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printed solder paste life time

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#79568

printed solder paste life time | 7 January, 2018

Hi everybody. I'm new at SMT soldering. I'm using a stencil to print solder paste on PCB. and my board has 0402 components that it make assembling process long so I can't complete a set of board in a day and I have to continue in the next day. what can I do to prevent of drying printed stencil? Can I put it in refrigerator and do it in next day?

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#79569

printed solder paste life time | 7 January, 2018

Your paste should specify a number of times it is OK for various things to happen.

The two you might care about are the "Stencil Time"/"Working life", which is how long the paste can be out of the pot on your stencil while you print PCBs.

The other is "Tack Time" which is how long the paste can sit on the printed board before you apply components and reflow. Beyond this time the paste can dry out or "slump" (create shorts by spreading out).

On traditional Pastes these times are often quite short but there are a number of Pastes these days that extend these times and can be extensively mistreated. Here is an example http://bltcircuitservices.co.uk/wp-content/uploads/2016/12/LED-3-Non-Refrigeration.pdf

Plenty of pastes are perfectly fine just left on the PCB for 2-3 days but this will depend a little on the room conditions.

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#79598

printed solder paste life time | 10 January, 2018

Hello, which type solder paste are you using?

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#79610

printed solder paste life time | 11 January, 2018

I use this one Chip Quik Inc. SMD291AX250T3

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#79643

printed solder paste life time | 23 January, 2018

Hello, it is written in the datasheet: Stencil Life: >8 hours @ 20-50% RH 22-28°C (72-82°F) >4 hours @ 50-70% RH 22-28°C (72-82°F)

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