Etching Aluminium on thin Mylar

[stonyjack]

I have been on a DYI mission for sometime to create my own headphone/small speaker driver. The driver will be planar magnetic and I have all the necessary components, however I do not have the knowledge for etching Aluminium on really thin mylar (6 um). Has anyone got experience with this?

 

[lcsaszar]

Diluted Sodium hydroxyde (NaOH) can be used for etching aluminium. I have a pair of Technics EAH-820 ortodynamic headphones with one side broken, that I tried to repair. My problem is that I could not do photocopying on the aluminium. Perhaps I will try again with a laser printer. Here are some more threads on it:
http://www.diyaudio.com/forums/planars-exotics/143717-how-repair-fine-traces.html
Technics EAH-830
http://www.diyaudio.com/forums/planars-exotics/212395-diy-orthodynamic-drivers-headphones.html
At the end I bought another pair for really cheap, and I am happy with them

 

[Elvee]

Most acid and bases do attack aluminum, including NaOH, but since the developer for photo-lithographic lacquers happens to be similar, it is probably not a good idea to use that one, unless you use a negative resin (xylene developer).

I suggest you post your question on a specialized chemistry forum, they will give you more pertinent answers.
I am pretty sure that you can etch aluminum with acetic, hydrochloric or nitric acid, including mixtures, plus salts like iron sulfate but the devil is in the details: how clean and sharp will it be, how fast, what is the optimum temperature etc.

Unless you are ready to spend hours experimenting, it is probably more sensible to ask the experts directly

 

[lcsaszar]

Agreed. I have experience with the Positiv 20 from Kontakt Chemie, and here the illuminated photoresist can be removed with NaOH. Fortunately that part of the aluminium should be etched, too...

 

[stonyjack]

I have spoken to a few chemists, most of them do not have experience with this but do have theoretical solutions which will require trial and error experiments on the mylar.

 

[Elvee]

You can try to duplicate the recipe of commercials products, when it is published.
This one uses a mixture of phosphoric, nitric and acetic acids with water.

 

[ilardi]

A very safe, photoresist friendly etchant is described at this website. http://www.uic.edu/sph/glakes/harts1/HARTS_library/Semenoff.txt This is an acid based system so it does not attack the photoresist.

I have used this successfully on several projects. You can use standard PCB techniques and get very good results.