October 3, 2008

We have an OEM that is wave soldering a 0.125 inch thick backplane assembly. 
  The assembly contains just press-fit VME connectors (added after wave 
soldering) and some PTH and SMT passive parts (capacitors and resistor 
networks).  The SMT parts are hand soldered.  Board material is IPC-4101/21, 
24, 26.

The OEM wave soldering machine settings are one single bottom preheater set 
at 350C with solder pot set at 260C.  Conveyor speed is 0.9 feet/minute.

Solder is Kester Sn63pb37; flux is Kester 971M; flux applied by foam method. 
  Solder machine is older Soltec Model 6551.

My question is; for this specific application, what is the recommended 
maximum preheat temperature?  Seems to me that 350C is too high.  Is this 
high a temperature compatible with the Tg of the FR4 board material?  Is 
there any concern with damaging the board material from overheating?

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