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Etching Al-Cu PCBs



March 5, 2022

Q. Hi. I'm looking for a good wet chemical solution to produce Al-Cu PCB. For the alkaline stripping process I use NaOH, but after that the aluminum layer was oxidized. Do you know about additives or other solutions for Al-Cu PCBs?

sam azar
hobbyist - turkey
^


March 2022

A. Hi Sam. I'm not sure I understand what you mean by Al-Cu PCB. You mean a circuit board built on an aluminum substrate rather than fiberglass (for better heat conductivity as are used for high power LED circuits)?

If so, NaOH certainly sounds inappropriate as it readily attacks aluminum. Generally people use proprietary strippers -- but if you want to try to formulate your own then http://pcbfab.com/photoresist-stripping looks like a good start.

But if liquids are making it through the dielectric layer between the copper and the aluminum and able to attack the aluminum,I'm having a hard time understanding how the board can work with the aluminum and copper connected ... or are you talking about a one-sided board where the NaOH is only attacking the back of the board. More words please :-)

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


March 6, 2022

Q. Dear ted
Thank you very much for your answer.
I use these boards to produce high power LED circuits.
What kind of proprietary strippers to use?
For more details: To remove the printing ink, I use caustic soda, which oxidizes and glosses the aluminum surface behind the board. Recently, I used plates that had an aluminum protective layer, but this is very expensive. So I decided that what I really needed to do was find a chemical solution (other than caustic soda) to remove the printing ink from the aluminum boards. I cannot use nitrate-containing solutions because they are destructive to the etching machine.
I read the site you mentioned but the chemicals introduced were not economical.
Do you have any other advice?
best regards.

sam azar [returning]
hobbyist - turkey
^


March 2022

A. Hi again. By proprietary I mean purchased from a supplier who has done the research and development and sells a packaged solution. Sorry, I don't know much about that field.

It wasn't me who said proper strippers or additives are expensive, although they probably are. You also had another answer, boards with a protective coating on the bottom, which you say are too expensive also. Professionals use these expensive answers because they work robustly. If hobbyists want to sacrifice robustness to find cheaper approaches which they may be able to get by with, that's perfectly fine ... but if there were cheap but robust solutions that's what people would be using instead of their expensive approaches. Sorry.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^

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