You may wish to also check oscillators (VCXO, OCXO, OSC, etc) as I know based on past experience that baking them over 85C can cause them to age and go off frequency.  This may be more of any issue with low PPM parts, but something to watch out for.  We've had to lower our bake out of built assemblies due to them and a few other parts down to a max of 85C.  The assembliers don't like it because it take more time, but it beats replacing an expensive part.

Best,

-Jeffrey Jenkins

-----Original Message-----
From: TechNet <[log in to unmask]> On Behalf Of Stadem, Richard D
Sent: Monday, March 25, 2019 7:17 AM
To: [log in to unmask]
Subject: [EXT] Re: [TN] Rework

Even though J-STD-033 guidelines call out for a 125 C bake, I don't ever do it. It can damage parts, especially if longer than 4 hours.
I just never bake at hotter than 105C, but have no problems with baking at 105C for 12 hours or more. I have never seen a part that did not have at least 80% of saturated moisture removed when baked at 105C for 12 hours. After that, there is little additional moisture removed per hour, so all you are doing is oxidizing the leads and there is no point in it. In most cases, an 8-hour bake at 105C is sufficient.
If you get any component down to 20% or less of its saturated moisture content, you will not have any issues during reflow and rework at normal leaded or leadfree temperatures, assuming the parts were designed to meet those reflow temps in the first place. At least, that has been my experience.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vargas, Stephen M
Sent: Monday, March 25, 2019 8:41 AM
To: [log in to unmask]
Subject: [TN] Rework

Good Morning:

      A rework/component question. We deal with some high density assemblies here (high mix) and periodically we need to perform rework with our hot air station. We manage our moisture sensitive material here per J-STD-033, particularly prior to SMT reflow. However, if we have an assembly that needs rework and assuming there are moisture sensitive parts very close to the reworked part, the thought process is that the entire assembly would require baking prior to starting rework. The question is whether all SMT components are capable of withstanding a bake process of 125 degrees C for 4-48 hours without damage? I understand this is a general question, but I'm wondering if I need to pull datasheets and contact component suppliers to confirm this or if it is universally accepted that SMT parts can handle this (wishful thinking............). Thanks in advance.

Regards,
Steve Vargas
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