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In a message dated 11/16/05 15:21:55, [log in to unmask] writes:
> Couple questions regarding the dreaded lead free process.
> 1. Do I need to request a different process for PCB fabs, what is
> the difference if any?
> A: It depends. For thin PCBs with components of near-uniform size you may be
o.k.
For thicker PCBs and components with significant differences in thermal mass
you need to specify: hi-Tg/hi-Td/low CTE materials [beware of datasheets--lots
of wrong info on them] [ you may want to specify STII=>215], you need to
specify E3 copper foil for internal layers, you need to specify at least 1.2 mils
of Cu in the through-holes, you need to specify vigorous moisture bakeout
prior to soldering process.
>
> 2. I understand that lead free components require a higher
> temperature and longer reflow time, which may affect other component
> reliability. Not all the components we use are available for lead free
> processes. Any recommendations on the processes to be used with a
> mixture of leaded vs. lead free? Is this wise? What should we be looking
> out for?
> A: iNEMI has determined that for components the MSL rating drops one level
for every 10C increase in soldering temperature
>
> 3. I did not want to recreate the wheel, anyone have a test plan
> or qualification plan available to qualify this type of process?
> A: Look at IPC-9701A at least for a partial answer.
>
> 4. And any recommendations on a lead free process class that we could
> send a few of our technicians to?
> A: Technicians you might send them to some of Bob Willis' courses; Engineers
and Designers you might send to my workshops [next ones in Boston December 5
and 6].
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
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