> On Mon, 05 Jan 2004 23:10:50 -0000, dkesterline <desterline@...> wrote:
>
>
>>>it also depends where you do your shopping, if muratic acid (HCl)
>>
>>is easy
>>
>>>to come
>>>by where you are and you can get H2O2 somewhere is most likely the
>>
>>cheapest
>>
>>>method.
>>>
>>
>>Muratic acid is widely used for cleaning masonary (bricks, block, etc)
>>and controlling PH in swimming pools. Most any masonary supply house or
>>pool chemical supplier should be able to sell you some in gallon jugs for
>>less then $5.
>>
>>H2O2 (hydrogen peroxide) should be available though any beauty supply
>>shop, though I'm not sure about the strength you need.
>
>
> I fear it is pretty thinned (no more than 10%)
>
>
>>Very weak peroxide is available in the Pharmacy for disinfectant. It's
>>not very strong, but if the recipie calls for water dilution, it might be
>>made to work.
>>
>>Since this is redily available, someone want to post a recipie? Maybe
>>some "Care and feeding" guidelines about the regeneration proccess?
>>
>
>
>
> The problem with diluted H2O2 (like 2% medical) is that you need a lot
> more. and the price is nearly the same as 35% stuff.
> the huge amount of water will keep your etchant growing.
>
> I bought 1 liter 35% at a chemist's shop for some 3 or 4 eur if i remember
> correct.
>
>
> I use a simplified CuCl process (as i think now - if wrong pease write).
>
> it works the following:
>
> for a start you make a 15% HCl solution (tap water is fine)
>
> Then you put a pcb in it.
>
> then you put H2O2 in it.
> for the first pcb you may need more than usual.
> start slow, you should see discoloration of the copper very quick.
> if you see bubbles forming it is more than enugh, stop adding h2o2.
>
>
>
> After some time the etchant will become green.
> as long as it is a bright green it etches and everything is fine.
> over time it gets darker, and darker, nearly brown.
> then it has stopped etching.
> if you add a few drops H2O2 you see immediately the conversion to bright
> green again.
> Add enough to get the whole amount bright green.
> but mind, stirr or agitate the container you are using.
> a few drops h2o2 can regenerate the whole container, you will see amazing
> effect when stirring.
>
> You will also see that localy near copper surfaces the etchant gets brown.
> if you agitate the brown drifts away and is diluted/regenerated and
> dissapears in the green again.
>
>
>
>
> Well, that pretty much is it. just add H2O2 to keep it bright green.
>
> If you add too much H2O2 the whole thing starts to "boil" at the copper
> surface.
> lots of bubbles and gas, clorine smell, no good at all.
> but if you have good ventilation and need a board in 10 seconds (no joke,
> bowl etching) this is a option.
>
>
> The H2O2 is volatile.
>
> After a etch when the board it out there is no new copper to be converted.
> any H2O2 still present has no where to go and will disappear over (not too
> long) time.
> therefore it is good to add only enough for one etch.
>
>
> While there is still copper left a certain (tiny) amount of H2O2 in the
> etchant
> is good. it immediately regenerates the brown etchant to green (Cu2Cl2 to
> CuCl2 i was told).
> But it can only work as long as Cu2Cl2 is produced. if there is no Cu2Cl2
> is left it is a fully
> regenerated etchant.
>
> So you see the reason for not adding too much. it will only produce oxygen.
>
> The echant stays in regenerated state in storage.
> so the CuCl2 is not lost between etches.
>
> It does also stay in used Cu2Cl2 condition. but air oxygen slowly
> regenerates it.
> If you add a bubbler (air pump) and let it run (hours to days) you can
> actually regenerate
> it only from air oxygen.
>
>
> I don't do that because H2O2 is so cheap, it is faster etching with it, and
> air bubbling adds problems (mist).
>
>
>
> There are two effects i can't fully describe:
>
> a) the "start up" why it works with plain HCl and H2O2 in the beginning.
> (but it really does, you need no day - long preparation)
> there is no CuCl2 present, it must directly convert it from copper, HCl and
> oxygen.
>
>
> b) the "blue" effect.
> Only once until now the etchant suddenly formed a blue soft sludge on the
> copper and
> refused etchnig. adding H2O2 did not help.
> Adding HCl did help, but i also needed some H2O2 again.
>
> I assume all Cl atoms were already used up and it din new HCl to get them.
>
>
> The catch is that the copper is not regenerated out the solution.
> the number of CuCL2 molecules steadily increases.
>
> If one Cu2Cl2 is regenerated 2 CuCl2 are produced.
> the clor needed is taken from the HCl.
> but with the hcl there is hydrogen. the hydrogen is taken by the oxygen
> from the H2O2.
> this leaves you with additional water.
>
> I hope this simple chemistry is correct, it is all i could come up with.
>
> the growth of the etchant is very low in fact, i would say nearly
> insignificant if some
> water vaporizes and some is taken out sticking to the boards.
> the consumption of H2O2 is also very low, only a few drops for a smaller
> board.
>
> the HCl consumption is not more, you will etch quite a few boards before
> the initial 15% are used up.
> you see i had the "blue" effect only once until now...
>
> to the handling:
> it is a strong etchant.
> i have fetched the pcb several times by now with bare hands and in only one
> second
> washed it immediately in water. nothing was to be seen on the hand.
> i strongly recomment not doing that anyways...
> Longer exposure is not tested, and i don't like being test rabbit.
>
> You can not use any metals in the tanks etc., no stainless steel or so.
> only plastic holds up well.
>
> For me this etchant is ideal with toner transfer - as it is as easy and
> fast.
> the toner takes no harm in the etchant.
> photoresist works too.
> Most ohp markers (edding etc) don't work too well.
> the best is the red staedtler ohp pen ink.
> with that you can correct your artwork if the toner transfer left errors.
>
>
>
> Feel free to ask any questions.
>
> Stefan
>
>
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