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Copper plating on gravure cylinder

March 13, 2010

dear sir,

copper plating on gravure cylinder.
conc. of CuSO4 : 210 gm/ltr
conc. of H2SO4 : 65 gm/ltr
tank capacity : 1075 ltr

I have to know that what would be
if CuSO4 is too high ?
if CuSO4 is too low?
if H2SO4 is too high?
if H2SO4 is too low?
And how do hardness additives work?

Komal Kumar
- Rudrapur, Uttarakhand, India

March 17, 2010

Dear Komal,

Each microstructural change caused by improper process-parameters will immediately also change your engraving properties, which means shorter life-time of diamonds and bad shaped cells. Many providers in the rotogravure industry offers courses in electroplating for the rotogravure industry, in which I am absolutely sure, won't leave any questions open,...anyhow...some answers to your questions:

Too low in Copper sulphate: Lower efficiency, bad distribution of copper deposition over the whole cylinder, burning on cylinder radius

Too high in Copper sulphate: Roughness, Brittle deposits, Crystallization

Too low Sulphuric Acid: Bad conductivity, low hardness, low ductility

Too high Sulphuric Acid: Higher hardness of deposits, brittle deposits, lower ductility

Additives in use are grain refiners. Hardness can be good adjusted, maintained and controlled over the dosage of these additives via Ah-Dosing.

Dominik Michalek
- Sydney, Australia


March 29, 2010

I'm getting very low copper plating efficiency on the cylinder?
current density is 25 A per dm2 and flowing current is equal to required current. H2SO4 & CuSO4 concentration is ok.
how can I get maximum copper plating efficiency?

Komal Kumar
- Rudrapur, Uttarakhand, India


March 30, 2010

Sir,
Something is not clear. Copper sulfate baths have an efficiency close to 100%. If your efficiency was very low the copper concentration should not be OK but rising. Perhaps you mean speed of deposition. In that case, carefully rise temperature and current and observe results.

Guillermo Marrufo
Monterrey, NL, Mexico


March 31, 2010

Hello Komal,

Copper electrolytes, as mentioned from my mexican colleague, work with almost 100% efficiency.

Some hints:
- If your thickness over the cylinder is uneven, then you might have a problem with the level of amount copper nuggets in your cylinders plating tank. Archived distance between cylinder and copper anode should be around 30-50 mm.
- Do not raise temperature above 32°C since this will cause a higher consumption of you hardness additive
- Check you voltage at working current
- Are you sure you are working with effective 25A/ dm2? If you are not sure, then I recommend a measurement on your rectifier shunt during copper plating. Measure the mV-Signal and re-calculate the real current.
- Are all contacts in order? Check carbon brushes on each side, or in case you have a cylinder plating tank with pinoles, then check the pinoles are not damaged and providing a good current flow.

Regards,

Dominik Michalek
- Sydney


April 3, 2010

thank you Mr. Dominik Michalek for the help.

thickness over the cylinder is even.
the level of amount copper nuggets is maximum in cylinder plating tank.
Archived distance between cylinder and copper anode is around 30-50 mm.
I'm working with 25 A/ dm2.

getting voltage = 6 Volt at working current of every cylinder
should I increase voltage & how much ?

Komal Kumar
- RUDRAPUR, UTTARAKHAND, INDIA


April 14, 2010

Hello Komal,

you are fine with 6 Volts at working current. Higher Voltage will increase temperature of your electrolyte and, if chilling system at your company doesn't work properly, will negatively affect your hardening additive and therefore the microcrystaline structure of the deposited copper. Try to keep your sulfuric acid at an concentration between 62 and 65 g/l. Copper sulfate better on 210-230 g/l.

Greetings,

Dominik Michalek
- Melbourne, Australia


April 29, 2010

Sir,

Last few months I'm observing that when I add sulfuric acid in tank to maintain concentration, next plated cylinder hardness suddenly decreases -- why?

Komal Kumar
- Rudrapur, Uttarakhand, India


April 29, 2010

Probably because of the temperature rise. Sulfuric is very exothermic.

James Watts
- Navarre, Florida

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May 3, 2010

Hello Komal,

the drop of the hardness is, as mentioned by James, caused by the heat generated by adding the sulfuric acid. Obviously, depends on the amount of sulfuric acid which is added.

Regards,
Dominik

Dominik Michalek
- Melbourne, Australia


June 3, 2010

dear sir,

I have a very good electrolyte chilling system for M/C. I operate my M/C 28 degree C. when sulfuric acid is added then hardness suddenly decreases. concentration is maintained daily by adding 1 ltr. H2SO4. daily we face hardness problem. please suggest me.

does H2SO4 react with hardness additive and how?

Komal Kumar
- Rudrapur, Uttarakhand, India


June 14, 2010

Hi Komal
in my previous posts I have already written to you what can cause the hardness drop/increase. Therefore I recommend to you the following:

- Make small additions of sulfuric acid
- Re-adjust your electrolyte temperature from 28 to 30°C
- Re-adjust your dosing amount of hardness additive
- Since it costs you quite lot of money re-doing the cylinders due of low hardness I recommend to you to automate as much as possible you dosings.
- I expect that you use DI-Water with a conductivity of less then 10 microSiemens.

Good Luck

Dominik Michalek
- Melbourne, Australia


July 30, 2010

Thanks Dominik Michalek,

I observed that hardness of the copper plated cylinder increases with decrement of H2SO4 conc.

can any one explain why?
Thanks

Komal Kumar
- Rudrapur, Uttarakhand, India


First of two simultaneous responses -- August 3, 2010

Copper coating can be done on cylinders by thermal spray
The thickness limitation is not there in thermal spray and good results can be achieved.We can under TWAS (twin wire arc spray) coating of copper on cylinders.

Gurmit Singh
- Bareilly, UP, India


Second of two simultaneous responses -- August 4, 2010

Hi Komal,

you have to try to understand the co-relation/function between all your physical and chemical parameters such as

- CD
- Temperature
- Additive dosage, effective amount
- Contamination by drag-ins and/or bad DI-Water quality (if existing)
- Filter system
- Calibration/Make of hardness measurement system
- Area of measurement
......and so on.

I think you should consider of hiring a qualified Electroplater-/Engineer to solve your problems and if required, gives an appropriate introduction in your process. At the end you save more capital as if you have continuing high reject rates (process time, chemicals, nerves, diamond (stylus) breakage etc) caused by bad copper deposits made by lack of control the whole process appropriate (which means also the thickness of substrate and base of substrate during measurement....).

I wish you the Best of Luck, Komal.

Cheers,
Dominik

Dominik Michalek
- Sydney, Australia


May 14, 2011

I'm facing dotting (pinhole) problem on gravure cylinder copper plating. while machine is working 20 ASD.
please give suggestion?
thanks.

Komal Kumar
- India
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