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July 2000

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Subject:
From:
Charlie Pitarys <[log in to unmask]>
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Date:
Tue, 18 Jul 2000 11:25:55 -0400
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Bounced this off a collegue who works in our TX office and here is the
outcome;
This
picture poses an interesting question.  I looked up the requirements in
ANSI-J-STD-001 B (I don't know if this is the latest, but it is the one I
have => the Draft of C didn't change either).  The photo shows good wetting
in all areas, with the exception of the area under the termination where the
adhesive contaminated the pad (just left of the arrow), but it appears to be
less than the 90 degree contact angle requirement.  It would have to be
better viewed under magnification to verify.  Poor wetting here could
potentially initiate microcracks in a high vibe condition.  In para 9.2.6.4
there does not appear to be a violation of the requirements to me, but I
have been out of the specification interpretation game for a while.

There are chip caps that only have metallization on the end of the
component.  In the case of this picture, there is a good solder fillet
between the pad and the end metallization.  This component will function
properly, and unless it is in a high vibration usage, I don't believe that
there will be any reliability issues.  I guess a question that may come out
from other responders is "what is the end use environment" for the
component.  If it is a TV set or something, this is acceptable.  If it is
for a missile application or a pace maker, it may work, but I think I would
still reject the joint.  This is just my opinion, of course.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Becerra Alejandro
Sent: Friday, July 14, 2000 5:51 PM
To: [log in to unmask]
Subject: [TN] Adhesive contamintation


Good afternoon Technetters,

I am sending a photo of one cross section of an 0603 component soldered in
the bottom side.
The photo shows how in the left terminal of the component there are not
solder between the metallization and the pad. The right terminal shows
solder between the metallization and the pad.
This effect is caused by adhesive contamination over the pad.
Unfortunately this condition is not clearly observed in the photo, but it is
observed in the microscope.
The fillet that is formed in the end side of the component is not affected.
Is this condition acceptable?

Thanks in advance for your help,

 <<0603soldera1.jpg>>



Alejandro Becerra
Phone (915) 841-8518, Fax (915) 841-8518
[log in to unmask]

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