Beginner looking for advice

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Cat 19 years ago

Hello All,

Please excuse the beginner questions; this is my first attempt at etching a PCB.

I bought some 2oz dbl sided boards, and will be etching them using Sodium Persulphate. I've done the traces using press-n-peal blue. I do not yet have an elaborate set up, and I'm looking for any advice your willing to share.

I've read that I should add 1/2lb Sodium Persulphate crystals to 1 gallon of warm water. The board should be submerged until the copper that is not protected is dissolved. Am I missing anything? Any tips or tricks that would be helpful? will this solution be strong enough? How does one dispose of the remaining etching solution?

Lastly the board is a breakout of sorts, taking a db25 and directing the individual wires to terminal connectors. The board will be exposed to short pulses (1-3 seconds) of 24VDC @ up to 5 amps. The traces are

1/16th of an inch thick and separated by only 1/32th of an inch in many places. This board will not be used for transferring signals, just on or off for short durations. Does this sound ok?

Thanks, Brian

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Hawker 19 years ago

Sounds basically good. Been a while since I have etched a board by hand. I send all mine out these days. But from what I remember.

Keep a heat source on the etchant. I think I used to use a 150W flood lamp. Most folks try to hang the board up and down, not flat and use a bubbler, which can be an aquarium air pump with a bunch of pin holes in the hose to keep the etchant moving.

As for trace and space. In the PCB CAD world we talk in mills or mm so we would not say 1/16th" trace and 1/32" space we would say 62.5mills trace and 32.25 mill space. This BTW is considered huge today. Using

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For continuous 5A and 10c temp rise you can see you need a 54 mill trace but you are intermittent (you didn't give a duty cycle) so less would work. If you got room though design for continuous - say 50 mills.

My guess is 30-50 mill is more than enough. 30 mill space sounds good for hand etching. 10mill trace and space is more "normal" for signals in a low tech area and you can probably get 15-20 mill space to work with a decent home made enchant tank if you need the room.

Based on all that if I were you I would go with 50 mill trace and 20-30 mill space.

On 5/9/2007 8:34 PM, The digits of Cat's hands composed the following:

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J

JeffM 19 years ago

Your use of Usenet

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*-rules+*-a-service-for-*-*-*-*+hide-the-fact-*-*-*-they-are-*-on-Usenet+concerns-*-*-*-*-about-the-Google-interface+what.is.wrong+*-*-*-*-*-*-*-*-*-*-*-*-*-is-now-legendary+*-*-savvy+Google-cannot-muster-*-*-*-*-*-*-*-*-*-*-*-*-*+*-*-policed&strip=1 needs improvement. If you feel *compelled* to ask the same question in MULTIPLE newsgroups, *this* is the prefered technique:

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*-*-*-marked-as-Read-in-ALL-*-groups+Newsgroups.line

Your technique

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is selfish and inefficient.

The last half of this thread explains WHY and fleshes out the (more acceptable) cross-posting paradigm:

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*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-*-*-*+*-frowned-on+*-correcting+*-Followup-To-*+*-*-_perfect_-*-*-*-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+*-polite-*-mention-*-*-*-*-*-*-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+mark-*-*-*-*-all-*-groups+*-*-*-*-two-groups-*-*-aren't-*-different

The last post in that thread hints at why (clueless) Google Groupers are so reviled by the majority of Usenet readers (who use a "newsreader").

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M

Marra 19 years ago

I would have put the board out to a professional company to make. Home made boards are crap.

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J

Joel Kolstad 19 years ago

Homemade boards are crap... SPICE with parasitics added is crap... Windows file-locking semantics are crap...

It seems as though you've boxed yourself into a much more restrictive world than need be -- if that works for you, great... but a lot of other people aren't nearly as self-limiting...

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G

Gunnar Gren 19 years ago

Joel Kolstad skrev:

That's becuse it dosen't know very much.

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