Kitty,

If this is s through hole board that will see one excursion through the wave, you can probably get away with the old 140Tg material ina  RoHS complaint form.

Tg as a spec is so old school now!  Some of the RoHS complaint 170Tg materials actually degrade to 130 and below after the first heating cycle.  

You need to also spec Td, and Z axis expansion.  And some multifunctional epoxies required to meet these specs can vastly increase the risk of cathode-anode failures (CAF).  So specify CAF resistant epoxy, or specify non-dicyandiamide epoxy (this is a common CAF resistant type)

So if your boards will be reflowed, especially if they will see more than one thermal cycle, try these specs:

LAMINATE MATERIAL SHALL BE IN ACCORDANCE WITH IPC-4101, EPOXY-GLASS LAMINATE, NON-DICYANDIAMIDE, NEMA GRADE FR-4, FLAMMABILITY RATING: UL 94V-0.
         MINIMUM Tg (DSC) 170
         MINIMUM Td (TGA) 330
         MAXIMUM Z-AXIS EXPANSION 25C-260C 4%   (you can alterrnately specify CTE, expressed as ppm/C)

And perhaps most importantly, if you are buying fabs overseas, make sure you use a good shop, don't just broker the boards.  Some have been known to completely ignore your specs and use whatever they can get cheapest.  Cheap isn't inexpensive when your yields drop and failures increase due to "cheap" fabs.  (Unless you are building "throaway" products)

Pete

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