Solder Paste Homogenizing and Degassing: The Hidden Switch Behind SMT Yield
Solder paste homogenizing and degassing is the process of re-suspending settled solder powder and removing entrapped air before stencil printing — the first quality gate of the SMT line.
Solder paste state decides print quality and joint yield, yet many factories control storage and warm-up while skipping the mixing step that matters just as much.
What Bad Mixing Costs You
•Tin powder settling and clumping.
Heavy solder powder settles during storage and shipping; under-mixed paste blocks stencils and prints thin.
•Entrapped air.
Bubbles become voids in reflow — a hard failure for automotive and medical electronics.
•Uneven flux distribution.
Separated flux lowers wettability and raises the risk of skips and bridges.
The Recommended Workflow
Warm the refrigerated paste to room temperature per specification (usually 2 to 4 hours) so no condensation enters.
Then mix and degas on a planetary centrifugal mixer: for example, 1000 to 2000 rpm for 1 to 3 minutes, with vacuum optional — tin powder re-suspends evenly and air is fully expelled.
Finally, check gloss and uniformity, and only print when the paste shows no separation.
Why Centrifugal Mixing Beats Hand Stirring
Hand or simple stirring cannot break up settled agglomerates and usually folds more air in.
A planetary centrifugal mixer works in a sealed cup, so mixing and vacuum degassing happen in one step with no metal contact and no contamination.
For SMT Engineers
Put paste mixing and degassing into your standard operating procedure, and log the parameters of every batch — this prevents void-type defects better than any post-inspection.
SMIDA covers the full range from 150 g lab samples to industrial large-capacity machines, and sample testing is welcome.
Yield is often won on these hidden switches.
Send a solder paste sample to the SMIDA lab for a free mixing and degassing test, and compare the void results for yourself.
