Hi 'bogert4',
Telling us that the "one single bottom preheater set 
at 350C" is meaningless–even with length of preheater and belt speed given it is essentially meaningless. You need the temperature measured on the PCB at both surfaces.
Having said that, you definitely need a preheater on top as well. With one prehater only the PCB will warp due to the thermal gradients. Further, only a relatively short section near the bottom will have a solder connection. Depending on the application, that may be o.k. or a big problem.
If you solder Pb-free, the situation is worse Td as well as TE(50=>260) is more important.

Werner


 


 

-----Original Message-----
From: - bogert <[log in to unmask]>
To: [log in to unmask]
Sent: Sat, 4 Oct 2008 7:36 am
Subject: [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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