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Immersion Silver

Lee

#18640

Immersion Silver | 11 January, 2002

I am going to be using large numbers of silver immersion PCB's for assembly.

I am concerned about long term storage ( shelf life )and handling prior to placement/assembly.

The recommended 'shelf life' appears to be 6 months but obviously this will be dependant on how they are stored etc,.

Does anyone have any experience of this finish causing any adverse effects - exceptional to HASL ?

Is there any industry standards or specs on storage ?

Should the handling of boards be limited to glove wearing operatives ?

thanks in advance

Lee

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#18642

Immersion Silver | 11 January, 2002

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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Yngwie

#21351

Immersion Silver | 29 August, 2002

I have seen several Imm Ag pad on the assembled board which have a copper colorleaching through the silver plating This happened on the pad which was not deposited with paste during the assembly process.

Don't know if it is a problem, but we only had these assembled boards a month and it appears they are already "oxidizing/leaching" whatever the correct term is. By the way, the boards have just been sitting around at no extreme temp or humidity cycles.

Guys, would you know anything about the immersion silver where all pads need to be reflowed?

Pls help.

-----Original Message----- From: Brad Ferkol Sent: Wednesday, August 28, 2002 10:10 AM To: Vahid Vatannia; Pam Kesler Subject: FW: Nanya silver plating

fyi... -----Original Message----- From: Braasch, Robert A [mailto:robert.a.braasch@intel.com] Sent: Wednesday, August 28, 2002 9:26 AM To: Reynolds, Dan; Boggs, David W; Martin, Michael H Cc: Fresch, Robert; 'Deneil_Logiudice@Jabil.com'; 'Brad_Ferkol@Jabil.com' Subject: RE: Nanya silver plating

Dan,

Good catch. Using immersion silver requires all pads to be reflowed. Jabil should know this as they are the ones that told us. Michael, can you root cause what caused the operations gap? Is it an issue in the way we provided the stencil info to Jabil or was this a Jabil miss? Rob

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#21449

Immersion Silver | 8 September, 2002

Would you be interested in a chemical free flexible packaging (bag) that extends the useful shelf-life of fabricated pc boards and surface finishes for that year or more? Let me know, and I'll get you all the technical details. Sincerely, Dave Salverian DTP, Inc. www.dasalintercept.com

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