AVR-Chat

----Original Message----
From: AVR-Chat@yahoogroups.com
[mailto:AVR-Chat@yahoogroups.com] On Behalf Of Steven Hodge
Sent: 15 March 2013 16:02 To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] moisture-sealed packaging

> I realize this is off-AVR topic, but why the sudden(?)
> proliferation of putting parts in moisture-sealed
> packaging (e.g., by Digi-Key and Mouser), when they were
> previously not so packaged?  Must the accompanying Threat
> of Dire Doom be taken seriously if limits are exceeded?  
> Why does it seem    
> limited to just SMT devices and not DIP?
> 

I'm not sure why they have suddenly started, but the reason it's done for SMT not DIP is because of the oven soldering that is used with SMT devices - they can explode/crack when put through the oven due to moisture boiling to steam inside the device.

I have seen it happen quite a few times with LED's, but never with any other devices.

The parts are sealed from the manufacturer, but once they open the pack and start chopping a few off the reel, the reeled parts start absorbing moisture. I can only assume they then re-seal the pack and remove all the moist air, otherwise the packaging to the end user is pointless.

-- 
Tim Mitchell