Mime-Version: |
1.0 |
Sender: |
|
X-To: |
|
Date: |
Sat, 6 Feb 1999 14:14:33 -0500 |
Reply-To: |
|
Subject: |
|
From: |
|
Content-Transfer-Encoding: |
7bit |
Organization: |
Applied CAD Knowledge Inc |
Content-Type: |
text/plain; charset=us-ascii |
Parts/Attachments: |
|
|
Scott Decker wrote:
>
> snip <
>
> First. 6 Layer Board.
> .5 oz on both outside layers and 1 oz on all inside signals and planes.
> .005" traces on all layers
> Dielectric thickness as follows:
> 6.5
> 10
> 18
> 10
> 6.5
> Er value of 4.2
> OK now you have the numbers, the impedance should be around 72 ohms.
> But Wait! The values I got were 77 72 72 72...... What Gives?
>
> Any Comments???
> I already herd that it's because the UV rays from the sun were hitting
> the top of the board more, but I don't think that's true....(:-}
>
Impedance is lighter than FR4 so more of it floats to the
top <g>.
Playing with these values on my tool I find that describing
the last trace layer as 1 oz instead of 1/2 would get you about
that difference. Can't get IPC's site right now, only the
archives are responding to me. Hope there's not a problem w/
the server...
--
Jeff Seeger Applied CAD Knowledge Inc
Chief Technical Officer Tyngsboro, MA 01879
jseeger "at" appliedcad "dot" com 978 649 9800
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
|
|
|