Electroless Copper Plating on Alumina
A discussion started in 1996 but continuing through 2017 . . .(1996)
Q. I am a researcher at the South Bank university Chemical engineering research center, and I would like to know how I can coat alumina, (aluminium oxide), particles with copper via an electroless process.
if however there is another way of coating the alumina with copper I would be interested in hearing it.
Thank you.Fraz Uddin Chishti
South Bank University - London, U.K.
A. You can plate alumina like you do ABS through etching, palladium-tin catalyst etc.
chemical process supplier
! A word of caution: Just as magnesium shavings can burst into flame, or a flour factory explode, aluminum and alumina 'particles' may be far more reactive to finishing processes than you might be led to expect from previous experience with aluminum bar stock or fabricated alumina articles.
I'm concerned about a process 'getting away from you', and I would urge you to limit your tests to very small quantities of particles and solutions until you acquire some experience to verify that unanticipated reactions don't occur when dealing with 'particles' that may have huge surface area to volume ratios.
Ted Mooney, P.E.
Pine Beach, New Jersey
To minimize searching and offer multiple viewpoints, we've combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.
Thinfilm Copper Plating(2004)
Q. Our company is working on micromachined thermal actuators. These devices consists of an aluminum thinfilm (500 nm) deposited on an alumina substrate. The aluminum is patterned by photolithography to make electrical traces that must withstand high currents. Since the Al layer is quite resistive, we would need a thicker copper layer (at least 100 µm) on top of the Al. We believe that copper electroplating is the most efficient way to do this, but we experienced adherence problems. The poor adherence is probably caused by the thin oxide layer on the Al, because this metal is vacuum evaporated and is therefore really clean. We tried to remove the oxide with an acid solution, but it also attacked the Al layer (some traces were completely removed by the acid).
We heard about other solutions, such as nickel chloride salt complexed in a solution of ammonium hydroxide to remove the oxide and strike nickel on the Al prior to standard copper electroplating. A zincate treatment, again prior to standard copper electroplating, is another possible solution. We would like to know if these solutions could work with Al thinfilms and if so, if there are well-known recipes for them. We would also be interested in any other easy ways to coat copper on Al thinfilms. The devices are 6"x6" and we are looking for a low to medium production process.Sebastian Pige
micromachining/engineering - Montreal, Quebec, Canada
A. Immersion copper for aluminum: Ammonia (25%) is slowly added to warm 6 % solution of copper sulphate with constant stirring until precipitate which first forms just dissolves. Then add potassium cyanide until colour disappears and solution is ready to use.
Good luck!Goran Budija
- Zagreb, Croatia
Q. I am a student working on a project that involves plating a palladium activated alumina tube with copper by the electroless plating technique. the copper plating solution I am using consists basically of the following chemicals:
In my project I need to plate the tube with a certain amount of copper so several plating baths are needed. My problem is that right after the consumption of the first plating bath the tube coated with copper oxidizes and further platings are not prevented.
How do I get rid of or reduce the oxidation so that I can carry on plating till I get the amount of copper required plated onto the tube?
Thank you for your help
Manchester University - Manchester, England
A. It might help if you mentioned the thickness you require. Most commonly, if you need a thick layer, and the part isn't too complex geometrically, you would first consider electroless copper followed by electroplated copper.
If, for some reason, you HAVE to use strictly electroless copper, why not replenish the copper, caustic, and reducer instead of making up new baths?
A freshly plated copper is quite active and will oxidize. You could use a benzotriazole coat between electroless platings, but then you would have to reactivate the surface prior to the next plating.
- Tallahassee, Florida
Q. Hi James,
I am also facing the same oxidation problem. I think your suggestion of a benzotriazole coat is very interesting. Could you please give us more detailed information on the solution formulation and also how to reactivate the surface later on?
Your advice will be highly appreciated,
Loughborough University - Loughborough, Leicestsershire
June 7, 2010
A. Dear Joey:
I suggest a 5% H2SO4 solution dip, after rinsing the parts and washing the electroless Cu solution from them.
- Tehran, Iran, Persia
How to copper plate alumina?May 20, 2010
Q. Sir, Does anybody know how I can copper plate alumina ?
hobbyist - Adelaide, SA, Australia
May 20, 2010
A. Hi, cousin Elio. Alumina is aluminum oxide. It is sold as a powder or grit. Do you want to plate this powder, perhaps for use in sintered parts? Or do you want to plate a piece of anodized aluminum (aluminum metal with an engineered alumina coating)? Or do you have alumina deposited onto a silicon chip that you wish to metallize?
Although you have a clear understanding of your situation, we don't have any understanding of it at all. What is your hobby and what kind of parts does it involve? Thanks!
Ted Mooney, P.E.
Pine Beach, New Jersey
June 1, 2010
Q. Hello Ted,
I want to copper plate a 20 mm square piece of pure alumina (I have no sputtering/vacuum equipment). Next I want to convert this to cuprous oxide. I am making my own light sensitive semiconductor material.
consultant - Adelaide, SA, Australia
June 6, 2010
A. You can deposit Cu on alumina by electroless plating. The alumina substrate needs to be sensitized using stannous chloride/HCl and activated using palladium chloride/HCl to make it receptive for plating of copper.
T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)
August 20, 2012
Q. Dear sir/madam,
I am working on my thesis which is related to nanocomposite thin film with copper as a matrix and alumina as a reinforcement; the problem is whatever I study I cannot find a scientific definition about thinfilm. Thank you in advance for your assistance. I am looking forward to receive your reply.
- Mashhad-Khorasan Razavi province, Iran
March 18, 2013
Q. Pin-Holes in Copper Plating of Cu/TiW Thin Film (on Glass Wafer)?
First, Let me introduce myself briefly. I'm Bump Process Engineer in Korea.
Can somebody help me to resolve this issue . . . Please, Please.
Bump Process & Structure :
Glass Wafer -> TiW sputter -> Cu sputter -> Negative PR patterning -> Cu plating(7 um) -> PR strip -> Cu Etch -> TiW Etch -> Back Side Inspection => Appear Pin-Holes and problem issue!!
Did not show a bad picture is a pity.
Reply would be highly appreciated.
Help Me.. SOS
Process Engineer - Pyongtaek City, Kyunggi Province, Korea
A. Hi Chang Soo,
Usually pin-hole problem on wafer plating was due to micro bubble/air trap and can be overcome by either mechanical way (vibrator or shocking system to get rid of trapped bubbles) or chemical way like introduce wetting agent into copper plating bath to reduce solution surface tension to have a better wetting of plating surface.
May 14, 2013
I run a smaller wafer plating tank, and I'm having trouble with my finishes coming out cloudy.
My bath is running at 200 g/L H2SO4, 30 g/L copper 2+ ion (that is, 120 g/L copper sulfate pentahydrate), 50 ppm Cl-, and 23 degrees C. I'm using an additive system made by DOW chemical. I plate on a 1500 Angstrom Cu seed on top of a 250 Angstrom Ta barrier
I'm usually plating very slow - about 0.25 micron/min, because my uniformity target is sigma = <2% of mean thickness and my target thickness is 1.5 micron. I know that low current density contributes to cloudiness, but when I run wafers at increasing total current, they transition straight into a reddish slightly burned finish without going through a mirror-bright zone at all.
I don't have access to a CVS tool to directly measure the amount of brightener in the bath, but I've been making the recommended additions.
- Portland, Oregon, USA
May 24, 2013
A. Hi Dan,
You may run hull cell test (e.g., 2 ampere, 5 min, room temp) to identify bright range with additive adjustment even you can't measure additive directly by CVS.
Additive dosing rate (ml per ampere hour) may vary among different plating equipment, plating bath life, production downtime, etc.
April 25, 2017
Q. I am Dheeraj Varanasi, a student from Hungary. As part of my research work I need to carry out electroless deposition of Copper on Alumina substrate. I follow finishing.com and found it useful at more than one instance. So, I would like to know how much HCl can be used to sensitize and activate the surface of Al2O3 substrate before I deposit Cu. I need thickness in range of nano-micro, so there is no problem of low thickness. Kindly help me.Dheeraj Varanasi
- Miskolc, Hungary
A. Hi cousin Dheeraj. It is my understanding that the HCl is only there as a carrier to maintain pH and make the deposition of the palladium possible. It is the palladium which deposits on the aluminum and acts as the catalyst to start the electroless copper deposition.
But if your interest is in building parts as opposed to developing chemistry, please be aware that these activating solutions are available as proprietary solutions from plating process vendors, and you may get better results from standard sequences of such processes which probably involve tin chloride followed by palladium chloride.
Mallory & Hajdu covers how this activation/catalyzing works in their Electroless Copper chapter. Sorry, I don't know whether alumina works differently than plastics in this activation sequence. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"
April 26, 2017
Q. I need electroless copper coating on surface of Alumina(Al2O3) substrate. Could you provide me the best way to activate the surface of Alumina, that does not involve PdCl Palladium Chloride. Alternate means of chemicals which can activate the surface. Thank you.
I am only asking for alternatives to Palladium as I am student and it is very costly to obtain it.
- Miskolc, Hungary
A. Hi again Dheeraj. I think one alternative is to try to find a vendor of plating-on-plastics process chemistry and see if you can get help. I'm not on top of developments, but I understand that graphite based and organo-metallic metallizing solutions are replacing palladium chloride in some applications. But these processes are the product of years of intense closely-guarded privately funded research, so it would be a matter of buying those proprietary chemicals not trying to find out how to make them. Best of luck.
Pine Beach, New Jersey
Striving to live "Aloha"
April 28, 2017
A. I have been able copper plate a form of Alumina Al2O3 (anodized aluminum articles to be precise), so my experience is limited to that -- but it may prove to be an viable alternative to you.
These are the steps for Anodized sheet of aluminum:
Degrease and clean the surface, sensitize the surface with a standard stannous chloride sensitizer solution (3 grams of stannous chloride, 5 ml of HCl, and enough DI Water to make 1 L of solution).
Rinse the article(don't let it dry) and while is wet apply a standard silver mirroring solution(tollen's reagent, brashear process)
After the Silver layer has been applied I was able to coat it with a strong copper layer using the simple but tested 'galvanic copper backing 'layer for silver mirrors. How it works? Make the recently Silvered alumina come in contact with very fine iron or zinc powdered metal and apply a standard Copper Sulfate solution. By way of galvanic electrical contact (standard electrode potential difference between Silver, Iron/Zinc and Copper electrolyte) will deposit a copper layer on the Silvered Alumina.
A video of such process(coating a recently silvered mirror with copper, the only one I could find on the web:
Another way would be by skipping the Silvering and use a Silver Nitrate Activating solution instead of Palladium chloride.
Very good reading here
- Managua, Nicaragua
November 27, 2017
Q. Hello everyone,
I need help and someone who can provide it to me.
How can I do to deposit copper on aluminum?
I already tried with alumon (zinc-plated) as activator and later HNO3
and also with HF and later with zinc-plated
Aluminum is in integrated circuits.
help me, thank you very much
Microelectronics - Salamanca, Spain
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