I want to deposit Ni films onto a 'mandrel' substrate and separate them, so that I am left with a free-standing Ni foil.
I have read this overview paper on electroforming:
http://www.nickelinstitute.org/~/Media/Files/TechnicalLiterature/Electroforming_AUniqueMetalFabricationProcess_10084_.pdf
A very interesting process - what I wish to do is plate some Ni foil (with some pattern) on a flat metal disc and separate it. From what I can gather, if I use stainless steel it should be possible to separate the Ni from it? How would I do this? Are there any chemicals I could pre-treat the steel with so it separates without damage?
I believe from wider reading I will be best with a Nickel Sulphamate type bath and can use ordinary UV photo resist for any patterning. Does this sound feasible?
Any advice / recommendations that might help me would be greatly appreciated.
You can certainly plate a nickel foil/sheet on a stainless steel electrode which can be separated without any problem. What thickness do you want? What is the size of the foil (Length x width) that you are aiming at? You can use sulphate bath which is the most used industrial bath. You can use sulphamate bath too. Pretreatment of steel is not a cumbersome process for this type of plating.
You can use nickel sulphate baths with some organic additives for better result. Make sure that mandrel should not be too complex. The simpler the mandrel, it will be easier to take out the foil. You can also try nickel electroless deposition on a mandrel followed by normal electrodeposition to provide strength to the deposit. I guess it will work.
You can deposit the Ni film on stainless steel by maintaining different deposition parameters like pH , temperature, concentration of the solution etc. I want to suggest you, take Ni acetate and phosphate buffer solution. Then use cyclic voltametry technique with the scan rate of 20-50 mV/s between -2 to 0V with different temperatures. I guess it will work. But you have to controlled in proper way. Also you can find any recipe in the literature. Good luck of your work.
We have very good experience with plating Ni on Ni and then releasing the Ni. Before we plate on the first layer we oxidise it a bit in H2O2, then we plate and after plating it is very easy to separate the 2 Ni layers. See Fig 5 in our paper Microelectronic Engineering 102 (2013) 36–39.
Good luck!
For obtaining free standing films, coat organic films like a simple photoresist and the deposit your films over it and then strip the resist using acetone to obtain a free standing film. Simply put, you will need some sacrificial layer kind of arrangement.
You can also deposit in vacuum Ni film onto a cleaved NaCl crystal surface and then dissolve NaCl in water. The free film will float on the water surface. This technic is often used in TEM investigations.
Hi all, thank you soo much for all of your replies - I have not had internet access for a few days so it took a little while for me to reply sorry.
Bankim, I was hoping to make 50 micron foils or thinner - the mandrel would not be complex... it would be flat actually - I want to make flat foils. Max size is likely to be 300x300mm.
From the suggestions above, I presume that I should first try with straight nickel sulphate bath, which makes things simpler :). Some of you have mentioned additions of some organics - what sort of materials do you suggest? I have heard of people using boric acid in the bath with the salt. Any suggestions?
If I want to use a stainless mandrel - should I pre-treat it in any way? I am going to mask a pattern on it with photo resist to mask the areas of the foil where I want holes. When peiople say it should be easy to repove... will it simply peel off?
Ravi, this option is one I considered but, since I want the foils to eventually be patterned with complex 'holes' I dont think it is an option. Also, stripping from between layers takes time and I want this to be a reasonably stift process which doesnt damage the resulting foils :)
Eugeniy, being from a thin film background, I did consider deposition on NaCl and dissolving the NaCl, however this is more expensive and does not allow me to make many foils from one master (mandrel)
Thanks Matthew for your response. Usually nickel deposits with stress and many a times it peels off the cathode during deposition due to stress. Thus addition of boric acid and a suitable organic additives such as SLS (Sodium lauryl Sulphate/long chain fatty amines/quarternary ammonium salts will help you to have a smooth and coherent deposit.
On the other hand electroless deposition followed by electrodeposition may also help you I hope. I am quite excited to know your results if you would like to share with me.
Please read as follows;
SLS (Sodium lauryl sulphate) / long chain fatty amines / quarternary ammonium salts etc.
Hi Bankim, I will keep you updated once I have the opportunity to get started (have other work to finish first, as always)
Another possible method of electroplating:
1) Deposition on any substrate in a vacuum aluminum film.
2) Then produce electrolytic deposition of nickel film over aluminum foil.
3) Then immerse the resulting sandwich in the alkaline solution. Alkali dissolve aluminum sublayer and the free nickel film will float on the surface.
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