Bob,
While there are no "official" standards yet for tin whiskers, the NEMI
document is an excellent start. Both JEDEC and IPC are working on "official"
documents to cover this phenomenon. JEDEC work is focused in Committee 14,
actually meeting this week in San Deigo on this very issue. IPC is working on a
guideline, focused in Committee 5-23e, under Assembly and Joining.
The NEMI web site gives the proposed standard - a baseline for both the JEDEC
and the IPC documents. The NEMI document proposes three classes of use -
class one does not allow tin plating on components, class two allows up to 40
micron whiskers, and class three (most liberal) allows whiskers to 65 microns. A
number of factors are called out in the NEMI document - nickel underplating,
fusing the tin, plating thickness, etc. Another feature, expected in the
more formal JEDEC and IPC documents are two kinds of qualifications - technology
qualification of different plating baths, plating thicknesses, and substrates
being plated. The second qualification will be "process" - specific plating
lines, plant location, etc. Also, much attention is paid to procedures for
testing tin whisker growth, measuring whiskers, and reporting maximum whisker
length.
A working session on the IPC guideline will be on February 24 at IPC Apex.
Denny Fritz
MacDermid, Inc
Chairman of IPC 5-23E Committee
*********************
Subj: Re: [LF] NEMI Class 2 (Wisker length 40 micron max)
Date: 1/25/05 8:33:29 PM US Eastern Standard Time
From: [log in to unmask]
Reply-to:[log in to unmask]
To: [log in to unmask]
Sent from the Internet (Details)
Reuven:
The NEMI test method and the classes can be downloaded from the NEMI website
at:
http://www.inemi.org/cms/projects/ese/tin_whisker_activities.html
Select the link "paper" next to the item Tin Whisker Acceptance Test
Requirements (NEMI Tin Whisker User Group, updated July 28, 2004)
Class 2 is the best performance rating you can get from a tin plating.
Cheers,
Bob Hilty
Tyco Electronics
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