Electronics > Projects, Designs, and Technical Stuff
Vapour phase Soldering
ElektroQuark:
Quote from: jeremy on Today at 09:47:20 PM
Asscon (related to siemens?)
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I looks like the use a SIEMENS PLC to control the system (logo on LCD screen).
jeremy:
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--- Quote ---2) depends on the amount of heating. Seems like as long as the board is in the vapour and not the fluid it will be ok. If you're talking about density, it is heavier than air.
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I was more thinking about physically how high the vapour cloud will be, and how big the "zone" between 'air' and the vapour will be. ( there will be some 'transition zone' )
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The vapour cloud height should actually be a function of the heating amount. My simple understanding of chemistry says that you will get more diffusion by injecting more energy into the system, hence more height. In the 3M video, they clearly solder 2 LGA1155 cpus in height plus some, so that's 37.5mm * 2 + a bit >= 75mm of "soldering zone". Sure, its a lower boiling point fluid, but it's a ballpark at least.
Some interesting historical patents (I found these on the derwent innovation index which I have access to, but they are all on google patents for free):
US 4394802 A - Counter-convection vapor control system; similar to free_electron's pic
US 4549686 A - Vapor phase soldering using perfluorotetradecahydrophenanthrene (C14 F24); this seems like the original commercial patent, but uses CFCs
US 4628616 A - Vapor tank; Hitachi patent on a vapour phase soldering tank
US 4996781 A - Vapor reflow type soldering apparatus with an improved flux separating unit; a later Hitachi patent
US 4681249 A - Vapor phase soldering apparatus; a continuous soldering system
US 4806662 A - Fluids having an oxetane structure and improved characteristics for special applications; the original "galden" patent
The original galden was created by a company known as Ausimont in Italy. Since galden lists Italy as the contact on the msds I became a little suspicious, so I did a bit of poking around and sure enough I also discovered that they merged with solvay later on: http://ec.europa.eu/competition/mergers/cases/decisions/m2690_en.pdf
Will post if I find any more interesting stuff.
coppice:
--- Quote from: jeremy on January 22, 2015, 10:19:48 am ---US 4549686 A - Vapor phase soldering using perfluorotetradecahydrophenanthrene (C14 F24); this seems like the original commercial patent, but uses CFCs
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The fluids we used in the early 80s for leaded soldering were CFCs. The electronics industry used to put enormous quantities of CFCs into the air back then. Boards were mostly cleaned with CFC113, commonly referred to as "trik", and the stuff was cheap enough that it was allowed to evaporate quite freely.
jeremy:
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 ( :-// ) 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 :P
ElektroQuark:
How do they use the vacuum?
If you apply vacuum the boiling point of liquid drops highly, so the temperature necesary for the soldering can't be reach.
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