The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: email@example.com (Bob Wilson)
Subject: Re: Etching: sodium persulfate vs ammonium persulfate??
Date: Mon, 25 Nov 2002 04:57:43 -0000
Organization: Your Organization
X-Newsreader: WinVN 0.99.9 (Released Version) (x86 32bit)
References: <3DD726BE.80ABA796@alphalink.com.au> <3DE003E2.firstname.lastname@example.org> <3DE00F98.DE1AE39A@imit.kth.se>
In article <3DE00F98.DE1AE39A@imit.kth.se>, email@example.com says...
>> Andrew Tweddle wrote:
>> > Terry King wrote:
>> >>Somewhere in the 10 years since I last etched a board,
>> >>Kepro has switched to Sodium Persulphate, with some
>> >>Does anyone know what the tradeoffs are between
>> >>sodium persulfate vs ammonium persulfate?
>> > Smell.
>> > The Ammonium ion in aq soln carrys away the copper very effectively.
>> > Sulphate ion is not as effective as chloride ion at etching copper at
>> > the same temperature. As a trade off for kitchen sink use. ie. using an
>> > elevated temperature to move the reaction rate along and relatively
>> > safe, and non smelly compared to ammonium copper chloride which works
>> > brilliantly but requires fume hoods, it isn't a bad one.
>> From my research, sodium persulfate seems a better choice if you want
>> shelf life. It seems that ammonium persulfate recrystalizes when it
>> cools down, and becomes useless. However, sodium persulfate can be used
>> at room temp or heated, and can even be reused again until it's used up.
>sodium persuphate is also less aggressive to cloths, skin and alike...
Aggressiveness to clothes isn't so much the problem, as making a bloody mess
out of them! Ferric chloride tends to produce insoluable brown hydroxides on
exposure to air. At one point, it seemed that half the clothes I owned had
brown stains on them! Ammonium persulphate does not. All its reaction
products are soluable and stable.
Be aware that one should use a very small amount of mercuric chloride as a
sort-of catalyst when using ammonium persuplhate. Full details are givem in
Clyde Coombs' very well known book "Printed Circuits Handbook", among other
places. Failure to do this results in slow etching times.
Generally ammonuim persuplhate has about half the copper capacity of ferric
chloride, has a greater tendency to undercut, and is rather unstable (it can
decompose very rapidly in the presence of some impurities. Still, it can be
useful if one can accept these rather serious disadvantages.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup