VOC Free No Clean Solder Balling

Sounds like the mask to me. Had a similar situation a couple years ago. The mask wasn't fully cured, so it absorbed water that the preheaters couldn't dry out. When it outgassed at the wave, it caused a lot of micro turbulence that broke the surface tension of the solder and created a zillion little solder balls. My wave wasn't fully inerted, so I also had the pleasure of microdross clinging to the mask and shorting test points.

One way to check to see if the mask is fully cured is to take a swab of methylene chloride (if you can get it in your facility) and rub it across the mask. If it comes up green, the mask isn't fully cured.

The same thing will work with IPA if the mask is really bad. If it's just marginal, you'll need the methylene chloride.

Doesn't offer a solution, but a potential root cause.

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