Nickel-phosphorous electrolytic plating
A discussion started in 2004 & continuing through 2017(2004)
Q. I work as Quality Engineer in a leadframe manufacturing company. Recently, we are switching an electroless nickel plating (EN plating) to electrolytic nickel phosphorous plating (by using different plating machine of course). We are plating NiP/Ni/Cu where copper is our base material. Our customer is requesting a phosphorous content in NiP layer of 6-9 wt % but when we try to plate, we could not get the wanted P content, although we are using the optimal plating condition recommended by our sole chemistry vendor. Thus, I have several questions which hope can get help from plating expert on the problems I faced.
1) Is NiP/Ni/Cu electrolytic plating process is an common plating configuration in electrolytic industry? To what I am told by my plating engineering guy, this is quite a new plating process.
2) How to determine the phosphorous content in NiP layer? We used EDX analysis to check on the P content. Is there any other alternative analysis method for p content? such as AAS, UV spectrophotometer or ICP?
3) What are the important parameters that need to be controlled during the electrolytic plating process? pH, current density and ...?
Thanks in advance for your valuable help.MY Ho
CQE Engineer - Bayan Lepas, Penang, Malaysia
Electrolytic Ni-P is not commonly used in the USA. I know of two facilities that use it for high build coatings for diamond turning for optical applications. Also, one proprietary supplier has tried to commercialize it for electronic applications like yours. Their installations I believe have primarily been in Europe.
If electrolytic Ni-P is like electroless Ni-P, if you use EDX to analyze for phosphorus, you will get a high result, because phosphorus is concentrated at the surface. UV or ICP methods give better results. The UV method is described in ISO spec 4527. The ICP method is described in ASTM spec 733.
Darell Engelhaupt of NASA in Huntsville has written several papers on this bath and its coating.
It is our sad duty to alert the readers to the passing of Ron Duncan on Dec. 15, 2006. For those who would like to know more about him, a brief obituary opened Update No. 13 of our Metal Finishing Industry Update Podcast.
A. I also know of one application in the USA in the biomedical industry. I'm not at liberty to speak too much about it, but electrolytic nickel-phosphorous has some unique properties. I mention it only to note that sometimes when you think nobody is using a certain plating process, it's not as uncommon as you think.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
A. I believe the copper included in the process tends to lower the P content in the deposit. try lowering the amount of copper, after you have a reliable analytical method. I have used gravimetric methods successfully.
Consultant - Poulsbo, Washington
(Don is co-author of the
book "Plating on Plastics")
August 10, 2013
A. Dear Mr. Ho;
for the P% content change, one easy way is to change the ASD.
September 26, 2012
Q. Does NiP require a Au flash on the surface for corrosion resistance. I know some use PdNi without Au flash and work just as well.TJ Tan, Engineering Manager
Nickel phosphorous is quite corrosion resistant and is used alone in lots of applications, although gold is even more corrosion resistant, of course. I could be mistaken, but I think the usual reason for gold plating of nickel phosphorous is for low contact resistance for very low voltage, very low power, digital circuits where even a little tarnish is a problem.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Ni-Co-P electrodepositionOctober 11, 2017
I tried to make nickel-cobalt-phosphorous coating by electrodeposition but the coatings didn't have enough quality (weak adhesion and cracks high stress). Electroplating bath was 240 g/l H2SO4 + 30 g/l NiCl2 + 40 g/l CoSO4 + 30 g/l H3BO3 + 20 g/l NaH2PO2 and saccharin + SDS as additives. The condition was as following:
i= 5 A/dm2
T= 65 °C
agitation = 250 rpm by 4 cm magnet in 250 CC beaker.
The thickness of coatings= 100 µm
I cannot use another bath (such as sulfamate or chloride bath). Is pulse or reverse pulse electroplating helpful? Please give me some advice. How can I have good coatings?
Student - Tehran, Iran
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