Bob,

You may need to take into account the operating environment before you
choose a finish.  Tin-lead is great in corrosive environments.  Silver and
ENIG, not so good.  There are some houses doing lead free HASL.
Check out Calumet Electronics:

http://www.cec-up.com/

John Laur
Rockwell Automation
Milwaukee, WI




Robert Walker <[log in to unmask]>
Sent by: DesignerCouncil <[log in to unmask]>
01/18/2006 11:39 AM
Please respond to "(Designers Council Forum)"; Please respond to
RWalker2222


        To:     [log in to unmask]
        cc:
        Subject:        [DC] RoHS board finish


Hi All,

I'm doing my first PCB design that will use lead-free components and I
need
to change my board finish from what I've always used.....HASL. I'm looking
for
 any recommendations or comments on the best board finish to use.

The components used on the design will be a mixture of tin-lead and
lead-free (SAC), so I'm not sure if there is a preferred finish to use in
this  type
of situation. I work in a prototype environment where the boards may be
reworked (BGA removal/replaced) a number of times, so I'm concerned about
the
ability of the finish being able to handle being  reworked/reflowed a
number of
times.

I'd also welcome any recommendations on the type of board material to use
since it will see an elevated temperature of up to 260C. I've always just
specified FR4 in the past.

Thanx in advance for any feedback.

Regards,
Bob Walker
[log in to unmask] (mailto:[log in to unmask])

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