Kenny,
Assuming your refering to IPC-A-610B with regards to class 3 this allows a
maximum lead protrusion of 1.5mm. I have seen mass lead trimming
successfully performed in a number of companies to this length. I have also
seen it poorly performed in one or two. I will offer the following:
Using a machine to trim the leads is the only way to go. As long as the
blades for the machine are kept sharp, a cutter is efficient and has a very
low probability of fracturing the solder joint. I suggest putting the
cutter blade on a sharpening schedule to prevent fracturing joints. The
cutters I have experienced get a bit dangerous to slightly warped PCB's
when you try cutting protrusions of less than .030".
I have seen two companies that actually have thier assemblers cutting all
leads by hand. In both cases it was very labor intensive and solder
fractures were far too common.
Depending on your component type and mix you might also consider using a
component prep process to cut the parts to length and add lock-in or
standoff forms where needed. This is the best alternative if you don't have
a large component mix. There are a few other considerations but this is
already becoming a novel.
So for what its worth, there's one opinion. Hope it helps.
Regards, Steve T.
----------
From: Kenny Bloomquist[SMTP:[log in to unmask]]
Sent: Monday, August 04, 1997 3:34 PM
To: [log in to unmask]
Subject: [TECHNET] Assy: Mass Lead Trimmers
What is the current climate toward mass lead trimming after wave solder?
I
am particularly interested in Class 3 applications. I am interested in
positives, negatives, standards requirements and equipment.
You may E-mail me direct or over the TechNet.
Thanks in advance for all responses.
KennyB
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