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From:
"ddhillma" <[log in to unmask]>
Date:
Thu, 12 Dec 96 07:42:27 cst
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     Hi Jauwhei Hong -
     
     I can echo Jan's reply - we are soldering SOT's with a dual wave 
     system with only minor problems. Our flux is a low residue material 
     that could be used in a no-clean mode. It has been my experience that 
     the SOT's seem to be a bit less solderable than other components and 
     that your flux selection will have a big impact on your final solder 
     joint fillet. Try a couple of different fluxes and see if you get 
     different results. Good Luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Re: (ASSEM) Wave soldering SOT-23
Author:  [log in to unmask] at ccmgw1
Date:    12/12/96 5:12 AM


> Tom:
> 
> If you are using no-clean flux to solder SOTs (or anything with tall, 
> non-solderable body that will repel the wave from reaching the pad, 
such as
> tantalum capacitors), dual wave would not work. This is because the 
first
> wave (chip or turbulant wave) will kill the flux, resulting in the 
poor
> solderability at the second wave (lambda wave). The way we do it 
rather
> successfully is to elongate the pad size and solder them with a 
vibrating
> wave (omega wave), which has much lower surface energy to reach any 
shadowed
> pads. Good luck.
> 
> Regards
> Jauwhei Hong
> [log in to unmask]
     
Jauwhei Hong,
We don't have any problems soldering SOT's with no-clean flux and 
dual-wave (chip & lambda). We get fine results if we only use an angle 
of 4 degrees, accurate dwell time for the specific pcb and a "perfect" 
preheat profile. We also don't have to elongate the pad sizes, we use 
the ordinary sizes the pick & place do.
     
i don't know, but are we different?
     
/Jan Merstrand
 Operation Engineer
 Ericsson Microwave Systems
 [log in to unmask]
     
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