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June 2006

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Subject:
From:
"Barmuta, Mike" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Barmuta, Mike
Date:
Wed, 21 Jun 2006 07:39:37 -0700
Content-Type:
text/plain
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text/plain (83 lines)
Ioan: The blowholes you are seeing could be the result of organics in
the tin plating outgassing during reflow. When heated they release CO
and CO2 gases creating voids.

	
Regards
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett WA
	
425-446-6076

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
Sent: Wednesday, June 21, 2006 5:57 AM
To: [log in to unmask]
Subject: [TN] Blowholes pandemic

Hi Technos,

for a couple of days I see occurences of blowholes in the joints of,
guess what, SMT 0603 resistors.

The reflow recipe did not change and we're talking about 2 different
established products, we have run many of each before. One is WS, the
other one no-clean. Each one uses different brand of solder paste, SnPb.

I have changed the paste with fresh one, no positive results. I have
changed the reels with different date codes, Bingo! But even the "bad"
parts were quite fresh, less than one year old. One of them is pure Sn
plated, don't know about the other ones.

The question is: where on Earth can humidity stay in a ceramic resistor?
What else can be the cause of the blowholes? Did not bake the boards,
since changing the components worked, so I guess the PCBs are out of the
hook...

Thanks,

Ioan

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