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
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