5300E789.1000908@...>,
   Philip Pemberton <ygroups@...> wrote:
> Does anyone know of a way I could reduce the amount of foam being
> produced?

Nip round to your local Macdonalds and see if you can persuade them to let
you have some Dimethylpolysiloxane. It's an anti-foaming agent that they
are adding to various food products and the oil they fry stuff in.

-- 
Stuart Winsor

On 17/02/14 07:01, Philip Pemberton wrote:
> On 16/02/14 16:41, Sam Rod wrote:
>>
>>
>> Perhaps you only need more room for the foam? Or reduce the liquid
>> content translating into more room for foam. Put another way if your
>> etchant is working.... The foam control is a small easily solved
>> byproduct. :)
>
> The tank is 1.5 litres, filled with 500ml of etchant, leaving 6-8 inches
> of space from the liquid level to the top of the tank. The foam was
> overflowing the tank after about ten minutes.
>
> I really don't think 500ml of etchant should produce that much foam!
>
> Aeration is an aquarium air-bubbler hose ("air curtain"), a little like
> this one: http://www.ebay.co.uk/itm/181124311130
> The difference is, mine has a right-angle connector on the end instead
> of a straight fitting.
>
> I checked the chemistry a few minutes ago -- bath parameters are:
>
>    Acid molarity      1.3 Molar
>    Specific gravity  ~1.225
>
> I left a board etching earlier this afternoon - after half an hour the
> CuCl had taken a fair bit of copper off but seemed to stop etching as it
> got towards the end. I ended up dumping the board in the ferric chloride
> tank to finish it off.

Foaming is usually a sign the liquid viscosity is too high. Long etching times 
are a symptom of that too.

The active ingredient should be diluted 1:1 with water. Add a few percent (like 
half a cup) of hydrochloric acid too. When topping up is need every few months, 
just add more hardware shop hydrochloric acid (it has water in it anyway).

With a setup similar to yours (but working properly), full etch happens in 
12mins at room temperature.

An air-ator that blows thousands of tiny bubbles may cause more of a foaming 
problem than one that blows coarser bubbles. Mine blows coarse ones like this:

<http://www.instructables.com/id/Vertical-Etching-Tank-for-DIY-PCB-etching/>

On 17/02/14 01:15, Russell Shaw wrote:
> Foaming is usually a sign the liquid viscosity is too high. Long etching times 
> are a symptom of that too.

That's interesting - I've never seen viscosity mentioned as a control
parameter for cupric chloride etchant.

> The active ingredient should be diluted 1:1 with water. Add a few percent (like 
> half a cup) of hydrochloric acid too. When topping up is need every few months, 
> just add more hardware shop hydrochloric acid (it has water in it anyway).

Are you suggesting I dilute the etchant I have one-to-one with water?
That sounds like it'd send the specific gravity crashing through the floor.

I'd sooner add peroxide to it, at least that'll oxygenate it while it's
reducing the SG...

> With a setup similar to yours (but working properly), full etch happens in 
> 12mins at room temperature.

I'd consider that more than acceptable seeing as my ferric chloride tank
takes a little over twenty minutes :)

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/

On 17/02/14 13:19, Philip Pemberton wrote:
> On 17/02/14 01:15, Russell Shaw wrote:
>> Foaming is usually a sign the liquid viscosity is too high. Long etching times
>> are a symptom of that too.
>
> That's interesting - I've never seen viscosity mentioned as a control
> parameter for cupric chloride etchant.
>
>> The active ingredient should be diluted 1:1 with water. Add a few percent (like
>> half a cup) of hydrochloric acid too. When topping up is need every few months,
>> just add more hardware shop hydrochloric acid (it has water in it anyway).
>
> Are you suggesting I dilute the etchant I have one-to-one with water?
> That sounds like it'd send the specific gravity crashing through the floor.

If you started with concentrated ferric chloride, it should be diluted 1:1 with 
water. The water gives "room" for the reactants. I'm assuming the ferric 
chloride was bought in liquid form. If it was obtained as dry powder, i'd add 
just enough water to dissolve it, then add another equal amount of water again 
(as a first guess, but maybe more water would be better). Add some HCl acid too.

You could tell how diluted the existing mix already is by comparing the weight 
of your etchant to the weight of concentrated ferric chloride.

> I'd sooner add peroxide to it, at least that'll oxygenate it while it's
> reducing the SG...

That would be ok for the first go. After that, the normal bubble agitation will 
keep the oxygenation good.

>> With a setup similar to yours (but working properly), full etch happens in
>> 12mins at room temperature.
>
> I'd consider that more than acceptable seeing as my ferric chloride tank
> takes a little over twenty minutes :)

If you started with concentrated ferric chloride, it should be diluted 1:1 with
water. The water gives "room" for the reactants. I'm assuming the ferric

On 17/02/14 14:36, James wrote:
>
> On 17/02/14 16:02, Russell Shaw wrote:
>>
>> If you started with concentrated ferric chloride, it should be diluted 1:1 with
>> water. The water gives "room" for the reactants. I'm assuming the ferric
>>
> I think you are talking cross-purposes here.  The poster is having problem with
> Cupric Chloride, not Ferric Chloride.

Maybe i assumed wrong then.

However, i started with 1:1 feric chloride, water, and some HCl, and it 
eventually converted to Cupric Chloride etching. But regardless, adequate water 
dilution is still needed. A syrupy concentrate will be very slow.