So THAT's why you had AABUS so liberally sprinkled into the SM-840D drafts.
You sneaky stinker you.
Doug Pauls
"Whittaker, Dewey
(EHCOE)"
<Dewey.Whittaker@ To
HONEYWELL.COM> [log in to unmask]
Sent by: TechNet cc
<[log in to unmask]>
Subject
Re: [TN] Build Structure
09/28/2006 02:48 Communication
PM
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]>
; Please respond
to
"Whittaker, Dewey
(EHCOE)"
<Dewey.Whittaker@
HONEYWELL.COM>
As long as you're espousing philosophical tips, dump the UOS; keep the
period; add new sentence stating "Deviations to this requirement shall
be AABUS( as agreed between user and supplier)". I get royalties for
this now that I got the IPC to legally recognize this in IPC-T-50.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Thursday, September 28, 2006 12:05 PM
To: [log in to unmask]
Subject: Re: [TN] Build Structure Communication
All Dimensions are finished UOS.
Plato
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice - 802.257.4571 ext 21
Fax - 802.257.0011
<http://www.vtcircuits.com/>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dan Skweres
Sent: Thursday, September 28, 2006 11:26 AM
To: [log in to unmask]
Subject: Re: [TN] Build Structure Communication
Frank,
So you're saying you specify starting copper weight and the finished
weight doesn't matter? I would think stating a minimum copper weight
would get you closer to what you want. If you were to specify H oz.
starting copper I agree you would have at least H oz. copper after
plating but as you stated various suppliers could in fact supply you
with different copper thicknesses depending on their processes. I
realize IPC does break it down (starting foil, class 1,2,3 plating
thickness etc.) but it doesn't guarantee anything. I guess the quote
was right... It all does depends.
Dan S
>>> [log in to unmask] 09/28/06 10:03AM >>>
Phillip,
To quote the great one "it depends"
What are you trying to achieve?
What is critical to your design?
How bad do you want to keep cost down?
Once you have answered these questions and probably a few dozen more you
can start to develop a plan to document PCB construction.
We do as follows with reasoning included:
1. Copper weight is always stated as starting. This allows us to ensure
we have a minimum copper weight for our current requirements and are not
reliant on various supplier plating processes. Also any additional
plating helps to derate our current calculations. And we can plan our
designs to use standard copper weights and minimize cost and lead
issues.
2. Dielectric thickness needs to be determined according to usage. For a
pure digital design a minimum dielectric thickness is enough but for
controlled impedance we specify a fixed dielectric and thickness.
Presently there are about 20 different standard stackups in my system
ranging from 2 to 10 layers.
We have designs that use .004 min dielectric layers with foil lamination
and designs that have set outer layer thickness that requires book build
processes, some are pure cheap FR-4 and others are RF Exotics, so we
need to have a large number of standard stackups. You may find you need
lots of standards or may get lucky and only have a couple.
Once you classify the design types you are producing you can then
develop the standard stackups you want your suppliers to use. Remember
to first talk to your suppliers and see if you can work concurrently to
find the best match and then to keep it as simple as possible to help
minimize your costs.
Hope it helps,
FNK
Frank N Kimmey CID+
Principal PCB Designer
PCB Programs
Powerwave Technologies Inc
Office 916-941-3159
Fax 916-941-3195
Mobile 916-670-0645
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Anslow, Phillip
Sent: Thursday, September 28, 2006 12:46 AM
To: [log in to unmask]
Subject: [TN] Build Structure Communication
Dear Fellow TechNetters,
Would you please share how you communicate your PCB build structures to
PCB fabricators, or, if you are a fabricator, how those which are
easiest to understand are presented to you.
For copper, is it best to quote (i) Nominal start weight or thickness,
(ii) minimum finished thickness to IPC-2221A tables before and/or after
plating if applicable?
For dielectric thickness, (i) specify value, (ii) give range (iii) leave
open?
Your advice and expertise is greatly appreciated.
Many thanks and regards,
Phil
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