I'd worry as to why there is no heel fillet.
To me that is an indicator that some root cause exists which may have
unpleasant reliability consequences.
Only when you can prove that the root cause is benign can you proceed.

Zero toe fillet is relatively normal.


Rex

Rex Waygood
Technical Manager
 
Hansatech EMS provides value manufacturing through engineering and
quality
 
Hansatech EMS Limited
Benson Road
Nuffield Industrial Estate
Poole
Dorset
BH17 0RY
 
+44 (0)1202 338200


 

-----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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