A few more (not sure if these are available on google patents):
DE20300375-U1 - Cooler for workpieces or components under cooled vacuum dome, especially in vapor phase vacuum soldering installation; Asscon patent from 2003
DE20300374-U1 - Assembly for temp. treatment of workpieces or components in controllably heated vacuum dome; similar to above, also from asscon
US 20070194083 A1 - Process and device for soldering in the vapor phase; IBL patent on using a vacuum to stop void forming inside joints. Still valid! This is the company that sells the US$6k/AU$26k (
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif.pagespeed.ce.5xOqKkq0Co.gif)
) machine mentioned earlier
US 4871109 A - Vapor phase soldering using certain perfluorinated polyethers; chemistry patent from everyone's favourite chemical company: Monsanto
http://www.emeraldinsight.com/doi/abs/10.1108/SSMT-10-2013-0028 - A very recent paper on solder voids due to vapour phase soldering
I read the paper but its not free access so I'll give you all the short version: yes you get voids without a vacuum. RoHS or not doesn't seem to make a difference.
http://www.emeraldinsight.com/doi/pdfplus/10.1108/eb037911 - Voids in BGAs.
Again, not free, but the summary is:
- convection oven with changeable air/nitrogen supply
- all BGAs originally came with no voids (verified by xray), Sn63 balls with ~1.5mm pitch
- no vacuum was used
- going to higher temps means more % voids
- flux/paste solvents with lower boiling points tend to cause more voiding (solder paste solvents are worse)
- recommended profile with worst solder paste caused about 1-2% voiding, best was 0.5%
- mesh size of the paste balls does show a minor trend towards smaller being better (200-300um instead of 500um), but it is so slight that I'm not buying it
- reflow atmosphere doesn't matter (air or nitrogen) with respect to void formation
- flux activity doesn't matter
Hopefully someone else is finding this as interesting as I am
![Tongue :P](https://www.eevblog.com/forum/Smileys/default/xtongue.gif.pagespeed.ic.J5mTe0A2NA.png)