That was very interesting information. You write that it is used for a number of other electronic applications. Do you know if it ever has been used as finish on surfaces to be soldered?

Per-Erik


-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Martin Bayes
Skickat: den 30 maj 2012 08:55
Till: [log in to unmask]
Ämne: Re: [TN] Phosphorus at the BGA pad

As others have already posted, conventional electrolytic nickel gold used as a PWB final finish,  uses a pure nickel underlayer.

It is worth noting that, for a number of other electronic component applications, electrolytic nickel-phosphorus is used commercially, rather than pure electrolytic nickel, due to its higher corrosion resistance.

Such electrolytic nickel-phosphorus baths, typically operated at low bath pH (below 2) and contain hypophosphorous acid.  Co-deposition occurs in an analogous manner to electroless systems (with P-content controlled by variables including bath pH, hypophosphous acid content and current density).

The development of modern day electroless nickel systems was triggered by the serendipitous discovery of electrolytic nickel phosphorus systems by Brenner and Riddell at what was then the National Bureau of Standards (now NIST) in the 1940's ( A. Brenner and G. Riddell, J. Res. N. B. S., (37), 32 (1946).

Martin

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