Before a recommendation can be considered would you provide information as to
whether you are using a coplanarity device check, what type of machine is
presenting the component, what thickness stencil you are using and what are
your profile settings on soak temp and time and time above liquidus.

Thanks,

Jim Keeton

-----Original Message-----
From:   Todd Ness [SMTP:[log in to unmask]]
Sent:   Monday, December 14, 1998 10:42 AM
To:     [log in to unmask]
Subject:        [TN] Fine-Pitch Soldering Problem

Technetters,

We are currently having soldering problems with a QFP 100 package
part. The part is a TI microprocessor component with a 0.0196" pitch.
The problem we are having with this part is we are getting
intermittent opens with corner leads. Other fine-pitch components on
this board solder fine. We have been building these boards for about 1
1/2  years in production with no problems until the last three months.
I found out that TI recently switched the lead plating for this part
from Tin/Lead to Nickel/Palladium. The solder paste we were using was
Kester OA 596. However, due to the inability of this paste to solder
to palladium parts, we switched to Kester OA 598. The profile was also
tweeked per Kester's recommendations for soldering to palladium leads.
All leads for this component and all other components on the board are
soldering fine with the new paste and new profile, except for some
intermittent opens on corner leads of the TI part with
Nickel/Palladium leads. Component leads for this part were inspected
prior to pick and place for coplanarity. Does anyone have any ideas of
what may be happening and any recommendations for eliminating this
problem.

Happy Holidays

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