Hey Steve,
I come from your class....including first hand experience to say nothing of
general practice.
You basically are on the right track. The mass lead cutting is a bear to
manage and maintain to say nothing of the inspection and rework post
process due to pressure being brought to bear on the connections themselves.
Do the prep work, the settings on the AI equipment and whatever else you
can to make things come out of the wave the correct way and you will be all
the happier with the results. All this without saying that touch up post
wave solder is work that can cause more harm than good.
Stay on the track you are on and stay in class, your a good student, you
learn well!
Richard
At 12:12 AM 12/18/01 -0500, you wrote:
>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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