The practical limit depends upon the size of your wallet.
Are you sure the vendors didn’t say 0.025 inch? Unless the plating solution is old (contains a lot of phosphate by-product,which slows plating and adversely affects the EN deposit properties), this thickness should be attained from most EN solutions in about 3 hours. If the EN is heat-treated for hardness, this should improve adhesion and reduce residual stress if these are concerns.
The Metal Finishing 2003 Guidebook and Directory chapter on Electroless (Autocatalytic) Plating states that electroless nickel (phosphorus type) thickness “generally ranges from 2.5 to 250 um…Deposits… greater than 625 um are currently and successfully being performed. The latter being typical of repair or salvage applications.”
The main problem with thick EN deposits is cost. The chemistry is expensive, solution maintenance must be frequently performed, and it is usually performed at 190
oF, so there is a lot of heat and DI water required. Plating rate is usually less than 0.0010”/hr.
Electroplated nickel (from nickel sulfamate solution) is used in electroforming (i.e., very thick deposits). The process can run for hours unattended.
See the link in the thread ‘Residual stress on electroless nicekl plating’
thread338-51904 for MacDermid’s info. Atotech is another good supplier who should be able to tell you which of their EN solutions are low stress/suitable for thick deposits.
although their web site is less helpful: Go to ‘GMF Chemistry,’ then ‘Electroless Nickel.’
See also ‘How to measure the residual stress in electroless nickel plating’
thread332-52658
