[SI-LIST] Re: measurement methods of power supply networks for a wirebond BGA package
- From: "Hill, John" <jhill@xxxxxxxxxx>
- To: <hliang@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 28 Jun 2006 20:22:54 -0400
Liang
Here is how you can do it.
1. Build a board with four SMA connectors, 1, 2, 3, and 4 all on the
same side of the board. Put connector 2 below connector 1. Put connector
3 to the right of connector 2. Put connector 4 below connector 3.
Connect connectors 1 and 2 to one of the planes. Connect connectors 3
and 4 to the other plane.
2. Measure the full 2 port S matrix from connector 1 to connector 2.
Let's call that [S]12.=20
3. Measure [S]23 and [S]34.
4 Calculate the ABCD Matrix of [S]12. Let's call it [ABCD]12.
5. Calculate the [ABCD]23 and [ABCD]34.
6. Find a matrix [ABCD]prime12 such that [ABCD]prime12 times
[ABCD]prime12 is equal to [ABCD]12.
7. Find a matrix [ABCD]prime34 such that [ABCD]prime34 times
[ABCD]prime34 is equal to [ABCD]34.
8. Find a matrix [ABCD]ab such that [ABCD]prime12 times [ABCD]ab times
[ABCD]prime34 is equal to [ABCD]23.
9. The B value of the matrix [ABCD]ab is equal to the impedance of the
planes.
All four connectors should have good ground connections. However you
need to have a good all over ground at the surface of the board with the
SMA connectors. You must keep the fields radiating off the board away
from the Semi-ridge coax. Do not use flexible coax unless it is the
special coax made for VNA work. If the flexible cable cost less than
$500, you may not have the right cable. Check with you VNA vendor or
just use Semi-ridge coax.
Touch the SMA connectors before you capture the data. If the measurement
changes when you touch the connectors, you have not done enough to
terminate the fields. Keep at it until you can touch the connectors
without seeing a change in the measured values. If all else fails, use
ferrites on the semi-ridge coax. Please try your best to avoid using
ferrites.
What we are doing here is de-embedding the impedances of the two feed
points in the [S]23 measurement. We find the through impedance of the
two planes at the mid point of connectors 2 and 3 inside the board.
I would be grateful if one of the Agilent people could pass this by one
of the VNA programmers to make sure we have the math correct. In fact,
if there is an application note with the math used to do the
de-embedding, I would like to know about it.
The cost of this information is sharing your results.
Best regards,
John
=20
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Liang, Hongwei
Sent: Tuesday, May 30, 2006 6:35 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] measurement methods of power supply networks for a
wirebond BGA package
I am searching for methods on using network analyzer to measure power
supply networks for a wirebond BGA package from 50MHz to 500MHz. All the
wirebonds need to included as part of power supply network. =20
If any one knows a paper or resource, would you please tell me? I
appreciate for your help.
Thank you,
H.W.
=20
=20
=20
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