Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing 1989-2025
-----
Gold Plating thickness variation
Q. We have done gold plating on a flat copper size of 50 mm * 100 mm sheet. Base material copper; over that nickel of 10 microns; and over that gold top layer of 2.55 microns.
In that coupon when we are checking the coating thickness the variation of coating thickness is up to 1.25 micron. Why this variation is coming?
Manager -Operations - Chennai,Tamil nadu /India
December 28, 2024
Ed. note: This forum is intended to help build camaraderie through sharing of tips, pics, anecdotes, & opinions.
When people withhold their names, those readers who offer theirs may be less likely to engage.
A. Hi Gopi.
Solving the problem can be very difficult, but understanding it will not be 🙂
The gold thickness at any location is directly proportional to the current flowing to that specific location in accord with Faraday's Law. But to put the matter colloquially, "Electricity takes the path of least resistance". Any spot which is nearer to the anodes will get a heavier deposit; and, because edges & corners only have to share the electricity with other areas on their interior side (because there is no metal beyond them), they get higher current and thicker deposits.
It is possible to build non-conductive "shields" that will make the path to those edges & corners longer and reduce the current to them, but it's not dead easy. But just to explain the general idea, picture a large sheet of plastic with a 40 mm x 90 mm window cut into it, and placed halfway between the anodes and your copper sheet; the electricity will be able to get to your copper sheet only by passing through the window, and because the window is smaller than your copper sheet, the electrical path from the anodes to the edges & corners is longer than to the middle of the sheet.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q, A, or Comment on THIS thread -or- Start a NEW Thread