We have often seen flux separating and pooling in the tubes if they are kept much longer than shelf life, both in or out of the fridge (usually engineering samples that are left over). One of the advantages of tubes is that operators can't whip it up and shear thin the paste before using and cause separation at any time. I have not seen any poor solderability when we have experimented with expired paste, but have not specifically tested for this reason. The separation will occur before the solderability is affected and will be an issue when printing. It is hard enough to control a printing process, so make sure you have good paste controls. Best to organize regular monthly shipments of paste, and manage usage, and don't treat it like sour cream (best before, good after). You should not have to scrap much paste and still be able to work within the shelf life. Roger Mack P.Eng. Manufacturing Specialist Parker Hannifin Canada Electronic Controls Division 1305 Clarence Avenue Winnipeg, MB R3T 1T4 Canada direct 204 453 3339 x373 [log in to unmask] www.parker.com/ecd From: "Robert Kondner" <[log in to unmask]> To: "'TechNet E-Mail Forum'" <[log in to unmask]>, <[log in to unmask]> Date: 06-20-2011 14:25 Subject: RE: [TN] Solderpaste Storage and Use Hi, I do wonder where all these shelf live ideas comes from. Seems to me that particle size and flux type will make a BIG difference, like a power of 10 or so. A no clean type 3 paste with low levels of activity would seem (at least to me) to last MUCH longer than say type 5 in an active OA flux. Has anyone ever done reflow studies for different types of old paste? I don't think a paste manufacturer would do such a test, I expect to get blasted for even suggesting the idea. But, Look at this link: http://www.endtimesreport.com/Prescription_longevity.html Bob K. Hmmm, I have a bucket of ancient paste tubes. I should give them a try. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Mack Sent: Monday, June 20, 2011 3:12 PM To: [log in to unmask] Subject: Re: [TN] Solderpaste Storage and Use Most pastes have a refrigeration spec. which gives it a shelf life of 6 months. If you are using 600g tubes most datasheets will require 8 hours to acclimatise. Once out of the fridge we don't return it either, but always sign initials, date and time on each tube. Create an out of fridge "on deck" storage for 3 or 4 tubes, or a daily amount for a line. We use a fixture that fills from the top and you pull tubes from the bottom like a canned drink dispenser. If you take one, add a new one to the top from the fridge. You will never run into trouble with your acclimitizing time, or pull too much. Your paste likely has a shelf life for room temperature, so set a spec. that discards all open tubes when pulled, for say, two weeks or a month. If you are using jars and storing working paste, sign and date it as well and control the out of fridge time for that as well. Roger Mack P.Eng. Manufacturing Specialist Parker Hannifin Canada Electronic Controls Division 1305 Clarence Avenue Winnipeg, MB R3T 1T4 Canada direct 204 453 3339 x373 [log in to unmask] www.parker.com/ecd From: Amol Kane <[log in to unmask]> To: <[log in to unmask]> Date: 06-20-2011 13:27 Subject: [TN] Solderpaste Storage and Use Sent by: TechNet <[log in to unmask]> I am re-writing our solderpaste use and storage procedures for water soluble and no clean fluxes (SnPb and Lead-free) to say, in essence the following: "To be stored per the manufacturer's recommendations (usually upto 10C), must be at room temperature before it is dispensed on the stencil (at least an hour thawing is required). Maximum use period to be 8 hours. Re-refrigeration and use beyond 8 hours not permitted" The pushback is to the prohibition of re-refrigeration (for use the next day) after it is thawed and use beyond 8 hours requirement. These requirements are due to concerns with moisture absorption by the solderpaste once thawed (affecting slump) and flux activity (due to ageing) What criteria are all the learned folks on technet using for solderpaste management? Is there any literature available that looks at solderpaste use limits on time and temperature? A logical solution would be to do a DOE to look at these parameters, but I am being asked to come up with something ASAP:). love how these things work! Thanks in advance Amol ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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