2019-BTU-web-Vacuum-reflow-Dimock.pdf - 第12页
V acuum level The amount of vacuum 0 100 200 300 400 500 600 700 800 Levels as low as 1 and high as 250 T orr (and higher) are possib le Experie nced signi ficant void reduction even at 250 T orr
Pump Down
Rate at which vacuum is applied
Too fast
Voids explode when leaving the joint
causing solder balls and splatter
We experienced parts moving and flipping
with a 100 Torr/ sec pump down.
0
100
200
300
400
500
600
700
800
30 to 60 Torr / sec
at hard vacuum levels
Vacuum level
The amount of vacuum
0
100
200
300
400
500
600
700
800
Levels as low as 1 and high as 250 Torr
(and higher) are possible
Experienced significant void reduction
even at 250 Torr
0
100
200
300
400
500
600
700
800
Hold time
The time at the chosen vacuum level
Hold times as short as 1 sec
and long as a few minutes are possible.
At 1 sec there is little time for voids to
move to the surface
Times greater than 40 seconds have
been proven to not be needed