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Stress in multi-layer plating

If I'm plating several metals one on top of each other, is the stress of the total stack equal to sum of individual stresses? Please guide me to a good reading for stress characteristics of plated films and their behavior. Thank you.

Nishath Yasmeen
Process engineer - Houston, Texas
2004

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I'm not sure that your question really has an answer except within a particular context, Nishath.

One way to answer your question might be to say that "zero stress" electroforms have been made by making small adjustments to the current density each time the internal stress starts going tensile or compressive, making it net out at zero. Another way to answer it is that a adding a second layer of tensilely stressed plating will bend a stress-tab more than the first layer alone did. But a third way to answer would be say if you plated 10 layers of nickel and the stress in the first layer was 6000 psi, the stress in the tenth layer would be about 6000 psi, not 60000 psi.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

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We plate a stack of 3 metals Cu, Ni and Pd. My question is : Is the stress of individual layers additive? Copper is compressive and Ni is tensile so the total stack is pretty Neutral correct? Thanks !

Nishath Yasmeen
Process engineer - Plating - Houston, Texas
2004

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No. The stress is between the deposited layer and its immediate substrate. If you have a tensile deposit, it will try to pull away from the substrate and delaminate; putting a compressive layer on top will only make the compressive deposit "hold onto" its immediate substrate. If you want a stress-free multilayer, you must make sure that all deposits are stress free. All the metals you list can be virtually so plated.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004

Stress is force/Area.The area where plating stress is effectual is the cross section . So the stress in different plating layers won't ad up( the force will add up of course) , if calculated over the whole system. To calculate the stress over the whole layer you have to multiply the single layer thickness with the internal stress in this layer , add the values of all layers and then divide by the overall thickness. But remember it will not be a homogenous system, the different stresses in the different plating layers will still be there .

Marcus Hahn
- Lucerne, Switzerland
2004