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HCD area has low tin thickness


Hi, recently I faced a problem where HCD area plated with low tin thickness compared with LCD. For passive components ( chips resistor) consists of top / side/ bottom termination. Side termination is extremely ( 20 µm) high but top extremely low.
Normally top termination we consider HCD compare with side termination. But problem the tin thickness showed reverse.
I'm doing tin barrel plating in acid bright tin. Will too high or too low additive affect throwing power or cathodic efficiency?
Seek for your advice.

Liu Siu Yang
Plating shop employee - Ipoh, Malaysia


Liu Siu,
As you probably know brighteners not only have an affect on the deposit morphology, but plating thickness distribution as well. This is why the term "levelers" is often used in plating baths. You didn't mention tin metal or acid concentrations, current density? Are they all in range?
Have you performed any hull cells to test the LCD and HCD areas? A plating test in the lab will also verify thickness abnormalities. Make small additions of additive to the hull cell and in the plating test beaker [beakers on eBay or Amazon]. Note the results. I have also seen cases where organic contaminants prevent the additives from doing their job. The answer to your question is yes to both. Too high or too low an additive concentration will affect throwing power. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York


HI, Mark Baker,
Tin : 12 g/l ; Acid: 190 g/l
Thanks for advise.
Additive low or high will affect throwing power.
What kind of additive will affect throwing power? Leveler/wetting agent or brightener? Will the balance of leveler /wetting vs. brightener is important?
Recently the product I detect black spot/stain in tin layer, is this called organic contaminants? I strip off tin layer to observe whether is nickel burn but after tin stripping, the black spot is disappeared.


Liu Siu Yang
Plating shop employee - Malaysia

The balance of wetter/additive/brightener is important, but I doubt it is causing the problems you are having. Have you carbon treated the bath lately? As far as black spots go, your rinsing probably needs to be improved. Tin baths can leave salt residue on parts and are hard to remove. The plating barrel should be lifted out of the water rinse 2 or 3 times to ensure full rinsing. How are those efficiency (or plating thickness tests coming)? How about the hull cell?

Mark Baker
Process Engineer - Syracuse, New York

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