It is doable IF it is co-designed with the fabricator understanding the
usual and
expected material deviations and etch factors; also, a tight tolerance on
a wide
line is more achievable than a tight tolerance on a narrow line because
the
absolute value of the tolerance is larger and etching tolerance is
dependent
not on line width but on copper foil depth. Copper thickness, dielectric
thickness
and consistency, line nominal width, etc all need to be dialed-in to
target spec
for a 50 ohm (or 100 Diff) nominal. (I hope I ma clear on this item, it is
the most
important).
As Deac also notes, there needs to be correlation established between the
fabricator's test equipment and methods, and the customer's. ..
Then the 1.33 Cpk is also possible and what would fall out of that would
be
processing outside of normal process windows, for instance, someone sets
the etcher on the wrong speed for the copper foil thickness ... (operator
errors being the biggest outside the process factor).
My 42 cents'; worth.
Valerie
Deac Descoteaux <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
02/14/2006 02:58 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Deac Descoteaux <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Impedance Spec +/-5% and Cpk of 1.33
I it difficult but doable. It would be interesting to see how the customer
measures the impedance as well?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Tuesday, February 14, 2006 2:28 PM
To: [log in to unmask]
Subject: Re: [TN] Impedance Spec +/-5% and Cpk of 1.33
This depends on the materials, dielectric and line dimensions which
contribute the standard deviation. Generally +/-5% is difficult to
achieve,
although we have a few designs that are capable @ a 5% tolerance.
Jeffrey Bush
Director, Quality Assurance and Technical Support VERMONT CIRCUITS
INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice - 802.257.4571 ext 37
Fax - 802.257.0011
<http://www.vtcircuits.com/>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glenn Pelkey
Sent: Tuesday, February 14, 2006 2:06 PM
To: [log in to unmask]
Subject: [TN] Impedance Spec +/-5% and Cpk of 1.33
Hi folks,
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.
Thanks,
Glenn
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