Brian,
I have also walked through these specs and their inconsistencies; it is
actually even worse.
Since it's minimum, you need to start with something thicker or you will
likely not comply.
Also, the terms minimum and nominal are crossed in the different specs,
and the method
to ascertain compliance is troublesome. Add to that, it applies to either
cores or prepregs.
Dewey,
I did write up a recommendation for reconciliation of the various specs
but nothing came
of it. I'm going to give it another shot.
Off line I will send you what I wrote.
Valerie
"Whittaker, Dewey (AZ75)" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
04/20/2006 11:26 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Whittaker, Dewey (AZ75)" <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Dielectric Thickness Requirements
I'll refrain from sarcasm and humor and say welcome to the club. For
the last two years I have been trying to rewrite IPC-4101, IPC-6012,
IPC-6011, IPC-A-600, and IPC-2221 for the same reasons. There are too
many undefined sets of criteria. It is not until you read them for
the ninth time and try to follow a process and requirements definition
protocol to completion that you realize all the dichotomies that exist.
The same probably exists for IPC-6013 and IPC-2222. You have correctly
concluded, that unless otherwise specified the minimum dielectric
spacing shall be .09 mm(.0035).
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Guidi
Sent: Thursday, April 20, 2006 7:59 AM
To: [log in to unmask]
Subject: [TN] Dielectric Thickness Requirements
I'm looking for some guidance with regards to dielectric thickness
requirements. We are currently fabricating boards for a customer in
which IPC-6013 is invoked on the drawing. Within IPC-6013A you will
find the following:
"3.7.15 Dielectric Thickness: The minimum dielectric spacing shall be
specified on the procurement documentation."
Well, that's pretty clear. However, it is not on the procurement
documentation, and it very rarely is. Since IPC-600 is invoked within
IPC-6013 as a sub-tier acceptability document, I figured I'd head down
that road. IPC-600G specifies the following:
"3.1.8 Acceptable - Class 1, 2, 3: The minimum dielectric thickness
meets the minimum requirements of the procurement documentation. If not
specified, must be 0.09 mm [0.0035 in] or greater."
Okay, so as a result of this statement one may interpret this as the
controlling requirement (0.0035" in this particular case). Unless of
course you head back to IPC-6013 which states the following in section
2: "2 Applicable Documents: The following specifications form a part
of this specification to the extent specified herein. If a conflict of
requirements exists between IPC-6013 and the listed applicable
documents, IPC-6013 shall take precedence.
So at this point, I'm right back to where I started. There is no defined
dielectric thickness specified on the procurement documentation.
Additionally, the cross sectional view on the drawing does not define
the number of ply's between layers. This is obviously desirable for the
manufacturer to ensure they/we have the freedom to develop the
construction based on a balance between the customers needs and the
manufacturing "sweet spot". However from a compliance stand point, I'm
in a quandary. If I had a multilayer construction with a single ply of
1080 prepreg between two 1/2 ounce layers (one signal, one ground),
would the resulting board comply to the spec? In looking for further
clarification, I deferred to IPC-6012B, IPC-2222 and IPC-2221A and
found the following:
IPC-6012B = .0035" minimum
IPC-2222 = .0035" minimum
IPC-2221A = Shall be specified on procurement documentation
I hope the use of direct quotes is acceptable here. It's the only way
for me to really characterize my problem. Has anyone out there come
across this issue? I've searched the archives, and similar issues have
not been discussed (as far as I can see) since 96'/97'.
Brian Guidi
R&D/Quality Systems Specialist
Teledyne Printed Circuit Technology
Tel: (603) 889-6191 X:310
Fax: (603) 886-2977
E-mail: [log in to unmask]
Visit us @ http://www.tetpct.com
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
