2019-BTU-web-Vacuum-reflow-Dimock.pdf - 第22页

Things to consider  V oids located at critical points (“ hot spots”) may be the real issue  V oid Size Large voids are most likely the primary concern Small voids may not be troublesome Cumulative voiding may only have…

Conclusions:

1. Nothing removes most of the empty spaces

from something

3. Vacuum levels as soft as 245 Torr and short as

5 seconds remove some of the empty spaces.

4. Hard vacuum of 20 Torr with a hold time of 30 seconds

results in void levels of about 2% in MFL 100s

2. It is easier to remove voids from small components

than large ones.

Things to consider

 Voids located at critical points (“hot spots”)

may be the real issue

 Void Size

Large voids are most likely the primary concern

Small voids may not be troublesome

Cumulative voiding may only have a secondary affect

QFN Void Distribution Analysis: QFN100

At 120 Torr and

lower vacuum

levels, the odds of

getting a void larger

than 1% is small