Bob,
The old component is extremely easy to remove. We've tried that on several boards and have had no problem.
The new component will not let go, at least in most cases. It's almost like it's glued to the board.
Leland
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Tuesday, March 27, 2012 3:18 PM
To: 'TechNet E-Mail Forum'; Leland Woodall
Subject: RE: [TN] Rework Concern and Question
Well,
Someone tears off some pads during rework and so maybe the PCB was bad?
I have heard that many times. Amazing how easy hot copper comes off a board. I can't help but smile! :-)
But I am curious about what happened!
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, March 27, 2012 2:18 PM
To: [log in to unmask]
Subject: [TN] Rework Concern and Question
Folks,
We've ran across a strange incident and I'd like a little advice from the group.
We recently underwent a component vendor change, and part of the first group of boards were misbuilt due to incorrect polarity (the part marking was misinterpreted by the vision operator).
Anyway, an attempt to remove the part by our Repair group resulted in lifted pads on 10 of the first 12 boards. We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone. The old style component comes off quite easily (within 3 seconds), and an analysis of its leads shows to be 100% tin. It's a 6 pin diode with very little mass.
What's going on here? Does a 2% silicone mix raise the melting point of solder by 200 degrees C?
Please help me understand.
Thanks,
Leland
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