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I'm trying my hand at making my own PCBs. Using the positive photo development method and ammonium persulphate for etching.

Does anyone know how long the etchent can be kept once mixed before it becomes useless? Also, what are the optimum temps for both the developer and ammonium persulphate to function at their best?

Videos online show the etching happening quite quickly and my boards are taking a long time. Wondering if temp is to blame. Doing it in the garage so the etch bath is slightly warmer than body temp[40-50C]. Photo development is cooler than body temp like about 25C.

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    \$\begingroup\$ Just my 2 cents here. From my experience (I have made PCBs with chemicals in the past, as well as milling) I can tell you it's mostly not worth it. BatchPCB and other places make PCBs for pretty cheap, and you get nice soldermask and silkscreen which help tremendously (they can prevent shorts that can waste your time) aside from looking better. Storing and managing chemicals these days can be a hassle. Just my opinion. \$\endgroup\$
    – Gustavo Litovsky
    Commented Feb 18, 2013 at 19:08
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    \$\begingroup\$ from personal experience the persulfate etchant can be kept indefinately and the etching temperature is somewhere around 50C-60C (hot to touch, not slightly warmer) \$\endgroup\$
    – miceuz
    Commented Feb 18, 2013 at 19:51

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Developer: we keep in room temperature.

Etchant (Ammonium persulphate): etching at around 50°C in bubble tank. Fresh batch etches 70µm copper in around 15 minutes. We replace it when etching time goes up to 30min.

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