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November 2005

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Subject:
From:
"Dehoyos, Ramon" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Dehoyos, Ramon
Date:
Wed, 16 Nov 2005 09:18:10 -0500
Content-Type:
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                Hi Tom:
                          More than likely is what you are suggesting.
To eliminate that possibility, you could send those parts by themselves
through the reflow oven and they might just outgas all the organics or
moisture that is trapped in the terminations that are causing this
problem, then install them on the board and see if that is a patch cure.
It seems to me that eventually you need to work with the part
manufacturer to find the root cause.
         Regards,
         Ramon
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gervascio, Thomas
Sent: Wednesday, November 16, 2005 8:49 AM
To: [log in to unmask]
Subject: [TN] Snap ,crack and pop

We have been seeing solder fines all over some PCMCIA boards we have
build. We checked the degree of cure on the PCB, paste volume and paste
oxidation and slump and checked the oven profile (tried both a ramp-soak
and ramp to spike profile with 1 C/sec ramp rates). We then found that
it only happened when certain resistors were used. All I know right now
is that it is a RoHS (tin plated over nickel) on ceramic part- 0603.
 
We put some boards on a hot plate and heard a sizzle and popping of the
paste on a board that had these parts (didn't see the same on a printed
bare board).
What could be outgassing from the part terminations that would interact
with the paste that would cause this explosive phenomena? Could the
parts be tin plated and then fused? could it be some sort of organic
material (brightener) that is remaining and outgassing?
 
 

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