2019-BTU-web-Vacuum-reflow-Dimock.pdf - 第8页
V apor phase reflow + vacuum: expensive, slow , messy Large voids are more likely to contact expose d solder surfaces and escape Why V acuum reflow? Convection reflo w + v acuum: no v apor, faster throughput, minimum mes…
Why Vacuum reflow?
“Low void” pastes
Michael Meilunas, “Solder Joint Void Analysis: Effects of Paste and Reflow Parameters”
AREA Consortium
Low Void Paste
Hot Profile
Average Cumulative Void %
Standard Paste
Cold Profile - Air
Atmosphere
Paste
Profile
MFL100
Standard NC
Cold 33%
Air Cold 19%
Low Void Hot 13%
very Hot
13%
Cold 18%
Nitrogen Low Void Hot 13%
very Hot
10%
Vapor phase reflow + vacuum: expensive, slow, messy
Large voids are more likely to contact exposed solder surfaces and escape
Why Vacuum reflow?
Convection reflow + vacuum:
no vapor, faster throughput, minimum mess
Vacuum reflow has been shown to be effective at reducing solder voids
Voids grow as surrounding pressure decreases (Pascal’s Law)
Large voids have an opportunity to combine and become larger voids
Vacuum Chamber is placed
between the last heated zone and cooling section
with automated board transfer in and out of the chamber
Inline vacuum reflow oven