| | What is the lifetime for a typical solder paste ? | | How long can boards be stacked waiting before the paste goes off ? | Lifetime and tack time depends on: | - Manufacturer | - Flux/mixture | - Environmental conditions | Typical lifetime is dependent on storage, check the | date code on the container. A viscosity test will | verify if it's still "good". | Tack time, how long it can set before reflow, is | typically around 4-6 hours though I've had some | vendors claim as much as 24 hours (???). I agree with the above three variables; Manufacturer, Flux Type, and Environmental conditions. From my experience, you need to get the components placed and the PCB reflowed within an hour or two using a water soluble paste otherwise you'll run into problems (I'm out here in "Silly-con Valley", so I'm not all that hot or dry out here). Now with a no-clean or RMA flux paste, I've hand placed prototype boards starting on one day, covered the boards and put them in the 'fridge at quitin' time, and then finished hand placing them the next day...believe it or not they reflowed fine!!
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