Dave,

As you know the common practice in the Japanese industry, where there is a
concern about "droop", even for tin-lead soldering, is to have a central rail
running through the wave to provide support for large heavily loaded single
sided paper phenolic boards.   A line for that rail is designed into the board.
 More conventionally there are the usual jigs and leading and trailing edge
stiffeners that can be used if warp is a concern.    And some people go up a
notch on the Tg.

Interlaminate fracture has not been an issue that has been raised amongst the
many users.

The most common solder temperature used amongst the approximately 400 lines
running at the moment would probably be 255C with topside preheat in the
100-110C range and contact time close to 3 seconds but of course those are the
parameters that have to be adjusted for each particular board.     As I have
pointed out before, large scale production experience has mainly with consumer
electronics, although consumer electronics these days extends to quite
sophisticated multilayer boards.  So far there have been no surprises as the process has
been adopted for professional electronics.

Keith Sweatman
Nihon Superior Co., Ltd

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