Hi Steve - just to chime in with the rest of the TechNet folks - I have
lead trimmed more "boards" than leads on a given day of operation with an
automated lead trim system. I don't have any "good" words of description
for the systems, am very glad to see them become "artificial reef material"
and am an advocate of your thoughts - prep the leads before soldering.
Enough said, I am off to swipe one of Doug's Mountain Dew's. Happy Holidays
to everyone.
Dave Hillman
Rockwell Collins
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"Stephen R. Gregory" <[log in to unmask]>@ipc.org> on 12/17/2001 11:12:22 PM
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Subject: [TN] Mass lead trimming systems...
Hi All!
The subject has come up here about mass lead trimming systems. From what
I've
learned, they have their place. But in our situation, I have the opinion
that
they aren't warranted here. We do a lot of class-3 electronics, have
hardware
(screws and whatnot from connectors) that hang below the lead length
requirements.
Many of the requirements on the asssembly drawings of products we build,
still call out MIL standards, even though they are obsolete, we are still
obligated to build to these standards...those that build product according
to
these standards, and have tried to deviate, or change, from what is
documented on these standards know what a task that is...it isn't going to
change.
So, in my opinion, mass lead trimming systems have no place here. There are
too many things that call out extra work that will need to be done because
of
these systems.
The J-STD's call out that if lead trimming is performed after wave solder,
then the joints should be either re-reflowed, or inspected under 10X to
ensure that there has been no fractures...
I've also heard that these systems need METICULOUS maintenance. If they
aren't maintained perfectly, they will cause major problems.
Just want to hear from any of you that have direct experience with these
systems..
My position is that you either prep PTH components so that lead length
requirements are met after soldering, and/or you make the adjustments that
are available on your auto-insertion machines so that you meet lead length
requirements...if you have to trim after wave solder, then either you
haven't
specified the proper component prep, or you need to adjust the cut and
clinch
on your auto-insertion equipment...I come the school that you can do things
before wave solder that keeps lead length requirements within
specifications,
and not require mass lead trimming afterwards.
So with that being said, what opinions are out there about mass lead
trimming
systems?
As always, all ya'll are the best...
-Steve Gregory-
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