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Etching woes: Press-n-Peel, Laminator, Etch Tank + Sodium Persulphate

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  • phil.quinton@ymail.com
    Hi, First post, hopefully one of many.. To cut a long story short, I m having problems after etching with Sodium Persulphate in my very
    Message 1 of 8 , Feb 19, 2013
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      Hi,<br><br>First post, hopefully one of many..<br><br>To cut a long
      story short, I'm having problems <b>after</b> etching with Sodium
      Persulphate in my very old RS etch tank ( purchased from ebay many years
      ago ). The etch tank has a working agitator which I've been
      using.<br><br>The press-n-peel blue transfer ( Laserjet 4 ) to the 1.6mm
      single sided copper board, via the laminator, appears to be pretty close
      to spot on ( sometimes the lines are a little blurred, which I'm
      guessing is due to too many passes ). <br><br>Issues:<br><blockquote>1.
      Etching is taking a bit longer than I expect ( ~15 minutes ). The very
      first couple of etches I did took < 5 minutes. Since then it's been
      getting progressively worse. Assumption was that the etchant was getting
      worn ( used 5 or 6 times ). So yesterday I cleared out the etchant,
      mixed some fresh 2.5 litres with 500g of etchant and had another go.
      Same, about 15 minutes.<br><br>2. The result looks pretty good ( post
      etch ) with the toner still visible. If you check under a magnifying
      glass you can see all the tracks in tact, nice clear and strong. I clear
      the toner off with a little thinners and the end result is just plain
      awful. A lot of copper tracks are etched straight through, most are very
      thin thin indeed and pads look massacred, even though the toner above it
      looked spot on. In short, it appears to be etching <b>under</b> the
      toner somehow.<br></blockquote><br>My guess is that the etch tank is no
      longer getting to the right temperature ( ~ 45 degrees ) and I'm etching
      too long with the agitator on. I'm going to get myself a temperature
      probe to confirm.<br><br>Has anyone had a similar experience ( Etch
      looking fine until the toner is removed )?<br><br>Thanks in
      advance,<br>Phil.<br>
    • Todd F. Carney
      In the trade what you have what is called undercutting. If the resist in firmly applied, undercutting is usually caused by exhausted etchant and therefore
      Message 2 of 8 , Feb 19, 2013
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        In the trade what you have what is called "undercutting." If the resist in
        firmly applied, undercutting is usually caused by exhausted etchant and
        therefore overlong etch times. It can also occur if too much agitation or
        heat is applied. I don't know about the "tank" you are using, but a simple
        photo tray (or Pyrex backing dish) and a gentle rocking agitation is all
        one needs for one-off PCBs. Etching in a simple apparatus such as this
        makes it easier to monitor the etch process and to stop it once the
        unwanted copper is clear.

        One other thing: do not use 2oz copper clad. Resist on 2oz copper will
        often be undercut before all the unwanted copper is clear. 1oz is plenty
        for every application. There are online tables that show the sectional area
        of a 1oz trace versus temperature and current load. If needed, a trace is
        made wider to handle more current. They're usually designed wide anyway. To
        keep grounds at the same potential, they're almost always made a big as
        possible--at least for analog and RF applications. Here is a nifty online
        calculator for trace width vs. current calculations:
        http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

        Best,

        Todd
        ------------------------------------------------------------------------------------
        K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
        ------------------------------------------------------------------------------------
        QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design


        On Tue, Feb 19, 2013 at 7:27 AM, phil.quinton@... <
        phil.quinton@...> wrote:

        > **
        >
        >
        > Hi,
        >
        > First post, hopefully one of many..
        >
        > To cut a long
        > story short, I'm having problems *after* etching with Sodium
        > Persulphate in my very old RS etch tank ( purchased from ebay many years
        > ago ). The etch tank has a working agitator which I've been
        > using.
        >
        > The press-n-peel blue transfer ( Laserjet 4 ) to the 1.6mm
        > single sided copper board, via the laminator, appears to be pretty close
        > to spot on ( sometimes the lines are a little blurred, which I'm
        > guessing is due to too many passes ).
        >
        > Issues:
        >
        > 1.
        > Etching is taking a bit longer than I expect ( ~15 minutes ). The very
        > first couple of etches I did took < 5 minutes. Since then it's been
        > getting progressively worse. Assumption was that the etchant was getting
        > worn ( used 5 or 6 times ). So yesterday I cleared out the etchant,
        > mixed some fresh 2.5 litres with 500g of etchant and had another go.
        > Same, about 15 minutes.
        >
        > 2. The result looks pretty good ( post
        > etch ) with the toner still visible. If you check under a magnifying
        > glass you can see all the tracks in tact, nice clear and strong. I clear
        > the toner off with a little thinners and the end result is just plain
        > awful. A lot of copper tracks are etched straight through, most are very
        > thin thin indeed and pads look massacred, even though the toner above it
        > looked spot on. In short, it appears to be etching *under* the
        > toner somehow.
        >
        >
        > My guess is that the etch tank is no
        > longer getting to the right temperature ( ~ 45 degrees ) and I'm etching
        > too long with the agitator on. I'm going to get myself a temperature
        > probe to confirm.
        >
        > Has anyone had a similar experience ( Etch
        > looking fine until the toner is removed )?
        >
        > Thanks in
        > advance,
        > Phil.
        >
        >
        >
        >


        [Non-text portions of this message have been removed]
      • tda7000
        I have used the toner transfer method with the laminator described here: http://ultrakeet.com.au/write-ups/superfuser I have not used Press-n-peel blue, just
        Message 3 of 8 , Feb 19, 2013
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          I have used the toner transfer method with the laminator described here: http://ultrakeet.com.au/write-ups/superfuser

          I have not used Press-n-peel blue, just magazine paper. However I have not had undercutting (that I ever noticed!). I used old Ferric Chloride and later on the Hydrochloric acid and Hydrogen Peroxide mixture. Both worked great.

          http://ultrakeet.com.au/write-ups/etchantComparison he describes Ammonium Persulphate as being much worse than Ferric Chloride. I have never used Ammonium Persulphate.

          I don't know if it's any different to Sodium Persulphate in terms of undercutting, but if his article has any truth behind it I would probably try something else.


          --- In Homebrew_PCBs@yahoogroups.com, "phil.quinton@..." <phil.quinton@...> wrote:
          >
          > Hi,<br><br>First post, hopefully one of many..<br><br>To cut a long
          > story short, I'm having problems <b>after</b> etching with Sodium
          > Persulphate

          <Snip>

          In short, it appears to be etching <b>under</b> the
          > toner somehow.<br></blockquote><br>My guess is that the etch tank is no
          > longer getting to the right temperature ( ~ 45 degrees ) and I'm etching
          > too long with the agitator on. I'm going to get myself a temperature
          > probe to confirm.<br><br>Has anyone had a similar experience ( Etch
          > looking fine until the toner is removed )?<br><br>Thanks in
          > advance,<br>Phil.<br>
          >
        • Todd F. Carney
          Either ammonium persulfate or sodium persulfate is used by commercial pcb manufacturers. They do not use ferric chloride, not for decades. Only hobbyists use
          Message 4 of 8 , Feb 19, 2013
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            Either ammonium persulfate or sodium persulfate is used by commercial pcb
            manufacturers. They do not use ferric chloride, not for decades. Only
            hobbyists use the stuff. I'm using a peroxide-muriatic acid-sodium chloride
            etchant. It's very cheap, and the chemicals are available either in a drug
            store or at places such as Home Depot (for the acid). I use it "one-shot."
            I use just enough to do the board I'm etching and then toss it away. It's
            that cheap. This way, It works the same way--etch times, etc.--every time I
            use it.

            73,

            Todd
            ------------------------------------------------------------------------------------
            K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
            ------------------------------------------------------------------------------------
            QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design


            On Tue, Feb 19, 2013 at 9:12 PM, tda7000 <Tda7000@...> wrote:

            > **
            >
            >
            >
            >
            > I have used the toner transfer method with the laminator described here:
            > http://ultrakeet.com.au/write-ups/superfuser
            >
            > I have not used Press-n-peel blue, just magazine paper. However I have not
            > had undercutting (that I ever noticed!). I used old Ferric Chloride and
            > later on the Hydrochloric acid and Hydrogen Peroxide mixture. Both worked
            > great.
            >
            > http://ultrakeet.com.au/write-ups/etchantComparison he describes Ammonium
            > Persulphate as being much worse than Ferric Chloride. I have never used
            > Ammonium Persulphate.
            >
            > I don't know if it's any different to Sodium Persulphate in terms of
            > undercutting, but if his article has any truth behind it I would probably
            > try something else.
            >
            >
            > --- In Homebrew_PCBs@yahoogroups.com, "phil.quinton@..." wrote:
            > >
            > > Hi,
            >
            > First post, hopefully one of many..
            >
            > To cut a long
            > > story short, I'm having problems *after* etching with Sodium
            > > Persulphate
            >
            >
            >
            > In short, it appears to be etching *under* the
            > > toner somehow.
            >
            > My guess is that the etch tank is no
            > > longer getting to the right temperature ( ~ 45 degrees ) and I'm etching
            > > too long with the agitator on. I'm going to get myself a temperature
            > > probe to confirm.
            >
            > Has anyone had a similar experience ( Etch
            > > looking fine until the toner is removed )?
            >
            > Thanks in
            > > advance,
            > Phil.
            >
            > >
            >
            >
            >


            [Non-text portions of this message have been removed]
          • phil.quinton@ymail.com
            Todd, Thank you for the advice. If you use a tray for etching, how do you keep the temperature up for the sodium persulphate? Or is it just a case of getting
            Message 5 of 8 , Feb 19, 2013
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              Todd,

              Thank you for the advice.

              If you use a tray for etching, how do you keep the temperature up for the sodium persulphate?

              Or is it just a case of getting the water warm before you mix in the etchant?

              It's possible that the agitator is too aggressive, especially as the etch time is taking so long.

              Can there be a difference in the quality of the sodium persulphate? The current batch is from a difference source to the very first etching.

              Thanks again,
              Phil.

              --- In Homebrew_PCBs@yahoogroups.com, "Todd F. Carney" <k7tfc@...> wrote:
              >
              > Either ammonium persulfate or sodium persulfate is used by commercial pcb
              > manufacturers. They do not use ferric chloride, not for decades. Only
              > hobbyists use the stuff. I'm using a peroxide-muriatic acid-sodium chloride
              > etchant. It's very cheap, and the chemicals are available either in a drug
              > store or at places such as Home Depot (for the acid). I use it "one-shot."
              > I use just enough to do the board I'm etching and then toss it away. It's
              > that cheap. This way, It works the same way--etch times, etc.--every time I
              > use it.
              >
              > 73,
              >
              > Todd
              > ------------------------------------------------------------------------------------
              > K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
              > ------------------------------------------------------------------------------------
              > QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
              >
              >
              > On Tue, Feb 19, 2013 at 9:12 PM, tda7000 <Tda7000@...> wrote:
              >
              > > **
              > >
              > >
              > >
              > >
              > > I have used the toner transfer method with the laminator described here:
              > > http://ultrakeet.com.au/write-ups/superfuser
              > >
              > > I have not used Press-n-peel blue, just magazine paper. However I have not
              > > had undercutting (that I ever noticed!). I used old Ferric Chloride and
              > > later on the Hydrochloric acid and Hydrogen Peroxide mixture. Both worked
              > > great.
              > >
              > > http://ultrakeet.com.au/write-ups/etchantComparison he describes Ammonium
              > > Persulphate as being much worse than Ferric Chloride. I have never used
              > > Ammonium Persulphate.
              > >
              > > I don't know if it's any different to Sodium Persulphate in terms of
              > > undercutting, but if his article has any truth behind it I would probably
              > > try something else.
              > >
              > >
              > > --- In Homebrew_PCBs@yahoogroups.com, "phil.quinton@" wrote:
              > > >
              > > > Hi,
              > >
              > > First post, hopefully one of many..
              > >
              > > To cut a long
              > > > story short, I'm having problems *after* etching with Sodium
              > > > Persulphate
              > >
              > >
              > >
              > > In short, it appears to be etching *under* the
              > > > toner somehow.
              > >
              > > My guess is that the etch tank is no
              > > > longer getting to the right temperature ( ~ 45 degrees ) and I'm etching
              > > > too long with the agitator on. I'm going to get myself a temperature
              > > > probe to confirm.
              > >
              > > Has anyone had a similar experience ( Etch
              > > > looking fine until the toner is removed )?
              > >
              > > Thanks in
              > > > advance,
              > > Phil.
              > >
              > > >
              > >
              > >
              > >
              >
              >
              > [Non-text portions of this message have been removed]
              >
            • Todd F. Carney
              Phil, I use an muriatic (hydrochloric) acid and peroxide etchant in a tray. I mix the etchant just before use, and since the combination is *exothermic*, it
              Message 6 of 8 , Feb 20, 2013
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                Phil,

                I use an muriatic (hydrochloric) acid and peroxide etchant in a tray. I mix
                the etchant just before use, and since the combination is *exothermic*, it
                heats itself long enough to get the job done. I have used persulfate
                etchants in trays, but the solution does have to be heated. This can be
                done, as you suggest, by mixing the persulfate into *hot* water. I say hot
                because as persulfate goes into solution, there is an *endothermic*
                reaction--it cools down.

                By the time it's fully dissolved it's still warm enough to etch,
                particularly since it is a fresh solution and etching times will therefore
                be short. If you reuse the etchant, you can always heat it carefully in a
                microwave. It will also help to preheat the tray and pcb in hot tap water
                so they don't draw heat from the etchant.

                I suppose it's possible you got some bad persulfate on your second try. I
                haven't used it for some time now, so I don't know good sources. I suspect,
                though, that MG Chemicals would have good quality material.
                http://www.mgchemicals.com/products/prototyping-and-circuit-repair/prototyping/
                .

                73,

                Todd
                ------------------------------------------------------------------------------------
                K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
                ------------------------------------------------------------------------------------
                QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design


                On Tue, Feb 19, 2013 at 11:22 PM, phil.quinton@... <
                phil.quinton@...> wrote:

                > **
                >
                >
                >
                >
                > Todd,
                >
                > Thank you for the advice.
                >
                > If you use a tray for etching, how do you keep the temperature up for the
                > sodium persulphate?
                >
                > Or is it just a case of getting the water warm before you mix in the
                > etchant?
                >
                > It's possible that the agitator is too aggressive, especially as the etch
                > time is taking so long.
                >
                > Can there be a difference in the quality of the sodium persulphate? The
                > current batch is from a difference source to the very first etching.
                >
                > Thanks again,
                > Phil.
                >
                >
                > --- In Homebrew_PCBs@yahoogroups.com, "Todd F. Carney" wrote:
                > >
                > > Either ammonium persulfate or sodium persulfate is used by commercial pcb
                > > manufacturers. They do not use ferric chloride, not for decades. Only
                > > hobbyists use the stuff. I'm using a peroxide-muriatic acid-sodium
                > chloride
                > > etchant. It's very cheap, and the chemicals are available either in a
                > drug
                > > store or at places such as Home Depot (for the acid). I use it
                > "one-shot."
                > > I use just enough to do the board I'm etching and then toss it away. It's
                > > that cheap. This way, It works the same way--etch times, etc.--every
                > time I
                > > use it.
                > >
                > > 73,
                > >
                > > Todd
                > > ----------------------------------------------------------
                > > K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
                > > ----------------------------------------------------------
                > > QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
                > >
                > >
                > > On Tue, Feb 19, 2013 at 9:12 PM, tda7000 wrote:
                > >
                > > > **
                >
                > > >
                > > >
                > > >
                > > >
                > > > I have used the toner transfer method with the laminator described
                > here:
                > > > http://ultrakeet.com.au/write-ups/superfuser
                > > >
                > > > I have not used Press-n-peel blue, just magazine paper. However I have
                > not
                > > > had undercutting (that I ever noticed!). I used old Ferric Chloride and
                > > > later on the Hydrochloric acid and Hydrogen Peroxide mixture. Both
                > worked
                > > > great.
                > > >
                > > > http://ultrakeet.com.au/write-ups/etchantComparison he describes
                > Ammonium
                > > > Persulphate as being much worse than Ferric Chloride. I have never used
                > > > Ammonium Persulphate.
                > > >
                > > > I don't know if it's any different to Sodium Persulphate in terms of
                > > > undercutting, but if his article has any truth behind it I would
                > probably
                > > > try something else.
                > > >
                > > >
                > > > --- In Homebrew_PCBs@yahoogroups.com, "phil.quinton@" wrote:
                > > > >
                > > > > Hi,
                > > >
                > > > First post, hopefully one of many..
                > > >
                > > > To cut a long
                > > > > story short, I'm having problems *after* etching with Sodium
                > > > > Persulphate
                > > >
                > > >
                > > >
                > > > In short, it appears to be etching *under* the
                >
                > > > > toner somehow.
                > > >
                > > > My guess is that the etch tank is no
                > > > > longer getting to the right temperature ( ~ 45 degrees ) and I'm
                > etching
                > > > > too long with the agitator on. I'm going to get myself a temperature
                > > > > probe to confirm.
                > > >
                > > > Has anyone had a similar experience ( Etch
                > > > > looking fine until the toner is removed )?
                > > >
                > > > Thanks in
                > > > > advance,
                > > > Phil.
                > > >
                > > > >
                > > >
                > > >
                > > >
                > >
                > >
                > > [Non-text portions of this message have been removed]
                > >
                >
                >
                >


                [Non-text portions of this message have been removed]
              • William Whyte
                (excess quoting trimmed by moderator - please trim!) Todd,  What are your ratios, particuly the sodium chloride(salt) ?
                Message 7 of 8 , Feb 20, 2013
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                  (excess quoting trimmed by moderator - please trim!)
                  Todd,  What are your ratios, particuly the sodium chloride(salt) ?
                                                                 Ollie       k0lqk

                  --- On Tue, 2/19/13, Todd F. Carney <k7tfc@...> wrote:

                  From: Todd F. Carney <k7tfc@...>
                  Subject: Re: [Homebrew_PCBs] Re: Etching woes: Press-n-Peel, Laminator, Etch Tank + Sodium Persulphate
                  To: Homebrew_PCBs@yahoogroups.com
                  Date: Tuesday, February 19, 2013, 11:21 PM

                  Either ammonium persulfate or sodium persulfate is used by commercial pcb
                  manufacturers. They do not use ferric chloride, not for decades. Only
                  hobbyists use the stuff. I'm using a peroxide-muriatic acid-sodium chloride
                  etchant. It's very cheap, and the chemicals are available either in a drug
                  store or at places such as Home Depot (for the acid). I use it "one-shot."
                  I use just enough to do the board I'm etching and then toss it away. It's
                  that cheap. This way, It works the same way--etch times, etc.--every time I
                  use it.

                  73,

                  Todd
                  ------------------------------------------------------------------------------------
                  K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
                  ------------------------------------------------------------------------------------
                  QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design

                  (snip excess by moderator - please trim!)
                • Todd F. Carney
                  ... Todd, What are your ratios, particuly the sodium chloride(salt) ? Ollie, I m actually no longer using the salt additive, just the muriatic (hydrochloric)
                  Message 8 of 8 , Feb 20, 2013
                  • 0 Attachment
                    On Wed, Feb 20, 2013 at 4:08 AM, William Whyte <olliewhy@...> wrote:

                    > **
                    >
                    >
                    Todd, What are your ratios, particuly the sodium chloride(salt) ?

                    Ollie,

                    I'm actually no longer using the salt additive, just the muriatic
                    (hydrochloric) acid and peroxide. I wish I could find my link, but I think
                    my original source used salt as a means of getting more chloride ions into
                    depleted etchant without adding more acid. I tried it a few times when I
                    was reusing the etchant and it did seem to shorten long etch times. Now
                    that I use the etchant one-shot---a small amount that is then discarded---I
                    don't need to refresh used etchant.

                    My formula for the one-shot version is the typical 1 part ≈35% muriatic
                    (hydrochloric) to 2 parts 3% hydrogen peroxide (the drug-store variety). I
                    warm it a bit to ≈100°F (38°C), but since I use only about 6oz (170ml) of
                    solution in a tray, it cools down fairly quickly. I use the foam trays that
                    meat comes packaged with.

                    I learned the one-shot method as an industrial photographer. Not reusing
                    film (and paper) developer, but using small amounts one-shot, allowed for
                    precise control that cannot really be had with reuse/replenishment schemes.
                    Precise repeatability is possible with one-shot. It's not with reuse.

                    Much of the need for repeatability, in my mind, is that we DIYers use some
                    pretty dubious methods of applying etchant resist to our boards--toner
                    transfer being the most common, it seems--I use it myself. This means using
                    materials that are not optimum for the purpose and applying them with
                    make-shift methods: cloths irons, etc. Combined with less-than-thorough
                    surface preparation of the copper clad, all this means our resist patterns
                    are fragile and cannot withstand long etch times with repeatable results.
                    It's not just that the resists are probably not-all-that chemically
                    resistant, but that their mechanical bond with the copper is weak and
                    uneven. Flaking of the resist, or undercutting of it in long etch times, is
                    an ongoing problem for many of us. Fast etch times and
                    repeatably-predictable results can minimize these problems. Both point to
                    one-shot etching.

                    Now in my online poking around in the last few days on these issues, I am
                    now persuaded that I need to be much-more careful in the disposal of my
                    etchant--especially since I'm tossing out several ounces at a time for each
                    board. To be perfectly honest, I used to just dump the stuff down the drain
                    with plenty of running water. Bad news! So what I'm going to try is to dump
                    it into a five-gallon bucket filled about 3/4 full of wood shavings. I have
                    a whole bale of the stuff left from when we had hamsters (a rant for
                    another occasion). Saw dust or even shredded paper might work just as well.
                    I'll dump the spent etchant into the bucket, maybe stir the shavings around
                    a bit (maybe not), and then keep the bucket open and outside (not
                    inside!!!) but out of the rain. Before long, each dumping will dry in the
                    bucket, sequestered (oh that word!) in the wood or paper fibers. I guess I
                    should put a warning sign on the bucket. At some point I'll have to
                    double-bag the shavings before tossing them in the land-fill garbage, but
                    as I'm thinking now it might take many years before that will be necessary.
                    It may never be necessary in my lifetime, so I'll have to leave disposal
                    instructions in my will (wink wink).

                    Best,

                    Todd
                    ------------------------------------------------------------------------------------
                    K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
                    ------------------------------------------------------------------------------------
                    QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design


                    [Non-text portions of this message have been removed]
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