In a message dated 3/2/99 7:32:06 AM Pacific Standard Time, [log in to unmask]
writes:
<< Good Morning from Minnesota,
We are currently building a product that requires us to trim the leads, after
soldering, to .020". When we trim, we are literally cutting most of
the solder fillet off. With the trim blade cutting into the solder first,
and not grabbing ont to the lead first, I think that is why we do not see
fractured solder. In your opinion, do you think that is a fair assumption?
(and I really hate to a-s-s-u-m-e). If so, do you think the solder
connections need to be 100% inspected under 10X magnification or reflowed, as
stated in the IPC 610B?
Thanks in advance for any input in this matter.
Connie Korth
K-Byte Manfacturing Hibbing>>
Hello there Connie!
I remembered a thread my good buddy Paul Klasek responded to last year
that was exactly the same problem you're having. Paul is pretty much on his
own down in Australia, so he has to be pretty creative when it comes to
solving the problems he faces. I guess what I'm saying is he knows of what he
speaks...check out the exchange below.
-Steve Gregory-
From: Paul Klasek <[log in to unmask]>
Subject: Re: Lead Trimming Question ?
Hi Chris ( & the rest of us on this issues )
On one of my previous projects I've got just that requirement = almost flush
base cut .
Tried all sorts of tungsten blades , super thin grinding disks on hyperspeeds
with vacuum take off ;
costly unsafe unrepeatable , you know it all .
What we finished up with was in-house build rig consisting of a high speed
diamond blade with >polished< top (Teflon coat if you feel extreme) gliding on
geared time feed ( or lever if you have a girl with feel, don't give it to
guy) below few chrome steel separating wires (.020 gauge in your case) on
which the pcb is resting (in a nest ; unless you designed tool holes for top
clamp fingers) . Both top touch clamp and bottom blade mounted with silicon
foam suspension to ensure positive but gentle action. If you design the top
clamp on grid you can change the fingers position according to your top
geography ; say if you have 8 slits running from a center to glide & lock
clamping fingers easy to a free spot on board .
The wires we >tensioned< with cam lock lever ( piano wires & mechanics may do
you ) Again, keep the cams sliding so you can adjust wires in between the
bottom topography on different boards . Check the status of separating wires
periodically , the constant polishing kills them eventually If you have them
on reels, just unlock the cams , pull fresh length in, lock again .
Let me know if get stuck .
See you
Paul Klasek
http://www.resmed.com
----------
From: Chris_Smith[SMTP:[log in to unmask]]
Sent: Friday, 17 July 1998 4:39
To: [log in to unmask]
Subject: [TN] Lead Trimming Question ?
All,
I have a lead trim operation that uses a Q-corporation LOM II trimming system
with a vacuum fixture. We are using the standard cutting rings with a 30
degree angle. The Vacuum fixture being used is quite snug and there is very
little vacuum loss in the process. The issue I have is the height requirement
we're trying to meet is .020" max length. This strict requirement is
resulting in pcbs being cut into and damaged, some flagging, and some solder
fractures. This seems to be a very operator dependent operation and costly if
not done correctly. I have tried varying the speed the cutter is moved across
the board, having Q-corp sharpen the blades instead of us doing it and using a
QB-1 PCB brusher which was purchased for this product. Is there anyone out
there with a similar trim height requirement and what types of things do you
perform to insure a repeatable process? Also anyone with suggestions please
let me, I need to get this resolved if at all possible.
Thanks
Chris Smith
Manufacturing Engineer
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