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July 2010

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Subject:
From:
Ian Hanna <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ian Hanna <[log in to unmask]>
Date:
Tue, 13 Jul 2010 12:58:44 -0400
Content-Type:
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text/plain (168 lines)
I don't think it's counter-intuitive Ed.  The moisture will be moving from the surface to the interior, the further the interior is the from the surface, the quicker the moisture ingress and inversely the longer the egress.  Ian

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Tuesday, July 13, 2010 12:47 PM
To: [log in to unmask]
Subject: Re: [TN] BAKING OF PWB QUESTION

I recently had an outbreak of blowholes at wave on several assemblies from one specific fab supplier. 

I used a precision lab balance to measure the start weight of several assemblies, baked for 2 hrs, cooled and re-weighed, noting the delta, baked for another hour, cool, weigh and repeat until delta last is <10% of delta 1st. Spot-check on X-ray and weigh the original samples above to monitor re-ingression. 

I did notice the thicker & more complex the assemblies, the greater the deltas and longer the bake required. Counter-intuitively, the thinner & simpler the assy, the faster re-ingression took place.

Regards,

Ed Popielarski

Sr. Mfg. Engr.


NBS Corporation
2950 Patrick Henry Dr.
Santa Clara, Ca. 95054

Ph: 408-654-1100
Fx: 408-654-1107
Cl: 408-234-1497
Cl: 949-581-6601

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Tuesday, July 13, 2010 9:30 AM
To: [log in to unmask]
Subject: Re: [TN] BAKING OF PWB QUESTION

Guys,
Wouldn't it vary with:
1) Temperature
2) Thickness of board
3) Area of board (and thus perimeter area)
4) Solder mask and coverage
5) Environment the board has previously seen
6) Material the board is made of?

Bev
RIM

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Bogden
Sent: Tuesday, July 13, 2010 11:44 AM
To: [log in to unmask]
Subject: Re: [TN] BAKING OF PWB QUESTION

Our experiments have shown and we implmented 1 hour max




________________________________
From: "Roberts, Jon (SA-1)" <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, July 13, 2010 10:35:09 AM
Subject: [TN] BAKING OF PWB QUESTION

Is there a rule of thumb or any best manufacturing practices of how long
after baking does the PWB have to be processed?  Jon


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