Gary,
IPC-7351 - 3.4.8 Panelization - gives a general idea, but also states that
it really depends on the board handling and fixture equipment. Under panel
construction (3.4.8.1) it states, "the panel must be planned well".
I would say that more than just specifying IPC-7351 Figure 3-21 is needed
on a multi-board panel.
We have small details that we add to our drill files that show what we want
between board to board and one like figure 3.21 board to panel edge.
Ray Johnston
Lead CAD Designer
Rane Corporation
425-355-6000
rayj@rane,com
----- Original Message -----
From: "Gary M. Koven" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 23, 2006 8:35 AM
Subject: Re: [DC] Breakaway tab specification
> OK, I'll correct my own error first.
>
> I used the obsolete spec IPC-SM-782A Figure 3-31. I should have used
> IPC-7351 Figure 3-21.
>
> Regardless, is 7351 kosher for this? Or do I need a different reference?
>
> Thanks,
> Gary
>
> -----Original Message-----
> From: Gary M. Koven [mailto:[log in to unmask]]
> Sent: Wednesday, August 23, 2006 11:22 AM
> To: IPC Designers Council ([log in to unmask])
> Subject: Breakaway tab specification
>
> 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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