**From:** Mike Degerstrom (*degerstrom.michael@mayo.edu*)

**Date:** Tue Nov 09 1999 - 09:12:20 PST

**Next message:**Mike Hughes: "[SI-LIST] : Plane Capacitance"**Previous message:**D. C. Sessions: "Re: [SI-LIST] : BusHolders: still necessary if SI mananged properly ?"

Jack,

I'm surprised that you could get capacitance and

inductance up to 6Ghz on a BGA. I will try to anwer your

question but I wouldn't think you can get results beyond

1 Ghz. At 1 Ghz, I would suspect that skin effect losses

are not your biggest worry when compared to L-C resonances.

However there have been postings many months ago which indicated

that skin-effect losses needed to be considered for leadframe packages

if I remember correctly. You may want to visit the archives

to review those postings.

You can fit a two-port network to a T-network or a pi-network

but the fit is valid only up to a certain frequency. The

technique to doing this is to covert measured S-parameters

to ABCD parameters then ABCD parameters to either T or pi-network.

The coversion formulas are given by a few good microwave textbooks

such as by Pozar. For example, let's say you did the fit to a pi-network

then the admittance of 'legs' to ground is your capacitance*jwf. The

reactance between the legs is your inductance*jwf. The real

part of your impedance between the legs of the pi-network

is your resistance vs frequency.

At some frequency your simple model does not work since your

physical structure is behaving like a distributed network. I will

plot magnitude and phases of the RLC values versus frequency

on log-frequency scale to help determine at what frequency

my results do not look correct.

Mike

On Nov 5, 11:38am, Jack wrote:

*> Subject: [SI-LIST] : resistance measurement
*

*> Hi All
*

*> I have some problem on package resistance measurement. Take BGA for
*

*> example,
*

*> I used to make
*

*> some "open" samples,and "short"samples to get the capacitance and
*

*> inductance
*

*> information
*

*> within a certain frequency range(bellow 6GHz). But for resistance, skin
*

*> effect let the resistance
*

*> increase nonlinear. How can I get the "resistance vs. frequency"
*

*> information from the VNA or TDR
*

*> measurement method?Does someone can help me to solve this
*

*> question?Thanks!
*

*>
*

*> Jack
*

*>
*

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*>
*

*>-- End of excerpt from Jack
*

-- _______________________________________________________________ Mike Degerstrom Email: degerstrom.michael@mayo.edu Mayo Clinic 200 1st Street SW Gugg. Bldg. RM 1042A Phone: (507) 284-3292 Rochester, MN 55905 FAX: (507) 284-9171 WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html _______________________________________________________________**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

**Next message:**Mike Hughes: "[SI-LIST] : Plane Capacitance"**Previous message:**D. C. Sessions: "Re: [SI-LIST] : BusHolders: still necessary if SI mananged properly ?"

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