Copper Electroplating part 2 (mixing the solution)

CopperElectroplatingIngredients

In part 1, we covered how to build the plating “tank”.  Now we’ll go through mixing our plating solution, using commonly avilable chemicals.

{snippet chemicalwarning}

We’re going to be using a 1 gallon plastic container, this should give us plenty of room for the boards we’re planning on plating.  The chemical composition for the bath looks like this for ~ 1 gallon (this is based on the Think Tinker Copper Plating Solution):

 

Distilled Water .709 gal 2.683 L
Zep Root Kill (Copper Sulfate Pentahydrate Crystals – CuSo45H2O) 10 oz 283.5 g
Car Battery Acid (35% Sulfuric Acid) .286 gal  1.0826 L
Muratic Acid (35% Hydrochloric Acid – HCl) 0.017 oz   .5 mL
Polyethelene Glycol (PEG)  .04 oz  1.134g

Since battery comes in quart containers, we’ll be making ~.874 gal (32/36.608), so the proportion fo Sulfuric Acid is correct. The revised numbers for 0.874 gal are:

Distilled Water 0.6197 gal 2.345 L
Zep Root Kill (Copper Sulfate Pentahydrate Crystals – CuSo45H2O) 8.74 oz 247.78 g
Car Battery Acid (35% Sulfuric Acid) 0.25 gal 0.9462 L
Muratic Acid (35% Hydrochloric Acid – HCl) 0.015 oz 0.437 mL
Polyethelene Glycol (PEG)  0.035 oz 0.9911 g

PEG – 300mg / L .  1Gal of solution = ~3.78L 300*3.78 = 1.134g PEG

After plating an initial board, we added around 9 grams of PEG to the solution – briging the total to around 10 grams.

Steps to Mix the Solution

NOTE: Mix components in the order presented in a WELL VENTALATED AREA!  Don’t breath in the fumes, wear safety glasses and gloves, protect your skin.

  1. Heat water (perhaps 70 C) – mainly to help the crystals dissolve in step two
  2. Fully disolve Copper Sulfate Pentahydrate Crystals in the water
  3. The water will now be blue – it is a good idea to let it cool before adding in the Sulfuric Acid
  4. Carefully add in the Battery Acid, mix thoroughly
  5. Add in Muratic Acid, mix
  6. Add in PEG, mix thoroughly

 

That’s it, the copper plating solution is mixed!  Now we’re ready to activate the through hole walls and finally start plating some PCB’s – assuming a constant current source is available.

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  • Jammer

    I see you are using PEG 3350 (Laxative) = Molecular Weight: 3350 g/mole =  in your process. In your tabe above is the PEG calling for PEG3350 or a different Molecular Weight?

    • bamos

      The PEG listed in the table was taken from a paper which didn’t list the molecular weight:http://www.electrochem.org/dl/ma/202/pdfs/0414.PDF.

      • None

         have you thought about reverse pulse plating?

        • bamos

          I’ve only read about it.  I’d probably go with a brightener (e.g. Janus Green B) before experimenting with reverse pulse plating.

  • Andrew

    Hi, where do you suggest geting the PEG from. I’m pretty sure i can source all teh other ingrediants easily enough, without too much trouble.

    • bamos

      What’s used on this page was sourced from ebay.  PEG is extremely common in laxatives (easy to find in stores/pharmacies) and has been used successfully by others (I believe Null Space Labs used common laxatives (bought from Rite Aid) in their electroplating bath for a while).

      • Andrew Frazer

        Yes, i have found multiple laxatives that have it in, but theres often other stuff in it as well… Does that not matter?

        I’m giving up on trying to use LPKF’s proconduct system of ceramic paste. Its just hopelessy unreliable.  I intend to build a microprocessor controlled power supply for my etching tank.. Sounds overkill and possibly is, but i want to employ reverse pulsing on it..    Four FETS in an H-Bridge will do the trickery to do the swap over.. I’m wonder if i can use a Switching Supply set up as a constant currnet source, rather than using the FETs in a linear fashion.  

        • bamos

          The additives didn’t seem to make much of a difference for NSL – their results were better than mine.  Here’s the site:http://wiki.032.la/nsl/Through_hole_plating

          Depending on the size boards you’re doing, using the FETs linearly isn’t that bad if your power supply rail is a nice low voltage.  Since you’re already rolling a custom circuit, you might try putting an enable on your H-bridge and using a comparator (with feedback from a current sense resistor) as the input to the enable.  This would allow you to control the polarity of the bridge with the MCU and have the comparator control the current.  This is a simplified version of how stepper motor drivers achieve constant current – might be worth a shot.

          • Andrew Frazer

            KLEAN-PREP

            Each sachet of KLEAN-PREP contains the following active ingredients:
            Polyethylene Glycol 3350 59.000g; Anhydrous Sodium Sulphate 5.685g; Sodium
            Bicarbonate 1.685g; Sodium Chloride 1.465g; Potassium Chloride 0.7425g.I can get this stuff, what do you reckon? 

          • bamos

             Hmm…the additives seem a bit high in that.  I’m not sure where you’re located, but MiraLAX appears to be pretty much pure PEG:http://www.miralax.com/pdf/MiraLAX_ProductLabel.pdf (no inactive ingredients, only one active ingredient).  I would aim for something closer to this.

          • Andrew Frazer

            Yes, thats that i thought.  I’ve found somewhere that will ship me the Miralax online. Its not somethign that our pharmacys don’t stock.. They only have the other stuff.   I still have other jobs to do on this, so hopefully it won’t be a hold up.  Forutantly just one last thing to get which is the Sulphric acid, but that is easy to get.

        • bamos

           It’s also worth mentioning that NSL used an industry standard brightener (Janus Green B) in their plating tank, which helped quite a bit.  It seems to be reasonably available online (in the US).

          • Andrew Frazer

            Does anyone know where you can get it from? ( Janus Green B )

  • Andrew Frazer

    PEG 3550 is easily avaialble as Miralax ( http://www.miralax.com/ ) in the US.  I was not able to buy it locally, however i was able to buy 510g from Biovea.com for about $50, which should last a long time!

    • bamos

       Wow.  Too bad you couldn’t find an ebay source to ship to you (the jar in the picture was only about $8 shipped).

      • Andrew Frazer

        Searched Ebay coud’nt find anything.

    • Andrew Frazer

      Hard to say it but i’m quite excited that some laxatives arrived today!

      • bamos

        haha :) Now you can really “get things moving”!

  • Andrew Frazer

    I was faced with buying either 98% or 10% sulphuric acid.  Not so keen on handing the 98%. When i worked out the ratio, it turns out the the diluted sulphric acid in the mix is actualy 10%.. So it is just a matter of using the total volume of acid and water stated above.   ( its within a few ml )..  Since i’ll be needing 30L of electrolyte, this works just fine..

    I’m just a bit worried about how i’m going to mix the copper sulphate in becuase i will have to mix it with the dilute h2s04

    • bamos

       30L…wow…where’s this being used?

      From a little bit of googling – when boiled sulfuric acid gives of primarily H20 (water – not a big deal) and SO3 (highly corrosive).  The boiling of pure sulfuric acid is > 300 degC, so if you heat a small amount of your solution total volume to around 50C or so, you’ll probably be able to dissolve the copper sulfate easily and then mix this in with the rest of the dilute acid. 

      Just be sure to do it outside and do some research to double check that heating the acid won’t kill you immediately 😉

      • Andrew Frazer

        30L is the volume of my tank.    I’m wanting to be able to plate an A4 sized board.   

    • Andrew Frazer

      FYI.   My receipe worked out like this;

      20l 10% h2S04
      1500 g CuSO4.5H20
      2.6ml 35% Muractic Acid
      6g PEG

      The 10% h2s04 comes in 20L drums, and there is no need to mix down with water, as 10% is the right concentration.. How fortunate was that.     I tryed to mix a small amoutn of CuS04 into the 10% h2S04 and it seemed ok..  no heat or bubbling..  So, in went 1500g into the 20L drum..  I rocked the drum back and forward for a while to help disolve and then just left at room temp for 36 hours or so, and its all dissolved, nicely..      This removes the need to mix acid/water and the 10% is safter to deal with as well.. No need to heat it up either, if you are prepared to wait for a couple of days..  

      • bamos

         very nice – sounds like it was meant to be!

  • Andrew Frazer

    I see you note, that you said, after plating a board, you added another 9g of PEG.. Why did you you do that?    It seems you’ve got a lot more in there than the recipe?

    • bamos

       It seemed like the copper wasn’t being deposited evenly, so I threw some more in (the PEG is a leveling agent).  If doing this over again, I would add anode bags/filters and use a brightener (e.g. Janus Green B).

  • Gnomathibus

    Hi, good job! I would like to reproduce the same thing, but I find that 23% muriatic acid in my country can do it anyway if so what is the right proportion?

    • bamos

      You’ll want to add more of the 23% muriatic acid (and a little less of the distilled water) to keep the same ratio as above. Exact amounts will vary depending on the size container you’re putting everything into (sample calculations are above).

      • Gnomathibus

        bamos thank you for your answer, I just find muriatic acid 33% :), can you help me calculate the correct proportions, the size of my container is 10L and my sulfuric acid is 37%

  • mirrirbiker

    What if I have isopropyl (70 percent) as my leveling agent?

    • bamos

      I hadn’t come across using isopropyl as a leveling agent, but after a quick search, it was mentioned briefly in a patent filed in the 60’s:US3257294.

  • beaka

    I use saccharin (Hermesetas tablets)as a brightener and no HCl in my pth process. A lower current will give finer result too.

    • bamos

      Very nice – talk about easy to source! So I can just dump a packet of sweet ‘n low into the solution (what concentration do you use). It was my understanding that the HCl was more of a leveler than brightening agent? I completely agree with the lower plating currents – I believe the pro’s use reverse pulse polarity plating to achieve the same affect in less time.

      Thanks for the tip!

    • Doddy

      Copper Sulphate, Hydrochloric Acid, Sulphuric Acid I can do easily enough… are you saying that I can exclude the HCL and the PEG, and replace both of these with Hermasetas (Saccharin)… if so, how sweet? (e.g. how many Harmasetas tablets per e.g. litre of H2SO4/CuSO4 solution do you find works well?, also, when you say lower current gives finer results, is there a lower limit to how low to go?, or will an amp or two eventually build up a thick enough layer?). First part is the interesting one for me as I’m ordering the H2SO4, CuSo4 today.

  • Teknerd

    This is a great series of articles. I am thinking about doing this myself but I am concerned about cost. Just to do one plating seems prohibitively expensive if you have to dispose the solution afterwards just to do one board. Can this solution be stored for awhile after use? Approximately how many boards can you do in one bath before you need to replace it?

  • zizo

    can I use Salt instead of Muratic Acid?

  • https://www.facebook.com/pages/All-Parts-Recovery/320187514819387 Amir Allparts

    Wear eye protection. gloves etc . and be gentle!

  • Mayerf

    Hi,
    Thank you for all! I have all the tools except peg3350. I can easily buy locally peg6000
    Can I use it?
    Thank you

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