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
>
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>