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SMT electronics assembly manufacturing forum.


solder paste stencil life

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#67841

solder paste stencil life | 15 December, 2012

Normally paste manufacturer specifies stencil life of a paste is 10 hours. the question is, if i run a continuous manufacturing for 40 hours, we will be adding 250 g of paste for every two hours. The addition of 250 g will be mixed with the paste which is already available on the stencil. After first 10 hours of manufacturing, do we need to remove all the paste in the stencil and scrap it?, currently the practice is we keep on adding till the end of production. since this goes by addition mechanism, there may be molecules of paste which has applied 12 hours before. any thoughts in this?

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#67843

solder paste stencil life | 17 December, 2012

I would scrap it. As you said part of it is going to be old paste. All manufacturers don't recommend mixing old with new paste because you change the rheology of the paste.

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#67845

solder paste stencil life | 17 December, 2012

Why scrap paste if there is no degradation of performance? Do your own study to determine this.

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