electroless nickel plating, > 11% by weight phosphorus - challenges?

What are the challenges in plating high-phosphorus electroless nickel, with a phosphorus content of > 11% by weight? My understanding is that this type of electroless nickel is completely amorphous and pit free (and non-magnetic), offering the best corrosion protection. It also minimizes tool wear for diamond turning applications, compared to deposits of lower phosphorus content. Reportedly, it also offers the lowest levels of trace contaminants. Over the 10%-11% P range, there is transition from crystalline/magnetic to amorphous/non-magnetic. So, a > 11% P specification assures consistency. Yet my experience suggests that few job shops (platers) are capable (or even willing) to deposit such nickel. Why is it more difficult to plate > 11% P electroless nickel compared to > 10% P? MacDermid's website (http://www.macindustrialproducts.com/properties.html ) states plating rates of 0.3-0.5 mil/hr for high phos. (10-13% P) compared to 0.6-1.0 mil/hr for mid phos. (5-9% P). Is plating rate the driving economic factor, or are there other factors that make the process difficult to establish and maintain?
I've posted a similar question on www.finishing.com.

Note, the bath used to deposit > 11% P is sometimes called a "disk bath" since this type of electroless nickel is used on memory (hard) disks.
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Hello Grant,
Have you received any useful information in response to your postings?
Thanks, Gerry

Not certain what difficulties lie in the actual plating process for electroless nickel with a phosphorus content > 11% by weight. However, I believe that the higher the phosphorus, the more brittle the plating layer will be ( whether it is baked or not, post plating). Might be very sensitive to flaking if the plated part flexes in-service?
Regards,
Greg .
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by Jerry Du (Jun 18 2004, 03:56 PM )
Grant,
Your understanding on the properties of high phos electroless nickel is correct. In fact high phos electroless nickel has been used for years in the indutry. The largest application for electroless nickel is for memory disk EN layer plating which uses high phos EN (~12%P, by weight). High phos deposit can be plated in a very stable rate and quality. Remember, the requirement for memory disk is much higher than general metal finishing. OMG Fidelity is the largest electroless nickel supplier in the indutry and the sole supplier for memory disk application in the US (www.omgi.com).
It is true that the plating rate of high phos bath (>11%P) is generally slower than mid phos bath (5-19%P). The main reason for the plating rate difference is the difference in their chelate and stablizer package used. It is possible to raise the plating rate to about 0.7 mil/hour, but pushing the rate too far will cause deposit property to change. I hope this will help you to clear some of the question. You can contact me if you need any specific assistance.
JD
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Neutron wrote:
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A question concerning this:
It was stated that there is a switch from crystalline/magnetic to amorphous/non-magnetic. What is the mechanism causing this switch, does it have to do with the change in deposition, or just the change in %P. (Just interested)
Thanks Seth