Werner, Technet people,
Would you have any quantitative data about the effect of side fillets
comparing to the heel fillet and the "bottom flat" wetting?
One of our customers asks us to have a solder fillet up to 50% of the
lead thickness on 3 sides of gullwing leads, with a fillet up to the
lead thickness (class 3 requirement) on the heel. I was not able to find
articles or papers showing the effect of side fillets on the solder
joint reliability.
I would really appreciate it if anyone could provide me with some
information
Thanks
Emmanuelle Crombez
> ----------
> From: Werner Engelmaier[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;[log in to unmask]
> Sent: Sunday, August 30, 1998 7:32 AM
> To: [log in to unmask]
> Subject: Re: [TN] SMT gull wing solder joint force test?
>
> Hi Mark,
> What you are proposing to do is not a good idea.
> First, there is no such thing as a standard 'solder joint
> force/shear/peel/pull test.' Because of the large variety of solder
> joint
> geometric variations, there can not be one from this consideration
> alone.
> Second, the solder joint strength, as determined by a lead shearing
> test, has
> no bearing on the reliability of the solder joint, provided the test
> does not
> reveal inadequate wetting.
> Third, the fracture surface of the forced solder joints give typically
> more
> information than do the shear-load histories, because the ONLY really
> important finding is whether or not adequate wetting has taken place.
> Fourth, the reliability in actual use does to a large extent depend on
> the
> heel fillet and the 'bottom flat' wetting; if the foot length is <3W,
> than
> also on the presence of a toe fillet, because short feet 'rock' during
> thermal
> cycling. Side fillets are less important, unless you have wetting
> problems.
> Fifth, make sure that your definition of a 'poor' solder joint
> corresponds
> with ANSI-J-STD-001.
>
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL 32174 USA
> Phone: 904-437-8747, Fax: 904-437-8737
> E-mail: [log in to unmask]
>
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