2019-BTU-web-Vacuum-reflow-Dimock.pdf - 第11页

Pump Down Rate at w hich vacuum is applied T oo fast V oids expl ode w hen leaving the joint causing solde r ball s and splatter W e experienced parts moving and flipping w ith a 100 T orr/ sec pump d ow n. 0 100 200 300…

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Four Basic Vacuum Process Steps
Not including transport
Pump Down
Vacuum level
Hold time
Equalization
Rate at which vacuum is applied Torr /sec
The amount of vacuum Torr
The time at the chosen vacuum level Seconds
The rate at which the chamber is Torr /sec
returned to room atmosphere
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