027. Hobbiest has tin plating problems

Letter 027

Hobbyist has tin plating problems

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I'm presently making some little shields out of copper sheet for a printed circuit board and would like to know what I should spec for a finish. I made a box for a power supply before out of 22 GA steel and specified just a straight tin plate. I did this because I wanted to solder the box together. The plating seemed to come back fine and the box assembled well. Since I always find finishing one of the most confusing parts of any project I was hoping that this web site could be a source of information for me on this subject in the future. I have been told that maybe a hot tin plate would be better. What is the difference between hot tin and just tin? Did my steel box have to go thru extra plating steps to be tinned? Was there a better finish I could have used? As you can see I have lots of questions and I would surely like to have a place I could get answers. My next project is using some perforated steel sheet so I will need to plate it too!!!! Any comments or help greatly appreciated. Peter

Peter Chapman

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Tin plating of electronics, and for solderability, can be a specialized field, and is one where my hands-on experience is limited, so I hope that some reader more knowledgeable on this than I will jump in and straighten us both out!

But I understand that there has been some movement in the Far East towards applying tin by hot dipping (into molten tin) as opposed to electroplating, for reduced cost and improved solderability. Another technique, I believe, is reflow--where the tin is electroplated, but then heated to the melting point for grain refinement.

Practically speaking though, electroplated tin is a fine finish, readily available, and I don't know of any job shops that offer hot dipped tin anyway. For onesy-twosy applications, if your tin solders well, I don't think you need additional steps.

Ted Mooney, P.E.
finishing.com
Brick, NJ

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While tin electroplate is fine, electroless tin on copper usually provides sufficient corrosion resistance and solderability at reduced cost to electroplating. Hot dip tin is fine for large quantities. For onesy/twosy parts, hobby quantities of electroless tin solution (1 pt / 1 qt) can be purchased off the shelf from many electronics / project sources. There is an electronics oriented chemical company (photoresists/etchants/tuner cleaner/etc.) out of Canada that produces and markets an electroless tin solution that is available in the US

Jeff Albom
- El Granada, California

Ed. note: That company out of Canada is, we believe, out of business. We think their successor is dalpro.net

Hot dip tinning of very small electronic parts was performed in a captive shop in New Jersey about 10 years ago. And it was a performance requiring skill and grace. The scrap rate was much less than 1/2 of 1%. If done poorly, you could have scrap of 10 to 15% with no problem.

I left email with the shop asking if they take on jobshop work. If they do, I will get back to this letter.

Regards,

Tom Pullizzi
Platronica.com
Falls Township, PA

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