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July 2013

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From:
Wayne Thayer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Thayer <[log in to unmask]>
Date:
Mon, 1 Jul 2013 15:15:19 +0000
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So if you can't get the board into a drybox or other protected area quickly, keep a pan of water handy to submerge it in!

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, July 01, 2013 10:49 AM
To: [log in to unmask]
Subject: Re: [TN] Moisture in PCB

Some PWBs can re-absorb full moisture content within a few hours after removal from the bake oven. This is dependent on the type of board, the design, and the relative humidity. Circuit boards actually absorb moisture from humidity in air much faster than they do from direct immersion in water.
As a general rule, after baking the boards move them to a drybox (desiccator) if they will not be processed through reflow within 8 hours. If you run batches of the same PWB at a time, and you do not have a drybox, then leave the boards in the oven without any heat applied after the bake is completed. This will help keep them dry a little longer, but only for a day or so at the most.
Refer to IPC-1601 "Printed Circuit Board Storage and Handling Guidelines".
http://www.dr-storage.com/index.asp?lang=2
http://www.seikausa.com/mcdry
http://www.terrauniversal.com/desiccators-dry-boxes/desiccator-storage.php


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Avni Selim Özçukurlu
Sent: Monday, July 01, 2013 6:36 AM
To: [log in to unmask]
Subject: [TN] Moisture in PCB

Hello All,


 


After a wave solder process of a PCB with lots of through-hole components on it, I have seen that there are popcorn part near via on that PCB. The flatness of the first layer of the PCB is gone after that process. I think that moisture remaind inside PCB gets outsite during the wave solder process and cause this problem. I didn't put the PCB in a vacuum oven before wave solder. Is it possible that the problem is related of this. Is there any alternative solution about that problem?


 

Actually I applied the heat up and vacuum to empty PCB before all process of manufacturing. After that vacuum oven process, it has passed about 10 days to start the wave solder process. During that 10 days, did PCB get moisture inside?

 

Thank you advance.

 

Selim.


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