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December 2001

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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 5 Dec 2001 12:57:10 -0500
Content-Type:
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Jorge,
The first thing I would do is take problem devices and turn them upside
down (i.e., "dead-bug" position) and measure the plating thickness and
composition using XRF (i.e., X-Ray Fluorescence.  QFP soldering problems
with high tin content plating usually is an indication that the leads
weren't plated correctly.  If the plating on the leads isn't above 200
microinches you'll probably have soldering problems.

Regards,
George

George M. Wenger (908)-546-4531 [log in to unmask]
Celiant Corporation
40 Technology Drive
Warren, New Jersey 07059


-----Original Message-----
From: Jorge Rodriguez [mailto:[log in to unmask]]
Sent: Wednesday, December 05, 2001 12:14 PM
To: [log in to unmask]
Subject: [TN] QFP Leads with 85 Tin 15 Lead finish


        I already sent this e-mail on the past, got one answer, I hope
there
is somebody out there having the same issue.


        Fellow Technetters:

                I am sending this looking for any help, I guess I've
done
everything as far as the process and I haven't been able to resolve the
issue. We've been having soldering problems for a while with QFPs with
85
Sn/15 Pb finish on the leads. The solder doesn't flow properly and an
acceptable solder joint is not formed, the leads can be sometimes lifted
with no effort. The solder paste was checked after the screen printer
operation and it looked alright, the oven profile was also verified and
it's
always within the solder paste manufacturer's recommendations. This
problem
seems to be affecting all the different products with this type of
component. These part numbers are manufactured by Altera. Has anybody
experienced similar problems with QFPs from this manufacturer?, Does
anybody
have recommendations as far as the reflow oven profile?. I read
somewhere
that this particular alloy has the liquidus temperature at 205 degrees,
is
this accurate?

        Any help would be really appreciated

Jorge Rodriguez
Sr Process Engineer
Varian Electronics Manufacturing
615 South River Drive
E-mail: [log in to unmask]

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