Hi all,

I ordered some ADXL345, HMC5843 and ITG-3200 .. all off them are marked as moisture sensitive devices. On the specs they say that they can get damaged after opening the moisture protective bag.. They say that once opened they would have a life of ~ 160 hours..

Is that true? If so, why they don't moisture break when soldered on a PCB?
If once opened the moisture protective bag do you think they could get damaged if I store them in a dry place at 25 degrees C?



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Once they are soldered to a board, moisture does not matter, because they (hopefully) will not be soldered again.

What happens is that you open the bag, and moisture from the air (slowly) gets into the device. When you put the part on a board and put the board in the oven to melt the solder, that trapped moisture turns to steam and the component explodes. So, you keep the parts in their dry bags until you are ready to manufacture the board.
Ok, thanks for explaining.. I have a couple ITG3200 chips which have been exposed to the air for 3/4 weeks.. Do you think they got corrupted? Is there a way to verify the status?

Wouldn't be possible to leave them in a pre heater for some time (oven at a very low temperature) to remove the moisture?
If you are going to hand solder them, then no problem.

If you are going to squirt paste solder on the board, place the part and then bake in an oven then maybe there could be a problem.

Some parts are more susceptible to this than others so it's difficult to say for sure. Assembly houses, when faced with this will follow instructions that come with the parts. The instructions say something like "bake in an oven at 90 C for four hours or so... this gently evaporates any moisture.

If you have stored the chips in an area subject to high humidity, you may have more problem than if you stored them in a low humidity area.

Sorry to be so vague... check google.
Thanks for your help. I actually checked google before posting here but I didn't find anything.. do you have some link to share on the topic?
No link off hand. Search google on this phrase:
moisture sensitive devices
and you should get some hits that explain it a bit.
Found this good pdf with lot of informations, even how to reflow them correctly:

Hope this helps someone else.

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