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"Tin Plating Problems"

FAQS & TUTORIAL:
(to help readers better understand the Q&A's)

Tin is conventionally plated either out of an alkaline tin stannate bath or an acid bath (based on tin sulfate, tin fluoborate, or methane sulfonic acid). The alkaline and acid baths each have their own advantages & disadvantages which we can't fully cover here.

But we note that in the acid process the tin ions dissolve in the +2 valence state, whereas in the alkaline process the tin ions must be at the +4 oxidation state for the process to work correctly, and they have a tendency to dissolve to the +2 state (like in the acid baths) which will make the process run wrong.

To get them into the +4 state and keep them there requires careful control of the anodes, including 'filming' them. There is a lot of info on all this stuff on this site, but understanding that there is this specific requirement should help you search the site and follow the dialogs.

Current question:

August 6, 2021

Q. We are facing problem in tin plating process. We are loading 8 copper plates in 1000 ltrs tin bath. First part and last observed dull plating in high current area. We need to solve this issue; please give your inputs.

Ananda babu
- Chennai Tamilnadu India
^


August 2021

A. Hi Ananda. Sorry but I'm not really following this description. Is one plate plated at a time, or are all 8 plates put into the tank before plating? Acid or alkaline plating? A pic to mooney@finishing.com for posting here would sure help :-)

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^


August 12, 2021

A. AFTER YOU RESPOND TO MR. MOONEY'S QUESTIONS, THEN, IF ALKALINE TIN, BE AWARE THAT THE SOLUTION IS EXTREMELY SENSITIVE TO COPPER CONTAMINATION. A SEPARATE TIN "STRIKE" WOULD PAY FOR ITSLEF BY PROLONGING THE MAIN PLATING SOLUTION.

robert probert



Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
probertbanner
^

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Closely related historical postings, oldest first:

2002

Q. I'm from a company in South Africa. Tin plating is one of the new ventures that our company started and needless to say we have a few problems and I wonder if someone could shed some light on some of my questions. We are plating onto copper and brass respectively (with tin). Please try and answer the questions as laboriously as possible.

1. How do other companies get their current onto their strip of metal?
2. The top and bottom of the strip will have a different thickness of tin. Why? We use Titanium baskets, and the strip runs horizontally.
3. Our passifier discolours the strip. Are there other types that we can use?
4. We used copper cyanide in one of the baths, it was suggested to leave it out of the process. Now the plated metal discolours (goes black). Do you suggest putting the copper cyanide back into the equation?
5. Is temperature control very important? Why?
6. The 'whiskers'-issue. How, why, how to get it away?
7. What is the voltage required on what thickness of strip?
8. After plating and a few hours has past the plated metal starts to turn black. Why and how do I prevent this?

I know these questions must be elementary to you, but it will help us a lot if you could answer some of them, without getting too frustrated!

Thank you,

Aletta Renee van der Vyver
- Johannesburg, Gauteng, South Africa
^


2002

A. Aletta,

Sounds like you having a lot of difficulties. Let me try to help you with your questions one by one.

1. Pending the type work you have your choices are to rack plate with rack to connect the work on to, barrel plate using steel media for electrical contact, or get electroless or immersion plating bath. However, electroless/immersion tin baths require very specific conditions to operate and are not widely used and may not get the plating thickness that you want.

2.Your different in plating thickness is caused by top part of your strip is a high current density area compare to the bottom. This means the top part wants to plate faster. Try increasing the distance between the anode basket and your work. This will reduce your thickness difference. A thick copper under plate and lowering your plating current may help in this area also.

3. Can't help here.

4. If you are using copper as a strike to help your adhesion, leave this step in the process.

affil. link
"Soldering in Electronics"
from Abe Books

or

5. Temperature control is important pending on the bath. A high operating temperature will improve your plating rate with baths that are alkaline based. However, acid tin baths do not like too high operating temperature and prefer to be operated at room temperature.

6. There is a lot information published on tin whiskers. A good book on the subject is "Soldering in Electronics" by R.J. Klein Wassink =>

Tin whiskers growth occurs only with pure tin under certain conditions such as long term storage with high humidity. Tin-lead alloys, bright tin, and I think reflowed tin is not prone to whisker growth.

7. The best method to set-up your plating parameters is current and time. Set your current per the surface area of your work. For example, 2.5 to 4.0 amps/dm2. A few trials you can determine a plating rate vs current and time. Note there are other variables that will affect your plating rate such as solution metal concentration, temperature, acid or caustic concentration, bath contamination, and so on. Also note the fast plating rate is not always the best. I seen too many people who use the maximum plus current to get the work out. In the end, they generate poor quality work, rework, and scrap.

8. What you may have is tarnishing of your work. Be sure you have good rinsing and drying after plating. The more rinsing the better.You could try an alcohol dip before drying to remove water on or in the plating surface.

I hope this helps and good luck.

Karl Weyermann
- Lebanon, Kentucky
^


November 19, 2014

affil. link
Tin and Tin-alloy Plating
from Abe Books

or




affil. link
Tin and Solder Plating
from Abe Books

or

A. Hi,

Top and bottom will have different thicknesses. Lowering the Current can improve the variance. Or using shields might help. Cathode part nearer to anode basket tends to get higher thickness. Shielding some part of cathode with non-conductive material will reduce thickness.

Voltage can be calculated using Faraday's Law.

Rinsing your product using deionised water before drying using hot air will reduce discoloration.

DUNCANT STEWART
- Lebanon, Kentucky
^



October 18, 2018

Q. Hi, I'm currently looking for solution to resolve dull or black plating in barrel for tin plating. Can anyone brief or explain the aspect or reason which can contribute to this dull plating or any recommendation to solve this problem

Navaletchumy d/o Vijaya kumaran
- Seremban, Malaysia
^


October 2018

A. Hi Navaletchumy. Please give us a starting point :-)

Are you doing alkaline tin plating or bright acid tin? Could the dullness/blackness be fretting corrosion from prolonged tumbling? Have you done any Hull Cell testing? Do you have any photos to show us what you mean by 'dull or black'. Is this a problem which just occurred for the first time, or does it come and go, or is this a new plating line which has not generated proper parts yet.

Most plating texts will introduce you to troubleshooting the process. "The Canning Handbook" [affil. link to book on Amazon] says dull deposit (in Bright Acid Tin) bath may be due to excess chloride, lack of brightener, temperature too high, sulphuric acid concentration too low, anodes passive, current density too low, metal concentration too high, or suspended solids. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^



Cracks in tin plated surface

May 21, 2019

Q. We have a problem with our tin plated surface. We have cracks in the plating.
We are doing a nickel strike and nickel layer before tin plating (to avoid tin whiskers).
Meanwhile we changed already our cleaning bath, HCl bath, nickel strike and nickel bath. And now we can only change the tin bath anymore to hopefully solve our problem.
Is there a possibility to analyse our liquid to avoid this problem in the future? Tin bath is methanesulfonate bath.

Kristoff De Backer
HTMS - Mechelen Noord, Belgium
^


May 22, 2019

A. Hello Kristoff, you didn't mention if the bath contained organic brightening agents. A high level of organics in MSA tin plating will cause internal stress of the deposit. This is true with both brightened and matte baths.

Mark Baker
Electronic Plating - Winston Salem, North Carolina USA
^


May 27, 2019

Q. We are doing a MSA dip and we have Argophan Brightener T and brightener in the bath too.

Kristoff De Backer
HTMS High Technical Metal Seals - Mechelen Antwerpen ,Belgium
^



October 11, 2019

Q. Hi guys I received water mark and stain issue continuously in my plating process. Anybody help to solve the issue?

vasan srini
- chennai,india
^


October 2019

A. Hi Vasan. I'm sure the readers will be happy to try to help; they invariably are. Give us a paragraph or two of detail and send pics for posting here to mooney@finishing.com. Thanks!

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^



June 17, 2020

Q. We are doing bright acid tin plating process of 3-4 micron on steel and brass components with undercoat of copper 3 micron.
Within a week, tin plating turns dull & black.
Please suggest remedy.

Pankaj N.
- Nagpur Maharashtra
^


June 2020

A. Hi Pankaj. It might be best if you describe the process sequences that you do on steel and brass substrates separately because we quickly get into confusion when they are merged...

For example: why are you copper plating the steel before tin plating, and what copper plating process are you using (cyanide, pyrophosphate, proprietary alkaline)? It sounds like it might be introducing more problems than it prevents :-)

What are these components? Are they highly polished before plating? If not, 3-4 microns strikes me as extremely thin.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^


June 21, 2020

Q. Hello sir,
Thanks for response.

For steel components:
Degreasing in solvent - Rinse - Derusting in dilute hydrochloric acid - Rinse - Bright acid tin plating process consists of sulphuric acid+stannous sulphate+brighteners - Rinse - Dip in hot 1% dilute NaOH sol'n - Hot oven dry.

For brass components all same operations except Derusting (as brass doesn't need Derusting).

Proprietary alkaline copper plating (3-4 micron) as undercoat before tin plating on both brass & steel.
Components are threaded & small. Tin plating of 3-6 microns to be done.
After plating, gauge to be checked as inspection criteria.

Within a week, tin plating turns dull & black.

Please suggest remedy.

Pankaj N. [returning]
- Nagpur Maharashtra
^


June 2020

A. Hi Pankaj. I certainly haven't seen all possible workable processes, but I've never heard of electroplating onto brass without an activating dip in mild acid, and I've never heard of electroplating either steel or brass without alkaline cleaning first. It surprises me that your plating has been exhibiting satisfactory adhesion.

As for the blackness developing in a week however, I would strongly suggest sulfur in the packaging or the environment and especially because the tin plating over the copper is very thin. Thread 5106 is specifically about tin plating turning black and should offer further food for thought.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^


June 22, 2020

A. I routinely plated both acid and alkaline tin on steel and brass and bronze parts at a thickness of 0.0002-0.0004" with good shelf life and no darkening. I think you need a thicker tin plate.

LK

Lyle Kirman
- Cleveland Heights
^


June 26, 2020

A. Just a thought. The tin thickness is very low and tin has a propensity to migrate into the base substrate to form an intermetallic compound if the base is copper or iron/steel. In the case of steel, the intermetallic compound is a grey colour and can be easily seen in tin cans, especially when the can has been opened and left exposed to the air for a day or so. If the contents are acid (say pineapples) you will see a dull grey ring around the meniscus - this is due to the tin being dissolved and exposing the intermetallic compound. I note that this enquiry is from the hooter climes and wonder if the thin layer of tin is diffusing into the base...

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
^


June 26, 2020

A. All of the above two reports PLUS, all tin plating solutions do not "rinse" off, you must go back into a mild cleaner to remove the tin plating solution, then rinse again, then it will not turn black in two weeks.

robert probert



Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
probertbanner
^



May 13, 2021

Q. Good morning,
I have been struggling for some time where steel components are copper plated and then tin plated.
The problem is that we experience random small blotches where the plating does not take on the part. This we obviously ascertain shortly after putting a charge in, we then have to scrutinize each part and ones with the blotching we wipe with steel wool/wire brush and return to tank.
The blotching is random, and small in HCD and LCD.
I can only assume that it would be a problem in the Cu. (oil on surface perhaps?) which may stick to component resulting in the blotching.
How can I regularly clean the surface of the Cu. The pre-cleaning/rinsing is meticulous, however this is my last resort.
Many thanks in advance

Stefanie Schopflin
- JOHANNESBURG/SOUTH AFRICA
^

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