Hi Jack - you are getting some excellent details for the herd so I'll just
add one additional comment. In terms of lead-free assembly processing,
understanding the laminate Td (temperature of decomposition) is a critical
parameter because it is a measure of robustness with regards to the higher
process temperatures used in lead-free soldering. In terms of solder joint
integrity, understanding the laminate Tg (glass transition temperature) is
a critical parameter because it allows you to understand the impact of CTE
global mismatch on your solder joint integrity.  Both laminate
characteristics are important and need matched to your product use
environment.

Dave Hillman
Rockwell Collins
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On Wed, Apr 13, 2016 at 9:08 AM, Jack Olson <[log in to unmask]> wrote:

> Way back when we were making changes to meet RoHS requirements, we were
> advised to use bare board materials with 170 Tg or higher. So we changed
> our Fabrication Drawing Notes and everything has been fine.
>
> But recently I've noticed that the default material for several different
> suppliers is around 155 Tg. Has the thinking "relaxed" in this regard? Or
> should I stick with my 170 ?
>
> Jack
>
>
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