Ooops
Getting old.
Land pattern error.
:-)
Is that not then excluded from the class 3 requirement?
Can the customer agree to a concession?
If the customer is concerned about reliability then some form of
qualification test might be the only way to satisfy a hi-rel
requirement.

Rex 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: 24 August 2011 21:58
To: [log in to unmask]
Subject: [TN] Gull Wing Lead - no heel fillet

Hypothetical situation:

Gull wing lead, land pattern error, zero heel (also zero toe) fillet.
Hardware would not meet Class 3 workmanship requirements.

An equation is being used to decide if the pad to gull wing lead lap
solder joint is adequate to survive the intended thermal cycling
environment.

This would have been a question for Werner but I am sure there are
others here who can shed some light on this for me.

I know that part of the justification for why we have set our IPC
standards where they are is partly based on years of testing.

How could a mathematical calculation such as "Steinberg equation"
justify a lack of Class 3 gull wing lead heel fillet?

Any help is appreciated.





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