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SMT electronics assembly manufacturing forum.

Paste Expiration

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Paste Expiration | 20 February, 2008

Wanted to get this out there to get a feel for what everyone is doing with their paste after they crack the original seal. The life clock obviously doesn't stop once its opened and at room temp so one cannot solely go by stencil life alone....I imagine there are a lot of low/mid volume guys out there that have to rejar at the end of the day in a new jar....

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Paste Expiration | 20 February, 2008

I don't know if it's the best or proper way. We have a seperate jar that the paste that comes off the stencil goes into. All used paste( of the same manf.) goes in this jar and back into the refrigerator. The remainder of the new jar goes in the fridge as well. The next day this paste is used with any additional paste needed coming from the new jar.

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Paste Expiration | 20 February, 2008

Yeah, it blows, but basically we toss it when it quits printing. We've never seen any visible quality issues we could attribute to recycling paste like this so we keep doing it. When we start doing BGA and X-raying stuff we'll take a closer look at what effects we might be missing. I hate it but you do what you can with limited resources.

At my last job paste handling was tightly, we use up what we're able to.

We don't buy jars, just the 600ml cartridges. At the end of the day we transfer what's left on the stencil to a jar (IF that paste came out of a tube) and cram the plug down on it to slow down the inevitable. If the paste on the stencil had been dispensed from a jar, we toss it. The cartridge goes into the fridge and gets used up first when we run again, then we dip into the jar to see how it prints. If it won't, we toss it.

Anything from 25 mil pitch or tighter gets fresh paste from a new tube.

Fortunately we don't have to worry about going past expiration dates because we only buy a box at a time and use it up well within the specs.

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On-board Dispensing of Dots & Lines

SMT spare parts - Qinyi Electronics