Victor,
You can also add small copper (overlapping) strips at one edge of the PCB in
the design. When the PCB gets routed, the copper is cut and can easily be
used
for a quick (edge) thickness calculation. They look something like this:
--------
-----------
--------------
------------------
---------------------
...etc.
If one is placed out of sequence it stands out like a sore thumb.
This also was something I learned from Lee Ritchey.
You also might want to get you hands on a copy of IPC-2141
which is on controlled impedance. Many OEMs will spec in 100%
TDR testing on the protos then allow AQL on the production (provided
the sample tested demonstrates it meets some CPk (agreed upon) value.
There's also sample tables/charts in IPC-6012.
Regarding Moonman's blueprint notes: Wow....must be military.
I haven't come accross those yet because I'm sure I'd rememer them!
David Hoover
Staff Application Engineer
Multek Technology, Inc.
www.multek.com
co-chair IPC-2141
----- Original Message -----
From: "Victor Hernandez" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, July 05, 2002 9:02 AM
Subject: Re: [TN] TDR test reports
> Earl,
>
> Can you please direct me to a WebSite that offers literature on how to
> calculate impedance. I have seen cards that have an impedance coupon.
> During the cross section I need to verify that the layup was conducted to
> print. Also how can I tell which layers are the impedance critical.
Tks.
>
> victor,
>
> -----Original Message-----
> From: Earl Moon [mailto:[log in to unmask]]
> Sent: Thursday, July 04, 2002 6:48 PM
> To: [log in to unmask]
> Subject: Re: [TN] TDR test reports
>
>
> Started designing and making impedance boards in 1983 for Magnuson
Computers
> in the Bay Area. Lee Ritchey was the man there.
>
> I required, then as now, specific MLB constructions with clearly specified
> materials, on the master drawing, as well as TDR testing as you do now
with
> traceability not only concerning the electrical part of the equation. Also
> required, then as now for all my one or two clients since then,
correlation
> and traceability of TDR to the materials and MLB construction shown in
> X-Section. This I do because it ties all the ends together and is very
> important for those not so knowlegeable, yet, about all that goes on in
the
> design and fab processes.
>
> MoonMan
>
> --------------------------------------------------------------------------
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