We are using I-Sn for years for back planes: both the connectors'
vendors and the assembly houses stated that this is the best solution,
even preferable to SnPb HASL. The reason is that thick PCBs (3.5 to 6
mm) with high aspect ratio (up to 10:1 - the hole diameter is forced by
the press fit pins) suffer from the dog bone effect of the HASL, that
may leave the middle of the barrel unplated.
We specify minimum thickness of 1 micron (~40 u"), matte finish, and
(god forbid for the possible commercial) Stanatech chemistry, that is
stated to be whiskers-free.
Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
SEABRIDGE Ltd. - A Siemens Company
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kaye Clayo
> Sent: Tuesday, November 30, 2004 21:23
> To: [log in to unmask]
> Subject: [TN] Immersion White Tin Plating Specification
>
> Hi Technet,
>
> Can anyone tell me what the plating specification (including
thickness,
> etc.)
> should be for immersion white tin to be used for compliant pin (press-
> fit)?
>
> Also, is immersion white tin the preferred finish for press-fit, or is
> immersion silver or something else?
>
> Thank you in advance.
>
> Kaye Clayo
> Sr. P. C. Layout Designer
> Keithley Instruments, Inc.
>
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