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Concerned about the storage of SMD components
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Concerned about the storage of SMD components
I have heard that SMD components suffer from humidity when stored for a long period. Is that correct?
The solution seems to be to bake them in an oven. seriously, i just don't get it

Currently this is the main point why I'm not considering SMD.
There are some SMD components which are moisture sensitive, such as newer high-density ICs. The vast majority of SMDs though are not moisture sensitive, and can be stored without any humidity requirements. The humidity requirement is mainly for attaching parts in a reflow oven, as the overall heat will cause steam to form in the package and create micro-cracks. Even JEDEC and IPC (the main circuit assembly standards boards) note that moisture sensitivity precautions don't need to be taken if you are hand soldering.

I store a bunch of SMT components in my lab, and the ones that are moisture sensitive have a desiccant bag combined with a humidity card to let me know what's up. I do this because sometimes I have a part reflowed at local assembly houses, and don't want to pay the extra cost for them to bake the moisture out of the part before reflowing it.
The epoxy used for chip bodies actually absorbs moisture. We think of it as a rock hard material, but it's not. If the moisture content is too high and it gets heated quickly the epoxy can crack or break the bond inside to the chip.

With DIP packages the bodies are much thicker and during automated assembly the heat from soldering is applied to the leads sticking through the board, so the bodies don't get so hot.

With modern surface mount parts the bodies are very thin and in automated assembly the heat is applied from above (or all around) in an oven. So they are much more likely to get hot and get damaged if they have moisture in them.

Hand soldering doesn't heat up the body so much, so usually isn't an issue.
Thanks a lot for the explanations! applause
le maƮtre
This is a little tip when i store old valuable Ic's in anti-static bags, I throw in a small silica bag to absorb humidity, works great and no oxidation on pins.
Try silica when storing for long periods of time with your SMD
I just received an ARM microcontroller which two out of the three indicators on the attached humidity card were pink-ish instead of blue-ish, but I don't have an oven to bake the thing. Will see how it goes when the module is finished (I am still missing some parts). confused
Even though it is reassuring to read that hand soldering should not cause too much problems, it is still scary since the card clearly advised to bake the microcontroller.
if hand soldering, you should not have any problems without baking using a little bit of flux.

Good luck !
Finally finished the build tonight and it seems to be working as expected so far w00t
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