Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, adam Seychell
<adam_seychell@y...> wrote:

Thanks Adam - this is helpful advice. Is there any reason not to use a
plastic picnic cooler? I believe these are PVC.

Grant

> I agree, ferric is the good old "standard" hobby etchant. Its quick
and low fuss 
> to getting started. Simply pour some into and old ice-cream
container, place in 
> the board and agitate or let it sit.
> The cupric chloride etchant will require a special etching tank
permanently 
> setup. However if you do a fair bit of prototyping I definitely
think its worth 
> the effort building one of these tanks or buying one. Its clean
because the 
> etchant stays in the tank, and there is no setup time involved, just
flick the 
> aquarium pump switch and insert the PCB. I found you also need to
make something 
> to hold the PCB while its immersed in the tank. That way not a drop
should spill 
> on the floor or your skin. Unfortunately chemical resistant tank
building is not 
> that easy. There are a number of ways it can be done, but the best
is probably 
> from perspex sheet and various plastic building materials. Glass is
not a good 
> idea as I found that silicon sealant doesn't make a good long term
seal for acid 
> solutions. The silicon goes a little softer than usual and after
several months 
> to a year it eventually gets salt creep between the glass silicon
interface. 
> Once that happens its a run away effect and you will loose the tank
contents.
> The easiest way to to find a plastic fabricator and ask them to make
you a very 
> basic slit tank from 3 mm PVC. The top of the tank should be flanged
outwards 
> for added strength, and also to act as carry handles. They will be
able to make 
> this kind of thing in 15 minutes. My tank cost AUD$40. PVC is a good
choice 
> because its easy to work with and can glued for modifications. Note
that PVC has 
> a 48°C temperature rating, after that is starts to weaken. The good
thing is 
> cupric chloride works so fast you can keep it at room temp.
> 
> The $175 quoted for 1lb of cupric chloride must be an analytical
grade from a 
> lab supplier. For etching you don't need such purity. Read my post
"Subject: 
> Preparation of cupric chloride etchant" from the other day. Its
possible to 
> prepare the etchant from water, HCl and scrap copper metal, all of
wich are very 
> cheap and readily available.
> 
> Acquiring the titration equipment is probably be biggest headache
for the 
> hobbyist0. However once you own this equipment there is no
maintenance costs. 
> Its very basic lab equipment so any lab supplier will sell this kind
of stuff. 
> There should be plenty places around, just look in the local
business directory. 
> Lab suppliers have a tendency not to sell chemicals cheap. Thats ok
because you 
> only need to get the glassware from them (indicator powder if price
is right), 
> and the chemicals come from supermarkets. You could probably get
away with food 
> dyes for the indicator, even turmeric powder is probably accurate
enough. The 
> NaOH standard solution can be made up if you know anyone who has
0.01g accurate 
> scales. An far easier way to prepare standard NaOH will be to make up a 
> saturated solution, measure its temperature and then look up
solubility chart to 
> find the concentration. For example, the solubility of NaOH at 20°C
is 1090 g/L. 
> Pipette 5.0 ml of saturate into exactly 1 liter of deionized water
to get 
> 0.005*1090/40 = 0.136 Molar standard NaOH solution. You have to buy
a pipette 
> and pipette sucker for doing titration anyhow.
> 
> The fumes from cupric chloride ethants are minor as the HCl
concentration is 
> approx 1 Moles/L or 3.6%. It smells a little at room temperature,
but only if 
> you put your nose up close while air is bubbling through the
solution. Just keep 
> the windows in the room open and everything will be fine. Iron tools
have a 
> tendency to rust around HCl fumes.
> 
> Adam
> 
> 
> grantfair2001 wrote:
> > I think there are many reasons that ferric chloride is still used so
> > commonly. It's the "done thing". If you just ask around most advice
> > about making PCB's will be to use FeCl. And it is readily available,
> > as are the persulfates which can also be used to etch.
> > 
> > The CuCl approach has several advantages - it is cheap, after the
> > initial investment for equipment (and maybe chemicals - the mail order
> > source I found in Canada for CuCL wants $175 for a pound!) and cupric
> > chloride is very environmentally friendly, since you don't have to
> > throw out the solution, just top up the hcl from time to time. But for
> > this you need some lab equipment to do titration, and some bromalin
> > orange indicator. All this is new and different for most amateurs, the
> > chemical equipment is not easy to find in the corner store, and it
> > costs some money when you do track it down. While hcl is readily
> > available from Home Depot or pool supplies, at the concentrations sold
> > (28% here in Toronto) it is much more dangerous than fecl or
> > persulphate. Acid proof gloves and goggles are wise. You need to find
> > an effective way to generate air bubbles evenly to get a reasonably
> > even etch. Think and Tinker (IIRC) outlines a good approach with PVC
> > pipe, but this takes time and tools). To speed etch times, you need
> > heat. To heat the solution requires a quartz covered heater element,
> > again not a home depot item, although available cheaply from surplus
> > sources sometimes. You also need a container to hold the cupric
> > chloride etchant (the original web article suggests using a plastic
> > picnic cooler, which is cheap and easily located) but if you heat the
> > solution I think there can be some hcl fumes which you need to get rid
> > of without acidifying your work environment with fumes. Do you need a
> > fume hood? Where do you find an acid proof fan? Where do you safely
> > vent hcl fumes without corroding neighbors or homes?
> > 
> > I hope to use this approach, but it is not as simple as buying some
> > fecl and adding water in a plastic container. The benefits are worth
> > the costs as far as I am concerned, but IMHO its not quick and easy to
> > get started.
> > 
> > Grant
> > 
> > --- In Homebrew_PCBs@yahoogroups.com, "rolanyang <rolan@h...>"
> > <rolan@h...> wrote:
> > 
> >>I had a chance to play around with some CuCl2 (Cupric Chloride)
> >>etching last Friday and performed a test etch  {snip]
> >>I can't imagine why people are still using Ferric Chloride.
> >>
> >>~Rolan
> > 
> > 
> > 
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