Acid Copper Plating issues Q&A

A. Hi Sanjay. You've given us no introduction to your situation. Assuming you are a professional production plater with acid copper plating experience who has suddenly experienced a big drop in plating speed, it's probably polarized anodes.

Luck & Regards,

A. Hello again Sanjay. Your copper sulphate is slightly high, but I doubt that that is the actual problem. As I said last time, my guess is that the problem is polarized anodes (what happens, as I understand it, is that the anodes dissolve too easily, building a highly concentrated syrup of copper sulphate around them which does not easily pass electricity, so even with the voltage turned up, little current flows).

What is your chloride concentration? And please tell us the specification for your anodes. And give us some background are you a hobbyist or in a professional plating shop? Did your shop once plate much faster? Thanks.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. I think you need to give data on composition of acid copper bath. Give also current density used, Cl content. Have you tested hardness of deposit? How pure is your bath with contamination? Lower temperature is better for acid copper as recommended.

A. The last time I heard this problem it was in Miami and it was bullets. A barrel had dumped a load of lead into the tank. In the Hull Cell we did have an additive to handle the excess amount of lead. Lead is only slightly soluble in sulphate, but more so in the presence of current. Get your supplier on the phone and ask him how to handle an excess amount of lead.

A. I have never seen circuit boards plated in an acid copper bath that did not have additives. Does not mean it cannot be done. Temperature should be 70-90 °F. You should have phos-copper anodes, not pure copper anodes.

An additive promotes smooth copper deposits, assists plating in thru holes, assists in trying to obtain 1:1 thickness in the hole to the surface of the board. If you use an additive, the chloride must be present at 70-90 ppm. Don't know if no chlorides in your bath is the problem.

Should be using oil free air agitation. Side to side movement of the plating rack helps. Pulse plating may help, more expensive than standard rectifier.

A. You did not need to add so much sulfuric. You can turn the current down some. Adjust a little at a time. Move your anode around some, away from trees to low spots. If you will calculate the total sulfuric and in proportion add copper sulphate and distilled water, you should come out with approx. 240 g/l copper sulphate and 60 g/l sulfuric. If you do want to try chloride then separate a liter from your revised bath and try 0.08 g/l chloride. Try this first before you add to entire bath. Make sure you have air beneath the object in large bubbles. Use a very small amount of a mild liquid soap. Very small at a time. Try in the 1 liter bath first till you get the results you need. Mainly reduce the current density. Approx. 1/10th amp per S.I..

A. Both previous answers are correct. Lack of Cl will cause treeing in high c.d. area. Keep CuSO4 180-220 g/l and H2SO4 60-75 g/l. Some call it maintaining a ratio of three. Avoid any contamination of Fe, Cr.

A. There is obviously some confusion here and it is likely that decorative acid copper formulations are being mistaken for printed circuit ones. The high metal/low acid variety would generally be used for decorative baths and the low metal/high acid type are used for printed circuit boards. The low metal concentration limits the current density that can be applied to the boards but the high sulfuric acid content certainly makes this blend effective for building a thickness of copper in the holes about equal to that which is plated onto the face of the boards. And, the additives become very critical in the production of fine grained and ductile, low stress deposits.

A. Hi Mirzal. To my limited knowledge there is no practical way (except dilution) to remove them from an acid copper plating solution. Although silver chloride salts are insoluble, it may not be an economically feasible answer.

As a matter of curiosity though, I see that CuCl is insoluble, and that there is a laboratory method to precipitate it from the soluble CuCl2 by adding copper powder and steam, while excluding air, then filtering it out. See, for example, www.inc.bme.hu/en/subjects/genchem/chlorides.pdf

If there is a more practical way to remove chlorides, or if anyone has attempted this "CuCl2 + Cu -> 2CuCl" method, please advise. Thanks.

Regards,

1) BRIGHT ACID COPPER PLATING

2) HIGH THROW ACID COPPER PLATING (MOSTLY USED FOR PCB FOR 1:1 RATIO)

A. There is quite a lot of information on the internet concerning the removal of chloride from acid copper baths.

Although I have never done this, the most common method seems to be the addition of a silver compound, usually silver nitrate, silver sulphate, or silver carbonate. A silver nitrate solution would be the most convenient but the nitrate ion would remain in the bath and I don't know how this would effect the plating. In any case, 3.04 grams of silver would precipitate 1 gram of chloride, in the form of silver chloride, AgCl.

Another method that was mentioned in two references was the use of zinc dust [on eBay or Amazon] in exact amounts. This would reduce some of the copper(II) to copper(I), which would then precipitate some of chloride as cuprous chloride, CuCl.

In any case, the precipitate formed would have to be completely removed by filtration before using the bath. Otherwise, any remaining in the bath would most surely produce roughness on the plated parts. It would be best to treat the solution in a separate treatment tank. In one reference, a 5 micron filter is suggested for the removal of the precipitate.

If it were me, I would first try one or more of these methods on a small portion of the bath, say a liter or so.

A. Silver sulphate works. Other than the expense, this is a reliable method to remove excess chlorides. High chlorides increase stress in the copper deposit.

A. SHARMA,

STAR PROBLEM AFTER NICKEL PLATE, SURFACE OF THE PARTS ARE SMOOTH OR ROUGH,DID YOU CHECK YOUR UNPLATED PART FOR ANY DEFECT.IF SURFACE IS SMOOTH YOU HAVE PITTING PROBLEM AND ROUGH DEPOSIT NICKEL , TOO MANY REASONS.CHECK YOUR CHEMISTRY IN YOUR TANKS.

? Hi Praveen. Please try to send us (mooney@finishing.com) some pics of these defects and more data about what you are doing. There is obviously a lot involved in achieving satisfactory plating, and we know nothing of your situation yet except that you do acid copper and get some sort of dots. Thanks.

Re. how to troubleshoot: The Canning Handbook [on eBay, Amazon, AbeBooks] has chapters on the operation and trouble shooting of the various plating baths, and Larry Durney's "Trouble in Your Tank" is the authority on the topic. Good luck.

Regards,

A. Hi Micha. I would guess that the impeller is nylon, which is not really acid resistant like the other inexpensive plastics polyethylene, polypropylene, and PVC ... or that there is a glued joint which doesn't stand up.

I'm sure you recognize that aquarium pumps are designed for aquariums not for plating solutions. There are many brands of plating filters, all of which will stand up to years of constant immersion, but even the cheapest will cost an order of magnitude more than an aquarium filter. We don't recommend or slam particular brands here (why?), but you might look for something advertised as all PVC or all polypropylene, or with readily available replaceable impellers.

Regards,

A. Hi Shinde. ASTM B489 "Standard Practice for Bend Test for Ductility of Electrodeposited and Autocatalytically Deposited Metal Coatings on Metals" might be useful. And it's possible that ASTM B490 "Standard Practice for Micrometer Bend Test for Ductility of Electrodeposits" could help too.

But if the plating is not done to a spec which mentions its compliance tests, I'm not aware of any "standard" tests that would be demanded. Are you the plater or the buyer? Are the parts small enough, and produced in sufficient volume that destructive testing is not a concern? If so, ad hoc testing is common but depends on the parts. Crushing in a vice, wrapping around a mandrel, and sawing can be combination adhesion & ductility tests. Best of luck.

Regards,

A. Hi Malik. Heavy parts taking "lots of time" is relative. What thickness do you want and what current density are you using for how much time; then we can help you figure out if something sounds wrong. Perhaps the problem is only in your expectation that plating should be achievable in less than reasonable time?

The lighter parts are quite possibly fluttering down through the solution, not contacting the cathode enough, rather than sitting in the bottom of the barrel in contact with the danglers. Try lowering the solution level and/or reducing the barrel rotation speed. Or the small brass parts may have greater surface area and therefore not enough amperage for bright plating.

Luck & Regards,

A. Hi Tirath. Sorry, but the answer is heck no, nowhere even close. Unless there is something quite special about your installation like high pressure impingement of plating solution, you would have to be quite lucky to achieve even 10% of that.

Luck & Regards,

A. Hi Daniel.

I am personally unfamiliar with neutralizing acid copper. In my experience you don't neutralize if there will be subsequent plating, for example nickel plating or tin plating; and if there will not be subsequent plating, it is often best to dip in a proprietary sodium benzotriazole [on eBay or Amazon] anti-tarnish, although proprietary chromate-based anti-tarnishes are occasionally used. Then again those things probably shouldn't be used for kitchen items unless they will be lacquered.

Please introduce yourself and describe what you are plating. Unfortunately, there's rarely a good answer to abstract questions -- the answer is usually "depends whether ..." :-)

Luck & Regards,

A. Hello,
Sorry it took a while to reply, I haven't had a chance to contribute to this site in awhile.
When I worked in the plating business we would experience this same problem periodically. We found that the bottom of our tanks contained dropped parts, anode bags had holes in them, the solution level was higher than the openings of the anode baskets. It's important that the bath filtration is adequate and filters are changed on a regular basis. It could be any one of the things I mentioned. Normally roughness of the deposit or nodules are due to particulate matter in the bath, usually metallic.