I guess it "depends!" - I can't believe I have fallen into using that
phrase! - Dependant on the supplier that is - We have been using
Enthone's Alpha-Star process, for some months now, and it's previous
incarnation of Alpha-Level. I am sure that MacDermid's Sterling process
has different specs too. There are several white papers from Enthone
regarding the reliability and robustness of the process and
solderability etc, but I don't recall seeing anything regarding
embrittlement of the solder bath. I guess a call to Enthone may shed
some light on the question. I'll ask and let the forum know.
Colin McVean M.Inst.C.T.
Production Manager
Artetch Circuits Limited
Main: 01903 725365
DD: 01903 712926
Email: [log in to unmask]
www.artetch.co.uk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Susan C. James
Sent: 11 August 2006 16:27
To: [log in to unmask]
Subject: Re: [TN] silver embrittlement
Hi Werner and Colin,
Now I'm really confused. I have the following as one of the notes in my
fab spec for IAg boards:
"Apply immersion silver over exposed copper after solder mask. IAg
thickness to be "thin" as specified in IPC-4553 (0.07 microns typical)."
I admit I only have the final draft copy of IPC-4553. While
investigating
IAg last year, there were several statements from various sources and
with
varying reasons to stay away from the thicker deposits. Has the
recommendation changed and should I be asking for more IAg thickness?
Thanks,
Sue
-------Original Messages-------
Date: Thu, 10 Aug 2006 07:14:57 -0700
From: "Crepeau, Phil (Space Technology)" <[log in to unmask]>
Subject: silver embrittlement
i'm trying to find out what's the safe maximum thickness of immersion
silver to call out on pwb's and smt components to minimize embrittlement
effects in solder joints. can anybody out there help?
thanks,
phil
Date: Thu, 10 Aug 2006 10:23:59 EDT
From: Werner Engelmaier <[log in to unmask]>
Subject: Re: silver embrittlement
Hi Phil,
Treat Ag the same as Au. For ImAg I suggest 0.07 to 0.13 microns as a
good
thickness range. I treat surface treatments in detail in my White Paper
[I
will send you that information by separate e-mail].
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
Date: Thu, 10 Aug 2006 15:34:58 +0100
From: Colin McVean <[log in to unmask]>
Subject: Re: silver embrittlement
Typical recommended coating thickness (for our Enthone Alpha-Star
process
at least) is 0.15 - 0.3 microns (6-12 microinches). Anything less than
this
will lead to poor storage shelf life, tarnishing and/or poor
solderability.
As with all surface finishes, there are trade-off's.
Colin
Colin McVean M.Inst.C.T.
Production Manager
Artetch Circuits Limited
Main: 01903 725365
DD: 01903 712926
Email: [log in to unmask]
www.artetch.co.uk
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