Bob,
As I replied in some previous mails, I ended up creating a separate panel
layout drawing.
In the response to the comments from Ted Tontis, I remarked that the
combination of hand soldered endcaps on both ends, as well as the 0.093
board thickness, might rule out a more conventional approach of tab all
ends, score all, etc.
Thanks for your input!
Gary
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Robert
Wolfe
Sent: Wednesday, August 23, 2006 1:09 PM
To: [log in to unmask]
Subject: Re: [DC] Breakaway tab specification
Gary,
You could specify this just as spec shows. However in this
case I too would agree to add any details required to your fab dwg.
Also just as the spec implies, it is a guideline, therefor your assembly
house should have some buy in as to how the board is paneled and
depaneled. If there are no extra items like notches, big holes, or areas
that you might not want a breakaway tab at least you & the assy house
should review the panel for this kind of stuff. If none of this applies
I feel at least add any details needed to decsribe breakaway, and in all
honesty even rough locations are good too, this way even if you
change vendors at least you will be getting close to the same board
where ever its built.
Bob Wofle
"Gary M. Koven" <[log in to unmask]> wrote:
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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