Bill,
Our rigid boards are 2, 4 and 6 layer boards where Dk, Tg, and other arcana
are not important enough to warrant any material beyond IPC 4101/21 "normal"
FR-4. We allow the fabricator to choose the prepreg. The standard 2-layer
core is mostly 0.059 inch these days. We're fortunate we can be flexible,
so there's no reason to pay more for what you don't really need, right?
Valerie St. Cyr had a comment on this topic also which was interesting and I
will go reply to hers next.
Thanks,
Gary
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Brooks,Bill
Sent: Wednesday, March 09, 2005 12:04 PM
To: [log in to unmask]
Subject: Re: [DC] Finished thickness tolerance
Hi Gary,
You'd be surprised how often this sort of question pops up.
The 'standard' thickness for PCB's here in the US I believe was derived from
the single and double sided board days back in the 1960's era... Material
was offered clad with copper in various thicknesses and in 1/32 inch
increments. It is still the 'defacto' standard. That's why you see so many
people specifying .031 (.03125) .063 (.0625) .094 (.09375) .125 thickness
materials. In fact the industry has become so flexible now that we could
specify just about any thickness we need in .002 in. increments because
that's the standard thickness of the prepreg material used to build up the
final thickness of any multilayer board. I think they still sell the single
and double side clad materials though... If you check with your chosen board
manufacturer I'm sure they can tell you what materials they normally stock
and use and will give you a broad range of options for finished board
thickness... even if you are designing in metric. :)
Best regards,
Bill Brooks - KG6VVP
PCB Design Engineer , C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
e-mail:[log in to unmask]
http://www.dtwc.com
http://pcbwizards.com
-----Original Message-----
From: Gary M. Koven [mailto:[log in to unmask]]
Sent: Wednesday, March 09, 2005 8:05 AM
To: [log in to unmask]
Subject: [DC] Finished thickness tolerance
We design Class 2 boards and have been specifying on drawing finished
thickness 0.031 in +/- 0.004 in or 0.062 in +/- 0.008 in.
I'm looking for the finished thickness tolerance tables by class. I could
not find these details of what I need in IPC-2221, 2222, 6011, or 6012, just
vague general references. Are these in IPC-4101?
If anyone can verify or correct what we have been specifying and reference
whatever updated standard to use, I'd appreciate it.
TIA and Best Regards,
======================
Gary M. Koven
Engineering Services Manager
Dynazign, Inc.
806 Tyvola Road, Suite 100
Charlotte, NC 28217
P: 704.405.1234 x210
F: 704.405.1402
http://www.dynazign.com/
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