Hi,
I would really appreciate some help here..
I am running some mixed board (thru holes with SMD) over wave.. after the wave, I discovered almost 80% of the boards are spatter with small lumps of solder dross on the under side... (between three to five counts of them)

I am using Tamura no-clean flux and on board preheat temp is peak at 100degree for 10 sec. the whole preheat zone runs at 80 sec..

am using Alpha Metal solder bar ..and adopting spray fluxer technology, no clean process..

I hope that someone could highlight and share with me the reason (if possible solution) for the formulation of solder dross on the under side of mixed technology boards after wave.

thank you very much
Darren

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