I have a new customer who is recommending a Sulfamate Nickel Finish for his boards. I'm not really familiar with this process. Is anybody else? How does it differ from electroless nickel? Can a standard NC solder paste cut the mustard with this stuff? I did a search of the Fine SMTNET Archives on Sulfamate Nickel and pulled up NADA! Won't you please help a worn-out old process engineer who's down on his luck?
Congratulations on your new customer. This could be a keeper.
Here's what you're familiar with: Electroless Nickel - per MIL-C-26074 and ASTM-B733. Electroless nickel describes the plating of nickel deposits, which may contain phosphorus and boron, onto catalytic metallic or catalyzed non-metallic substrates by chemical reduction. Unlike electrolytically plated nickel coatings, electroless nickel coatings produce very uniform, hard and lubricious coatings, without an externally applied electric current, and are normally identified according to their phosphorus content. [Pacific Aerospace & Electronics]
Here's what your new customer is talking about: Electrolytic Nickel - per QQ-N-290. Unlike Electroless Nickel, Electrolytic nickel uses an external current supply to plate the nickel to various substrates. It is one of the most widely used types of plating due to fact it can be welded unlike Electroless Nickel. Electrolytic Nickel comes in different forms, one of the most popular being Sulfamate Nickel. Sulfamate Nickel is has a dull, matt finish and is often used as an undercoating for Gold applications. [Pacific Aerospace & Electronics]
You should be able to go about your business, nary giving this new nickel coating a second thought. [Assuming the fab did a good job of plating, of course.] Your new customer could be practicing one theory making the rounds. The theory protends that the "black pad" problem associated with hypercorroded nickel on ENIG pads goes away with elctrolytic nickel.
Simply calling out electrolytic nickel does not assure you of sulfamate [low stress] nickel. All electrolytic nickel is not sulfamate / stress free. Typically a low stress nickel electroplate is produced with a sulfamate nickel bath and low brightners/organics. Make sure you call it out correctly.