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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