Gentlemen,

I'm looking for confirmation and/or correction on breakaway tab
specification.

On my drill drawings, this is my first note for a blanket default:

"FABRICATE PER IPC-6012 CLASS 2 UNLESS OTHERWISE SPECIFIED"

However, 6012 is uselessly vague about breakaway tabs...referring the user
to the acceptability requirements of the assembly.

In the Depanelization/Singulation section, I don't call out a specific IPC
standard for breakaway tab acceptability.  The only statement I make is:

"BREAKAWAY TABS MUST SHEAR BELOW EDGE OF BOARD OUTLINE"

In the past, that has always been adequate.

However, I now have a board for which I've been tasked to pre-determine a
certain number of how many up.

On page 35 of IPC-SM-782A, Figure 3-31 "Breakaway (routed pattern)" shows
some better detail on their so-called Low-Stress (Mouse Bite) Breakaway.
The figure shows approximate center to center spacing of 75mm (3.0in)
between tabs and maximum indent of 0.4mm (0.016in).

Is it kosher to call out something like this:

"BREAKAWAY TABS TO BE LOW-STRESS MOUSE BITE PATTERN PER IPC-SM-782"

Or, is it not kosher because there exists a different standard in the
Acceptability series (like IPC-A-600, which I don't have here) which might
supersede a Design-series standard such as 782?

I've always in the past left arcana such as this to the assembly shop who
typically work with their chosen fabricator to pick a panel size, how many
up, tooling hole location, yada yada.  Now that I must own this step on this
one board, I will have to issue some sort of panelization drawing, and I
want to be careful not to put too much information on drawing which might
add to the cost of the boards.

TIA and Best Regards,

===========================
Gary M. Koven, C.I.D.
Dynazign, Inc.
Charlotte, NC, USA
Veteran of the Marsh School

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