Guy,
I'm no mech guy, but with the stiffer lead free solders wouldn't smaller
fillets be a good thing? The little you gain in longer time for a crack
to propagate through a large solder joint would be more than offset by a
longer time for it to form in the first place because the smaller joint
would be more compliant. I await either confirmation or a firey death
from more knowledgeable Technetters.
I seem to recall that a few years ago Ing was saying that Ericsson had
gone to chip cap joints where there was virtually no fillet showing up
the side of the chip face.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Thursday, May 22, 2008 7:49 AM
To: [log in to unmask]
Subject: Re: [TN] 0402 anti-tombstoning land pattern
If we make the land narrower than the part and minimize the length,
won't
that compromise both mechanical strength and solder joint life in a
thermal
cycling environment?
My experience with solder joint failure on chip components the joint
cracks
down the face and under the part. If the height of the fillet is reduced
the
time to failure will also reduce. No?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Wednesday, May 21, 2008 5:51 PM
To: [log in to unmask]
Subject: Re: [TN] 0402 anti-tombstoning land pattern
Hi Dean,
Make the land pattern narrower than the component-I know, I know, tough
to
do with 0402's as well as shorter thus producoing less of a fillet
[which is
,of course, the root cause for the tombstoning]
Werner
Future workshops:
Reliability Issues with Lead-Free Soldering Processes, June 17, London
Interconnect Failures and Design for Reliability for PCB PTHs, June 17,
London Pb-Free Soldering Processes-Survival, Quality, Reliability,
August
18, Orlando Reliability Issues with Lead-Free Soldering Processes,
September
22, Schaumburg Failure Mode and Root Cause Analyses Reliability
(Fatigue,
Brittle Fracture, ENIG), September 22, Schaumburg
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