Werner
Thanks for your feedback
Arturo
----- Original Message -----
From: "Werner Engelmaier" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 07, 2005 9:14 PM
Subject: [TN] Re: [TN] Led component Pull Test
> Hi Arturo,
> I have answered your question inthe past:
> There is no pull test specification. And there is a good reason none
exists.
> First, there cannot be such thing as a real 'lead pull test;' while you
are
> of course pulling on the lead, what you are doing to the solder joint is
> peeling it—the proper reference is a lead-peeling test.
> Second, the solder joint strength, as determined by a lead peeling test,
has
> no bearing on the reliability of the solder joint, provided the peeling
test
> does not reveal inadequate wetting or poor metallization, e.g., 'Black
Pad.'
> Third, in a peeling test you always need to observe the whole peel-load
> history for the whole peeling process; with a 1T or larger heel fillet,
the largest
> load will be at the initial portion of peeling through the heel fillet,
with l
> ower loads subsequently depending on whether or not (or to what extent)
side
> fillets are present.
> Fourth, the fracture surface of the peeled solder joints give typically
more
> information than do the peel-load histories, because the ONLY really
important
> finding is whether or not adequate wetting has taken place, i.e. the
> separation is mostly in the solder vs. being interfacial.
> Fifth, 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.
>
> Regards,
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL 32174 USA
> Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
> E-mail: [log in to unmask], Website: www.engelmaier.com
>
>
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