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Date: | Tue, 16 Jan 96 13:58:49 PST |
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We are switching from HASL to Ni/Au process and realize that on Ni/Au
boards, solder paste is not spread out as well as HASL process.
Wettability of the pad edge becomes a major concern. I have some
questions regarding Ni/Au process and would like to discuss with anyone
who have been involved with this alternative surface finish.
Is this problem associated with the inherent nature of Ni/Au material
surface characteristics, or is it associated with the oxidation and/or
contamination of the metal surface (Although Au is very stable, Ni tends
to oxidize even at moderate temperature ) ? It has been recommended to
use sulfuric acid or plasma to clean Ni/Au surface, is it a feasible
approach? If yes, who shall perform this cleaning step: PCB fabricator
or PCB assembler?
By the way, what is the shelf life of Electroless Ni/Immersion Au board
under normal storage condition? Our vendor claims that HASL and OSP both
have the avg. shelf life as 12 months, but is unable to provide the
corresponding avg shelf life for Ni/Au.
Thanks in advance for any response.
Nora Xiao
Process Engineer
Tektronix, Inc.
Beaverton, OR
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