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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


When to trash the solder paste

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Roy

#51303

When to trash the solder paste | 3 August, 2007

I would like to know, if the solder paste for SMT is unpacked (the syringe is opened) and is stocked at room temperature, then when I should trash it. After 12 hours/24 hours exposure? Or any other suggested time?

Thanks.

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#51315

When to trash the solder paste | 3 August, 2007

Depends on the manufacturer of the paste...

Rosin-based-flux solder paste usually takes 12-24hr's to fully oxidize with open containers. Water-based flux usually is 3-12hr's, but some have a 24hr open container shelf life...

However, uncertain until you provide the supplier and product name...

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#51316

When to trash the solder paste | 3 August, 2007

Hi Roy,

Depends onmany factors. Your plants environment, the ype of paste, the size of the syringe, your smallest aperture you want to release too, type of screen printer, etc...

Your best bet is to perform a DOE and see for yourself.

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Roy

#51321

When to trash the solder paste | 5 August, 2007

Many thanks.

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#51325

When to trash the solder paste | 6 August, 2007

I concur with Chunks.

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#51345

When to trash the solder paste | 8 August, 2007

I have instituted a policy that probably seems a little extreme to some, but is worth the cost in my eyes. Once a jar of solder paste is opened, it must be thrown away at the end of the work day (Properly discarded, of course). We use the small 250mg jars of paste, as to minimize the amount that is lost.

My company, unfortunately, doesn't have a real good climate control system in place, and the SMT line is in the middle of the factory. I found we are often out of the recommended temperature range of the paste we are using (range was 23C-27C). During the day in summer, and in the morning in winter, our SMT defects would spike.

Anyway, I figured I would share my experience with the question you have at hand.

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Roy

#51348

When to trash the solder paste | 8 August, 2007

Thank you! And I agree with you. The temperature is an important factor. I will check our supplier's control system.

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