Ioan,

In the early nineties of the last century I had to find leadfree
alloys that coped as much as possible with the materials used that
time with SnPb wave soldering. I started with worst case alloys as the
eutectic SnCu (227dC).

I met the same problem you have: freezing the alloy in the cool areas
of the solder pot with a temperature setting of 265dC. It turned out
that for wave soldering the pot temperature should be as high as 280dC
to prevent freezing. Even at 275dC icicles were common found on for
instance at axial mounted power resistors.

With Sn100 as solder material, I guess that you also need about 280dC.
Not to speak of the temperature shock that the assembly will undergo.

Conveyor speed was as usual: 1.00 til 1.35 m/min for a contact time of
about 4  seconds, depending of the length of the solde wave. Any
faster speed reduced hole filling in DS assemblies.

VOC-free fluxes required a preheat temperature of 135dC to prevent
explosive evaporation of water in holes and vias.
Colophony fluxes residues gave burned debries in the solder pot very
soon, ininiating glowing phenomina when tinoxides SnO oxidized into
SnO2 spontanuously. So also due to the high pot temperature an oxygen
free environment will be inevitable.

At last we ended the search with the now common accepted SAC-alloy
with its pepper and salt additions for special solder properties.


Peer Langeveld
Consultant Soft Soldering Processes
5502 VH 8  The Netherlands





2007/11/28, Ioan Tempea <[log in to unmask]>:
> Dear Technos,
>
>
>
> I have moved to this new company and here we're running SN100C in wave,
> as opposed to the SAC305 I used to have before. So I have to start all
> over defining the baseline process parameters.
>
>
>
> Besides frequent shorts and solder not going all the way to the top, we
> have an issue with solder freezing at the corners of the solder pot. To
> overcome this "chilly" issue, we were suggested to run the pot at 540F!
>
>
>
> So I would like to know where you are with the SN100C:
>
> *          What pot temperature
>
> *          What conveyor speed range
>
> *          What flux (special formulation for the alloy or regular,
> solids content, water or alcohol based, etc)
>
> *          Nitrogen or not
>
> *          Other particular points of interest
>
>
>
> Of course an insight regarding the attainable defect free yields would
> also be appreciated.
>
>
>
> Thank you,
>
>
>
> Ioan
>
>
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