Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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How temperature and humidity effects solder paste/printing

Adam

#5931

How does temperature and humidity effect solder paste/printing | 11 April, 2001

I'm trying to find information/articles describing the effects of temp and humidity on solder paste. Just recently we have gone through a change outside temperature and humdidty and have notice solderabilty problems with smt boards.

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#5932

How does temperature and humidity effect solder paste/printing | 11 April, 2001

OA pastes are more hydroscopic than NC pastes.

Hydroscopic. The capacity of a material to absorb and retain moisture from the ambient air.

Sometimes this is compounded if you remove paste from the frig and let it warm to room temperature, because the moisture in the air condenses on the relatively cool paste.

As moisture in your paste passes 100�C in your oven, it flashes over to steam and blasts solder and flux particles all over your board. Coo, eh? Oooo, baby talk to me about the NC solder ball whiners, now!!!

Consider controlling the environment of your assembly area [at least your soldering area]. We try to keep within the trapazoid [84�F/30%RH, 72�F/30%RH, 78�F/70%RH, 68�F/70%RH] and we try to limit the rate of temperature change to LT 5�F/hr. J-STD-001 suggests work area environmental controls [I believe, my copy is out in the car and I'm too tired to go get it to check.]

Though less impressive to view, environmental controls like this help lower ESD damage to your products, also.

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