SparkFun Forums

[davethomaspilot]

I need to build 20 - 30 pcbs.

I have solder paste that purchased in January and have not kept in a refrigerator.

Is there a way to determine if its still ok to use, or should I just order up new? I don't want a big hassle in trying to reflow these cards, but would like to get started this weekend if paste isn't bad.

Thanks,

Dave Thomas

[rpcelectronics]

Dave,

I use Lodestar paste. Sometimes the paste will visibly separate and you can see the silver grains and basically some kind of liquid or paste flux in there with it. I typically keep my paste jars in the fridge, but on occasion, I am doing assembly night after night and I leave a closed jar sitting on the bench and this happens. I keep some small wooden stirring sticks handy to stick it back up and get the paste re-distributed. If I ever question if the paste is going to reflow, I plop a small blob down on something metal or even an old PCB and use my hot air station to flow it. Basically its either going to flow or not and it will be dull or shiny. This is a pretty good test to see if your paste is "past it's prime".

Good luck!

[redwire]

I've used questionable paste before- heat/air/moisture are the big enemies. If it's old, I just had to stir it.
It depends on the type of flux and also the PCB and component's. If you have older, oxidized PCB's or parts, it puts greater demands on the paste. 8 months old should be fine, best to simply try it.

[ohararp]

I have some 2 year old paste here that stays at about 70F. Keep it stirred and you should be fine.