Hi all.
I’ve had a ton of problems with solder paste in the past but am now getting perfect results so just in case anyone else is suffering, I thought I’d share my discoveries with you.
Now I don’t print solder paste every day but maybe once a fortnight. Paste is stored in the fridge between prints with caps on etc. You probably won’t have these issues if you print every day.
The biggest problem I had was getting the paste to stop ‘clumping’ at the tip. I initially found that heating the paste slightly (I left it sitting on top of a power supply) helped with the flow briefly then it went back to clumpiness. I couldn’t believe that was the issue as surely Canadian room temperature can’t be that different to the rest of the world (and if so, it’ll probably be colder 
)
In the end it turned out to be a combination between cleanliness and freshness of paste. So what I found was this:
-
With a new tube of paste, I found that ejecting a small amount without a nozzle on cleared any ‘stale’ paste from the tube. On at least one other tube, this knob of paste was the reason my nozzle blocked. I slice the expelled paste off with a knife and dispose of it.
-
Although I’d love to use a new nozzle every time, that becomes expensive. But the number one thing I have found is to have the nozzles spotlessly clean. And I mean clean The biggest difference between crappy pasting and perfect pasting is how clean the nozzle is. The only way I have found of cleaning the nozzles is an ultrasonic bath with flux remover for 30 minutes to an hour.
With that I paste at -6 or -8 and it comes out beautifully. Many of my pads are 0402 and the smallest I currently print is 0.25 mm x 0.25mm.
I plan to 3D print out a nozzle ‘scraper’ to clear the bulk of the paste out before the bath to hopefully reduce the time of immersion and I’ll update how well that works.
Have fun pasting!
