The main "enemy" of printed paste is moisture absoption, the next is temperature
swings. 
So to extend tack or usable life of printed pastes you need to store your work
in a temperature stable low humidity environment.  
You can achieve low humidity by putting your work in cabinets which are flushed
with nitrogen. I've no idea who suppliers will be in your part of the World, but
try starting with  clean room or lab equipment house catalogs. 
If you don't have an everlasting nitrogen supply an alternative is to place your
work in a dessicator: simply an airtight box with some silicon gel absorbant.
A refrigerator is a low humidity  temperature controlled environment of course,
but it is also low temperature. So you will have a problem when you remove your
work from it, as moisture in the air is likely to condense on to your paste and
cause all sorts of problems. The nack here would be to keep the work dry till it
has warmed to ambient  ie keep in a closed container. The time scales here might
make this impractical.
You might want to consider a refinement which is to put a little solvent of the
type used to make the paste/paste thinners in the container. This will help
reduce paste dry out if that is a problem. Talk to your paste supplier here.
These ideas have all been tried with some success, for example:
A customer of mine with a very critical application extended the [measured]
usable paste life from 4-5 hours to 20 hours using nitrogen storage - so it does
work.
Feel free to contact me direct if you want elaborations.

Mike Fenner, BSP UK
T: +441 295 720 631 F: +441 295 720 937
100760,351@ Compuser,com

-------------------------------
Hello TechNet - I am looking for some opinions/info on the use of 
     extending the tack life of printed solder paste on assemblies. Yes, I 
     know I should be processing as soon as possible but life on the 
     process floor is far from ideal!
     
        1- Does storage in nitrogen chambers help?
     
        2- Who manufactures nitrogen chambers?
     
        3- Does refrigerated storage help?
     
        4- Any technical papers/resources available in industry?
     
     Thanks,
     
     Dave Hillman
     Rockwell Collins
     319-395-1615
     [log in to unmask]