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Tin plating on Aluminum -- is intermediate layer of copper needed? (page 1)

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Q. I want to plate tin onto aluminum. Can I plate directly onto the aluminum,or is an intermediate coating required? I was planning to degrease, de-ox, and zincate the aluminum prior to plating with tin.

How thick can I plate the tin?

Next, I want to plate tin on a plasma-sprayed tin surface. How do I activate the plasma-sprayed tin to get a good bond?

Thanks,

Wanda Hudson
- Huntsville, Alabama


First of two simultaneous responses--

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A. You will need some type of strike or barrier coating between the Tin and Aluminum if you want good results. As far as a vendor it depends on the type of tin. For Alkaline Tin you can make it up yourself. Thickness can be up as much as .001" or more without any problems, depending on the application.


Jim Conner
- Salisbury, Maryland

Second of two simultaneous responses--

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A. The way I would recommend to plate Sn on Al is to pretreat the Al with the std. process cycle, then immersion Sn the Al. The next step is to either bronze plate the Al or Alkaline Cu plate, then Sn plate in either an Alk. Sn or Acid Sn process.

As for activating the plasma Sn I would recommend an acid that will dissolve some Sn, either MSA, methane sulfonic acid, or fluoboric acid. The conc. to use will be about 5% by vol.


George Shahin
- Rock Hill, South Carolina

June , 2009

A. Hi, folks. It sounds like George is speaking of the Alstan® process as an alternative to zincating.

We don't really like to compare a proprietary process to a generic process like zincate, or to compare one proprietary process to another. But I have seen Alstan lines for bus bar and electrical components, and I suppose that since it is a very purpose-designed process, specifically for applying tin to aluminum, that it may well do that job better than zincating followed by copper plating followed by tin plating.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey


To minimize searching and thrashing time, and to provide multiple points of view, Finishing.com combined several formerly separate threads into the single dialog you are now viewing. Please forgive any resultant repetition.



++++appended

We plate copper bus bar in tin. I wanted to know how we could plate aluminum bus bar in tin. What is the process to do this?

Howard Leatherwood
Plating shop - Pearland, Texas, United States


++++

You cannot electroplate directly onto aluminum because it is so active that it forms a passive skin instantly. The normal procedure is to immersion plate zinc onto the aluminum via a zincating bath, and then proceed with alkaline copper and tin plating, or alkaline electroless nickel and tin plating. As an alternative, Atotech offers a proprietary sequence for plating aluminum busbar called Alstan, which uses stannate instead of zincate, and then direct tin plating without the copper or electroless nickel.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey



Copper strike isn't adhering to aluminum

+

Q. Hi,

I have a tin plating process over copper and brass, but I want to process it over aluminum. I have tried with Canning system (Bondal), with Alumon (Enthone OMI) with gal-1 (Atotech) and when I proceed with the strike copper, the copper surface has air between copper and zinc. Because of that, the tin plating is not good, and if I brush the tin will go and the aluminum part is at air. I think there is a problem with my copper process, because it is used for plating over carbon steel (sheets), and is cyanide and has caustic soda for component, but what can I do or what else can I use for that part of the process.

Thanks a lot for your comments.

Jorge Luis Medina Franco
- Aguascalientes, Ags. Mexico


+

A. On your cyanide copper solution you should be using a "strike" formulation which is high in cyanide and low in copper metal which is the opposite of a plate solution. Also you should have live entry into the cyanide copper solution.


George Shahin
- Rock Hill, South Carolina

+

A. We do a lot of tin on aluminium. What you need is an electroless nickel strike prior to plating with copper although the copper should not be necessary we use a zincate process followed by electroless nickel strike (your local suppliers that you have mentioned would have a suitable process then either straight to the tin or better still a coat of conventional bright nickel). We find this works fine.

Regards

Bob Lynch
     plating company
Sydney, Australia

Wernick, Pinner & Sheasby
Surface Treatment & Finishing of Aluminium and Its Alloys


+

A. The principal and safer method for plating aluminum is to use an intermediate layer of electroless nickel instead of copper. If you have no possibility of electroless plating, you must use the system zincate + copper. It is important to enter the bath "live" and to start with high current density (3 Amp/dm2) and slow it down to 2 Amp/dm2. Remember that each type of aluminum alloy has different pretreatments.

Gabriel Schonwald
Bnei Berak, Israel



Can't get good adhesion on A356 Aluminum

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Q. We are currently electro-Tin plating on aluminum and aluminum alloys. Our methods employ standard alkaline cleaning, alkaline etch, a commercial zincate followed by a low pH copper strike, then tin. We have had very good success with our current chemistry with exception of plating on A356 aluminum alloy. The alloy contains 7% silicates, which I believe is causing our adhesion problems. Typically the zincate process does not seem to hold on. I'm looking to see if anyone has any experience plating on A356 aluminum or experience in activating high silicate alloys.

Tim Martin
plating shop - Springfield, Massachusetts


++

A. (Rinsing omitted):
1. Clean in a non-silicated cleaner STAY OUT OF ALKALI ETCHING! Alkali etching does the opposite of what you want to do. You want to decrease the area of exposed silicon and INCREASE the area of bare aluminum. By alkali etching you are doing the opposite, as the alkali removes aluminum and leaves the silicon.
2. 100% Nitric Acid + 2 pounds per gallon ammonium bifluoride, immerse until the part TURNS FROTHY WHITE ALL OVER, remove, do not stop to look, hurriedly rinse two times and then enter
3. Dilute zincate
4. 4 oz/gal Baking Soda (Sodium Bicarbonate) FORGET THE COPPER CYANIDE
5. ALKALINE ELECTROLESS NICKEL from one of the top three EN suppliers, 90 °F, 5 minutes, the Johnny-come-latelies are not good enough.
6. Do anything you want to it now.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

Editor's note:    
   Mr. Probert is the
   author of




What process for plating on aluminum is best for RF

+++++++appended

Q. I am working on a project where we are solder fusing RF printed circuit boards to copper and aluminum pallets. We intend to plate the copper and aluminum pallets with matte tin. What specification should we be calling out? Is an underplate required between the copper or aluminum pallets and the matte tin and if so what would be best given this is an RF application.

Martin Camen
user - Dix Hills, New York



A. Sorry Martin, I don't know whether having copper between the aluminum and the tin is beneficial to RF reduction or not. But we appended your inquiry to a thread which indicates that you can go with an all tin approach on aluminum, or a copper and then tin approach, or an electroless nickel on the zincate layer before the tin plating. Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey



Bus bar plated with copper then tin turns black over time

June 27, 2010

Q. Aluminium busbar is tin plated using copper as undercoat (3 microns) upon which tin is coated 6 microns. Over a period of time the busbar turns blackish. What could be the reason?

praveen kumar
quality engg - bangalore, karnataka, india



A. Hi Praveen. There are possibly many causes, but the first two that come to mind are cyanide bleed-out from the cyanide copper step, or sulfides forming because of a sulphide rich atmosphere. With some more facts, and hopefully some pictures, we can probably offer a pretty good answer. God luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey



Required thickness of copper layer between aluminum and tin

February 10, 2014

Q. We are doing tin plating on aluminum, in this process we are giving the copper plating barrier for adhesion and also for conductivity purpose. Please tell me what should be the thickness of copper plating before tin plating?

Arjun singh
- Haridwar, uttrakhand, India
  ^- Privately contact this inquirer -^


February 11, 2014

A. Hello Arjun,
If the Cu plating is also for conductivity purposes, I would deposit a minimum of .0008" or 8/10ths of one mil. Good Luck!

Mark Baker
Process Engineer - Malone, New York USA


February 12, 2014

Q. Which type of copper plating do the good work to achieve the high thickness among Cyanide alkaline and acid copper for tin plating on aluminum purpose.
If we consider general case for undercoat layer, how much it should be.

Arjun singh [returning]
- Haridwar, uttrakhand, india


February 13, 2014

A. Hello Arjun,
I'm not a big fan of Cyanide baths, so if you have a non-cyanide alkaline Cu bath, use it as a strike, then go into the acid Cu plate to build thickness. Acid Cu has better leveling characteristics than Cyanide Cu and Pyrophosphate Cu baths. If you didn't need the Cu plate for finished part conductive purposes, you could skip the acid Cu plate.From what you stated in your question it sounds like you do need that step.

Mark Baker
process engineer - Malone, New York


February 24, 2014

Q. We are doing Tin plating on aluminum busbars for corrosion and conducting purpose. In this process we are doing Alkaline cleaning, Non-cyanide alzincate, Copper plating, and finally tin plating.
In the above process copper plating is 5-7 micron and Tin plating 8-9 micron. Finish is good & OK, Adhesion is OK.

Can we continue this process?

Arjun singh
- Haridwar, uttrakhand, india


February 2014

A. Hi Arjun. If there are no specifications which your process is not compliant with, I think it sounds good :-)

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey


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