Always remember that your "approved" drawing takes precedence over the
specification! If you have the clearance in the next level of assembly and
you meet your drawing requirements (hint, hint) you should be OK.
Ron Dieselberg

-----Original Message-----
From: Miguel Vallejo [mailto:[log in to unmask]]
Sent: Wednesday, February 09, 2000 03:05
To: [log in to unmask]
Subject: [TN] Dimension variation


Hi,
I'm in the assembly end of the stick and have a situation that requires
insight from the IPC group and parts manufacturers, although everyone is
welcome to respond.
1. J-STD-001B, 1.3.1, states "Actual measurements of specific part
mounting and solder fillet dimensions and determination of percentages
are not required except for referee purposes."
2. If connector, sockets, headers, etc. are manufactured to present a
lead protrusion of .060 on a .062 PCB and .030 on a .092 PCB (I'm
assuming this is the manufacturer's target from what I've seen).
3. Considering a scenario where PCB and parts fabrication tolerances are
in opposite directions (ex. PCB on the min. side and part on the max.
side), which results in an increased lead protrusion, .062-.065.

Is one to interpret the J-STD statement as expecting such a variation to
be acceptable on a class 3 assy, since we're not required to measure for
these dimensions? I've concluded so, but others here think we are bound
to the .060 max.
However, how is one expected to follow recommendations on J-STD-001B,
1.3.1, and meet the .060 max. lead protrusion on this kind of scenario?
I hope I presented a clear idea of my situation.
Thank you for any help.

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