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March 2006

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Subject:
From:
Jason Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jason Gregory <[log in to unmask]>
Date:
Mon, 6 Mar 2006 14:45:04 -0600
Content-Type:
text/plain
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text/plain (116 lines)
True Ramon,

But sometimes the pad layout is spec'd for a regular SOT14 or 16, and the
only available part (due to obsolescence or whatever) is a narrow body
component. Dealt with that a million times before.


Jason Gregory
Manufacturing Engineer
Innova Electronics
(281)653-5593
(281)653-5594 fax
(281)594-0602 cell
[log in to unmask]

-----Original Message-----
From: Dehoyos, Ramon [mailto:[log in to unmask]]
Sent: Monday, March 06, 2006 2:35 PM
To: TechNet E-Mail Forum; Jason Gregory
Subject: RE: [TN] Heel Overhang







        Usually the components have leads that are quite larger than
necessary. At part prep, someone decides what die to use to form the parts.
It seems that the die use was not the proper one. The right prep is when the
center of the feet are in the middle of the pad's length, at both ends of
the component.
        Ramon




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jason Gregory
Sent: Monday, March 06, 2006 2:03 PM
To: [log in to unmask]
Subject: Re: [TN] Heel Overhang

Kevin,

In IPC-A-610 Rev. D, it states clearly, for Class 3, "Minimum heel fillet
height is equal to solder thickness plus lead thickness."

If you have parts where the pad layout spread is larger than your component,
then the larger the difference will get you further away from the acceptable
spec.


Jason Gregory
Manufacturing Engineer
Innova Electronics
(281)653-5593
(281)653-5594 fax
(281)594-0602 cell
[log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Monday, March 06, 2006 10:29 AM
To: [log in to unmask]
Subject: [TN] Heel Overhang

Hello again.

Question on IPC-610 (class 3) criteria.  For SMT solder joints, there appear
to be criteria set for TOE overhang, but not HEEL overhang.  Is this an
oversite or a purposeful omission?  Is there a limit on how much the heel of
an "L" shaped SMT lead can be off the pad lengthwise?  The obvious and
defined limit is "does not violate minimum electrical clearance", but does
anyone else have info on this criteria?

Thanks again,
Kevin Glidden


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