Dirty Solder Joints

It could be the nozzles themselves causing the contamination. The coating could be worn off and oxidizing. Or it could be residue on the board or components that wasn't washed off.

reply »

I presume you have a local flux spray with your selective solder machine (I have no idea what you use). If I have a group of leads in close proximity like this, I would be trying to design a well and nozzle setup that I can use to solder all the joints at one time. If you are using multiple hits of a smaller well and nozzle, each time the machine cycles to solder, it sprays some flux. If the flux sprayed is inadequately heated, it is not being adequately interted. Looks like you might be soldering 11 times - spraying flux that many times. If all the flux overspray not withing your solder well so it reaches a temperature adequate to fully activate the flux, that might be what you are seeing. The photo looks like there is a lot of residues. I use selective solder and no-clean process and it important that any no-clean flux reaches full temperature, or it remains active. Also, if you have your flux spray nozzle spray angle wide, you could be spraying on an excessive amount of flux and spraying flux right over the joints that were already complete. It looks like you have a whitish residue - unless that is just poor lighting reflection.

This message was posted the Electronics Forum @ SMTA

reply »