Hi All,
I have done my first hot air soldering this afternoon after ordering a pro board and stencil from JLC. I am using chipquick solder paste (lead free, you cannot buy leaded within the EU as retail anymore).
I warmed the board up for about 20 seconds at 100 degrees (lowest my hot air gun can go) and the board was about 30mm away using fairly large nozzle, about 9mm nozzle. Then upped to 160 degrees to fully melt with air speed about 80%.
From a visual inspection it looked quite good, until i looked with an eye glass. Between my pads are loads of very tiny solder balls, all hanging out on the solder mask. I have tried to get a photo but I don't have a microscope of macro lens so I tried to shoot through my magnifier, you can see the edge of the pad lined with balls but this continues across with ever smaller balls.


Could anyone suggest how to stop this from happening?
I have tried spending more time a lower temperature and the opposite, high temperature and soldering as quickly as possible - these didin't work. I have also tried to replicate the oven profile of the paste with limited success and that doesn't seem to help either. could this be too much airflow? not enough airflow?
My solder paste was warm as i had left it out the fridge for about 5 hours.