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May 1999

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Subject:
From:
Paul Klasek <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 19 May 1999 09:35:55 +1000
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Yep, still here , buried under "projects" like seems everybody else ' Bev's
not biting ; Dave ; etc. this run up y2k is hectic .
Got a fright when Hugo tried to deregister me ; but , still here :

Fikreta, (it does help not to have a name like Steve or Paul ; the ID is
clear);
apart from what you find in archives on this subject one thing I did not see
that much emphasised ; remembering from old telecom days :

Exposed copper is not the best thing to have on solder side (forbidden on
some jobs); and milling/grinding/cutting/ this close does jolt the lead as
well ; solder being not weld ;
I've seen leads very much peeled from surrounding fillets after shave or cut
;
and no , it was not a dry joint issue .
Therefore my solution would be :
Bend the rules of prescribed leg protrusion = inspect from top (you're still
better off with filled barrel than smd joint); prep the leads to less than
board thickness and wave ; with bit of luck you should not have anything
ever .
If you get some icicles ; make a slide over vacuumed and earthed (copper
tail) linisher gliding on foam and plate ; it will look good too as all the
joints will have uniform dressing .
The slide can be as simple as steel trims clipped on side of board to
maintain the specified height . Needless to say keep ESD in considerations
on every step .
Filter on that vacuum would be nice .

See you folks ; good to know yo' out there .
How's the StarWars ; any decent models to glue up ; or is it all McLUCAS
merchandise ?

Paul Klasek
http://www.resmed.com



-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Wednesday, 19 May 1999 4:06
To: [log in to unmask]
Subject: Re: [TN] leads trimming


In a message dated 5/18/99 10:26:20 AM Pacific Daylight Time,
[log in to unmask] writes:

<< Hello there,
 I have requirements to trim leads down to 0.035". Have anybody try to prep
that short before wave. Board size is 4"x6" . I would like to know if any
experience with machines that trim leads.


 Fikreta Jusufagic
 Mfg. Engineer
 Sanmina Co, San Jose
 Voice: (408) 954-5594
 Fax: (408) 954-5277 >>

Hi Fikreta!

You sure that's TRIMMING leads? Sounds more like SHAVING them to me! (GRIN)
That is some short puppies...

I've had to do some boards like that before, only because of the poorly
designed case that the board had to go in, if you didn't trim them that
short
things could short out on the case. But I did it after wave...there was a
lot
of radial components on the board that also had to stand-off the board, and
if I trimmed them before wave they would fall over.

As far as equipment, a good person to send a email to asking about that
stuff
is Paul Klasek ([log in to unmask]) if he doesn't read this email
already...he's on the TechNet too. (HEY PAUL! Ya' there?) I remember him
helping somebody out a while back using one of those teflon-coated, spinning
blade deals...the name Q-Tron seems to stick in my mind for some reason?

As far as I'm concerned, the only reason you should need to trim leads that
short is because somebody wasn't thinking when they designed whatever
product
you're building. They shoulda left room for at least 60 to 100 thou..
Trimming leads that short there's always the chance of fracturing the
joints..

But hey, I know how it is, you get whatever the customer gives you...you
being at Sanmina, a contract assembly company like me, you do the same thing
I hafta do too...

-Steve Gregory-

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