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Subject:	Re: Impedance Spec +/-5% and Cpk of 1.33
From:	Dennis Fritz <[log in to unmask]>
Reply To:	TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:	Tue, 14 Feb 2006 23:04:44 EST
Content-Type:	text/plain
Parts/Attachments:	text/plain (65 lines)

In a message dated 2/14/2006 2:18:23 PM Eastern Standard Time,  
[log in to unmask] writes:

Is the  industry capable of this requirement?

Impedance +/-5% with a  demonstrated Cpk of 1.33.

This could apply to Single Ended 50 ohms or  100 ohms Differential.
Also, this is on a Flex Circuit.


*************************************
I believe the IPC roadmap just published in late 2005 shows  the following 
capabilities on 5.0 mil (125 micron) circuit traces.  While  this is from rigid 
boards, perhaps it can be projected to flex.  A number  of controlled 
impedence configurations are shown, as noted.  Also, the RCG  means revenue center of 
gravity shops - the generally capable  construction.  The SOA is state of the 
art, meaning that perhaps the "best"  2-5% of the shops in the world can meet 
these criteria.   As I  understand it a Cpk of 1.33 would be four standard 
deviations.  Thus, the  average shop cannot meet your requirements with any 
controlled impedence  construction.  The best shops can possibly meet your 
requirements (in hard  boards) with surface microstrip, embedded microstrip, and 
stripline  construction.  
 
Hopefully, this will give you a place to start in discussing  your 
requirements, and the next IPC Roadmap should have a bit of data on flex  capability as 
I understand the PCQRR committee has now constructed test coupons  for this 
material. 
 
 
Table A6-9.  Controlled Impedance Formation (125m  Conductor)
ATTRIBUTE                      2002-2003                                  
2004-2005
RCG        SoA                            RCG               SoA
Surface Microstrip
Standard Deviation (Ω)      2.3           1.4                             2.1 
               1.0
Embedded  Microstrip
Standard Deviation (Ω)      1.4           0.8                             1.4 
                 0.7
Stripline
Standard Deviation (Ω)     1.4            0.9                             1.4 
                0.6
Edge-Coupled Stripline 
Standard Deviation (Ω)      2.7           1.7                             2.7 
               1.5
Broadside-Coupled Stripline  
Standard Deviation (Ω)     2.2            1.4                             2.2 
                 1.4


Denny Fritz
MacDermid
Section editor - Rigid board fabrication, IPC Roadmap. 

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