Rick,
Lye (Sodium Hydroxide) solution will etch aluminum very well. The trick is not to make the enchant too strong as the reaction is very exothermic and will run away. Use a very dilute solution and give it some time to work. The reaction evolves hydrogen gas, the bubbles tend to lift the edge of your resist which is another reason to use a dilute solution. Most paints and waxes with resist the NaOH but not most photo resists. I would think toner would work ok. Brush the surface now an then to keep the hydrogen bubbles from blocking the etching. NaOH is nasty stuff, but no worse that other strong bases or acids, protect your eyes your corneas doen't do well with lye eye drops. Strong hot HaOH and Al will emit a mist of hot caustic mist not good on your lungs and use gloves.
Red Devil too their lye off the market years ago, I buy RamRod drain cleaner at Smart and Final, it's a fairly strong NaOH solution. I dilute it to clean aluminum parts coming off the mill prior to anodizing.
NaOH is not on the DEA list I or II precursor chemical list yet so it should be available, though there is not much call for it any more not many folks make their own soap. It's available on line I got some food grade stuff for baking pretzels. Acetone, sulfuric acid and hydrochloric acid are on list II so watch how much you buy at one time.
I saw a nice process for activating plated through holes the other day that uses copper hypophosphite. Looks to be a simple reliable way to activate the holes prior to copper plating. The process starts with Calcium Hypophosphite and Copper Sulfate. Turns out all Hypophosphite salts are List I chemicals, which makes it out of reach for home practitioners.
Craig
--- In Homebrew_PCBs@yahoogroups.com, "Rick Sparber" <rgsparber@...> wrote:
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> Has anyone used lye to etch aluminum through photo resist?
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> As a test, I put a strip of aluminum in lye plus water and after 15 minutes
> the strip was half of its original thickness. So there is no doubt that lye
> can etch VERY deep. But the chemical reaction generated a lot of heat and
> the tape I had on there quickly floated off. Next time I will use more
> water.
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> I did have the lye and aluminum outside while I watched from inside. Nasty
> fumes!
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> Thanks,
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> Rick
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