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Inconsistent & Variable Copper Plating Hardness

   

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Q. We plate hard copper on mild steel cylinders which are later engraved using electronic engravers. The problem is that we can't seem to maintain the hardness of the plated copper consistent. I would like to see a consistent 200 HV plus on the hardness tester but every now and then I see a dip in the hardness, which even goes down to 180 HV. If I try to overdose the electrolyte with the hardness additive the plated copper becomes brittle and then I have to use a carbon filter. The other problem is that the engraving section complains about excess burrs when they cut a coarse angle, so I need to improve the copper quality too.

I would appreciate if someone could suggest a way to overcome the above mentioned problems.

SHEIKH RIZWAN
In of charge Plating Section - KARACHI, SINDH, PAKISTAN

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A. I think no one can recommend anything with the very little information you gave. What chemistry are you using: sulphate, fluoborate, pyrophosphate, cyanide? And what kind of hardness additive are you adding? The only thing that I can guess is the excess of burrs comes from the same low hardness deposit (the cutting chips don't break). Give more details to try to give you an intelligent tip.

Guillermo Marrufo
Monterrey, NL, Mexico

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A. Given what you've said I would assume you're plating cylinders in an acid copper bath. In the sulfuric acid bath, copper plates preferentially, the additive is a controlled impurity. To successfully co-deposit the additive the current density is increased, also the concentration of the copper as copper sulfate must be controlled. If the copper sulfate concentration increases, the additive cannot co-deposit, trying to overcome this by increasing the dosage of additive will leave you with organic contamination, thus brittleness. Control your copper sulfate and sulfuric acid concentrations and you should be able to consistently achieve the hardness you need.

Hank Kudlinski
- Guilford, Connecticut

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March 31, 2009

Q. Plz let us Know What is the International Standard of Copper Hardness for Electronic Engraving.

please let us Know the Optimum Range of Minimum & Maximum.

Umma Reddy
- Rudrapur, Uttarakhand, India

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A. Hi, Umma. Letter 49930 is about that topic and seems to suggest 200 Vickers. letter 38332 suggests 195 to 205 HV. Good luck.

Regards,

Ted Mooney, P.E. RET finishing.com Brick, New Jersey

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April 6, 2010 Q. Why does the hardness suddenly decrease when I add sulfuric acid into the copper plating electrolyte? Komal Kumar - Uttarakhand, India A. Hi, Komal. Letter 54564 and several other threads here suggest that higher sulfuric acid leads to greater, not lesser hardness. However, that letter also suggests that the heat released from adding the sulfuric acid may raise the temperature of the bath, which does cause lower hardness. Good luck. Regards, Ted Mooney, P.E. RET finishing.com Brick, New Jersey January 26, 2011 I must agree with Hank Kudlinski here, if the sulphate and acid levels are not correct then its virtually impossible to control your hardness level. we run a chloride free solution (and as such always use de- I water )with sulphate at 220 g/l and sulphuric 61 g/l, maintaining a hardness of 220V as this suits our higher speed engravers, lower hardness around 190-200 may be more suitable for slower or older heads. hope this helps Garry Williams - Liverpool, England December 29, 2011 Q. I am searching for a way to increase the hardness in a copper pyrophosphate solution. The application is for plating DMM's in the record plating process. I am looking for a hardness between 230-250 KHN. D Bancroft - Garden Grove, California, USA January 5, 2012 I looked in "the properties of electrodeposited metals and alloys" second edition by Safranek. Its KHN is given with a 200g weight and hardness was under 100 for a grain refined copper pyrophosphate deposit. All else was lower. I assume that you are using a proprietary additive. What does that company have to say? If this is a home brew, I doubt if you will get your desired hardness. Modern electroplating by Lowenheim lists the hardest plate as 250 vickers, kg.mm*2 from an Ammonium citrate modified bath. It also lists one as 150 - 210 from a M & T additive, again in vickers. James Watts - Navarre, Florida Dear Reader, please -- Answer or comment on this question (your posting will appear on this page)   Ask a new question (your posting will start a new page)   Visit our home page (finishing.com -- The Home Page of the finishing industry ®)