Immersion Silver

We have one product with electroless nickel, immersion silver solderability protection. We do not purport to be experts, but like many things, have seemingly boundless opinions.

Side note: There are a least three different [maybe five] imm silver finishes that have little in common, aside name and confusion.

LONG-TERM STORAGE OF IMM SILVER Not sure what you consider to be long-term storage, but we believe shelf life to be somewhat less [on the order of 12 months] than HASL and much better than ENIG, given adequate environment (20 to 30 C, 40 to 70% R.H.), remain in a sealed package to eliminate air born contamination, bla bla bla.

HANDLING PRIOR TO PLACEMENT/ASSEMBLY * PWB coated with imm silver must be completely dried prior to packaging and all packaging materials must be sulfur-free. * PWB handling is not as sensitive as it is for the OSP finishes. Some people say it is a good practice to wear gloves to prevent potential soiling of the solder pads with human oils and salts. [This is true. It is good practice to handle boards with gloves, especially if you are NC.] We do not wear gloves when handling imm silver [or any other] boards. All PWB, regardless of surface finish, should only be handled by the edges. * This gloved handling maybe more important for operators at the fabricator.

Side note to possibly link the storage and handling issues: Most immersion silver finishes have a co-deposited organic anti-tarnish in them.

ISSUES WITH IMM SILVER * We worry that we made a mistake selecting this material, because the market has not accepted it well and has largely gone to ENIG. * There is not much information about the stuff, not many assemblers are using it, assemblers complain about ENIG, there is not much information about the stuff, not many assemblers are using it, assemblers complain about bla bla bla * �Does anyone have any experience of this finish causing any adverse effects - exceptional to HASL?� Not sure what the question means. * We see no change in our solder pot analysis after 6 months, but on the other hand, this product accounts for maybe LT 5% of the board feet across the wave. * Solvents used for solder paste misprints does not appear to effect the solderability of the imm silver coating. * Insure that the imm silver PWB is completely dry prior to storage or processing. * Does imm silver eliminate migration issues associated with thick pure silver deposits? Do samples meet UL-796 silver migration test requirements?

INDUSTRY STANDARDS OR SPECIFICATIONS ON STORAGE We are aware of no industry standards or specifications on storage.

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