To Bogert:

You need to see a profile of the pwb from your OEM, not just the machine 
settings.  Insist on this.  Once you have this, post another technet with 
profile/pwb information (max component and circuit side temperature, 
solder contact (dwell) time.

As for the machine settings, 350C is typical of the preheat setting used 
on the Soltec machine with VOC fluxes.  And 260C (500F) is used widely 
throughout the industry.  I question the .9ft/min.  This all depends on 
the width of the wave and the solder dwell time.  The slowest I've ever 
run on the Soltec (with a .250" backplane) was 2.0 ft/min (which gave me 
about a 6 second dwell time).

Al 





- bogert <[log in to unmask]> 
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[TN] Wave soldering temperature profile question






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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